Patients with plasma cell disorders examined at whole-body dynamic contrast-enhanced MR imaging: initial experience

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.

Review of diffusion-weighted imaging and dynamic contrast-enhanced MRI for multiple myeloma and its precursors (monoclonal gammopathy of undetermined significance and smouldering myeloma)

The last decades, increasing research has been conducted on dynamic contrast-enhanced and diffusion-weighted MRI techniques in multiple myeloma and its precursors. Apart from anatomical sequences which are prone to interpretation errors due to anatomical variants, other pathologies and subjective evaluation of signal intensities, dynamic contrast-enhanced and diffusion-weighted MRI provide additional information on microenvironmental changes in bone marrow and are helpful in the diagnosis, staging and follow-up of plasma cell dyscrasias. Diffusion-weighted imaging provides information on diffusion (restriction) of water molecules in bone marrow and in malignant infiltration. Qualitative evaluation by visually assessing images with different diffusion sensitising gradients and quantitative evaluation of the apparent diffusion coefficient are studied extensively. Dynamic contrast-enhanced imaging provides information on bone marrow vascularisation, perfusion, capillary resistance, vascular permeability and interstitial space, which are systematically altered in different disease stages and can be evaluated in a qualitative and a (semi-)quantitative manner. Both diffusion restriction and abnormal dynamic contrast-enhanced MRI parameters are early biomarkers of malignancy or disease progression in focal lesions or in regions with diffuse abnormal signal intensities. The added value for both techniques lies in better detection and/or characterisation of abnormal bone marrow otherwise missed or misdiagnosed on anatomical MRI sequences. Increased detection rates of focal lesions or diffuse bone marrow infiltration upstage patients to higher disease stages, provide earlier access to therapy and slower disease progression and allow closer monitoring of high-risk patients. Despite promising results, variations in imaging protocols, scanner types and post-processing methods are large, thus hampering universal applicability and reproducibility of quantitative imaging parameters. The myeloma response assessment and diagnosis system and the international myeloma working group provide a systematic multicentre approach on imaging and propose which parameters to use in multiple myeloma and its precursors in an attempt to overcome the pitfalls of dynamic contrast-enhanced and diffusion-weighted imaging.Single sentence summary statementDiffusion-weighted imaging and dynamic contrast-enhanced MRI provide important additional information to standard anatomical MRI techniques for diagnosis, staging and follow-up of patients with plasma cell dyscrasias, although some precautions should be taken on standardisation of imaging protocols to improve reproducibility and application in multiple centres.

Optimization of whole-body 2-[18F]FDG-PET/MRI imaging protocol for the initial staging of patients with myeloma

OBJECTIVE

To determine the optimal 2-[¹⁸F]FDG-PET/MRI imaging protocol for the initial staging of patients with suspected or confirmed multiple myeloma.

METHODS

Radiologists and nuclear medicine specialists reviewed all PET/MRI exams of 104 patients with a monoclonal gammopathy (MG). The presence of focal and diffuse bone marrow involvement (BMI) was assessed using 4 different image datasets: WB-MRI, PET, WB-PET/MRI, and WB-DCE-PET/MRI. A reference standard was established by a panel review of all baseline and follow-up imaging, and biological and pathological information. The diagnostic performance for each image dataset to detect BMI was evaluated and compared (Fisher's exact test).

RESULTS

Sensitivity, specificity, and accuracy for focal BMI of WB-MRI was 87%, 97%, and 92%; of PET was 78%, 97%, and 95%; of WB-PET/MRI was 93%, 97%, and 95%; and of WB-DCE-PET/MRI was 93%, 97%, and 95%, respectively. WB-PET/MRI and WB-DCE-PET/MRI were statistically superior to PET (p = 0.036) without decreasing specificity. The sensitivity, specificity, and accuracy of WB-MRI for diffuse BMI detection was 91%, 80%, and 85%; of 3DT1-PET was 53%, 89%, and 74%; of WB-PET/MRI was 98%, 66%, and 79%; and of WB-DCE-PET/MRI was 98%, 59%, and 75%, respectively. PET lacked sensitivity compared to all other dataset studies (p < 0.0001). WB-MRI had the best accuracy without reaching statistical significance when compared to the other datasets.

CONCLUSION

The WB-PET/MRI dataset including T1 and T2 Dixon, WB-DWI, and PET images provides optimal diagnostic performance to detect both focal lesions and diffuse BMI, with limited added value of WB-DCE for baseline staging of patients with MG. Key Points • The combination of morphological and functional MRI sequences and metabolic (2-[¹⁸F]FDG-PET) images increases the diagnostic performance of PET/MRI to detect focal bone lesions. • The adjunction of dynamic contrast-enhanced sequences did not improve diagnostic performance.

Whole-Body Functional MRI and PET/MRI in Multiple Myeloma

Simple Summary

Whole-body magnetic resonance imaging (MRI) is recognized as the most sensitive imaging technique for the detection of bone marrow infiltration, and was therefore, recently included in the new diagnostic myeloma criteria, as proposed by the International Myeloma Working Group. The use of diffusion-weighted MRI further improved the performances of whole-body MRI in the setting of multiple myeloma, and its systematic implementation in general clinical practice is now recommended. Whole-body, dynamic, contrast-enhanced MRI might provide further information on lesions vascularity and might help evaluate response to treatment. Hybrid PET/MRI might act as the optimal imaging modality, owing to the association of the best techniques for both detecting bone marrow involvement and evaluating treatment response, providing one-stop-shop imaging in a whole-body scale. This review provides an overview on the value of whole-body MRI, including diffusion-weighted and dynamic contrast-enhanced MRI and whole-body ¹⁸F-FDG PET/MRI in diagnosis, staging, and response evaluation in multiple myeloma.

Abstract

Bone disease is one of the major features of multiple myeloma (MM), and imaging has a pivotal role in both diagnosis and follow-up. Whole-body magnetic resonance imaging (MRI) is recognized as the gold standard for the detection of bone marrow involvement, owing to its high sensitivity. The use of functional MRI sequences further improved the performances of whole-body MRI in the setting of MM. Whole-body diffusion-weighted (DW) MRI is the most attractive functional technique and its systematic implementation in general clinical practice is now recommended by the International Myeloma Working Group. Whole-body dynamic contrast-enhanced (DCE) MRI might provide further information on lesions vascularity and help evaluate response to treatment. Whole Body PET/MRI is an emerging hybrid imaging technique that offers the opportunity to combine information on morphology, fat content of bone marrow, bone marrow cellularity and vascularization, and metabolic activity. Whole-body PET/MRI allows a one-stop-shop examination, including the most sensitive technique for detecting bone marrow involvement, and the most recognized technique for treatment response evaluation. This review aims at providing an overview on the value of whole-body MRI, including DW and DCE MRI, and combined whole-body ¹⁸F-FDG PET/MRI in diagnosis, staging, and response evaluation in patients with MM.

Whole-body magnetic resonance imaging (WB-MRI) in oncology: recommendations and key uses

The past decade has witnessed a growing role and increasing use of whole-body magnetic resonance imaging (WB-MRI). Driving these successes are developments in both hardware and software that have reduced overall examination times and significantly improved MR imaging quality. In addition, radiologists and clinicians have continued to find promising new applications of this innovative imaging technique that brings together morphologic and functional characterization of tissues. In oncology, the role of WB-MRI has expanded to the point of being recommended in international guidelines for the assessment of several cancer histotypes (multiple myeloma, melanoma, prostate cancer) and cancer-prone syndromes (Li-Fraumeni and hereditary paraganglioma-pheochromocytoma syndromes). The literature shows growing use of WB-MRI for the staging and follow-up of other cancer histotypes and cancer-related syndromes (including breast cancer, lymphoma, neurofibromatosis, and von Hippel-Lindau syndromes). The main aim of this review is to examine the current scientific evidence for the use of WB-MRI in oncology.

MRI protocol optimization for quantitative DCE-MRI of the spine

PURPOSE

In this study we systematically investigated different Dynamic Contrast Enhancement (DCE)-MRI protocols in the spine, with the goal of finding an optimal protocol that provides data suitable for quantitative pharmacokinetic modelling (PKM).

MATERIALS AND METHODS

In 13 patients referred for MRI of the spine, DCE-MRI of the spine was performed with 2D and 3D MRI protocols on a 3T Philips Ingenuity MR system. A standard bolus of contrast agent (Dotarem - 0.2ml/kg body weight) was injected intravenously at a speed of 3ml/s. Different techniques for acceleration and motion compensation were tested: parallel imaging, partial-Fourier imaging and flow compensation. The quality of the DCE MRI images was scored on the basis of SNR, motion artefacts due to flow and respiration, signal enhancement, quality of the T₁ map and of the arterial input function, and quality of pharmacokinetic model fitting to the extended Tofts model.

RESULTS

Sagittal 3D sequences are to be preferred for PKM of the spine. Acceleration techniques were unsuccessful due to increased flow or motion artefacts. Motion compensating gradients failed to improve the DCE scans due to the longer echo time and the T₂* decay which becomes more dominant and leads to signal loss, especially in the aorta. The quality scoring revealed that the best method was a conventional 3D gradient-echo acquisition without any acceleration or motion compensation technique. The priority in the choice of sequence parameters should be given to reducing echo time and keeping the dynamic temporal resolution below 5s. Increasing the number of acquisition, when possible, helps towards reducing flow artefacts. In our setting we achieved this with a sagittal 3D slab with 5 slices with a thickness of 4.5mm and two acquisitions.

CONCLUSION

The proposed DCE protocol, encompassing the spine and the descending aorta, produces a realistic arterial input function and dynamic data suitable for PKM.

Intravoxel Incoherent Motion Diffusion-weighted Imaging of Multiple Myeloma Lesions: Correlation with Whole-Body Dynamic Contrast Agent-enhanced MR Imaging

PURPOSE

To correlate intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) parameters with the enhancement patterns of bone marrow and focal lesion obtained on whole-body (WB) dynamic contrast agent-enhanced (DCE) magnetic resonance (MR) images in patients with stage-III multiple myeloma (MM) before and after systemic therapy.

MATERIALS AND METHODS

Twenty-seven patients with MM were retrospectively included in this institutional review board-approved study. Requirement for written informed consent was waived. All patients underwent WB DCE MR imaging before treatment and 18 patients underwent repeat MR imaging 3 months after treatment. A transverse IVIM DWI sequence with 10 b values (0, 10, 20, 30, 50, 80, 100, 200, 400, and 800 sec/mm(2)) was acquired within bone marrow and focal lesions. The IVIM parameters (perfusion fraction [f], molecular diffusion coefficient [D], and perfusion-related D [D*]) and apparent diffusion coefficient (ADC) were extracted for both focal lesions and bone marrow and correlated with focal lesions and maximal bone marrow enhancement (BMEmax) (Spearman correlation coefficient) at baseline and at follow-up (Wilcoxon signed-rank test).

RESULTS

D and ADC values positively correlated with BMEmax (r = 0.7, P < .001; and r = 0.455, P = .0435, respectively). Patients with increased BMEmax showed significantly increased ADC and D within bone marrow versus patients who did not have increased BMEmax (ADC, 0.67 × 10(-3) mm(2)/sec vs 0.54 × 10(-3) mm(2)/sec, P = .03; D, 0.58 × 10(-3) mm(2)/sec vs 0.42 × 10(-3) mm(2)/sec, P < .001). Within focal lesions, f was the maximum in lesions that showed enhancement followed by washout. After treatment in good responders, the significant decrease in maximal enhancement value of focal lesions (baseline vs after treatment, 213.9% ± 78.7 [standard deviation] vs 131% ± 53.6, respectively; P < .001) was accompanied by a significant decrease in f (baseline vs after treatment, 11% ± 3.8 vs 5.8% ± 4.7, respectively; P < .001).

CONCLUSION

Diffuse bone marrow involvement is associated with increased D. Hypervascular focal lesions with high maximal enhancement value of focal lesions also show high f value. Likewise, the decreased maximal enhancement value of focal lesions after treatment is accompanied by decreased f.

(11)C-acetate as a new biomarker for PET/CT in patients with multiple myeloma: initial staging and postinduction response assessment

PURPOSE

We investigated the potential value of (11)C-acetate (ACT) PET/CT in characterizing multiple myeloma (MM) compared with (18)F-FDG PET/CT. Bone marrow histological and whole-body (WB) MRI findings served as the reference standards.

METHODS

In this prospective study, 15 untreated MM patients (10 men and 5 women, age range 48-69 years) underwent dual-tracer (11)C-ACT and (18)F-FDG PET/CT and WB MRI for pretreatment staging, and 13 of them had repeated examinations after induction therapy. Diffuse and focal bone marrow uptake was assessed by visual and quantitative analyses, including measurement of the maximum standardized uptake value (SUVmax). Between-group differences and correlations were assessed with the Mann-Whitney U test and the Pearson test.

RESULTS

At staging, all 15 patients had diffuse myeloma involvement upon bone marrow examination with 30-90 % of plasma cell infiltrates. Diffuse infiltration was detected in all of them (100 %) using (11)C-ACT with a positive correlation between bone marrow uptake values and percentages of plasma cell infiltrates (r = +0.63, p=0.01). In contrast, a diagnosis of diffuse infiltration could be established using (18)F-FDG in only six patients (40 %). Focal lesions were shown in 13 patients on both (11)C-ACT PET/CT and WB MRI, and in 10 patients on (18)F-FDG PET/CT. Focal lesions demonstrated (11)C-ACT uptake with a mean SUVmax of 11.4 ± 3.3 (range 4.6-19.6, n=59), which was significantly higher than the (18)F-FDG uptake (mean SUVmax 6.6 ± 3.1, range 2.3-13.7, n=29; p<0.0001). After treatment, the diffuse bone marrow (11)C-ACT uptake showed a mean SUVmax reduction of 66 % in patients with at least a very good partial response versus 34 % in those with at most a partial response only (p=0.01).

CONCLUSION

PET/CT using (11)C-ACT as a biomarker showed a higher detection rate for both diffuse and focal myeloma lesions at diagnosis than using (18)F-FDG, and may be valuable for response assessment.

Imaging of the entire cerebrospinal fluid volume with a multistation 3D SPACE MR sequence: feasibility study in patients with hydrocephalus

OBJECTIVES

To evaluate the feasibility of imaging the entire cerebrospinal fluid (CSF) volume using the SPACE MR sequence.

METHODS

The SPACE sequence encompassing the brain and spine was performed at 1.5 T in 12 healthy volunteers and 26 consecutive patients with hydrocephalus. Image contrast was estimated using difference ratios in signal intensity between CSF and its background. Segmentation of CSF was performed using geometrical features and a topological assumption of CSF shapes. Subarachnoid and ventricular CSF space volumes were assessed in volunteers and patients and linear discriminant analysis was performed.

RESULTS

Image contrast was 0.94 between the CSF and the brain and 0.90 between the CSF and the spinal cord. According to the phantom study, the accuracy of CSF volume measurement was 98.5 %. A clear distinction between patients and healthy volunteers was obtained using the linear discriminant analysis. Significant linear regression was found in healthy volunteers between ventricular (Vv) and the whole subarachnoid CSF volume (Vs) with Vv = 0.083 Vs.

CONCLUSIONS

Imaging of the entire CSF volume is feasible in healthy volunteers and patients with hydrocephalus. CSF volume can be obtained on a whole-body scale. This approach may be of use for the diagnosis and follow-up of patients with hydrocephalus.

KEY POINTS

• MRI assessment of CSF volume is feasible in healthy volunteers/hydrocephalus patients. • CSF volume can be obtained on a whole-body scale. • The ratio of subarachnoid and ventricular CSF is constant in healthy volunteers. • CSF linear discriminant analysis can distinguish between patients and healthy volunteers. • Entire CSF volume imaging is useful for diagnosing and following hydrocephalus.

Role of whole-body 64-slice multidetector computed tomography in treatment planning for multiple myeloma

PURPOSE

The authors evaluated the role of whole-body 64-slice multidetector computed tomography (WB-MDCT) in treatment planning for multiple myeloma.

MATERIAL AND METHODS

This was a prospective study of 28 consecutive patients with multiple myeloma (19 men, nine women; age range, 51-73 years; mean age, 60 years) who underwent WB-MDCT and conventional radiography (CR) of the skeleton. The images were interpreted for the presence of bony lesions, medullary lesions, fractures and extraosseous lesions. We evaluated any changes in treatment planning as a result of WB-MDCT findings.

RESULTS

WB-MDCT was superior to CR for detecting bony lesions (p=0.001), especially of the spine (p=0.001) and thoracic cage (p=0.006). WB-MDCT upstaged 14 patients, with a significant difference in staging (p=0.002) between WB-MDCT and CR. Medullary involvement either focal (n=6) or diffuse (n=3) had a positive correlation with the overall score (r=0.790) and stage (r=0.618) of disease. Spine fractures were better detected at WB-MDCT (n=4) than at CR (n=2). Extraosseous soft tissue lesions (n=7) were detected only at WB-MDCT. Findings detected at the WB-MDCT led to changes in the patient's treatment plan in 39% of cases. Upstaging of seven patients (25%) altered the medical treatment plan, and four of 28 (14%) patients required additional radiotherapy (7%) and vertebroplasty (7%).

CONCLUSIONS

We conclude that WB-MDCT has an impact on treatment planning and prognosis in patients with multiple myeloma, as it has high rate of detecting cortical and medullary bone lesions, spinal fracture and extraosseous lesions. This information may alter treatment planning in multiple myeloma due to disease upstaging and detection of spine fracture and extraosseous spinal lesions.

[Whole body functional MR imaging: hemato-oncologic applications]

Hemato-oncologic imaging combines anatomical and functional imaging data for optimal staging and follow-up of patients. It is currently possible to achieve high spatial resolution and functional evaluation at whole body MR imaging. Functional imaging may be achieved with two techniques: dynamic imaging following intravenous contrast injection and diffusion-weighted imaging. The purpose of this article is to demonstrate how both functional imaging techniques can be combined with whole body MR imaging for the evaluation of multiple myeloma and lymphomas.

Multiple myeloma treatment response assessment with whole-body dynamic contrast-enhanced MR imaging

PURPOSE

To compare posttreatment bone marrow changes at whole-body dynamic contrast material-enhanced magnetic resonance (MR) imaging with clinical response in patients with multiple myeloma (MM) and to determine if this technique can be used to assess treatment response in patients with MM.

MATERIALS AND METHODS

This study was approved by an institutional review board; all patients gave informed written consent. Thirty patients (21 men, nine women; mean age, 58 years +/- 10 [standard deviation]) underwent whole-body dynamic contrast-enhanced MR imaging before treatment, after induction chemotherapy (n = 30), and after autologous stem cell transplantation (ASCT) (n = 20). Maximal percentages of bone marrow (BME(max)) and focal lesion (FLE(max)) enhancement were assessed at each MR imaging examination. Clinical responses were determined on the basis of international uniform response criteria. Posttreatment changes in BME(max)and FLE(max)were compared with clinical response to therapy by using the Mann-Whitney U test. Receiver operating characteristic (ROC) analysis of posttreatment BME(max)was used to identify poor responders.

RESULTS

Eleven of 30 patients were good responders to induction chemotherapy; 16 of 20 patients were good responders to ASCT. After induction chemotherapy, mean BME(max)differed between good and poor responders (94.3% vs 138.4%, respectively; P = .02). With the exclusion of results from six examinations with focal lesions in which a poor clinical response was classified but BME(max)had normalized, a posttreatment BME(max)of more than 96.8% had 100% sensitivity for the identification of poor responders (specificity, 76.9%; area under the ROC curve, 0.90; P = .0001). Mean FLE(max)after induction chemotherapy did not differ between good and poor responders. Mean timing (ie, the number of postcontrast dynamic acquisitions where FLE(max)was observed) was significantly delayed in good responders compared with poor responders (4.7 vs 2.9, P < .0001). Post-ASCT MR imaging results correctly depicted all four clinically good responders whose disease subsequently progressed.

CONCLUSION

With quantitative analysis of BME(max)and the timing of FLE(max), whole-body dynamic contrast-enhanced MR imaging can be used to assess treatment response in patients with MM.

Multiple myeloma

Advances in the imaging and treatment of multiple myeloma have occurred over the past decade. This article summarises the current status and highlights how an understanding of both is necessary for optimum management.