Study of feasibility of portal dosimetry in comparison with ImatriXX 2-D array system for IMRT and Rapid arc patient specific QA.

Abstract

-This study aimed to compare the Varian portal dosimetry system and the ImatriXX 2-D array system of IBA dosimetry for IMRT and Rapid arc patient specific quality assurance (QA). Fifteen cases of IMRT and fifteen cases of Rapid arc plans were selected for the patient specific QA study using portal dosimetry and ImatriXX 2-D array system. Planar dose comparison was carried out with gamma criteria of 3% -3 mm {dose difference and distance-to-agreement (DTA)}. For portal dosimetry system area gamma, average gamma and maximum gamma were analyzed and for the ImatriXX 2-D array system, the % of pixels passing the 3%-3mm gamma was chosen. In case of IMRT, the portal dosimetry mean values of area gamma, average gamma and maximum gamma were 1.01, 0.48 and 1.72 with standard deviation values of 0.38, 0.05 and 0.20 and for Rapid arc the corresponding values were 2.01, 0.48 and 1.72 with standard deviation of 0.54, 0.07 and 0.29. With the ImatriXX 2-D array system, on an average 99.22% of the pixels passed the criteria of 3%-3 mm with standard deviation of 0.58 for IMRT. For rapid arc, the average value was 97.14% with a standard deviation of 1.26. The results showed that both the systems can be use for patient specific QA measurements for IMRT and rapid arc. Portal dosimetry as well as ImatriXX measurements showed significant difference in gamma results of IMRT vs. rapid arc with pvalue less than 0.05. Compared to ImatriXX 2-D array system, the portal dosimetry values were more consistent. The portal dosimetry QA is less time consuming and in case of IMRT individual field verification is easier compared to ImatriXX 2-D array system.

Dosimetric Comparison Between Jaw Tracking and No Jaw Tracking in Intensity-Modulated Radiation Therapy

“…AS1200 detector has an active area of 40 Â 40 cm 2 with 1190 Â 1190 pixel arrays and pixel pitch of 0.336 mm which is suitable for both large-and small-field verification. [3][4][5] The treatment planning system is Eclipse v13. 6.…”

Dosimetric Comparison of a-Si 1200 and a-Si 1000 Electronic Portal Imager for Intensity Modulated Radiation Therapy (IMRT)

“…Although the primary purpose of EPID is to verify patient positioning, but with the introduction of on board imagers for image guidance the EPID has been more utilised for machine QA and pre-treatment patient specific QA [11][12][13][14]. Dosimetry using EPIDs or portal dosimetry has received considerable attention recently due to its relatively high-resolution of 0.392mm amorphous silicon (a-Si) flat-panel detector [15][16][17][18]. Several authors have extensively studied the dosimetric properties of a-Si 500 and a-Si 1000 EPID and its application in IMRT [19][20][21][22][23][24][25].…”