Patient‐specific dose quality assurance of single‐isocenter multiple brain metastasis stereotactic radiosurgery using PTW Octavius 4D. Issue 9 (18th July 2020)

• Record Type: Journal Article
• Authors: McCulloch, James; Pawlowski, Jamie; Kirby, Neil; Rasmussen, Karl; Shi, Zheng; Myers, Pamela; Stathakis, Sotirios; Papanikolaou, Niko; Saenz, Daniel L.
• Is Part Of: Journal of applied clinical medical physics. Volume 21:Issue 9(2020)
• Page Start: 107
• Page End: 115
• Publication Date: 2020-07-18
• Subjects: multiple brain metastases -- patient specific -- quality assurance -- single isocenter -- stereotactic radiosurgery; Medical physics -- Periodicals; Clinical medicine -- Periodicals; Health Physics; Clinical Medicine; Electronic journals; Periodicals; Periodicals; Fulltext; Internet Resources; 610.153
• DOI: 10.1002/acm2.12979
• Languages: English
• ISSNs: 1526-9914

Abstract

Abstract: Purpose: Single‐isocenter multiple brain metastasis stereotactic radiosurgery is an efficient treatment modality increasing in clinical practice. The need to provide accurate, patient‐specific quality assurance (QA) for these plans is met by several options. This study reviews some of these options and explores the use of the Octavius 4D as a solution for patient‐specific plan quality assurance. Methods: The Octavius 4D Modular Phantom (O4D) with the 1000 SRS array was evaluated in this study. The array consists of 977 liquid‐filled ion chambers. The center 5.5 cm × 5.5 cm area has a detector spacing of 2.5 mm. The ability of the O4D to reconstruct three‐dimensional (3D) dose was validated against a 3D gel dosimeter, ion chamber, and film measurements. After validation, 15 patients with 2–11 targets had their plans delivered to the phantom. The criteria used for the gamma calculation was 3%/1 mm. The portion of targets which were measurable by the phantom was countable. The accompanying software compiled the measured doses allowing each target to be counted from the measured dose distribution. Results: Spatial resolution was sufficient to verify the high dose distributions characteristic of SRS. Amongst the 15 patients there were 74 targets. Of the 74 targets, 61 (82%) of them were visible on the measured dose distribution. The average gamma passing rate was 99.3% (with sample standard deviation of 0.68%). Conclusions: The high resolution provided by the O4D with 1000 SRS board insert allows for very high‐resolution measurement. This high resolution in turn can allow for high gamma passing rates. The O4D with the 1000 SRS array is an acceptable method of performing quality assurance for single‐isocenter multiple brain metastasis SRS.