Clinical comparision of two image guidance methods for breast cancer treatment : 4D CBCT versus 2D PlanarView

• Main Authors: Peng-Hao Chen, 陳鵬壕
• Other Authors: Pao-Hsu Chang
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/mhz75g

碩士 === 高雄醫學大學 === 醫學影像暨放射科學系碩士在職專班 === 103 === Verification images are applied clinically before radiation treatment to ensure the accuracy of isocenter localization. The setup errors are recorded and corrected by calculating the displacement of the isocenter location on treatment setup and CT simulation. This study examined images of breast cancer patient was taken with the two most commonly used image-guided verification techniques, cone beam CT and X-ray orthogonal images. Localization errors in three axes (the caudal/cephalad, anterior/ posterior, and left/right axes) were recorded and analyzed. 11 patients with breast cancer were treated with image-guided radiotherapy with an Elekta Synergy linear accelerator. Images were taken with 4D CBCT and 2D X-ray prior to treatment. Magnitude of displacements along the three directional axes was measured. Distributions of the data were analyzed using Mann Whitney U test to define significance. Spearman’s rank correlation was used to measure the degree of association of these displacements between the two sets of images. From the analysis of the positioning X-ray orthogonal radiographs, results showed that the mean setup displacements and standard deviations were -0.05±2.45 mm, 1.83±4.38 mm, and -0.36±2.38 mm for left/right (X axis), cranial/caudal (Y axis) and anterior/posterior (Z axis) directions respectively. The mean setup displacements and standard deviations from the CBCT images when referenced to the CT simulation position were -0.12±1.97 mm, 0.65±4.52 mm and 0.64±2.08 mm for left/right (X axis)﹐cranial/caudal (Y axis) and anterior/posterior (Z axis) directions respectively. The p values for X,Y,Z axis calculated using Mann Whitney U test were 0.892, 0.003, and 0.0 for the two different sets of images. The Spearman rank correlation coefficient was 0.528, 0.741 and 0.345, with p values of 0, 0, 0.01 for X, Y, and Z axis respectively. For both image sets, the largest displacement was found in the cranial/caudal direction (Y axis). The variations along the Y axis and Z axis are statistically significant in 4D CBCT that take respiratory cycle in account and in 2D kV radiographs. Spearman''s rank correlation coefficient revealed a positively correlated relationship between the displacements along all the three axes from these two different image-guided techniques but differ in magnitude.