A protocol for the reduction of systematic patient setup errors with minimal portal imaging workload

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy

Background:

• Accurate patient setup is crucial in radiotherapy to ensure precise dose delivery.
• Current off-line patient setup correction protocols, like the shrinking action level (SAL) protocol, can be resource-intensive.
• Minimizing portal imaging is desirable to reduce workload and patient dose.

Purpose of the Study:

• To evaluate a novel off-line patient setup correction protocol, termed the "no-action-level" (NAL) protocol.
• To compare the efficacy and efficiency of the NAL protocol against the widely used SAL protocol.
• To assess the potential of the NAL protocol in minimizing portal imaging requirements.

Main Methods:

• Two off-line protocols were compared: the shrinking action level (SAL) and the new no-action-level (NAL) protocol.
• The NAL protocol involves calculating the mean setup error over a fixed number of fractions and always applying a correction.
• Protocol performance was evaluated using a database of setup errors from 600 prostate patients and Monte Carlo simulations.

Main Results:

• The NAL protocol demonstrated significantly higher accuracy than the SAL protocol for comparable workloads.
• The SAL protocol required approximately three times more portal images than the NAL protocol to achieve similar systematic error reduction.
• The NAL protocol proved effective in reducing systematic errors in a real patient population.

Conclusions:

• The NAL protocol is more efficient than the SAL protocol for both measured and simulated setup data.
• Implementing the NAL protocol can lead to a substantial decrease in the number of required portal images.
• Reduced portal imaging translates to decreased workload and potentially lower radiation dose to healthy tissues.