Intrafractional gastric motion and interfractional stomach deformity using CT images

Area of Science:

• Radiation Oncology
• Medical Imaging
• Gastrointestinal Oncology

Background:

• Accurate radiation therapy (RT) for gastric lymphoma requires precise targeting of the stomach.
• Understanding gastric motion is critical for determining appropriate treatment margins.
• Previous studies have not fully quantified both intrafractional and interfractional gastric motion.

Purpose of the Study:

• To evaluate intra- and interfractional gastric motion using repeated CT scans.
• To determine the necessary treatment margins for gastric radiation therapy.
• To assess the impact of fasting and simulated RT delivery on stomach volume.

Main Methods:

• Six gastric lymphoma patients underwent repeated CT scans before RT.
• Stomach center coordinates (X, Y, Z) were analyzed to quantify motion.
• CT scans were matched to bony anatomy for accurate comparison.
• Treatment margins were calculated based on systematic and random errors.

Main Results:

• Average intrafractional motion: -12.1 mm (SI), 2.4 mm (LAT), 4.6 mm (VD).
• Average interfractional motion: -4.1 mm (SI), 1.9 mm (LAT), 1.5 mm (VD).
• Required margins: 15.9 mm (SI), 31.0 mm (LAT), 29.6 mm (VD).

Conclusions:

• Both intrafractional and interfractional gastric motion are considerable.
• Significant margins are necessary for effective gastric radiation therapy.
• Fasting and simulated RT delivery help minimize stomach volume.