Advanced MR imaging of bone marrow: quantification of signal alterations on T1-weighted Dixon and T2-weighted Dixon sequences in red marrow, yellow marrow, and pathologic marrow lesions.

OBJECTIVES: To quantify and compare signal intensity (SI) changes on T1-weighted (W) and T2W Dixon imaging in yellow marrow, red marrow, and bone marrow lesions. MATERIALS AND METHODS: A total of 141 patients (77 controls, 64 lesions-33 benign, 31 malignant) between January 2016 and December 2017 were retrospectively identified. For the control group, fixed 2-cm2 region of interests (ROI) were drawn at L5, bilateral ilium and femurs on in-phase and opposed-phase T1W and T2W Dixon images. For the lesion group, ROIs of best fit were drawn around each lesion on in-phase and opposed-phase T2W Dixon images. SI changes between in-phase and opposed phase maps for each group were compared. Inter-reader analysis was performed. RESULTS: Yellow marrow exhibited smaller SI changes as compared to red marrow on both T1W and T2W Dixon imaging at all locations (p < 0.0001) except at L5 on T2W Dixon imaging (p = 0.206). Both benign and malignant lesions showed significantly smaller SI changes as compared to both yellow (p = 0.0087, p < 0.0001) and red marrow (p = 0.0004, p < 0.0001) on T2W Dixon imaging. Malignant lesions exhibited smaller SI change as compared to benign lesions on T2W Dixon imaging (p = 0.0005). Signal intensity loss on both red and yellow marrow were smaller on T1W Dixon as compared to T2W Dixon (0.49-0.64, 0.27-0.31 vs. 0.70-0.74, 0.48-0.71). Inter-reader agreements were excellent (0.91-0.97). CONCLUSIONS: SI change calculated from T2-weighted Dixon imaging can adequately differentiate between yellow marrow, red marrow, and osseous lesions, both benign and malignant.

Subacromial impingement anatomy and its association with rotator cuff pathology in women: radiograph and MRI correlation, a retrospective evaluation.

OBJECTIVE: To evaluate the relationships between acromial anatomy and developmental alterations with rotator cuff tears in female patients and compare these parameters on radiographs and corresponding MRIs along with inter-reader performance. MATERIALS AND METHODS: Patient demographics, symptoms, and acromial characteristics on radiograph (acromial index, lateral acromion angle, subacromial space on AP and Y- views, acromial anterior and lateral downsloping) and MRI (shape, slope, spur, osteoarthrosis, os acromiale) were recorded. Radiographic and MRI findings were compared and correlated with rotator cuff pathology on MRI. Inter-reader analysis was performed. RESULTS: A total of 140 MRIs from 137 female patients were included. No significant correlation (p > 0.05) existed between acromial parameters and rotator cuff tears, except for a smaller subacromial space on the Y view and spurs correlated with subscapularis tendon tear (p = 0.02, p = 0.04). The presence of lateral downsloping on MRI correlated with a smaller lateral acromion angle (p = 0.0002) and the presence of lateral downsloping on radiography (p = 0.0015). Inter-reader agreements were good to excellent (ICC: 0.65-0.89). CONCLUSION: Subacromial impingement anatomy characteristics have no significant associations with supraspinatus or infraspinatus tears in symptomatic women. Among different measures, supine MRI can be reliably used to identify lateral downsloping of the acromion.

Does 3DMR provide equivalent information as 3DCT for the pre-operative evaluation of adult Hip pain conditions of femoroacetabular impingement and Hip dysplasia?

OBJECTIVE:: Femoroacetabular impingement (FAI) and hip dysplasia (HD) are frequently evaluated by isotropic CT (3DCT) for preoperative planning at the expense of radiation. The aim was to determine if isotropic MRI (3DMR) imaging can provide similar quantitative and qualitative morphological information as 3DCT. METHODS:: 25 consecutive patients with a final diagnosis of FAI or HD were retrospectively selected from December 2016-December 2017. Two readers (R1, R2) performed quantitative angular measurements on 3DCT and 3DMR, blinded to the diagnosis and each other's measurements. 3DMR and 3DCT of the hips were qualitatively and independently evaluated by a radiologist (R3), surgeon (R4), and fellow (R5). Interobserver and intermodality comparisons were performed. RESULTS:: The ICC was good to excellent for all measurements between R1 and R2 (ICC:0.60-0.98) and the majority of intermodality measurements for R1 and R2. Average inter-reader and inter-modality PABAK showed good to excellent agreement for qualitative reads. On CT, all alpha angles (AA) were significantly lower in dysplasia patients than in cam patients (p < 0.05). All lateral center-edge angle (LCEA) were significantly lower in dysplasia than in cam patients (p < 0.05). On MR, AA at 12, 1, and 2 o'clock, and LCEA at center were significantly lower in dysplasia patients than in cam patients (p < 0.05). CONCLUSION:: 3DMR offers similar qualitative and quantitative analysis as 3DCT in adult painful hip conditions. ADVANCES IN KNOWLEDGE:: 3DMR has good potential to replace 3DCT and serve as a one-stop modality for bone and soft tissue characterizations in the pre-operative evaluation of FAI and HD.

CCR4 promotes medullary entry and thymocyte-dendritic cell interactions required for central tolerance.

Autoimmunity results from a breakdown in central or peripheral tolerance. To establish central tolerance, developing T cells must enter the thymic medulla, where they scan antigen-presenting cells (APCs) displaying a diverse array of autoantigens. If a thymocyte is activated by a self-antigen, the cell undergoes either deletion or diversion into the regulatory T cell (T reg) lineage, thus maintaining self-tolerance. Mechanisms promoting thymocyte medullary entry and interactions with APCs are incompletely understood. CCR4 is poised to contribute to central tolerance due to its expression by post-positive selection thymocytes, and expression of its ligands by medullary thymic dendritic cells (DCs). Here, we use two-photon time-lapse microscopy to demonstrate that CCR4 promotes medullary entry of the earliest post-positive selection thymocytes, as well as efficient interactions between medullary thymocytes and DCs. In keeping with the contribution of thymic DCs to central tolerance, CCR4 is involved in regulating negative selection of polyclonal and T cell receptor (TCR) transgenic thymocytes. In the absence of CCR4, autoreactive T cells accumulate in secondary lymphoid organs and autoimmunity ensues. These studies reveal a previously unappreciated role for CCR4 in the establishment of central tolerance.