Immobilization versus no immobilization for pelvic external beam radiotherapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Techniques

Background:

• Pelvic radiotherapy is crucial for treating malignancies but is susceptible to patient positioning errors.
• Accurate patient positioning and immobilization are essential for effective radiotherapy delivery.
• Comparing different immobilization techniques is necessary to optimize treatment reproducibility.

Purpose of the Study:

• To determine the most reproducible patient positioning and immobilization technique for pelvic radiotherapy.
• To compare the accuracy and efficiency of three distinct immobilization methods.

Main Methods:

• Retrospective analysis of 65 patients undergoing pelvic external beam radiotherapy.
• Comparison of three techniques: no immobilization with leg separator, vacuum bag cushion (VBC), and Aquaplast system.
• Calculation and statistical analysis of systematic error, random error, and planning target volume (PTV) margins for each technique.

Main Results:

• No immobilization demonstrated the lowest systematic (2.42 ± 0.97 mm) and random (1.39 mm) errors.
• The VBC technique had the highest systematic errors (4.31 ± 3.84 mm), while Aquaplast had the highest random errors (3.59 mm).
• The no-immobilization technique yielded the smallest PTV margins (4.56 mm x, 4.69 mm y, 4.59 mm z).

Conclusions:

• The no-immobilization technique with a leg separator is the most reproducible method for pelvic radiotherapy.
• This technique results in the smallest planning target volume margins, enhancing treatment accuracy.
• The no-immobilization method is time-saving, cost-effective, and highly suitable for resource-limited settings.