TRANQUILTY SCORING TO OPTIMIZE PEDIATRIC IMAGING AND REDUCE RADIATION EXPOSURE ON TOTAL-BODY PET SCANNERS

Objectives: Pediatric PET imaging protocols have historically used a standard weight-based dosing. However, the increased sensitivity of total-body PET allows for the reduction of imaging times and/or the potential for further dose reduction without compromising image quality [1,2]. Optimization of pediatric protocols should consider patient cooperation to reduce the need for general anesthesia and the potential risks involved as well as dose reduction. Our aim is to develop a precision imaging protocol for pediatric populations on total-body PET scanners using a Tranquility Score to determine scan duration and pediatric dosing scale for each individual patient.Methods: To ascertain the feasibility of reducing our standard 20-minute acquisition time using pediatric dosing (4.07MBq/kg) for patients who struggle with the duration, ¹⁸F-FDG scans from eight pediatric patients (ages 5-17 years old, weight 22-84kg) were reconstructed in shortened durations as low as 2.5 minutes. Data were analyzed after patients were prospectively enrolled in an IRB-approved registry-type study (#1470016). Each reconstruction was assessed by four Board Certified Nuclear Medicine Physicians (a Likert scale was given for desired smoothness and image quality) to determine the shortest acquisition still superior to the scan quality produced by conventional PET scanners [2]to determine whether the images were of diagnostic quality. To establish which pediatric patients would benefit from a reduction in scan time verses a reduction in dosing, we developed a Tranquility Scoring System (Table 1) to assess patient cooperation. The scoring system uses a scale from 1 to 4, with 1 requiring anesthesia and 4 indicating the patient can cooperate for a full 20-minute acquisition. For pediatric patients who can tolerate our standard 20-minute acquisition, a dose reduction proportional to the acceptable scan time reduction can be applied. Each number on the tranquility scale corresponds to an assigned scan duration and dosing scale.Results: The 5-minute reconstructions on the total-body PET scanner exceeded the standard-of-care compared to image quality of conventional PET/CT scanners, indicating a scan duration as low as 5 minutes would not sacrifice image quality with standard pediatric dosing, while 2.5-minute reconstructions were deemed to be of diagnostic quality [2]. Incorporating the level of cooperation from pediatric patients, a dose reduction can be implemented as an alternative at a reverse linear rate to reduction in scan duration. For example, if a patient can tolerate a 20-minute acquisition, the dose would be reduced by 75% compared to that used for a 5-minute acquisition. Conclusion: Although our current pediatric imaging protocol may provide exceptional image quality, Oour Tranquility Scoring System evaluates a child’s capacity to cooperate, which can be used results in either aeither to reduceed scan time to avoid potential anesthesia or a to reduce dose reduction below the SNMMI standards. Unlike pediatric protocols on conventional PET scanners, the EXPLORER does not sacrifice require extended scan duration for to achieve dose reduction. Any facility with a total-body PET or other ultra-high performance scanner with similar sensitivity could implement a Tranquility Scoring System to further most appropriately reduce radiation and anesthesia risks to their pediatric population.References: [1] R. D. Badawi, et al., “First Human Imaging Studies with the EXPLORER Total-Body Scanner,” J Ncul Med, vol. 60, 2019.