SU‐E‐T‐263: MRI‐Guided Targeted Prostate Cancer Radiation Therapy: Multi‐Image Co‐Registration

Purpose: MRI has been used for guiding treatment planning and post‐treatment evaluation in prostate cancer targeted radiation therapy. However, the co‐registration of MR images to CT or ultrasound images needs manual adjustment due to the motion of the pelvic organs. To improve the accuracy of the co‐registration of MR images to CT or ultrasound images, we investigated the use of simultaneous image co‐registration of multiple MR images to CT or ultrasound images utilizing MIM™ software. Methods: Multiple MR images, including T1 without and with Gd‐contrast agent, T2, and diffusion weighted images were acquired using the same preview image allowing MR images to be inherently co‐registered. By using MIM™ image fusion software, multiple MR images were simultaneously fused with either CT or ultrasound image. Adjustment of CT/MR image co‐registration uses the best contrast information from one or multiple MR images at each micro‐structure location. The alignment of individual MR image was then adjusted to account for their individual contrast characteristics. Results: Thirty seven prostate cancer patients were studied using this image co‐registration method. By using this strategy, T2‐weighted MR images can be accurately matched to CT images with <2 mm of the prostate margin. Newly acquired T1‐weighted MR images can be fused accurately to pelvic bones, prostate and pelvic lymph nodes. However, the alignment of the rectum, bladder, and bowel can vary. Conclusion: The simultaneous multiple MR image co‐registration technique provides a strategy of efficient multiple MR image co‐registration, while improving the accuracy of image co‐registration. This image co‐registration technique has also been used in other locations, such as the spine.