Faculty Bibliography

OBJECTIVE. The purpose of this article is to provide a practice-focused review of accelerating musculoskeletal MRI with the use of widely accessible techniques and to assess the effects of such acceleration on the value of musculoskeletal MRI. CONCLUSION. Echo-train compaction with fast radiofrequency pulses, high gradient performance modes, and high receiver bandwidth, as well as basic phase undersampling techniques, affords at least twofold acceleration of musculoskeletal MRI examinations while retaining image quality, comprehensiveness, and diagnostic performance. Optimized efficiency is a cornerstone for adding value to musculoskeletal MRI.

OBJECTIVE. The purpose of this article is to provide a practice-focused review of the clinical application of advanced acceleration techniques for rapid musculoskeletal MRI examinations. CONCLUSION. Parallel imaging, simultaneous multislice acquisition, compressed sensing-based sampling, and synthetic MRI techniques provide unprecedented opportunities for rapid musculoskeletal MRI examinations. For 2D and 3D fast spin-echo and turbo spin-echo pulse sequences, acceleration factors between 3 and 8 can be realized in clinical practice, amounting to a time savings of 66-85% when compared with unaccelerated acquisitions.

Musculoskeletal (MSK) image-guided oncologic intervention is an established field within radiology. Numerous studies have described its clinical benefits, safety, cost effectiveness, patient satisfaction, and improved quality of life, thereby establishing image-guided oncologic intervention as a preferred pathway in treating patients presenting with specific benign MSK tumors. But there is a paradigm shift on the horizon because these techniques may also support established pillars (surgery, systemic treatment, radiotherapy) in the treatment of malignant MSK tumors. Unlike benign tumors, where they are used as primary therapy lines with curative intent, such interventions can be selected for malignant tumors as adjuvant treatment in painful or unstable bone or soft tissue lesions or as more palliative therapy strategies. Using examples from our clinical practices, we elaborate on the benefits of applying a multidisciplinary approach (traditionally involving MSK radiologists, oncologists, orthopaedic surgeons, microbiologists, pathologists, physiotherapists, and pain management experts), ideally within a sarcoma treatment center to deliver a patient-specific therapy plan and illustrate methods to assess the benefits of this model of care.In this article, we review the current repertoire of ablation techniques, demonstrate why such procedures offer value-based alternatives to conventional treatments of specific tumors, and reflect on future directions. Additionally, we review the advantages and limitations of each technique and offer guidance to improve outcomes.

OBJECTIVE:To develop and evaluate the performance of deep convolutional neural networks (DCNN) to detect and identify specific total shoulder arthroplasty (TSA) models. MATERIALS AND METHODS/METHODS:We included 482 radiography studies obtained from publicly available image repositories with native shoulders, reverse TSA (RTSA) implants, and five different TSA models. We trained separate ResNet DCNN-based binary classifiers to (1) detect the presence of shoulder arthroplasty implants, (2) differentiate between TSA and RTSA, and (3) differentiate between the five TSA models, using five individual classifiers for each model, respectively. Datasets were divided into training, validation, and test datasets. Training and validation datasets were 20-fold augmented. Test performances were assessed with area under the receiver-operating characteristic curves (AUC-ROC) analyses. Class activation mapping was used to identify distinguishing imaging features used for DCNN classification decisions. RESULTS:The DCNN for the detection of the presence of shoulder arthroplasty implants achieved an AUC-ROC of 1.0, whereas the AUC-ROC for differentiation between TSA and RTSA was 0.97. Class activation map analysis demonstrated the emphasis on the characteristic arthroplasty components in decision-making. DCNNs trained to distinguish between the five TSA models achieved AUC-ROCs ranging from 0.86 for Stryker Solar to 1.0 for Zimmer Bigliani-Flatow with class activation map analysis demonstrating an emphasis on unique implant design features. CONCLUSION/CONCLUSIONS:DCNNs can accurately identify the presence of and distinguish between TSA & RTSA, and classify five specific TSA models with high accuracy. The proof of concept of these DCNNs may set the foundation for an automated arthroplasty atlas for rapid and comprehensive model identification.

Purpose: To investigate the heating effect of clinical metal artifact reduction MRI protocols at 1.5 and 3T on different types of hip arthroplasty implants.
Material(s) and Method(s): Two standard ASTM MRI phantoms were placed head-to-head on the scanner table to simulate the upper and lower portions of a human torso. The phantoms were filled with gelled saline medium, which had the electrical and thermal properties of human muscle. Four different total hip arthroplasty implant configurations, including a metal-on-polyethylene construct with cobalt chromium (CoCr) femoral stem, a metal-on-metal construct with CoCr femoral stem, and two metalon-ceramic constructs with titanium (Ti) femoral stems at two lengths were tested. Fiber optic temperature sensors were used to measure the temperature at seven points along the implants. Temperature changes of three clinical pulse sequence type protocols, including high-bandwidth turbo spin echo (HBW-TSE), Slice Encoding for Metal Artifact Correction (SEMAC), and compressed sensing SEMAC (CS-SEMAC) were measured. Each protocol contained 6 pulse sequences, which were obtained in coronal, sagittal and axial orientations as intermediateweighted and short tau inversion recovery (STIR) varieties with image coverage identical to that in patients. Non-parametric Friedman and Wilcoxon signed-rank tests were implemented for multi-group comparisons.
Result(s): In 1.5T experiments, the maximum heating consistently occurred at the tip of the femoral stem for all implant types (p < 0.01). The maximum heating at any single point reached to 13.1degreeC at 1.5T which was at the tip of the shorter Ti stem. Across all 3T MRI protocols and all implant constructs, the maximum heating at any single point was 1.9 degreeC. Maximum temperature rises at 3T occurred at the tip of the femoral stem and medial aspect of the acetabular cup in most cases; however, there was no significant heating difference among various points along the implant periphery (p > 0.05). The degree of heating was not different between different implant types at 1.5 or 3T (p > 0.05).
Conclusion(s): Metal artifact reduction MRI at 1.5T may result in supraphysiological heating of the implant which can be mitigated with proper adjustment of scan protocol. However, 3T MRI poses no risk of thermal injury, and can be considered safe clinically

OBJECTIVES/OBJECTIVE:Longitudinal assessment of changes in apparent diffusion coefficient (ADC)-values in multiple myeloma (MM) patients and their potential role for classifying disease activity. METHODS:Retrospective analysis of whole-body-MRI data in 73 stage III MM patients undergoing systemic treatment. Bone marrow involvement was evaluated using a standardized unenhanced 4-sequences whole-body-MRI protocol. We measured ADC-values in focal lesions (FL) and diffusely involved bone marrow (DIBM) areas. Response to treatment was based on the course of hematologic parameters. The time points of MRI-examinations were baseline, 1st (mean, 3 months), 2nd (mean, 10 months), and 3rd (mean, 18 months) follow up (FU). RESULTS:/s for diagnosing inactive disease at follow-up proved unreliable. CONCLUSIONS:In myeloma-patients with lower tumor burden, the longitudinal course of ADC-values is predictable only for FL whereas for DIBM ADC-changes considerably overlap between responders and non-responders and are not indicative for assessment of the disease activity.

RATIONALE AND OBJECTIVES/OBJECTIVE:The educational value of the daily resident readout, a vital component of resident training, has been markedly diminished due to a significant decrease in imaging volume and case mix diversity. The goal of this study was to create a "simulated" daily readout (SDR) to restore the educational value of the daily readout. MATERIALS AND METHODS/METHODS:To create the SDR the following tasks were performed; selection of cases for a daily worklist for each resident rotation, comprising a combination of normal and abnormal cases; determination of the correct number of cases and the appropriate mix of imaging modalities for each worklist; development of an "educational" environment consisting of separate "instances" of both our Picture Archive Communication System and reporting systems; and the anonymization of all of the cases on the worklists. Surveys of both residents and faculty involved in the SDR were performed to assess its effectiveness. RESULTS:Thirty-two residents participated in the SDR. The daily worklists for the first 20 days of the SDR included 3682 cases. An average of 480 cases per day was dictated by the residents. Surveys of the residents and the faculty involved in the SDR demonstrated that both agreed that the SDR effectively mimics a resident's daily work on rotations and preserves resident education during the Coronavirus Disease 2019 crisis. CONCLUSION/CONCLUSIONS:The development of the SDR provided an effective method of preserving the educational value of the daily readout experience of radiology residents, despite severe decreases in imaging exam volume and case mix diversity during the Coronavirus Disease 2019 pandemic.

OBJECTIVES/OBJECTIVE:The aim of this study was to test the hypothesis that clinically used magnetic resonance (MR)-conditional needles of varying lengths, orientations, locations, and pulse sequences can result in excessive heating during MR imaging (MRI)-guided interventions that can be minimized to physiological ranges with proper selection of the needle length, needle position, and modification of pulse sequence parameters. MATERIALS AND METHODS/METHODS:We simulated a clinical interventional MRI setting with 2 standard American Society for Testing and Materials F2182-11A phantoms and measured temperatures with fiber optic sensors. Temperature profiles were monitored for commercial 10, 15 and 20 cm MR-conditional cobalt-chromium needles in clinically relevant perpendicular, 45-degree oblique, and parallel orientations relative to the static magnetic field (B0) and center, right off-center, and left off-center needle tip locations in the z = 0 plane. Clinically available interventional MRI pulse sequences including turbo spin echo (TSE), fast TSE, slice encoding for metal artifact correction, compressed sensing slice encoding for metal artifact correction, half-Fourier acquisition single-shot TSE (HASTE), HASTE inversion recovery, fluoroscopic steady-state gradient echo (3.0 T only), fast low-angle shot gradient echo, and volumetric interpolated breath-hold examination gradient echo pulse sequences were tested at 1.5 and 3.0 T field strengths. Acquired temperature data were analyzed using Friedman and Wilcoxon signed-rank tests with Bonferroni correction. RESULTS:After 5-minute of continuous MRI, less than 2.5°C heating occurred when needles were oriented perpendicular and 45-degree oblique to B0, regardless of field strengths. Higher temperature rises capable of causing permanent tissue damage were observed when needles were oriented in parallel to B0 (1.5 T: 22°C with 20 cm needles, 3.0 T: 8°C with 10 and 15 cm needles) using higher radiofrequency energy pulse sequences, such as TSE and HASTE. Left off-center location, parallel orientation, and needle lengths close to half of the radiofrequency pulse wavelength were positively associated with higher temperature rises. CONCLUSIONS:Under the herein used experimental conditions, clinically used MR-conditional needles can heat to supraphysiologic temperatures during prolonged MRI at 1.5 and 3.0 T field strengths; however, the temperature rise can be balanced to physiological ranges with proper selection of needle length, needle orientation, and pulse sequence parameters. Caution must be exercised when using different MRI systems, as results may not directly translate.