A population of pediatric phantoms to investigate the tradeoff between radiation dose and image quality

Objectives Pediatric nuclear medicine dosing guidelines are often based on patient weight, but our previous studies have shown that patient body shape plays a major role in both patient dose and image quality. The goal of this project was to further explore these relationships.

Methods A set of 120 phantoms were modeled at the 10th, 50th, and 90th height percentiles and 50th weight percentile for ages ranging from 0 to 15 years. Kidneys were modeled with the following variations in volume: average size, +15%, -15%, and -30%. The phantoms were digitized to 1 mm voxels for use in image simulations. Attenuation maps for 140 keV were generated based on ICRP organ compositions and densities. Analytic simulations of the projection data of structures of interest for Tc-99m imaging agents were created using an analytic projection code that models attenuation, the collimator-detector response, and patient scatter. Our initial investigations are for Tc-99m DMSA renal SPECT, and so projections were generated for the renal pelvis, medulla, and cortex and the liver, spleen and body remainder. Defects modeling focal kidney function deficits of varying sizes have been created.

Results We have created a pediatric patient population and corresponding projection datasets that allow studying the tradeoff between dose and image quality in pediatric imaging of Tc-99m tracers. We have used these data in an initial study of the effect of body habitus in Tc-99m DMSA SPECT using task-based image quality measures. We found that image quality and dose were both affected by body habitus and not just patient weight.

Conclusions The phantoms and projection data in this work can be used to provide data to refine dosing guidelines for pediatric nuclear while taking into account the affects on both radiation dose and image quality.

Research Support NIH R01 EB013558