Current pediatric administered activity guidelines for ^99m Tc-DMSA SPECT based on patient weight do not provide the...

Area of Science:

• Nuclear Medicine
• Pediatric Imaging
• Medical Physics

Background:

• Current pediatric molecular imaging administered activity (AA) guidelines rely on weight-based scaling, not rigorously evaluated for diagnostic image quality (IQ).
• Existing guidelines use adult AA scaled by patient weight with fixed minimums and maximums.
• This approach may not optimize IQ across diverse pediatric patient populations.

Purpose of the Study:

• To rigorously evaluate the efficacy of weight-based scaling in equalizing task-based IQ for pediatric patients.
• To compare weight-based scaling with patient girth as predictors of IQ in pediatric SPECT.
• To assess the impact of administered activity (AA) on diagnostic image quality (IQ) in pediatric renal SPECT.

Main Methods:

• Utilized a projection image database with an anthropomorphic model observer.
• Measured task-based IQ for renal functional defect detection across six different AA levels.
• Applied Receiver-Operating Characteristic (ROC) analysis, using the area under the curve (AUC) as the figure-of-merit; investigated patient girth as a predictor.

Main Results:

• Increasing AA demonstrated a monotonic, saturating increase in AUC, indicating defect detectability is influenced by quantum noise.
• The required AA for a given AUC increased with patient age.
• Weight-based scaling resulted in similar IQ for newborns and older children but lower IQ for 1- and 5-year-olds.
• Patient girth showed a stronger correlation with the AA needed for a constant AUC in 99mTc-DMSA renal SPECT.

Conclusions:

• Weight-based scaling is insufficient for equalizing task-based IQ in pediatric 99mTc-DMSA renal SPECT.
• Patient girth should be considered as a more effective parameter than weight for developing new pediatric dosing guidelines.
• Optimizing AA based on girth may improve diagnostic accuracy and consistency in pediatric nuclear medicine.