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

Purpose: To determine the added value of dynamic subtraction magnetic resonance (MR) imaging for the localization of prostate cancer. Materials and Methods: 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 precontrast images from corresponding post-contrast images of each phase was performed on the console. Results: 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, 0.69 cm³) was smaller than with T2-weighted images (n = 14, 1.05 cm³) or conventional dynamic images (n = 43, 0.71 cm³). Conclusion: 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.