Optimizing Coronary CT Angiography: Impact of Tailored Protocols on Radiation Dose, Image Quality, and Patient Eligibility
Abstract
Purpose
To create user-friendly, size and heart condition-specific protocols to improve coronary CT angiography (CCTA) image quality, reduce dose, and expand eligibility to patients with contraindications due to heart activity.
Methods
Two CCTA protocols were created to replace multiple size and heart-rate dependent protocols on a wide-beam scanner: one for BMI ≥25 and one for BMI <25. New guidelines were established to specify contrast volume and injection rate based on BMI to improve bolus quality. Within each protocol, 28 different profiles were customized based on seven heart rate (HR) categories (from 30-200 beats/minute) and HR rhythm (stable, variable, irregular, and highly irregular). Before intervention, the whole heartbeat was often imaged to accommodate rapid/fluctuating heart rates due to high volume of inpatient and emergency patients. Custom phase gated windows with full mA and 20% reduced mA outside were defined for specific HR/rhythm combinations to reduce radiation by iteratively analyzing images and gathering feedback from technologists. Additionally, deep learning algorithms were utilized to further improve vessel detectability. One-on-one training was conducted to educate technologists on the new protocols. CTDIvol was retrospectively tracked monthly.
Results
In the first month after implementation of the new protocols, CTDIvol decreased by 30%. Bolus quality improved, especially in high BMI patients. Patients with rapid HR or contraindications to beta blockers that previously were cancelled or delayed were successfully imaged. By embedding the HR/rhythm profiles within the protocol, fewer protocol decisions were required by technologists. In combination with one-on-one training, technologists expressed increased comfortability with cardiac imaging on the multi-modality scanner.
Conclusion
The use of tailored phase windows and BMI-based contrast administration improved image quality and lowered radiation doses, particularly for patients with irregular rhythms or high BMI. Replacing multiple rigid protocols with two dynamic protocols allowed imaging of challenging patients and increased comfortability among technologists.