Electronic Portal Image processing for high precision radiotherapy

The advent of a-Si Electronic Portal Imaging Device (EPID) has led to an important tool for the clinicians to verify the location of the radiation therapy beam with respect to the patient anatomy. However, the Electronic Portal Images (EPI) are blur and suffer from low contrast due to Compton Scattering. It is difficult to differentiate between the organs and tissues from low contrast images. We need better in-treatment images to extract relevant features of the anatomy for a reliable patient set-up verification. The goal of this research work was to inspect several image processing techniques for contrast enhancement and edge detection/sharpening on EPI in DICOM format and improvise their visual aspects for better diagnosis and intervention. We propose a hybrid approach to enhance the quality of electronic portal images by using CLAHE algorithm and median filtering followed by image sharpening. Results suggest impressive improvement in the image quality by the proposed method. To quantify the degree of enhancement or degradation for various techniques experimentally, metrics like RMSE and PSNR are compared.