Determining intrafractional prostate motion using four dimensional ultrasound system.

Area of Science:

• Radiation Oncology
• Medical Imaging
• Prostate Cancer Treatment

Background:

• Accurate prostate positioning is crucial for effective radiotherapy.
• Intrafractional motion can impact treatment accuracy.
• Novel ultrasound technology allows for real-time motion monitoring.

Purpose of the Study:

• To evaluate the clinical significance of intrafractional prostate motion.
• To assess prostate displacement during typical radiotherapy treatment fractions.
• To investigate the correlation between Body Mass Index (BMI) and prostate motion.

Main Methods:

• Ten prostate cancer patients underwent transperineal ultrasound (US) monitoring during radiotherapy.
• Prostate motion was tracked for 2-2.5 minutes per fraction using the Clarity autoscan system.
• Data on motion in three orthogonal directions and Euclidean distance were analyzed.

Main Results:

• Mean maximal intrafractional displacements were small (e.g., 0.2 ± 0.9 mm superior/inferior).
• Fewer than 10% of fractions showed displacements exceeding 2.0 mm in any direction.
• No significant correlation was found between patient BMI and prostate displacement.

Conclusions:

• Intrafractional prostate motion is of minimal clinical consequence for short radiotherapy fractions (2-2.5 min).
• Prostate motion requires consideration for longer treatment delivery techniques like conventional or IMRT radiotherapy.
• Real-time ultrasound monitoring provides valuable data on intra-fractional prostate dynamics.