Risk assessment of a new acceptance testing procedure for conventional linear accelerators

Area of Science:

• Medical Physics
• Radiotherapy Equipment Quality Assurance

Background:

• Conventional linear accelerator (linac) acceptance testing procedures (ATPs) are time-consuming.
• New techniques utilizing electronic portal imaging devices (EPIDs) offer potential for more efficient and robust ATPs.

Purpose of the Study:

• To perform a comparative risk assessment of a new EPID-based ATP (ATP_EPID) versus the conventional ATP (ATP_conv).

Main Methods:

• Failure Modes and Effects Analysis (FMEA) was employed, following AAPM TG-100 guidelines.
• Five medical physicists assessed risks, comparing failure pathways and Risk Priority Numbers (RPNs) for both ATP approaches.
• RPNs > 100 were classified as high-priority failure modes.

Main Results:

• The ATP_EPID had 44% fewer failure pathways (233 vs. 534) and 35% fewer high-priority RPNs (40 vs. 114) compared to ATP_conv.
• Individual ATP tests showed 2.0x and 3.5x higher failure pathways and RPNs, respectively, for ATP_conv.
• The EPID pixel sensitivity map was identified as a key high-risk failure for ATP_EPID.

Conclusions:

• The largely automated ATP_EPID can mitigate human factor errors compared to ATP_conv.
• Manufacturers must address EPID pixel sensitivity map errors to prevent significant patient treatment impacts.