Fat fraction estimation of morphologically normal lumbar vertebrae using the two-point mDixon turbo spin-echo MRI with flexible echo times and multipeak spectral model of fat: Comparison between cancer and non-cancer patients

Efficacy of fat quantification methods used in MRI to distinguish between normal, benign, and malignant bone marrow pathologies in children

BACKGROUND

Fat quantification methods in magnetic resonance imaging (MRI) have been studied to differentiate bone marrow pathologies in adult patients; however, scarce literature is available in pediatric patients.

PURPOSE

To evaluate the efficacy of the T1 signal intensity value (T1-SIV), out-of-phase/in-phase signal ratio (OP/IP SR), and fat fraction (FF) to differentiate between normal, benign, and malignant pathological processes.

MATERIAL AND METHODS

A total of 48 pediatric patients with lumbar and pelvic MRI were classified into three groups according to bone marrow pathology (group 1, normal; group 2, benign pathology/reconversion; group 3, malignant). The efficacy of T1-SIV, OP/IP SR, and FF values in differentiating these pathologies was evaluated using Kruskal-Wallis or analysis of variance and followed by Bonferroni or Dunn-Bonferroni tests. Cutoff values for malignant infiltration were defined using ROC analysis.

RESULTS

Although these values were significantly different in all three groups (P = 0.001-0.008), this difference was not sufficient to discriminate between all groups. Subgroup analyses showed significant differences in T1-SIV between groups 1-3, in OP/IP SR between groups 1-3, 2-3, and 1-2, in FF between groups 1-2 and 1-3 in various regions (P = 0.001-0.049). Cutoff values had a sensitivity and specificity of 90%-100% for OP/IP SR and FF.

CONCLUSION

T1-SIV, OP/IP SR, and FF may potentially distinguish normal from pathological bone marrow. OP/IP SR and FF values detected malignant infiltration with high sensitivity and specificity in this study. However, only OP/IP SR may significantly differentiate benign and malignant bone marrow pathologies which needs to be confirmed in the future study with a larger patient population.

Water Fraction Ratio of the Sacroiliac Joint Subchondral Bone Marrow in Patients with Ankylosing Spondylitis Predicts the Degree of Disease Activity

Objectives: Ankylosing spondylitis (AS) is a chronic inflammatory arthritis with characteristic involvement of the spine and sacroiliac joints. MRI may be the only indicator of disease activity or response. This study aimed to use a novel water fraction measurement technique on MRI as a biomarker to predict disease activity in patients with AS. Methods: We enrolled 39 patients (18 men [mean age, 38.6 years; range, 18−59 years] and 21 women [mean age, 39.3 years; range, 23−61 years]) who were clinically diagnosed with AS and underwent MRI, including mDixon sequences. Water fraction values of sacroiliac joint subchondral bone marrow were derived from the mDixon sequences. The Ankylosing Spondylitis Disease Activity Score (ASDAS) was recorded using clinical information and laboratory values from medical records. Multiple linear regression, Firth logistic regression, and intraclass correlation coefficients were used for the statistical analysis. Results: In multiple linear regression, water fraction, subchondral bone marrow edema, subchondral bone erosion, and subchondral bone marrow enhancements were significantly associated with ASDAS with C-reactive protein (ASDAS-CRP). The water fraction parameters showed a good linear correlation with ASDAS-CRP and ASDAS with erythrocyte sedimentation rate (ASDAS-ESR) (beta coefficient = 1.98, p < 0.001 and beta coefficient = 1.60, p = 0.003). Firth logistic regression showed that water fraction was a significant predictor of ASDAS-CRP but not ASDAS-ESR. The intraclass correlation coefficient showed excellent repeatability for the three repeated measures of the water fraction. Conclusion: Water fraction parameter could be a good imaging biomarker of disease activity status. The sacroiliac joint evaluated by mDixon MRI may be a promising biomarker of disease progression in patients with spondyloarthritis.

Fat fraction quantification of lumbar spine: comparison of T1-weighted two-point Dixon and single-voxel magnetic resonance spectroscopy in diagnosis of multiple myeloma

PURPOSE

We aimed to investigate the value of T1-weighted two-point Dixon technique and single-voxel magnetic resonance spectroscopy (MRS) in diagnosis of multiple myeloma (MM) through quantifying fat content of vertebral marrow.

METHODS

A total of 30 MM patients and 30 healthy volunteers underwent T1-weighted two-point Dixon and single-voxel MRS imaging. The fat fraction map (FFM) was reconstructed from the Dixon images using the equation FFM = Lip/In, where Lip represents fat maps and In represents in-phase images. The fat fraction (FF) of MRS was calculated by using the integral area of Lip peak divided by the sum of integral area of Lip peak and water peak.

RESULTS

FF values measured by the Dixon technique and MRS were significantly decreased in MM patients (45.99%±3.39% and 47.63%±4.38%) compared with healthy controls (64.43%±0.96% and 76.22%±1.91%) (P < 0.001 with both methods). FF values measured by Dixon technique were significantly positively correlated to those measured by MRS in MM (r = 0.837, P < 0.001) and healthy control group (r = 0.735, P < 0.001), respectively. There was no significant difference between area under the curve (AUC) obtained by the Dixon technique (0.878±0.047; range, 0.785 to 0.971; optimal cutoff, 56.35 for healthy controls vs. MM) and MRS (0.883±0.047; range, 0.791 to 0.974; optimal cutoff, 61.00 for healthy controls vs. MM). The ability of Dixon technique to differentiate MM group from healthy controls was equivalent to single-voxel MRS.

CONCLUSION

Regarding detection of fat contents in vertebral bone, T1-weighted two-point Dixon technique exhibited equivalent performance to single-voxel MRS in the diagnosis of multiple myeloma. Moreover, two-point Dixon is a more convenient and stable technique for assessing bone marrow changes in MM patients than single-voxel MRS.

Differentiation between benign and malignant vertebral compression fractures using qualitative and quantitative analysis of a single fast spin echo T2-weighted Dixon sequence

Objectives

To determine and compare the qualitative and quantitative diagnostic performance of a single sagittal fast spin echo (FSE) T2-weighted Dixon sequence in differentiating benign and malignant vertebral compression fractures (VCF), using multiple readers and different quantitative methods.

Methods

From July 2014 to June 2020, 95 consecutive patients with spine MRI performed prior to cementoplasty for acute VCFs were retrospectively included. VCFs were categorized as benign (n = 63, mean age = 76 ± 12 years) or malignant (n = 32, mean age = 63 ± 12 years) with a best valuable comparator as a reference. Qualitative analysis was independently performed by four radiologists by categorizing each VCF as either benign or malignant using only the image sets provided by FSE T2-weighted Dixon sequences. Quantitative analysis was performed using two different regions of interest (ROI1-2) and three methods (signal drop, fat fraction (FF) from ROIs, FF maps). Diagnostic performance was compared using ROC curves analyses. Interobserver agreement was assessed using kappa statistics and intraclass correlation coefficients (ICC).

Results

The qualitative diagnostic performance ranged from area under the curve (AUC) = 0.97 (95% CI: 0.91–1.00) to AUC = 0.99 (95% CI: 0.95–1.0). The quantitative diagnostic performance ranged from AUC = 0.82 (95% CI: 0.73–0.89) to AUC = 0.97 (95% CI: 0.91–0.99). Pairwise comparisons showed no statistical difference in diagnostic performance (all p > 0.0013, Bonferroni-corrected p < 0.0011). All five cases with disagreement among the readers were correctly diagnosed at quantitative analysis using ROI2. Interobserver agreement was excellent for both qualitative and quantitative analyses.

Conclusions

A single FSE T2-weighted Dixon sequence can be used to differentiate benign and malignant VCF with high diagnostic performance using both qualitative and quantitative analyses, which can provide complementary information.

Key Points

• Qualitative analysis of a single FSE T2-weighted Dixon sequence yields high diagnostic performance and excellent observer agreement for differentiating benign and malignant compression fractures.

• The same FSE T2-weighted Dixon sequence allows quantitative assessment with high diagnostic performance.

• Quantitative data can readily be extracted from the FSE T2-weighted Dixon sequence and may provide complementary information to the qualitative analysis, which may be useful in doubtful cases.

T2-weighted Dixon MRI of the spine: A feasibility study of quantitative vertebral bone marrow analysis

PURPOSE

To compare the measurements of fat fraction (FF) and in-phase vs. opposed-phase ratio between two-dimensional T2-weighted (T2W) spin-echo (SE) Dixon and three-dimensional (3D) T1-weighted (T1W) volume interpolated breath-hold examination (VIBE) Dixon sequences in malignant vertebral lesions and normal vertebral bone marrow.

MATERIALS AND METHODS

Thirty patients with focal vertebral malignancies (20 men, mean age, 67.3±9.4 [SD] years; age range: 41-84 years) and 30 patients without malignant spinal disease (11 men, mean age, 70.1±12.9 [SD]; age range: 53-93 years) were retrospectively included. Each patient underwent spine MRI at 1.5 Tesla including T2W SE and T1W VIBE 2-point Dixon sequences. Two readers independently performed 3D-volume of interest (VOI) and region of interest (ROI)-based FF and IO-ratio measurements of malignant lesions and normal vertebrae. Student t-test, Pearson correlation (r) test and two-way mixed model intraclass correlation coefficients (ICC) were used to compare measurements.

RESULTS

T2W SE and T1W VIBE mean FF and IO-ratio were significantly smaller in malignancy compared to normal marrow, but there were significant differences of paired measurement mean values between T2W SE and T1W VIBE Dixon parameters in malignant lesions T2W SE VOI FF=9%, T2W SE ROI FF=7%, T2W SE IO-ratio=4% vs. T1W VIBE VOI FF=11%, T1W VIBE ROI FF=9%, T1W VIBE IO-ratio=-2%, and in normal vertebrae T2W SE VOI FF=74%, T2W SE ROI FF=77%, T2W SE IO-ratio=51% vs. T1W VIBE VOI FF=67%, T1W VIBE ROI FF=73%, T1W VIBE IO-ratio=58% (each P comparing the paired T2W TSE and T1W VIBE parameter, respectively<0.001). There was excellent positive correlation between T2W SE and T1W VIBE-FF (r≥0.99) and VOI and ROI FF measurements for each sequence (r≥0.99). Inter-reader agreement was excellent for all measurements (ICC≥0.94 for all).

CONCLUSION

Calculation of T2W SE Dixon derived FF is feasible and gave valid results that help discriminate between malignant vertebral lesions and normal vertebral bone marrow.

The Utility of Modified Dixon Turbo Spin Echo Shoulder Magnetic Resonance Arthrography in Assessing Rotator Cuff Disorder and Evaluating the Rotator Cuff Muscles

RATIONALE AND OBJECTIVES

To compare the diagnostic ability of modified Dixon (mDixon) turbo spin echo (TSE) T1-weighted (T1W) shoulder magnetic resonance arthrography (MRA) with that of conventional shoulder MRA, and evaluate the feasibility of mDixon TSE in-phase (IP) images in measuring the fat fraction and size of rotator cuff muscles.

MATERIALS AND METHODS

This retrospective study included 57 patients who underwent 3T shoulder MRA examinations with conventional and mDixon TSE T1W images (mean age: 56.7 years; range: 20-78 years). Two musculoskeletal radiologists independently evaluated the rotator cuff tendons with fat saturated T1W images and mDixon TSE T1W water images. Occupation ratios measured on T1W and mDixon TSE T1W IP images were compared. The fat fraction of the supraspinatus from the mDixon TSE T1W images was calculated and correlated with fatty infiltration of the supraspinatus on T1W images.

RESULTS

For tendon pathology, the kappa value for inter-sequence and inter-reader agreement was 0.957 (95% confidence interval [CI]: 0.923-0.990) and 0.839 (95% CI: 0.778-0.899), respectively. For retear, the kappa value for inter-sequence and inter-reader agreement was 0.913 (95% CI: 0.796-1.000) and 0.779 (95% CI: 0.594-0.963), respectively. The intraclass correlation coefficient for both occupation ratios was 0.986 (95% CI: 0.973-0.993). Comparison of mDixon TSE T1W fat fraction with Goutallier grade showed a strong positive linear correlation (r = 0.929).

CONCLUSIONS

The mDixon TSE T1W sequence is a good alternative to conventional sequences in shoulder MRA for evaluating rotator cuff pathology. Furthermore, this sequence provides information on the size and fat infiltration of rotator cuff muscles.

Dixon or DWI - Comparing the utility of fat fraction and apparent diffusion coefficient to distinguish between malignant and acute osteoporotic vertebral fractures

PURPOSE

To compare fat fraction (FF) and apparent diffusion coefficient (ADC) as discriminators distinguishing malignant from acute/subacute osteoporotic vertebral fractures.

METHOD

1.5 T MRIs of 42 malignant and 27 acute/subacute osteoporotic vertebral fractures (38 patients) were retrospectively reviewed. Two readers independently classified fractures as malignant or osteoporotic based on conventional imaging morphology. Diagnostic reader confidence was rated as confident or not confident. FF was derived from axial T1 gradient-echo 2-point Dixon MRI. ADC maps were calculated from axial b50 and b900 images. Both readers independently performed ROI measurements of mean FF and ADC of the same fractured vertebrae. FF and ADC values, corresponding ROC curves and optimized cut-off value performance were compared. Inter-reader agreement was analysed by calculation of intraclass correlation coefficients (ICCs). A p-value < 0.05 was deemed significant.

RESULTS

Mean FF and ADC were significantly lower in malignant (9.5 % and 1.05 × 10^-3 mm²/s) compared to osteoporotic fractures (32 % and 1.34 × 10^-3 mm²/s, all p < 0.001). The optimal cut-off FF was 11.5 %, detecting malignant fractures with 86 %/89 % sensitivity/specificity. The optimal ADC cut-off of 1.04 × 10^-3 mm/s² yielded 62 %/96 % sensitivity/specificity. FF AUC (0.93) was significantly larger than ADC AUC (0.82, p = 0.03). In the subgroup of nine cases reported with low expert reader confidence, the optimized cut-off specificities of FF (83 %) and ADC (83 %) exceeded reader specificity (50 %). There was excellent inter-reader agreement for mean FF (ICC = 0.99) and good agreement for mean ADC (ICC = 0.86) measurements.

CONCLUSION

FF and ADC can improve reader specificity to distinguish between malignant and acute or subacute osteoporotic vertebral fractures. As single discriminator, FF was superior to ADC.

Advanced MR imaging of bone marrow: quantification of signal alterations on T1-weighted Dixon and T2-weighted Dixon sequences in red marrow, yellow marrow, and pathologic marrow lesions

OBJECTIVES

To quantify and compare signal intensity (SI) changes on T1-weighted (W) and T2W Dixon imaging in yellow marrow, red marrow, and bone marrow lesions.

MATERIALS AND METHODS

A total of 141 patients (77 controls, 64 lesions-33 benign, 31 malignant) between January 2016 and December 2017 were retrospectively identified. For the control group, fixed 2-cm² region of interests (ROI) were drawn at L5, bilateral ilium and femurs on in-phase and opposed-phase T1W and T2W Dixon images. For the lesion group, ROIs of best fit were drawn around each lesion on in-phase and opposed-phase T2W Dixon images. SI changes between in-phase and opposed phase maps for each group were compared. Inter-reader analysis was performed.

RESULTS

Yellow marrow exhibited smaller SI changes as compared to red marrow on both T1W and T2W Dixon imaging at all locations (p < 0.0001) except at L5 on T2W Dixon imaging (p = 0.206). Both benign and malignant lesions showed significantly smaller SI changes as compared to both yellow (p = 0.0087, p < 0.0001) and red marrow (p = 0.0004, p < 0.0001) on T2W Dixon imaging. Malignant lesions exhibited smaller SI change as compared to benign lesions on T2W Dixon imaging (p = 0.0005). Signal intensity loss on both red and yellow marrow were smaller on T1W Dixon as compared to T2W Dixon (0.49-0.64, 0.27-0.31 vs. 0.70-0.74, 0.48-0.71). Inter-reader agreements were excellent (0.91-0.97).

CONCLUSIONS

SI change calculated from T2-weighted Dixon imaging can adequately differentiate between yellow marrow, red marrow, and osseous lesions, both benign and malignant.

Reliability of measuring the fat content of the lumbar vertebral marrow and paraspinal muscles using MRI mDIXON-Quant sequence

PURPOSE

We aimed to assess the reliability of measuring the fat content of the lumbar vertebral marrow and the paraspinal muscles using magnetic resonance imaging (MRI) mDIXON-Quant sequence.

METHODS

Thirty-one healthy volunteers were included. All participants underwent liver mDIXON-Quant imaging on a 3.0 T Philips MRI scanner by observer A. Within two weeks, observer B repeated the scan. After the examination, each observer independently measured the fat content of the third lumbar vertebra (L3), and the psoas (PS), erector spinae (ES), and multifidus (MF) muscles on central L3 axial images. After two weeks, each observer repeated the same measurements. They were blinded to their previous results. Reliability was estimated by evaluating the repeatability and reproducibility.

RESULTS

The repeatability of the fat content measurements of L3, PS, ES, and MF was high. The intraclass correlation coefficients of the fat content of L3, PS, ES, and MF were 0.997, 0.984, 0.997, and 0.995 for observer A and 0.948, 0.974, 0.963, and 0.995 for observer B, respectively. The reproducibility of the measurement of the fat content of L3, PS, ES, and MF was high, and the interclass correlation coefficients were 0.984, 0.981, 0.977, and 0.998, respectively.

CONCLUSION

Using mDIXON-Quant imaging to measure the fat content of the lumbar vertebral marrow and paraspinal muscles shows high reliability and is suitable for use in clinical practice.

Quantitative Whole-Body Diffusion-Weighted MR Imaging

Whole-body diffusion-weighted MRI has emerged as a powerful diagnostic tool for disease detection and staging mainly used in systemic bone disease. The large field-of-view functional imaging technique highlights cellular tumor and suppresses normal tissue signal, allowing quantification of an estimate of total disease burden, summarized as the total diffusion volume (tDV), as well as global apparent diffusion coefficient (gADC) measurements. Both tDV and gADC have been shown to be repeatable quantitative parameters that indicate tumor heterogeneity and treatment effects, thus potential, noninvasive, imaging biomarkers informing on disease prognosis and therapy response.

Fat fraction mapping using magnetic resonance imaging: insight into pathophysiology

Adipose cells have traditionally been viewed as a simple, passive energy storage depot for triglycerides. However, in recent years it has become clear that adipose cells are highly physiologically active and have a multitude of endocrine, metabolic, haematological and immune functions. Changes in the number or size of adipose cells may be directly implicated in disease (e.g. in the metabolic syndrome), but may also be linked to other pathological processes such as inflammation, malignant infiltration or infarction. MRI is ideally suited to the quantification of fat, since most of the acquired signal comes from water and fat protons. Fat fraction (FF, the proportion of the acquired signal derived from fat protons) has, therefore, emerged as an objective, image-based biomarker of disease. Methods for FF quantification are becoming increasingly available in both research and clinical settings, but these methods vary depending on the scanner, manufacturer, imaging sequence and reconstruction software being used. Careful selection of the imaging method-and correct interpretation-can improve the accuracy of FF measurements, minimize potential confounding factors and maximize clinical utility. Here, we review methods for fat quantification and their strengths and weaknesses, before considering how they can be tailored to specific applications, particularly in the gastrointestinal and musculoskeletal systems. FF quantification is becoming established as a clinical and research tool, and understanding the underlying principles will be helpful to both imaging scientists and clinicians.

Noninvasive Quantitative Detection Methods of Liver Fat Content in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) ranges from simple steatosis to NAFLD-related liver cirrhosis and is a main cause of chronic liver diseases. Patients with nonalcoholic steatohepatitis and fibrosis are at a great risk of the progression to cirrhosis or hepatocellular carcinoma, both of which are tightly associated with liver-related mortality. Liver biopsy is still the gold standard for the diagnosis of NAFLD, but some defects, such as serious complications, sampling error and variability in histologic evaluation among pathologists, remain problematic. Therefore, noninvasive, repeatable and accurate diagnostic methods are urgently needed. Ultrasonography is a well-established and lower-cost imaging technique for the diagnosis of hepatic steatosis, especially suitable for population census, but limited by its low sensitivity to diagnose mild steatosis and being highly operator-dependent. Computed tomography also lacks the sensitivity to detect mild steatosis and small changes in fat content, and presents a potential radiation hazard. Controlled attenuation parameter based on the FibroScan^® technology is a promising tool for noninvasive semiquantitative assessment of liver fat content, but the accuracy rate depends on the operator's expertise and is affected by age, width of the intercostal space, skin capsular distance and body mass index. Magnetic resonance imaging and magnetic resonance spectroscopy are regarded as the most accurate quantitative methods for measuring liver fat content in clinical practice, especially for longitudinal follow up of NAFLD patients. In this review, we mainly introduce the current imaging methods that are in use for evaluation of liver fat content and we discuss the advantages and disadvantages of each method.

Fracture of ankle: MRI using opposed-phase imaging obtained from turbo spin echo modified Dixon image shows improved sensitivity

OBJECTIVE

To evaluate if opposed-phase (OP) imaging obtained from the turbo spin echo (TSE) modified Dixon (mDixon) technique can increase the sensitivity of MRI for diagnosing ankle fractures.

METHODS

This study included 95 CT-confirmed ankle fractures with additional MRI of the ankle using a TSE modified Dixon (mDixon) technique. Two groups of images were analyzed independently: Group 1-imaging group without OP imaging; Group 2-imaging group with OP imaging. Readers assessed the images using a 4-point confidence score to detect fractures. During the first review session, the fracture site was blinded. For the second review session, the fracture site was provided. Sensitivity and positive-predictive value were calculated.

RESULTS

In both sessions, the sensitivity for Group 2 was significantly greater than that for Group 1 (Session 1: 76.3% vs 62.6%, p < 0.0001; Session 2: 80.5% vs 65.3%, p < 0.0001). The positive-predictive value of Group 2 was significantly lower in both sessions 1 and 2 (Session 1: 85.8% vs 97.5%, p < 0.0001; Session 2: 90.5% vs 96.9%, p = 0.0068). Among the 28 false-negative fractures missed in Group 1 (Session 1), 12 (9 minimal displaced and 4 small diameter fractures) were identified in Group 2 (Session 1). While 8.9% showed lower movement, 33.6% showed upper movement in Group 2 compared with Group 1. Possible causes of false-positive lesions were subcutaneous fat, bone marrow edema, and intraosseous vessel mimic fractures.

CONCLUSION

OP imaging obtained using the modified Dixon technique provided better sensitivity and improved descriptions of fractures, especially for minimal displaced fractures and small diameter fractures. However, caution is required when diagnosing fractures with OP imaging because pseudofractures can appear as a result of adjacent bone marrow edema, vascular structures, or subcutaneous fat lobules. Advances in knowledge: In MRI, minimal displaced or small chip bone fracture maybe missed, OP imaging obtained using the mDixon technique provided better sensitivity and improved descriptions of fractures using the black boundary artifact.

Detection of vertebral metastases: a comparison between the modified Dixon turbo spin echo T2 weighted MRI and conventional T1 weighted MRI: a preliminary study in a tertiary centre

OBJECTIVE

To compare the diagnostic performance of modified Dixon (mDixon) turbo spin echo (TSE) T₂ weighted MRI and conventional T₁ weighted MRI in vertebral metastasis detection.

METHODS

Between September 2014 and October 2016, 33 patients with 68 metastases who had undergone whole-spine MRI were enrolled. The following sagittal image sets were evaluated: T₁WI, and mDixon TSE T₂ weighted water and fat images. Two radiologists independently evaluated each image-set for metastasis. The MR findings were compared with positron emission tomography-CT (PET-CT) scans. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for each sequence. The diagnostic performance of each sequence was evaluated using receiver operating characteristic (ROC) curves.

RESULTS

Sensitivity, specificity, PPV and NPV for reviewer 1 were 83.8, 99.1, 89.1 and 98.6%, respectively, with T₁WI; 79.4, 98.8, 85.7 and 98.2%, respectively, with mDixon TSE T₂ weighted water imaging; and 86.8, 99.1, 89.4 and 98.8%, respectively, with mDixon TSE T₂ weighted fat imaging. For reviewer 2, the respective scores were 91.2, 99.2, 91.2 and 99.2%; 85.3, 99.5, 93.4 and 98.7%; and 89.7, 99.3, 92.4 and 99.1%. With PET-CT as the gold standard, the ROC curves of the three sequences showed no significant difference (all p > 0.05).

CONCLUSION

The diagnostic performance of mDixon TSE T₂ weighted water and fat imaging was comparable to that of conventional T₁WI in the detection of vertebral metastases. Advances in knowledge: mDixon TSE T₂WI can be a good alternative to conventional T₁WI for detecting vertebral metastases.

Usefulness of black boundary artifact on opposed-phase imaging from turbo spin-echo two-point mDixon MRI for delineation of an arthroscopically confirmed small fracture of the lateral talar dome: A case report

RATIONALE

A nondisplaced chip fracture can be missed on MRI. Opposed-phase imaging from mDixon MRI produces an interesting artifact called black boundary artifact. This artifact can provide better contrast at the fracture line resulting in better depiction of a small chip fracture on MRI.

PATIENT CONCERNS

We present a case of small nondisplaced chip fracture at the lateral talar dome that was well delineated only with the aid of a black boundary artifact after using T2-weighted opposed-phase imaging from turbo spin-echo two-point modified Dixon ankle MRI. In other sequences, the lesion demonstrated a focal full thickness cartilage defect, subtle cortical irregularity, or subcortical bone marrow edema but the full delineation of the fracture line was not possible.

DIAGNOSES

Opposed-phase imaging from mDixon MRI aided in the diagnosis of lateral talar dome osteochondral fracture (osteochondral lesion), which was confirmed arthroscopically.

INTERVENTIONS

The osteochondral fragment was removed by arthroscopy.

OUTCOMES

The patient did well with recovery of full range of motion after 2 months.

LESSONS

We have identified a black boundary artifact using opposed-phase imaging from mDixon MRI that can aid in detection of small fracture, which can be missed by conventional MRI, by providing a dark linear signal at the fracture line.

Improved fat-suppression homogeneity with mDIXON turbo spin echo (TSE) in pediatric spine imaging at 3.0 T

Background Robust fat suppression remains essential in clinical MRI to improve tissue signal contrast, minimize fat-related artifacts, and enhance image quality. Purpose To compare fat suppression between mDIXON turbo spin echo (TSE) and conventional frequency-selective and inversion-recovery methods in pediatric spine MRI. Material and Methods Images from T1-weighted (T1W) and T2-weighted (T2W) TSE sequences coupled with conventional methods and the mDIXON technique were compared in 36 patients (5.8 ± 5.4 years) at 3.0 T. Images from 42 pairs of T1W (n = 16) and T2W (n = 26) scans were acquired. Two radiologists reviewed the data and rated images using a three-point scale in two categories, including the uniformity of fat suppression and overall diagnostic image quality. The Wilcoxon rank-sum test was used to compare the scores. Results The Cohen's kappa coefficient for inter-rater agreement was 0.69 (95% confidence interval [CI], 0.56-0.83). Images from mDIXON TSE were considered superior in fat suppression ( P < 0.01) in 22 (rater 1) and 25 (rater 2) cases, respectively. In 13 (rater 1) and 11 (rater 2) cases, mDIXON TSE demonstrated improved diagnostic image quality ( P < 0.01). In three cases, fat suppression was superior using inversion-recovery and likewise in one case mDIXON had poorer image diagnostic quality. Lastly, mDIXON and conventional fat-suppression methods performed similarly in 17 (rater 1) and 14 (rater 2) cases, and yielded equal diagnostic image quality in 28 (rater 1) and 30 (rater 2) cases. Conclusion Robust fat suppression can be achieved with mDixon TSE pediatric spine imaging at 3.0 T and should be considered as a permanent replacement of traditional methods, in particular frequency-selective techniques.