Quantifying Patient Positioning Errors and Radiation Dose Variation in Cardiac Computed Tomography Angiography

Area of Science:

• Medical Imaging
• Radiological Physics
• Radiation Dose Optimization

Background:

• Accurate patient centring at the computed tomography (CT) scanner isocentre is crucial for minimizing radiation dose.
• Previous studies have highlighted the importance of precise patient positioning in CT examinations.

Purpose of the Study:

• To quantify patient positioning errors in cardiac CT angiography.
• To assess the relationship between these positioning errors and radiation dose.
• To estimate potential radiation dose reductions achievable through optimal patient centring.

Main Methods:

• Retrospective observational study of 399 adult patients undergoing ECG-gated cardiac CT angiography.
• Calculation of vertical and lateral deviations from the scanner isocentre using scout images and institutional dose monitoring software.
• Extraction of radiation dose indices (CTDIvol, DLP) from DICOM reports.
• Statistical analysis including correlation, multivariable regression, and simulation modeling.

Main Results:

• High prevalence of off-centring: 83% in anteroposterior (AP) and 50% laterally.
• Severe AP off-centring (>30 mm) in 39% of cases.
• No independent association between off-centring and radiation dose (CTDIvol, DLP) after adjusting for BMI, age, and sex.
• Male patients and higher BMI categories showed greater off-centring.

Conclusions:

• Patient off-centring is highly prevalent in cardiac CT.
• Adjusting for patient demographics and BMI, off-centring did not independently impact radiation dose.
• Scenario modeling suggests potential for significant radiation dose reduction (approx. 12%) with ideal centring, requiring prospective validation.