A four-dimensional computed tomography analysis of multiorgan abdominal motion

Area of Science:

• Medical imaging and radiation oncology.
• Computational anatomy and biomechanics.

Background:

• Accurate radiation therapy for abdominal tumors requires understanding organ motion.
• Respiration-induced motion significantly impacts target volume delineation and dose delivery.

Purpose of the Study:

• To quantify multiorgan respiration-induced motion in liver and pancreatic cancer patients.
• To analyze motion characteristics of clinical target volumes and organs at risk.

Main Methods:

• Acquired four-dimensional computed tomography (4D CT) scans for 18 patients.
• Utilized deformable registration to propagate organ contours across respiratory phases.
• Extracted motion metrics (center of mass, bounding box) from 3D organ models.

Main Results:

• Liver clinical target volumes exhibited average superior-inferior motion of 9.7 mm (SD 5 mm).
• Pancreatic tumors showed average motion of 5 mm (SD 1 mm).
• Abdominal organs moved in unison with varying amplitudes; gating reduced motion range by ~10x.

Conclusions:

• Deformable registration effectively calculates four-dimensional organ trajectories.
• Motion quantification provides critical data for radiation therapy planning.
• Results offer insights into inter-organ motion dynamics during respiration.