Whole-body MRI to assess bone involvement in prostate cancer and multiple myeloma: comparison of the diagnostic accuracies of the T1, short tau inversion recovery (STIR), and high b-values diffusion-weighted imaging (DWI) sequences

Computer-aided diagnosis of skeletal metastases in multi-parametric whole-body MRI

The confident detection of metastatic bone disease is essential to improve patients' comfort and increase life expectancy. Multi-parametric magnetic resonance imaging (MRI) has been successfully used for monitoring of metastatic bone disease, allowing for comprehensive and holistic evaluation of the total tumour volume and treatment response assessment. The major challenges of radiological reading of whole-body MRI come from the amount of data to be reviewed and the scattered distribution of metastases, often of complex shapes. This makes bone lesion detection and quantification demanding for a radiologist and prone to error. Additionally, whole-body MRI are often corrupted with multiple spatial and intensity distortions, which further degrade the performance of image reading and image processing algorithms. In this work we propose a fully automated computer-aided diagnosis system for the detection and segmentation of metastatic bone disease using whole-body multi-parametric MRI. The system consists of an extensive image preprocessing pipeline aiming at enhancing the image quality, followed by a deep learning framework for detection and segmentation of metastatic bone disease. The system outperformed state-of-the-art methodologies, achieving a detection sensitivity of 63% with a mean of 6.44 false positives per image, and an average lesion Dice coefficient of 0.53. A provided ablation study performed to investigate the relative importance of image preprocessing shows that introduction of region of interest mask and spatial registration have a significant impact on detection and segmentation performance in whole-body MRI. The proposed computer-aided diagnosis system allows for automatic quantification of disease infiltration and could provide a valuable tool during radiological examination of whole-body MRI.

Evaluation of MRI in the diagnostic accuracy of extrahepatic metastases in neuroendocrine tumors in comparison with the reference standard somatostatin-receptor-PET/CT

Purpose

The aim of this study was to compare the diagnostic performance of different sets of MR sequences in detecting extrahepatic disease of NETs on routine liver magnetic resonance imaging (MRI).

Method

One hundred twenty-seven patients with NETs with and without hepatic and extrahepatic metastases who underwent liver MRI and SSTR-PET/CT were retrospectively analyzed. Two radiologists evaluated in consensus in four sessions: (1) non-contrast T1w+T2w (NC), (2) NC+DWI, (3) NC+ contrast-enhanced T1w (CE), and (4) NC+DWI+CE the presence and number of metastases (lymph nodes, bone, peritoneal surface, lung base, and abdominal organ). Sensitivity, specificity, positive, and negative predictive value for detection of metastases were calculated for each session in a patient-based manner; detection and error rates were calculated for lesion-based analysis. Comparison between the MR-sessions and positron emission tomography-computed tomography (PET/CT) was performed with the McNemar test.

Results

Regarding all 1,094 lesions detected in PET/CT, NC+DWI, and NC, CE+DWI identified most true-positive lesions 779 (71%) and 775 (71%), respectively. Patient-based analysis revealed significantly higher sensitivity by NC+DWI (85%) than NC and NC+CE (p = 0.011 and 0.004, respectively); the highest specificity was reached by NC+CE+DWI (100%). Site-based analysis revealed highest detection rates for lymph node metastases for NC+DWI and NC, CE+DWI (73 and 76%, respectively); error rates were lower for NC, CE+DWI with 5% compared with 17% (NC+DWI). Detection rates for bone metastases were similarly high in NC+DWI and NC, CE+DWI (75 and 74%, respectively), while CE showed no benefit. For peritoneal metastases highest sensitivity was reached by NC+DWI (67%).

Conclusion

The combination of NC+DWI showed better sensitivities than the combination of NC+CE. NC+DWI showed similar, sometimes even better sensitivities than NC+CE+DWI, but with lower specificities.

Diagnostic value of whole -body diffusion weighted imaging added to bone scan in early diagnosis of bone metastases in breast cancer patients

Background

Metastases to the bones are a frequent location of metastasis in advanced breast cancer and are responsible for substantial morbidity and healthcare expenses. Imaging has been crucial in directing patient therapy for decades, contributing to the staging and response evaluation of the skeleton. This research aimed to assess the diagnostic value of whole-body magnetic resonance imaging with diffusion-weighted imaging added to radionuclide bone scans for early diagnosis of bone metastases in breast cancer patients.

Results

The study was a prospective observational cohort study performed on 20 patients with breast cancer and suspected bone metastases. The patients were evaluated first by obtaining a detailed personal history. Laboratory tests, including CBC, liver, and kidney function tests were assessed. All patients were examined by diffusion-weighted whole-body MRI (DWIBS; diffusion-weighted imaging with background body signal suppression) images and bone scintigraphy after intravenous injection of 20 mci of technetium-99m (99mTc) methylene diphosphonate using a dual head gamma camera. The total number of lesions detected by bone scan was 74, and 75 lesions were seen by DWIBS. Twenty-four lesions were missed by bone scan and detected by DWIBS. Fourteen lesions were detected by bone scan and found free by DWIBS examination in the spine and pelvic bones.

Conclusions

Whole body DWIBS seems to be a promising method of imaging in detecting bone metastases from breast cancer that could be used complementary to the traditional bone scan for more accurate diagnosis and staging of the tumor, helping to determine the most appropriate protocol of management.

Evaluating prostate cancer bone metastasis using accelerated whole-body isotropic 3D T1-weighted Dixon MRI with compressed SENSE: a feasibility study

OBJECTIVES

The study aimed to assess the efficiency of whole-body high-resolution compressed sensing-sensitivity encoding isotropic T1-Weighted Dixon (CSI-T1W-Dixon) scans in evaluating bone metastasis.

METHODS

Forty-five high-risk prostate cancer patients with bone metastases were enrolled prospectively and underwent whole-body MRI sequences, which included the following: pre- and post-contrast CSI-T1W-Dixon and conventional multi-planar T1-Weighted Dixon (CMP-T1W-Dixon) (coronal, sagittal, and axial scans), short tau inversion recovery (STIR), and DWI. Comparison between the CMP-T1W-Dixon and CSI-T1W-Dixon images was done for the subjective image quality, the quantitative contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR). Furthermore, the diagnostic performance based on per-lesion and per-patient basis utilizing non-contrast T1-weighted (T1)/T1+ contrasted T1-weighted (T1C)/T1 + T1C + STIR + DWI sequences was compared between the CSI-T1W-Dixon and CMP-T1W-Dixon methods using reference standards (combining biopsy data and 6-month imaging follow-up).

RESULT

The CSI-T1W-Dixon images produced fewer image artifacts in the axial and coronal planes compared to the CMP-T1W-Dixon images. Also, the CSI-T1W-Dixon images provided better a CNR in fat-only images of all three planes and water-only images of the axial plane (p < 0.05). The CSI-T1W-Dixon showed a higher sensitivity than the CMP-T1W-Dixon techniques in analyzing T1-only images on a per-lesion basis (82.7% vs. 53.8% for sensitivity, p = 0.03). On a per-patient basis, no difference was found in the diagnostic capacity between the CSI-T1W-Dixon and CMP-T1W-Dixon sequences either alone or in combinations (p = 0.57-1).

CONCLUSION

High-resolution CSI-T1W-Dixon with higher image quality and diagnostic capacity can replace the CMP-T1W-Dixon method in evaluating bone metastasis in clinical practice.

KEY POINTS

• Compressed sensing isotropic acquisition for 3D T1-weighted Dixon images can improve the image quality with fewer artifacts compared to the anisotropic multiplanar acquisition. • Compressed sensing isotropic acquisition can save 67% of scanning time compared to anisotropic multiplanar acquisition. • Compressed sensing isotropic 3D T1-weighted Dixon images can offer better diagnostic performance with higher sensitivity compared to anisotropic multiplanar images.

Whole body imaging in musculoskeletal oncology: when, why, and how

The use of whole-body imaging has become increasingly popular in oncology due to the possibility of evaluating total tumor burden with a single imaging study. This is particularly helpful in cases of widespread disease where dedicated regional imaging would make the evaluation more expensive, time consuming, and prone to more risks. Different techniques can be used, including whole-body MRI, whole-body CT, and PET-CT. Common indications include surveillance of cancer predisposing syndromes, evaluation of osseous metastases and clonal plasma cell disorders such as multiple myeloma, and evaluation of soft tissue lesions, including peripheral nerve sheath tumors. This review focuses on advanced whole-body imaging techniques and their main uses in musculoskeletal oncology.

A Multicompartmental Diffusion Model for Improved Assessment of Whole-Body Diffusion-weighted Imaging Data and Evaluation of Prostate Cancer Bone Metastases

Purpose To develop a multicompartmental signal model for whole-body diffusion-weighted imaging (DWI) and apply it to study the diffusion properties of normal tissue and metastatic prostate cancer bone lesions in vivo. Materials and Methods This prospective study (ClinicalTrials.gov: NCT03440554) included 139 men with prostate cancer (mean age, 70 years ± 9 [SD]). Multicompartmental models with two to four tissue compartments were fit to DWI data from whole-body scans to determine optimal compartmental diffusion coefficients. Bayesian information criterion (BIC) and model-fitting residuals were calculated to quantify model complexity and goodness of fit. Diffusion coefficients for the optimal model (having lowest BIC) were used to compute compartmental signal-contribution maps. The signal intensity ratio (SIR) of bone lesions to normal-appearing bone was measured on these signal-contribution maps and on conventional DWI scans and compared using paired t tests (α = .05). Two-sample t tests (α = .05) were used to compare compartmental signal fractions between lesions and normal-appearing bone. Results Lowest BIC was observed from the four-compartment model, with optimal compartmental diffusion coefficients of 0, 1.1 × 10^-3, 2.8 × 10^-3, and >3.0 ×10^-2 mm²/sec. Fitting residuals from this model were significantly lower than from conventional apparent diffusion coefficient mapping (P < .001). Bone lesion SIR was significantly higher on signal-contribution maps of model compartments 1 and 2 than on conventional DWI scans (P < .008). The fraction of signal from compartments 2, 3, and 4 was also significantly different between metastatic bone lesions and normal-appearing bone tissue (P ≤ .02). Conclusion The four-compartment model best described whole-body diffusion properties. Compartmental signal contributions from this model can be used to examine prostate cancer bone involvement. Keywords: Whole-Body MRI, Diffusion-weighted Imaging, Restriction Spectrum Imaging, Diffusion Signal Model, Bone Metastases, Prostate Cancer Clinical trial registration no. NCT03440554 Supplemental material is available for this article. © RSNA, 2023 See also commentary by Margolis in this issue.

Validating the screening criteria for bone metastases in treatment-naïve unfavorable intermediate and high-risk prostate cancer - the prevalence and location of bone- and lymph node metastases

OBJECTIVE

The European Association of Urology (EAU) recommends a bone scan for newly diagnosed unfavorable intermediate- and high-risk prostate cancer. We aimed to validate the screening criteria for bone metastases in patients with treatment-naïve prostate cancer.

METHODS

This single-center retrospective study included all patients with treatment-naïve unfavorable intermediate- or high-risk prostate cancer. All underwent MRI of the lumbar column (T2Dixon) and pelvis (3DT2w, DWI, and T2 Dixon). The presence and location of lymph node and bone metastases were registered according to risk groups and radiological (rad) T-stage. The risk of lymph node metastases was assessed by odds ratio (OR).

RESULTS

We included 390 patients, of which 68% were high-risk and 32% were unfavorable intermediate-risk. In the high-risk group, the rate of regional- and non-regional lymph node metastases was 11% and 6%, respectively, and the rate of bone metastases was 10%. In the unfavorable intermediate-risk group, the rate of regional- and non-regional lymph node metastases was 4% and 0.8%, respectively, and the rate of bone metastases was 0.8%. Metastases occurred exclusively in the lumbar column in 0.5% of all patients, in the pelvis in 4%, and the pelvis and lumbar column in 3%. All patients with bone metastases had radT3-4, and patients with radT3-4 showed a four-fold increased risk of lymph node metastases (OR 4.48, 95% CI: 2.1-9.5).

CONCLUSION

Bone metastases were found in 10% with high-risk prostate cancer and 0.8% with unfavorable intermediate-risk. Therefore, we question the recommendation to screen the unfavorable intermediate-risk group for bone metastases.

KEY POINTS

• The rate of bone metastases was 10% in high-risk patients and 0.8% in the unfavorable intermediate-risk group. • The rate of lymph-node metastases was 17% in high-risk patients and 5% in the unfavorable intermediate-risk group. • No bone metastases were seen in radiologically localized disease.

Whole-body MRI in oncology: can a single anatomic T2 Dixon sequence replace the combination of T1 and STIR sequences to detect skeletal metastasis and myeloma?

OBJECTIVES

To compare the diagnostic accuracy of a single T2 Dixon sequence to the combination T1+STIR as anatomical sequences used for detecting tumoral bone marrow lesions in whole-body MRI (WB-MRI) examinations.

METHODS

Between January 2019 and January 2020, seventy-two consecutive patients (55 men, 17 women, median age = 66 years) with solid (prostate, breast, neuroendocrine) cancers at high risk of metastasis or proven multiple myeloma (MM) prospectively underwent a WB-MRI examination including coronal T1, STIR, T2 Dixon and axial diffusion-weighted imaging sequences. Two radiologists independently assessed the combination of T1+STIR sequences and the fat+water reconstructions from the T2 Dixon sequence. The reference standard was established by consensus reading of WB-MRI and concurrent imaging available at baseline and at 6 months. Repeatability and reproducibility of MRI scores (presence and semi-quantitative count of lesions), image quality (SNR: signal-to-noise, CNR: contrast-to-noise, CRR: contrast-to-reference ratios), and diagnostic characteristics (Se: sensitivity, Sp: specificity, Acc: accuracy) were assessed per-skeletal region and per-patient.

RESULTS

Repeatability and reproducibility were at least good regardless of the score, region, and protocol (0.67 ≤ AC1 ≤ 0.98). CRR was higher on T2 Dixon fat compared to T1 (p < 0.0001) and on T2 Dixon water compared to STIR (p = 0.0128). In the per-patient analysis, Acc of the T2 Dixon fat+water was higher than that of T1+STIR for the senior reader (Acc = +0.027 [+0.025; +0.029], p < 0.0001) and lower for the junior reader (Acc = -0.029 [-0.031; -0.027], p < 0.0001).

CONCLUSIONS

A single T2 Dixon sequence with fat+water reconstructions offers similar reproducibility and diagnostic accuracy as the recommended combination of T1+STIR sequences and can be used for skeletal screening in oncology, allowing significant time-saving.

KEY POINTS

• Replacement of the standard anatomic T1 + STIR WB-MRI protocol by a single T2 Dixon sequence drastically shortens the examination time without loss of diagnostic accuracy. • A protocol based on fat + water reconstructions from a single T2 Dixon sequence offers similar inter-reader agreement and a higher contrast-to-reference ratio for detecting lesions compared to the standard T1 + STIR protocol. • Differences in the accuracy between the two protocols are marginal (+ 3% in favor of the T2 Dixon with the senior reader; -3% against the T2 Dixon with the junior reader).

Emerging MR methods for improved diagnosis of prostate cancer by multiparametric MRI

Current challenges of using serum prostate-specific antigen (PSA) level-based screening, such as the increased false positive rate, inability to detect clinically significant prostate cancer (PCa) with random biopsy, multifocality in PCa, and the molecular heterogeneity of PCa, can be addressed by integrating advanced multiparametric MR imaging (mpMRI) approaches into the diagnostic workup of PCa. The standard method for diagnosing PCa is a transrectal ultrasonography (TRUS)-guided systematic prostate biopsy, but it suffers from sampling errors and frequently fails to detect clinically significant PCa. mpMRI not only increases the detection of clinically significant PCa, but it also helps to reduce unnecessary biopsies because of its high negative predictive value. Furthermore, non-Cartesian image acquisition and compressed sensing have resulted in faster MR acquisition with improved signal-to-noise ratio, which can be used in quantitative MRI methods such as dynamic contrast-enhanced (DCE)-MRI. With the growing emphasis on the role of pre-biopsy mpMRI in the evaluation of PCa, there is an increased demand for innovative MRI methods that can improve PCa grading, detect clinically significant PCa, and biopsy guidance. To meet these demands, in addition to routine T1-weighted, T2-weighted, DCE-MRI, diffusion MRI, and MR spectroscopy, several new MR methods such as restriction spectrum imaging, vascular, extracellular, and restricted diffusion for cytometry in tumors (VERDICT) method, hybrid multi-dimensional MRI, luminal water imaging, and MR fingerprinting have been developed for a better characterization of the disease. Further, with the increasing interest in combining MR data with clinical and genomic data, there is a growing interest in utilizing radiomics and radiogenomics approaches. These big data can also be utilized in the development of computer-aided diagnostic tools, including automatic segmentation and the detection of clinically significant PCa using machine learning methods.

Whole-body MRI: detecting bone metastases from prostate cancer

Whole-body magnetic resonance imaging (WB-MRI) is currently used worldwide for detecting bone metastases from prostate cancer. The 5-year survival rate for prostate cancer is > 95%. However, an increase in survival time may increase the incidence of bone metastasis. Therefore, detecting bone metastases is of great clinical interest. Bone metastases are commonly located in the spine, pelvis, shoulder, and distal femur. Bone metastases from prostate cancer are well-known representatives of osteoblastic metastases. However, other types of bone metastases, such as mixed or inter-trabecular type, have also been detected using MRI. MRI does not involve radiation exposure and has good sensitivity and specificity for detecting bone metastases. WB-MRI has undergone gradual developments since the last century, and in 2004, Takahara et al., developed diffusion-weighted Imaging (DWI) with background body signal suppression (DWIBS). Since then, WB-MRI, including DWI, has continued to play an important role in detecting bone metastases and monitoring therapeutic effects. An imaging protocol that allows complete examination within approximately 30 min has been established. This review focuses on WB-MRI standardization and the automatic calculation of tumor total diffusion volume (tDV) and mean apparent diffusion coefficient (ADC) value. In the future, artificial intelligence (AI) will enable shorter imaging times and easier automatic segmentation.

Correcting B0 inhomogeneity-induced distortions in whole-body diffusion MRI of bone

Diffusion-weighted magnetic resonance imaging (DWI) of the musculoskeletal system has various applications, including visualization of bone tumors. However, DWI acquired with echo-planar imaging is susceptible to distortions due to static magnetic field inhomogeneities. This study aimed to estimate spatial displacements of bone and to examine whether distortion corrected DWI images more accurately reflect underlying anatomy. Whole-body MRI data from 127 prostate cancer patients were analyzed. The reverse polarity gradient (RPG) technique was applied to DWI data to estimate voxel-level distortions and to produce a distortion corrected DWI dataset. First, an anatomic landmark analysis was conducted, in which corresponding vertebral landmarks on DWI and anatomic T₂-weighted images were annotated. Changes in distance between DWI- and T₂-defined landmarks (i.e., changes in error) after distortion correction were calculated. In secondary analyses, distortion estimates from RPG were used to assess spatial displacements of bone metastases. Lastly, changes in mutual information between DWI and T₂-weighted images of bone metastases after distortion correction were calculated. Distortion correction reduced anatomic error of vertebral DWI up to 29 mm. Error reductions were consistent across subjects (Wilcoxon signed-rank p < 10^-20). On average (± SD), participants' largest error reduction was 11.8 mm (± 3.6). Mean (95% CI) displacement of bone lesions was 6.0 mm (95% CI 5.0-7.2); maximum displacement was 17.1 mm. Corrected diffusion images were more similar to structural MRI, as evidenced by consistent increases in mutual information (Wilcoxon signed-rank p < 10^-12). These findings support the use of distortion correction techniques to improve localization of bone on DWI.

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.

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.

Role of whole-body diffusion-weighted imaging in evaluation of multiple myeloma

The evaluation of bone disease in multiple myeloma (MM) is an important topic in imaging. This study retrospectively investigated whole-body diffusion-weighted imaging (WB-DWI) in the evaluation of bone marrow infiltration and treatment response in MM.A total of 126 patients with MM who underwent WB-DWI between January 2016 and December 2020 were enrolled. All the patients received 4-course induction chemotherapy. WB-DWI was performed before and after chemotherapy to measure the apparent diffusion coefficient (ADC) values. According to gender and Revised International Staging System (RISS) staging groups, the relationship between ADC value and bone marrow plasma cell infiltration ratio before treatment were explored using Spearman and Pearson correlation coefficients. Comparison of ADC values before and after treatment according to different chemotherapy regimens and treatment response was performed by 2-independent samples non-parametric tests and t test.There was a negative correlation between the ADC value and the degree of bone marrow infiltration and this was statistically significant (r = -0.843, P < .001). In different gender and RISS groups, ADC value before treatment was negatively correlated with the proportion of plasma cell infiltration (male, r = -0.849; female, r = -0.836; Stage I, r = -0.659; Stage II, r = -0.870; Stage III, r = -0.745; all P < .001). The ADC values of all subjects increased to varying degrees after 4-course induction chemotherapy, including different chemotherapy regimens and treatment responses (all P < .05 except for progressive disease group).The ADC value was negatively correlated with the degree of bone marrow infiltration in different gender and RISS stages. The ADC value increased after treatment, but it was not consistent with progressive disease group. The increase of ADC value may indicate the disease burden and outcome of MM induced chemotherapy.

Prostate cancer: Molecular imaging and MRI

The role of molecular imaging in initial evaluation of men with presumed or established diagnosis of prostate cancer and work up of biochemical recurrence and metastatic disease is rapidly evolving due to superior diagnostic performance compared to anatomic imaging. However, variable tumor biology and expression of transmembrane proteins or metabolic alterations poses a challenge. We review the evidence and controversies with emphasis on emerging PET radiopharmaceuticals and experience on clinical utility of PET/CT and PET/MRI in diagnosis and management of prostate cancer.

Determination and clinical significance of bone pseudoprogression in hormone receptor-positive metastatic breast cancer

Background

^99mTechnetium labeled methylene diphosphonate bone scans (BSs) are commonly used to monitor disease progression in bone for patients with metastatic breast cancer (MBC). However, new BS lesions may represent osteoblastic bone healing, which we now define as bone pseudoprogression. In this study, we aimed to assess the clinical significance and determination methods of bone pseudoprogression.

Methods

This retrospective analysis was conducted among 48 patients with hormone receptor-positive MBC treated with first-line endocrine therapy. Four months after initiating therapy, all the participants did not show extraosseous disease progression. Participants were divided into two groups according to the presence of new BS lesions. All the patients continued on treatment until explicit disease progression (extraosseous disease progression or progressive lysis on bone lesions). Explicit progression-free survival (PFS) and extraosseous objective response rate were analyzed between the two groups.

Results

New BS lesions were observed in 11 of 48 (22.9%) patients. All the new BS lesions appeared as osteoblastic bone lesions on computed tomography. For patients with new BS lesions, the median PFS was 26.57 months [95% confidence interval (CI) 15.46-37.68], which was similar to that (29.57 months; 95% CI 19.24-39.90) in patients without new BS lesions [hazard ratio: 1.098 (95% CI 0.482-2.503), p = 0.818]. Notably, 82.9% of patients without new BS lesions showed an extraosseous objective response, whereas 85.7% of patients with new BS lesions demonstrated an extraosseous objective response [odds ratio: 0.806 (95% CI 0.061-5.682), p = 0.999]. The median interval between bone pseudoprogression and true disease progression was 21.26 months (95% CI 10.11-32.42).

Conclusions

Osteoblastic new BS lesions detected on follow-up BSs may represent bone pseudoprogression. Clinicians should raise awareness of bone pseudoprogression, thereby avoiding premature discontinuation of therapy and maximizing the opportunity to benefit from endocrine therapy. Due to the small sample size and retrospective nature of the study, large prospective clinical trials are needed to confirm our findings.

The Clinical Diagnostic Value of Lumbar Intervertebral Disc Herniation Based on MRI Images

MRI was used to measure the changes in the angle of the facet joints of the lumbar spine and analyze the relationship between it and the herniated lumbar intervertebral disc. Analysis of the causes of lumbar disc herniation from the anatomy and morphology of the spine provides a basis for the early diagnosis and prevention of lumbar disc herniation. There is a certain correlation between the changes shown in MRI imaging of lumbar disc herniation and the TCM syndromes of lumbar intervertebral disc herniation. There is a correlation between the syndromes of lumbar disc herniation and the direct signs of MRI: pathological type, herniated position, and degree of herniation. Indirect signs with MR, nerve root compression and dural sac compression, are related. The MRI examination results can help syndrome differentiation to improve its accuracy to a certain extent. MRI has high sensitivity for the measurement of the angle of the facet joints of the lumbar spine and can be used to study the correlation between the changes of the facet joint angles and the herniated disc. Facet joint asymmetry is closely related to lateral lumbar disc herniation, which may be one of its pathogenesis factors. The herniated intervertebral disc is mostly on the sagittal side of the facet joint, and the facet joint angle on the side of the herniated disc is more sagittal. The asymmetry of the facet joints is not related to the central lumbar disc herniation, and the angle of the facet joints on both sides of the central lumbar disc herniation is partial sagittal.

Flare phenomenon in prostate cancer: recent evidence on new drugs and next generation imaging

Over the years, an increasing proportion of metastatic prostate cancer patients has been found to experience an initial bone flare phenomenon under both standard therapies (androgen deprivation therapy, chemotherapy, radiotherapy, abiraterone, enzalutamide) and novel agents (immunotherapy, bone-targeting radioisotopes). The underlying biological mechanisms of the flare phenomenon are still elusive and need further clarification, particularly in relation to different types of treatment and their treatment response assessment. Flare phenomenon is often underestimated and, in some cases, can negatively affect clinical outcome. In cases with suspected bone flare, the treatment should be continued for a minimum of 12 more weeks before further decisions about efficacy can be taken. Physicians and patients should be aware of this effect to avoid unwarranted anxiety and inadequate early discontinuation of treatment. This review aims at highlighting new evidence on flare phenomenon arising after the introduction of new drugs extending across the biochemical, radiographic and clinical spectrum of the disease.

Whole-body MRI-based multivariate prediction model in the assessment of bone metastasis in prostate cancer

PURPOSE

A whole-body MRI (WB-MRI) including T1, short time inversion recovery (STIR), diffusion-weighted imaging (high b value) was applied in our center for the detection of bone metastasis in prostate cancer (PCa) patients. We intended to assess the diagnostic performance of this examination.

METHODS

547 cases of PCa patients with higher risk of metastasis were referred to bone scintigraphy with SPECT/CT (BS + SPECT/CT) and whole-body MRI in Shanghai Changhai Hospital. Best valuable comparator (BVC) was applied for the final diagnosis of metastasis. A panel of radiologists interpreted the results. Decision curve analysis (DCA) and receiver operating characteristic curve (ROC) analysis were applied.

RESULTS

Bone metastasis was diagnosed in 110 cases, and others were non-metastatic by BVC. The area under the receiver operating characteristic curve (AUC) was higher in WB-MRI (0.778) than BS + SPECT/CT (0.634, p < 0.001). A WB-MRI-based prediction model was established with AUC of 0.877. Internal validation showed that the predictive model was well-calibrated. The DCA demonstrated that the model had higher net benefit than the BS + SPECT/CT-based model.

CONCLUSION

WB-MRI is more effective in identifying metastasis in PCa patients than BS + SPECT/CT. The prediction model combined WB-MRI with clinical parameters may be a promising approach to the assessment of metastasis.

Repeatability and reproducibility of ADC measurements: a prospective multicenter whole-body-MRI study

OBJECTIVES

Multicenter oncology trials increasingly include MRI examinations with apparent diffusion coefficient (ADC) quantification for lesion characterization and follow-up. However, the repeatability and reproducibility (R&R) limits above which a true change in ADC can be considered relevant are poorly defined. This study assessed these limits in a standardized whole-body (WB)-MRI protocol.

METHODS

A prospective, multicenter study was performed at three centers equipped with the same 3.0-T scanners to test a WB-MRI protocol including diffusion-weighted imaging (DWI). Eight healthy volunteers per center were enrolled to undergo test and retest examinations in the same center and a third examination in another center. ADC variability was assessed in multiple organs by two readers using two-way mixed ANOVA, Bland-Altman plots, coefficient of variation (CoV), and the upper limit of the 95% CI on repeatability (RC) and reproducibility (RDC) coefficients.

RESULTS

CoV of ADC was not influenced by other factors (center, reader) than the organ. Based on the upper limit of the 95% CI on RC and RDC (from both readers), a change in ADC in an individual patient must be superior to 12% (cerebrum white matter), 16% (paraspinal muscle), 22% (renal cortex), 26% (central and peripheral zones of the prostate), 29% (renal medulla), 35% (liver), 45% (spleen), 50% (posterior iliac crest), 66% (L5 vertebra), 68% (femur), and 94% (acetabulum) to be significant.

CONCLUSIONS

This study proposes R&R limits above which ADC changes can be considered as a reliable quantitative endpoint to assess disease or treatment-related changes in the tissue microstructure in the setting of multicenter WB-MRI trials.

KEY POINTS

• The present study showed the range of R&R of ADC in WB-MRI that may be achieved in a multicenter framework when a standardized protocol is deployed. • R&R was not influenced by the site of acquisition of DW images. • Clinically significant changes in ADC measured in a multicenter WB-MRI protocol performed with the same type of MRI scanner must be superior to 12% (cerebrum white matter), 16% (paraspinal muscle), 22% (renal cortex), 26% (central zone and peripheral zone of prostate), 29% (renal medulla), 35% (liver), 45% (spleen), 50% (posterior iliac crest), 66% (L5 vertebra), 68% (femur), and 94% (acetabulum) to be detected with a 95% confidence level.

Comparison of PET/CT and MRI in the Diagnosis of Bone Metastasis in Prostate Cancer Patients: A Network Analysis of Diagnostic Studies

BACKGROUND

Accurate diagnosis of bone metastasis status of prostate cancer (PCa) is becoming increasingly more important in guiding local and systemic treatment. Positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging (MRI) have increasingly been utilized globally to assess the bone metastases in PCa. Our meta-analysis was a high-volume series in which the utility of PET/CT with different radioligands was compared to MRI with different parameters in this setting.

MATERIALS AND METHODS

Three databases, including Medline, Embase, and Cochrane Library, were searched to retrieve original trials from their inception to August 31, 2019 according to the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement. The methodological quality of the included studies was assessed by two independent investigators utilizing Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2). A Bayesian network meta-analysis was performed using an arm-based model. Absolute sensitivity and specificity, relative sensitivity and specificity, diagnostic odds ratio (DOR), and superiority index, and their associated 95% confidence intervals (CI) were used to assess the diagnostic value.

RESULTS

Forty-five studies with 2,843 patients and 4,263 lesions were identified. Network meta-analysis reveals that 68Ga-labeled prostate membrane antigen (68Ga-PSMA) PET/CT has the highest superiority index (7.30) with the sensitivity of 0.91 and specificity of 0.99, followed by 18F-NaF, 11C-choline, 18F-choline, 18F-fludeoxyglucose (FDG), and 18F-fluciclovine PET/CT. The use of high magnetic field strength, multisequence, diffusion-weighted imaging (DWI), and more imaging planes will increase the diagnostic value of MRI for the detection of bone metastasis in prostate cancer patients. Where available, 3.0-T high-quality MRI approaches 68Ga-PSMA PET/CT was performed in the detection of bone metastasis on patient-based level (sensitivity, 0.94 vs. 0.91; specificity, 0.94 vs. 0.96; superiority index, 4.43 vs. 4.56).

CONCLUSIONS

68Ga-PSMA PET/CT is recommended for the diagnosis of bone metastasis in prostate cancer patients. Where available, 3.0-T high-quality MRI approaches 68Ga-PSMA PET/CT should be performed in the detection of bone metastasis.

Whole-body magnetic resonance imaging for prostate cancer assessment: Current status and future directions

Over the past decade, updated definitions for the different stages of prostate cancer and risk for distant disease, along with the advent of new therapies, have remarkably changed the management of patients. The two expectations from imaging are accurate staging and appropriate assessment of disease response to therapies. Modern, next-generation imaging (NGI) modalities, including whole-body magnetic resonance imaging (WB-MRI) and nuclear medicine (most often prostate-specific membrane antigen [PSMA] positron emission tomography [PET]/computed tomography [CT]) bring added value to these imaging tasks. WB-MRI has proven its superiority over bone scintigraphy (BS) and CT for the detection of distant metastasis, also providing reliable evaluations of disease response to treatment. Comparison of the effectiveness of WB-MRI and molecular nuclear imaging techniques with regard to indications and the definition of their respective/complementary roles in clinical practice is ongoing. This paper illustrates the evolution of WB-MRI imaging protocols, defines the current state-of-the art, and highlights the latest developments and future challenges. The paper presents and discusses WB-MRI indications in the care pathway of men with prostate cancer in specific key situations: response assessment of metastatic disease, "all in one" cancer staging, and oligometastatic disease.

The prevalence and locations of bone metastases using whole-body MRI in treatment-naïve intermediate- and high-risk prostate cancer

Objective

The aim of this study was to assess the prevalence and distribution of bone metastases in treatment-naïve prostate cancer patients eligible for a metastatic workup using whole-body MRI, and to evaluate the results in light of current guidelines.

Methods

This single-institution, retrospective study included all patients with treatment-naïve prostate cancer referred to whole-body MRI during 2016 and 2017. All were eligible for a metastatic workup according to the guidelines: PSA > 20 ng/ml and/or Gleason grade group ≥ 3 and/or cT ≥ 2c and/or bone symptoms. The definition of a metastasis was descriptive and based on the original MRI reports. The anatomical location of metastases was registered.

Results

We included 161 patients with newly diagnosed prostate cancer of which 36 (22%) were intermediate-risk and 125 (78%) were high-risk. The median age and PSA were 71 years (IQR 64–76) and 13 ng/ml (IQR 8–28), respectively. Bone metastases were found in 12 patients (7%, 95% CI: 4–13), and all were high-risk with Gleason grade group ≥ 4. The pelvis was affected in 4 patients, and the spine + pelvis in the remaining 8. No patients demonstrated metastases to the spine without concomitant metastases in the pelvis. Limitations are the small number of metastases and retrospective design.

Conclusion

This study suggests that the overall prevalence of bone metastases using the current guidelines for screening is quite low. No metastases were seen in the case of Gleason grade group ≤ 3, and further studies should investigate if it necessary to screen non-high-risk patients.

Key Points

• The overall prevalence of bone metastases was 7% in the case of newly diagnosed intermediate- and high-risk prostate cancer.

• The prevalence in high-risk patients was 10%, and no metastases were seen in patients with Gleason grade group ≤ 3.

• The pelvic skeleton is the main site, and no metastases occurred in the spine without concomitant pelvic metastases.

Comparison of Whole-Body MRI, CT, and Bone Scintigraphy for Response Evaluation of Cancer Therapeutics in Metastatic Breast Cancer to Bone

Background CT and bone scintigraphy have limitations in evaluating systemic anticancer therapy (SACT) response in bone metastases from metastatic breast cancer (MBC). Purpose To evaluate whether whole-body MRI enables identification of progressive disease (PD) earlier than CT and bone scintigraphy in bone-only MBC. Materials and Methods This prospective study evaluated participants with bone-only MBC between May 2016 and January 2019 (ClinicalTrials.gov identifier: NCT03266744). Participants were enrolled at initiation of first or subsequent SACT based on standard CT and bone scintigraphy imaging. Baseline whole-body MRI was performed within 2 weeks of entry; those with extraosseous disease were excluded. CT and whole-body MRI were performed every 12 weeks until definitive PD was evident with one or both modalities. In case of PD, bone scintigraphy was used to assess for bone disease progression. Radiologists independently interpreted images from CT, whole-body MRI, or bone scintigraphy and were blinded to results with the other modalities. Systematic differences in performance between modalities were analyzed by using the McNemar test. Results Forty-five participants (mean age, 60 years ± 13 [standard deviation]; all women) were evaluated. Median time on study was 36 weeks (range, 1-120 weeks). Two participants were excluded because of unequivocal evidence of liver metastases at baseline whole-body MRI, two participants were excluded because they had clinical progression before imaging showed PD, and one participant was lost to follow-up. Of the 33 participants with PD at imaging, 67% (22 participants) had PD evident at whole-body MRI only and 33% (11 participants) had PD at CT and whole-body MRI concurrently; none had PD at CT only (P < .001, McNemar test). There was only slight agreement between whole-body MRI and CT (Cohen κ, 0.15). PD at bone scintigraphy was reported in 50% of participants (13 of 26) with bone progression at CT and/or whole-body MRI (P < .001, McNemar test). Conclusion Whole-body MRI enabled identification of progressive disease before CT in most participants with bone-only metastatic breast cancer. Progressive disease at bone scintigraphy was evident in only half of participants with bone progression at whole-body MRI. © RSNA, 2020 Online supplemental material is available for this article.

Baseline bone marrow ADC value of diffusion-weighted MRI: a potential independent predictor for progression and death in patients with newly diagnosed multiple myeloma

OBJECTIVES

To illuminate the prognostic value of ADC (apparent diffusion coefficient), an important quantitative parameter of diffusion-weighted MRI, for multiple myeloma (MM).

METHODS

A prospective single-center study which enrolled 114 consecutive newly diagnosed MM patients with baseline whole-body diffusion-weighted MRI (WB DW-MRI) results was conducted. Baseline clinical and MRI parameters were analyzed with univariate and multivariate approaches to identify independent risk factors for progression-free survival (PFS) and overall survival (OS).

RESULTS

Five different DW-MRI patterns were seen, and the mean ADC value of the representative background bone marrow was 0.4662 ± 0.1939 × 10^-3 mm²/s. After a mean follow-up of 50.2 months (range, 15.7-75.8 months), twenty-four patients died and seven were lost to follow-up. The mean ADC value of the representative background bone marrow was showed to be an independent risk factor for both PFS (HR 4.664; 95% confidence interval (CI) 1.138-19.121; p = 0.032) and OS (HR 14.130; 95% CI 1.544-129.299; p = 0.019). Normal/salt-and-pepper pattern on DW-MRI was associated with PFS using univariate analysis (p = 0.035) but lost the significance with multivariate Cox regression.

CONCLUSIONS

Mean ADC value of the representative background bone marrow predicts both PFS and OS which suggests the role of baseline DW-MRI for risk stratification in newly diagnosed MM patients.

KEY POINTS

• Whole-body diffusion-weighted MRI (WB DW-MRI) might be helpful to improve the current risk stratification systems for newly diagnosed multiple myeloma (MM). • Morphological parameters as MRI pattern and focal lesion-associated parameters have been reported to be related to survival. However, important functional parameters such as apparent diffusion coefficient (ADC) values were not incorporated into the current risk stratification model. • This study is one of the first endeavors to delineate the correlation of baseline ADC values and survival in MM patients. It is revealed that the mean ADC value of the representative background bone marrow (L3-S1 and iliac bone) was an independent risk factor for both PFS and OS.

Whole-body diffusion-weighted magnetic resonance imaging for the detection of bone metastases and their prognostic impact in metastatic renal cell carcinoma patients treated with angiogenesis inhibitors

Background: Metastatic renal cell carcinoma (mRCC) patients with bone metastases (BM) are at high risk for skeletal related events and have a poorer outcome when treated with vascular endothelial growth factor receptor-tyrosine kinase inhibitors (VEGFR-TKIs). Computed tomography (CT) lacks sensitivity to detect BM in mRCC. We aimed to determine the added value of whole body diffusion-weighted magnetic resonance imaging (WB-DWI/MRI) to CT for the detection of BM in mRCC and to estimate the prognostic impact of the number of BM in mRCC patients treated with VEGFR-TKIs.Material and methods: We conducted a prospective study including consecutive mRCC patients treated with a first-line VEGFR-TKI in the metastatic setting. All patients underwent a pretreatment thoracic-abdominal-pelvic CT and WB-DWI/MRI. CT and WB-DWI/MRI were compared for the detection of BM. The number of detected BM was correlated with response rate (RR), progression-free survival (PFS) and overall survival (OS) after start of the VEGFR-TKI.Results: Ninety-two patients were included. BM were found in 55% of the patients by WB-DWI/MRI and in 43% of the patients by CT (p = .003). Mean number of BM discovered per patient was 6.8 by WB-DWI/MRI versus 1.9 by CT (p = .006). The cutoff of ≤5 versus >5 BM on WB-DWI/MRI had the highest discriminative power for all outcome measures. Patients with >5 BM had a lower RR (10% versus 42%), more frequently early progressive disease (43% versus 13%, p = .003), shorter PFS (4 versus 10 months, p = .006) and shorter OS (10 versus 35 months, p < .0001) compared to patients with ≤5 BM.Conclusion: WB-DWI/MRI detects significantly more BM in mRCC patients than CT, allowing better estimation of the prognostic impact of BM in mRCC patients treated with VEGFR-TKIs. The prognostic impact should now be validated in patients treated with immune checkpoint inhibitors.

Comparison of whole-body MRI with diffusion-weighted imaging and PET/CT in lymphoma staging

OBJECTIVES

To compare the diagnostic efficiency of whole-body MRI-DWI and PET/CT in lymphoma staging.

METHODS

A prospective study enrolled 92 patients with lymphoma. Prior to treatment, all patients underwent whole-body MRI-DWI and PET-CT. The methods' efficiency was compared in the diagnosis of lymph node (LN) and organ involvement, and in determining lymphoma stage.

RESULTS

Sensitivity, specificity, and accuracy in the diagnosis of enlarged LN involvement were 98.2%, 99.9%, and 99.3%, respectively, for MRI-DWI, and 99.4%, 100.0%, and 99.8%, respectively, for PET/CT. ROC analysis showed similar methods' efficiency in the diagnosis of enlarged LN involvement (p > 0.06). MRI-DWI and PET/CT sensitivity in the diagnosis of non-enlarged LN involvement was 77.8% and 88.1%, respectively (p < 0.001). MRI-DWI and PET/CT sensitivity, specificity, and accuracy in the diagnosis of lung involvement were 73.3%, 98.7%, 94.6% and 86.7%, 98.7%, 96.7%; spleen involvement 54.8%, 98.3%, 83.3% and 100.0%, 100.0%, 100.0%; bone marrow involvement 87.1%, 96.4%, 93.0% and 64.5%, 87.3%, 79.1%; and all-organ involvement 72.9%, 98.1%, 91.4% and 80.0%, 96.6%, 92.2%, respectively. ROC analysis showed similar methods' efficiency in the diagnosis of lung involvement (р > 0.3), higher for PET/CT in spleen involvement (р < 0.0001), higher for MRI-DWI in bone marrow involvement (р < 0.0008), and similar in all-organ involvement (р > 0.35). MRI-DWI and PET/CT determined the correct lymphoma stage in 79 (86%) patients.

CONCLUSIONS

Whole-body MRI-DWI and PET/CT determined the correct lymphoma stage in similar numbers of patients. MRI-DWI can serve as a non-irradiative alternative to PET/CT in lymphoma staging.

KEY POINTS

• Whole-body MRI-DWI efficiency compared with that of PET/CT is similar in the diagnosis of enlarged LN involvement, inferior in the diagnosis of non-enlarged LN and spleen involvement, but superior in the diagnosis of bone marrow involvement. • A new efficient MRI-DWI sign for diagnosis of diffuse bone marrow involvement has been proposed, i.e., a diffuse increase in spine signal intensity on high b value DWI images above the kidney parenchyma. • MRI-DWI and PET/CT determined the correct lymphoma stage in similar numbers of patients.

Shortening the acquisition time of whole-body MRI: 3D T1 gradient echo Dixon vs fast spin echo for metastatic screening in prostate cancer

PURPOSE

To compare 3D T1-weighted fast spin echo (FSE) and 3D T1-weighted gradient echo (GE) mDixon as morphologic sequences to complement diffusion-weighted imaging (DWI) for the metastatic screening in prostate cancer (PCa) patients.

MATERIALS AND METHODS

Thirty PCa patients at high risk of metastases prospectively underwent both a 3D T1 FSE (14 min) and a rapid 3D T1 GE^mDixon (1 min 20 s) sequences within a WB-MRI protocol. Two readers assessed the diagnostic performance of the FSE/Fat/in-phase (IP)/IP+Fat sequences in detecting bone and node metastases. The reference standard was established by a panel of four physicians on the basis of all baseline and follow-up imaging, biological and clinical information. The reproducibility of readings, predictive accuracy (Acc) from ROC curves analysis, and contrast-to-reference ratio (CRR) in lesions were assessed for each sequence.

RESULTS

In bone and lymph nodes (per-region analysis), reproducibility was at least good for all sequences/readers, except for nodes in the common iliac/inguinal regions. In bone (per-organ analysis), Acc of FSE was superior to that of mDixon (difference + 4%, p < 0.0083). In nodes (per-organ analysis), Acc of Fat was superior to that of other sequences (difference + 4% to + 6% depending on reader, p < 0.0083). In the per-patient analysis, Acc of FSE was superior to that of mDixon (difference + 4% to + 6% depending on sequence, p < 0.0083). Fat images had higher CRR compared with FSE in the thoracic spine, the bony pelvis and lymph node metastases (p < 0.025).

CONCLUSION

3D T1 GE^mDixon may replace 3D T1 FSE to complement DWI in WB-MRI for metastatic screening in PCa. It demonstrates an Acc ranging from + 4% to + 6% (nodes) to - 4% to - 6% (bone and patient staging) compared with FSE and considerably reduces the examination time, offering the perspective of acquiring WB-MRI examinations in less than 20 min.

KEY POINTS

• The replacement of 3D T1 FSE by the 3D T1 GE mDixon as morphologic sequence to complement DWI drastically reduces the acquisition time of WB-MRI studies. • The 3D T1 GE mDixon sequence offers similar reproducibility of image readings compared with that of the 3D T1 FSE. • Differences in diagnostic accuracy are limited (+ 4%/+ 6% in favor of mDixon to detect node metastases; + 4%/+ 6% in favor of FSE to detect bone metastases/metastatic disease in a patient).

Imaging for Metastasis in Prostate Cancer: A Review of the Literature

Background: Initial staging and assessment of treatment activity in metastatic prostate cancer (PCa) patients is controversial. Indications for the various available imaging modalities are not well-established due to rapid advancements in imaging and treatment.

Methods: We conducted a critical literature review of the main imaging abnormalities that suggest a diagnosis of metastasis in localized and locally advanced PCa or in cases of biological relapse. We also assessed the role of the various imaging modalities available in routine clinical practice for the detection of metastases and response to treatment in metastatic PCa patients.

Results: In published clinical trials, the most commonly used imaging modalities for the detection and evaluation of therapeutic response are bone scan, abdominopelvic computed tomography (CT), and pelvic and bone magnetic resonance imaging (MRI). For the detection and follow-up of metastases during treatment, modern imaging techniques i.e., choline-positron emission tomography (PET), fluciclovine-PET, or Prostate-specific membrane antigen (PSMA)-PET provide better sensitivity and specificity. This is particularly the case of fluciclovine-PET and PSMA-PET in cases of biochemical recurrence with low values of prostate specific antigen.

Conclusions: In routine clinical practice, conventional imaging still have a role, and communication between imagers and clinicians should be encouraged. Present and future clinical trials should use modern imaging methods to clarify their usage.

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.

Multiparametric MRI - local staging of prostate cancer and beyond

Background Accurate local staging is critical for treatment planning and prognosis in patients with prostate cancer (PCa). The primary aim is to differentiate between organ-confined and locally advanced disease with the latter carrying a worse clinical prognosis. Multiparametric MRI (mpMRI) is the imaging modality of choice for the local staging of PCa and has an incremental value in assessing pelvic nodal disease and bone involvement. It has shown superior performance compared to traditional staging based on clinical nomograms, and provides additional information on the site and extent of disease. MRI has a high specificity for diagnosing extracapsular extension (ECE), seminal vesicle invasion (SVI) and lymph node (LN) metastases, however, sensitivity remains poor. As a result, extended pelvic LN dissection remains the gold standard for assessing pelvic nodal involvement, and there has been recent progress in developing advanced imaging techniques for more distal staging. Conclusions T2W-weighted imaging is the cornerstone for local staging of PCa. Imaging at 3T and incorporating both diffusion weighted and dynamic contrast enhanced imaging can further increase accuracy. "Next generation" imaging including whole body MRI and PET-MRI imaging using prostate specific membrane antigen (68Ga-PSMA), has shown promising for assessment of LN and bone involvement as compared to the traditional work-up using bone scintigraphy and body CT.