Room: AAPM ePoster Library
The stray radiation data from CT vendor for shielding design is measured using a 32cm CTDI phantom and 140kVp, which doesn’t reflect average patient of a pediatric hospital. The stray radiation data must be scaled to better reflect an average pediatric patient for shielding design.
Stray radiation data were collected using different sizes of CTDI phantoms (10cm, 16cm, and 32cm) with variable tube voltages (80kVp, 100kVp, 120kVp, and 140kVp) at different distances (1m and 2m). The kVp and phantom size for an average pediatric patient uses 120kVp with 16cm phantom for head, and with 24.1cm for body (13-year-old from AAPM Report-204). kVp and phantom factors are generated to scale the vendor stray radiation data. kVp factor is the ratio of stray radiation at 140kVp compared to other kVp. Phantom factor is the ratio of stray radiation 32cm phantom creates compared to other size of phantoms. For a fixed phantom size, the polynomial fit was used for the stray radiation versus kVp. With this fit, kVp factor is generated for 10kVp increments for different phantom sizes. Additionally, the kVp factor uses a polynomial fit for a specific kVp, so kVp factor can be estimated for a fixed patient size. Phantom factor was generated using the measured exposure data, and was fit using polynomial for each phantom size for different kVp. For each kVp, the phantom factor is linearly fit, so various phantom sizes can be used.
The estimated kVp and phantom factors were combined to modify the stray radiation data. Using the combined factors, vendor data can be scaled for any kVp or phantom size.
kVp and phantom factors were generated and applied to the vendor stray radiation data to reflect the pediatric patient parameters. Using the modified data, shielding design can better fit a pediatric hospital.