Estimating the Absorbed Dose of Organs in Pediatric Imaging of 99mTc-DTPA Radiopharmaceutical using MIRDOSE Software

Introduction: In this study, organ radiation doses were calculated for the renal agent 99mTc-DTPA in children. Bio-kinetic energy of 99mTc-DTPA was evaluated by scintigraphy and estimates for absorbed radiation dose were provided using standard medical internal radiation dosimetry (MIRD) techniques.Materials and Methods: In this applied research, fourteen children patients (6 males and 8 females) were imaged using a series of planar and SPECT images after injecting with technetium-99m diethylenetriaminepentaacetic acid (99mTc-DTPA). A hybrid planar/SPECT method was used to plot time-activity curves to obtain the residence time of the source organs and also MIRDOSE software was used to calculate the absorbed dose of every organ. P-values were calculated using t-tests in order to make a comparison between the adsorbed doses of male and female groups.Results: Mean absorbed doses (µGy/MBq) for urinary bladder wall, kidneys, gonads, liver and adrenals were 213.5±47.8, 12.97±6.23, 12.0±2.5, 4.29±1.47, and 3.31±0.96, respectively. Furthermore, the mean effective dose was 17.5±3.7 µSv/MBq. There was not any significant difference in the mean absorbed dose of the two groups.Conclusion: Bladder cumulated activity was the most contribution in the effective dose of patients scanned with 99mTc-DTPA. Using a hybrid planar/SPECT method can cause an increase in accumulated activity accuracy for the region of interest. Moreover, patient-specified internal dosimetry is recommended.

Preparation and Crystal Structure of a Rhenium Analogue of the Cationic Renal Agent, Tc-99m Diaminocyclohexane

We report here a chemical study on a Re analogue of one of the few cationic Tc-99m tracers previously investigated as an agent for effective renal plasma flow (ERPF) measurement. Cationic Tc-99m tracers have the potential for overcoming problems associated with common anionic Tc-99m tracers in patients who have developed a uremic state. The Tc-99m-DACH tracer, prepared from 1,2-diaminocyclohexane (1,2-DACH), is the only cationic renal agent tested in humans and has seven possible isomers. The complex isolated from the reaction of the racemic mixture, (±)-trans-1,2-DACH, and ReIO2(PPh3)2 after conversion to the BPh4- salt was found by X-ray crystallography to be the meso isomer, trans-[ReO2 (trans-R,R-1,2-DACH)(trans-S,S-l,2-DACH)][BPh4]·MeOH·2H2O (1). The structural parameters for 1 are normal. The complex is highly symmetrical, suggesting that the analogous meso Tc-99m-DACH agent is also symmetrical. Studies of other Tc-99m-DACH agents that were made from cis-1,2-DACH or individual trans-1,2-DACH enantiomers show that the biodistribution is not very dependent on the starting 1,2-DACH ligand stereochemistry; these agents must be less symmetrical than the meso Tc-99m-DACH agent analogue of 1. Thus, the overall charge and lipophilicity (similar for all Tc-99m-DACH isomers) exert a greater influence on biodistribution than the specific structural features of the different Tc-99m-DACH isomers.