Radiation Physics

PV QA 3 - Poster Viewing Q&A 3

TU_10_3214 - QA for SBRT of spine lesions: Introducing a novel 3D gel dosimeter for spatial and dosimetric end-to-end testing

Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3

QA for SBRT of spine lesions: Introducing a novel 3D gel dosimeter for spatial and dosimetric end-to-end testing
D. Saenz1, K. Rasmussen1, E. Pappas2, N. Kirby1, S. Stathakis1, Z. Shi Jr1, and N. Papanikolaou1; 1University of Texas Health San Antonio Cancer Center, San Antonio, TX, 2Department of Radiology and Radiotherapy, Technological Educational Institute of Athens, Athens, Greece

Purpose/Objective(s): The ability to localize precisely and deliver an accurate dose are the most critical components of spine SBRT. Due to the planned concavity of the dose distribution to avoid the spinal cord, these requirements create a demand for robust quality assurance tools. Gel dosimetry presents a unique advantage of measuring a three-dimensional dose distribution. The ability to deliver and measure the dose distribution in an end-to-end test is examined in this study.

Materials/Methods: A patient with a single lesion in the lumbar spine was used as a case study, and two 3D printed phantoms were created for the purpose of testing. One phantom was filled with gel and the other with openings for two ionization chambers, one in the target and one where the spinal cord sits. Treatment plans were developed in two different treatment planning systems. The plans were devised to cover the target with 18 Gy and keep the maximum point dose to the spinal cord below 14 Gy. Each plan was then delivered to both the gel phantom and the ionization chamber phantom. In addition, pre-treatment QA on a detector array was also performed.

Results: Gamma analysis for the pre-treatment QA on a detector array phantom showed 95.4% of measurement points passing the criteria of 3%/2mm agreement. For the ionization chamber measurement in the 3D printed spine phantom, 3% agreement was found between measurement and calculation for both the target and spinal cord ionization chamber measurements. The 3D gel phantom dose distribution agreed well with calculations with a 97% gamma passing rate using 3%/2mm criteria.

Conclusion: Gel dosimetry accomplishes the goal of verifying both dose and spatial accuracy for spine SBRT. We have demonstrated that this can be done with patient-modeled 3D-printed phantoms that can assure quality delivery of a treatment using an end-to-end test with high sensitivity to spatial and dosimetric errors.

Author Disclosure: D. Saenz: None. K. Rasmussen: None. E. Pappas: None. Z. Shi: None. N. Papanikolaou: Research Grant; BrainLab. site visitor for ACR Radiation Oncology Practice Accreditation; ACR. Speaker's Bureau; BrainLab. treasurer/secretary; Texas Radiological Society. medical physics advisory committee member; Texas Medical Board.

Send Email for Daniel Saenz


Assets

TU_10_3214 - QA for SBRT of spine lesions: Introducing a novel 3D gel dosimeter for spatial and dosimetric end-to-end testing



Attendees who have favorited this

Please enter your access key

The asset you are trying to access is locked. Please enter your access key to unlock.

Send Email for QA for SBRT of spine lesions: Introducing a novel 3D gel dosimeter for spatial and dosimetric end-to-end testing