Comments on "Quantitative evaluation of radiochromic film response for two-dimensional dosimetry" [Med. Phys. 24, 223-231 (1997)].

It was with interest that I read the article by Zhu et al., especially the part concerning the inherent variation of optical density across the film which the author concluded is likely due to a nonuniform dispersion of the radiochromic sensitive dye rather than an artifact of the scanning technique. I agree with the author on this point as we had performed the same examinations. However, we must have received ‘‘a good batch’’ as the variations seen across all our films, performing the same experiments where less than 1% in one direction and less than 2.5% in the other direction with a single irradiation technique. We received two packets of the new MD55/2 Gafchromic film with batch No. 941206. All ten sheets were tested with a 1.5 cm strip taken from each sheet in both directions. Examples are shown in Figs. 1 and 2 after 40 Gy applied dose. The results shown were measured on a Scanditronix RFA300 densitometer, converted to read in the visible region with a wavelength of 760 nm610 nm. Results are converted to a percentage dose normalized to 100% at the