A Multiinstitutional Study on Wasted CT Scans for Over 60,000 Patients.

Area of Science:

• Radiology and Medical Imaging
• Health Informatics
• Radiation Safety

Background:

• Repeated imaging in CT exposes patients to unnecessary radiation, impacting satisfaction and increasing costs.
• Limited data exists on repeat and reject rates specifically for CT examinations.
• Standardized analysis of repeat rates is crucial for optimizing CT protocols and patient care.

Purpose of the Study:

• To develop and validate an automated algorithm for quantifying CT repeat-reject rates.
• To compare repeat rates between academic and rural healthcare settings.
• To identify specific protocols, technologists, and indications associated with higher repeat rates for targeted interventions.

Main Methods:

• A retrospective analysis of 61,102 CT examinations from 2015-2018 using an automated algorithm.
• Utilized DICOM metadata to identify and classify repeat CT acquisitions.
• Calculated scanner-, technologist-, protocol-, and indication-specific repeat rates, estimating positive predictive values and sensitivity.

Main Results:

• An estimated 1.1-1.4% of CT scans resulted in repeat imaging, contributing to excess radiation dose.
• Significant variations in repeat rates were observed between academic (1.1%) and rural (1.4%) sites.
• Bolus tracking and helical extension were major contributors to repeat scans, with rates varying significantly by site (e.g., 11.6% vs 4.3% for bolus tracking).

Conclusions:

• Automated, multi-institutional quantification of CT repeat rates is a valuable metric for assessing unnecessary radiation exposure.
• The algorithm effectively identified repeat acquisitions with high sensitivity (92%) and positive predictive values (91-99%).
• Findings highlight the need for targeted technologist training and protocol optimization to reduce repeat CT imaging and associated radiation risks.