Two-point Dixon fat-water swapping artifact: lesion mimicker at musculoskeletal T2-weighted MRI.

Fat-water swapping is an artifact specific to chemical shift encoded MRI and so-called Dixon methods. It is more frequent using the 2-point than the multi-point (> 2) Dixon method. Actually, fat-water swapping on the 2-point Dixon sequences partly triggered the development of the multi-point techniques. Fat-water swapping occurs on post-processing calculated fat- and water-only images, but not on the directly acquired in-phase and out-of-phase source images. It originates from a natural ambiguity between fat and water peaks that may cause inverted calculation between fat- and water-only voxels. Fat-water swapping artifact over large areas encompassing multiple tissues can easily be recognized, but it may be confusing when the calculation errors are limited to a single anatomic structure or a small area, especially on T2-weighted images. We report four cases with 2-point Dixon fat-water swapping artifacts mimicking musculoskeletal lesions at T2-weighted MRI and propose hints to avoid misinterpretation.

Lumbar pain with intracranial origin.

A 48-year-old woman presented low-back pain radiating to the lower right leg. Magnetic resonance imaging (MRI) of the lumbar spine revealed a L4-L5 subacute subdural hematoma (SDH). The patient had no general or local cause for this lumbar SDH, such as coagulation disorder, trauma, surgery, or lumbar puncture. She had a history of post-traumatic bilateral hemorrhagic contusions of the brain and intracranial SDH because of a fall occurring several months before the current problems. A downward migration of the cerebral SDH was found as only potential explanation of the lumbar SDH. The association between the intracranial and spinal hematomas is discussed.

Multimodality Imaging of Pelvic Inflammatory Disease Complicated with Tubo-Ovarian Abscess.

Teaching Point: Pelvic inflammatory disease (PID) is the most frequent gynecologic cause of emergency visits. Because of its prevalence and non-specific symptoms, the radiologist may encounter this pathology and its complications on all imaging modalities and should carefully assess PID signs to avoid delay in management, late complications, and unnecessary surgery.

Prolapsed Uterine Fibroid: Value of MRI in Case of Massive Bleeding.

Teaching Point: In case of acute bleeding caused by a mass located in the vagina, it may be difficult to assess the origin of the mass and determine whether it is benign or malignant; MRI is a useful tool for mass detection, diagnosis, and treatment decision.

BRCA1 Mutation: An Insidious Enemy with Multiple Facets .

Epidemiological studies suggest that around 10% of breast cancers are due to hereditary predisposition. The risk of cancer is exponentially increased in patients harboring BRCA1 or BRCA2 mutations. Cumulative breast cancer risk by age 80 is estimated to 72% for BRCA1 mutation carriers and 69% for BRCA2. The cumulative risk estimates for developing ovarian cancer by age 80 are 44% for BRCA1 mutation carriers and 17% for BRCA2. We present here the case of a 59-year-old woman who developed a left breast cancer in 2014 treated by conservative surgery, radiotherapy, and endocrine therapy with letrozole. The diagnosis of BRCA1 mutation was performed in 2015. In 2018, the patient was referred to our institution for treatment of an aggressive angiosarcoma developed in the same breast. She had undergone radical hysterectomy by the age of 49 years for a benign uterine pathology. In 2020, she developed a tumor in the gastric wall; histological analysis confirmed a serous papillary carcinoma of ovarian origin. She was treated - after gastrectomy and lymphadenectomy - with 6 courses of carboplatin and paclitaxel followed by olaparib therapy. In 2021, she suffered from a chest recurrence of high grade angiosarcoma. New resection with free margins was performed. We discuss the link between angiosarcomas and BRCA mutations, the therapeutic options for angiosarcoma and ovarian cancer of extra ovarian origin and the follow-up modalities.

Semi-quantitative CT scoring of nailed shaft fractures during normal healing and in non-unions: comparison with radiographic scoring.

PURPOSE: To compare tomographic (TUS) with radiographic (RUS) union scores in nailed shaft fractures during normal healing and in non-unions. METHODS: Two radiologists blinded to fracture age separately determined RUS and TUS in nailed femoral or tibial shaft fractures by analyzing the radiographic and CT examinations obtained in 47 patients during normal healing (early fracture group; 24 study participants, 17 men,19 tibias, mean fracture-CT delay 109 ±â€¯57 days [42-204 days]) and in surgically proven non-united fractures (late fracture group, 23 patients, 14 men, 12 tibias, mean fracture-CT delay 565 ±â€¯519 days[180-1983 days]). In both study groups, we determined the inter- and intra-observer agreement of RUS and TUS and compared TUS with RUS. RESULTS: Intra- and inter-observer agreement of RUS and TUS was very good in the early fracture group and good in the late fracture group for both readers. TUS correlated with RUS substantially in the early fracture group and only weakly in the late fracture group. TUS was statistically significantly lower than RUS in study participants with RUS ≥ 8 or 9 for R2 only and ≥ 10 for both readers in the early fracture group and in patients with RUS ≥ 8, 9 or 10 in the late fracture group for both readers. CONCLUSION: RUS and TUS of nailed shaft fractures during normal healing or in non-unions are both feasible and reproducible. They yield similar values in fractures with no or limited callus. TUS yields lower values than RUS in fractures with callus.

Semi-quantitative CT assessment of fracture healing: How many and which CT reformats should be analyzed?

PURPOSE: To assess how many and which CT reformats of long bone non-unions should be analyzed to best approximate the analysis of a larger number of CT reformats obtained in the three orthogonal planes. METHOD: We used 29 CT examinations of tibial or femoral non-unions to obtain 87 stacks of 7 CT reformats each in the coronal (n = 29), sagittal (n = 29) or transverse (n = 29) planes. Two independent radiologists scored two fracture sites on each CT reformat by using a Tomographic Union Score (TUS) (1: no callus, 2: non-bridging callus; 3: bridging immature callus; 4: bridging remodeled callus). The reference standard was the mean of the three TUS calculated from the cortical scores obtained on all the sagittal, coronal and transverse CT reformats. We determined the agreement (intra-class correlation coefficient (ICC) between the reference standard and 33 models combining one to seven CT reformats from one to three planes. The three best models were compared following a resampling procedure by a Wilcoxon's signed rank test. RESULTS: Three models combining two (mid-coronal and mid-sagittal), three (mid-coronal, mid-sagittal and mid-transverse) or four (two paramedian coronal and sagittal) CT reformats had the highest ICC (ICC ≥ 0.89) for both observers. After resampling, the model combining the two paramedian sagittal and coronal CT reformats statistically outperformed the two other models. CONCLUSION: Semi-quantitative analysis of the two paramedian sagittal and coronal CT reformats is an acceptable alternative to the analysis of more numerous reformats.

Fasciae of the musculoskeletal system: MRI findings in trauma, infection and neoplastic diseases.

The fascial system is a continuum of connective tissues present everywhere throughout the body that can be locally involved in a large variety of disorders. These disorders include traumatic disorders (Morel-Lavallée lesion, myo-aponeurotic injuries, and muscle hernia), septic diseases (necrotizing and non-necrotizing cellulitis and fasciitis), and neoplastic diseases (superficial fibromatosis, desmoid tumors, and sarcomas). The current pictorial review aims to focus on these localized disorders involving the fasciae of the musculoskeletal system and their appearance at MRI.

Value of a radiographic score for the assessment of healing of nailed femoral and tibial shaft fractures: A retrospective preliminary study.

OBJECTIVES: To assess the value of a radiographic score for the detection of delayed union in nailed fractures. METHODS: The modified radiographic union score (mRUS) values were determined by three separate radiologists on 259 radiographic sets of 58 nailed tibial or femoral fractures obtained at different timepoints after fracture (mean of 4.5 radiographic sets per fracture). A surgeon determined fracture outcome (normal or delayed union) at a mean of 192days after injury. Mean radiographic scores obtained at different timepoints after fracture were compared between fractures with normal or abnormal healing at follow-up. RESULTS: The mean score values increased significantly over time for fractures with normal healing for all readers (p<0.001). The mean score values determined 11-14 weeks after injury were higher in fractures with normal healing than in fractures with delayed union at follow-up (p<0.05). Scoring of radiographs obtained at about 3 months after injury or later enabled detection of fractures with delayed union with a sensitivity of 0.63-0.77 and a specificity of 1.0 (area under curve: 0.77- 0.88). CONCLUSIONS: The mRUS score can contribute to the detection of delayed union at a delay of about 3 months after injury in nailed shaft fractures.

Case Reports in Oncological Medicine Myoepithelioma: A New Rearrangement Involving the LPP Locus in a Case of Multiple Bone and Soft Tissue Lesions.

We report a case of multiple myoepithelioma with synchronous bone and soft tissue tumors, associated with a new genomic alteration of the LPP locus. The lesions occurred in the foot by presenting one lump in the plantar soft tissue, and three lesions were detected in the calcaneus and in the navicular bone. All tumors showed the double immunophenotype of epithelial markers and S100 protein expression. No rearrangement of the EWSR1 and FUS loci was detected as reported in myoepitheliomas. However, molecular karyotyping detected an unbalanced rearrangement of the LPP locus, not involving the HMGA2 locus, which is the most frequent translocation partner observed in benign mesenchymal tumors such as lipomas (of soft tissue as well as parosteal) and pulmonary chondroid hamartoma.

Fat suppression at 2D MR imaging of the hands: Dixon method versus CHESS technique and STIR sequence.

OBJECTIVE: To compare the effectiveness of fat suppression and the signal-to-noise ratio (SNR) of the Dixon method with those of the CHESS (Chemical Shift-Selective) technique and STIR (Short Tau Inversion Recovery) sequence in hands of normal subjects at 2D MR imaging. MATERIAL AND METHODS: 14 healthy volunteers (mean age of 29.4 years) consented to have both hands prospectively imaged with SE T1 Dixon, T1 CHESS, T2 Dixon, T2 CHESS and STIR sequences in a 1.5T MR scanner. Three radiologists scored the effectiveness of fat suppression in bone marrow (EFSBM) and soft tissues (EFSST) in 20 joints per subject. One radiologist measured the SNR in 10 bones per subject. Statistical analysis used two-way ANOVA with random effects, paired t-test and observed agreement to assess differences in effectiveness of fat suppression, differences in SNR and inter-observer agreement. RESULTS: EFSBM was statistically significantly higher for T1 Dixon than for T1 CHESS and for T2 Dixon than for T2 CHESS (p<0.0001). EFSBM was significantly higher for T2 Dixon than for STIR in the coronal plane (p=0.0020). The SNR was significantly higher for T1 Dixon than for T1 CHESS and for T2 Dixon than for STIR (p<0.0001). The SNR was significantly lower for T2 Dixon than for T2 CHESS (p<0.0001). CONCLUSION: The Dixon method yields more effective fat suppression and higher SNR than the CHESS technique at 2D T1-weighted MR imaging of the hands. At T2-weighted MR imaging, fat suppression is more effective with the Dixon method while SNR is higher with the CHESS technique.

Multirater agreement for grading the femoral and tibial cartilage surface lesions at CT arthrography and analysis of causes of disagreement.

OBJECTIVE: To assess the multirater agreement of the modified Outerbridge system for the grading of predefined areas of femorotibial cartilage at CT arthrography with multiple readers, with varying experience. DESIGN: Five readers with varying experience (two junior radiologists, three musculoskeletal radiologists including two experts in cartilage imaging) separately analyzed 962 cartilage sectors from pre-divided knee CT arthrograms with femorotibial osteoarthritis (Kellgren/Lawrence=3). Each cartilage area was graded twice by each reader, at a three-month interval, according to the modified 5-grade Outerbridge system. Interobserver and intraobserver agreement were assessed. After the second reading, 121 areas exhibiting the highest interobserver disagreement were reviewed in consensus to determine the sources of disagreement. RESULTS: The global interobserver agreement was fair (k=0.35), and increased with the grade (from k=0.14 to k=0.76 from grade 0-4). The intraobserver agreement varied with the readers' experience from moderate (k=0.59) to almost perfect (k=0.92). The majority of cases of disagreement (44%) was due to difficulties in assessing the normal variations of cartilage thickness, including diffuse cartilage thinning (23%) and normal variants of cartilage thickness (22%). 32% of cases of disagreement were due to retrospectively avoidable interpretation errors. CONCLUSIONS: The multirater agreement of the modified Outerbridge system is only fair when readers of different level of experience are taken into account, and interobserver agreement increases with readers' experience. However, interobserver agreement is substantial for grade 4 lesions. We report normal variations of cartilage thickness that may improve observer agreement in reporting cartilage lesions.

Self-resolving focal non-ossifying myositis: a poorly known clinical and imaging entity diagnosed with MRI.

BACKGROUND: Focal myositis is a rare benign inflammatory pseudotumor, presenting as a painful nodular mass within a muscle, and characterized by spontaneous resolution within weeks. PURPOSE: To assess the clinical and imaging findings of focal nodular myositis simulating a neoplasm at clinical examination, with no history of trauma. MATERIAL AND METHODS: This study describes the locations and appearance at ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI) of this condition in a series of five patients. RESULTS: MRI and US displayed a solid intramuscular "tumor" and suggested a continuum between the proximal and distal muscle fibers that appeared thickened within the nodular lesion, a sign that has been reported in myositis ossificans. MRI showed edema in adjacent muscles and soft tissues, as well as intense enhancement of the mass. Intense vascular flows were seen at Doppler analysis. CT did not reveal the appearance of peripheral ossifications, ruling out the diagnosis of myositis ossificans. In some patients, the diagnosis of sarcoma had been suggested as possible by the radiologist. Imaging follow-up with MRI showed complete resolution of the masses over several weeks, thus avoiding a biopsy; no recurrence was observed at long-term follow-up (more than 24 months). CONCLUSION: This paper highlights MRI and US findings in focal non-ossifying myositis, and emphasizes the role of MRI in suggesting this diagnosis, leading to the careful follow-up of the lesion until its resolution, and ruling out more aggressive lesions.