Quality control of instant kit 99mTc-mercapto acetyl triglycine with inter- and intra-operator measurements.

This prospective study was aimed to assess inter- and intra-operator variability during routine quality control (QC) procedure for technetium-99m mercaptoacetyl triglycine ((99m)Tc-MAG3) instant kit formulation. A total of 160 QC analyses with thin layer chromatography (TLC) for 20 separate MAG3 re-constitutions were performed by 2 radiochemists. The percentage of free and hydrolysed (99m)Tc as well as binding efficiency, were calculated according to standard TLC. Each QC analysis was done using silica gel (SG), silica acrylic (SA), Whatman 1 (W1) and Whatman 3 (W3) TLC strips separately at 1h, following labeling MAG3 instant kit with (99m)Tc-pertechnetate. To assess the radiochemical stability of (99m)Tc-MAG3, the same analysis was performed 4h after kit reconstitution. Visual confirmation for QC with scintigraphy was also performed. At both time points, each radio-chemist repeated all the procedure twice for each of the TLC paper types to analyze the intra-operator reliability. Crombach's Test was used for the reliability analysis. High inter-operator correlation ratios (range: 0.821-0.920) per each TLC strip were found where the highest concordance rate was 0.921 for SA. Each TLC strip showed adequate kit reconstitution with acceptable free and hydrolysed (99m)Tc percentages both at 1 and 4 h analyses, along with high binding efficiency values of 94.3 +/- 2.9 and 92.5 +/- 1.9 at 1 and 4 h respectively. Intra-observers reliability showed almost equal high concordance rates (range: 0.888-0.961) for all types of strips. In conclusion, all kinds of ITLC/TLC strips were reliable to assess stability of the radiopharmaceutical at 1 and 4 h while analysis with the SA strip had the highest concordence rate. Inter- and intra-operator QC was also reliable.

Simplified method for determining the radiochemical purity of 99mTc-MAG3.

UNLABELLED: 99mTc-Mercaptoacetyltriglycine is used for dynamic renal imaging, and the summary of product characteristics (SPC) for the European formulation specifies a shelf life of 1 or 4 h, depending on the reconstitution volume of the kit. To minimize the time required to test the radiochemical purity, a simplified quality control method was developed. METHODS: To satisfy the recommendations of the International Commission on Harmonisation, results obtained with the methods described in the European and American SPCs were compared with those obtained with the simplified method. Further validation of the new method was performed by comparison with the standard 2-strip thin-layer chromatographic method as well as tests for linearity and limits of detection and quantification. RESULTS: The simplified method provided results comparable to those provided by the registered SPC methods but was more rapid to perform and used smaller volumes of solvents. CONCLUSION: The simplified method is a reasonable alternative to the registered SPC methods.

Preparation of 99mTc-MAG3: radiochemical purity is affected by the residence time of sodium chloride injection in a three-part syringe.

BACKGROUND: Routine technetium-99m mercaptoacetyltriglycine (99mTc-MAG3) radiochemical purity measurements have revealed occasional unacceptably low values. Preliminary investigations suggested a causal link with the residence time of sodium chloride injection in the syringe used to reconstitute the MAG3 kit. OBJECTIVES: To investigate the cause of this phenomenon, determine how it can be avoided and establish whether it occurs with other 99mTc radiopharmaceuticals. METHODS: 99mTc-MAG3 was prepared by drawing sodium chloride injection into a lubricated, three-part, 10 ml Plastipak syringe and using it to reconstitute a MAG3 kit immediately or after a 15 min incubation period. The radiochemical purity was measured by high-performance liquid chromatography. The experiment was repeated using lubricant-free, two-part, Norm-Ject syringes and lubricated, two-part, Monoject syringes (15 min incubation only). To investigate the influence of Plastipak's rubber components on the radiochemical purity, samples were prepared using sodium chloride injection that had been incubated with lubricated or lubricant-free rubber plunger ends. Similar experiments were performed to determine the effect of Plastipak on 99mTc-exametazime, 99mTc-sestamibi and 99mTc-tetrofosmin. RESULTS: The radiochemical purities of 99mTc-MAG3 prepared with sodium chloride injection incubated for 0 and 15 min in Plastipak syringes were 96.4+/-0.5% and 89.4+/-5.5%, respectively. The difference was significant (P<0.05, n=10). With Norm-Ject syringes, the radiochemical purities were 96.5+/-0.5% and 96.6+/-0.5%, respectively. The difference was not significant (P>0.05, n=10). With Monoject syringes, the radiochemical purity was 96.6+/-0.4% (n=10). 99mTc-MAG3 prepared using sodium chloride injection treated with lubricated and unlubricated syringe rubber plunger ends had radiochemical purities of 85.3+/-6.6% and 82.1+/-6.5% (n=5), respectively. The radiochemical purities of other 99mTc radiopharmaceuticals prepared using sodium chloride injection incubated for 0 or 15 min in Plastipak syringes were as follows: 99mTc-exametazime, 95.3+/-0.6% and 94.5+/-1.8%; 99mTc-sestamibi, 98.0+/-0.6% and 97.7+/-0.6%; 99mTc-tetrofosmin, 96.5+/-0.2% and 97.0+/-0.4%. None of the differences was significant (P>0.05, n=5). CONCLUSIONS: A lipophilic impurity, originating from the rubber plunger of a three-part Plastipak syringe, is formed in 99mTc-MAG3 when the sodium chloride injection used to reconstitute the kit is in the syringe for a prolonged time. The effect is eliminated by using a two-part syringe or by injecting the sodium chloride injection into the kit immediately. The phenomenon does not occur with 99mTc-exametazime, 99mTc-sestamibi or 99mTc-tetrofosmin.

Effect of solvent flow rate in mini-column testing of 99mTc-mertiatide.

OBJECTIVE: The recommended method for radiochemical purity testing of 99mTc-mertiatide involves the use of a C-18 solid-phase mini-column cartridge. The mertiatide package insert states that the solvents should be "pushed through the cartridge slowly," but a flow rate is not specified. The mini-column cartridge instruction sheet recommends flow rates of 5-10 and 2-10 mL/min for conditioning and for elution, respectively, of the cartridge. The purpose of this study was to evaluate the effect of different flow rates on determining the radiochemical purity of 99mTc-mertiatide. METHODS: Radiochemical purity was tested on 10 consecutive vials of 99mTc-mertiatide prepared for routine clinical use and on 4 vials of 99mTc-mertiatide spiked with 6%-15% free pertechnetate using 3 different flow rates: slow drip (5 mL/min for conditioning and 2 mL/min for elution), fast drip (10 mL/min for conditioning and 10 mL/min for elution), and very fast drip (about 15-20 mL/min for conditioning and about 15-20 mL/min for elution). An infusion pump was used to provide constant flow rates for the first 2 conditions, whereas manual handling, reflecting real-life practice, was used for the third condition. RESULTS: All 3 flow rates yielded essentially identical radiochemical purities for each vial tested (agreement was always within 0.3% for a given vial). The elapsed times for mini-column conditioning, loading, and elution were approximately 15, 5, and 3 min for the slow drip, fast drip, and very fast drip, respectively. CONCLUSION: Faster flow rates for mini-column testing of 99mTc-mertiatide save time (and correspondingly reduce radiation exposure to the worker) without adversely affecting the results of radiochemical purity determinations.

Preparation, radiochemical purity control and stability of 99mTc-mertiatide (Mag-3).

BACKGROUND: Scintigraphic image analysis of 99mTc-mertiatide (Mag-3, mercaptoacetyltriglycine) clearance provides the determination of the blood flow, the tubular transit time and the excretion as well from both kidneys. Radiopharmaceutical routine recommends a radiochemical purity control before administration of the product to a patient. The main objective of this study is to develop a Mag-3 labeling procedure that fits better than the previous one in our daily routine production of radiopharmaceuticals. METHODS: Increasing proportions of 99mTc-Mag-3 were measured during the heating and cooling steps of the Mag-3 labeling procedure. HPLC analysis was used to confirm the results of a rapid radiochemical quality control assay on standard ITLC-SG paper. RESULTS: The reconstitution time takes 20-25 minutes from the harvest of pertechnetate to a ready-for-use calibrated patient syringe. The HPLC profile of 99mTc-Mag-3 including its minor impurities remains unchanged for 24-48 hours after reconstitution. CONCLUSIONS: The application of a programmable Peltier-directed device for heating/cooling provides a better control of the temperature course. The procedure proposed fully meets the labeling criteria recommended by the supplier and can be performed with a minimum of attention within a time-span that we formerly needed for solely the radiochemical purity control assay. Moreover, 99mTc-Mag-3 prepared in this way seems to be considerably more stable than mentioned in the manufacturer's instructions.

Identity confirmation of 99mTc-MAG3, 99mTc-sestamibi and 99mTc-ECD using radio-LC-MS.

Due to the low concentrations in which 99mTc-radiopharmaceuticals are obtained (4-40 ng/ml), confirmation of the identity of these tracer agents in the European Pharmacopoeia is generally performed only indirectly by assessment of their retention times on RP-HPLC. We have investigated whether it is possible to obtain more direct proof of the identity of technetium-99m labelled radiopharmaceuticals using radio-LC-MS. As representative examples, negatively charged 99mTc-MAG3, positively charged 99mTc-Sestamibi and neutral 99mTc-ECD were used. The three technetium-99m radiopharmaceuticals were prepared in several conditions to obtain variable relative amounts of radiochemical impurities and variable concentrations of the complexes (pico- to nanomolar). The preparations were analyzed on a reversed phase C18 HPLC column using a radio-LC-MS system equipped with a time of flight mass spectrometer with electrospray ionization in positive (99mTc-Sestamibi, 99mTc-ECD) or negative (99mTc-MAG3, 99mTc-ECD) mode. For each of the studied complexes, the main peak in the radiometric channel coincided with the expected molecular ion mass of the corresponding technetium complex in the mass spectrometer channel. The relative error on the measured accurate mass was in the range of 10 ppm. The identity of several radiochemical impurities of the three technetium complexes was also confirmed or established. It is concluded that radio-LC-MS can be a sensitive aid in quality control of 'no carrier added' radiopharmaceuticals.