Objective The quality of all clinical MRI is dependent on B0 homogeneity, which is optimized during the shimming part of a prescan or preparatory phase before image acquisition. The purpose of this study was to assess shimming techniques clinically employed for breast MRI across our practice, and to determine factors that correlate with higher image quality for contrast-enhanced breast MRI at 1.5T. Methods One hundred consecutive female patients were retrospectively collected with Institutional Review Board approval. Shimming-related parameters, including shim-box placement and shimming gradient offsets were extracted from prior contrast-enhanced 3D fat-suppressed T1-weighted gradient echo image acquisitions. Three breast radiologists evaluated these images for fat saturation, breast density, overall image quality, and artifacts. Technologist experience was also evaluated for variability of shimming. Generalized linear mixed models were used to compare acquisition parameters between fat saturation. P < 0.05 was considered as statistical significance. Results The percentage of soft tissue inside the field of view (FOV) (ie, Tissue/FOV) in the good fat-saturation group (0.37 ± 0.06) was significantly lower (P < 0.01) than that in the poor fat-saturation group (0.39 ± 0.06). Other shimming-related parameters were found not significantly affecting the fat-saturation outcomes. Technologists with more experience tended to have less variable shimming performance than junior technologists did. Conclusions The quality of clinical MRI and especially breast MRI is highly dependent on shimming. Decreasing Tissue/FOV was associated with good image quality (good fat saturation). Optimization of shimming may require manual shimming or higher-order field-correction strategies.
In the era of digital breast tomosynthesis (DBT), the need for diagnostic mammography (MG) before a diagnostic ultrasound for masses recalled from screening tomosynthesis has been questioned. 1-3 Historically, most masses recalled from two-dimensional (2D) screening mammography underwent diagnostic mammography prior to ultrasound. 4,5 In this setting, diagnostic mammography views have been shown to increase the specificity of mammography by improving margin assessment, determining lesion location, and confirming persistence of the screen-detected mass. 5,6 In comparison to 2D imaging, DBT allows better differentiation of true findings from superimposition of fibroglandular tissue, increases mass margin visibility, and improves location assessment. 7-9 In addition, studies have shown that DBT has similar accuracy as routine diagnostic mammography for non-calcified findings, 10 is comparable to spot compression mammography for characterizing masses as benign or malignant, 1 and is equivalent or better than spot compression mammography for evaluating findings recalled from 2D screening mammography. 2,3,11 Currently, institutions and practitioners vary in how the work-up of masses recalled from screening tomosynthesis is performed, with some opting for ultrasound first and others performing diagnostic mammography before ultrasound. There are no clear American College of Radiology practice guidelines for work-up of DBT-detected masses. The purpose of this study is to compare outcomes of masses recalled from screening DBT worked-up initially with diagnostic mammography with those first evaluated with diagnostic ultrasound. MethodS and MaterIalS Study subjects, imaging technique, and interpretation Our Institutional Review Board approved this retrospective Health Insurance Portability and Accountability Act-compliant study. Informed consent was waived. We performed a retrospective review of our mammography reporting system for all screen-detected masses from July 1, 2017, from the time of our conversion to
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