ESTRO 2024 - Abstract Book

S5581

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

2513

Poster Discussion

Testing the feasibility of image matching prostate radiation therapy with online 2D MRI CINE imaging

Elizabeth Denney, Colin J Shelton, Pawel Drowd, Michèle Keane, Ina Katerina Nilo, Silvia Fabiano, Claudia Linsenmeier, Sophie Perryck, Stephanie Tanadini-Lang, Matthais Guckenberger, Lotte Wilke

University Hospital of Zurich, Radiation Oncology, Zürich, Switzerland

Purpose/Objective:

Using Viewray’s 0.35T MR-Linac (equipped with the A3i System), the position of the target volume is evaluated after daily online adaption with MRI 2D-coplanar images (CINE images) with a resolution of 0.35cm. This imaging technique is different from the standard initial MRI positioning True Fast Imaging with Steady-State Free Precession (TRUFI) scan with a resolution of 0.15cm. This study aims to evaluate the feasibility of image matching prostate cancer with online CINE images on a MR-Linac, and if it is comparable with image matching prostate cancer on a TRUFI scan.

Material/Methods:

112 fractions from 37 patients receiving daily online adaptive stereotaxic body radiation therapy (SBRT) prostate treatment (with or without an escalated dose to the dominant intraprostatic lesion (DIL)) were assessed. The SBRT dose fractionation for all patients were one of the following: 5x7Gy, 5x7.5Gy, 5x7.25Gy/8Gy (8Gy to the DIL), or 5x7.5Gy/8Gy (8Gy to the DIL). All patients received the standard treatment (an hour-long online adaptive treatment that involves initial patient positioning, initial positioning verification (TRUFI scan), contour adaption, planning adaption, final positioning verification (CINE images and final TRUFI scan), and finally the treatment with the standard image guided radiation therapy (IGRT) assessment. To compare the feasibility of matching the prostate on the CINE images, IGRT corrections from the CINE images were applied and the values were recorded. After applying the corrections, a final TRUFI scan was acquired and the IGRT corrections of matching the prostate were applied again. These values were also recorded. As exclusion criteria, when the IGRT corrections on the CINE images were greater than 0.20cm, the corrections were not applied and a TRUFI scan was directly acquired. These fractions were not recorded. The following data during the process was recorded daily:

• IGRT corrections from the CINE images • IGRT corrections from the TRUFI scan • Total length of treatment • Fractionation scheme

Results:

112 fractions from 37 patients receiving daily adaptive SBRT prostate radiation therapy were assessed. Table 1 outlines the mean absolute value IGRT corrections recorded daily during treatment.