Findings: Following the intravenous administration of 28.9 mCi of technetium 99m Ceretec delayed images over the brain were performed. Coronal and sagittal reconstruction images were then performed. Submitted images demonstrate an area of decreased perfusion involving the left MCA territory. Specifically, this involves a portion of the left frontal, temporal and parietal lobes.

Diagnosis: Decreased perfusion within the left MCA territory.

Discussion: Ceretec also known as HMPAO is a lipophilic agent which crosses the blood-brain barrier. Once within the brain, it becomes hydrophilic and is therefore trapped within brain tissue.

The activity reflects cerebral blood flow with most activity seen within gray matter. Uptake is highest within the cerebellum. White matter is not well visualized because of relatively lower regional blood flow. In addition, uptake is usually heterogeneous reflecting the normal gyriform and sulcal pattern of the brain.

Cerebrovascular reserve can be assessed with the use of acetazolamide. Cerebral blood flow normally increases with this medication secondary to an increased levels of carbon dioxide level. However, regions of poorer perfusion will demonstrate a relative deficit because of decreased vasodilatation.

References:
Mettler, FA, Guiberteau MJ. Essentials of Nuclear Medicine Imaging, 4th Edition.
W.B. Saunders, Philadelphia. 1998:84-85.

Thrall JH, Ziessman HA. Nuclear Medicine, the Requisites.
Mosby, St. Louis, 1995:268-270.

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