History

• 5-year old boy.
  
• Suffers from Moya-Moya disease.
  
• One year after a right sided EC-IC bypass the patient is referred for a H215O PET scan to examine the brain perfusion reserve 13 minutes after acetazolamide (Diamox®) challenge.

Acquisition protocol

• For both scans 400 MBq H215O water was applied as a bolus injection, and the uptake dynamically acquired in 3D mode (18x10sec).
  
• Arterial blood was continuously drawn from the radial artery and the activity counted.
  
• The baseline and the Diamox scan were acquired within 20 minutes.

Analysis

• The dispersion of the input curves were estimated and deconvolved. Then, absolute perfusion maps were calculated with the PMOD pixel-wise podeling tool (PXMOD) using the the time-weighted integral method developed by Alpert et al., as illustrated below.

PXMOD tool illustrating Alpert's rCBF quantification method. Dynamic PET images top, rCBF map bottom. Click on the image for viewing with better resolution.

• The perfusion reserve was calculated by subtracting the baseline rCBF from the rCBF under Diamox challenge.

PFUS tool illustrating perfusion reserve calculation. Diamox rCBF top, baseline rCBF middle, reserve bottom. Click on the image for viewing with better resolution.

Findings

During baseline acquisition a normal brain perfusion of 0.5[ml/ml Tissue/min] was measured in the left hemisphere. A restricted perfusion was detected in the right parietal and frontal cortex.

After Diamox challenge a normal perfusion increase was found in the supply area of the left middle cerebral artery, in the occipital cortex and the cerebellum. In the left frontal cortex the increase was reduced. Furthermore, a steal phenomenon - ie. a perfusion reduction instead of an increase - was visible in the supply area of the right anterior and middle cerebral artery as well as in the left frontal cortex.

Diagnosis

In addition to the known perfusion reduction in the left hemisphere an insufficient perfusion reserve was diagnosed in the left frontal cortex. As a consequence, the patient was operated and a left EC-IC bypass introduced.