Coronal Curved Planar Reformation for Vertebra Localization in Pelvic Radiotherapy CT Images

The localization of the third lumbar (L3) vertebra is of clinical interest because quantitative analysis of skeletal muscle mass at the L3 vertebra is important for the assessment of postoperative recovery in patients with rectal cancer. A fully automated solution to reform a curved coronal plane is developed for localization of the L3 vertebra in pelvic radiotherapy CT images. The mid-sagittal plane is first identified, then the vertebral bodies are segmented. With the centers of the vertebral bodies are located, the anteroposterior position of the curved coronal plane is determined, followed by the reconstruction of the curved coronal plane. A radiotherapist is asked to evaluate the quality of the reformed curved planes. For the 282 CT images used in this study, the majority (70.2%, 198/282) of the curved coronal planes are rated as satisfactory or above. In conclusion, a curved planar reformation method is proposed in this study to display the entire lumbar vertebrae in one view for the reliable localization of the L3 vertebra. Future study will investigate the possibility of developing an automated procedure for L3 vertebra localization using therapeutic CT images.