A simple algorithm for planar image registration in radiation therapy

Abstract

A simple algorithm is presented for planar image registration and the method is applied to the simulator and portal image registration for patient setup verification in radiation therapy. Basically, the algorithm follows the concept proposed by Balter et al. [Med. Phys. 19, 329-334 (1992)], which converts the problem of open curve registration into matching a series of points along the curves. Balter's algorithm consists of three steps: (1) to determine a common starting point for each curve pair, (2) acquire two corresponding point sets along each curve, and (3) obtain a global transform matrix by matching two point sets. We integrate all three steps into one simple procedure which fits the sampled points along the intended curve pair by taking the relative path length shift as an independent fitting parameter. After being modified, the algorithm is able to take the different magnification factors of images into account, and it avoids curvature calculations. Numerical simulation as well as clinical and phantom images have been utilized to test the accuracy of the algorithm. The typical errors are less than 1 mm in translation and 1 degree in rotation. We also made a comparison study with the chamfer method. The results of the two methods agree to within 0.5 mm in translation and 0.5 degree in rotation.

A frequency‐based approach to locate common structure for 2D‐3D intensity‐based registration of setup images in prostate radiotherapy

“…A number of 2D-2D [14][15][16][17][18][19][20][21][22][23][24][25] and 2D-3D 12,13,26-35 registration methods have been proposed for the determination of setup errors in pelvic sites. Other 2D-3D registration methods developed for sites other than the pelvis but which use the correlation coefficient or mutual information include the work by Refs.…”

A new algorithm for the registration of portal images to planning images in the verification of radiotherapy, as validated in prostate treatments

“…3,4 Furthermore, the procedure is very time-consuming, which generally means that not all fractions will be verified: at our department the no action level 5,6 ͑NAL͒ protocol is used to decide which fractions will be verified. Most radiotherapy departments use interactive methods 5,[7][8][9][10][11][12][13][14][15][16] to aid the physician in matching the two images. For example, corresponding points in the two images are marked or contours in the images are manually drawn and these points or contours are then automatically matched.…”

Entropy-based dual-portal-to-3-DCT registration incorporating pixel correlation

“…Gilhuijs et al [18] utilize an arithmetic mean of the pixel values of the distance-transformed image as a cost function, whereas Leszczynski et al [29] utilize both the arithmetic mean and the root of mean square distance. Cai et al [9] proposed to register the simulator and the portal images by matching open curves extracted from the images. The dense-field methods, on the other hand, directly manipulate the pixel intensities, and hence, these methods are more robust to noise and blur in the portal images.…”