Determination of redundant scan coverages along the Z-axis and dose implications for common paediatric computed tomography imaging examinations in a limited resource setting.

Introduction: Optimizing scan parameters, particularly along the Z-axis, is crucial for minimizing unnecessary medical radiation exposure. Understanding and mitigating redundant scan coverages is essential for enhancing the safety and efficacy of paediatric CT imaging. This study quantified redundant Z-axis scan coverage and evaluated its associated dose implications in paediatric CT examinations in a limited-resource healthcare setting.

Methods: A retrospective review was conducted on 279 paediatric CT scan records from two large tertiary hospitals in Ghana. Distances above the upper target and below the lower target of selected anatomical regions were measured using calibrated callipers on the CT console. The National Cancer Institute Dosimetry System for Computed Tomography (Monte Carlo-based software) was used to simulate the scanning situations and organ-dose implications.

Results: In all, 87.3% of the CT scans had redundancies ranging from 0.77 ± 0.42 to 2.34 ± 1.22 cm for head, 1.43 ± 2.36 to 5.64 ± 3.00 cm for chest and 4.86 ± 3.01 to 6.75 ± 4.28 cm for abdominopelvic CT scans. Optimizing the scan length to the appropriate anatomical boundaries reduced the total dose-length product of neonates and middle-aged children by 27.9% and 26.1% respectively for chest CT scans, and 26.2% for infants during abdominopelvic CT scans. Optimal scan length selection for chest CT examinations resulted in organ-dose reductions of 57.5%, 56.1%, 63.6% and 73.8% for the thyroid glands, heart wall, lungs and breasts respectively.

Conclusion: The study demonstrates a high prevalence (87.3%) of redundant scan coverage in paediatric CT examinations, with significant variances across different body sites. Implementing optimized scan lengths could substantially reduce radiation exposure and significantly lower organ doses.