An MRI based method for detection of microcalcifications in the human breast

Abstract

Purpose: This study evaluates a new magnetic resonance imaging method for detecting calcium deposits, using their characteristic susceptibility effects, in practical conditions to provide insight into its clinical value for detecting breast microcalcifications at high field (7T). Methods: Signatures of calcium deposits in phase images were detected via cross-correlation between the images and a library of templates containing simulated phase signatures of deposits. The influences of deposit position, signal-to-noise ratio, spatial resolution, high-pass filtering, and fat suppression on the method were determined and used to optimize the method for detecting simulated microcalcifications inserted in silico into breast MRI of healthy controls. Results: In images acquired with a clinical scanner and acquisition times below 12 minutes, simulated microcalcifications with sizes of 0.8 – 1.0 mm were detected in images with voxel sizes of (0.4 mm)3 and (0.6 mm)3 with sensitivity and specificity of 75-87% and 54-87%, respectively; smaller microcalcifications with sizes of 0.6 – 0.7 mm were detected better in images with voxel size of (0.4 mm)3, with sensitivity and specificity of 87% and 54%, respectively, than in images with voxel size of (0.6 mm)3, with sensitivity and specificity of 56-78% and 44-47%, respectively. Conclusions: The new method is promising for detecting large microcalcifications (approximately 0.8 – 1.0 mm in longest dimension) within the breast at 7T. Detection of smaller deposits may be possible in images with higher spatial resolution; unfortunately, these images take too long to acquire using current MR methods and therefore are clinically impractical. Although mammography can detect smaller microcalcifications with sensitivity between 74-95%, and specificity between 89-99%, this alternative MRI method does not expose breasts to ionizing radiation, is not affected by breast density, and can be combined with other quantitative MRI exams to increase the diagnostic specificity of breast MRI.