Radiochromic film dosimetry of a high dose rate beta source for intravascular brachytherapy

Good clinical physics practice requires that dose rates of brachytherapy so urces be checked by the institution using them, as recommended by American Association of Physicists in Medicine Task Group 56 and The American Colleg e of Radiology. For intravascular brachytherapy with catheter-based systems , AAPM Task Group 60 recommends that the dose rate be measured at a referen ce point located at a radial distance of 2 mm from the center of the cathet er axis. AAPM Task Group 60 also recommends that the dose rate along the ca theter axis at a radial distance of 2 mm should be uniform to within +/- 10 % in the center two-thirds of the treated length, and the relative dose rat e in the plane perpendicular to the catheter axis through the center of the source should be measured at distances from 0.5 mm to R-90 (the distance f rom a point source within which 90% of the energy is deposited) at interval s of 0.5 mm. Radiochromic him dosimetry has been used to measure the dose d istribution in a plane parallel to and at a radial distance of 2 mm from th e axis of a novel, catheter-based, beta source for intravascular brachyther apy. The dose rate was averaged along a line parallel to the catheter axis at a radial distance of 2 mm, in the centered 24.5 mm of the treated length . This average dose rate agreed with the dose rate measured with a well ion ization chamber by the replacement method using source trains calibrated wi th an extrapolation chamber at the National institute of Standards and Tech nology. Ail of the dose rates in the centered 24.5 mm of a line parallel to the axis at a distance of 2 mm were within +/- 10% of the average. (C) 199 9 American Association of Physicists in Medicine. [S0094-2405(99)01711-3].