Digitally Reconstructed Radiograph Dosimetry: Introducing a New Application of Digitally Reconstructed Radiographs for Evaluation of Dose Distribution in Radiation Therapy.

PURPOSE: The digitally reconstructed radiograph (DRR) has traditionally been used for geometric radiation therapy (RT) treatment verification, with no reported dosimetric applications to date. This study aimed to introduce a methodology for the first time, allowing us to derive a dose distribution within an RT treatment plan using the DRR image.

METHODS AND MATERIALS: Initially, the correlation between the pixel values of the DRR image and the depth of the water phantom was established. Subsequently, the relationship between depth and absorbed dose was derived. By combining these 2 equations, the connection between the pixel values of the DRR and the absorbed dose was established. This approach was then used to calculate the dose distribution for homogeneous and RANDO phantoms. To verify the accuracy of this technique, the results were compared with the dose distribution from the treatment planning system.

RESULTS

The comparison of point doses at the isocenter of the RANDO phantom indicated differences of 1% and 2.4% for energies of 6 and 15 MV, respectively. A region-based dose distribution comparison using gamma analysis (3%-3 mm criteria) resulted in agreements of 98% and 95% for energies of 6 and 15 MV, respectively.

CONCLUSIONS

DRR dosimetry is an innovative method that employs DRR images to calculate dose distribution in RT planning, enhancing their traditional geometric use. It operates independently of a treatment planning system, making it a cost-effective solution that can run on personal computers. This approach acts as a supplementary tool, ensuring dosimetric verification and quality control in RT treatments.