Standard edge detection algorithms versus conventional contouring for a three-dimensional CT-CT matching

In order to reduce uncertainties of patient set-up positioning, the Computerized Tomography (CT) images acquired at the treatment planning can be compared with those obtained during radiation dose delivery sessions. This insures dose delivery procedure as well as protects organ at risks located in the vicinity of tumor region. A method, based on the use of standard edge detection algorithms, developed to compare registered CT images with those acquired during treatment procedure. Several original CT images prepared from patients who underwent for prostate and head and neck cancers. The CT slices, in which the target volume was identified, were selected as reference CT images. The registered CT images were manipulated in transitional direction from 1 pixel to 5 pixels as well as an axial rotation was performed from 1 to 5 degrees. The difference in transition as well as the difference in rotation of the prostate body was evaluated through edge detection algorithms using an in-house code ritten in MATLAB. Results show that 1 pixel difference in transition and 1 degree difference in rotation can be recognized for inhomogeneous egions. Although, due to the lower contrast in soft tissues, the variation of the prostate body was not found to be clear, a significant variation was detected at the bony-soft tissue and air-soft tissue conjunction regions. The results obtained from the current study are comparable with those reported using Chamfer algorithm. It is concluded that the current method, can be used to control patient positioning in radiotherapy sessions as a part of Image guided radiotherapy protocols.

Standard edge detection algorithms versus conventional contouring for a three-dimensional CT-CT matching Keywords:

Edge detection algorithms , Transitional/rotational variation , CT-CT matching