Does the presence of macroscopic intralesional fat exclude malignancy? An analysis of 613 histologically proven malignant bone lesions.

OBJECTIVE: To determine if macroscopic intralesional fat detected in bone lesions on CT by Hounsfield unit (HU) measurement and on MRI by macroscopic assessment excludes malignancy. MATERIALS AND METHODS: All consecutive CT-guided core needle biopsies (CNB) of non-spinal bone lesions performed at a tertiary center between December 2005 and September 2021 were reviewed. Demographic and histopathology data were recorded. All cases with malignant histopathology were selected, and imaging studies were reviewed. Two independent readers performed CT HU measurements on all bone lesions using a circular region of interest (ROI) to quantitate intralesional fat density (mean HU < -30). MRI images were reviewed to qualitatively assess for macroscopic intralesional fat signal in a subset of patients. Inter-reader agreement was assessed with Cronbach's alpha and intraclass correlation coefficient. RESULTS: In 613 patients (mean age 62.9 years (range 19-95 years), 47.6% female), CT scans from the CNB of 613 malignant bone lesions were reviewed, and 212 cases had additional MRI images. Only 3 cases (0.5%) demonstrated macroscopic intralesional fat on either CT or MRI. One case demonstrated macroscopic intralesional fat density on CT in a case of metastatic prostate cancer. Two cases demonstrated macroscopic intralesional fat signal on MRI in cases of chondrosarcoma and osteosarcoma. Inter-reader agreement was excellent (Cronbach's alpha, 0.95-0.98; intraclass correlation coefficient, 0.90-0.97). CONCLUSION: Malignant lesions rarely contain macroscopic intralesional fat on CT or MRI. While CT is effective in detecting macroscopic intralesional fat in primarily lytic lesions, MRI may be better for the assessment of heterogenous and infiltrative lesions with mixed lytic and sclerotic components. CLINICAL RELEVANCE STATEMENT: Macroscopic intralesional fat is rarely seen in malignant bone tumors and its presence can help to guide the diagnostic workup of bone lesions. KEY POINTS: • Presence of macroscopic intralesional fat in bone lesions has been widely theorized as a sign of benignity, but there is limited supporting evidence in the literature. • CT and MRI are effective in evaluating for macroscopic intralesional fat in malignant bone lesions with excellent inter-reader agreement. • Macroscopic intralesional fat is rarely seen in malignant bone lesions.

Clinical Applications, Challenges, and Recommendations for Artificial Intelligence in Musculoskeletal and Soft-Tissue Ultrasound: AJR Expert Panel Narrative Review.

Artificial intelligence (AI) is increasingly used in clinical practice for musculoskeletal imaging tasks, such as disease diagnosis and image reconstruction. AI applications in musculoskeletal imaging have focused primarily on radiography, CT, and MRI. Although musculoskeletal ultrasound stands to benefit from AI in similar ways, such applications have been relatively underdeveloped. In comparison with other modalities, ultrasound has unique advantages and disadvantages that must be considered in AI algorithm development and clinical translation. Challenges in developing AI for musculoskeletal ultrasound involve both clinical aspects of image acquisition and practical limitations in image processing and annotation. Solutions from other radiology subspecialties (e.g., crowdsourced annotations coordinated by professional societies), along with use cases (most commonly rotator cuff tendon tears and palpable soft-tissue masses), can be applied to musculoskeletal ultrasound to help develop AI. To facilitate creation of high-quality imaging datasets for AI model development, technologists and radiologists should focus on increasing uniformity in musculoskeletal ultrasound performance and increasing annotations of images for specific anatomic regions. This Expert Panel Narrative Review summarizes available evidence regarding AI's potential utility in musculoskeletal ultrasound and challenges facing its development. Recommendations for future AI advancement and clinical translation in musculoskeletal ultrasound are discussed.

The International Skeletal Society: a look back at 50 years of multidisciplinary expertise, collaboration, and education in musculoskeletal health and disease.

Multidisciplinary collaboration and radiology-pathology correlation are key components to advancing our knowledge and understanding of musculoskeletal disease and improving clinical care. The International Skeletal Society was founded on this principle and in its 50-year history it has successfully cultivated a globally recognized and respected Annual Meeting and Refresher Course to foster interest and share expertise in musculoskeletal disorders. The Society's consistent efforts for outreach and intersociety connections with MSK societies around the world have further strengthened its heritage. This look back on the Society's first 50 years recounts how it all started, where it has been, and provides insights on its promising future, not only in its support for education and scientific discovery, but also in its enrichment of precision medicine.

Radiologists should use the hip-knee-ankle angle rather than the mechanical axis deviation to describe knee alignment.

OBJECTIVE: Preoperative and postoperative coronal knee alignment is an important predictor of total knee arthroplasty (TKA) failure. Radiologists often report the mechanical axis deviation (MAD) rather than hip-knee-ankle angle (HKAA) to describe coronal knee alignment. The aim of this study is to evaluate (i) how well the MAD predicts the HKAA; (ii) if patient height and sex affect the performance of the MAD; and (iii) if the MAD could be measured faster than the HKAA. MATERIALS AND METHODS: Two hundred patients undergoing hip-to-ankle radiographs for TKA planning were retrospectively reviewed. The MAD and HKAA were measured using previously published methods by the Visage picture archiving and communication systems (PACS) tools. Receiver operator characteristic (ROC) curves were used to evaluate the performance of the MAD to predict HKAA by gender and height. The performance of a linear model was used to predict HKAA from MAD in a prospectively collected cohort of 40 patients. Paired t tests were used for the comparison of time measurement in MAD and HKAA in this cohort. RESULTS: MAD strongly correlated with HKAA (r = 0.99, p < 0.001); however, the performance of MAD differed by height (p = 0.005) and sex (p < 0.001). There was no significant difference in the time taken to measure HKAA versus MAD (p > 0.05). CONCLUSION: HKAA should be used instead of the MAD because it is more clinically relevant and takes the same amount of time to be measured.

Creating High Fidelity Synthetic Pelvis Radiographs Using Generative Adversarial Networks: Unlocking the Potential of Deep Learning Models Without Patient Privacy Concerns.

BACKGROUND: In this work, we applied and validated an artificial intelligence technique known as generative adversarial networks (GANs) to create large volumes of high-fidelity synthetic anteroposterior (AP) pelvis radiographs that can enable deep learning (DL)-based image analyses, while ensuring patient privacy. METHODS: AP pelvis radiographs with native hips were gathered from an institutional registry between 1998 and 2018. The data was used to train a model to create 512 × 512 pixel synthetic AP pelvis images. The network was trained on 25 million images produced through augmentation. A set of 100 random images (50/50 real/synthetic) was evaluated by 3 orthopaedic surgeons and 2 radiologists to discern real versus synthetic images. Two models (joint localization and segmentation) were trained using synthetic images and tested on real images. RESULTS: The final model was trained on 37,640 real radiographs (16,782 patients). In a computer assessment of image fidelity, the final model achieved an "excellent" rating. In a blinded review of paired images (1 real, 1 synthetic), orthopaedic surgeon reviewers were unable to correctly identify which image was synthetic (accuracy = 55%, Kappa = 0.11), highlighting synthetic image fidelity. The synthetic and real images showed equivalent performance when they were assessed by established DL models. CONCLUSION: This work shows the ability to use a DL technique to generate a large volume of high-fidelity synthetic pelvis images not discernible from real imaging by computers or experts. These images can be used for cross-institutional sharing and model pretraining, further advancing the performance of DL models without risk to patient data safety. LEVEL OF EVIDENCE: Level III.

Multiple myeloma: a review of atypical imaging features and other distinct plasma cell disorders that demonstrate similar imaging features.

Multiple osteolytic lesions are a well-recognized and typical imaging feature of multiple myeloma as well as several other plasma cell disorders. Given the high volume of imaging studies obtained of multiple myeloma patients, radiologists will likely encounter a subset of multiple myeloma patients with less common or "atypical" findings during their practice. These atypical findings include osteosclerotic lesions, extramedullary lesions, and amyloid deposition. Similar imaging findings that are considered atypical for multiple myeloma can also be detected in other plasma cell disorders that are distinct from multiple myeloma. For instance, POEMS syndrome is a distinct plasma cell disorder from multiple myeloma, but also can present with osteosclerotic lesions. This article reviews the atypical findings associated with multiple myeloma and also reviews other plasma cell disorders that can have a similar spectrum of imaging findings. Special attention is paid to the musculoskeletal imaging findings.

Epithelioid osteoblastoma with secondary aneurysmal bone cyst and FOS gene rearrangement.

Epithelioid osteoblastoma, sometimes equated with aggressive osteoblastoma, is a variant of osteoblastoma that typically demonstrates more worrisome imaging and pathological features compared to conventional osteoblastoma. These more aggressive features can overlap with those seen in osteosarcoma, creating a diagnostic challenge for radiologists and pathologists. Recent identification of FOS and FOSB gene rearrangements in osteoid osteoma and osteoblastoma has allowed for greater diagnostic confidence following biopsy, but careful radiological-pathological correlation remains a key component for guiding appropriate management. Although the imaging features of conventional osteoblastoma have been previously described, there are limited examples in the literature of the imaging appearance of epithelioid osteoblastoma, and none with secondary aneurysmal bone cyst. In this case report, we detail the clinical, imaging, and histological characteristics of a proximal femoral epithelioid osteoblastoma which was pathologically confirmed by FOS and FOSB genetic testing. The initial imaging impression favored a malignancy, but when the biopsy results were correlated in a multidisciplinary fashion with the imaging, epithelioid osteoblastoma became the leading diagnosis which was subsequently genetically confirmed. This case emphasizes the value of multidisciplinary radiology-pathology correlation in routine practice.

NTRK-rearranged spindle cell neoplasm of the lower extremity: radiologic-pathologic correlation.

Neurotrophic tyrosine receptor kinase (NTRK)-rearranged spindle cell neoplasm is a recently characterized soft tissue tumor and has been classified as provisional by the World Health Organization. Detection of the genetic rearrangement is important because these tumors are amenable to targeted tyrosine kinase inhibitor therapy, which can play a key role in patients with unresectable or advanced disease. Although the spectrum of histopathology associated with this entity is broad, one notable feature is the infiltrative growth pattern, which is most reminiscent of lipofibromatosis-like neural tumor. Description of their diverse histologic attributes has aided recognition, but so far little attention has been paid to correlating the gross appearance and imaging features of these lesions. In this report, we describe the clinical, imaging, histopathological, and genetic features of a soft tissue NTRK-rearranged spindle cell neoplasm. Inclusion of this more recently identified entity into the imaging differential of tumors with intratumoral relatively hypovascular nodules and infiltrative margins is important because testing for NTRK rearrangement is not routinely performed.

Society of Skeletal Radiology- white paper. Guidelines for the diagnostic management of incidental solitary bone lesions on CT and MRI in adults: bone reporting and data system (Bone-RADS).

The purpose of this article is to present algorithms for the diagnostic management of solitary bone lesions incidentally encountered on computed tomography (CT) and magnetic resonance (MRI) in adults. Based on review of the current literature and expert opinion, the Practice Guidelines and Technical Standards Committee of the Society of Skeletal Radiology (SSR) proposes a bone reporting and data system (Bone-RADS) for incidentally encountered solitary bone lesions on CT and MRI with four possible diagnostic management recommendations (Bone-RADS1, leave alone; Bone-RADS2, perform different imaging modality; Bone-RADS3, perform follow-up imaging; Bone-RADS4, biopsy and/or oncologic referral). Two algorithms for CT based on lesion density (lucent or sclerotic/mixed) and two for MRI allow the user to arrive at a specific Bone-RADS management recommendation. Representative cases are provided to illustrate the usability of the algorithms.

Dynamic stabilization home exercise program for treatment of thumb carpometacarpal osteoarthritis: A prospective randomized control trial.

STUDY DESIGN: Randomized control trial. INTRODUCTION: Thumb carpometacarpal (CMC) osteoarthritis (OA) is a common cause of hand pain and disability. Standard conservative therapy (SCT) for thumb CMC OA includes an orthosis and instruction in joint protection, adaptive equipment, and pain relieving modalities. The dynamic stability home exercise (HE) program is complementary conservative therapy designed to strengthen the stabilizing muscles of the thumb CMC. PURPOSE OF THE STUDY: To investigate whether the addition of HE to SCT (SCT+HE) was more effective at reducing pain and disability in thumb CMC OA compared to SCT alone. METHODS: The study compared 2 groups: SCT and SCT+HE. The SCT group received SCT with in-home pain management instructions, joint protection strategies with adaptive equipment, and a hand-based thumb-spica orthosis. The SCT+HE group received HE program instructions for adductor stretching and opponens and first dorsal interosseous strengthening in addition to SCT. Our primary outcome measure was the numerical rating scale (NRS) with secondary outcome measures of QuickDASH (shortened Disabilities of the Arm, Shoulder and Hand questionnaire), range of motion, grip strength, and pinch strength. Outcome measurements were assessed at first visit, 6 weeks, and 6 months. RESULTS: There was no statistical difference between the 2 groups for NRS and QuickDASH at 6 weeks (P = .28 and P = .36, respectively) or 6 months (P = .52 and P = .97, respectively). However, there was a statistically significant decrease in NRS and QuickDASH scores at 6 weeks and 6 months within both groups. CONCLUSIONS: Both SCT and SCT+HE are effective at reducing pain and disability in OA of the thumb CMC joint. Neither therapy program was superior to the other at improving NRS or QuickDASH scores at 6-week or 6-month follow-up.

CT Attenuation Values Do Not Reliably Distinguish Benign Sclerotic Lesions From Osteoblastic Metastases in Patients Undergoing Bone Biopsy.

BACKGROUND. CT attenuation thresholds that accurately distinguish enostoses from untreated osteoblastic metastases have been published. In the Mayo Clinic practices, these thresholds have been applied more broadly to distinguish benign sclerotic bone lesions other than enostoses from osteoblastic metastases. OBJECTIVE. The purpose of this article is to determine if CT attenuation thresholds allow the distinguishing of benign sclerotic bone lesions from osteoblastic metastases in patients undergoing bone biopsy. METHODS. A retrospective search was conducted to identify sclerotic lesions described on CT between October 7, 1998, and July 15, 2018, that underwent subsequent biopsy. Two musculoskeletal radiologists recorded lesions' maximum and mean attenuation. Using previously published attenuation thresholds, sensitivity and specificity for differentiating benign sclerotic lesions from osteoblastic metastases were calculated. ROC curve analysis was performed to determine if more appropriate attenuation thresholds exist. Intraclass correlation coefficients (ICCs) were computed. RESULTS. A total of 280 patients met inclusion criteria. Of those, 162 had malignant biopsy results and 118 had benign biopsy results. Of the 162 malignant lesions, 81 had received prior treatment. Maximum and mean attenuation were not significantly different between benign and malignant lesions for either reader (all p > .05). For reader 1, to distinguish benign from malignant lesions, a maximum attenuation threshold of more than 1060 HU resulted in sensitivity of 23.7%, specificity of 87.0%, and accuracy of 60.6%. A mean attenuation threshold of greater than 885 HU resulted in sensitivity of 19.5%, specificity of 90.7%, and accuracy 60.7%. ROC curve analysis showed AUCs for mean and maximum attenuation thresholds of 51.8% and 54.6%, respectively. Subgroup analyses of benign versus malignant and treated versus untreated lesions had similar results. Similar findings were obtained for reader 2. The two readers' ICC was 0.946 for maximum attenuation and 0.918 for mean attenuation. CONCLUSION. Published attenuation thresholds for distinguishing enostoses from osteoblastic metastases had slightly decreased specificity and markedly decreased sensitivity when applied to the differentiation of benign sclerotic lesions from osteoblastic metastases in our sample of biopsy-proven lesions. ROC analysis showed no high-performing attenuation threshold alternative. CLINICAL IMPACT. Published CT attenuation thresholds intended for distinguishing enostoses from osteoblastic metastases should not be used more broadly. More accurate alternative thresholds could not be derived.

Radiology-pathology correlation for bone and soft tissue tumors or tumor-like masses: single institutional experience after implementation of a weekly conference.

OBJECTIVES: To determine the frequency of non-diagnostic and discordant results from bone and soft tissue biopsies performed at our institution over a 3-year period and to investigate whether implementation of a weekly musculoskeletal radiology-pathology correlation conference decreased the time to appropriate patient management in cases of discordance. METHODS: Consecutive image-guided core needle biopsy results obtained over a 12 month period of time were reviewed in a retrospective fashion. Following implementation of the correlation conference, subsequent consecutive image-guided core needle biopsy results obtained over a 26 month period of time were reviewed in a prospective fashion. For non-diagnostic and discordant cases, the time in days from date of availability of the biopsy result to date of documentation of a specific follow-up action plan was recorded. RESULTS: Diagnostic yield was 96.5% and 94.9% for the retrospective and prospective periods, respectively. There were four discordant results in the retrospective cohort (1.7%) and seven discordant results in the prospective cohort (2.1%). Following implementation of the weekly correlation conference, there was significant decrease (p < 0.05) in median time from a discordant biopsy result to follow-up action plan. There were no unnecessary surgeries, litigation, or other unfavorable consequences in either cohort. CONCLUSION: Image-guided core needle biopsies of bone and soft tissue provide high diagnostic yield, often with specific diagnoses. The statistically significant decrease in number of days to follow-up action plan for discordant results suggests radiology-pathology review has a positive impact on patient care. Subjective benefits from communication and educational standpoints are also noteworthy.

A Case of Short Radiolunate Avulsion Injury: Magnetic Resonance Diagnosis and Surgical Reconstruction.

Injury to the volar wrist capsule with short radiolunate ligament avulsion is uncommon and is often difficult to discern on advanced imaging, which can lead to a delay in diagnosis and the development of chronic wrist instability. We report a case of a short radiolunate ligament avulsion injury and a volar wrist capsular injury that went unrecognized for an extended period and led to chronic wrist pain and instability. We describe the magnetic resonance imaging findings of the injury and detail a successful surgical reconstruction technique.

Society of skeletal radiology member utilization and performance of whole-body MRI in adults.

OBJECTIVES: To evaluate musculoskeletal (MSK) radiologist whole-body magnetic resonance imaging (WBMRI) practice patterns in an effort to better understand current MSK clinical utilization and the need for standardized coding. METHODS: A 12-question survey was created in Survey Monkey®. The survey was e-mailed to Society of Skeletal Radiology (SSR) members on September 19, 2018. The survey included questions on SSR member demographics and on their experience with WBMRI. RESULTS: One hundred sixty-four of 1454 (11%) SSR members responded to the survey. A minority (32%; n = 52/164) of respondents reported that their institutions routinely perform WBMRI. The most common indication was multiple myeloma (78%, n = 51/65). The most commonly utilized sequences were coronal short tau inversion recovery (STIR) (79%, n = 52/66) and coronal T1 without fat saturation (73%, n = 48/66). A large proportion of respondents (48%, n = 31/64) did not know the code used for billing WBMRI at their institutions. Of the remaining respondents, 23% (n = 15/64) reported use of the bone marrow MRI code, 16% (n = 10/64) the chest/abdomen/pelvis combination code, and 9% (n = 6/64) the unlisted MRI procedure code. CONCLUSION: There is variation in who is responsible for the protocol and interpretation of WBMRI, as well as how the exam is performed and how the exam is coded, which raise barriers to broad implementation. Recent WBMRI guidelines for multiple myeloma and prostate cancer can mitigate many of these barriers, but they do not address the coding and reimbursement challenges. Collaborative multi-society development of a new CPT® code for WBMRI may be a worthwhile endeavor.

Bone health of transgender adults: what the radiologist needs to know.

Sex steroids are important regulators of bone development before puberty and of bone homeostasis throughout adulthood. Gender-affirming therapies with sex steroids are used in transgender and gender diverse persons for treatment of gender dysphoria, which may have profound impacts on their bone metabolism. Many studies have described variable changes in bone density and geometry in transgender cohorts. In order to provide informed guidance on the effect of gender-affirming therapy, the International Society of Clinical Densitometry issued official position statements in 2019 for the performance and interpretation of dual-energy x-ray absorptiometry in transgender and gender-diverse patients. We review the effects of gender-affirming hormone therapy on bone physiology and the changes in bone modulation that have been reported in the literature in transgender patients who have received gender-affirming therapy. We also summarize the recent guidelines for interpretation of dual energy x-ray absorptiometry as an update for the radiologist.

Epithelioid schwannoma: imaging findings on radiographs, MRI, and ultrasound.

Epithelioid schwannoma is an uncommon benign peripheral nerve sheath tumor, with distinct morphological and pathological features. To our knowledge, the imaging features of epithelioid schwannoma have not been described. In this case report, we describe the imaging findings of a pathologically proven case of epithelioid schwannoma presenting as a slowly growing painless mass near the ankle. The MR imaging signs commonly associated with conventional schwannoma were absent. On correlative radiographs, there were intra-tumoral calcifications. Radiographs are an essential tool in the imaging evaluation of soft-tissue masses. Knowledge of soft-tissue tumor types that can be associated with intra-tumoral calcifications is helpful in honing the differential diagnosis.

Gout: Update on Dual-Energy Computed Tomography with Emphasis on Artifact Identification.

PURPOSE OF REVIEW: Gout is the most common inflammatory arthritis and is increasing in prevalence and incidence in many countries worldwide. Accurate diagnosis is important to direct treatment that may include chronic medication. Burden quantification and treatment monitoring are key in the effective care of patients with gout. This review highlights the positive impact of dual-energy computed tomography (DECT) on the evaluation of gout patients and discusses common imaging artifacts that limit this imaging modality. RECENT FINDINGS: DECT has become the most accurate imaging method for confirming or excluding gout. Of note, however, it has reduced sensitivity in early disease, including initial attacks. Burden quantification is another important role of DECT, which can now be performed using automated software methods, allowing for a more reliable assessment of treatment effect. However, the analysis of gout DECT images can be impeded by artifacts related to the DECT reconstruction technique. DECT is the most sensitive and specific imaging modality for diagnosis, burden quantification, and treatment monitoring in patients with gout. A working knowledge of common DECT artifacts is essential for mitigating their occurance and misinterpretation.

Current status of ultrasound and dual-energy computed tomography in the evaluation of gout.

Gout is the most common inflammatory arthritis and is increasing in relevance due to its rising prevalence and incidence. Dual-energy CT (DECT) and ultrasound (US) are the most frequently used imaging modalities for the diagnosis of gout and for the follow-up of patients receiving therapy. Although DECT has the highest diagnostic accuracy for gout and shows consistently excellent reader agreement in the assessment of urate deposition change after therapy, US also performs well and remains just as important an imaging tool in these realms due to its practical advantages in cost, availability, and safety. This article reports the current status of these two modalities in regard to diagnosis and therapy follow-up.

Nontuberculous Mycobacterial Infections of the Upper Extremity: 15-Year Experience at a Tertiary Care Medical Center.

PURPOSE: To present our experience with culture-positive, nontuberculous mycobacterial infections (NTMI) of the upper extremity and to compare the clinical features and outcomes of treatment among immunocompetent and immunocompromised patients. METHODS: All patients at our medical center diagnosed with NTMI of the upper extremity from December 1, 2000, through December 31, 2015, were included. We performed a retrospective analysis of patient demographic characteristics, delay to diagnosis, risk factors, clinical presentation, specific location, diagnostic testing, treatment regimens, and outcomes. These variables were compared between immunocompetent and immunocompromised patients. RESULTS: Forty-four patients were identified with culture-positive NTMI of the upper extremity. Of the patients, 27 (61%) were men (median age, 59 years [range, 23-83 years]). Twenty (45%) patients were immunocompromised. Immunocompromised patients had fewer known inoculation injuries compared with immunocompetent patients (45% vs 92%). A significant difference existed in the treatment regimens selected for immunocompetent versus immunocompromised patients: immunocompetent patients were more often treated with both antibiotics and surgery (88% vs 50%), whereas immunocompromised patients were more often treated with antibiotics alone (45% vs 4%). Overall, 24% experienced treatment failure and 9% died. Outcomes were relatively similar between immunocompetent and immunocompromised patients. A shorter delay to diagnosis was associated with a lower failure rate. CONCLUSIONS: Diagnosis of upper-extremity NTMI is often delayed because of indolent presentation and lack of clinical suspicion. The clinical presentation, diagnostic delay, and diagnostic testing results are similar between immunocompetent and immunocompromised patients. Although treatment varied significantly between patient groups, outcomes were similar. Timely diagnosis has the greatest impact on patient outcome. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.