Mismatch in Breast and Detector Size during Screening and Diagnostic Mammography Results in Increased Patient Radiation Dose

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When using mammographic detectors of different sizes, it can be difficult to match patient breast size to optimal detector size. We studied whether a mismatch between breast size and optimal detector size resulted in increased radiation exposure. All screening and diagnostic (Dx) mammography patients during a 6-week period in November-December 2009 (864 patients) were evaluated (institutional review board exemption for quality assurance studies). Data gathered included breast size (large or small), detector size used, number of views obtained, mean glandular dose (MGD) per breast, and patient waiting time. Average MGD and average waiting time was calculated for imaging performed on appropriately matched or mismatched breast size-detector size pairs. Screening mammography patients with large breasts imaged on a small detector received a significantly higher radiation dose (4.9 vs. 3.3mGy, P<.05) and a greater number of views (5.9 vs. 4.6, P<.05) compared to optimally matched breast-detector pairs. Dx mammography patients with large breasts imaged on a small detector received a higher radiation dose (8.2 vs. 6.7mGy, P<.05) compared to optimally matched breast-detector pairs, although without an increased number of views. Waiting times were longer for a large detector. A mismatch in breast-detector sizes results in a significantly greater radiation dose to patients with large breasts imaged on a small detector. Pressure to minimize patient waiting time may inadvertently result in increased radiation dose. Detector size should be matched to breast size whenever possible, but particularly for patients with larger breast sizes.