Individually wide range of renal motion evaluated by four-dimensional computed tomography

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiology

Background:

• Accurate assessment of organ motion is vital for optimizing radiation therapy delivery.
• Intensity-modulated radiation therapy (IMRT) and stereotactic body radiation therapy (SBRT) require precise targeting to minimize dose to healthy tissues.
• Understanding renal motion is particularly important for abdominal RT due to the proximity of kidneys to common treatment targets.

Purpose of the Study:

• To quantify physiologic renal motion using four-dimensional computed tomography (4DCT).
• To evaluate the correlation between renal motion and patient demographics.
• To inform the optimization of abdominal IMRT and SBRT techniques.

Main Methods:

• Twenty patients underwent CT simulation and 4DCT acquisition.
• Thirty-nine kidneys were contoured across ten respiratory phases to estimate motion.
• Statistical analysis was performed to assess correlations with age, sex, height, and weight.

Main Results:

• Renal motion was not significantly related to patient age, sex, height, or body weight.
• Average renal motion was 11.1 mm (craniocaudal), 3.6 mm (anterior-posterior), and 1.7 mm (right-left).
• Renal motion strongly correlated with respiratory phases in all directions (r > 0.97, p < 0.01).

Conclusions:

• Renal motion is primarily driven by respiration and is independent of demographic factors.
• Significant individual variability exists in cranio-caudal renal motion.
• Individualized assessment of renal respiratory motion is essential for effective radiation therapy planning.