Prostate cancer: added value of subtraction dynamic imaging in 3T magnetic resonance imaging with a phased-array body coil

To determine the added value of dynamic subtraction magnetic resonance (MR) imaging for the localization of prostate cancer. We examined 21 consecutive patients who underwent MR imaging in 3T unit with a phased-array body coil and then had radical prostatectomy. After T2-weighted fast spin-echo imaging, we performed a contrast-enhanced dynamic 3D gradient-echo imaging consisting of pre-contrast, 2 successive early-phased (first imaging was started just after the appearance of contrast material in the aortic bifurcation followed by second imaging 35 seconds after the initiation of first imaging) and one 5-minute delayed post-contrast series. Subtraction of pre- contrast images from corresponding post-contrast images of each phase was performed on the console. On ROC analysis, the overall accuracy (Az value) of dynamic imaging combined with subtraction imaging was higher than T2-weighted imaging (p = 0.001) or conventional dynamic imaging alone (p = 0.074) for localization of cancer foci regardless of their zonal locations. Among pathologically verified 81 lesions, the mean volume of detected lesions with the subtraction images (n = 49, 0.69cm3) was smaller than with T2-weighted images (n = 14, 1.05cm3) or conventional dynamic images (n = 43, 0.71cm3). For localization of small prostate cancer, additional subtraction for the dynamic imaging could be superior to both T2-weighted imaging and un-subtracted dynamic imaging.