Case 32
Courtesy of Dr.Christiane Wiefels, University of Ottawa
Presentation:
History : 69 y.o female with dementia. Images are provided in two different color scales as follows:
1. What is the radiotracer? This study is a bain perfusion scan which can be performed by either 99mTc ethyl cysteinate dimer (99mTc ECD) or 99mTc-HMPAO.
2. What are the findings: There is moderate extensive perfusion defect within bilateral superior posterior parietal regions (yellow arrow). There is mildly decreased perfusion to the left mesial temporal cortex (pink arrow). There is also mild-moderate hypo-perfusion of bilateral occipital cortices (blue arrow). The thalamus appears mildly hypo-perfused, bilaterally. The frontal lobes are relatively preserved. Images are slightly blurred because the patient was claustrophobic and was moving during imaging. However, the images were interpretable.
IMPRESSION:
The pattern of hypoperfusion is more in keeping with Lewy Body dementia. Severe Alzheimer disease cannot be completely excluded in this case, although felt to be less likely.
3.What could we do if the patient has fear or is claustrophobic? Short acting lorazepam can be given as closer as possible from the acquisition time.
4.Explain Patient Preparation for this study: The patient should be placed in a quiet, dimly lit room either seated or preferably on a stretcher, and should be instructed to remain quiet and refrain from talking. It is important that the patient is not aware that the injection is taking place (turn head prior to injection). Patients should keep eyes open. After an additional 10 minutes of rest, the patient may return to the waiting area.
5. Explain radiotracer administration and imaging technique: 555–1,110 MBq (15–30 mCi) Tc-99m ECD, is administered intravenously and tomographic imaging of the brain is performed Approximately a 45-min delay from injection to imaging gives the best image quality. Images obtained after a 20-min delay will be interpretable [1]. After a 5-10 minute wait, the ECD or HMPAO is injected slowly through the established IV access. It is important that the patient is not aware that the injection is taking place (turn head prior to injection). Patients should keep eyes open. After an additional 10 minutes of rest, the patient may return to the waiting area. After 45 min (30 min at least) imaging is started. Wait 30 -60 minutes for ECD and 30-90 min for HMPAO to improve the signal-to-noise ratio. The patient should be in a supine position with the head positioned in a secure head holder device with forehead and chin straps to ensure the patient remains still. The canto-meatal line should be at 90 degrees to the detector (1).The imaging field is the entire brain including the cerebellum.