Chemical shift imaging with in-phase and opposed-phase sequences at 3 T: what is the optimal threshold, measurement method, and diagnostic accuracy for characterizing marrow signal abnormalities?

Value of third-generation of VNCa dual-energy CT for differentiating diffuse marrow infiltration of multiple myeloma from red bone marrow

This study aims to investigate the ability of bone marrow imaging using third-generation dual-energy computed tomography (CT) virtual noncalcium (VNCa) to differentiate between multiple myeloma (MM) with diffuse bone marrow infiltration and red bone marrow (RBM). Bone marrow aspiration or follow-up results were used as reference. We retrospectively reviewed 188 regions of interests (ROIs) from 21 patients with confirmed MM and diffuse bone marrow infiltrations who underwent VNCa bone marrow imaging between May 2019 and September 2022. At the same time, we obtained 98 ROIs from 11 subjects with RBM for comparative study, and 189 ROIs from 20 subjects with normal yellow bone marrow for the control group. The ROIs were delineated by 2 radiologists independently, the interobservers reproducibility was evaluated by interclass correlation coefficients. The correlation with MRI grade results was analyzed by Spearman correlation coefficient. Receiver operating characteristic (ROC) curve analysis was used to determine the optimal threshold for differentiating between these groups and to assess diagnostic performance. There were statistically significant differences in VNCa CT values of bone marrow among the MM, RBM, and control groups (all P < .001), with values decreasing sequentially. A strong positive rank correlation was observed between normal bone marrow, subgroup MM with moderately and severe bone marrow infiltration divided by MRI and their corresponding CT values (ρ = 0.897, 95%CI: 0.822 to 0.942, P < .001). When the CT value of VNCa bone marrow was 7.15 HU, the area under the curve (AUC) value for differentiating RBM and MM was 0.723, with a sensitivity of 50.5% and a specificity of 89.8%. When distinguishing severe bone marrow infiltration of MM from RBM, the AUC value was 0.80 with a sensitivity 70.9% and a specificity 78.9%. The AUC values for MM, RBM, and the combined group compared to the control group were all >0.99, with all diagnostic sensitivity and specificity exceeding 95%. VNCa bone marrow imaging using third-generation dual-energy CT accurately differentiates MM lesions from normal bone marrow or RBM. It demonstrates superior diagnostic performance in distinguishing RBM from MM with diffuse bone marrow infiltration.

In-phase and opposed-phase Dixon chemical shift imaging for the assessment of skeletal marrow lesions: comparison of measurements from longitudinal sequences to those from axial sequences

OBJECTIVE

In-phase and opposed-phase chemical shift imaging (CSI) is a useful technique for assessing skeletal lesions. This study determined the frequency of significant differences in measurements obtained from longitudinal (coronal or sagittal) sequences to those obtained from axial sequences.

METHODS

Chemical shift imaging was undertaken in 96 consecutive patients referred from the Musculoskeletal Sarcoma and Spinal Oncology services for assessment of possible bone tumours as part of a standard tumour protocol, which included turbo spin echo and inversion recovery sequences. For spinal lesions, CSI was obtained in the sagittal and axial planes, while for all other sites, it was obtained in the coronal and axial planes.

RESULTS

The study included 49 (51.0%) males and 47 (49.0%) females with mean age 42.4 years (range 2-91 years). In 4 cases, 2 individual lesions were assessed, making a total of 100 lesions. Based on typical imaging features (n = 57) or histology (n = 43), 22 lesions (22%) were classified as non-neoplastic, 44 (44%) as benign neoplasms, 6 (6%) as intermediate-grade neoplasms, and 28 (28%) as malignant neoplasms. A significant discrepancy, wherein a lesion was classified as fat-containing (% SI drop >20%-25%) in the longitudinal plane, while in the axial plane it was classified as fat-replacing (% SI drop <20%-25%), or vice versa, occurred in 9%-14% of cases. However, this discrepancy had no appreciable effect on overall diagnostic accuracy, which was calculated at 79% for the longitudinal plane and 75%-80% for the axial plane.

CONCLUSIONS

Significant differences in CSI measurements occur in 9%-14% of cases based on imaging plane, but with no significant effect on diagnostic accuracy.

ADVANCES IN KNOWLEDGE

Radiologists should be aware that CSI measurements in different planes appear to have significant differences in up to 14% of lesions. However, diagnostic accuracy does not seem to be significantly affected.

Magnetic Resonance Imaging Biomarkers of Bone and Soft Tissue Tumors

Magnetic resonance imaging (MRI) is essential in the management of musculoskeletal (MSK) tumors. This review delves into the diverse MRI modalities, focusing on anatomical, functional, and metabolic sequences that provide essential biomarkers for tumor detection, characterization, disease extent determination, and assessment of treatment response. MRI's multimodal capabilities offer a range of biomarkers that enhance MSK tumor evaluation, aiding in better patient management.

Fat quantification: Imaging methods and clinical applications in cancer

Recently, the study of the relationship between lipid metabolism and cancer has evolved. The characteristics of intratumoral and peritumoral fat are distinct and changeable during cancer development. Subcutaneous and visceral adipose tissue are also associated with cancer prognosis. In non-invasive imaging, fat quantification parameters such as controlled attenuation parameter, fat volume fraction, and proton density fat fraction from different imaging methods complement conventional images by providing concrete fat information. Therefore, measuring the changes of fat content for further understanding of cancer characteristics has been applied in both research and clinical settings. In this review, the authors summarize imaging advances in fat quantification and highlight their clinical applications in cancer precaution, auxiliary diagnosis and classification, therapy response monitoring, and prognosis.

Role of advanced MRI techniques for sacroiliitis assessment and quantification

The introduction of MRI was supposed to be a qualitative leap for the evaluation of Sacroiliac Joint (SIJ) in patients with Axial Spondyloarthropathies (AS). In fact, MRI findings such as bone marrow edema around the SIJ has been incorporated into the Assessment in SpondyloArthritis International Society (ASAS criteria). However, in the era of functional imaging, a qualitative approach to SIJ by means of conventional MRI seems insufficient. Advanced MRI sequences, which have successfully been applied in other anatomical areas, are demonstrating their potential utility for a more precise assessment of SIJ. Dixon sequences, T2-mapping, Diffusion Weighted Imaging or DCE-MRI can be properly acquired in the SIJ with promising and robust results. The main advantage of these sequences resides in their capability to provide quantifiable parameters that can be used for diagnosis of AS, surveillance or treatment follow-up. Further studies are needed to determine if these parameters can also be integrated into ASAS criteria for reaching a more precise classification of AS based not only on visual assessment of SIJ but also on measurable data.

Multi-parametric whole-body MRI evaluation discerns vital from non-vital multiple myeloma lesions as validated by 18F-FDG and 11C-methionine PET/CT

PURPOSE

We tested a novel multi-parametric (mp) whole body (WB)-MRI evaluation algorithm for medullary lesions in comparison to positron emission tomography (PET) radiotracers ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and ¹¹C-methionine (¹¹C-MET).

METHODS AND MATERIALS

This retrospective single-center study included 44 MM patients, who received both ¹⁸F-FDG-PET and WB-MRI within ten days. MRI classified focal lesions as vital when showing 1) significant diffusion-restriction, 2) a fat fraction (FF) less than 20 % and 3) homogenous hypointensity on T2-weighted images. On a lesion-by-lesion level the findings were compared to ¹⁸F-FDG PET by using a 5-point scoring system (analogous to the Deauville score [DS]). In 24/44 (55 %) patients additional comparison to ¹¹C-MET PET was available.

RESULTS

Among two radiologists, an excellent inter-observer reliability for mpWB-MRI in a total of 84 medullary lesions was observed (ICC = 1, k = 1, p <.01). 16/17 (94.1 %) MRI-classified vital lesions had a DS of 4 or 5 on either ¹⁸F-FDG-PET or ¹¹C-MET-PET. MRI-rated non-vital lesions correlated with PET-based DS ≤ 3. When results of mpWB-MRI were compared to ¹⁸F-FDG, a fair inter-observer agreement was recorded (ICC = 0.52, k = 0.53, p <.01), while for ¹¹C-MET, an excellent concordance rate was achieved (ICC = 0.81, k = 0.79, p <.01).

CONCLUSION

The proposed mpWB-MRI interpretation algorithm allowed to assess tumor activity of myeloma lesions with high inter-observer reproducibility. We observed a substantial concordance between the mpWB-MRI classification of lesions and PET assessment based on a semi-automatically calculated 5-point scoring system analogous to the Deauville scores.

The Value of 3 Tesla Field Strength for Musculoskeletal Magnetic Resonance Imaging

ABSTRACT

Musculoskeletal magnetic resonance imaging (MRI) is a careful negotiation between spatial, temporal, and contrast resolution, which builds the foundation for diagnostic performance and value. Many aspects of musculoskeletal MRI can improve the image quality and increase the acquisition speed; however, 3.0-T field strength has the highest impact within the current diagnostic range. In addition to the favorable attributes of 3.0-T field strength translating into high temporal, spatial, and contrast resolution, many 3.0-T MRI systems yield additional gains through high-performance gradients systems and radiofrequency pulse transmission technology, advanced multichannel receiver technology, and high-end surface coils. Compared with 1.5 T, 3.0-T MRI systems yield approximately 2-fold higher signal-to-noise ratios, enabling 4 times faster data acquisition or double the matrix size. Clinically, 3.0-T field strength translates into markedly higher scan efficiency, better image quality, more accurate visualization of small anatomic structures and abnormalities, and the ability to offer high-end applications, such as quantitative MRI and magnetic resonance neurography. Challenges of 3.0-T MRI include higher magnetic susceptibility, chemical shift, dielectric effects, and higher radiofrequency energy deposition, which can be managed successfully. The higher total cost of ownership of 3.0-T MRI systems can be offset by shorter musculoskeletal MRI examinations, higher-quality examinations, and utilization of advanced MRI techniques, which then can achieve higher gains and value than lower field systems. We provide a practice-focused review of the value of 3.0-T field strength for musculoskeletal MRI, practical solutions to challenges, and illustrations of a wide spectrum of gainful clinical applications.

Do contrast-enhanced and advanced MRI sequences improve diagnostic accuracy for indeterminate lipomatous tumors?

PURPOSE

Benign, intermediate-grade and malignant tumors sometimes have overlapping imaging and clinical characteristics. The purpose of this study was to evaluate the added value of contrast-enhanced sequences (dynamic contrast enhancement (DCE)), diffusion-weighted imaging (DWI), and chemical shift imaging (CSI) to noncontrast MRI sequences for the characterization of indeterminate lipomatous tumors.

MATERIALS AND METHODS

Thirty-two consecutive patients with histologically proven peripheral lipomatous tumors were retrospectively evaluated. Two musculoskeletal radiologists recorded the MRI features in three sessions: (1) with noncontrast T1-weighted and fluid-sensitive sequences; (2) with addition of static pre- and post-contrast 3D volumetric T1-weighted sequences; and (3) with addition of DCE, DWI, and CSI. After each session, readers recorded a diagnosis (benign, intermediate/atypical lipomatous tumor (ALT), or malignant/dedifferentiated liposarcoma (DDL)). Categorical imaging features (presence of septations, nodules, contrast enhancement) and quantitative metrics (apparent diffusion coefficient values, CSI signal loss) were recorded.

RESULTS

For 32 tumors, the diagnostic accuracy of both readers did not improve with the addition of contrast-enhanced sequences, DWI, or CSI (53% (17/32) session 1; 50% (16/30) session 2; 53% (17/32) session 3). Noncontrast features, including thick septations (p = 0.025) and nodules ≥ 1 cm (p < 0.001), were useful for differentiating benign tumors from ALTs and DDLs, as were DWI (p = 0.01) and CSI (p = 0.009) metrics.

CONCLUSION

The addition of contrast-enhanced sequences (static, DCE), DWI, and CSI to a conventional, noncontrast MRI protocol did not improve diagnostic accuracy for differentiating benign, intermediate-grade, and malignant lipomatous tumors. However, we identified potentially useful imaging features by DCE, DWI, and CSI that may help distinguish these entities.

Pediatric skeletal diffusion-weighted magnetic resonance imaging, part 2: current and emerging applications

Diffusion-weighted imaging (DWI) complements the more established T1, fluid-sensitive and gadolinium-enhanced magnetic resonance pulse sequences used to assess several pediatric skeletal pathologies. There is optimism that the technique might not just be complementary but could serve as an alternative to gadolinium and radiopharmaceuticals for several indications. As a non-contrast, free-breathing and noninvasive technique, DWI is especially valuable in children and is readily incorporated into existing MRI protocols. The indications for skeletal DWI in children include distinguishing between benign and malignant skeletal processes, initial assessment and treatment response assessment for osseous sarcomas, and assessment of inflammatory arthropathies and femoral head ischemia, among others. A notable challenge of diffusion MRI is the dynamic nature of the growing pediatric skeleton. It is important to consider the child's age when placing DWI findings in context with potential marrow pathology. This review article summarizes the current and evolving applications of DWI for assessing the pediatric skeleton, rounding off the discussion with evolving directions for further research in this realm.

Role of in-phase and out-of-phase chemical shift MRI in differentiation of non-neoplastic versus neoplastic benign and malignant marrow lesions

OBJECTIVE

To determine its ability of in-phase (IP) and out-of-phase (OOP) chemical shift imaging (CSI) to distinguish non-neoplastic marrow lesions, benign bone tumours and malignant bone tumours.

METHODS

CSI was introduced into our musculoskeletal tumour protocol in May 2018 to aid in characterisation of suspected bone tumours. The % signal intensity (SI) drop between IP and OOP sequences was calculated and compared to the final lesion diagnosis, which was classified as non-neoplastic (NN), benign neoplastic (BN) or malignant neoplastic (MN).

RESULTS

The study included 174 patients (84 males; 90 females: mean age 44.2 years, range 2-87 years). Based on either imaging features (n = 105) or histology (n = 69), 44 lesions (25.3%) were classified as NN, 66 (37.9%) as BN and 64 (36.8%) as MN. Mean % SI drop on OOP for NN lesions was 36.6%, for BN 3.19% and for MN 3.24% (p < 0.001). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and diagnostic accuracy of CSI for differentiating NN from neoplastic lesions were 65.9%, 94.6%, 80.6%, 89.1%% and 87.4% respectively, and for differentiating BN from MN were 9.1%, 98.4%, 85.7%, 51.2 and 53.1% respectively.

CONCLUSION

CSI is accurate for differentiating non-neoplastic and neoplastic marrow lesions, but is of no value in differentiating malignant bone tumours from non-fat containing benign bone tumours.

ADVANCES IN KNOWLEDGE

CSI is of value for differentiating non-neoplastic marrow lesions from neoplastic lesions, but not for differentiating benign bone tumours from malignant bone tumours as has been previously reported.

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.

The Value of Quantitative Musculoskeletal Imaging

Musculoskeletal imaging is mainly based on the subjective and qualitative analysis of imaging examinations. However, integration of quantitative assessment of imaging data could increase the value of imaging in both research and clinical practice. Some imaging modalities, such as perfusion magnetic resonance imaging (MRI), diffusion MRI, or T2 mapping, are intrinsically quantitative. But conventional morphological imaging can also be analyzed through the quantification of various parameters. The quantitative data retrieved from imaging examinations can serve as biomarkers and be used to support diagnosis, determine patient prognosis, or monitor therapy.

We focus on the value, or clinical utility, of quantitative imaging in the musculoskeletal field. There is currently a trend to move from volume- to value-based payments. This review contains definitions and examines the role that quantitative imaging may play in the implementation of value-based health care. The influence of artificial intelligence on the value of quantitative musculoskeletal imaging is also discussed.

Anomalous signal intensity increase on out-of-phase chemical shift imaging: a manifestation of marrow mineralisation?

OBJECTIVE

In-phase (IP) and out-of-phase (OOP) chemical shift imaging (CSI) is an established technique for clarifying the nature of indeterminate bone marrow lesions, a signal intensity (SI) drop of > 20% at 1.5 tesla (T) or > 25% on 3 T on the OOP sequence being consistent with a non-neoplastic process. Occasionally, SI increase is seen on OOP sequences. The aim of this study is to determine if this is related to marrow sclerosis or matrix mineralisation.

MATERIALS AND METHODS

In 184 cases, the SI change on OOP was calculated. For patients in whom the SI on OOP increased compared with the IP sequence, available CT studies and radiographs were reviewed to look for marrow sclerosis and/or matrix mineralisation.

RESULTS

Forty out of 184 patients (34.25%) showed an anomalous increase in SI on the OOP sequence. CT studies were available in 27 cases (67.5%), of which medullary sclerosis was seen in 20 (74.1%) while matrix mineralisation was seen in a further 2 cases. Review of radiographs demonstrated matrix mineralisation in 6 cases, while punctate signal void consistent with chondral calcification was seen on MRI in 2 more cases. Based on either typical imaging features (n = 22) or histology (n = 18), 7 lesions (17.5%) were classed as non-neoplastic, 18 (45%) as benign neoplasms and 15 (37.5%) as malignant neoplasms.

CONCLUSION

When assessing focal marrow lesions with CSI, anomalous SI increase may be seen on the OOP sequence in approximately one-third of cases. In over 75% of such cases, CT or radiographs demonstrate either diffuse marrow sclerosis or matrix mineralisation.

Pelvic bone tumor resection: what a radiologist needs to know

Pelvic bone tumors present a diagnostic and therapeutic challenge. Due to the deep anatomic location and resultant late clinical presentation, pelvic bone tumors tend to be large and located in close proximity to pelvic viscera as well as vital neurovascular structures. Operative management of pelvic bone tumors is indicated for a variety of orthopedic oncologic conditions. In general, limb-sparing pelvic resection rather than hemipelvectomy with amputation of the ipsilateral limb is considered when a functional limb can be preserved without compromising the surgical margins. There are various options for pelvic resection and reconstruction, and the selection depends on tumor histology, anatomic location, and extent. The decision regarding choice of surgical procedure and reconstruction method for a pelvic bone tumor requires a thorough knowledge of the pelvic anatomy, and careful inspection of the anatomic extent. The surgical plan must strike a balance between acceptable functional outcome and acceptable morbidity. In this review, we describe the different types of pelvic resection techniques, and the vital role preoperative imaging plays in defining the anatomic extent of a pelvic bone tumor and subsequent surgical planning.

The Dixon technique for MRI of the bone marrow

Dixon sequences are established as a reliable MRI technique that can be used for problem-solving in the assessment of bone marrow lesions. Unlike other fat suppression methods, Dixon techniques rely on the difference in resonance frequency between fat and water and in a single acquisition, fat only, water only, in-phase and out-of-phase images are acquired. This gives Dixon techniques the unique ability to quantify the amount of fat within a bone lesion, allowing discrimination between marrow-infiltrating and non-marrow-infiltrating lesions such as focal nodular marrow hyperplasia. Dixon can be used with gradient echo and spin echo techniques, both two-dimensional and three-dimensional imaging. Another advantage is its rapid acquisition time, especially when using traditional two-point Dixon gradient echo sequences. Overall, Dixon is a robust fat suppression method that can also be used with intravenous contrast agents. After reviewing the available literature, we would like to advocate the implementation of additional Dixon sequences as a problem-solving tool during the assessment of bone marrow pathology.

MRI biomarkers in osseous tumors

Although radiography continues to play a critical role in osseous tumor assessment, there have been remarkable advances in cross-sectional imaging. MRI has taken a lead in this assessment due to high tissue contrast and spatial resolution, which are well suited for bone lesion assessment. More recently, although somewhat lagging other organ systems, quantitative parameters have shown promising potential as biomarkers for osseous tumors. Among these sequences are chemical shift imaging (CSI), apparent diffusion coefficient (ADC), and intravoxel incoherent motion (IVIM) from diffusion-weighted imaging (DWI), quantitative dynamic contrast enhanced (DCE)-MRI, and magnetic resonance spectroscopy (MRS). In this article, we review the background and recent roles of these quantitative MRI biomarkers for osseous tumors. Level of Evidence: 3 Technical Efficacy Stage: 3 J. MAGN. RESON. IMAGING 2019. J. Magn. Reson. Imaging 2019;50:702-718.