Proton-density fat fraction and simultaneous R2* estimation as an MRI tool for assessment of osteoporosis

Age-related T1 mapping, fat fraction, diffusion and perfusion parameters of the lumbar vertebrae in healthy children under 3.0 T MRI

AIM

Compare the T1 mapping, fat fraction, diffusion and perfusion parameters of the lumbar vertebrae of different age groups to establish normal values for healthy children and observe the trends in these parameters with age.

MATERIALS AND METHODS

A total of 146 healthy children (0-14 years) were included in this prospective study and underwent 3.0 T lumbar MRI examination. The study cohort was divided into five age groups (Group A ∼ E) according to development milestones in children. T1 mapping, Dixon and IVIM (intravoxel incoherent motion)sequence images were used to measure the parameters of lumbar vertebrae 2-4.

RESULTS

The normal values of each parameter were measured and compared across different age groups. The T1 value was negatively correlated with age (r=-0.619, p<0.001). The fat fraction (FF%) was positively correlated with age (r=0.635, p<0.001). There was a negative correlation between the D value and age (r=-0.406, p<0.001). The D∗ value was positively correlated with age (r=0.54, p<0.001). The f value was positively correlated with age (r=0.775, p<0.001). The inflexion points of the T1 value and FF% curves were at approximately 3 years old (36 months).The inflexion points of the IVIM-related parameter curves were approximately 5 years old (60 months).

CONCLUSION

The age-dependent differences in the vertebral body parameters of this pediatric cohort suggest changes in the bone marrow composition and cellular structure of the vertebral body during physiological growth in children. The establishment of normal values of children's lumbar spine can facilitate the clinical study of diseases.

Association of proton-density fat fraction with osteoporosis: a systematic review and meta-analysis

This study aimed to evaluate the correlation between measuring proton-density fat fraction (PDFF) in bone marrow using multi-echo chemical shift-encoded MRI and osteoporosis, assessing its effectiveness as a biomarker for osteoporosis. A systematic review was conducted by two independent researchers using Cochrane, PubMed, EMBASE, and Web of Science databases up to December 2023. Quality assessments were evaluated using the Cochrane risk of bias tool and the Agency for Healthcare Research and Quality (AHRQ) checklist. Fourteen studies involving 1495 patients were analyzed. The meta-analysis revealed a significant difference in PDFF values between the osteoporosis/osteopenia group and the normal control group, with a mean difference of 11.04 (95% CI: 9.17 to 12.92, Z=11.52, P < 0.00001). Measuring PDFF via MRI shows potential as an osteoporosis biomarker and may serve as a risk factor for osteoporosis. This insight opens new avenues for future diagnostic and therapeutic strategies, potentially improving osteoporosis management and patient care.

OBJECTIVE

This study aims to assess the correlation between measuring proton-density fat fraction (PDFF) in bone marrow using multi-echo chemical shift-encoded MRI and osteoporosis, evaluating its effectiveness as a biomarker for osteoporosis.

MATERIALS AND METHODS

This systematic review was carried out by two independent researchers using Cochrane, PubMed, EMBASE, and Web of Science databases up to December 2023. Quality assessments were evaluated using the Cochrane risk of bias tool and the Agency for Healthcare Research and Quality (AHRQ) checklist.

RESULTS

Fourteen studies involving 1495 patients were analyzed. The meta-analysis revealed a significant difference in PDFF values between the osteoporosis/osteopenia group and the normal control group, with a (MD = 11.04, 95% CI: 9.17 to 12.92, Z = 11.52, P < 0.00001). Subgroup analyses indicated that diagnostic methods, gender, and echo length did not significantly impact the PDFF-osteoporosis association.

CONCLUSION

PDFF measurement via MRI shows potential as an osteoporosis biomarker and may serve as a risk factor for osteoporosis. This insight opens new avenues for future diagnostic and therapeutic strategies, potentially improving osteoporosis management and patient care.

Assessment of Calcaneal Spongy Bone Magnetic Resonance Characteristics in Women: A Comparison between Measures Obtained at 0.3 T, 1.5 T, and 3.0 T

BACKGROUND

There is a growing interest in bone tissue MRI and an even greater interest in using low-cost MR scanners. However, the characteristics of bone MRI remain to be fully defined, especially at low field strength. This study aimed to characterize the signal-to-noise ratio (SNR), T2, and T2* in spongy bone at 0.3 T, 1.5 T, and 3.0 T. Furthermore, relaxation times were characterized as a function of bone-marrow lipid/water ratio content and trabecular bone density.

METHODS

Thirty-two women in total underwent an MR-imaging investigation of the calcaneus at 0.3 T, 1.5 T, and 3.0 T. MR-spectroscopy was performed at 3.0 T to assess the fat/water ratio. SNR, T2, and T2* were quantified in distinct calcaneal regions (ST, TC, and CC). ANOVA and Pearson correlation statistics were used.

RESULTS

SNR increase depends on the magnetic field strength, acquisition sequence, and calcaneal location. T2* was different at 3.0 T and 1.5 T in ST, TC, and CC. Relaxation times decrease as much as the magnetic field strength increases. The significant linear correlation between relaxation times and fat/water found in healthy young is lost in osteoporotic subjects.

CONCLUSION

The results have implications for the possible use of relaxation vs. lipid/water marrow content for bone quality assessment and the development of quantitative MRI diagnostics at low field strength.

Chemical shift-encoded MRI with compressed sensing combined with parallel imaging for proton density fat fraction measurement of the lumbar vertebral bone marrow

We aimed to investigate the accuracy of proton density fat fraction (PDFF) measurement of the lumbar vertebral bone marrow using chemical shift-encoded magnetic resonance imaging (CSE-MRI) with compressed sensing combined with parallel imaging (CSPI). This study recruited a commercially available phantom, and 43 patients. Fully sampled data without CSPI and under-sampled data with CSPI acceleration factors of 2.4, 3.6, and 4.8 were acquired using a 1.5T imaging system. The relationships between PDFF measurements obtained with the no-CSPI acquisition and those obtained with each CSPI acquisition were assessed using Pearson correlation coefficient (r), linear regression analyses, and Bland-Altman analysis. The intra- and inter-observer variabilities of the PDFF measurements were evaluated using the intraclass correlation coefficient. PDFF measurements obtained with all acquisitions showed a significant correlation and strong agreement with the reference PDFF measurement of the phantom. PDFF measurements obtained using CSE-MRI with and without CSPI were positively correlated (all acquisitions: r = 0.99; P < .001). The mean bias was -0.31% to -0.17% with 95% limits of agreement within ±2.02%. The intra- and inter-observer agreements were excellent (intraclass correlation coefficient: 0.988 and 0.981, respectively). A strong agreement and positive correlation were observed between the PDFF measurements obtained using CSE-MRI with and without CSPI. PDFF measurement of the lumbar vertebral bone marrow using CSE-MRI with CSPI can be acquired with a maximum reduction of approximately 75% in the acquisition time compared with a fully sampled acquisition.

Longitudinal MR-based proton-density fat fraction (PDFF) and T2* for the assessment of associations between bone marrow changes and myelotoxic chemotherapy

OBJECTIVES

MR imaging-based proton density fat fraction (PDFF) and T2* imaging has shown to be useful for the evaluation of degenerative changes in the spine. Therefore, the aim of this study was to investigate the influence of myelotoxic chemotherapy on the PDFF and T2* of the thoracolumbar spine in comparison to changes in bone mineral density (BMD).

METHODS

In this study, 19 patients were included who had received myelotoxic chemotherapy (MC) and had received a MR imaging scan of the thoracolumbar vertebrates before and after the MC. Every patient was matched for age, sex, and time between the MRI scans to two controls without MC. All patients underwent 3-T MR imaging including the thoracolumbar spine comprising chemical shift encoding-based water-fat imaging to extract PDFF and T2* maps. Moreover, trabecular BMD values were determined before and after chemotherapy. Longitudinal changes in PDFF and T2* were evaluated and compared to changes in BMD.

RESULTS

Absolute mean differences of PDFF values between scans before and after MC were at 8.7% (p = 0.01) and at -0.5% (p = 0.57) in the control group, resulting in significantly higher changes in PDFF in patients with MC (p = 0.008). BMD and T2* values neither showed significant changes in patients with nor in those without myelotoxic chemotherapy (p = 0.15 and p = 0.47). There was an inverse, yet non-significant correlation between changes in PDFF and BMD found in patients with myelotoxic chemotherapy (r = -0.41, p = 0.12).

CONCLUSION

Therefore, PDFF could be a useful non-invasive biomarker in order to detect changes in the bone marrow in patients receiving myelotoxic therapy.

CLINICAL RELEVANCE STATEMENT

Using PDFF as a non-invasive biomarker for early bone marrow changes in oncologic patients undergoing myelotoxic treatment may help enable more targeted countermeasures at commencing states of bone marrow degradation and reduce risks of possible fragility fractures.

KEY POINTS

Quantifying changes in bone marrow fat fraction, as well as T2* caused by myelotoxic pharmaceuticals using proton density fat fraction, is feasible. Proton density fat fraction could potentially be established as a non-invasive biomarker for early bone marrow changes in oncologic patients undergoing myelotoxic treatment.

Physiological gradient in lumbar spine fat fraction and R2* and its impact on osteoporosis diagnosis

BACKGROUND

Bone marrow adiposity and R2* have been explored as an imaging biomarker for osteoporosis. Chemical shift-encoded MRI (CSE-MRI) is a method that allows for relatively accurate measurement of adiposity and R2* in bone marrow in a simple manner. Additionally, there are reports of a physiological gradient of fat distribution in the lumbar spine. This physiological gradient of fat distribution can potentially impact the prediction of osteoporosis. Furthermore, the distribution of R2* is not well understood.

PURPOSE

This study examined how lumbar spine fat fraction (FF) and R2* change with different levels of the lumbar spine, how they influence osteoporosis prediction, and how they change according to measurement methods.

STUDY DESIGN/SETTING

Cross-sectional study using retrospectively collected data.

PATIENT SAMPLE

The study included patients who underwent dual-energy X-ray absorptiometry and lumbar spine CSE-MRI within one-month intervals between 2017 and 2022.

OUTCOME MEASURES

Reproducibility of FF and R2* based on measurement techniques, changes in FF and R2* according to vertebral level and osteoporosis status, and diagnostic power of osteoporosis based on vertebral level.

METHODS

Patients were categorized into the normal bone density, osteopenia, and osteoporosis groups based on bone mineral density. The relationship between groups and spine level before and after BMD adjustment was investigated using generalized estimating equations. Comparisons between the three groups and various measures of reliability were conducted using intraclass correlation coefficient. The diagnostic performance for predicting osteoporosis was evaluated with a receiver operating characteristic curve.

RESULTS

Comparing the three groups, FF increased with osteoporosis severity, while R2* decreased (p<.001). The intra/inter-rater agreement for FF and R2* was excellent. A physiological gradient within individuals was observed, where FF increased towards the lower lumbar spine (p=.002). R2* tended to decrease, but it was not statistically significant (p=.218). There was no statistically significant difference in the diagnosis of osteoporosis based on FF or R2* across different lumbar spine levels.

CONCLUSIONS

There was an increase in FF and a decrease in R2* from T12 to L5. However, the predictive power of osteoporosis did not significantly differ between each level.

Associations of gestational diabetes and proton density fat fraction of vertebral bone marrow and paraspinal musculature in premenopausal women

Background and objective

Fat content in bones and muscles, quantified by magnetic resonance imaging (MRI) as a proton density fat fraction (PDFF) value, is an emerging non-invasive biomarker. PDFF has been proposed to indicate bone and metabolic health among postmenopausal women. Premenopausal women with a history of gestational diabetes (GDM) carry an increased risk of developing type 2 diabetes and an increased risk of fractures. However, no studies have investigated the associations between a history of GDM and PDFF of bone or of paraspinal musculature (PSM), composed of autochthonous muscle (AM) and psoas muscle, which are responsible for moving and stabilizing the spine. This study aims to investigate whether PDFF of vertebral bone marrow and of PSM are associated with a history of GDM in premenopausal women.

Methods

A total of 37 women (mean age 36.3 ± 3.8 years) who were 6 to 15 months postpartum with (n=19) and without (n=18) a history of GDM underwent whole-body 3T MRI, including a chemical shift encoding-based water-fat separation. The PDFF maps were calculated for the vertebral bodies and PSM. The cross-sectional area (CSA) of PSM was obtained. Associations between a history of GDM and PDFF were assessed using multivariable linear and logistic regression models.

Results

The PDFF of the vertebral bodies was significantly higher in women with a history of GDM (GDM group) than in women without (thoracic: median 41.55 (interquartile range 32.21-49.48)% vs. 31.75 (30.03-34.97)%; p=0.02, lumbar: 47.84 (39.19-57.58)% vs. 36.93 (33.36-41.31)%; p=0.02). The results remained significant after adjustment for age and body mass index (BMI) (p=0.01-0.02). The receiver operating characteristic curves showed optimal thoracic and lumbar vertebral PDFF cutoffs at 38.10% and 44.18%, respectively, to differentiate GDM (AUC 0.72 and 0.73, respectively, sensitivity 0.58, specificity 0.89). The PDFF of the AM was significantly higher in the GDM group (12.99 (12.18-15.90)% vs. 10.83 (9.39-14.71)%; p=0.04) without adjustments, while the CSA was similar between the groups (p=0.34).

Conclusion

A history of GDM is significantly associated with a higher PDFF of the vertebral bone marrow, independent of age and BMI. This statistical association between GDM and increased PDFF highlights vertebral bone marrow PDFF as a potential biomarker for the assessment of bone health in premenopausal women at risk of diabetes.

Chemical Shift-Encoded MRI of the Lumbar Vertebral Bone Marrow for Detecting Osteoporosis With Low Trabecular Bone Quality in Patients With Breast Cancer Receiving Aromatase Inhibitors

BACKGROUND

Osteoporosis with low trabecular bone quality (OLB) in patients with breast cancer receiving aromatase inhibitor (AI) therapy is associated with an increased risk of vertebral fractures. The capability of chemical shift-encoded MRI (CSE-MRI) in detecting OLB needs to be investigated.

PURPOSE

To assess the diagnostic performance of proton density fat fraction (PDFF) and R2* measurements from CSE-MRI for detecting OLB in postmenopausal women with breast cancer undergoing AI therapy.

STUDY TYPE

Prospective.

POPULATION

126 postmenopausal females (mean age: 69.5 ± 8.8 years) receiving AIs (average period: 41.6 ± 26.5 months) after breast cancer surgery.

FIELD STRENGTH/SEQUENCE

1.5-T, three-dimensional CSE-MRI (six echoes), T1-weighted Dixon, short tau inversion recovery, and diffusion-weighted images.

ASSESSMENT

Both CSE-MRI and dual-energy x-ray absorptiometry were performed on the same day. Measurements included averaged PDFF, R2*, bone mineral density (BMD), and trabecular bone score (TBS) from L1 to L4 vertebrae. A T-score ≤ -2.5 from BMD measurements indicated osteoporosis, whereas T-scores of ≤ - 2.5 plus TBS ≤-3.7 indicated OLB. The diagnostic performance of PDFF, R2*, and the combination of PDFF and R2* for identifying osteoporosis or OLB was assessed.

STATISTICAL TESTS

Student's t-test; Mann-Whitney U test; χ2 or Fisher exact tests; Pearson correlation; multivariate analysis; Receiver operating characteristic (ROC) analysis with the area under the curve (AUC); logistic regression model; intraclass correlation coefficient. A P-value <0.05 was considered statistically significant.

RESULTS

For detecting osteoporosis, AUC values were 0.59 (PDFF), 0.66 (R2*), and 0.65 (combined PDFF and R2*). Significant mean differences were noted between patients with and without OLB for PDFF (66.11 ± 5.36 vs. 57.49 ± 6.43) and R2* (46.62 ± 9.24 vs. 63.36 ± 12.44). AUC values for detecting OLB were 0.75 (PDFF), 0.82 (R2*), and 0.84 (combined PDFF and R2*).

DATA CONCLUSION

R2* may perform better than PDFF for identifying OLB in patients with breast cancer receiving AIs.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 4.

The quantitative parameters derived from IDEAL-IQ in the lumbar vertebrae of healthy children: a pilot study of bone development

Background

Early childhood bone development affects that of bone disease in adolescence and adulthood. Many diseases can affect the cancellous bone or bone marrow. Therefore, it is of great significance to quantify the bone development of healthy children. The evaluation methods of bone development include bone age (BA) assessment and dual-energy X-ray bone mineral densitometry (DXA), both of which have strong subjectivity. The present study was conducted to improve our understanding of the bone development of healthy children using the quantitative parameters derived from iterative decomposition of water and fat with echo asymmetry and least squares estimation quantification (IDEAL-IQ) sequence.

Methods

Our study enrolled healthy children between January 2022 to December 2022 consecutively in Children's Hospital of Shanxi. The inclusion criteria were as follows: (I) age ≤18 years; (II) no contraindications (surgical and interventional devices for ferromagnetic materials, cardiac implantable electronic devices, cochlear implants, insulin pumps, dental implants containing metal or alloy) to magnetic resonance imaging (MRI) scan. The exclusion criteria were as follows: (I) previous malignant disease, (II) previous chemoradiotherapy, (III) previous spine surgery, (IV) previous or acute vertebral compression fracture, (V) artifacts present in images. Participants underwent MRI scans using IDEAL-IQ sequence in the lumbar vertebrae. The IDEAL-IQ parameters [proton density fat fraction (PDFF), 1/T2* (R2*)] were obtained. The factor analysis of variance was applied to compare the differences of PDFF and R2* in different lumbar vertebral groups. The Kruskal-Wallis H test or Mann-Whitney U test was applied to compare the differences of quantitative data among different gender or age groups. Spearman correlation analysis was applied to study the relationship among the age, PDFF, and R2*.

Results

A total of 145 participants (76 males, 69 females) were evaluated. There were no significant differences in PDFF and R2* of different lumbar vertebrae (PPDFF=0.338, PR2*=0.868). The average age was 36 [13-72] months. They were assigned into 4 groups (0-11, 12-35, 36-71, and 72-144 months). As the age increased, the average PDFF and R2* both increased significantly (rPDFF=0.659, rR2*=0.359, P<0.001). There were significant statistical differences in PDFF and R2* between the 4 age groups (ZPDFF=46.651, ZR2*=27.537, P<0.001). Moreover, the PDFF was also positively correlated with R2* (r=0.576, P<0.001). No association was found between the gender and PDFF, R2* (PPDFF=0.949, PR2*=0.177).

Conclusions

The quantitative parameters derived from IDEAL-IQ in the lumbar vertebrae of healthy children will improve our understanding of bone development and provide a basis for further exploring the diseases that affect children's bone development.

Relative fat fraction of malignant bone lesions from breast cancer, prostate cancer and myeloma are significantly lower than normal bone marrow and shows excellent interobserver agreement

OBJECTIVES

To compare relative fat fraction (rFF) of active bone lesions from breast, prostate and myeloma malignancies and normal bone marrow; to assess its inter-reader agreement.

METHODS

Patients with breast (n = 26), myeloma (n = 32) and prostate cancer (n = 52) were retrospectively evaluated. 110 baseline rFF maps from whole-body MRI were reviewed by two radiologists. Regions of interest for up to four focal active lesions in each patient were drawn on rFF maps, one each at the cervicothoracic spine, lumbosacral spine, pelvis and extremity. The mean and standard deviation of rFF were recorded. The rFF of normal marrow was measured in the pelvis for patients without diffuse bone disease (n = 88). We compared the rFF of malignant bone lesions and normal marrow using Mann-Whitney test. Interobserver agreement was assessed by interclass correlation coefficient.

RESULTS

Malignant bone lesions showed significantly lower median rFF (13.87%) compared with normal marrow (89.76%) with little overlap (p < 0.0001). There was no significant difference in the median rFF of malignant lesions from breast (14.46%), myeloma (13.12%) and prostate cancer (13.67%) (p > 0.017, Bonferroni correction) and in the median rFF of bone disease according to their anatomical locations (p > 0.008, Bonferroni correction). There was excellent interobserver agreement (0.95).

CONCLUSION

The low rFF of active bone lesions in breast, prostate and myeloma malignancies provides high image contrast relative to normal marrow that may be used to detect bone metastases.

ADVANCES IN KNOWLEDGE

This study shows the importance of rFF towards detecting bone metastases.

Radiomics Texture Analysis of Bone Marrow Alterations in MRI Knee Examinations

Accurate diagnosis and timely intervention are key to addressing common knee conditions effectively. In this work, we aim to identify textural changes in knee lesions based on bone marrow edema (BME), injury (INJ), and osteoarthritis (OST). One hundred and twenty-one MRI knee examinations were selected. Cases were divided into three groups based on radiological findings: forty-one in the BME, thirty-seven in the INJ, and forty-three in the OST groups. From each ROI, eighty-one radiomic descriptors were calculated, encoding texture information. The results suggested differences in the texture characteristics of regions of interest (ROIs) extracted from PD-FSE and STIR sequences. We observed that the ROIs associated with BME exhibited greater local contrast and a wider range of structural diversity compared to the ROIs corresponding to OST. When it comes to STIR sequences, the ROIs related to BME showed higher uniformity in terms of both signal intensity and the variability of local structures compared to the INJ ROIs. A combined radiomic descriptor managed to achieve a high separation ability, with AUC of 0.93 ± 0.02 in the test set. Radiomics analysis may provide a non-invasive and quantitative means to assess the spatial distribution and heterogeneity of bone marrow edema, aiding in its early detection and characterization.

Quantitative analysis of vertebral fat fraction and R2* in osteoporosis using IDEAL-IQ sequence

OBJECTIVE

To investigate the correlation between FF, R2* value of IDEAL-IQ sequence and bone mineral density, and to explore their application value in the osteoporosis.

METHODS

We recruited 105 women and 69 men aged over 30 years who voluntarily underwent DXA and MRI examination of lumbar spine at the same day. Participants were divided into normal, osteopenia and osteoporosis group based on T-score and BMD value of DXA examination. One-way ANOVA was adopted to compare the quantitative parameters among the three groups. Independent samples t-test was utilized to compare FF and R2* value between men and women.Pearson correlation analysis was used to research the correlation between FF, R2* value and BMD.

RESULTS

Age, height, weight, BMD and FF value were significantly different among three groups (p < 0.05). No significant difference was found in FF value between male and female group, while R2* value were significantly different. Vertebral FF was moderately negatively correlated with aBMD, especially in women (r = -0.638, p < 0.001). R2* was mildly to moderately positively correlated with aBMD in men (r = 0.350, p = 0.003), but not in women. Moreover, FF was positively correlated with age, R2* was negatively correlated with age in men, and BMD was negatively correlated with age.

CONCLUSIONS

The vertebral FF value of IDEAL-IQ sequence has the potential to be a new biological marker for the assessment of osteoporosis. Vertebral FF is moderately negatively correlated with aBMD, especially in women, allowing accuratly quantify the bone marrow fat. R2* value is mildly to moderately correlated with BMD in men and can be served as a complementary tool in the assessment of osteoporosis.

Can the greater trochanter/femoral neck signal intensity ratio on coronal T1 weighted images of the hip differentiate normal-abnormal bone mineral density?

A simple index calculated by dividing the greater trochanter signal intensity by that of the femoral neck on coronal T1-weighted magnetic resonance images of the hip may be useful as an opportunistic screening tool to differentiate normal vs. abnormal bone mineral density.

PURPOSE

The aim of this study is to evaluate the efficacy of the greater trochanter/femoral neck (T/N) signal intensity (SI) ratio on T1 weighted images of the hip in differentiating patients with normal vs. abnormal bone mineral density (BMD) using hip dual-energy x-ray absorptiometry (DXA) as the reference.

METHODS

Three BMD groups according to the T score of the femoral neck (i.e., normal, osteopenia, and osteoporosis) were created, and 20 patients were included for each group. The T/N ratio was calculated by dividing the greater trochanter SI by that of the femoral neck on coronal T1-weighted images. Receiver-operator characteristic (ROC) analysis was performed to determine diagnostic efficacy.

RESULTS

The mean age was 59.2±9.4; there were 57 women and 3 men. The mean BMD was 0.67±0.14 g/cm2. The mean T/N ratio for the normal, osteopenia, and osteoporosis groups were 1.37 (±0.12), 1.19 (±0.10), and 1.18 (±0.13), respectively. When the osteopenia and osteoporosis groups were combined into one group, i.e., low BMD group, the mean T/N ratio was 1.18 (±0.11), and it was significantly different from that of the normal BMD group (p<0.00001). In ROC analysis, the area under curve (AUC) for the T/N ratio in the diagnosis of low BMD was 0.870. An optimal cutoff value of 1.28 was found for the differentiation of normal vs. abnormal BMD with 80% sensitivity and 80% specificity.

CONCLUSIONS

The T/N ratio seems to be effective at differentiating patients with normal vs. abnormal BMD and may help triage patients for additional evaluation.

Feasibility Study of 3D FACT and IVIM Sequences in the Evaluation of Female Osteoporosis

BACKGROUND

The aim of this study is to search for the predictive value of 3D fat analysis and calculation technique (FACT) and intravoxel incoherent motion (IVIM) parameters in identifying osteoporosis in women.

METHODS

We enrolled 48 female subjects who underwent 3.0 T MRI, including 3D FACT and IVIM sequences. Bone mineral density (BMD) values and Fracture Risk Assessment (FRAX) scores were obtained. Proton density fat fraction (PDFF) in the bone marrow and the real diffusion (D) value of intervertebral discs were measured on 3D FACT and IVIM images, respectively. Accuracy and bias were assessed by linear regression analysis and Bland-Altman plots. Intraclass correlation coefficients were used to assess the measurements' reproducibility. Spearman's rank correlation was applied to explore the correlation. MRI-based parameters were tested for significant differences among the three groups using ANOVA analyses. A receiver operating characteristic (ROC) analysis was performed.

RESULTS

The PDFF of the vertebral body showed a negative correlation with BMD (R = -0.393, p = 0.005) and a positive correlation with the FRAX score (R = 0.706, p < 0.001). The D value of intervertebral discs showed a positive correlation with BMD (R = 0.321, p = 0.024) and a negative correlation with the FRAX score (R = -0.334, p = 0.019). The area under the curve values from the ROC analysis showed that the 3D FACT and IVIM sequences could accurately differentiate between normal and osteoporosis (AUC = 0.88 using the PDFF; AUC = 0.77 using the D value). The PDFF value demonstrated a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 78.6%, 89.5%, 84.6%, and 85.0%, respectively, in its ability to predict osteoporosis. The D value had a sensitivity, specificity, PPV, and NPV of 63.16%, 92.9%, 65.0%, and 77.8%, respectively, for predicting osteoporosis.

CONCLUSIONS

The 3D FACT- and IVIM-measured PDFF and D values are promising biomarkers in the assessment of bone quality and fracture risk.

Adiponectin overexpression promotes fracture healing through regulating the osteogenesis and adipogenesis balance in osteoporotic mice

INTRODUCTION

Osteoporosis invariably manifests as loss of bone, which is replaced by adipose tissue; this can easily lead to fractures, accompanied by delayed and poor healing. Adiponectin (APN) balances osteogenesis and adipogenesis in bone marrow mesenchymal stem cells (BMSCs). Therefore, this study explored whether adiponectin promotes bone fracture healing by regulating the balance between osteogenesis and adipogenesis.

MATERIALS AND METHODS

We used adenovirus overexpression vectors carrying APN (Ad-APN-GFP) to treat ovariectomized (OVX) mouse BMSCs and osteoporotic bone fractures to investigate the role of APN in bone microenvironment metabolism in osteoporotic fractures. We subsequently established an OVX mice and bone fracture model using Ad-APN-GFP treatment to investigate whether APN could promote bone fracture healing in osteoporotic mice.

RESULTS

The experimental results showed that APN is a critical molecule in diverse differentiation directions in OVX mouse BMSCs, with pro-osteogenesis and anti-adipogenesis properties. Importantly, our study revealed that Ad-APN-GFP treatment facilitates bone generation and healing around the osteoporotic fracture ends. Moreover, we identified that Sirt1 and Wnt signaling were closely related to the pro-osteogenesis and anti-adipogenesis commitment of APN in OVX mouse BMSCs and femoral tissues.

CONCLUSION

We demonstrated that APN overexpression facilitates bone fracture healing in osteoporosis. Furthermore, APN overexpression promoted bone formation in OVX mouse BMSCs and bone fracture ends by regulating the balance between osteogenesis and adipogenesis both in vitro and in vivo.

Association of lumbar vertebral bone marrow and paraspinal muscle fat composition with intervertebral disc degeneration: 3T quantitative MRI findings from the population-based KORA study

OBJECTIVE

To assess the association of lumbar bone marrow adipose tissue fat fraction (BMAT-FF) and paraspinal muscle proton density fat fraction (PDFF) and their interplay with intervertebral disc degeneration (IVDD).

METHODS

In this retrospective cross-sectional study based on a prospective population-based cohort, BMAT-FF and PDFF of asymptomatic individuals were calculated based on 3T-MRI dual-echo and multi-echo Dixon VIBE sequences. IVDD was assessed at motion segments L1 to L5 and dichotomized based on Pfirrmann grade ≥ 4 and/or presence of other severe degenerative changes or spinal abnormalities at least at one segment. Pearson's correlation coefficients were calculated for BMAT-FF and PDFF. Univariable and multivariable logistic regression models for IVDD were calculated.

RESULTS

Among 335 participants (mean age: 56.2 ± 9.0 years, 43.3% female), the average BMI was 27.7 ± 4.5 kg/m2 and the prevalence of IVDD was high (69.9%). BMAT-FF and PDFF were significantly correlated (r = 0.31-0.34; p < 0.001). The risk for IVDD increased with higher PDFF (OR = 1.45; CI 1.03, 2.04) and BMAT-FF (OR = 1.56; CI 1.16, 2.11). Pairwise combinations of PDFF and BMAT-FF quartiles revealed a lower risk for IVDD in individuals in the lowest BMAT-FF and PDFF quartile (OR = 0.21; CI 0.1, 0.48). Individuals in the highest BMAT-FF and PDFF quartile showed an increased risk for IVDD (OR = 5.12; CI 1.17, 22.34) CONCLUSION: Lumbar BMAT-FF and paraspinal muscle PDFF are correlated and represent both independent and additive risk factors for IVDD. Quantitative MRI measurements of paraspinal myosteatosis and vertebral bone marrow fatty infiltration may serve as imaging biomarkers to assess the individual risk for IVDD.

KEY POINTS

• Fat composition of the lumbar vertebral bone marrow is positively correlated with paraspinal skeletal muscle fat. • Higher fat-fractions of lumbar vertebral bone marrow and paraspinal muscle are both independent as well as additive risk factors for intervertebral disc degeneration. • Quantitative magnetic resonance imaging measurements of bone marrow and paraspinal muscle may serve as imaging biomarkers for intervertebral disc degeneration.

mDIXON-Quant technique diagnostic accuracy for assessing bone mineral density in male adult population

BACKGROUND

To investigate the diagnostic efficacy of mDIXON-Quant technique for prediction of bone loss in male adults.

METHODS

One hundred thirty-eight male adults were divided into normal, osteopenia, and osteoporosis groups based on DXA and QCT for the lumbar spine. Differences in mDIXON-Quant parameters [fat fraction (FF) and T2^* value] among three groups, as well as the correlation of mDIXON-Quant parameters and bone mineral density (BMD) were analyzed. The areas under the curves (AUCs) for mDIXON-Quant parameters for prediction of low bone mass were calculated.

RESULTS

According to DXA standard, FF and T2^* value were significantly increased in osteoporosis group compared with normal group (P = 0.012 and P < 0.001). According to QCT standard, FF was significantly increased in osteopenia and osteoporosis groups compared with normal group (both P < 0.001). T2^* values were significantly different among three groups (all P < 0.05). After correction for age and body mass index, FF was negatively correlated with areal BMD and volumetric BMD (r = -0.205 and -0.604, respectively; both P < 0.05), and so was T2^* value (r = -0.324 and -0.444, respectively; both P < 0.05). The AUCs for predicting low bone mass according to DXA and QCT standards were 0.642 and 0.898 for FF, 0.648 and 0.740 for T2^* value, and 0.677 and 0.920 for both combined, respectively.

CONCLUSIONS

FF combined with T2^* value has a better diagnostic efficacy than FF or T2^* value alone in prediction of low bone mass in male adults, which is expected to be a promising MRI method for the screening of bone quality.

TRIAL REGISTRATION

ChiCTR1900024511 (Registered 13-07-2019).

Advances in Bone Marrow Imaging: Strengths and Limitations from a Clinical Perspective

Conventional magnetic resonance imaging (MRI) remains the modality of choice to image bone marrow. However, the last few decades have witnessed the emergence and development of novel MRI techniques, such as chemical shift imaging, diffusion-weighted imaging, dynamic contrast-enhanced MRI, and whole-body MRI, as well as spectral computed tomography and nuclear medicine techniques. We summarize the technical bases behind these methods, in relation to the common physiologic and pathologic processes involving the bone marrow. We present the strengths and limitations of these imaging methods and consider their added value compared with conventional imaging in assessing non-neoplastic disorders like septic, rheumatologic, traumatic, and metabolic conditions. The potential usefulness of these methods to differentiate between benign and malignant bone marrow lesions is discussed. Finally, we consider the limitations hampering a more widespread use of these techniques in clinical practice.

Novel micro-MRI approach for subchondral trabecular bone analysis in patients with hip osteoarthritis is comparable to micro-CT approach

AIM

To test the agreement between a newly developed micro-magnetic resonance imaging (MRI) analysis of the subchondral bone and the micro-computed tomography (CT) approach.

METHODS

Samples obtained from 10 patients with osteoarthritis undergoing total hip arthroplasty were scanned with a 7.0 T micro-MRI. Proton density-weighted images and proton density-weighted images with fat suppression were obtained. The results were validated with a micro-CT device. Micro-MRI and micro-CT scans of the same sample were aligned, and regions of interest were delineated on equal areas of the sample. Bone volume fraction was calculated by using in-house plugins. The agreement between the methods was tested with Bland-Altman analysis.

RESULTS

The agreement between the methods was good, with average difference of 2.167%. The differences between the methods were not significant (P=0.272, t test).

CONCLUSION

The novel micro-MRI approach could be used for subchondral bone analysis. With further optimization for clinical MRI machines, the approach can be also used in the diagnostics of hip osteoarthritis.

Novel micro-MRI approach for subchondral trabecular bone analysis in patients with hip osteoarthritis is comparable to micro-CT approach

AIM

To test the agreement between a newly developed micro-magnetic resonance imaging (MRI) analysis of the subchondral bone and the micro-computed tomography (CT) approach.

METHODS

Samples obtained from 10 patients with osteoarthritis undergoing total hip arthroplasty were scanned with a 7.0 T micro-MRI. Proton density-weighted images and proton density-weighted images with fat suppression were obtained. The results were validated with a micro-CT device. Micro-MRI and micro-CT scans of the same sample were aligned, and regions of interest were delineated on equal areas of the sample. Bone volume fraction was calculated by using in-house plugins. The agreement between the methods was tested with Bland-Altman analysis.

RESULTS

The agreement between the methods was good, with average difference of 2.167%. The differences between the methods were not significant (P=0.272, t test).

CONCLUSION

The novel micro-MRI approach could be used for subchondral bone analysis. With further optimization for clinical MRI machines, the approach can be also used in the diagnostics of hip osteoarthritis.

Behavior during aging of bone-marrow fatty-acids profile in women's calcaneus to search for early potential osteoporotic biomarkers: a 1H-MR Spectroscopy study

AIM

Identify new potential biomarkers of osteoporosis at an early stage, by magnetic resonance spectroscopy (MRS), studying early changes in the metabolic profile of bone-marrow fatty acids in women's calcanei during healthy aging and osteoporosis status.

METHODS

Single voxel MRS was performed by using a point resolved spectroscopy (PRESS) sequence at 3T. Thirty-four Caucasian women (age range: 22-59 years) were recruited to investigate calcaneus bone marrow. The cohort was constituted of four groups according to age, menopausal status, and T-score evaluated after a DXA examination on the femoral neck. Women were classified in young control (n = 11, mean age = 26.5 ± 3.8 y, age range: 22-34 years), perimenopausal groups (n = 11, mean age = 42.0 ± 3.6 y, age range: 37-47 years), postmenopausal group (n = 9, mean age = 55.4 ± 2.9 y, age range: 50-59 years, mean T-score = -1.70 ± 0.50) and osteoporotic group (n = 6, mean age = 53.0 ± 2.8 y, age range: 50-58 years, mean T-score = -2.54 ± 0.10). The total lipid content (TL), the Unsaturation Index (UI), and the fraction of unsaturated/polyunsaturated fatty acid (f_UFA and f_PUFA) were calculated.

RESULTS

TL was significantly correlated with age (r = 0.73, p < 0.001). TL increases linearly with age in the young + perimenopausal population (r = 0.92, p < 0.001) but this trend is not significant in the postmenopausal subject (r = 0.48, p = 0.07). No significant correlation was found between T-Score and TL in postmenopausal and osteoporotic women, whereas a significant correlation was found between TL and time interval (t_p) between the age at menopause and the age of the subject at the MRS examination. Conversely, no correlation was found between T-score and t_p. The unsaturation index (UI) does not significantly discriminate between osteoporotic, peri- and postmenopausal women. On the other hand, f_UFA is significantly different in peri-menopausal and osteoporotic subjects (p = 0.02), while f_PUFA is significantly different both between peri- and postmenopausal women (p = 0.05) and postmenopausal and osteoporotic subjects (p = 0.03). Both f_UFA and f_PUFA did not correlate with subjects' age.

CONCLUSION

In the female calcaneus, f_UFA and f_PUFA are promising measurable quantities for the characterization of bone marrow's composition potentially correlated with the development of osteoporosis, whereas UI does not differentiate between subjects of varying osteoporotic status. The fact that the TL in the calcaneus is correlated with t_p, indicates that active metabolic changes are still occurring in these subjects, giving complementary information to the DXA about the changes in bone marrow's composition which may affect the whole bone health.

Patient physiology influences the MRI-based vertebral bone quality score

BACKGROUND CONTEXT

Osteoporosis is a critical issue affecting postmenopausal women and the aging population. A novel magnetic resonance imaging (MRI)-based vertebral bone quality (VBQ) score has been proposed as a method to identify poor bone quality and predict fragility fractures. The diagnostic accuracy of this tool is not well understood.

PURPOSE

To examine the ability of VBQ to predict osteoporosis and osteopenia, its correlation with dual-energy x-ray absorptiometry (DEXA), and the influence of patient-specific factors upon the score.

STUDY DESIGN

Retrospective cohort study.

PATIENT SAMPLE

Patients over the age of 18 with a DEXA scan and noncontrast, T1-weighted MRI of the lumbar spine completed within a 2-year period.

OUTCOME MEASURES

Area-under-curve (AUC) values of the VBQ score predicting osteopenia and osteoporosis when controlling for patient characteristics.

METHODS

Patients with noncontrast, T1-weighted MRIs of the lumbar spine and DEXA scans completed within a 2-year time frame were retrospectively reviewed. Patient demographics and medical risk factors for osteoporosis were identified and compared. VBQ scores were measured by two trained researchers and interrater reliability was calculated. Patients were separated into three groups defined by lowest DEXA T-score: Healthy Bone, Osteopenia, and Osteoporosis. analysis of variance, Kruskal-Wallis test, chi-square, t tests, Mann-Whitney U tests, and multivariate linear regression were performed to examine the relationship between patient characteristics, DEXA t-scores, and VBQ scores. Receiver operating characteristic analysis and AUC values were generated for the prediction of osteopenia and osteoporosis.

RESULTS

A total of 156 patients were included for analysis. Sufficient inter-rater reliability was determined for VBQ measures (intraclass correlation coefficient: 0.81). Most patients were female (83%), postmenopausal (81%), and had hyperlipidemia (64%). Patients with hyperlipidemia and healthy bone density by DEXA had elevated baseline VBQ scores (p<.001) reflective of values seen in osteopenia and osteoporosis. The AUC of the VBQ score predicting osteopenia and osteoporosis changed to be more concordant with DEXA results after controlling for hyperlipidemia (AUC=0.72, 0.70 vs. AUC=0.88, 0.89; p<.001). Sub-analysis of hyperlipidemia subtypes revealed that elevated high-density lipoprotein is associated with elevated VBQ scores.

CONCLUSIONS

Hyperlipidemia increased the MRI-based VBQ score in our healthy bone population. The high signal intensities resembled values seen in osteopenia and osteoporosis, suggesting that physiologic variables which impact bone composition may influence the VBQ score. Specifically, elevated high-density lipoprotein may contribute to this. The microarchitectural changes and the clinical implications of these factors need further exploration.

Chemical Shift-Encoded MRI of Bone Metabolic Markers in Ankylosing Spondylitis

Objective

To investigate the feasibility and correlation of sacroiliac joint (SIJ) fat fraction (FF) and R2^∗ as markers of bone metabolism in patients with ankylosing spondylitis (AS).

Methods

75 AS patients were classified into an early active group (EA), late active group (LA), and inactive group (IA). Additionally, 54 matched healthy individuals were selected to be part of the normal control group (NC). All participants underwent chemical shift encoded based MRI (IDEAL-IQ) and routine clinical SIJ MRI at 3.0 T. FF and R2^∗ were measured in subchondral bone, bone marrow edema (BME), and fat metaplasia (FM). Out of the participants, 39 with BME lesions (15 from EA, 16 from LA, 8 from IA) and 39 with FM lesions (9 from EA, 17 from LA, 13 from IA) were included. Differences in FF, R2^∗ value for subchondral bone of all participants and for BME, FM lesions were evaluated. Subsequently, different stages of BME and FM in patient groups were compared, and the relationship between FF and R2^∗ was analyzed.

Results

A significant difference in FF was demonstrated among the BME, FM and the normal bone marrow (p < 0.001), meanwhile, the difference of R2^∗ value in FM was significantly lower (p = 0.034, 0.012) than that of BME and that of normal bone marrow. At lever of different lesions, only the FF for BME was significantly different among 3 patient groups (p = 0.001), while there was no significantly different FF for FM among 3 patient groups. Unlike in BME lesions, the FF in FM lesions had a negative correlation with R2^∗ (p < 0.001, r = −0.488).

Conclusion

FF and R2^∗ measurements help to quantitatively analyze the bone marrow fat composition and bony trabecular microstructure changes in AS, providing a noninvasive and accurate assessment basis for AS bone metabolism abnormalities.

Associations between Bone Mineral Density and Longitudinal Changes of Vertebral Bone Marrow and Paraspinal Muscle Composition Assessed Using MR-Based Proton Density Fat Fraction and T2* Maps in Patients with and without Osteoporosis

Background: Proton-density fat fraction (PDFF) and T2* of the vertebrae, as well as the cross-sectional area (CSA) of the paraspinal musculature (PSM), have been suggested as biomarkers for bone fragility. The aim of this study was to longitudinally assess changes in PDFF, T2* and CSA of the PSM over 6 months in patients with and without osteoporosis. Methods: Opportunistic bone mineral density (BMD) measurements (BMD < 120 mg/cm3) were obtained from a CT acquired during the clinical routine work up in osteoporotic/osteopenic patients (n = 29, mean age 72.37 ± 10.12 years, 16 women). These patients were frequency-matched for age and sex to subjects with normal BMD values (n = 29). All study patients underwent 3T MR imaging at baseline and 6-month follow up, including spoiled gradient echo sequences for chemical shift encoding-based water-fat separation, from which T2* and PDFF values of the lumbar spine and the PSM were obtained. Moreover, the CSA of the PSM was assessed longitudinally. Changes in T2*, PDFF and CSA over 6 months were calculated for the vertebrae and PSM and associations with baseline BMD values were assessed. Results: The change in CSA of the PSM over 6 months was significantly lower in the osteoporotic/osteopenic group (−91.5 ± 311.7 mm2), compared to the non-osteoporotic group, in which the CSA increased (29.9 ± 164.0 mm2, p = 0.03). In a further analysis, patients with higher vertebral PDFF at baseline showed a significantly stronger increase in vertebral T2*, compared to those patients with lower vertebral PDFF at baseline (0.9 ± 1.6 ms vs. 0.0 ± 1.8 ms, p = 0.04). Moreover, patients with higher PSM PDFF at baseline showed a significantly stronger increase in vertebral T2*, compared to those patients with lower PSM PDFF at baseline (0.9 ± 2.0 ms vs. 0.0 ± 1.3 ms, p = 0.03). Conclusion: The PSM CSA decreased significantly longitudinally in patients with osteoporosis/osteopenia, compared to those without. Additionally, higher vertebral and PSM PDFF at baseline were associated with stronger changes in vertebral bone marrow T2*. Therefore, longitudinal PDFF and T2* mapping may be useful quantitative radiation-free tools for the assessment and prediction of muscle and bone health in patients with suspected osteoporosis/osteopenia.

Bone quality in patients with osteoporosis undergoing lumbar fusion surgery: analysis of the MRI-based vertebral bone quality score and the bone microstructure derived from microcomputed tomography

BACKGROUND CONTEXT

Osteoporosis is a risk factor for instrumentation failure in spine surgery. Bone strength is commonly assessed by bone mineral density (BMD) as a surrogate marker. However, BMD represents only a portion of bone strength and does not capture the qualitative dimensions of bone. Recently, the magnetic resonance imaging (MRI)-based vertebral bone quality (VBQ) score was introduced as a novel marker of bone quality. However, it is still unclear if the VBQ score correlates with in-vivo bone microstructure.

PURPOSE

The aims of the study were (1) to demonstrate differences in MRI-based (VBQ) and in-vivo (microcomputed tomography; μCT) bone quality between osteopenic/osteoporotic and normal bone, (2) to show the correlation between VBQ, bone microstructure and volumetric BMD (vBMD), and (3) to determine the predictive value of the VBQ score for the prevalence of osteopenia/osteoporosis.

STUDY DESIGN/SETTING

Retrospective cross-sectional study.

PATIENT SAMPLE

267 patients who underwent posterior lumbar fusion surgery from 2014 to 2021 at a single academic institution. Bone biopsies were harvested intraoperatively in 118 patients.

OUTCOME MEASURES

VBMD, VBQ score, and bone microstructure parameters derived from μCT.

METHODS

Quantitative computed tomography (QCT) measurements were performed at the lumbar spine and the L1/L2 average was used to categorize patients with a vBMD ≤120mg/cm³ as osteopenic/osteoporotic. The VBQ score was determined by dividing the median signal intensity of the L1-L4 vertebrae by the signal intensity of the cerebrospinal fluid using sagittal T1-weighted MRI scans. Intraoperative bone biopsies from the posterior superior iliac spine were obtained and evaluated with μCT. VBQ scores and μCT parameters were compared between the normal and the osteopenic/osteoporotic group. Correlations between VBQ score, μCT parameters and vBMD were assessed with Spearman's correlation (ρ). Receiver operating characteristic (ROC) analysis was performed to determine the VBQ score as a predictor for osteopenia/osteoporosis. Multiple linear regression analysis with vBMD L1/L2 as outcome was used to identify independent predictors from VBQ, μCT parameters and demographics.

RESULTS

267 patients (55.8% female, age 63.3 years, BMI 29.7 kg/m²; n=118 with bone biopsy) with a prevalence of osteopenia/osteoporosis of 65.2% were analyzed. In the osteopenic/osteoporotic group the VBQ score, structured model index (SMI), and trabecular separation (Tb.Sp) were significantly higher, whereas bone volume fraction (BV/TV), connectivity density (Conn.D) and trabecular number (Tb.N) were significantly lower. There were significant correlations between VBQ and μCT parameters ranging from ρ=-.387 to ρ=0.314 as well as between vBMD and μCT parameters ranging from ρ=-.425 to ρ=.421, and vBMD and VBQ (ρ=-.300, p<.001). ROC analysis discriminated osteopenia/osteoporosis with a sensitivity of 84.7% and a specificity of 40.6% at a VBQ score threshold value of 2.18. Age, BV/TV and trabecular thickness (Tb.Th), but not VBQ, were significant independent predictors for vBMD (corrected R²=0.434).

CONCLUSIONS

This study demonstrated for the first time that the VBQ score is associated with trabecular microstructure determined by μCT. The bone microstructure and VBQ score were significantly different in patients with impaired vBMD. However, the ability to predict osteopenia/osteoporosis with the VBQ score was moderate. The VBQ score appears to reflect additional bone quality characteristics and might have a complementary role to vBMD. This enhances our understanding of the biological background of the radiographic VBQ score and might be a take-off point to evaluate the clinical utility of it as non-invasive screening tool for bone quality.

Associations of Texture Features of Proton Density Fat Fraction Maps between Lumbar Vertebral Bone Marrow and Paraspinal Musculature

Chemical shift encoding-based water−fat MRI (CSE-MRI)-derived proton density fat fraction (PDFF) has been used for non-invasive assessment of regional body fat distributions. More recently, texture analysis (TA) has been proposed to reveal even more detailed information about the vertebral or muscular composition beyond PDFF. The aim of this study was to investigate associations between vertebral bone marrow and paraspinal muscle texture features derived from CSE-MRI-based PDFF maps in a cohort of healthy subjects. In this study, 44 healthy subjects (13 males, 55 ± 30 years; 31 females, 39 ± 17 years) underwent 3T MRI including a six-echo three-dimensional (3D) spoiled gradient echo sequence used for CSE-MRI at the lumbar spine and the paraspinal musculature. The erector spinae muscles (ES), the psoas muscles (PS), and the vertebral bodies L1-4 (LS) were manually segmented. Mean PDFF values and texture features were extracted for each compartment. Features were compared between males and females using logistic regression analysis adjusted for age and body mass index (BMI). All texture features of ES except for Sum Average were significantly (p < 0.05) different between men and women. The three global texture features (Variance, Skewness, Kurtosis) for PS as well as LS showed a significant difference between male and female subjects (p < 0.05). Mean PDFF measured in PS and ES was significantly higher in females, but no difference was found for the vertebral bone marrow’s PDFF. Partial correlation analysis between the texture features of the spine and the paraspinal muscles revealed a highly significant correlation for Variance(global) (r = 0.61 for ES, r = 0.62 for PS; p < 0.001 respectively). Texture analysis using PDFF maps based on CSE-MRI revealed differences between healthy male and female subjects. Global texture features in the lumbar vertebral bone marrow allowed for differentiation between men and women, when the overall PDFF was not significantly different, indicating that PDFF maps may contain detailed and subtle textural information beyond fat fraction. The observed significant correlation of Variance(global) suggests a metabolic interrelationship between vertebral bone marrow and the paraspinal muscles.

Differentiation of bone metastases from benign red marrow depositions of the spine: the role of fat-suppressed T2-weighted imaging compared to fat fraction map

OBJECTIVE

To differentiate bone metastases (BMs) from benign red marrow depositions (BRMs) of the spine using quantitative parameters derived from fat-suppressed T2-weighted imaging (T2 FS) and fat fraction (FF) map METHODS: One hundred eleven lesions, divided into 62 BMs and 49 BRMs according to MR images and either bone scan or PET-CT, were assessed with T2 FS and FF map. Two radiologists independently measured quantitative parameters from the ROIs in the lesions, including fat-suppressed (FS) T2 ratio (ratio of lesion FS T2 signal intensity [SI] to normal marrow FS T2 SI), FF, and FF ratio (ratio of lesion FF to normal marrow FF). The mean values of these parameters were compared between the two groups. To evaluate the diagnostic utilities of individual (FS T2 ratio, FF, and FF ratio) and combined parameters, ROC curves were analyzed. For the ROC curves among the individual parameters and their combinations, AUCs were compared.

RESULTS

The FS T2 ratio of BMs was significantly higher than that of BRMs (2.638 vs. 1.155 [p < 0.001]). The FF and FF ratio of BMs were significantly lower than those of BRMs (FF, 3.554% vs. 20.038% [p < 0.001]; FF ratio, 0.072 vs. 0.364 [p < 0.001]). The ROC AUCs of individual and combined parameters ranged from 0.941 to 0.980. The AUCs of all individual parameters and their combinations did not demonstrate statistically significant differences.

CONCLUSION

The FS T2 ratio, FF, and FF ratio can be useful in differentiating BMs from BRMs with or without any combination of the parameters.

KEY POINTS

• Quantitative parameters derived from fat-suppressed T2-weighted imaging and fat fraction map could be used to differentiate bone metastases from benign red marrow depositions with or without any combination of the parameters. • Quantitative parameters of fat-suppressed T2-weighted imaging provide diagnostic performance similar to those of fat fraction map in differentiating bone metastases from benign red marrow depositions.

Ultrashort time-to-echo T2* and T2* relaxometry for evaluation of lumbar disc degeneration: a comparative study

Background

To compare potential of ultrashort time-to-echo (UTE) T2* mapping and T2* values from T2*-weighted imaging for assessing lumbar intervertebral disc degeneration (IVDD),with Pfirrmann grading as a reference standard.

Methods

UTE-T2* and T2* values of 366 lumbar discs (L1/2-L5/S1) in 76 subjects were measured in 3 segmented regions: anterior annulus fibrosus, nucleus pulposus (NP), and posterior annulus fibrosus. Lumbar intervertebral discs were divided into 3 categories based on 5-level Pfirrmann grading: normal (Pfirrmann grade I),early disc degeneration (Pfirrmann grades II-III), and advanced disc degeneration (Pfirrmann grades IV-V). Regional differences between UTE-T2* and T2* relaxometry and correlation with degeneration were statistically analyzed.

Results

UTE-T2* and T2*value correlated negatively with Pfirrmann grades (P < 0.001). In NP, correlations with Pfirrmann grade were high with UTE-T2* values (r =  − 0.733; P < 0.001) and moderate with T2* values (r = -0.654; P < 0.001). Diagnostic accuracy of detecting early IVDD was better with UTE-T2* mapping than T2* mapping (P < 0.05),with receiver operating characteristic analysis area under the curve of 0.715–0.876.

Conclusions

UTE-T2* relaxometry provides another promising magnetic resonance imaging sequence for quantitatively evaluate lumbar IVDD and was more accurate than T2*mapping in the earlier stage degenerative process.

Adding liver R2* quantification to proton density fat fraction MRI of vertebral bone marrow improves the prediction of osteoporosis

OBJECTIVES

To assess the predictive value of the combination of bone marrow (BM) proton density fat fraction (PDFF) and liver R2* for osteopenia and osteoporosis and the additional role of liver R2*.

METHODS

A total of 107 healthy women were included between June 2019 and January 2021. Each participant underwent dual-energy X-ray absorptiometry (DXA) and chemical shift-encoded 3.0-T MRI. PDFF measurements were performed for each lumbar vertebral body, and R2* measurements were performed in liver segments. Agreement among measurements was assessed by Bland-Altman analysis. Receiver operating characteristic (ROC) curves were generated to select optimised cut-offs for BM PDFF and liver R2*. Univariable and multivariable logistic regressions were performed. The C statistic and continuous net reclassification improvement (NRI) were adopted to explore the incremental predictive ability of liver R2*.

RESULTS

Bone mass decreased in 42 cases (39.3%) and nonbone mass decreased in 65 cases (60.7%). There were significant differences among the age groups, menopausal status groups, PDFF > 45.0% groups, and R2* > 67.7 groups. Each measurement had good reproducibility. The odds ratios (95% CIs) were 4.05 (1.22-13.43) for PDFF and 4.34 (1.41-13.35) for R2*. The C statistic (95% CI) without R2* was 0.888 (0.827-0.950), and with R2* was 0.900 (0.841-0.960). The NRI resulting from the combination of PDFF and R2* was 75.6% (p < 0.01).

CONCLUSION

The predictive improvement over the use of BM PDFF and other traditional risk factors demonstrates the potential of liver R2* as a biomarker for osteopenia and osteoporosis in healthy women.

KEY POINTS

• Liver R2* is a biomarker for the assessment of osteopenia and osteoporosis. • Liver R2* improved the ability to predict osteopenia and osteoporosis. • The intra- and interobserver measurements showed high agreement.

Imaging of the Osteoporotic Spine - Quantitative Approaches in Diagnostics and for the Prediction of the Individual Fracture Risk

Osteoporosis is a highly prevalent systemic skeletal disease that is characterized by low bone mass and microarchitectural bone deterioration. It predisposes to fragility fractures that can occur at various sites of the skeleton, but vertebral fractures (VFs) have been shown to be particularly common. Prevention strategies and timely intervention depend on reliable diagnosis and prediction of the individual fracture risk, and dual-energy X-ray absorptiometry (DXA) has been the reference standard for decades. Yet, DXA has its inherent limitations, and other techniques have shown potential as viable add-on or even stand-alone options. Specifically, three-dimensional (3 D) imaging modalities, such as computed tomography (CT) and magnetic resonance imaging (MRI), are playing an increasing role. For CT, recent advances in medical image analysis now allow automatic vertebral segmentation and value extraction from single vertebral bodies using a deep-learning-based architecture that can be implemented in clinical practice. Regarding MRI, a variety of methods have been developed over recent years, including magnetic resonance spectroscopy (MRS) and chemical shift encoding-based water-fat MRI (CSE-MRI) that enable the extraction of a vertebral body's proton density fat fraction (PDFF) as a promising surrogate biomarker of bone health. Yet, imaging data from CT or MRI may be more efficiently used when combined with advanced analysis techniques such as texture analysis (TA; to provide spatially resolved assessments of vertebral body composition) or finite element analysis (FEA; to provide estimates of bone strength) to further improve fracture prediction. However, distinct and experimentally validated diagnostic criteria for osteoporosis based on CT- and MRI-derived measures have not yet been achieved, limiting broad transfer to clinical practice for these novel approaches. KEY POINTS::   · DXA is the reference standard for diagnosis and fracture prediction in osteoporosis, but it has important limitations.. · CT- and MRI-based methods are increasingly used as (opportunistic) approaches.. · For CT, particularly deep-learning-based automatic vertebral segmentation and value extraction seem promising.. · For MRI, multiple techniques including spectroscopy and chemical shift imaging are available to extract fat fractions.. · Texture and finite element analyses can provide additional measures for vertebral body composition and bone strength.. CITATION FORMAT: · Sollmann N, Kirschke JS, Kronthaler S et al. Imaging of the Osteoporotic Spine - Quantitative Approaches in Diagnostics and for the Prediction of the Individual Fracture Risk. Fortschr Röntgenstr 2022; DOI: 10.1055/a-1770-4626.

On quantification errors of R 2 * $$ {R}_2^{\ast } $$ and proton density fat fraction mapping in trabecularized bone marrow in the static dephasing regime

PURPOSE

To study the effect of field inhomogeneity distributions in trabecularized bone regions on the gradient echo (GRE) signal with short TEs and to characterize quantification errors on R 2 * $$ {R}_2^{\ast } $$ and proton density fat fraction (PDFF) maps when using a water-fat model with an exponential R 2 * $$ {R}_2^{\ast } $$ decay model at short TEs.

METHODS

Field distortions were simulated based on a trabecular bone micro CT dataset. Simulations were performed for different bone volume fractions (BV/TV) and for different bone-fat composition values. A multi-TE UTE acquisition was developed to acquire multiple UTEs with random order to minimize eddy currents. The acquisition was validated in phantoms and applied in vivo in a volunteer's ankle and knee. Chemical shift encoded MRI (CSE-MRI) based on a Cartesian multi-TE GRE scan was acquired in the spine of patients with metastatic bone disease.

RESULTS

Simulations showed that signal deviations from the exponential signal decay at short TEs were more prominent for a higher BV/TV. UTE multi-TE measurements reproduced in vivo the simulation-based predicted behavior. In regions with high BV/TV, the presence of field inhomogeneities induced an R 2 * $$ {R}_2^{\ast } $$ underestimation in trabecularized bone marrow when using CSE-MRI at 3T with a short TE.

CONCLUSION

R 2 * $$ {R}_2^{\ast } $$ can be underestimated when using short TEs (<2 ms at 3 T) and a water-fat model with an exponential R 2 * $$ {R}_2^{\ast } $$ decay model in multi-echo GRE acquisitions of trabecularized bone marrow.

Opportunistic Use of Lumbar Magnetic Resonance Imaging for Osteoporosis Screening

Magnetic resonance imaging (MRI) is a routine assessment before spine surgery. We found that the opportunistic use of MRI with the vertebral bone quality (VBQ) score has good diagnostic ability, with a threshold value of VBQ > 3.0, in recognizing patients who may need further osteoporosis evaluation.

INTRODUCTION

The purpose of this study was to determine whether the opportunistic use of magnetic resonance imaging (MRI) is useful for identifying spine surgical patients who need further osteoporosis evaluation.

METHODS

This retrospective study evaluated 83 thoracolumbar spine surgery patients age ≥ 50 who received T1-weighted MRI. Opportunistic MRI was evaluated with the vertebral bone quality (VBQ) score, VBQ (fat) score, and signal-to-noise ratio (SNR). Each uses the median L1-L4 vertebral body signal intensities (SI) divided by either the L3 cerebrospinal fluid (CSF) SI, average SI of the L1 and S1 dorsal fat, or standard deviation (SD) of the background SI dorsal to the skin. Single-level VBQ was calculated as the ratio of the L1 vertebral body and L1 CSF SIs. Receiver-operator curve analysis was performed to determine diagnostic ability.

RESULTS

The mean age was 70.10, 80% were female, and 96% were Caucasian. The mean ± SD VBQ, single-level VBQ, VBQ (fat), and SNR were 3.39 ± 0.68, 3.56 ± 0.81, 3.95 ± 1.89, and 113.18 ± 77.26, respectively. Using area under the curve, the diagnostic ability of VBQ, single-level VBQ, VBQ (fat), and SNR for clinical osteoporosis were 0.806, 0.779, 0.608, and 0.586, respectively. Diagnostic threshold values identified with optimal sensitivity and specificity were VBQ of 2.95 and single-level VBQ of 3.06.

CONCLUSION

Opportunistic use of MRI is a simple, effective tool that may help recognize patients who are at risk for complications related to bone disease. A VBQ > 3.0 can identify patients who need additional diagnostic evaluation.

MR-based proton density fat fraction (PDFF) of the vertebral bone marrow differentiates between patients with and without osteoporotic vertebral fractures

The bone marrow proton density fat fraction (PDFF) assessed with MRI enables the differentiation between osteoporotic/osteopenic patients with and without vertebral fractures. Therefore, PDFF may be a potentially useful biomarker for bone fragility assessment.

INTRODUCTION

To evaluate whether magnetic resonance imaging (MRI)-based proton density fat fraction (PDFF) of vertebral bone marrow can differentiate between osteoporotic/osteopenic patients with and without vertebral fractures.

METHODS

Of the 52 study patients, 32 presented with vertebral fractures of the lumbar spine (66.4 ± 14.4 years, 62.5% women; acute low-energy osteoporotic/osteopenic vertebral fractures, N = 25; acute high-energy traumatic vertebral fractures, N = 7). These patients were frequency matched for age and sex to patients without vertebral fractures (N = 20, 69.3 ± 10.1 years, 70.0% women). Trabecular bone mineral density (BMD) values were derived from quantitative computed tomography. Chemical shift encoding-based water-fat MRI of the lumbar spine was performed, and PDFF maps were calculated. Associations between fracture status and PDFF were assessed using multivariable linear regression models.

RESULTS

Over all patients, mean PDFF and trabecular BMD correlated significantly (r =  - 0.51, P < 0.001). In the osteoporotic/osteopenic group, those patients with osteoporotic/osteopenic fractures had a significantly higher PDFF than those without osteoporotic fractures after adjusting for age, sex, weight, height, and trabecular BMD (adjusted mean difference [95% confidence interval], 20.8% [10.4%, 30.7%]; P < 0.001), although trabecular BMD values showed no significant difference between the subgroups (P = 0.63). For the differentiation of patients with and without vertebral fractures in the osteoporotic/osteopenic subgroup using mean PDFF, an area under the receiver operating characteristic (ROC) curve (AUC) of 0.88 (P = 0.006) was assessed. When evaluating all patients with vertebral fractures, those with high-energy traumatic fractures had a significantly lower PDFF than those with low-energy osteoporotic/osteopenic vertebral fractures (P < 0.001).

CONCLUSION

MR-based PDFF enables the differentiation between osteoporotic/osteopenic patients with and without vertebral fractures, suggesting the use of PDFF as a potential biomarker for bone fragility.

Fully automated radiomic screening pipeline for osteoporosis and abnormal bone density with a deep learning-based segmentation using a short lumbar mDixon sequence

BACKGROUND

Although lumbar bone marrow fat fraction (BMFF) has been demonstrated to be predictive of osteoporosis, its utility is limited by the requirement of manual segmentation. Additionally, quantitative features beyond simple BMFF average remain to be explored. In this study, we developed a fully automated radiomic pipeline using deep learning-based segmentation to detect osteoporosis and abnormal bone density (ABD) using a <20 s modified Dixon (mDixon) sequence.

METHODS

In total, 222 subjects underwent quantitative computed tomography (QCT) and lower back magnetic resonance imaging (MRI). Bone mineral density (BMD) were extracted from L1-L3 using QCT as the reference standard; 206 subjects (48.8±14.9 years old, 140 females) were included in the final analysis, and were divided temporally into the training/validation set (142/64 subjects). A deep-learning network was developed to perform automated segmentation. Radiomic models were built using the same training set to predict ABD and osteoporosis using the mDixon maps. The performance was evaluated using the temporal validation set comprised of 64 subjects, along with the automated segmentation. Additional 25 subjects (56.1±8.8 years, 14 females) from another site and a different scanner vendor was included as independent validation to evaluate the performance of the pipeline.

RESULTS

The automated segmentation achieved an outstanding mean dice coefficient of 0.912±0.062 compared to manual in the temporal validation. Task-based evaluation was performed in the temporal validation set, for predicting ABD and osteoporosis, the area under the curve, sensitivity, specificity, and accuracy were 0.925/0.899, 0.923/0.667, 0.789/0.873, 0.844/0.844, respectively. These values were comparable to that of manual segmentation. External validation (cross-vendor) was also performed; the area under the curve, sensitivity, specificity, and accuracy were 0.688/0.913, 0.786/0.857, 0.545/0.944, 0.680/0.920 for ABD and osteoporosis prediction, respectively.

CONCLUSIONS

Our work is the first attempt using radiomics to predict osteoporosis with BMFF map, and the deep-learning based segmentation will further facilitate the clinical utility of the pipeline as a screening tool for early detection of ABD.

Gender- and Age-Associated Differences in Bone Marrow Adipose Tissue and Bone Marrow Fat Unsaturation Throughout the Skeleton, Quantified Using Chemical Shift Encoding-Based Water-Fat MRI

Bone marrow adipose tissue (BMAT) is a dynamic tissue which is associated with osteoporosis, bone metastasis, and primary bone tumors. The aim of this study is to determine region-specific variations and age- and gender-specific differences in BMAT and BMAT composition in healthy subjects. In this cross-sectional study, we included 40 healthy subjects (26 male: mean age 49 years, range 22-75 years; 14 female: mean age 50 years, range 29-71) and determined the bone marrow signal fat fraction and bone marrow unsaturation in the spine (C3-L5), pelvis, femora, and tibiae using chemical shift encoding-based water-fat imaging (WFI) with multiple gradient echoes (mGRE). Regions of interest covered the individual vertebral bodies, pelvis and proximal epimetaphysis, diaphysis, and distal epimetaphysis of the femur and tibia. The spinal fat fraction increased from cervical to lumbar vertebral bodies (mean fat fraction ( ± SD or (IQR): cervical spine 0.37 ± 0.1; thoracic spine 0.41 ± 0.08. lumbar spine 0.46 ± 0.01; p < 0.001). The femoral fat fraction increased from proximal to distal (proximal 0.78 ± 0.09; diaphysis 0.86 (0.15); distal 0.93 ± 0.02; p < 0.001), while within the tibia the fat fraction decreased from proximal to distal (proximal 0.92 ± 0.01; diaphysis 0.91 (0.02); distal 0.90 ± 0.01; p < 0.001). In female subjects, age was associated with fat fraction in the spine, pelvis, and proximal femur (ρ = 0.88 p < 0.001; ρ = 0.87 p < 0.001; ρ = 0.63 p = 0.02; ρ = 0.74 p = 0.002, respectively), while in male subjects age was only associated with spinal fat fraction (ρ = 0.40 p = 0.04). Fat fraction and unsaturation were negatively associated within the spine (r = -0.40 p = 0.01), while in the extremities fat fraction and unsaturation were positively associated (distal femur: r = 0.42 p = 0.01; proximal tibia: r = 0.47, p = 0.002; distal tibia: r = 0.35 p = 0.03), both independent of age and gender. In conclusion, we confirm the distinct, age- and gender-dependent, distribution of BMAT throughout the human skeleton and we show that, contradicting previous animal studies, bone marrow unsaturation in human subjects is highest within the axial skeleton compared to the appendicular skeleton. Furthermore, we show that BMAT unsaturation was negatively correlated with BMAT within the spine, while in the appendicular skeleton, BMAT and BMAT unsaturation were positively associated.

Associations of incidental vertebral fractures and longitudinal changes of MR-based proton density fat fraction and T2* measurements of vertebral bone marrow

BACKGROUND

Quantitative magnetic resonance imaging (MRI) techniques such as chemical shift encoding-based water-fat separation techniques (CSE-MRI) are increasingly applied as noninvasive biomarkers to assess the biochemical composition of vertebrae. This study aims to investigate the longitudinal change of proton density fat fraction (PDFF) and T2* derived from CSE-MRI of the thoracolumbar vertebral bone marrow in patients that develop incidental vertebral compression fractures (VCFs), and whether PDFF and T2* enable the prediction of an incidental VCF.

METHODS

In this study we included 48 patients with CT-derived bone mineral density (BMD) measurements at baseline. Patients that presented an incidental VCF at follow up (N=12, mean age 70.5 ± 7.4 years, 5 female) were compared to controls without incidental VCF at follow up (N=36, mean age 71.1 ± 8.6 years, 15 females). All patients underwent 3T MRI, containing a significant part of the thoracolumbar spine (Th11-L4), at baseline, 6-month and 12 month follow up, including a gradient echo sequence for chemical shift encoding-based water-fat separation, from which PDFF and T2* maps were obtained. Associations between changes in PDFF, T2* and BMD measurements over 12 months and the group (incidental VCF vs. no VCF) were assessed using multivariable regression models. Mixed-effect regression models were used to test if there is a difference in the rate of change in PDFF, T2* and BMD between patients with and without incidental VCF.

RESULTS

Prior to the occurrence of an incidental VCF, PDFF in vertebrae increased in the VCF group (Δ_PDFF=6.3 ± 3.1%) and was significantly higher than the change of PDFF in the group without VCF (Δ_PDFF=2.1 ± 2.5%, P=0.03). There was no significant change in T2* (Δ_T2*=1.7 ± 1.1ms vs. Δ_T2*=1.1 ± 1.3ms, P=0.31) and BMD (Δ_BMD=-1.2 ± 11.3mg/cm³ vs. Δ_BMD=-11.4 ± 24.1mg/cm³, P= 0.37) between the two groups over 12 months. At baseline, no significant differences were detected in the average PDFF, T2* and BMD of all measured vertebrae (Th11-L4) between the VCF group and the group without VCF (P=0.66, P=0.35 and P= 0.21, respectively). When assessing the differences in rates of change, there was a significant change in slope for PDFF (2.32 per 6 months, 95% confidence interval (CI) 0.31-4.32; P=0.03) but not for T2* (0.02 per 6 months, CI -0.98-0.95; P=0.90) or BMD (-4.84 per 6 months, CI -23.4-13.7; P=0.60).

CONCLUSIONS

In our study population, the average change of PDFF over 12 months is significantly higher in patients that develop incidental fractures at 12-month follow up compared to patients without incidental VCF, while T2* and BMD show no significant changes prior to the occurrence of the incidental vertebral fractures. Therefore, a longitudinal increase in bone marrow PDFF may be predictive for vertebral compression fractures.

Finite Element Analysis of Osteoporotic and Osteoblastic Vertebrae and Its Association With the Proton Density Fat Fraction From Chemical Shift Encoding-Based Water-Fat MRI - A Preliminary Study

PURPOSE

Osteoporosis is prevalent and entails alterations of vertebral bone and marrow. Yet, the spine is also a common site of metastatic spread. Parameters that can be non-invasively measured and could capture these alterations are the volumetric bone mineral density (vBMD), proton density fat fraction (PDFF) as an estimate of relative fat content, and failure displacement and load from finite element analysis (FEA) for assessment of bone strength. This study's purpose was to investigate if osteoporotic and osteoblastic metastatic changes in lumbar vertebrae can be differentiated based on the abovementioned parameters (vBMD, PDFF, and measures from FEA), and how these parameters correlate with each other.

MATERIALS AND METHODS

Seven patients (3 females, median age: 77.5 years) who received 3-Tesla magnetic resonance imaging (MRI) and multi-detector computed tomography (CT) of the lumbar spine and were diagnosed with either osteoporosis (4 patients) or diffuse osteoblastic metastases (3 patients) were included. Chemical shift encoding-based water-fat MRI (CSE-MRI) was used to extract the PDFF, while vBMD was extracted after automated vertebral body segmentation using CT. Segmentation masks were used for FEA-based failure displacement and failure load calculations. Failure displacement, failure load, and PDFF were compared between patients with osteoporotic vertebrae versus patients with osteoblastic metastases, considering non-fractured vertebrae (L1-L4). Associations between those parameters were assessed using Spearman correlation.

RESULTS

Median vBMD was 59.3 mg/cm³ in osteoporotic patients. Median PDFF was lower in the metastatic compared to the osteoporotic patients (11.9% vs. 43.8%, p=0.032). Median failure displacement and failure load were significantly higher in metastatic compared to osteoporotic patients (0.874 mm vs. 0.348 mm, 29,589 N vs. 3,095 N, p=0.034 each). A strong correlation was noted between PDFF and failure displacement (rho -0.679, p=0.094). A very strong correlation was noted between PDFF and failure load (rho -0.893, p=0.007).

CONCLUSION

PDFF as well as failure displacement and load allowed to distinguish osteoporotic from diffuse osteoblastic vertebrae. Our findings further show strong associations between PDFF and failure displacement and load, thus may indicate complimentary pathophysiological associations derived from two non-invasive techniques (CSE-MRI and CT) that inherently measure different properties of vertebral bone and marrow.

Voxel-based mapping of five MR biomarkers in the wrist bone marrow

OBJECTIVE

MRI is a reliable and accurate technique to characterize rheumatoid arthritis. The aim of this study was to provide voxel-by-voxel 3D maps of the proton density fat fraction (PDFF), the T₁ of water (T_1W), the T₁ of fat (T_1F), the T₂* of water (T₂*_W), the T₂* of fat (T₂*_F) in the wrist bone marrow.

MATERIALS AND METHODS

The experiments were conducted on 14 healthy volunteers (mean age: 24 ± 4). The data were acquired at 1.5 T using two optimized four-echo 3D 1.2 × 1.2 × 1.2 mm³-isotropic spoiled gradient sequences. A repeatability study was carried out. The measurements were done using a homemade parametric viewer software.

RESULTS

The inter-volunteer results were, on average: PDFF = 86 ± 3%, T_1W = 441 ± 113 ms, T_1F = 245 ± 19 ms, T₂*_W = 6 ± 1 ms and T₂*_F = 16 ± 3 ms. The coefficients of variation were for fat based biomarkers CV_PDFF < 5%, CV_T1F < 15% and CV_T2*F < 10% in the repeatability study.

DISCUSSION

The protocol and quantification tool proposed in this study provide high-resolution voxel-by-voxel 3D maps of five biomarkers in the wrist in less than 4 min of acquisition.

High contrast cartilaginous endplate imaging using a 3D adiabatic inversion-recovery-prepared fat-saturated ultrashort echo time (3D IR-FS-UTE) sequence

Ultrashort echo time (UTE) sequences can image tissues with transverse T ₂ /T ₂ * relaxations too short to be efficiently observed on routine clinical MRI sequences, such as the vertebral body cartilaginous endplate (CEP). Here, we describe a 3D adiabatic inversion-recovery-prepared fat-saturated ultrashort echo time (3D IR-FS-UTE) sequence to highlight the CEP of vertebral bodies in comparison to the intervertebral disc (IVD) and bone marrow fat (BF) at 3 T. The IR-FS-UTE sequence used a 3D UTE sequence combined with an adiabatic IR preparation pulse centered in the middle of the water and fat peaks, while a fat saturation module was used to suppress the signal from fat. A slab-selective half pulse was used for signal excitation, and a 3D center-out cones trajectory was used for more efficient data sampling. The 3D IR-FS-UTE sequence was applied to an ex vivo human spine sample, as well as the spines of six healthy volunteers and of three patients with back pain. Bright continuous lines representing signal from CEP were found in healthy IVDs. The measured contrast-to-noise ratio was 18.5 ± 4.9 between the CEP and BF, and 20.3 ± 4.15 between the CEP and IVD for the six volunteers. Abnormal IVDs showed CEP discontinuity or irregularity in the sample and patient studies. In conclusion, the proposed 3D IR-FS-UTE sequence is feasible for imaging the vertebral body's CEP in vivo with high contrast.

Preliminary quantitative analysis of vertebral microenvironment changes in type 2 diabetes mellitus using FOCUS IVIM-DWI and IDEAL-IQ sequences

PURPOSE

To explore the application of intravoxel incoherent motion diffusion-weighted imaging(IVIM-DWI) on account of field-of-view optimized and constrained undistorted single shot (FOCUS) and iteraterative decomposition of water and fat with echo asymmetry and least-squares estimation quantitation(IDEAL-IQ) sequences in evaluating the vertebral microenvironment changes of type 2 diabetes mellitus(T2DM) patients and the correlation with bone mineral density(BMD).

METHOD

128 T2DM patients (mean age 63.4 ± 5.28 years) underwent both dual-energy X-ray absorptiometry (DEXA) and spine MRI. The FOCUS IVIM-DWI and IDEAL-IQ derived parameters of the vertebral body(L1, L2, L3, L4)were measured on corresponding maps of the lumbar spine. The subjects were divided into 3 groups according to T-scores as follows: normal (n = 37), osteopenia (n = 43), and osteoporosis(n = 48) group.One-way analysis of variance (ANOVA) were used to compare the vertebral parameters(ADC_slow, ADC_fast, f, FF, R2*) among three BMD cohorts.Receiver operating characteristic (ROC) analyses and Spearman's rank correlation were performed to test the diagnostic performance and the correlation between them respectively.

RESULTS

There were significant differences in vertebral ADC_slow, ADC_fast, FF and R2* between the three groups (P < 0.05).Statistically, BMD was moderately negatively correlated with FF (r = -0.584, P < 0.001) and weakly positively with ADC_slow (r = 0.334, P < 0.001), meanwhile moderately positively correlated with R2*(r = 0.509, P < 0.001) and ADC_fast(0.545, P < 0.001).ADC_fast was moderately negatively correlated with FF (r = -0.417, P < 0.001), weakly positively correlated with R2*(0.359, P < 0.001).Compared with the area under the curve (AUC) of ADC_slow, ADC_fast, FF and R2*, the AUC of ADC_fast was higher in identifying between normal and abnormal(osteopenia and osteoporosis), normal from osteopenia, while the AUC of FF was higher in identifying osteopenia from osteoporosis.

CONCLUSIONS

FOCUS IVIM-DWI and IDEAL-IQ of lumbar spine might be useful to evaluate the vertebral microenvironment changes of T2DM patients.

Vertebral bone marrow T2* mapping using chemical shift encoding-based water-fat separation in the quantitative analysis of lumbar osteoporosis and osteoporotic fractures

BACKGROUND

Chemical shift encoding-based water-fat separation techniques have been used for fat quantification [proton density fat fraction (PDFF)], but they also enable the assessment of bone marrow T2*, which has previously been reported to be a potential biomarker for osteoporosis and may give insight into the cause of vertebral fractures (i.e., osteoporotic vs. traumatic) and the microstructure of the bone when applied to vertebral bone marrow.

METHODS

The 32 patients (78.1% with low-energy osteopenic/osteoporotic fractures, mean age 72.3±9.8 years, 76% women; 21.9% with high-energy traumatic fractures, 47.3±12.8 years, no women) were frequency-matched for age and sex to subjects without vertebral fractures (n=20). All study patients underwent 3T-MRI of the lumbar spine including sagittally acquired spoiled gradient echo sequences for chemical shift encoding-based water-fat separation, from which T2* values were obtained. Volumetric trabecular bone mineral density (BMD) and trabecular bone parameters describing the three-dimensional structural integrity of trabecular bone were derived from quantitative CT. Associations between T2* measurements, fracture status and trabecular bone parameters were assessed using multivariable linear regression models.

RESULTS

Mean T2* values of non fractured vertebrae in all patients showed a significant correlation with BMD (r=-0.65, P<0.001), trabecular number (TbN) (r=-0.56, P<0.001) and trabecular spacing (TbSp) (r=0.61, P<0.001); patients with low-energy osteoporotic vertebral fractures showed significantly higher mean T2* values than those with traumatic fractures (13.6±4.3 vs. 8.4±2.2 ms, P=0.01) as well as a significantly lower TbN (0.69±0.08 vs. 0.93±0.03 mm-1, P<0.01) and a significantly larger trabecular spacing (1.06±0.16 vs. 0.56±0.08 mm, P<0.01). Mean T2* values of osteoporotic patients with and without vertebral fracture showed no significant difference (13.5±3.4 vs. 15.6±3.5 ms, P=0.40). When comparing the mean T2* of the fractured vertebrae, no significant difference could be detected between low-energy osteoporotic fractures and high-energy traumatic fractures (12.6±5.4 vs. 8.1±2.4 ms, P=0.10).

CONCLUSIONS

T2* mapping of vertebral bone marrow using using chemical shift encoding-based water-fat separation allows for assessing osteoporosis as well as the trabecular microstructure and enables a radiation-free differentiation between patients with low-energy osteoporotic and high-energy traumatic vertebral fractures, suggesting its potential as a biomarker for bone fragility.

High-contrast osteochondral junction imaging using a 3D dual adiabatic inversion recovery-prepared ultrashort echo time cones sequence

While conventional MRI sequences cannot visualize tissues from the osteochondral junction (OCJ) due to these tissues' short transverse T₂ /T₂ * relaxations, ultrashort echo time (UTE) sequences can overcome this limitation. A 2D UTE sequence with a dual adiabatic inversion recovery preparation (DIR-UTE) for selective imaging of short T₂ tissues with high contrast has previously been developed, but high sensitivity to eddy currents and aliased out-of-slice excitation make it difficult to image the thin layer of the OCJ in vivo. Here, we combine the DIR scheme with a 3D UTE cones sequence for volumetric imaging of OCJ tissues in vivo, aiming to generate higher OCJ contrast compared with a recently developed single IR-prepared UTE sequence with a fat saturation module (IR-FS-UTE). All sequences were implemented on a 3-T clinical scanner. The DIR-UTE cones sequence combined a 3D UTE cones sequence with two narrow-band adiabatic IR preparation pulses centered on water and fat spectrum frequencies, respectively. The 3D DIR-UTE cones sequence was first applied to a phantom, then to the knees of four healthy volunteers and four patients diagnosed with osteoarthritis and compared with the IR-FS-UTE sequence. In both phantom and volunteer studies, the proposed DIR-UTE cones sequence showed much higher contrast for OCJ imaging than the IR-FS-UTE sequence did. The 3D DIR-UTE cones sequence showed a significantly higher contrast-to-noise ratio between the OCJ and subchondral bone fat (mean, standard deviation [SD]: 25.7 ± 2.3) and between the OCJ and superficial layers of cartilage (mean, SD: 22.2 ± 3.5) compared with the IR-FS-UTE sequence (mean, SD: 10.8 ± 2.5 and 16.3 ± 2.6, respectively). The 3D DIR-UTE cones sequence is feasible for imaging of the OCJ region of the knee in vivo and produces both high resolution and high contrast.

Clinical imaging of marrow adiposity

Research examining bone marrow adipose tissue (BMAT) has rapidly expanded during the last two decades, leading to advances in knowledge on the role of BMAT in the pathogenesis of bone loss and endocrine disorders. Clinical imaging has played a crucial role for the in vivo assessment of BMAT, allowing non-invasive quantification and evaluation of BMAT composition. In the present work, we review different imaging methods for assessing properties of BMAT. Our aim is to review conventional magnetic resonance imaging (MRI), water-fat imaging, and single-voxel proton magnetic resonance spectroscopy (¹H-MRS), as well as computed tomography (CT)-based techniques, including single energy and dual energy CT. We will also discuss the clinical applications of these methods in type 2 diabetes mellitus, obesity and anorexia nervosa.

Quantifying Bone Marrow Fat Fraction and Iron by MRI for Distinguishing Aplastic Anemia from Myelodysplastic Syndromes

Background

Bone marrow of patients with aplastic anemia (AA) is different from that of patients with myelodysplastic syndrome (MDS) and is difficult to identify by blood examination. IDEAL‐IQ (iterative decomposition of water and fat with echo asymmetry and least‐squares estimation) imaging might be able to quantify fat fraction (FF) and iron content in bone tissues.

Purpose

To determine if IDEAL‐IQ measurements of bone marrow FF and iron content can distinguish between patients with AA and MDS.

Study Type

Retrospective.

Population

Fifty‐seven patients with AA, 21 patients with MDS, and 24 healthy controls.

Field Strength/Sequence

3.0 T, IDEAL‐IQ sequence.

Assessment

Three independent observers evaluated the IDEAL‐IQ images and measured FF and R2* in the left posterior superior iliac spine.

Statistical Tests

Kruskal–Wallis test, linear correlations, and Bland–Altman analysis were used. A P‐value of <0.05 was considered statistically significant.

Results

The FF in patients with AA (79.46% ± 15.00%) was significantly higher than that in patients with MDS (42.78% ± 30.09%) and control subjects (65.50% ± 14.73%). However, there was no significant difference in FF between control subjects and patients with MDS (P = 0.439). The R2* value of AA, MDS, and controls was 145.38 ± 53.33, (171.13 ± 100.89, and 135.99 ± 32.41/second, respectively, with no significant difference between the three groups (P = 0.553).

Data Conclusion

Quantitative IDEAL‐IQ magnetic resonance imaging may facilitate the diagnosis of AA and distinguish it from MDS.

Level of Evidence

3

Technical Efficacy Stage

2

Adding marrow R2∗ to proton density fat fraction improves the discrimination of osteopenia and osteoporosis in postmenopausal women assessed with 3D FACT sequence

OBJECTIVE

To evaluate the role of three-dimensional Fat Analysis & Calculation Technique sequence in improving the diagnostic accuracy for the detection of osteopenia and osteoporosis by simultaneous quantification of proton density fat fraction (PDFF) and fat-corrected R2∗.

METHODS

Fat Analysis & Calculation Technique imaging of lumbar spine was obtained in 99 postmenopausal women including 52 normal bone mass, 29 osteopenia, and 18 osteoporosis. The diagnostic performance of PDFF and R2∗ in the differentiation of different bone-density groups was evaluated with the receiver operating characteristic curve.

RESULTS

The reproducibility of PDFF and R2∗ measures was satisfactory with the root mean square coefficient of variation, 2.16% and 2.70%, respectively. The intra- and interobserver agreements for the PDFF and R2∗ were excellent with the intraclass correlation coefficient > 0.9 for all. There were significant differences in PDFF and R2∗ among the three groups (P < 0.05). Bone density had a moderate inverse correlation with PDFF (r  = -0.659) but a positive association with R2∗ (r = 0.508, P < 0.001). Adjusted for age, years since menopause and body mass index, odds ratios (95% confidence interval) for osteopenia and osteoporosis per standard deviation higher marrow PDFF and R2∗ were 2.9 (1.4-5.8) and 0.4 (0.2-0.8), respectively. The areas under the curve were 0.821 for PDFF, 0.784 for R2∗, and 0.922 for both combined for the detection of osteoporosis (P < 0.05). Similar results were obtained in distinguishing osteopenia from healthy controls.

CONCLUSIONS

Simultaneous estimation of marrow R2∗ and PDFF improves the discrimination of osteopenia and osteoporosis in comparison with the PDFF or R2∗ alone.

Magnetic resonance biomarkers in radiation oncology: The report of AAPM Task Group 294

A magnetic resonance (MR) biologic marker (biomarker) is a measurable quantitative characteristic that is an indicator of normal biological and pathogenetic processes or a response to therapeutic intervention derived from the MR imaging process. There is significant potential for MR biomarkers to facilitate personalized approaches to cancer care through more precise disease targeting by quantifying normal versus pathologic tissue function as well as toxicity to both radiation and chemotherapy. Both of which have the potential to increase the therapeutic ratio and provide earlier, more accurate monitoring of treatment response. The ongoing integration of MR into routine clinical radiation therapy (RT) planning and the development of MR guided radiation therapy systems is providing new opportunities for MR biomarkers to personalize and improve clinical outcomes. Their appropriate use, however, must be based on knowledge of the physical origin of the biomarker signal, the relationship to the underlying biological processes, and their strengths and limitations. The purpose of this report is to provide an educational resource describing MR biomarkers, the techniques used to quantify them, their strengths and weakness within the context of their application to radiation oncology so as to ensure their appropriate use and application within this field.

Proton density fat fraction of the spinal column: an MRI cadaver study

BACKGROUND

The increased popularity of minimally invasive spinal surgery calls for a revision of guidance techniques to prevent injuries of nearby neural and vascular structures. Lipid content has previously been proposed as a distinguishing criterion for different bone tissues to provide guidance along the interface of cancellous and cortical bone. This study aims to investigate how fat is distributed throughout the spinal column to confirm or refute the suitability of lipid content for guidance purposes.

RESULTS

Proton density fat fraction (PDFF) was assessed over all vertebral levels for six human cadavers between 53 and 92 years of age, based on fat and water MR images. According to their distance to the vertebra contour, the data points were grouped in five regions of interest (ROIs): cortical bone (-1 mm to 0 mm), pre-cortical zone (PCZ) 1-3 (0-1 mm; 1-2 mm; 2-3 mm), and cancellous bone ([Formula: see text] 3 mm). For PCZ1 vs. PCZ2, a significant difference in mean PDFF of between -7.59 pp and -4.39 pp on average was found. For cortical bone vs. PCZ1, a significant difference in mean PDFF of between -27.09 pp and -18.96 pp on average was found.

CONCLUSION

A relationship between distance from the cortical bone boundary and lipid content could be established, paving the way for guidance techniques based on fat fraction detection for spinal surgery.

Differentiation of Vertebral Metastases From Focal Hematopoietic Marrow Depositions on MRI: Added Value of Proton Density Fat Fraction

OBJECTIVE. The purpose of this study was to evaluate the added value of proton density fat fraction (PDFF) in differentiating vertebral metastases from focal hematopoietic marrow depositions. MATERIALS AND METHODS. The study included 44 patients with 30 vertebral metastases and 14 focal hematopoietic marrow depositions who underwent spinal MRI. The final diagnoses were based on histologic confirmation, follow-up MRI, or PET/CT. Two musculoskeletal radiologists with 1 and 15 years of experience independently interpreted both image sets (i.e., images from conventional MRI alone versus images from conventional MRI and PDFF combined). Using a 5-point scale, the readers scored their confidence in the malignancy of the vertebral lesions. The diagnostic performance (AUC) of the two image sets was assessed via ROC curve analyses. Sensitivities, specificities, and accuracies (for both image sets) were compared using the McNemar test. Kappa coefficients were calculated to assess interobserver agreement. RESULTS. Both readers showed improved diagnostic performance after PDFF was added (AUC, 0.840-0.912 and 0.805-0.895 for readers 1 and 2, respectively). However, adding PDFF did not significantly improve the sensitivity and specificity of either reader (p > .05). Interobserver agreement significantly improved from moderate (κ = 0.563) to excellent (κ = 0.947) after PDFF was added. CONCLUSION. The addition of PDFF to a conventional MRI protocol improved the diagnostic performance for differentiating vertebral metastases from focal hematopoietic marrow depositions but without resulting in significant improvement in sensitivity and specificity.

Quantitative magnetic resonance imaging for determining bone marrow fat fraction at 1.5 T and 3.0 T: a technique to noninvasively assess cellularity and potential malignancy of the bone marrow

BACKGROUND

Pediatric bone marrow assessment by MRI is challenging and primarily experiential and qualitative, with a paucity of clinically useful quantitative imaging techniques.

OBJECTIVE

MRI fat fraction (MRI-FF) is a technique used to quantify the degree of fat in other organ systems. The purpose of this study was to assess whether MRI-FF accurately measures bone marrow composition.

MATERIALS AND METHODS

This two-part study included a validation phase, followed by an application phase. For the validation phase, the MRI-FF of piglet bones (6 long bones, 8 axial bones) was performed at 1.5 tesla (T) and 3.0 T, and correlated to the histological fat fraction (H-FF). We used Bland-Altman plots to compare MRI-FF at 1.5 tesla T and 3.0 T. For the application phase, five children with malignant marrow disease were recruited along with seven age- and gender-matched control subjects. The MRI-FF in the children was correlated to the H-FF. Boxplots were used to compare the MRI-FF of patients and control subjects.

RESULTS

For the validation animal study, the MRI-FF of piglet bones at both 1.5 T and 3.0 T demonstrated moderate positive correlation to H-FF (r=0.41 and 0.42, respectively). MRI-FF at 1.5 T and 3.0 T were in good agreement, on average 7.7% apart. For the application phase, we included 5 children (4 with leukemia, 1 rhabdomyosarcoma) with median age 7 years, range (3-10 years). All children had MRI-FF and H-FF below 10%. The MRI-FF in patients (3.8±1.2) was significantly lower than that of control subjects (46.1±12.3%) (P<0.01).

CONCLUSION

MRI-FF is a valid technique to assess bone marrow fat fraction at both 1.5 T and 3.0 T. The MRI-FF in children with malignant marrow processes is significantly lower than in control subjects with normal marrow.