RESUMO
Determining the radiochemical purity of 99Tcm-HMPAO using the standard method suggested by the manufacturer of the HMPAO kit is slow, consuming much of the 30 min useful shelf-life of the radiopharmaceutical. We have compared two new methods (a solvent extraction technique and a method involving a disposable, pre-packed reverse phase chromatography cartridge) with the standard method for determining the radiochemical purity of 99Tcm-HMPAO. There were no significant differences (F test, p less than 0.05) in the results obtained by all three methods. However, the reversed phase chromatography method gave better agreement (correlation coefficient of 0.877) with results obtained using the standard method than did the solvent extraction technique (correlation coefficient of 0.693). The solvent extraction technique took about 10 min to perform whereas the reversed phase chromatography method took only 5 min. Both of the new methods did not achieve complete separation of the secondary, less lipophilic 99Tcm-HMPAO complex from the primary, lipophilic 99Tcm-HMPAO complex but the error introduced was small (typically only 3-5%). The new methods offer the capability of determining the radiochemical purity of 99Tcm-HMPAO quickly, reliably and accurately, prior to administration of the radiopharmaceutical to the patient.
Assuntos
Compostos de Organotecnécio/normas , Oximas/normas , Compostos de Organotecnécio/análise , Oximas/análise , Radioquímica , Kit de Reagentes para Diagnóstico , Tecnécio Tc 99m ExametazimaRESUMO
The standard radiochemical purity (RCP) determination uses a three-paper chromatography strip and solvent system (TP). The involvement of multiple strips for calculation of percentage primary, lipophilic 99Tcm-exametazime complex is tedious and time-consuming. The significant streaking of radioactivity on the ITLC/SG MEK strip of the TP method indicates that ITLC/SG MEK may not be an ideal system for RCP analysis of 99Tcm-exametazime. This study was undertaken to compare the standard TP method with two other proposed single-strip chromatography systems: Whatman 17 Chr paper with ethyl acetate (WE) and Gelman Solvent Saturation Pads paper with ether (GE). Our results showed that the solvent developing times (n = 55) and Rf values for TP, WE and GE were 130.4 +/- 9.0 s/0.5-1.0, 205.9 +/- 13.0 s/0.2-1.0 and 90.2 +/- 7.5 s/0.8-1.0, respectively. For RCP values ranging from 45.0 to 94.6% (n = 61), both WE and GE closely correlated with TP (r = 0.97 and 0.96). However, in the intermediate RCP range (i.e. 75-85%, n = 25), the false RCP acceptance rate (i.e. RCP > or = 80%) was 40% (10/25) for the WE method versus 4% (1/25) for the GE method. The GE method has the most clear separation of lipophilic 99Tcm-exametazime from other radiochemical impurities and offers the quickest RCP analysis for 99Tcm-exametazime with relatively accurate results.
Assuntos
Compostos de Organotecnécio/normas , Oximas/normas , Cromatografia em Papel/métodos , Compostos de Organotecnécio/isolamento & purificação , Oximas/isolamento & purificação , Análise de Regressão , Solventes , Tecnécio Tc 99m ExametazimaRESUMO
The radiochemical purity of hexamethylproxypropylene amine oxime (HMPAO) was determined in 16 preparations using the three-strip method. Immediately post-formulation, 90.3% +/- 4.0% (mean +/- SD) of the activity was associated with the primary lipophilic complex having an Rf of 0.45 +/- 0.11. We recorded a significantly higher content of sodium pertechnetate Tc 99m in methylethyl ketone (MEK) (21.1% +/- 8.5%) than in saline (5.0% +/- 3.7%; P less than 0.001). To clarify this finding, we ran sequential chromatograms (t = 0, 1, 2, 3 h) and found that the primary complex steadily disappeared, with a rate constant of 0.31 h-1. These results suggest that there is a decomposition of the primary complex during chromatography in MEK that might be responsible for the larger fraction of sodium pertechnetate Tc 99m in MEK. Eluate composition might influence the Rf of the lipophilic complex and the rate of its in vitro decomposition. In another experimental setting, we investigated 99mTc-HMPAO decomposition species in urine after application of a suspension of labelled leukocytes by performing sequential chromatographic analyses in 11 patients. At 1 h after application, urinary activity reflected the presence of a secondary complex (84.8% +/- 9.2%) and sodium pertechnetate Tc 99m (15.2% +/- 9.2%). The values after 3 h were markedly different (91.4% +/- 4.8% and 8.6% +/- 4.8%; P less than 0.001). Thus, urinary activity mostly consisted of a secondary complex, increasing with time.
Assuntos
Compostos de Organotecnécio/normas , Oximas/normas , Oximas/urina , Cromatografia/métodos , Humanos , Tecnécio Tc 99m ExametazimaRESUMO
The radiochemical purities of technetium Tc 99m exametazime prepared with one-hour-old or six-hour-old sodium pertechnetate Tc 99m from two manufacturers' generators were compared. Eluates from each manufacturer's generators were diluted immediately to provide two solutions of sodium pertechnetate Tc 99m. For the one-hour-old solution, eluate was diluted with 0.9% sodium chloride injection to a concentration of radioactivity of 38 mCi in 5.5 mL and used one hour later. For the six-hour-old solution, eluate was diluted to 65 mCi in 5.5 mL and used six hours later. Technetium Tc 99m exametazime was prepared by injecting 5.0 mL of one of the solutions into an exametazime kit to provide 30 mCi of technetium Tc 99m in 5.0 mL. At 2, 30, and 60 minutes after reconstitution of each kit, the radiochemical purity was measured by high-performance liquid chromatography with radiation detection. At two minutes, all the preparations retained high radiochemical purities. However, at 30 and 60 minutes, the radiochemical purities of technetium Tc 99m exametazime prepared with six-hour-old sodium pertechnetate Tc 99m were significantly lower than those of technetium Tc 99m exametazime prepared with one-hour-old sodium pertechnetate Tc 99m. Similar results were found for each manufacturer's generators. The radiochemical purity of technetium Tc 99m exametazime was affected by the age of the sodium pertechnetate Tc 99m from which it was prepared but not by the generator from which the sodium pertechnetate Tc 99m was obtained.