Serial Semiquantitative Imaging of Brain Damage Using Micro-SPECT and Micro-CT After Endothelin-1–Induced Transient Focal Cerebral Ischemia in Rats

In this study, we validated the use of 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) micro-SPECT combined with micro-CT for semiquantification of the infarct size after an experimental stroke in rats and compared our observations with those obtained from histology. This imaging strategy was applied to measure the longitudinal effect of mild hypothermia on the progression of brain damage after stroke in rats. Methods: The endothelin-1 model was used to elicit a transient focal cerebral ischemia in rats. This resulted in a reproducible insult in which the core is represented by the striatum and the penumbra by the cortex. Micro-SPECT and micro-CT images were taken at 1, 3, and 7 d after infusion of endothelin-1 and compared with those taken before the insult. After the last acquisition, rats were sacrificed and the infarct volume was determined via Nissl staining. The results obtained with micro-SPECT and micro-CT were compared with histology at the same time points. Mild hypothermia (33°C) was induced for 2 h, starting 20 min after the insult. Results: Brain damage was estimated using micro-SPECT and micro-CT and was reproducible with minimal interobserver variability. Normothermic stroke rats had reduced 99mTc-HMPAO uptake at 1 and 3 d after the insult, whereas hypothermia improved damage after stroke. These findings corroborate with histology at the same time points. At 1 wk after the insult, no reduction of radioactive uptake was observed in any treatment group. Conclusion: Micro-SPECT and micro-CT allow quick and reproducible semiquantification of brain damage as an interesting alternative to histology to measure the extent of infarcted tissue in small animals after stroke.

[1]  G. Steinberg,et al.  Optimal depth and duration of mild hypothermia in a focal model of transient cerebral ischemia: effects on neurologic outcome, infarct size, apoptosis, and inflammation. , 1998, Stroke.

[2]  J. Sharkey.  Perivascular Microapplication of Endothelin-1: A New Model of Focal Cerebral Ischaemia in the Rat , 1993, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[3]  Michel Defrise,et al.  Improved quantification in single-pinhole and multiple-pinhole SPECT using micro-CT information , 2009, European Journal of Nuclear Medicine and Molecular Imaging.

[4]  Frans van der Have,et al.  The pinhole: gateway to ultra-high-resolution three-dimensional radionuclide imaging , 2007, European Journal of Nuclear Medicine and Molecular Imaging.

[5]  G. Donnan,et al.  Sensitivity and specificity of 99mTc-HMPAO SPECT cerebral perfusion measurements during the first 48 hours for the localization of cerebral infarction. , 1997, Stroke.

[6]  S. Schwab,et al.  Hypothermia in focal ischemia: implications of experiments and experience. , 2009, Journal of neurotrauma.

[7]  T. Wieloch,et al.  Long-lasting neuroprotective effect of postischemic hypothermia and treatment with an anti-inflammatory/antipyretic drug. Evidence for chronic encephalopathic processes following ischemia. , 1996, Stroke.

[8]  D. Corbett,et al.  A serial MR study of cerebral blood flow changes and lesion development following endothelin‐1‐induced ischemia in rats , 2001, Magnetic resonance in medicine.

[9]  N. Jones,et al.  Inflammatory Cell Infiltration after Endothelin-1-Induced Cerebral Ischemia: Histochemical and Myeloperoxidase Correlation with Temporal Changes in Brain Injury , 2007, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[10]  G. Calo’,et al.  New insights on flow-independent mechanisms of 99mTc-HMPAO retention in nervous tissue: in vitro study. , 1999, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.

[11]  S. Meikle,et al.  Small animal SPECT and its place in the matrix of molecular imaging technologies , 2005, Physics in medicine and biology.

[12]  L. Swanson.  The Rat Brain in Stereotaxic Coordinates, George Paxinos, Charles Watson (Eds.). Academic Press, San Diego, CA (1982), vii + 153, $35.00, ISBN: 0 125 47620 5 , 1984 .

[13]  R. Sapolsky,et al.  General versus Specific Actions of Mild-Moderate Hypothermia in Attenuating Cerebral Ischemic Damage , 2007, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[14]  B. Siesjö,et al.  Regional Cerebral Blood Flow during and after 2 Hours of Middle Cerebral Artery Occlusion in the Rat , 1997, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[15]  Michel Defrise,et al.  Reproducibility of left ventricular volume and ejection fraction measurements in rat using pinhole gated SPECT , 2005, European Journal of Nuclear Medicine and Molecular Imaging.

[16]  T. Kawase,et al.  Post-ischemic hypothermia delayed neutrophil accumulation and microglial activation following transient focal ischemia in rats , 2000, Journal of Neuroimmunology.

[17]  D. Mathews,et al.  Calcium 45 autoradiography and dual-isotope single-photon emission CT in a canine model of cerebral ischemia and middle cerebral artery occlusion. , 1996, AJNR. American journal of neuroradiology.

[18]  C. Vanhove,et al.  Effect of high-intensity ultrasound-targeted microbubble destruction on perfusion and function of the rat heart assessed by pinhole-gated SPECT. , 2010, Ultrasound in medicine & biology.

[19]  E. Candelario-Jalil,et al.  Injury and repair mechanisms in ischemic stroke: considerations for the development of novel neurotherapeutics. , 2009, Current opinion in investigational drugs.

[20]  Michel Defrise,et al.  Interest of the ordered subsets expectation maximization (OS-EM) algorithm in pinhole single-photon emission tomography reconstruction: a phantom study , 2000, European Journal of Nuclear Medicine.

[21]  Y. Michotte,et al.  Neurochemical changes and laser Doppler flowmetry in the endothelin-1 rat model for focal cerebral ischemia , 2000, Brain Research.

[22]  L. Agnati,et al.  Short- and long-term changes in striatal neurons and astroglia after transient forebrain ischemia in rats. , 1997, Stroke.

[23]  Youngho Seo,et al.  Rodent brain imaging with SPECT/CT. , 2007, Medical physics.

[24]  F. Beekman,et al.  U-SPECT-II: An Ultra-High-Resolution Device for Molecular Small-Animal Imaging , 2009, Journal of Nuclear Medicine.

[25]  E. Samaniego.  Therapeutic Hypothermia in Acute Stroke , 2013 .

[26]  W D Heiss,et al.  Ischemic Penumbra: Evidence From Functional Imaging in Man , 2000, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[27]  Turgut Tatlisumak,et al.  Acute ischemic stroke: Overview of major experimental rodent models, pathophysiology, and therapy of focal cerebral ischemia , 2007, Pharmacology Biochemistry and Behavior.

[28]  Y. Michotte,et al.  Effect of resuscitative mild hypothermia on glutamate and dopamine release, apoptosis and ischaemic brain damage in the endothelin‐1 rat model for focal cerebral ischaemia , 2003, Journal of neurochemistry.

[29]  Michael Chopp,et al.  Temporal profile of microglial response following transient (2h) middle cerebral artery occlusion , 1997, Brain Research.

[30]  K. Langen,et al.  Technetium-99m-HMPAO, technetium-99m-ECD and iodine-123-IMP cerebral blood flow measurements with pharmacological interventions in primates. , 1997, Journal of nuclear medicine : official publication, Society of Nuclear Medicine.