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IMAGE INTERPRETATION · BRAIN IMAGING

Brain SPECT: When to Image After ECD Injection

Brain perfusion SPECT (Tc-99m ECD), transverse slices — normal study
Brain perfusion SPECT (Tc-99m ECD), transverse slices — normal study

Provided clinical image

Question

In the type of brain perfusion study shown here, once the radiopharmaceutical has been injected in the appropriate resting environment, approximately how long after injection should SPECT image acquisition typically begin?

  1. AWithin 60 seconds, before the tracer begins to redistribute away from its initial perfusion pattern in the brain
  2. B6–24 hours after injection to allow complete clearance of non-specific circulating background activity
  3. CImmediately after injection while the patient remains in the quiet supine position to capture peak brain activity
  4. D15–30 minutes after injection, allowing the tracer to fix in brain tissue and background activity to clear sufficiently
Show the answer and explanation

D. 15–30 minutes after injection, allowing the tracer to fix in brain tissue and background activity to clear sufficiently

For Tc-99m HMPAO and Tc-99m ECD brain perfusion studies, SPECT acquisition typically begins 15–30 minutes after injection. By this time, the lipophilic tracer has crossed the blood-brain barrier, undergone intracellular conversion to a hydrophilic form, and is fixed in brain parenchyma proportional to perfusion at the time of injection. Starting acquisition too early captures residual circulating tracer and elevated background; waiting too long — especially with Tc-99m HMPAO — may reduce image quality as brain-to-background ratios decline over time.

More brain imaging images

DaTSCAN (I-123 ioflupane) SPECT — midbrain axial sliceDaTscan (I-123 Ioflupane): What It Evaluates Tc-99m HMPAO or ECD brain perfusion SPECT — normal distributionNormal Brain Perfusion SPECT with Tc-99m HMPAO Brain perfusion SPECT — transaxial, coronal, sagittal, and temporal slices showing regional cerebral blood flow pattern in dementiaAlzheimer’s Disease on Brain Perfusion SPECT DaTSCAN (I-123 ioflupane) SPECT — normal striatal uptakeParkinson’s Disease on DaTscan: Loss of the Comma Shape Brain perfusion SPECT — frontal lobe hypoperfusion patternFrontotemporal Dementia on Brain Perfusion SPECT Brain scan statics at 5, 10, and 20 minutes showing absence of cerebral perfusion — only scalp/skull activity visibleBrain Death Scan: Absent Cerebral Perfusion
← Normal Tc-99m ECD Brain SPECT: Gray vs White MatterDaTscan (I-123 Ioflupane): What It Evaluates →

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