Clinical significance of multi-leaf collimator calibration errors

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Intensity-modulated radiotherapy (IMRT) relies on precise delivery of radiation beams.
• Multi-leaf collimator (MLC) calibration errors can potentially compromise treatment accuracy.

Purpose of the Study:

• To investigate the clinical impact of MLC calibration errors on head and neck (H&N), prostate, and lung stereotactic body radiotherapy (SBRT) treatment plans.
• To determine the threshold of MLC error that leads to significant deviations from planning criteria.

Main Methods:

• Retrospective analysis of five patient plans for each of the three treatment sites (H&N, prostate, lung SBRT).
• Intentional introduction of varying MLC errors (0.2 mm, 0.4 mm, 0.7 mm).
• Evaluation of plan quality based on planning target volume (PTV) criteria and mean PTV dose.

Main Results:

• MLC errors of 0.7 mm, 0.4 mm, and 0.2 mm were sufficient to cause major violations in PTV planning criteria for H&N, prostate, and lung SBRT, respectively.
• Mean PTV dose increased linearly with MLC error, with rates ranging from 3.2% to 5.9% per millimeter depending on the treatment site.

Conclusions:

• Sub-millimeter accuracy in MLC calibration is essential for safe and effective IMRT delivery.
• Robust MLC quality assurance programs are critical to minimize clinical impact and ensure patient safety in modern radiotherapy.