Posted: Monday, November 14, 2022
Hassan Jassar, PhD, of the Medical College of Wisconsin, Froedtert Hospital, Milwaukee, and colleagues demonstrated the feasibility of accurate real-time motion monitoring of a liver tumor using a subliver volume as a tumor surrogate. This approach reportedly bypasses the difficulty posed by the invisibility of liver tumors on the T2/T1-weighted two-dimensional (2D) cine MRI without using a contrast agent. Additionally, the approach does not require implanting radio-opaque clips or approximating the whole liver motion as the tumor motion. These findings were presented at the 2022 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract 244).
The study analyzed patients with liver cancer who were treated with 1.5 T using an MRI imaging-guided linear accelerator. All patients were given a three-dimension mid-position image derived from a daily four-dimensional (4D) MRI to describe a subliver volume encompassing the tumor. During the same session, real-time 2D T2/T1-weighted balanced fast field echo cine MRI images were collected with free breathing during MR-guided adaptive radiation therapy. The cine images were acquired with a temporal resolution of 200 msec interleaved between coronal and sagittal orientations.
A total of eight patients were included in the study. Of them, six had mean (range) centroid motions of 8.8 mm in the superior-inferior direction, 1.5 mm in the left-right direction, and 3.2 mm in the anterior-posterior direction. Additionally, the six patients had mean shallow dose equivalent (range) values of 1.2 mm in the superior-inferior direction, 0.94 mm in the left-right direction, and 1 mm in the anterior-posterior direction. The mean of the maximum tumor motion from the 4D MRI was 8 mm in the superior-inferior direction, which was smaller than the centroid motion monitoring. According to the authors, this finding suggests the importance of motion capture using motion monitoring in real time. For the remaining two patients, quantitative motion monitoring was difficult to complete because of target deformation and large through-plane motion in the anterior-posterior direction.
Disclosures: Dr. Jassar reported no financial conflicts of interest.