Computer-Based Methods for Matching and Comparison of Portal Image and Digitally Reconstructed Radiograph

The Radiotherapy is the clinical and scientific discipline devoted to the management of patients with cancer by the use of ionizing radiation or high energy X-ray. One of the most important steps in the Radiotherapy Process will be the Simulation Phase. This considers in first place the Treatment Planning which main tasks are the radiation dose calcultions and the beams placements. And in second place the Treatment Verification which considers the verification that the target coverage and the irradiation of healthy tissues agree with the Treatment Planning. The accurate patient positioning and beams alignment becomes crucial components in the Treatment Verification. This introduces an element of urgency in the developement of a computer model to permit the ability to set up accurately the patient just before the Treatment Delivery. This work proposes a computer model for the direct comparison of the Portal Image and the Mega voltage Digitally Reconstructed Radiograph of the corresponding Treatment Plan. The portal image represents the patient positioning in the moment of the treatment by the use of Electronic Portal Imaging Devices. For this purpose, the following steps are achieved: 1. Reconstruction of Digitally Reconstructed Radiographs at different energies from keV to MeV. 2. Importation of Electronic Portal Image to the Simulator software. 3. Development of image enhancement and filtering tools (e.g. contrast enhancement and edge detection ) to assist the management of Portal Images. 4. Development of methods for Spatial Transformations (e.g. rotation, scaling, translation). 5. Point Registration in the case of Open Field beams. 6. Contour Registration in the case of Field beams with blocks. 7. Blending of the Mega voltage Digitally reconstructed Radiograph and the Transformed Portal Image in the Fusion Image