Girth-based administered activity for pediatric ^99m Tc-DMSA SPECT.

Area of Science:

• Nuclear Medicine
• Pediatric Imaging
• Radiation Dosimetry

Background:

• Pediatric molecular imaging balances image quality (IQ) with radiation exposure.
• Current North American Consensus Guidelines use patient weight for administered activity (AA) recommendations.
• Optimizing AA is crucial for diagnostic efficacy and patient safety.

Purpose of the Study:

• To develop a girth-based dosing guideline for pediatric Tc-99m DMSA renal function imaging.
• To systematically generate curves showing the tradeoff between AA and IQ as a function of patient girth.
• To provide data for standards bodies to create next-generation pediatric DMSA SPECT dosing guidelines.

Main Methods:

• Utilized an anthropomorphic phantom series with variations in age, gender, girth, and kidney size.
• Simulated realistic SPECT projections with a fixed renal cortex defect.
• Employed task-based IQ assessment using Receiver Operating Characteristic (ROC) analysis and Area Under the Curve (AUC) to measure defect detectability.

Main Results:

• Girth-based dosing differed from weight-based dosing, particularly for patients with disproportionate weight-to-girth ratios.
• Potential AA reductions up to 62.9% were observed while maintaining baseline IQ (AUC=0.80) in specific pediatric cases.
• Task-based IQ results were sensitive to simulated defect size, requiring physician input for AUC interpretation.

Conclusions:

• Simulation data supports a girth-based dosing method for pediatric renal SPECT.
• Patient waist circumference at the kidney level should be considered for optimizing AA and IQ.
• This data can inform the development of new girth-based dosing guidelines for pediatric DMSA SPECT.