(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: It is the first pre-clinical evaluation study of pre-release novel film, OrthoChromic OC-1, with suggested film processing protocols on clinical cases.
Methods: The OC-1 was tested using Eclipse v15.6 with Truebeam, Halcyon, and MultiPlan v5.3 with Cyberknife M6, respectively. The tested cases were chosen from clinical practices with varieties of treatment modalities with dose levels ranged from 2Gy to 85Gy. Orthochromic protocol requires two films and two plans. The single calibration film is exposed to calibration plan, with multiple dose levels in scan direction and uniform dose in lateral direction. QA film is exposed to patient specify QA plan, align parallel with calibration film in scan direction, the specific setup can correct the lateral effect from scanner sensor variation and film coating variation. The QA and calibration films are scanned in single session with Epson 12000Xl-GA flatbed scanner with parameter of 48bit, 75DPI and reflective type. Scanned Tiff image is imported to OrthoChrome Pro software, each of the two film areas is registered with corresponding planned dose dicom file, QA film compared with planned dose and gamma analysis is performed.
Results:
(1) OC-1 vs. wedge-calibration types: 4-level, 8-level step wedge and continuous wedge (EDW) are used for calibrations. 4-level calibration can reach 91.0% pass rate with 2mm 2%, continuous 99.4%, 8-level 99.5%. Therefore 8-level is used for the rest studies.
(2) OC-1vs. EBT3: The OC-1 can achieve 94.7% vs. EBT3 85.8% pass rate with 2mm/2% gamma index for Cyberknife SBRT prostate patient.
(3) OC-1 vs. treatment types: With the treatment types of IMRT and SBRT/SRS, all tested case with OC-1 can reach 90+% pass rate with 2mm/2% gamma index.
Conclusion:
Better performance than EBT3 with its robust protocol and automatic analyses, the pre-release OC-1 film can achieve consistent result in wide prescription dose range verified from 2Gy to 85Gy.
Keywords
Film, Quality Assurance, Stereotactic Radiosurgery
Taxonomy
TH- Radiation Dose Measurement Devices: Radiochromic film
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