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Overview

Background

Brain perfusion single-photon emission computed tomography (SPECT) imaging is a functional nuclear imaging technique performed to evaluate regional cerebral perfusion. Because cerebral blood flow is closely linked to neuronal activity, the activity distribution is presumed to reflect neuronal activity levels in different areas of the brain. A lipophilic, PH-neutral radiopharmaceutical (most commonly technetium-99m-hexamethylpropyleneamine oxime [HMPAO] and ^99mTc-ethylene cysteine diethylester [ECD], with a half-life of 6.02 hours) is injected into the patient, which crosses the blood-brain barrier and continues to emit gamma rays. A 3-dimensional representation of cerebral blood flow can be iterated using gamma detectors, allowing for interpretation.^{[1, 2, 3, 4]}

Brain SPECT can be complemented with pharmaceutical agents that enhance regional cerebral blood flow, such as acetazolamide (carbonic anhydrase). Acetazolamide increases local pCO₂ and causes arteriolar dilation, allowing for assessment of cerebrovascular reserve in transient ischemic attack, stroke, and vascular anomalies and distinguishing vascular from neuronal causes of dementia.^{[5, 6, 7]}

(See the brain SPECT images below.)

Three-dimensional SSP quantitative maps.

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Three-dimensional SSP quantitative maps confirm widespread reduction in cortical activity, most marked in the temporal lobes

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Indications

Brain perfusion SPECT imaging can aid in the diagnosis and ongoing evaluation of many different medical conditions, such as the following:

Detection and evaluation of cerebrovascular disease
Aid in the diagnosis and differential diagnoses of suspected dementia
Detection of seizure focus
Assessment of brain death
Evaluating suspected brain trauma
Neuropsychiatric disorders: Mood disorders, evaluating and subtyping attention-deficit disorder
Substance abuse
Infection/inflammation

American College of Radiology (ACR) – Society of Pediatric Radiology (SPR) Guidelines

A joint ACR-SPR practice parameter on the performance of SPECT brain perfusion imaging examinations includes the following indications^[8]:

Evaluating patients with suspected dementia
Localizing epileptic foci preoperatively
Diagnosing encephalitis
Monitoring and assessing vascular spasm following subarachnoid hemorrhage
Mapping of brain perfusion during interventions
Detecting and evaluating cerebrovascular disease
Predicting the prognosis of patients with cerebrovascular accidents
Corroborating the clinical impression of brain death

For other indications, such as neuropsychiatric disorders and chronic fatigue syndrome, the findings of SPECT brain perfusion imaging have not been fully characterized. In HIV encephalopathy, SPECT brain perfusion imaging can detect altered brain perfusion.

Contraindications

Brain SPECT imaging is contraindicated in the following:

Pregnancy
Breastfeeding (this should be interrupted for 24 hours prior to imaging)
Lack of cooperation

The use of acetazolamide is contraindicated in patients with a known sulfa allergy or advanced liver disease and may trigger a migraine in patients with migraine history. Acetazolamide should be avoided for 3 days after acute stroke or recent transient ischemic attack.^[8]

Brain SPECT imaging is a safe procedure on the whole. However, care must be provided by the imaging technologist to reduce patient discomfort and minimize motion artifact. Care must also be provided to avoid tissue extravasation of radiopharmaceutical agents, as there is potential to induce tissue necrosis.

Periprocedure

Juni JE, Waxman AD, Devous MD Sr, Tikofsky RS, Ichise M, Van Heertum RL, et al. Procedure guideline for brain perfusion SPECT using (99m)Tc radiopharmaceuticals 3.0. J Nucl Med Technol. 2009 Sep. 37(3):191-5. [QxMD MEDLINE Link].
Kapucu OL, Nobili F, Varrone A, Booij J, Vander Borght T, Någren K, et al. EANM procedure guideline for brain perfusion SPECT using 99mTc-labelled radiopharmaceuticals, version 2. Eur J Nucl Med Mol Imaging. 2009 Dec. 36(12):2093-102. [QxMD MEDLINE Link].
Rossini F, Zauner H, Bergmann J, Kronbichler M, Spindler I, Golaszewski S, et al. HMPAO-SPECT Can Discriminate between Patients with Subjective Cognitive Complaints with and without Cognitive Deficits and those with Mild Cognitive Impairment. Curr Alzheimer Res. 2019. 16 (9):843-851. [QxMD MEDLINE Link].
Van Patten R, Greif T, Britton K, Tremont G. Single-photon emission computed tomography (SPECT) perfusion and neuropsychological performance in mild cognitive impairment. J Clin Exp Neuropsychol. 2019 Jul. 41 (5):530-543. [QxMD MEDLINE Link].
Farid K, Petras S, Ducasse V, Chokron S, Helft G, Blacher J, et al. Brain perfusion SPECT imaging and acetazolamide challenge in vascular cognitive impairment. Nucl Med Commun. 2012 Jun. 33(6):571-80. [QxMD MEDLINE Link].
Yamauchi M, Imabayashi E, Matsuda H, Nakagawara J, Takahashi M, Shimosegawa E, et al. Quantitative assessment of rest and acetazolamide CBF using quantitative SPECT reconstruction and sequential administration of (123)I-iodoamphetamine: comparison among data acquired at three institutions. Ann Nucl Med. 2014 Nov. 28 (9):836-50. [QxMD MEDLINE Link].
Johnston M. Brain SPECT imaging with acetazolamide challenge. J Nucl Med Technol. 2013 Mar. 41 (1):52-4, 10A. [QxMD MEDLINE Link].
[Guideline] American College of Radiology and the Society for Pediatric Radiology. ACR-SPR Practice Parameter for the Performance of Single Photon Emission Computed Tomography (SPECT) Brain Perfusion Imaging, including Brain Death Examinations. ACR.org. Available at https://www.acr.org/-/media/ACR/Files/Practice-Parameters/BrainPerf-SPECT.pdf?la=en. October 1, 2016; Accessed: October 20, 2019.
Kranert T, Menzel C, Bartenstein P, Brust P, Coenen HH, Krause BJ, et al. [Perfusion brain imaging with SPECT-technique. German Guideline S1]. Nuklearmedizin. 2013. 52(5):157-62; quiz N55. [QxMD MEDLINE Link].
Thrall J, Ziessman H. Central Nervous System. Nuclear Medicine - The Requisites. 1st Ed. United States of America: Mosby; 1995. Nuclear Medicine: 11.
Sawada H, Orimo S. [Relationship between striatal ¹²³I-FP-CIT uptake and cognitive functions in Parkinson's disease]. Rinsho Shinkeigaku. 2019 Dec 25. 59 (12):799-805. [QxMD MEDLINE Link].
Amen DG, Krishnamani P, Meysami S, Newberg A, Raji CA. Classification of Depression, Cognitive Disorders, and Co-Morbid Depression and Cognitive Disorders with Perfusion SPECT Neuroimaging. J Alzheimers Dis. 2017. 57 (1):253-266. [QxMD MEDLINE Link].
Murray I.P.C, Ell P.J. Lipophilic tracers for the study of regional cerebral blood flow. Van der Wall.H, William Strauss.H. Nuclear Medicine in Clinical Diagnosis and Treatment. 2nd Ed. Edinburgh: Churchill Livingstone; 1998. 1: 42.

Media Gallery

History of THC abuse with 2-month history of psychosis and cognitive decline. There is a normal pattern of brain perfusion throughout the neocortical structures, corpus striatum, brain stem, and cerebellum.
Three-dimensional SSP quantitative maps.
Three-dimensional SSP quantitative maps
Patient with right hemiparesis with left carotid stenosis and mid-basilar artery occlusion. Acetazolamide stress perfusion demonstrates mild reduction in perfusion to bilateral frontotemporal and basal ganglia regions when compared to baseline. Mild reduction in perfusion to the superior aspect of the cerebellum bilaterally
Reduced activity throughout the neocortices with sparing of the occipital lobes and paracentral gyri
Three-dimensional SSP quantitative maps confirm widespread reduction in cortical activity, most marked in the temporal lobes
Three-dimensional SSP quantitative maps
Patient presents with cognitive impairment with preservation of short-term memory. Tomographic images shows reduced tracer uptake in the frontal lobes, more prominent on the right and in the temporal lobes, more marked on the left. Tracer uptake in the parietal and occipital lobes and deep gray matter preserved. Three-dimensional SSP maps confirm this impression.
Three-dimensional SSP quantitative maps
History of generalized slurring, tremor, confusions and delusions. Tomographic images confirm bilateral, asymmetrical hypoperfusion involving the parietal lobes, temporal lobes, and occipital lobes. Pattern supportive of Lewy body disease
Delayed planar saved images demonstrate absent tracer uptake in the cerebral hemispheres, cerebellum, basal ganglia, and brain stem.
Three-dimensional SSP quantitative maps
Three-dimensional SSP quantitative maps
Left temporal ictal hyperperfusion with subtraction images showing difference between the ictal and interictal scans. There is likely left anterior temporal seizure focus. Three-dimensional SSP maps confirm this impression.
Patient was investigated for memory and visual spatial impairment. There are bilateral frontal lobe changes being marked on the left with lesser left temporal involvement, suggestive of frontotemporal neurodegenerative process.
Three-dimensional SSP quantitative maps.
Asymmetrical uptake in the cerebral hemispheres with markedly reduced tracer uptake in the left temporal and parietal lobes. Uptake in the left sensorimotor cortex appears normal.
Three-dimensional SSP quantitative maps.

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Table 1. Tracer Information ^[13]

	Tc-99m HMPAO	Tc-99m ECD
Transport mechanism	Neutral lipophilic compound	Neutral lipophilic compound
First-pass cerebral extraction	80%	60-70%
Peak activity	1-2 min postinjection 4-7% of the dose remains within the brain	1-2 min postinjection 6-7% of the dose remains within the brain
Advantage	Less radiation dose	Rapid brain uptake with excellent brain retention Higher brain-to-background ratio Higher gray-to-white matter ratio
Disadvantage	Poor stability Dose needs to be used within 30 min postreconstitution	Higher radiation dose Currently not available in Australia
Trapping mechanism	Trapped in all living cells; glutathione-mediate conversion to hydrophilic complex	Trapped only in metabolically intact cells and not retained during transient dysfunction; enzymatic (esterases) conversion to hydrophilic products

Table 2. Radiation Dosimetry in Adults

Radiopharmaceutical

Administered Activity, MBq (mCi)

Organ Receiving the Largest Radiation Dose, mGy (rad)

Effective Dose, mSv (rem)

Tc-99m HMPAO

555-1110 IV

(15-30)

0.034

Kidneys

(0.126)

0.0093

(0.034)

Tc-99m ECD

555-1110 IV

(15-30)

0.073

Bladder wall

(0.27)

0.011

(0.041)

Table 3. Radiation Dosimetry in Children

Radiopharmaceutical

Administered Activity,

MBq/kg

(mCi/kg)

Organ Receiving the Largest Radiation Dose, mGy (rad)

Effective Dose, mSv (rem)

Tc-99m HMPAO

7.4–11.1 IV

(0.2-0.3)

0.14

Thyroid

(0.52)

0.026

(0.096)

Tc-99m ECD

7.4-11.1 IV

(0.2-0.3)

0.083

Bladder wall

(0.31)

0.023

(0.085)

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SPECT Brain Imaging

Background

Indications

American College of Radiology (ACR) – Society of Pediatric Radiology (SPR) Guidelines

Contraindications

References

Tables

Contributor Information and Disclosures

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