Assessment of large single-fraction, low-energy X-ray dose with radiochromic film

Purpose: To investigate the accuracy of in vivo dosimetry using radiochromi c film for large single-fraction, low-energy irradiations. Methods and Materials: Gafchromic MD-55-2 radiochromic film and LiF thermol uminescent dosimeters (TLDs) were placed in vivo on 25 patients to ascertai n their effectiveness for assessment of dose. All patients received 10 Gy s ingle fractions at energies ranging from 100 kVp (half-value layer [HVL] = 3.5 mm Al) up to 250 kVp (HVL = 2.3 mm Cu), Effects of small air gaps were also investigated using LiF TLDs and radiochromic film. Results: Radiochromic him adequately measured applied dose for 25 patients in vivo with a standard deviation of 5.5% from prescribed dose. LiF TLDs re corded a standard deviation of 4.1% from measured to applied dose, Small ai r gaps which can be created under the film or TLDs during in vivo dosimetry were shown to have a measurable but minimal effect on results for gaps les s than 5 mm, Conclusions: Gafchromic film has adequately measured applied dose in vivo a t low energy for large 10 Gy single-fraction irradiation. (C) 2000 Elsevier Science Inc.