SU‐GG‐T‐306: Evaluation of Two‐Dimensional Diode Array Dosimeter for An Application of Exit Dosimetry

Abstract

Purpose: To characterize and evaluate the performance of MapCHECK™ two‐dimensional diode array dosimeter for accurate measurement of exit fluence at an extended source‐to‐surface distance (SSD) for the application of in vivo dosimetry based on dose reconstruction. Method and Materials: Dose profile measurements of open field for varying field sizes (3×3cm2, 5×5cm2, 7×7cm2 and 10×10cm2), air gaps (30cm, 40cm, 50cm and 60cm) and thicknesses of primary beam attenuator (10cm and 20cm of solid water) using MapCHECK™, CC04 ionization chamber and GafChromic® EBT radiochromic film were carried out. For clinical measurements, the 2D dosimetry measurements for five IMRT boost fields were carried out at an air gap of 50 cm with MapCHECK™, and compared with GafChromic® EBT radiochromic film, which served as the gold standard. Results: With increasing air gap, the difference between MapCHECK™ system and CC04 increased slightly for both primary beam attenuator thicknesses. For air gaps of 0cm, 30cm, 40cm, 50cm and 60cm, the overall agreement between MapCHECK™ and CC04 was ±1.25%, ±1%, ±2%, ±2.5% and ±4, respectively. The overall agreement averaged over all air gaps between MapCHECK™ system and CC04 was within ±2% while agreement between GafChromic® EBT radiochromic film and CC04 was ±3.5%. For the clinical IMRT fields and using the gamma test, the comparison between MapCHECK™ and GafChromic EBT radiochromic film yielded a mean passing rate of 91.9%, with a minimum and maximum passing rate of 87.6% and 97.2% respectively. Conclusion: MapCHECK™ yielded to have an accurate dose distribution (profile and 2D dose distribution) at an extended SSD (> 130cm). It can be considered a suitable candidate for exit dosimetry.