Glucagon

Patients underwent preoperative MRI with a 3T Philips Achieva MR system with a 6-channel cardiac phased array coil placed around the pelvis, and with an endorectal coil (Medrad eCoil, Bayer Healthcare). To limit peristalsis of the rectal wall 1mg dose of Glucagon (Glucagon, Eli Lilly & Co., Indianapolis) was injected prior to imaging. T2W images and multi echo T2W images were acquired, and only patients who underwent T2 mapping were included in the study. The echo times used were 90, 150, and 180 ms. The field-of-view was 160 mm x 160 mm and the matrix size was 212 x 212 with an in-plane resolution of 0.75 x 0.75 mm. The repetition time (TR) was 7.5 ms.

Patients underwent preoperative MRI with a 3T Philips Achieva MR system with a 6-channel cardiac phased array coil placed around the pelvis, and with or without endorectal coil (Medrad, Bayer Healthcare). For patients undergoing imaging using an endorectal coil, a 1mg dose of Glucagon (Glucagon, Eli Lilly & Co., Indianapolis) was injected prior to MR imaging to limit peristalsis of the rectal wall. T2W images and multi echo T2W images for T2 maps were acquired. The patients were randomly assigned to one of three groups (Group A–C). Group A (n = 15) was imaged without any endorectal coil using turbo spin echo (TSE) imaging pulse sequence for both T2W images and T2 mapping. Group B (n = 15) was imaged with an endorectal coil using TSE for both T2W images and T2 mapping. Group C (n = 15) was imaged with an endorectal coil using TSE for T2W images and the recently developed k-t-T2 sequence (18 (link)) for T2 mapping. Table 1 provides details of the imaging parameters used.
T2 maps were calculated using an in-house MATLAB (MathWorks, Natick, MA) program on a voxel by voxel basis from multi-echo T₂-weighted images using a mono-exponential signal decay model:
$$S=S_{0}exp(-TE/T_2)$$ where S is the signal at each echo time (TE) and S₀ is the extrapolated signal at TE = 0 ms.

All MR scans were performed with both an endorectal coil (Medrad, Warrendale, PA) and a phased-array surface coil by using either a 1.5T or 3.0T Achieva MR scanner (Philips Medical Systems, Eindhoven, Netherlands [n = 131]), or a 1.5T Excite MR scanner (GE Healthcare, Waukesha, WI [n = 30]). Immediately before the MR scan, 1 mg glucagon (Lilly, Indianapolis, IN) was injected intramuscularly to reduce peristalsis of the rectum. We imaged the entire prostate and oriented axial images to be perpendicular to the rectal wall, based on the sagittal images. A parallel imaging factor of 2 was utilized in all sequences. The following image types were obtained: axial, coronal, and sagittal T₂-weighted fast spin echo (FSE), axial T₁-weighted FSE, axial free-breathing diffusion-weighted imaging (DWI), and axial free-breathing dynamic contrast enhanced-MR (DCE-MR) imaging. Acquisition of DCE-MR images (of the entire prostate) started 30 seconds before intravenous bolus administration of 0.1 mmol/kg Gadodiamide (Omniscan, GE Healthcare, Princeton, NJ), which was followed immediately by a 20-mL saline flush at the rate of 2.0 mL/s. The total image acquisition time was ~45 minutes. Due to logistic reasons, MRI protocols were not identical for patients with PCa and patients without PCa. Detailed T₂-weighted imaging acquisition protocols are given in the Appendix.