How soon after the administration of 99mTc-exametazime can SPECT brain imaging begin?

SPECT brain imaging using 99mTc-exametazime, which is also known as 99mTc-HMPAO (hexamethylpropyleneamine oxime), is typically conducted 15 to 20 minutes after the administration of the radiopharmaceutical. This timing allows sufficient uptake of the tracer in the brain tissues to achieve optimal imaging quality.

The pharmacokinetics of 99mTc-exametazime reveal that it quickly crosses the blood-brain barrier and is retained in the brain, providing valuable information about cerebral perfusion. Immediate imaging would not provide accurate results because the radiotracer needs time to localize properly within the brain tissue.

Delaying imaging beyond 20 minutes could lead to a decrease in radiotracer retention in the brain, thus compromising the diagnostic quality of the images obtained. Hence, the best practice is to start SPECT imaging within the 15-20 minute timeframe after tracer administration for accurate assessments.