DOSE OPTIMIZATION OF NUCLEAR MEDICINE PROCEDURES IN PAEDIATRIC PATIENTS: BIOKINETIC MODEL ANALYSIS AND DOSE COEFFICIENT ANALYSIS
This study analysed the biokinetic behaviour of the radiopharmaceutical 99mTc-dimercaptosuccinic acid (DMSA), after administration in 8 infants aged 4 months to 2 years, through an imaging study in a nuclear medicine facility using a Gamma camera, and compared the obtained values with those obtained with the reference ICRP biokinetic model. The in vivo data was treated using an adapted methodology from the MIRD 16 pamphlet. The obtained results allowed for an absorbed dose estimation which is smaller than that provided by ICRP by 32.1% in the kidneys, and 18.4% in the liver.
Dose assessment was performed using the MCNPX 2.7 code and the GsF voxel phantoms BABY and CHILD. The two phantoms were scaled according to two different methodologies - using a kidney mass function relative to age; and using body mass and height. The obtained Dose Coefficients reveal that the ‘step’ function with age as used by ICRP could be too simplistic. When using the 2nd methodology, which takes into account body weight and height, results can be fitted to a 1/m function in which m is the body mass. This function could be adapted to provide optimized values for dose in paediatric patients, especially for those aged 0-5 years old.