Assessing myeloma bone disease with whole-body diffusion-weighted imaging: comparison with x-ray skeletal survey by region and relationship with laboratory estimates of disease burden

Recent advances in imaging and artificial intelligence (AI) for quantitative assessment of multiple myeloma

Multiple myeloma (MM) is a malignant blood disease, but there have been significant improvements in the prognosis due to advancements in quantitative assessment and targeted therapy in recent years. The quantitative assessment of MM bone marrow infiltration and prognosis prediction is influenced by imaging and artificial intelligence (AI) quantitative parameters. At present, the primary imaging methods include computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). These methods are now crucial for diagnosing MM and evaluating myeloma cell infiltration, extramedullary disease, treatment effectiveness, and prognosis. Furthermore, the utilization of AI, specifically incorporating machine learning and radiomics, shows great potential in the field of diagnosing MM and distinguishing between MM and lytic metastases. This review discusses the advancements in imaging methods, including CT, MRI, and PET/CT, as well as AI for quantitatively assessing MM. We have summarized the key concepts, advantages, limitations, and diagnostic performance of each technology. Finally, we discussed the challenges related to clinical implementation and presented our views on advancing this field, with the aim of providing guidance for future research.

Development of a whole spinal MRI-based tumor burden scoring method in participants with multiple myeloma: a pilot study of prognostic significance

The aim of the study was to develop a new whole spinal MRI-based tumor burden scoring method in participants with newly diagnosed multiple myeloma (MM) and to explore its prognostic significance. We prospectively recruited participants with newly diagnosed MM; performed whole spinal MRI (sagittal FSE T1WI, sagittal IDEAL T2WI, and axial FLAIR T2WI) on them; and collected their clinical data, early treatment response, progression-free survival (PFS), and overall survival (OS). We developed a new tumor burden scoring method according to the extent of bone marrow infiltration in five MRI patterns. All participants were divided into good response and poor response groups after four treatment cycles. Univariate, multivariate analyses, and ROC were used to determine the performance of independent predictors. Thresholds for PFS and OS were calculated using X-tile, and their prognostic significance were assessed by Kaplan-Meier. The Kruskal-Wallis H test was used to compare the differences of tumor burden score between the revised International Staging System (R-ISS) stages. The new tumor burden scoring method was used in 62 participants (median score, 12; range, 0-18). The tumor burden score (OR 1.266, p = 0.002) was an independent predictor of poor response and the AUC was 0.838. Higher tumor burden scores were associated with shorter PFS (p = 0.002) and OS (p = 0.011). The tumor burden score was higher in R-ISS-III than in R-ISS-I and R-ISS-II (p = 0.016 and p = 0.006, respectively). The tumor burden score was an excellent predictor of prognosis and may serve as a supplemental marker for R-ISS.

Predicting cytogenetic risk in multiple myeloma using conventional whole-body MRI, spinal dynamic contrast-enhanced MRI, and spinal diffusion-weighted imaging

OBJECTIVES

Cytogenetic abnormalities are predictors of poor prognosis in multiple myeloma (MM). This paper aims to build and validate a multiparametric conventional and functional whole-body MRI-based prediction model for cytogenetic risk classification in newly diagnosed MM.

METHODS

Patients with newly diagnosed MM who underwent multiparametric conventional whole-body MRI, spinal dynamic contrast-enhanced (DCE-)MRI, spinal diffusion-weighted MRI (DWI) and had genetic analysis were retrospectively included (2011-2020/Ghent University Hospital/Belgium). Patients were stratified into standard versus intermediate/high cytogenetic risk groups. After segmentation, 303 MRI features were extracted. Univariate and model-based methods were evaluated for feature and model selection. Testing was performed using receiver operating characteristic (ROC) and precision-recall curves. Models comparing the performance for genetic risk classification of the entire MRI protocol and of all MRI sequences separately were evaluated, including all features. Four final models, including only the top three most predictive features, were evaluated.

RESULTS

Thirty-one patients were enrolled (mean age 66 ± 7 years, 15 men, 13 intermediate-/high-risk genetics). None of the univariate models and none of the models with all features included achieved good performance. The best performing model with only the three most predictive features and including all MRI sequences reached a ROC-area-under-the-curve of 0.80 and precision-recall-area-under-the-curve of 0.79. The highest statistical performance was reached when all three MRI sequences were combined (conventional whole-body MRI + DCE-MRI + DWI). Conventional MRI always outperformed the other sequences. DCE-MRI always outperformed DWI, except for specificity.

CONCLUSIONS

A multiparametric MRI-based model has a better performance in the noninvasive prediction of high-risk cytogenetics in newly diagnosed MM than conventional MRI alone.

CRITICAL RELEVANCE STATEMENT

An elaborate multiparametric MRI-based model performs better than conventional MRI alone for the noninvasive prediction of high-risk cytogenetics in newly diagnosed multiple myeloma; this opens opportunities to assess genetic heterogeneity thus overcoming sampling bias.

KEY POINTS

• Standard genetic techniques in multiple myeloma patients suffer from sampling bias due to tumoral heterogeneity. • Multiparametric MRI noninvasively predicts genetic risk in multiple myeloma. • Combined conventional anatomical MRI, DCE-MRI, and DWI had the highest statistical performance to predict genetic risk. • Conventional MRI alone always outperformed DCE-MRI and DWI separately to predict genetic risk. DCE-MRI alone always outperformed DWI separately, except for the parameter specificity to predict genetic risk. • This multiparametric MRI-based genetic risk prediction model opens opportunities to noninvasively assess genetic heterogeneity thereby overcoming sampling bias in predicting genetic risk in multiple myeloma.

Diffusion-weighted imaging (DWI) in diagnosis, staging, and treatment response assessment of multiple myeloma: a systematic review and meta-analysis

OBJECTIVE

To evaluate the role of diffusion-weighted imaging (DWI) in the initial diagnosis, staging, and assessment of treatment response in patients with multiple myeloma (MM).

MATERIALS AND METHODS

A systematic literature review was conducted in PubMed, the Cochrane Library, EMBASE, Scopus, and Web of Science databases. The primary endpoints were defined as the diagnostic performance of DWI for disease detection, staging of MM, and assessing response to treatment in these patients.

RESULTS

Of 5881 initially reviewed publications, 33 were included in the final qualitative and quantitative meta-analysis. The diagnostic performance of DWI in the detection of patients with MM revealed pooled sensitivity and specificity of 86% (95% CI: 84-89) and 63% (95% CI: 56-70), respectively, with a diagnostic odds ratio (OR) of 14.98 (95% CI: 4.24-52.91). The pooled risk difference of 0.19 (95% CI: - 0.04-0.42) was reported in favor of upstaging with DWI compared to conventional MRI (P value = 0.1). Treatment response evaluation and ADC_mean value changes across different studies showed sensitivity and specificity of approximately 78% (95% CI: 72-83) and 73% (95% CI: 61-83), respectively, with a diagnostic OR of 7.21 in distinguishing responders from non-responders.

CONCLUSIONS

DWI is not only a promising tool for the diagnosis of MM, but it is also useful in the initial staging and re-staging of the disease and treatment response assessment. This can aid clinicians with earlier initiation or change in treatment strategy, which could have prognostic significance for patients.

Development of machine learning support for reading whole body diffusion-weighted MRI (WB-MRI) in myeloma for the detection and quantification of the extent of disease before and after treatment (MALIMAR): protocol for a cross-sectional diagnostic test accuracy study

INTRODUCTION

Whole-body MRI (WB-MRI) is recommended by the National Institute of Clinical Excellence as the first-line imaging tool for diagnosis of multiple myeloma. Reporting WB-MRI scans requires expertise to interpret and can be challenging for radiologists who need to meet rapid turn-around requirements. Automated computational tools based on machine learning (ML) could assist the radiologist in terms of sensitivity and reading speed and would facilitate improved accuracy, productivity and cost-effectiveness. The MALIMAR study aims to develop and validate a ML algorithm to increase the diagnostic accuracy and reading speed of radiological interpretation of WB-MRI compared with standard methods.

METHODS AND ANALYSIS

This phase II/III imaging trial will perform retrospective analysis of previously obtained clinical radiology MRI scans and scans from healthy volunteers obtained prospectively to implement training and validation of an ML algorithm. The study will comprise three project phases using approximately 633 scans to (1) train the ML algorithm to identify active disease, (2) clinically validate the ML algorithm and (3) determine change in disease status following treatment via a quantification of burden of disease in patients with myeloma. Phase 1 will primarily train the ML algorithm to detect active myeloma against an expert assessment ('reference standard'). Phase 2 will use the ML output in the setting of radiology reader study to assess the difference in sensitivity when using ML-assisted reading or human-alone reading. Phase 3 will assess the agreement between experienced readers (with and without ML) and the reference standard in scoring both overall burden of disease before and after treatment, and response.

ETHICS AND DISSEMINATION

MALIMAR has ethical approval from South Central-Oxford C Research Ethics Committee (REC Reference: 17/SC/0630). IRAS Project ID: 233501. CPMS Portfolio adoption (CPMS ID: 36766). Participants gave informed consent to participate in the study before taking part. MALIMAR is funded by National Institute for Healthcare Research Efficacy and Mechanism Evaluation funding (NIHR EME Project ID: 16/68/34). Findings will be made available through peer-reviewed publications and conference dissemination.

TRIAL REGISTRATION NUMBER

NCT03574454.

Advanced Imaging in Multiple Myeloma: New Frontiers for MRI

Plasma cell dyscrasias are estimated to newly affect almost 40,000 people in 2022. They fall on a spectrum of diseases ranging from relatively benign to malignant, the malignant end of the spectrum being multiple myeloma (MM). The International Myeloma Working Group (IMWG) has traditionally outlined the diagnostic criteria and therapeutic management of MM. In the last two decades, novel imaging techniques have been employed for MM to provide more information that can guide not only diagnosis and staging, but also treatment efficacy. These imaging techniques, due to their low invasiveness and high reliability, have gained significant clinical attention and have already changed the clinical practice. The development of functional MRI sequences such as diffusion weighted imaging (DWI) or intravoxel incoherent motion (IVIM) has made the functional assessment of lesions feasible. Moreover, the growing availability of positron emission tomography (PET)–magnetic resonance imaging (MRI) scanners is leading to the potential combination of sensitive anatomical and functional information in a single step. This paper provides an organized framework for evaluating the benefits and challenges of novel and more functional imaging techniques used for the management of patients with plasma cell dyscrasias, notably MM.

Histogram Analysis Based on Apparent Diffusion Coefficient Maps of Bone Marrow in Multiple Myeloma: An Independent Predictor for High-risk Patients Classified by the Revised International Staging System

RATIONALE AND OBJECTIVES

The revised International Staging System (R-ISS) is the current risk stratifier for patients with newly diagnosed multiple myeloma (NDMM). We used histogram analysis based on apparent diffusion coefficient (ADC) maps of bone marrow to predict high-risk NDMM patients staged as R-ISS stage III.

MATERIAL AND METHODS

Sixty-one NDMM patients were recruited prospectively and underwent whole-body diffusion-weighted MRI. Mean ADC and four ADC-based histogram parameters of representative background bone marrow were quantified with TexRAD software, including ADC entropy, ADC standard deviation (SD), ADC skewness and ADC kurtosis. Diagnostic performance to discriminate R-ISS III from I/II disease was evaluated by receiver-operating characteristics curve (ROC). Univariate and multivariate analysis using stepwise logistic regression model was performed to identify predictors for R-ISS III.

RESULTS

ADC entropy of background marrow showed the highest areas under the ROC (0.784, sensitivity = 93.3%, specificity = 63.0%) for the detection of R-ISS stage III disease. Multivariate analysis showed that increased ADC entropy (>3.612) of background marrow can independently predict R-ISS stage III disease in the overall patients (Model 1 corrected for diffuse infiltration [DI] pattern: odds ratio [OR], 10.647; p = 0.008; Model 2 corrected for mean ADC: OR, 10.485; p = 0.010) and in the subgroup with DI pattern (OR, 7.043; p = 0.037).

CONCLUSION

ADC entropy of background marrow may serve as a sensitive imaging biomarker facilitating the detection of high-risk NDMM patients staged as R-ISS stage III. Increased ADC entropy of background marrow can independently predict R-ISS stage III in the overall patients and in the subgroup with DI pattern.

Myeloma Response Assessment and Diagnosis System (MY-RADS): strategies for practice implementation

Structured reporting systems have been developed for many organ systems and disease processes beginning with BI-RADS in 1993. Numerous reports indicate that referring health care providers prefer structured reports. Reducing variability of reports from one radiologist to another helps referring physician and patient confidence. Changing radiologists practice habits from completely free text to structured reports can be met with some resistance, but most radiologists quickly find that structured reports make their job easier. Whole-body MR studies are recommended as first-line imaging, by the International Myeloma Working Group (IMWG), for all patients with suspected diagnosis of asymptomatic myeloma and/or initial diagnosis of solitary plasmacytoma. Whole-body MR imaging (WBMRI) has been shown to have equal or greater sensitivity and specificity compared to PET/CT for detection of bone marrow involvement. Changing to WBMRI from other imaging modalities can be difficult for referring providers. Patient acceptance is high. MY-RADS is for myeloma patients who have WBMRI studies done. The intent of the system is to promote uniformity in MR imaging acquisition, diagnostic criteria, and response assessment and to diminish differences in the subsequent interpretation and reporting. A secondary benefit is a report template that provides a guide for interpretation for radiologists who may not have previously dictated these difficult studies. The characterization of bone marrow abnormalities in myeloma patients usually is fairly straightforward. To date, there is no standardized scoring or risk stratification of abnormalities nor is there an imaging atlas of abnormalities.

Imaging of treatment response and minimal residual disease in multiple myeloma: state of the art WB-MRI and PET/CT

Bone imaging has been intimately associated with the diagnosis and staging of multiple myeloma (MM) for more than 5 decades, as the presence of bone lesions indicates advanced disease and dictates treatment initiation. The methods used have been evolving, and the historical radiographic skeletal survey has been replaced by whole body CT, whole body MRI (WB-MRI) and [¹⁸F]FDG-PET/CT for the detection of bone marrow lesions and less frequent extramedullary plasmacytomas.Beyond diagnosis, imaging methods are expected to provide the clinician with evaluation of the response to treatment. Imaging techniques are consistently challenged as treatments become more and more efficient, inducing profound response, with more subtle residual disease. WB-MRI and FDG-PET/CT are the methods of choice to address these challenges, being able to assess disease progression or response and to detect "minimal" residual disease, providing key prognostic information and guiding necessary change of treatment.This paper provides an up-to-date overview of the WB-MRI and PET/CT techniques, their observations in responsive and progressive disease and their role and limitations in capturing minimal residual disease. It reviews trials assessing these techniques for response evaluation, points out the limited comparisons between both methods and highlights their complementarity with most recent molecular methods (next-generation flow cytometry, next-generation sequencing) to detect minimal residual disease. It underlines the important role of PET/MRI technology as a research tool to compare the effectiveness and complementarity of both methods to address the key clinical questions.

Association of loss of spleen visualization on whole-body diffusion-weighted imaging with prognosis and tumor burden in patients with multiple myeloma

This study investigated the clinical significance of loss of spleen visualization (LSV) on whole-body diffusion-weighted imaging (WB-DWI) in patients with multiple myeloma (MM). The WB-DWI of 96 patients with newly diagnosed MM (NDMM) and 15 patients with smoldering MM (sMM) were retrospectively reviewed. LSV was observed in 56 patients with NDMM (58.3%) and 1 patient with sMM (6.7%). Patients with NDMM with LSV had a higher median infiltration of bone marrow plasma cells (80.0% vs. 50.0%, p < 0.001) and median total diffusion volume (median; 540.2 vs. 137.0 mL, p = 0.003) than patients without LSV. Patients with LSV had a lower spleen-to-spinal cord ratio (0.36 vs. 0.96, p < 0.001) and worse 2-year overall survival (OS) (84.6% vs. 100%, p = 0.032). Patients who did not recover spleen visualization during treatment had a worse prognosis, even when they obtained very good partial response (median progression-free survival: 13.2 months). Spleen histopathological findings revealed higher cellularity and diffuse myeloma cell infiltration in a patient with LSV and splenic amyloidosis without extramedullary hematopoiesis in a patient without LSV. Therefore, LSV indicates worse prognosis for patients with MM, even when the patient responds to treatment. Further studies are warranted to clarify the immunological role of spleen in MM.

Comparison of conventional magnetic resonance imaging and diffusion-weighted imaging in the differentiation of bone plasmacytoma from bone metastasis in the extremities

PURPOSE

To compare conventional magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) in the differentiation of bone plasmacytoma from bone metastasis in the extremities.

MATERIALS AND METHODS

A total of 65 patients with 27 bone plasmacytomas (11 men; mean age, 63.6±8.2 [SD] years) and 38 patients with bone metastases (20 men; mean age, 64.1±11.5 [SD] years) were retrospectively included. Plasmacytomas and metastases were compared for size, peritumoral edema, signal intensity (SI), SI pattern, apparent diffusion coefficient (ADC) values and standard deviation (SD) of ADC. Receiver operating characteristic analysis with area under the curve (AUC) was used to calculate sensitivity, specificity, and accuracy of MRI and DWI for the diagnosis of plasmacytoma according to a defined cut-off value.

RESULTS

On conventional MRI, plasmacytomas showed less peritumoral edema (22% vs. 71%; P<0.001), were more often hyperintense on T1-weighted image (48% vs. 18%; P=0.022) and more homogeneous on T2-weighted image (78% vs. 26%; P<0.001) and contrast-enhanced T1-weighted images (70% vs. 25%; P=0.001) than bone metastases. Mean ADC value and SD of ADC were significantly lower in bone plasmacytomas (760.1±196.9 [SD] μm²/s and 161.5±62.7 [SD], respectively) than in bone metastases (1214.2±382.6 [SD] μm²/s and 277.0±110.3 [SD], respectively) (P<0.001). Using an ADC value≤908.3μm²/s, DWI yielded 88% sensitivity and 78% specificity for the diagnosis of plasmacytoma. ADC value yielded best area under the curve (AUC=0.913), followed by SD of ADC (AUC=0.814) and homogeneity on T2-weighted images (AUC=0.757). The combination of conventional MRI and DWI (AUC=0.894) showed improved diagnostic performance over conventional MRI alone (AUC= 0.843) for discriminating between plasmacytoma and metastasis.

CONCLUSION

Conventional MRI in combination with DWI can be useful to discriminate between bone plasmacytoma and bone metastasis in the extremities.

Inter-observer agreement of baseline whole body MRI in multiple myeloma

Background

Whole body magnetic resonance imaging (MRI) is now incorporated into international guidance for imaging patients with multiple myeloma. The aim of this study was to investigate inter-observer agreement of triple reported baseline whole-body MRI in myeloma and highlight potential pitfalls.

Methods

Fifty-seven patients with symptomatic myeloma at first presentation or relapse and planned for autologous stem cell transplant were included. All patients completed baseline whole body MRI within 2 weeks prior to starting treatment. Each scan was reported independently by 3 radiologists using a defined scoring system. Differences in observer scores were compared using analysis of variance (ANOVA) and inter-observer agreement assessed using intra class correlation coefficient (ICC).

Results

There was no significant difference in mean observer scores for whole skeleton and ICC demonstrated excellent inter-observer agreement at 0.91. ICC varied between skeletal regions with spine, pelvis and ribs showing good inter-observer agreement, whereas skull and long bones were moderate. Scans with variation in observer scores were re-examined and cause of discrepancies identified. This information was used to describe potential anatomical pitfalls in reporting .

Conclusion

Whole-body MRI has excellent inter-observer agreement in reporting symptomatic myeloma at baseline. Inter-observer agreement varied between skeletal regions highlighting specific areas of difficulty.

MRI versus 18F-FDG-PET/CT for detecting bone marrow involvement in multiple myeloma: diagnostic performance and clinical relevance

PURPOSE

To compare the diagnostic performance of MRI and ¹⁸F-FDG-PET/CT in detecting bone marrow involvement (BMI) in patients with multiple myeloma (MM).

MATERIALS AND METHODS

This retrospective study was approved by our Institutional Review Board. Two radiologists and two nuclear medicine specialists independently and blindly reviewed 84 pairs of MRI and PET/CT scans obtained in 73 MM patients. Readers assessed the presence and patterns of BMI. The best valuable comparator (BVC) for BMI was established by a panel review of all baseline and follow-up imaging, and biological and pathological information. Intra- and inter-reader agreement and correlation between MRI and PET/CT were assessed using the prevalence-adjusted bias-adjusted kappa (k) coefficient. Diagnostic performance of MRI and PET/CT in detecting BMI was evaluated from ROC characteristics. Association between imaging and biological, pathological, and clinical findings was assessed using Wilcoxon rank-sum and chi-square tests.

RESULTS

Intra- and inter-reader agreement was very good for MRI (k = 0.90 [0.81; 1.00] and 0.88 [0.78; 0.98]). Intra- and inter-reader agreement was good for PET/CT (k = 0.80 [0.69; 0.91] and 0.71 [0.56; 0.86]). The sensitivity of MRI to detect BMI (97% [90%; 100%]) was significantly superior to that of PET/CT (76% [64%; 85%]) (p < 0.001). The specificity of MRI (86% [57%; 98%]) was lower than that of PET/CT (93% [66%; 100%]), without reaching statistical significance (p = 0.32). There was a strong correlation between decisions regarding patient management and PET/CT findings (p < 0.001).

CONCLUSION

MRI is significantly more sensitive than PET/CT to detect BMI in MM. Patient management is more strongly correlated with PET/CT findings.

KEY POINTS

• MRI and PET/CT have very close diagnostic value for the detection of bone marrow involvement in multiple myeloma. • MRI has a significantly higher sensitivity and better reproducibility. • PET/CT findings appear to have a higher impact on clinical decisions.

Interobserver agreement of whole-body magnetic resonance imaging is superior to whole-body computed tomography for assessing disease burden in patients with multiple myeloma

Objectives

Whole-body MRI (WB-MRI) is recommended by the International Myeloma Working Group for all patients with asymptomatic myeloma and solitary plasmacytoma and by the UK NICE guidance for all patients with suspected myeloma. Some centres unable to offer WB-MRI offer low-dose whole-body CT (WB-CT). There are no studies comparing interobserver agreement and disease detection of contemporary WB-MRI (anatomical imaging and DWI) versus WB-CT. Our primary aim is to compare the interobserver agreement between WB-CT and WB-MRI in the diagnosis of myeloma.

Methods

Consecutive patients with newly diagnosed myeloma imaged with WB-MRI and WB-CT were prospectively reviewed. For each body region and modality, two experienced and two junior radiologists scored disease burden with final scores by consensus. Intraclass correlation coefficients (ICC), median scores, Wilcoxon signed-rank test and Spearman’s correlation coefficients were calculated.

Results

There was no significant difference in overall observer scores between WB-MRI and WB-CT (p = 0.87). For experienced observers, interobserver agreement for WB-MRI was superior to WB-CT overall and for each region, without overlap in whole-skeleton confidence intervals (ICC 0.98 versus 0.77, 95%CI 0.96–0.99 versus 0.45–0.91). For inexperienced observers, although there is a trend for a better interobserver score for the whole skeleton on WB-MRI (ICC 0.95, 95%CI 0.72–0.98) than on WB-CT (ICC 0.72, 95%CI 0.34–0.88), the confidence intervals overlap.

Conclusions

WB-MRI offers excellent interobserver agreement which is superior to WB-CT for experienced observers. Although the overall burden was similar across both modalities, patients with lower disease burdens where MRI could be advantageous are not included in this series.

Key Points

• Whole-body MRI is recommended by the International Myeloma Working Group for patients with multiple myeloma and solitary plasmacytoma and by the NICE guidance for those with suspected multiple myeloma.

• Some centres unable to offer whole-body MRI (WB-MRI) offer low-dose whole-body CT (WB-CT).

• This prospective study demonstrates that contemporary WB-MRI (with anatomical sequences and DWI) provides better interobserver agreement in assessing myeloma disease burden for the whole skeleton and across any individual body region in myeloma patients when compared with low-dose whole-body CT.

Electronic supplementary material

The online version of this article (10.1007/s00330-019-06281-x) contains supplementary material, which is available to authorized users.

Comparison of Whole-Body DWI and 18F-FDG PET/CT for Detecting Intramedullary and Extramedullary Lesions in Multiple Myeloma

OBJECTIVE. The purpose of this study was to compare the ability of whole-body (WB) DWI and ¹⁸F-FDG PET/CT in detecting intramedullary and extramedullary lesions in multiple myeloma. MATERIALS AND METHODS. The study included 49 patients with multiple myeloma who had undergone WB DWI and PET/CT. Intramedullary lesions for each region were scored by a scoring system using WB DWI and PET/CT separately. Extramedullary lesions seen separately on WB DWI and PET/CT per patient were recorded. Patients with diffuse lesions of the whole spine seen using both modalities were defined as group A, and those with such lesions seen on WB DWI only were defined as group B. The mean scores assigned to intramedullary lesions using the two modalities, the numbers of extramedullary lesions detected by WB DWI and PET/CT, and the mean percentages of plasma cells in the two patient groups were compared. RESULTS. Scores were higher for WB DWI than for PET/CT in all regions of the body (p < 0.05) except the skull, both in patients with a new diagnosis of multiple myeloma and in previously treated patients. Mean (± SD) percentages of plasma cells were significantly higher in group A than group B (50.458% ± 16.036% vs 18.682% ± 15.524%; p = 0.00). The mean number of extramedullary lesions detected by WB DWI was slightly higher than the mean number detected by PET/CT, although there was no statistical difference (4.48 ± 6.70 vs 4.39 ± 6.46 lesions; p = 0.86). CONCLUSION. For detecting intramedullary lesions, WB DWI is more sensitive than PET/CT in all regions except the skull, both in patients with a new diagnosis and previously treated patients and especially in patients with a low percentage of plasma cells. For detecting extramedullary lesions, WB DWI has sensitivity equivalent to that of PET/CT. The use of both modalities may offer complementary information.

Guidelines for Acquisition, Interpretation, and Reporting of Whole-Body MRI in Myeloma: Myeloma Response Assessment and Diagnosis System (MY-RADS)

Acknowledging the increasingly important role of whole-body MRI for directing patient care in myeloma, a multidisciplinary, international, and expert panel of radiologists, medical physicists, and hematologists with specific expertise in whole-body MRI in myeloma convened to discuss the technical performance standards, merits, and limitations of currently available imaging methods. Following guidance from the International Myeloma Working Group and the National Institute for Clinical Excellence in the United Kingdom, the Myeloma Response Assessment and Diagnosis System (or MY-RADS) imaging recommendations are designed to promote standardization and diminish variations in the acquisition, interpretation, and reporting of whole-body MRI in myeloma and allow response assessment. This consensus proposes a core clinical protocol for whole-body MRI and an extended protocol for advanced assessments. Published under a CC BY 4.0 license. Online supplemental material is available for this article.

Combination bone marrow imaging using positron emission tomography (PET)-MRI in plasma cell dyscrasias: correlation with prognostic laboratory values and clinicopathological diagnosis

Objective

This prospective observational study of positron emission tomography (PET)-MRI findings in 16 consecutive newly diagnosed patients with a plasma cell dyscrasia describes and compares MRI-detected myeloma lesions with ¹⁸F-fludeoxyglucose PET-avid myeloma lesions, and correlates quantitative imaging findings to a range of biochemical and prognostic parameters.

Methods

Simultaneously acquired whole body PET and MRI images were evaluated qualitatively for the presence of focal or generalised abnormalities of bone marrow (BM) on either modality. Quantitative analysis comprised mean standardised uptake values (SUVmean) and fractional water content of the BM measured from PET and chemical shift MRI images of the second to fourth lumbar vertebrae.

Results

Final diagnoses comprised symptomatic myeloma (n = 10), asymptomatic myeloma (n = 4) and monoclonal gammopathy of uncertain significance (n = 2). 8/10 patients with symptomatic myeloma demonstrated BM abnormalities on qualitative assessment of MRI compared to 4/10 on PET. BM SUVmean inversely correlated with serum albumin (r = 0.57, p = 0.017). BM water fraction correlated with trephine cellularity and blood platelet count (r = 0.78, p = 0.00039 and r = 0.61, p = 0.0013 respectively). BM water fraction correlated with SUVmean in patients with low plasma cell burden (r = 0.91, p = 0.0015) but not in patients with high plasma cell burden (r = 0.18, p = 0.61).

Conclusion

PET-MRI shows promise in both morphological and functional multiparametric quantitative assessment of myeloma.

Advances in knowledge

For the first time, multiparametric imaging in myeloma has been shown to predict BM abnormalities and correlate with known biochemical prognostic markers, moving PET-MRI beyond simple diagnostic applications into potential prognostic and treatment selection applications.

Imaging in myeloma with focus on advanced imaging techniques

In recent years, there have been major advances in the imaging of myeloma with whole body MRI incorporating diffusion-weighted imaging, emerging as the most sensitive modality. Imaging is now a key component in the work-up of patients with a suspected diagnosis of myeloma. The International Myeloma Working Group now specifies that more than one focal lesion on MRI or lytic lesion on whole body low-dose CT or fludeoxyglucose (FDG) PET/CT fulfil the criteria for bone damage requiring therapy. The recent National Institute for Health and Care Excellence myeloma guidelines recommend imaging in all patients with suspected myeloma. In addition, there is emerging data supporting the use of functional imaging techniques (WB-DW MRI and FDG PET/CT) to predict outcome and evaluate response to therapy. This review summarises the imaging modalities used in myeloma, the latest guidelines relevant to imaging and future directions.

Differentiation of multiple myeloma and metastases: Use of axial diffusion-weighted MR imaging in addition to standard MR imaging at 3T

Background

Metastasis and multiple myeloma are common malignant bone marrow lesions which may be difficult to distinguish because of similar imaging findings. The purpose of this study was to determine the value of adding diffusion-weighted imaging (DWI) to standard MR imaging to differentiate multiple myeloma from metastasis.

Methods

25 patients with metastasis and 18 patients with multiple myeloma underwent 3T MR imaging with DWI (b = 0, 800 s/mm²) were enrolled. They all had pathologically confirmed bone lesions and were in a treatment naïve state. Two readers who were blind of final diagnosis measured the average ADC (ADCav) and minimum ADC (ADCmin) on the DWI. They then estimated the diagnosis, based on the standard MR imaging and measured ADC values. Another reader performed histogram analysis on the whole tumor volume and obtained mean ADC (ADCvol), standard deviation (SDvol), skewness, and kurtosis. Comparison of the obtained values from DWI was performed by the t-test or Mann-Whitney U test. The receiver operating characteristic (ROC) curve with areas under the curve (AUC) was used to obtain the cut off values and to evaluate the diagnostic performance of the two readers.

Results

ADCav, ADCmin, and ADCvol of multiple myeloma were significantly lower than those of metastasis: ADCav, 752 μm²/sec versus 1081 μm²/sec; ADCmin, 704 μm²/sec vs 835 μm²/sec; ADCvol 761 μm²/sec vs 1184 μm²/sec (p < .001). In histogram analysis, ADC values of multiple myeloma showed narrow distribution than metastasis: SDvol, 144 vs 257 (p < .001). Areas under the receiver operating characteristic curve was significantly higher with additive DWI than standard MR alone: 0.762 vs 0.953; 0.706 vs 0.950 (p < .05) for two readers.

Conclusions

This study suggested that the addition of axial DWI to standard MR imaging can be helpful to diagnose multiple myeloma from metastasis at 3T.

Whole-Body MR Imaging: The Novel, "Intrinsically Hybrid," Approach to Metastases, Myeloma, Lymphoma, in Bones and Beyond

Whole-body MR imaging (WB-MR imaging) has become a modality of choice for detecting bone metastases in multiple cancers, and bone marrow involvement by multiple myeloma or lymphoma. Combination of anatomic and functional sequences imparts an inherently hybrid dimension to this nonirradiating tool and extends the screening of malignancies outside the skeleton. WB-MR imaging outperforms bone scintigraphy and CT and offers an alternative to PET in many tumors by time of lesion detection and assessment of treatment response. Much work has been done to standardize procedures, optimize sequences, validate indications, confirm preliminary research into new applications, rendering clinical application more user-friendly.

Functional and molecular MRI of the bone marrow in multiple myeloma

MRI plays an important role in the management of patients with plasma cell neoplasms and has been recognized as a biomarker of malignancy in the novel criteria for the diagnosis of multiple myeloma. Functional and molecular MRI techniques such as diffusion-weighted imaging (spinal or whole body), intravoxel incoherent motion, and dynamic contrast enhanced MRI, provide additional information related to tumor cellularity and angiogenesis, which may have prognostic implications for patients with smoldering and symptomatic myeloma. These non-invasive functional techniques are also being evaluated as imaging biomarkers for response assessment in myeloma patients. The purpose of this article is to provide a comprehensive critical review on the current use and potential future applications of these advanced MRI techniques in multiple myeloma. In addition, we will address the technologies involved and describe the qualitative and quantitative characteristics of normal bone marrow with these techniques.

Implementing diffusion-weighted MRI for body imaging in prospective multicentre trials: current considerations and future perspectives

For body imaging, diffusion-weighted MRI may be used for tumour detection, staging, prognostic information, assessing response and follow-up. Disease detection and staging involve qualitative, subjective assessment of images, whereas for prognosis, progression or response, quantitative evaluation of the apparent diffusion coefficient (ADC) is required. Validation and qualification of ADC in multicentre trials involves examination of i) technical performance to determine biomarker bias and reproducibility and ii) biological performance to interrogate a specific aspect of biology or to forecast outcome. Unfortunately, the variety of acquisition and analysis methodologies employed at different centres make ADC values non-comparable between them. This invalidates implementation in multicentre trials and limits utility of ADC as a biomarker. This article reviews the factors contributing to ADC variability in terms of data acquisition and analysis. Hardware and software considerations are discussed when implementing standardised protocols across multi-vendor platforms together with methods for quality assurance and quality control. Processes of data collection, archiving, curation, analysis, central reading and handling incidental findings are considered in the conduct of multicentre trials. Data protection and good clinical practice are essential prerequisites. Developing international consensus of procedures is critical to successful validation if ADC is to become a useful biomarker in oncology.

KEY POINTS

• Standardised acquisition/analysis allows quantification of imaging biomarkers in multicentre trials. • Establishing "precision" of the measurement in the multicentre context is essential. • A repository with traceable data of known provenance promotes further research.

Serum high expression of miR-214 and miR-135b as novel predictor for myeloma bone disease development and prognosis

Multiple myeloma (MM) originates from malignant plasma cells, leading to multiple destructive lytic bone lesions that occur in more than 80% of MM patients. MicroRNAs have been reported to be involved in development of bone lesions in MM. However, the circulating microRNA as diagnostic and prognostic biomarkers for bone lesions has not been elucidated yet. In this study, we identified differentially expressed miRNAs that are potentially involved in myeloma-related bone disease in serum of MM patients. MiR-214 and miR-135b was shown to be increased in serum of MM patients with bone lesions. Serum level of miR-214 and miR-135b was highly correlated with the severity of lytic bone lesions and demonstrated as a diagnostic tool for identifying bone diseases based on results of a receiver operating characteristic analysis (ROC). In addition, patients with high levels of serum miR-214 had a dismal survival with significantly shortened progression free survival (PFS) and overall survival (OS). Interestingly, bisphosphonates treatment significantly extended PFS and OS in patients with higher level of miR-214 comparing to patients without bisphosphonates treatment. Taken together, our findings revealed the significance of circulating miR-214 and miR-135b levels in detection of bone disease and in prediction of prognosis of patients with multiple myeloma, suggesting its potential clinical applications. The result of this study also set the foundation for searching more circulating miRNA as biomarker for tumor bone lesions.

A prospective study comparing whole-body skeletal X-ray survey with 18F-FDG-PET/CT, 18F-NaF-PET/CT and whole-body MRI in the detection of bone lesions in multiple myeloma patients

Background

For decades, the most widely used imaging technique for myeloma bone lesions has been a whole-body skeletal X-ray survey (WBXR), but newer promising imaging techniques are evolving.

Purpose

To compare WBXR with the advanced imaging techniques 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT), 18F-sodium fluoride (NaF) PET/CT and whole-body magnetic resonance imaging (WB-MRI) in the detection of myeloma bone lesions.

Material and Methods

Fourteen patients with newly diagnosed multiple myeloma were prospectively enrolled. In addition to WBXR, all patients underwent FDG-PET/CT, NaF-PET/CT, and WB-MRI. Experienced specialists performed blinded readings based on predefined anatomical regions and diagnostic criteria.

Results

In a region-based analysis, a two-sided ANOVA test showed that the extent of detected skeletal disease depends on the scanning technique (P < 0.0001). Tukey’s multiple comparison test revealed that WB-MRI on average detects significantly more affected regions than WBXR (P < 0.005), FDG-PET/CT (P < 0.0001), and NaF-PET/CT (P < 0.05). In a patient-based analysis, a Cochran’s Q test showed that there are no significant differences in the proportion of patients with bone disease detected by the different scanning techniques (P = 0.23). Determination of intrareader variability resulted in Kappa coefficients corresponding to moderate (FDG-PET/CT) and substantial agreement (WB-MRI, WBXR, NaF-PET/CT).

Conclusion

WB-MRI detects on average significantly more body regions indicative of myeloma bone disease compared to WBXR, FDG-PET/CT, and NaF-PET/CT. The lack of significance in the patient-based analysis is most likely due to the small number of study participants.

Diagnostic Advances in Multiple Myeloma

There have been several advances in the diagnosis of multiple myeloma (MM) in recent years. Serum free light chains have improved the ability to diagnose light chain MM; however, there are still difficulties in the serologic diagnosis of MM in some cases, particularly IgA MM. A novel heavy/light chain assay is able to improve the accuracy of diagnosis in these cases. Free light chains may also improve the diagnosis of extramedullary disease in difficult cases such as disease involving the central nervous system, pleura, or ascites. Advances in imaging such as whole body low-dose computed tomography (CT) whole body magnetic resonance imaging (MRI), and positron emission tomography/computed tomography (PET/CT) have improved sensitivity in identifying lytic bone lesions, which would enable earlier treatment, and monitoring of osseous disease particularly in non- or oligosecretory disease. New techniques such as fused PET/MRI may further enhance the diagnosis of both bone lesions and extramedullary disease.

[Role of whole-body diffusion weighted imaging (WB-DWI) in the diagnosis and monitoring of newly diagnosed multiple myeloma]

目的

探讨磁共振全身弥散加权成像（WB-DWI）在初诊多发性骨髓瘤（MM）患者诊断和监测中的应用价值。

方法

收集2012年9月至2016年1月收治的107例初诊MM患者的临床资料，分析其中治疗前行WB-DWI检查的60例患者的结果，探讨WB-DWI在MM诊断和监测中的作用。

结果

60例患者中有57例均发现程度不等的骨质破坏病灶，WB-DWI阳性检出率为95.0%（57/60）。MM相关的骨破坏多累及中轴骨，以肋骨、脊柱及骨盆骨多见，肋骨为最易受累部位，检出率为96.5%（55/57）。有13例患者初诊时CT检查未发现骨质破坏，但行WB-DWI检查发现相同部位有弥散受限病灶影。8例患者治疗前后均行WB-DWI检查，结果显示8例患者治疗前最大病灶的中位表观弥散系数（ADC）值为0.984×10⁻³mm²/s；治疗后为1.142×10⁻³mm²/s，治疗后最大病灶的中位ADC值较治疗前高，且均高于正常值[（0.516±0.180）×10⁻³mm²/s]；诱导治疗后WB-DWI检查结果与临床疗效相符。

结论

WB-DWI在诊断和监测MM中起重要作用，其诊断敏感性优于CT；诱导治疗后的WB-DWI检查结果与患者的临床疗效有一定的相关性，可用于疾病监测。

The Role of Imaging in the Treatment of Patients With Multiple Myeloma in 2016

The novel criteria for the diagnosis of symptomatic multiple myeloma have revealed the value of modern imaging for the management of patients with myeloma. Whole-body low-dose CT (LDCT) has increased sensitivity over conventional radiography for the detection of osteolytic lesions, and several myeloma organizations and institutions have suggested that whole-body LDCT should replace conventional radiography for the work-up of patients with myeloma. MRI is the best imaging method for the depiction of marrow infiltration by myeloma cells. Whole-body MRI (or at least MRI of the spine and pelvis if whole-body MRI is not available) should be performed for all patients with smoldering multiple myeloma with no lytic lesions to look for occult disease, which may justify treatment. In addition, MRI accurately illustrates the presence of plasmacytomas, spinal cord, and/or nerve compression for surgical intervention or radiation therapy; it is also recommended for the work-up of solitary bone plasmacytoma, and it may distinguish malignant from benign fractures (which is very important in cases of patients in biochemical remission with no other signs of progression). Diffusion weighted imaging (DWI) seems to improve MRI diagnosis in patients with myeloma. PET/CT is a functional imaging technique, more sensitive than conventional radiography for the detection of lytic lesions, which probably allows better definition of complete response and minimal residual disease compared with all other imaging methods. PET/CT has shown the best results in the follow-up of patients with myeloma and has an independent prognostic value both at diagnosis and following treatment. PET/CT can also be used for the work-up of solitary bone plasmacytoma and nonsecretory myeloma.

Whole body magnetic resonance imaging in newly diagnosed multiple myeloma: early changes in lesional signal fat fraction predict disease response

Cross-sectional imaging techniques are being increasingly used for disease evaluation in patients with multiple myeloma. Whole body magnetic resonance imaging (WB-MRI) scanning is superior to plain radiography in baseline assessment of patients but changes following treatment have not been systematically explored. We carried out paired WB-MRI scans in 21 newly diagnosed patients prior to, and 8-weeks after, starting chemotherapy, and analysed stringently selected focal lesions (FLs) for parametric changes. A total of 323 FLs were evaluated, median 20 per patient. At 8 weeks, there was a reduction in estimated tumour volume (eTV), and an increase in signal fat fraction (sFF) and apparent diffusion coefficient (ADC) in the group as a whole (P < 0·001). Patients who achieved complete/very good partial response (CR/VGPR) to induction had a significantly greater increase in sFF compared to those achieving ≤ partial response (PR; P = 0·001). When analysed on a per-patient basis, all patients achieving CR/VGPR had a significant sFF increase in their FL's, in contrast to patients achieving ≤PR. sFF changes in patients reaching maximal response within 100 days (fast responders) were greater compared to slow responders (P = 0·001). Receiver Operator Characteristic analysis indicated that sFF changes at 8 weeks were the best biomarker (area under the Curve 0·95) for an inferior response (≤PR). We conclude that early lesional sFF changes may provide important information on depth of response, and are worthy of further prospective study.

Nuclear medicine imaging of multiple myeloma, particularly in the relapsed setting

Multiple myeloma (MM) is characterized by a monoclonal plasma cell population in the bone marrow. Lytic lesions occur in up to 90 % of patients. For many years, whole-body X-ray (WBX) was the method of choice for detecting skeleton abnormalities. However, the value of WBX in relapsing disease is limited because lesions persist post-treatment, which restricts the capacity to distinguish between old, inactive skeletal lesions and new, active ones. Therefore, alternative techniques are necessary to visualize disease activity. Modern imaging techniques such as magnetic resonance imaging, positron emission tomography and computed tomography offer superior detection of myeloma bone disease and extramedullary manifestations. In particular, the properties of nuclear imaging enable the identification of disease activity by directly targeting the specific cellular properties of malignant plasma cells. In this review, an overview is provided of the effectiveness of radiopharmaceuticals that target metabolism, surface receptors and angiogenesis. The available literature data for commonly used nuclear imaging tracers, the promising first results of new tracers, and our pilot work indicate that a number of these radiopharmaceutical applications can be used effectively for staging and response monitoring of relapsing MM patients. Moreover, some tracers can potentially be used for radio immunotherapy.

Diffusion-weighted imaging and the skeletal system: a literature review

Diffusion-weighted imaging (DWI) is a magnetic resonance imaging (MRI) sequence that has a well-established role in neuroimaging, and is increasingly being utilised in other clinical contexts, including the assessment of various skeletal disorders. It utilises the variability of Brownian motion of water molecules; the differing patterns of water molecular diffusion in various biological tissues help determine the contrast obtained in DWI. Although early research on the clinical role of DWI focused mainly on the field of neuroimaging, there are now more studies demonstrating the promising role DWI has in the diagnosis and monitoring of various osseous diseases. DWI has been shown to be useful in assessing a patient's skeletal tumour burden, monitoring the post-chemotherapy response of various bony malignancies, detecting hip ischaemia in patients with Legg-Calvé-Perthes disease, as well as determining the quality of repaired articular cartilage. Despite its relative successes, DWI has several limitations, including its limited clinical value in differentiating chondrosarcomas from benign bone lesions, as well as osteoporotic vertebral compression fractures from compression fractures due to malignancy. This literature review aims to provide an overview of the recent developments in the use of DWI in imaging the skeletal system, and to clarify the role of DWI in assessing various osseous diseases.

Whole-body MRI in patients with lymphoma: collateral findings

PURPOSE

To assess the incidence of collateral findings detected on whole-body magnetic resonance (WB-MRI) scans performed on patients with lymphoma.

MATERIALS AND METHODS

114 patients (65 male; median age 45.2 years, range 15-86) with histologically confirmed lymphoma (47 Hodgkin, 67 Non-Hodgkin) underwent WB-MRI. The collateral findings were classified into three classes, according to their clinical significance, as follows: not or low significant (class 1), moderately or potentially significant (class 2), and significant (class 3). A Chi-square (χ (2)) test was performed to assess the statistical significance of differences in the incidence of collateral findings based on age (≤50 and >50 years old), gender and histology (Hodgkin and Non-Hodgkin Lymphoma).

RESULTS

Ninety-one of 114 patients (79.8 %) had one or more incidental findings on WB-MRI. Collateral findings were more frequent in class 1 (43 %); abnormalities found in 35 patients (30.7 %) were considered potentially significant, whereas seven patients (6.1 %) demonstrated significant collateral findings requiring immediate treatment or further diagnostic evaluation. Collateral findings were more frequent in subjects over 50 years old compared to those of 50 years old or younger; differences were statistical significant (χ (2) = 8.42, p < 0.05). There were not statistically significant differences related to gender (χ (2) = 0.17, p > 0.05) and histology (χ (2) = 0.24, p > 0.05).

CONCLUSION

WB-MRI is an attractive procedure that allows to detect incidental abnormalities of organs not involved by disease offering the opportunity to obtain an early diagnosis of asymptomatic life-threatening diseases.

Application of (18)F-FDG PET and diffusion weighted imaging (DWI) in multiple myeloma: comparison of functional imaging modalities

Aim of this prospective study was to assess the sensitivity of positron emission tomography (PET) and diffusion-weighted imaging (DWI) in detecting multiple myeloma (MM) lesions, using the well-established morphologic modalities magnetic resonance imaging (MRI) and computed tomography (CT) as the standard of reference (RS). The study included 24 MM patients (15 newly diagnosed, 9 pre-treated). All underwent (18)F-FDG PET/CT and wholebody DWI. The findings in PET and DWI were compared to matching imaging findings in combined non-enhanced T1w, fat-saturated T2w (TIRM)- MRI, and low-dose CT. Patient-based analysis revealed that 15/24 patients (10 primary MM, 5 pre-treated) had myeloma lesions according to our RS. PET was positive in 13/24 patients (11 primary MM, 2 pre-treated) and DWI in 18/24 patients (12 primary MM, 6 pre-treated). Lesion-based analysis demonstrated 128 MM lesions, of which PET depicted 60/128 lesions (sensitivity 47%), while DWI depicted 99/128 lesions (sensitivity 77%). Further analysis including only the 15 untreated MM patients revealed a sensitivity of 90% for both PET and DWI and an overall concordance of PET and DWI of 72%. In conclusion, DWI was more sensitive than (18)F-FDG PET in detecting myeloma lesions in a mixed population of primary and pre-treated MM patients. However, (18)F-FDG PET and DWI demonstrated equivalent sensitivities in the sub-population of primary, untreated MM patients. This higher sensitivity of DWI in pre-treated patients may be due to the fact that (18)F-FDG PET becomes negative earlier in the course of treatment in contrary to MRI, in which already treated lesions can remain visible.

Whole body diffusion weighted MRI--a new view of myeloma

The recent consensus statement from the International Myeloma Working Group has introduced the role of whole body (WB) magnetic resonance imaging (MRI) into the management pathway for patients with multiple myeloma. The speed, coverage and high sensitivity of WB diffusion weighted (DW)-MRI and the unique capability to quantify both burden of disease and response to treatment has led to increasing implementation at leading centres worldwide for imaging malignant marrow disease, both primary and metastatic. WB DW-MRI is likely to have a significant impact on management decisions and pathways for patients with multiple myeloma. This review will introduce the basic principles of DW-MRI, present current evidence for patients with myeloma and will discuss practicalities and exciting future applications.