The study of palliative therapy for intranasal tumors in dogs (犬の鼻腔腫瘍における緩和療法に関する研究)

An ideal head-immobilization method provides a high level of accuracy and reproducibility in the immobilization. Various head-immobilization methods for radiotherapy have been published and are excellent in terms of accuracy; however, these methods are complicated to use and labor intensive. This study describes 2 new bite-block-type head-immobilization devices designed for greater stability and decreased vertical variation. The device designed in our previous study (“the bite-block-type head-immobilization device”; Device A) was modified by creating a groove on the upper surface of the horizontal plate (Device B) for a stable ventral–dorsal position or on the underside of the horizontal plate (Device C) for a stable dorsal–ventral position. These 3 devices were objectively compared with respect to setup time and accuracy of computed tomography (CT) images by 2 independent authors. Five healthy male beagles were used in this study. For each device, the setup time and variation in the coordinates were measured 5 times for each dog. The median setup time for Devices A, B, and C was 3.1, 1.6, and 2.3 min, respectively, showing that the groove modifications enabled reduced setup time (in Device B, by at least 50%). Moreover, three-dimensional analysis of the CT images revealed that the measurement variability of Device A (median, 1.3 mm) was significantly higher than that of Device C (median, 0.6 mm; p < 0.001). Collectively, our results show that use of a bite-block-type head-immobilization device