Equis ISSN 2398-2977

Brain: scintigraphy

Contributor(s): Russel Malton, Rachel Murray

Introduction

  • Conventional radionuclide brain imaging was originally developed for the detection of  intracranial neoplasms. 
  • Interpretation relies on exclusion of the injected radiopharmaceutical from the brain parenchyma by the blood brain barrier in normal patients.  
  • Disruption of the blood brain barrier by intracranial lesions such as tumors, abscesses or cysts allows the radiopharmaceutical to localize in the brain substance.
  • The availability of conventional equipment and relatively low cost along with the ability to carry out the procedure in a standing sedated patient makes planar brain scintigraphy a reasonable option for evaluating the equine brain.
  • Two-dimensional planar images are not able to detect subtle changes in regional brain uptake of radiopharmaceutical limiting the use of conventional scintigraphy in cerebral blood flow studies.

Radiopharmaceuticals

  • 99mTc-DTPA (Diethylenetriaminepentaacetic acid) is confined to the blood pool, does not pass the normal blood brain barrier and is cleared rapidly by the kidneys minimizing background activity.
  • 99mTc-GHA (Glucoheptonate) has similar properties to DTPA but is cleared more slowly from the blood pool. 99mTc-GHA provides good lesion: background contrast and was formerly the agent of choice but is no longer available.
  • 99mTc-pertechnetate: scans obtained are of poorer quality as a result of normal accumulation of this agent in choroids plexus and salivary glands and slower blood clearance resulting in higher background activity.
  • 99mTc-HMPAO (Hexamethylpropyleneamine oxime) is a lipophilic molecule which diffuses past the blood brain barrier and is thought to be trapped in the intracellular compartment of the brain by its conversion to a hydrophilic compound. Distribution of this agent provides a map of cerebral blood flow however detection of filling defects in most cases requires high spatial and contrast resolution which cannot be achieved with planar scintigraphy.

Dosage

  • Radioactivity of the radiopharmaceuticals used with reported success are in the range of 2.8-3.7 GBq. 
  • The dose range in all studies carried out in adult horses by this author is 3.0-4.5 GBq.

Uses

  • Planar scintigraphy is indicated for:
    • Suspected intracranial space-occupying lesions, eg tumor, abscess.
    • Seizures where extracranial causes have been ruled out.
    • Further evaluation of  head trauma with suspected brain injury.
    • Unexplained behavioral changes with suspected intracranial etiology.
    • Cranial nerve disorders.

Requirements

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Preparation

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Procedure

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Aftercare

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Archer D C et al (2003) Scintigraphic appearance of selected diseases of the equine head. Equine Vet Educ 15 (6), 305-313 Wiley Online Library.
  • Barakzai S Z & Dixon P M (2003) Effect of sinus trephination on scintigraphy of the equine skull. Vet Rec 152 (20), 629-630 PubMed.
  • Dykes N L, Warnick L D, Summers B A et al (1994) Retrospective analysis of brain scintigraphy in 116 dogs and cats. Vet Radiol 35 (1), 59-65 VetMedResource.
  • Daniel G B, Twardock A R, Tucker R L et al (1992) Brain scintigraphy. Prog Vet Neurol (1), 25-34 VetMedResource.

Other sources of information

  • Dykes N L (1996)Conventional (Planar) Brain Scintigraphy.In:Handbook of Veterinary Nuclear Medicine.Eds: Berry C R & Daniel G B. North Carolina State University, Raleigh, NC, USA. pp 133-137.


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