Tc99mECD

Tc99mECD is a radiopharmaceutical used for cerebral perfusion imaging with single-photon emission computed tomography (SPECT). It consists of a technetium-99m complex with ethyl cysteinate dimer (also called bicisate or ECD). The compound is lipophilic and crosses the blood-brain barrier; once in the brain it is retained in proportion to regional cerebral blood flow, allowing assessment of perfusion patterns.

The agent is prepared from a kit that combines technetium-99m pertechnetate with ethyl cysteinate dimer and a reducing agent, typically stannous chloride. After labeling, the radiochemical purity is generally high, and the labeled complex remains in brain tissue for several hours, enabling flexible timing of imaging.

Indications include evaluation of cerebral perfusion in suspected cerebrovascular disease, acute or prior stroke, transient ischemic attacks, dementia, epilepsy, and traumatic brain injury, as well as post-surgical perfusion assessment. The imaging protocol involves intravenous injection of Tc-99mECD, with SPECT acquisition typically performed about 15–60 minutes after injection, though protocols vary. Adult activity is commonly in the range of 20–25 millicuries (about 740–925 MBq), adjusted for weight and institutional guidelines.

Interpretation centers on relative tracer uptake; regions with reduced uptake indicate diminished perfusion. Images are frequently interpreted alongside CT or MRI for anatomical correlation and to distinguish perfusion abnormalities from structural lesions. Safety considerations include radiation exposure; the procedure is generally avoided in pregnancy, with lactation precautions as per local guidelines. Tc-99mHMPAO is a related brain-perfusion agent that may be used as an alternative, with differing pharmacokinetics.