It has been widely reported that 99m Tc-succimer adsorbs to plastic syringes significantly (up to 50%), often resulting in a lower administered dose than intended or inaccurate dosing. This adsorption rate is especially problematic in the pediatric population. To improve 99m Tc-succimer dosing, we compared the adsorption of 99m Tc-succimer with 2 types of syringes: silicone-coated syringes with nonlatex rubber on the plunger and inert nonreactive syringes with no silicone coating and no rubber on the plunger. Methods: 99m Tc-succimer kits were compounded according to the manufacturer's instructions. 99m Tc-succimer doses (37-185 MBq) were drawn into 3-mL (silicone-coated or inert nonreactive) syringes in a 1-mL volume. Thirty min, 1 h, 2 h, and 4 h later, the syringes were assayed in a dose calibrator and assayed again after being emptied and rinsed with saline. In addition, we examined the data collected from 129 99m Tc-succimer doses administered in a pediatric department, in which 52 were dispensed in siliconecoated syringes and 77 were dispensed in inert nonreactive syringes. The doses were assayed immediately before and after injection. The syringes were flushed with normal saline. Results: The labeling efficiency of the 99m Tc-succimer kits was more than 95%. Residual activity left in the inert nonreactive syringes was 0.73% (SD, ±0.18%), which was significantly lower than the activity left in the silicone-coated syringes, 20.9% (SD, ±5.6%; P , 0.0001). The extent of adsorption did not change significantly between 30 min and 4 h of incubation. The clinical data showed that the residual activity was 30.6% (SD, ±12.5%) from doses dispensed in silicone-coated syringes and 6.38% (SD, ±2.95%) from doses dispensed in inert nonreactive syringes (P , 0.001). Conclusion: The inert nonreactive syringes had significantly less residual of 99m Tc-succimer than silicone-based syringes, making it possible to accurately administer calculated doses of 99m Tc-succimer to pediatric patients. The adsorption or adhesion of radiopharmaceuticals to administration sets and syringes has been well documented (Table 1) (1-8). In a previous study, we found that 99m Tc-succimer adsorbed to plastic syringes up to 82%, often resulting in a lower administered dose than intended or inaccurate dosing (9). This rate of adsorption is especially problematic with low doses used with the pediatric population, which led us to investigate syringes with clinically acceptable levels of adsorption. MATERIALS AND METHODS99m Tc-succimer kits were compounded according to the manufacturer's instructions. 99m Tc-succimer doses (37-185 MBq) were drawn into 3-mL type A, silicone-coated (BD 3 mL, 309572, B-D) and type B, inert nonreactive ( Fig. 1) (HSW 3 mL, 4020-X00V0 2 mL [3 mL]) NORM-JECT (Henke Sass Wolf) syringes with a volume of 1 mL. Both syringe types are composed of a blend of laboratory-grade polyethylene and polypropylene in sterile individually wrapped packaging. Thirty min, 1 h, 2 h, and 4 h later, the syringes were assayed in a dose calibrat...
Balancing image quality with radiation dose is a goal with every diagnostic procedure requiring radiation. Our institution compared the dosing of 99m Tc-labeled succimer, commonly referred to as dimercaptosuccinic acid ( 99m Tc-DMSA), to pediatric patients using 2 methods of calculation, body surface area (BSA, the method we used from 2009 to 2010) and body weight (BW, the method we used in 2011). Methods: A retrospective study was conducted in a 230-bed inpatient, tertiarycare academic pediatric hospital to obtain objective data on patients under the age of 17 y who received a renal nuclear medicine procedure with 99m Tc-DMSA using a 300,000-count parallel image and four 150,000-count pinhole images. Data collection included patient age, sex, height, weight, calculated activity, assayed activity, administered activity, residual syringe activity, imaging time, and notable patient or equipment factors affecting the procedure. Results: Calculated activities based on BSA were higher than calculated activities based on BW. 99m Tc-DMSA adsorption to the plastic syringes was significant, with a range of 3%-82%. Because of the adsorption, an average of 23.7 MBq (SD, 631 MBq) was added to the patients' calculated dose when the order was placed. Therefore, assayed activities were significantly higher than calculated activities in both groups. Administered activity correlations to BSA and BW calculations were 0.75 and 0.83, respectively. Administered activities from BSA and BW groups were outside the American College of Radiology (ACR)-recommended guidelines 59% and 45% of the time, respectively. Overall, children less than 2 y old were above the ACR recommendations 80% of the time. There was a poor correlation between administered activity and total imaging time (r 5 0.23). Average imaging time overall for 5 planar views was 14.8 min (67.1 min). Patients receiving less than the ACR-recommended administered activities (,1.85 MBq/kg) had an average increase in imaging time of 4.5 min (63.4 min). Conclusion: The activity administered to patients was significantly affected by the amount of 99m Tc-DMSA activity adsorbed to the syringe. Syringe residual should be considered when standardizing 99m Tc-DMSA imaging protocols and calculating patient dose. Although 99m Tc-DMSA adsorption was variable, the administered activities correlated with calculated activities. In all but one of our patients, the total imaging time was far less than recommended by the ACR and European Association of Nuclear Medicine guidelines. The study indicates that using the BW calculation of 3.7 MBq/kg resulted in a range of administered activity of 1.85-2.59 MBq/kg. 99m Tc-DMSA dosing of 3.7 MBq/kg for pinhole imaging should be appropriate for most studies.
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