Beyond Anatomy: Fat-Suppressed MR and Molecular Imaging of Spinal Pain Generators.

Spine pain is highly prevalent and costly, but evaluation with clinical features and anatomic imaging remain limited. Fat-suppressed MR imaging and molecular imaging (MI) may help identify inflammatory, lesional, and malignant causes. Numerous MI agents are available, each with advantages and disadvantages. Herein, FDG PET, prostate-specific membrane antigen (PSMA), bone radiotracers, and others are highlighted. No specific pain MI agents have been identified, but mechanisms of key agents are shown in video format, and the mechanism of PSMA as a theranostic agent is displayed. A multidisciplinary approach is needed to master this topic.

A Machine Learning Model Demonstrates Excellent Performance in Predicting Subscapularis Tears Based on Pre-Operative Imaging Parameters Alone.

PURPOSE: To develop a machine learning model capable of identifying subscapularis tears before surgery based on imaging and physical examination findings. METHODS: Between 2010 and 2020, 202 consecutive shoulders underwent arthroscopic rotator cuff repair by a single surgeon. Patient demographics, physical examination findings (including range of motion, weakness with internal rotation, lift/push-off test, belly press test, and bear hug test), and imaging (including direct and indirect signs of tearing, biceps status, fatty atrophy, cystic changes, and other similar findings) were included for model creation. RESULTS: Sixty percent of the shoulders had partial or full thickness tears of the subscapularis verified during surgery (83% of these were upper third). Using only preoperative imaging-related parameters, the XGBoost model demonstrated excellent performance at predicting subscapularis tears (c-statistic, 0.84; accuracy, 0.85; F1 score, 0.87). The top 5 features included direct signs related to the presence of tearing as evidenced on magnetic resonance imaging (MRI) (changes in tendon morphology and signal), as well as the quality of the MRI and biceps pathology. CONCLUSIONS: In this study, machine learning was successful in predicting subscapularis tears by MRI alone in 85% of patients, and this accuracy did not decrease by isolating the model to the top features. The top five features included direct signs related to the presence of tearing as evidenced on MRI (changes in tendon morphology and signal), as well as the quality of the MRI and biceps pathology. Last, in advanced modeling, the addition of physical examination or patient characteristics did not make a significant difference in the predictive ability of this model. LEVEL OF EVIDENCE: Level III, diagnostic case-control study.

Retrospective evaluation of MRI findings in arthroscopically confirmed cases of hypermobile lateral meniscus.

OBJECTIVE: To identify preoperative MRI findings in patients with arthroscopically confirmed hypermobile lateral meniscus utilizing a standard MRI knee protocol, with comparison to normal control and lateral meniscal tear groups. SUBJECTS AND METHODS: All patients with arthroscopically confirmed hypermobile lateral meniscus diagnosed at our institution were retrospectively identified. The following structures were evaluated on preoperative knee MRIs: superior and inferior popliteomeniscal fascicles, lateral meniscus and meniscocapsular junction, popliteal hiatus, and soft tissue edema around the popliteal hiatus. The same MRI features were evaluated in the normal control and lateral meniscal tear groups. RESULTS: Study, normal control, and lateral meniscal tear patients (18 each) were included. In the study group, 94.4% had superior popliteomeniscal fascicle abnormality, 89.0% had inferior popliteomeniscal fascicle abnormality, and 72.2% had lateral meniscal abnormality. Incidence of these abnormalities was significantly higher than in the normal control group. Meniscal abnormalities in the study group all involved the posterior horn meniscocapsular junction, 12/13 of which had vertical signal abnormality at the junction and 1/13 with anterior subluxation of the entire posterior horn. Popliteus hiatus measurements were largest in the lateral meniscal tear group. CONCLUSION: In patients with hypermobile lateral meniscus, the combination of popliteomeniscal fascicle abnormality and vertical signal abnormality at the meniscocapsular junction was seen in the majority of patients. Popliteomeniscal fascicle signal abnormality without identifiable lateral meniscal injury was the next most common imaging appearance. Radiologists may provide valuable information by suggesting the diagnosis of hypermobile lateral meniscus in such cases.

Multimodality evaluation of transfascial muscle and other soft tissue herniations of the extremities.

This review illustrates the multimodality assessment of transfascial muscle and other soft tissue herniations of the extremities. Transfascial herniations of the extremities can develop from congenital or acquired disruptions of the deep fascia, resulting in herniation of the underlying muscle, nerve, or soft tissue tumor into the subcutaneous tissues. While most patients present with a painless subcutaneous nodule that may change in size with muscle activation, some may experience focal or diffuse extremity symptoms such as pain and paresthesias. Although the diagnosis may be clinically suspected, radiologic evaluation is useful for definitive diagnosis and characterization. Ultrasound is the preferred modality for initial workup through a focused and dynamic examination. Magnetic resonance imaging can be utilized for equivocal, complicated, and preoperative cases. Computed tomography is less useful in the evaluation of transfascial herniations in the extremities due to similarities in the attenuation between muscle and fascia, which can decrease the conspicuity of small defects.

Advantages of CT Versus MRI for Preoperative Assessment of Osteochondritis Dissecans of the Capitellum.

BACKGROUND: Magnetic resonance imaging (MRI) is considered to be the gold standard for imaging of osteochondritis dissecans (OCD). PURPOSE/HYPOTHESIS: The purpose was to determine the additional value of a preoperative computed tomography (CT) scan in adolescent patients with capitellar OCD of the elbow. Consistent with the fact that OCD is a lesion involving the subchondral bone, the hypothesis was that CT would be superior to MRI for imaging OCD of the capitellum. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 3. METHODS: All patients being treated surgically for an OCD of the capitellum between 2006 and 2016 at one institution were reviewed for preoperative imaging. A total of 28 patients met the inclusion criteria. Corresponding MRI and CT scans were compared retrospectively. Multiple parameters were recorded, with special emphasis on OCD lesion size, fragmentation, and tilt as well as joint surface integrity, loose bodies, and osteophytes. RESULTS: The OCD lesions were best seen on CT scans, whereas MRI T1-weighted images overestimated and T2-weighted images underestimated the size of defects. A subchondral fracture nonunion was found on CT scans in 18 patients, whereas this was seen on MRI T1-weighted images in only 2 patients (P < .001) and MRI T2-weighted images in 4 patients (P < .001). Fragmentation of the OCD fragment was found on CT scans in 17 patients but on MRI scans in only 9 patients (P = .05). Osteophytes as a sign of secondary degenerative changes were seen on CT scans in 24 patients and were seen on MRI scans in 15 patients (P = .02). Altogether, only 51 of 89 secondary changes including loose bodies, effects on the radial head and ulnohumeral joint, and osteophytes that were seen on CT scans were also seen on MRI scans (P = .002). CONCLUSION: OCD fragmentation and secondary changes were more often diagnosed on CT. These factors indicate OCD instability or advanced OCD stages, which are indications for surgery. In an adolescent who is considered at risk for OCD (baseball, gymnastics, weightlifting, tennis) and who has lateral elbow joint pain with axial or valgus load bearing, CT is our imaging modality of choice for diagnosing and staging OCD of the capitellum.

Deep learning-based virtual noncalcium imaging in multiple myeloma using dual-energy CT.

BACKGROUND: Dual-energy CT with virtual noncalcium (VNCa) images allows the evaluation of focal intramedullary bone marrow involvement in patients with multiple myeloma. However, current commercial VNCa techniques suffer from excessive image noise and artifacts due to material decomposition used in synthesizing VNCa images. OBJECTIVES: In this work, we aim to improve VNCa image quality for the assessment of focal multiple myeloma, using an Artificial intelligence based Generalizable Algorithm for mulTi-Energy CT (AGATE) method. MATERIALS AND METHODS: AGATE method used a custom dual-task convolutional neural network (CNN) that concurrently carries out material classification and quantification. The material classification task provided an auxiliary regularization to the material quantification task. CNN parameters were optimized using custom loss functions that involved cross-entropy, physics-informed constraints, structural redundancy in spectral and material images, and texture information in spectral images. For training data, CT phantoms (diameters 30 to 45 cm) with tissue-mimicking inserts were scanned on a third generation dual-source CT system. Scans were performed at routine dose and half of the routine dose. Small image patches (i.e., 40 × 40 pixels) of tissue-mimicking inserts with known basis material densities were extracted for training samples. Numerically simulated insert materials with various shapes increased diversity of training samples. Generalizability of AGATE was evaluated using CT images from phantoms and patients. In phantoms, material decomposition accuracy was estimated using mean-absolute-percent-error (MAPE), using physical inserts that were not used during the training. Noise power spectrum (NPS) and modulation transfer function (MTF) were compared across phantom sizes and radiation dose levels. Five patients with multiple myeloma underwent dual-energy CT, with VNCa images generated using a commercial method and AGATE. Two fellowship-trained musculoskeletal radiologists reviewed the VNCa images (commercial and AGATE) side-by-side using a dual-monitor display, blinded to VNCa type, rating the image quality for focal multiple myeloma lesion visualization using a 5-level Likert comparison scale (-2 = worse visualization and diagnostic confidence, -1 = worse visualization but equivalent diagnostic confidence, 0 = equivalent visualization and diagnostic confidence, 1 = improved visualization but equivalent diagnostic confidence, 2 = improved visualization and diagnostic confidence). A post hoc assignment of comparison ratings was performed to rank AGATE images in comparison to commercial ones. RESULTS: AGATE demonstrated consistent material quantification accuracy across phantom sizes and radiation dose levels, with MAPE ranging from 0.7% to 4.4% across all testing materials. Compared to commercial VNCa images, the AGATE-synthesized VNCa images yielded considerably lower image noise (50-77% noise reduction) without compromising noise texture or spatial resolution across different phantom sizes and two radiation doses. AGATE VNCa images had markedly reduced area under NPS curves and maintained NPS peak frequency (0.7 lp/cm to 1.0 lp/cm), with similar MTF curves (50% MTF at 3.0 lp/cm). In patients, AGATE demonstrated reduced image noise and artifacts with improved delineation of focal multiple myeloma lesions (all readers comparison scores indicating improved overall diagnostic image quality [scores 1 or 2]). CONCLUSIONS: AGATE demonstrated reduced noise and artifacts in VNCa images and ability to improve visualization of bone marrow lesions for assessing multiple myeloma.

Biphasic squamoid alveolar renal cell carcinoma: Cytologic features of a rare entity.

Biphasic squamoid alveolar renal cell carcinoma is a newly described rare morphologic variant of papillary renal cell carcinoma. Its characteristic histomorphology and immunophenotype have been well described in the literature. Namely, BSARCC is composed of a dual-cell population with nests of larger squamoid cells surrounded by a single layer of cuboidal cells in alveolar arrangements. Invariably, the squamoid component expresses cyclin D1. More recently, MET alterations have been identified within a subset of BSARCC, raising the possibility for targeted MET inhibitor therapy. To the best of our knowledge the cytomorphologic features of BSARCC have yet to be described. Herein we correlate the cytologic features (percutaneous image-guided fine needle aspiration) of BSARCC to its corresponding histomorphology and immunophenotype (core needle biopsy).

Mammary analogue secretory carcinoma: A challenging case arising in a young man with radiation exposure.

Mammary Analogue Secretory Carcinoma (MASC) is a recently described salivary gland tumor frequently sampled via fine-needle aspiration. The cytologic features of MASC are not entirely distinctive and can simulate acinic cell carcinoma, but the tumor harbors an ETV6 gene rearrangement resulting in an ETV6-NTRK3 fusion gene. We present a case of MASC arising in a 31 year old man with a history of multiple radio-embolization procedures.

Malignant gastrointestinal neuroectodermal tumor: Cytologic, histologic, immunohistochemical, and molecular pitfalls.

Malignant gastrointestinal neuroectodermal tumor (GNET) is a rare malignant primary gastrointestinal mesenchymal tumor which can be diagnosed via fine-needle aspiration (FNA) cytology. In the context of FNA, the diagnosis requires a cell block and the use of significant resources including immunohistochemical stains and molecular testing. The differential diagnosis of GNET includes clear cell sarcoma (CCS), gastrointestinal stromal tumor (GIST), gastric schwannoma, metastatic melanoma, malignant perivascular epithelioid cell tumor (PEComa) and granular cell tumor, among others. Here we describe a case which was initially diagnosed as malignant granular cell tumor by FNA which was later revised to GNET following the finding of an EWSR1-ATF1 fusion gene rearrangement.

Impact of flow pattern, body mass index, and age on intraprocedural fluoroscopic time and radiation dose during sacroiliac joint injections.

PURPOSE: Understanding all factors that may impact radiation dose and procedural time is crucial to safe and efficient image-guided interventions, such as fluoroscopically guided sacroiliac (SI) joint injections. The purpose of this study was to evaluate the effect of flow pattern (intra- vs. periarticular), patient age, and body mass index (BMI) on radiation dose and fluoroscopy time. METHODS: A total of 134 SI joint injections were reviewed. Injectate flow pattern, age, and BMI were analyzed in respect to fluoroscopy time (minutes), radiation dose (kerma area product (KAP); µGy m2), and estimated skin dose (mGy). RESULTS: BMI did not affect fluoroscopy time, but increased BMI resulted in significantly higher skin and fluoroscopy doses (p < 0.001). There was no association between fluoroscopy time and flow pattern. Higher skin dose was associated with intraarticular flow (p = 0.0086), and higher KAP was associated with periarticular flow (p = 0.0128). However, the odds ratios were close to 1. There was no significant difference between fluoroscopy time or dose based on patient age. CONCLUSION: Increased BMI had the largest impact on procedural radiation dose and skin dose. Flow pattern also showed a statistically significant association with radiation dose and skin dose, but the clinical difference was small. Proceduralists should be aware that BMI has the greatest impact on fluoroscopy dose and skin dose during SI joint injections compared to other factors.

MR arthrogram of the postoperative glenoid labrum: normal postoperative appearance versus recurrent tears.

OBJECTIVE: The purpose of this study is to describe the MR arthrogram appearance of the postoperative glenoid labrum and to describe the features consistent with recurrent tear. MATERIALS AND METHODS: We identified 30 patients who had undergone glenoid labral repair, had a subsequent MR arthrogram of his or her shoulder, and went on to repeat shoulder arthroscopy. Each MR arthrogram was reviewed blindly, and the glenoid labrum was described as normal, irregular, or torn. Additional findings recorded included the presence or absence of a paralabral cyst and suture anchors in the glenoid. The operative report was also reviewed for each patient to determine the status of the labrum at arthroscopy. RESULTS: Following consensus review, 18/30 MRIs were felt to demonstrate recurrent glenoid labral tear, 11/30 showed an irregular labrum, and 1/30 was called normal. The radiology impression regarding the presence or absence of a recurrent glenoid labral tear agreed with the operative report in 24/30 (80%) cases, and was discrepant in six. This equals 83.3% sensitivity and 81.8% specificity of MR arthrogram in the diagnosis of recurrent labral tear in this study. A paralabral cyst was present in 3/30 (10%) cases, all three of which were torn. CONCLUSIONS: MR arthrogram findings of signal equal to gadolinium or fluid within or underlying the glenoid labrum and markedly diminutive or absent labrum were the most useful features to diagnose recurrent tear. Some signal underlying the labrum, which is confined to the anterosuperior quadrant, may be normal. The secondary finding of a paralabral cyst was also highly sensitive for recurrent tear.

Subfascial fat herniation: sonographic features of back mice.

Three adult patients are described with sonographic features of subfascial fat hernation. Each patient presented to the musculoskeletal ultrasound department at our institution for the evaluation of a palpable mass of the low back. Subfascial fat hernation, also known as back mice and fibro-fatty nodule, are an uncommon cause of a palpable mass in the low back or low back pain. They are small mobile subcutaneous nodules in a characteristic location near the posterior superior iliac spine. This entity has not been described in the radiology literature. These cases are presented in order to demonstrate the sonographic findings of back mice and to describe key anatomic features.

Patellar calcar: MRI appearance of a previously undescribed anatomical entity.

OBJECTIVE: The femoral calcar is a constant anatomical structure within the proximal femur representing a condensation of bone trabeculae. It is our impression that a similar structure is present within the patella. The purpose of this retrospective study was to define the prevalence, appearance, location, and configuration of the patellar calcar on MRI examinations. MATERIALS AND METHODS: One hundred consecutive unenhanced knee MRIs were retrospectively reviewed by two readers who were blinded to the clinical indication. The patellar calcar was defined as a dark signaling, linear or curvilinear structure subjacent to the patellar articular surface. If present, the patellar calcar was assigned to a "well seen," "moderately well seen," or "faintly seen" category. Location of the calcar within the patella, orientation, configuration, and thickness were recorded. Confounding variables, such as marrow edema, patellar chondromalacia, bipartite patella, or postoperative changes were also recorded. RESULTS: The patellar calcar was visualized in 81 out of 100 (81 %) MRIs. When detected, the calcar was well seen in 20 out of 81 (25 %), moderately well seen in 35 out of 81 (43 %), and faintly seen in 26 out of 81 (32 %). The anteroposterior width of the calcar measured at its thickest segment was: < 1 mm in 43 out of 81 (53 %), 1 mm in 28 out of 81 (35 %), and >1 mm in 10 out of 81 (12 %). CONCLUSION: The patellar calcar was seen in the majority of knee MRIs and had a consistent imaging appearance. The calcar may be obscured by degenerative arthrosis of the patella and rarely may mimic patellar stress fracture or osteochondritis dissecans. Radiologists and clinicians should be familiar with this normal anatomical structure.