Development of A Novel Image Guidance Alternative for Patient Localization using Topographic Images for TomoTherapy

17th International Conference on the Use of Computers in Radiation Therapy

物理学;计算机科学

Sharon Qi, X.^1 ; White, Benjamin^1 ; Low, Daniel A^1

Department of Radiation Oncology, University of California Los Angeles, Los Angeles, CA, United States^1

关键词: Anterior posteriors;    Cranial caudal direction;    Localization errors;    Multileaf collimators;    Patient localization;    Radius of curvature;    Scanning parameters;    Topographic imaging;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/489/1/012078/pdf
DOI  :  10.1088/1742-6596/489/1/012078

学科分类：计算机科学（综合）

来源: IOP

【 摘 要 】

To develop a faster and lower dose topogram based image registration for TomoTherapy as an alternative image guidance tool to volumetric megavoltage computed tomography (MVCT). Topogram procedures were performed for an anthropomorphic thorax phantom on a TomoTherapy HD unit (Accuray Inc., Sunnyvale, CA) using couch speeds from 1-4 cm/s and gantry angles of 0 and 90 degrees, other scanning parameters are: 1 mm imaging jaw, compression factor of 1, 30 seconds scanning duration with all multileaf collimators (MLCs) open. The raw exit detector data was exported after each scan. The topogram was reconstructed from a fan beam source for TomoTherapy beam and detector geometry at a SSD of 85 cm. A reference image, so called Digitally Reconstructed Topogram (DRT) was created by integrating the trajectories through the kVCT simulation with the topogram geometry. Image registration was performed by visually aligning the bony structure in topogram to the DRT. Image resolution was determined by the radius of curvature for the detector array, source to axis distance, source to detector distance, detector spacing, and number of detectors. The localization errors were 1.5, 2.5 mm in medio-lateral and anterior-posterior direction, larger errors in cranial-caudal direction was observed for faster couch speeds (i.e., ≥3cm/s). The topographic imaging time was 30 sec (versus 3-5 minutes for MVCT thorax scan) with imaging dose less than 1% of MVCT scan. Topograms with appropriate couch speed provide reliable patient localization images while significantly reducing pre-treatment imaging time. Topogram can be used as an alternative and/or additional patient alignment tool to MVCT on TomoTherapy.