Interobserver image registration variability impacts on stereotactic arrhythmia radioablation (STAR) target margins

Area of Science:

• Medical Imaging
• Radiation Oncology
• Cardiac Imaging

Background:

• Stereotactic arrhythmia radioablation (STAR) requires precise targeting.
• Cardiac computed tomography (CT) is used for treatment planning.
• Interobserver variability in image registration can impact treatment accuracy.

Purpose of the Study:

• To quantify interobserver variability in cardiac CT image registration.
• To determine necessary margins for STAR targeting considering this variability.

Main Methods:

• Ten experts registered cardiac CTs to planning CTs for 15 patients.
• Registrations involved automated and manual adjustment steps.
• Margins were calculated to encompass observer and automated targets.

Main Results:

• Manual registration averaged 5 minutes, 55 seconds.
• Automated registration required a 6 mm expansion for 95% overlap.
• Manual registration required a 4 mm expansion for 95% overlap in most cases, with some requiring up to 9 mm.

Conclusions:

• Cardiac CT to planning CT registration adds ~3 mm uncertainty to STAR targeting.
• Treatment planning workflows must incorporate this uncertainty into target margin assessments.