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Stabilization of [99mTc]HMPAO--1. Ethanolic preparation
M W Billinghurst1, D N Abrams, M S Lawson
1Health Sciences Centre, Winnipeg, Manitoba, Canada.
International Journal of Radiation Applications and Instrumentation. Part A, Applied Radiation and Isotopes
|January 1, 1991
Summary
Preparing technetium-99m hexamethylpropyleneamine oxime ([99mTc]HMPAO) in ethanol enhances its stability for brain imaging. This improvement extends its usability beyond the previous 30-minute window.
Area of Science:
- Nuclear Medicine
- Radiopharmaceutical Chemistry
Background:
- Cerebral blood flow imaging relies on radiopharmaceuticals like technetium-99m hexamethylpropyleneamine oxime ([99mTc]HMPAO).
- The short in vitro stability of [99mTc]HMPAO limits its clinical application time.
Purpose of the Study:
- To investigate the effect of ethanol-based preparation on the in vitro stability and biological distribution of [99mTc]HMPAO.
- To determine if enhanced stability can extend the useful time of [99mTc]HMPAO for brain imaging.
Main Methods:
- Comparison of in vitro radiochemical purity of [99mTc]HMPAO prepared in 85% ethanol versus aqueous solution.
- Biological distribution studies in mice to assess brain uptake and brain:blood ratios for both formulations.
Main Results:
- [99mTc]HMPAO in 85% ethanol showed improved in vitro stability (92% purity at 90 min) compared to aqueous preparation (79% at 90 min).
- Similar brain uptake and brain:blood ratios were observed for ethanolic and aqueous formulations at relevant time points.
- The ethanolic formulation maintained stability for 2 hours, while the aqueous formulation's utility was limited to 15 minutes.
Conclusions:
- Preparation of [99mTc]HMPAO in 85% ethanol significantly enhances its in vitro stability.
- This enhanced stability allows for a longer useful time for [99mTc]HMPAO, potentially expanding its use in cerebral blood flow imaging.