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Society for Pediatric Radiology – Poster Archive
Final ID: Poster #: SCI-001
Pediatric Dose Evaluation of 4D Dynamic CT Protocol
Purpose or Case Report: Balancing PEEP settings in mechanically ventilated premature infants to maximize air exchange while minimizing barotrauma is typically evaluated using bronchography. A 4D dynamic airway computerized tomography protocol (4D CT) was developed as a less invasive method to evaluate large and small airways collapse at variable PEEP settings. Our purpose was to evaluate the radiation dose from 4D CT and to demonstrate the number of cycles impact on the radiation dose.
Methods & Materials: 39 pediatric patients <5 years who underwent imaging as part of routine clinical care between 1/1/16-10/1/18. Dynamic sequential CT scan was performed on Siemens Flash, fixed 70 kVp, fixed 10 mAs. One 4D CT imaging cycle was defined as the time required for one full inspiratory-expiratory cycle at a given PEEP, which ranged between 2-8 seconds. Each cycle contained 7 rotations. The body and skin effective radiation doses were estimated using two methods: (1) the body effective dose is calculated using Monte Carlo simulations of a library of male and female anthropomorphic size and age-specific phantoms. (2) NanoDots optically stimulated luminescent dosimeters were used to measure the peak skin dose (PSD) by placing them on the chest of a newborn phantom for a different number of cycles.
Results: Increasing the number of cycle/rotations increased the PSD, dose length product (DLP), effective dose, and the lung organ dose. The estimated effective dose varied depending on the patient’s DLP value, patient’s gender, and age weighting factors. The average effective dose was higher for female patients. From the simulation’s results, the highest organ dose was received by the lungs. The average value for lung dose was 0.9 mSv.
Conclusions: Irradiation over the same anatomic region by 4D CT results in accumulation of radiation dose and raising the concern for the potential deterministic effect of skin injury. The maximum measured entrance skin exposure by the 4D CT was orders of magnitude lower than the threshold dose for early transient erythema (2000 mGy). As the PSD increased by increasing the number of rotations, reducing the number of imaging cycles may reduce the overall patient radiation exposure. A differential effective dose in female patients is due to higher end-organ risk from radiation scatter. Extra caution to limit cycles should be exercised when using 4D CT technique in children under 1 year. In addition, DLP would be a better dose metric than CTDI because of DLP metric account for the total irradiated area.
Methods & Materials: 39 pediatric patients <5 years who underwent imaging as part of routine clinical care between 1/1/16-10/1/18. Dynamic sequential CT scan was performed on Siemens Flash, fixed 70 kVp, fixed 10 mAs. One 4D CT imaging cycle was defined as the time required for one full inspiratory-expiratory cycle at a given PEEP, which ranged between 2-8 seconds. Each cycle contained 7 rotations. The body and skin effective radiation doses were estimated using two methods: (1) the body effective dose is calculated using Monte Carlo simulations of a library of male and female anthropomorphic size and age-specific phantoms. (2) NanoDots optically stimulated luminescent dosimeters were used to measure the peak skin dose (PSD) by placing them on the chest of a newborn phantom for a different number of cycles.
Results: Increasing the number of cycle/rotations increased the PSD, dose length product (DLP), effective dose, and the lung organ dose. The estimated effective dose varied depending on the patient’s DLP value, patient’s gender, and age weighting factors. The average effective dose was higher for female patients. From the simulation’s results, the highest organ dose was received by the lungs. The average value for lung dose was 0.9 mSv.
Conclusions: Irradiation over the same anatomic region by 4D CT results in accumulation of radiation dose and raising the concern for the potential deterministic effect of skin injury. The maximum measured entrance skin exposure by the 4D CT was orders of magnitude lower than the threshold dose for early transient erythema (2000 mGy). As the PSD increased by increasing the number of rotations, reducing the number of imaging cycles may reduce the overall patient radiation exposure. A differential effective dose in female patients is due to higher end-organ risk from radiation scatter. Extra caution to limit cycles should be exercised when using 4D CT technique in children under 1 year. In addition, DLP would be a better dose metric than CTDI because of DLP metric account for the total irradiated area.
More abstracts on this topic:
Dynamic Imaging for Optimized Orthodontic Airway Plates in Robin Sequence
Ho Michelle, Mercan Ezgi, Evans Kelly, Sheller Barbara, Otjen Jeffrey, Friedman Seth
Estimation of Peak Skin Dose with Dose Structure Reports in a Radiation Data Management SystemZhu Xiaowei, Whitaker Jayme, Shellikeri Sphoorti, Cahill Anne Marie
Poster____SCI-001.pdf
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