[Analysis of abdominal organ motion using four-dimensional CT]

Area of Science:

• Medical Imaging
• Radiation Oncology
• Anatomical Motion Analysis

Background:

• Accurate measurement of abdominal organ motion is crucial for defining internal margins in abdominal cancer treatment.
• Respiration-induced organ motion necessitates precise assessment for effective radiotherapy planning.

Purpose of the Study:

• To evaluate three-dimensional abdominal organ motion during respiration using four-dimensional computed tomography (4DCT).
• To analyze the relationship between diaphragmatic movement and the motion of abdominal organs.

Main Methods:

• Analysis of 4DCT scans from 13 hepatocellular carcinoma patients.
• Contouring of liver, kidneys, pancreas, spleen, and para-aortic lymph nodes across 10 respiratory phases.
• Calculation of 3D organ movement and correlation with diaphragmatic motion.

Main Results:

• Average diaphragmatic movement was 10.3 mm, with significant interpatient variability.
• Predominant cranio-caudal (CC) movement observed in abdominal organs, with liver and right kidney showing strong correlation to diaphragmatic motion.
• Para-aortic lymph nodes exhibited smaller movement (5.7 mm) compared to diaphragmatic motion.

Conclusions:

• 4DCT provides accurate measurement of abdominal organ motion throughout respiration.
• Diaphragmatic mobility serves as a reliable indicator for the CC movement of the liver and right kidney.
• Para-aortic lymph node movement is significantly less than diaphragmatic excursion, impacting internal margin considerations.