Planar EPID-Based Dosimetry for SRS and SRT Patient-Specific QA

Abstract

The study’s purpose was to develop and validate Electronic Portal Imaging Device (EPID)-based dosimetry for Stereotactic Radiosurgery (SRS) and Stereotactic Radiation Therapy (SRT) patient-specific Quality Assurance (QA). The co-operation between extended Source-to-Imager Distance (SID) to reduce the saturation effect and simplify the EPID-based dosimetry model was used to perform patient-specific QA in SRS and SRT plans. The four parameters were included for converting the image to dose at depth 10 cm; dose-response linearity with MU, beam profile correction, collimator scatter and water kernel. The model accuracy was validated with 10 SRS/SRT plans. The traditional diode arrays with MapCHECK were also used to perform patient-specific QA for assuring model accuracy. The 150 cm-SID was found a possibility to reduce the saturation effect. The result of model accuracy was found good agreement between our EPID-based dosimetry and TPS calculation with GPR more than 98% for gamma criteria of 3%/3 mm, more than 95% for gamma criteria of 2%/2 mm, and the results related to the measurement with MapCHECK. This study demonstrated the method to perform SRT and SRT patient-specific QA using EPID-based dosimetry in the FFF beam by co-operating between the extended SID that can reduce the saturation effect and estimate the planar dose distribution with the in-house model.

Advances in Radiotherapy Dosimetry Techniques and Pre-Treatment Verification

“…Several studies have shown that EPID dosimetry is the most convenient tool for rapid and reliable patient-specific QA and can replace detector arrays in performing patient-specific QA of IMRT and VMAT, which can eliminate the need for phantom setup [47][48][49][50][51][52][53][54]. In 2019, Torres-Xirau et al [55] investigated the dose response of EPID in the presence of a magnetic field using Unity MR-linac (Unity, Elekta AB, Stockholm, Sweden).…”

A hybrid method to improve efficiency of patient specific SRS and SBRT QA using 3D secondary dose verification

“…Popular measurement-based methods for PSQA of lung SBRT plans include film, [7][8][9] multi-dimensional diode arrays, [10][11][12] high-resolution diode arrays, 10,13,14 and electronic portal imaging device (EPID) based QA. 12,[15][16][17][18] Due to the use of small field segments and steep dose gradients that are associated with lung SBRT plans, previous studies have demonstrated the need to use high resolution measurement methods to be able to detect potential errors through the use of stricter gamma criteria. 10,12,17 However, even with high resolution measurement devices, the sensitivity of measurement based QA to detect errors has been shown to be limited.…”

Clinical Efficacy of an Electronic Portal Imaging Device versus a Physical Phantom Tool for Patient-Specific Quality Assurance

“…An electronic portal imaging device (EPID) attached to the linear accelerator (LINAC) has a good resolution and a low volume-averaging effect; moreover, its setup is extremely simple [11][12][13]. Hence, the EPID can overcome the limitations of the array detector [14,15]. Furthermore, several research groups have verified its suitability as a patient-specific QA tool compared to commercial array detectors [13,16,17].…”