Analysis of abdominal organ motion using four-dimensional CT

Abstract

Accurate individualized measurement of organ motion is the premise of defining internal margin (IM) for abdominal malignancies. This study was to assess the three-dimensional abdominal organ motion caused by respiration using four-dimensional computed tomography (4DCT), and to analyze the association between the movement of diaphragm and abdominal organs. The 4DCT scans of 13 patients with hepatocellular carcinoma were analyzed, five of whom had para-aortic lymph node metastases. The liver, kidneys, pancreas, spleen, and para-aortic lymph nodes were contoured in all 10 respiratory phases of 4DCT scans. The 3D movement of diaphragm and organs was calculated and the relationship between the movement of diaphragm and abdominal organs was analyzed. The average diaphragmatic movement was (10.3+/-4.0) mm with wide interpatient variations. Analysis of the center of the mass of abdominal organs revealed predominant cranio-caudal (CC) movement, with a mean of (10.1+/-3.9) mm for liver, (9.3+/-2.9) mm for left kidney, (9.6+/-4.1) mm for right kidney, (7.6+/-3.0) mm for pancreas, (10.6+/-3.3) mm for spleen, and (5.7+/-1.8) mm for para-aortic lymph nodes. The CC movement of the liver and the right kidney correlated well with the diaphragmatic movement, and no significant differences were observed. There was no significant correlation of the diaphragmatic movement to the CC movement of left kidney, pancreas and spleen. The movement of both kidneys was comparable, however, the movement of one kidney did not predict the movement of the contralateral one. The 4DCT scanning can accurately measure abdominal organ motion during whole respiration. The diaphragmatic mobility can approximate the CC movement of liver and right kidney, and the movement amplitude of para-aortic lymph nodes is much smaller than diaphragmatic mobility.