Radiochromic film dosimetry: reflection vs transmission scanning.

The objective of this study was to compare the transmission and the reflection scanning reading modes of radiochromic MD-55 films of a document scanner. The use of the red channel of the red-green-blue images results in measurement accuracy that did not differ between the two reading modes. On the other hand, the scanner uniformity and temporal stability, the long-term stability of the film readings and the dynamic range is superior using the reflection mode. The dynamic range of dose measurements can be extended up to least 500 Gy using the alternative color channels by both reading techniques. Similar backscattering dose factors close to high Z inhomogeneities were found using both scanning modes. In conclusion, the use of reflection scanning mode of MD55 films was superior to the traditionally used transmission mode.