A total of nine normal volunteer subjects were studied with three forms of [99mTc] hexamethylpropyleneamineoxime (HM-PAO), a potential cerebral blood flow imaging agent. One, the d,l isomer, showed 4.1% uptake in the brain which remained constant over 8 hr. There was good differentiation between uptake in gray and white matter on tomographic slices. We propose that this agent may allow regional cerebral blood flow imaging to be performed on a routine basis.

https://jnm.snmjournals.org/content/27/2/171.full.pdf

Technetium-99m HM-PAO stereoisomers as potential agents for imaging regional cerebral blood flow: human volunteer studies.

Forty-six patients were studied with N-isopropyl I-123 p-iodoamphetamine (IMP) and the Harvard Scanning Multidetector Brain System. In nine control patients, good differentiation between the gray and white matter of the cerebral cortex and the basal ganglia was evident. Regional uptake was affected by physiologic maneuvers (visual stimulation). In 24 patients studied for stroke, IMP images demonstrated areas that were involved in acute infarction in eight patients whose initial transmission computerized tomography (TCT) was normal; IMP also showed perfusion abnormalities larger than the TCT abnormality in ten patients. Perfusion abnormalities were present in 23/24 of these patients. Seven patients studied with a history of TIA had normal TCT and IMP images. In three patients studied during seizure activity, regions of hyperperfusion corresponded to the EEG seizure focus. Markedly decreased activity was present in three patients with brain tumor and corresponded to the focal abnormality on the TCT study. Our study demonstrates the feasibility of assessing regional brain perfusion using a radiopharmaceutical that is lipid soluble and has a high extraction fraction in the brain, together with single-photon ECT.

https://jnm.snmjournals.org/content/23/3/191.full.pdf

Initial experience with SPECT (single-photon computerized tomography) of the brain using N-isopropyl I-123 p-iodoamphetamine: concise communication

Traumatic aneurysms and arteriovenous fistulas of the extracranial vessels in war injuries

The remote effects of small unilateral cerebrovascular lesions confined to subcortical structures were evaluated by single photon emission computerized tomography (SPECT) and a CBF tracer, I-123 HIPDM. A CBF study was performed in 34 patients presenting with subcortical stroke either in the acute or in the chronic stages. Twenty-one of the 34 patients showed areas of cortical hypoperfusion ipsilateral to the subcortical lesion. In 14 patients, asymmetry of perfusion was also observed at the cerebellar level, perfusion being significantly reduced in the cerebellar hemisphere contralateral to the lesion. There was no correlation between the degree and extension of these remote effects and the type of stroke (ischemic or hemorrhagic), the patency of cerebral arteries, or the size and site of the lesion by transmissive computerized tomography (TCT). Subcortical hematomas showed a correlation between occurrence of remote effects and time interval from the onset of stroke, occurring more frequently in the acute phase. A correlation was observed between cortical and cerebellar remote effects and the severity of clinical presentation. The causes of remote effects are still unclear and have been extensively debated. Our data indicate that there is a relationship of remote effect to the neurological status. It is possible to show, by noninvasive, low-cost methods, remote CBF effects after stroke that may contribute to the assessment of brain functional impairment.

https://journals.sagepub.com/doi/pdf/10.1038/jcbfm.1988.97

Remote Effects of Subcortical Cerebrovascular Lesions: A SPECT Cerebral Perfusion Study

UNLABELLED Cerebral vasospasm is a frequent complication after subarachnoid hemorrhage and contributes to overall morbidity and mortality Arteriography is the standard test for determining the presence of vasospasm A retrospective review of 16 patients with cerebral aneurysm was undertaken to assess the sensitivity and specificity of SPECT for diagnosis of vasospasm Fourteen patients were hospitalized after subarachnoid hemorrhage and 2 patients were hospitalized for elective aneurysmal clipping The patients' condition on discharge was correlated to clinical and SPECT evidence of vasospasm METHODS Vasospasm was defined as the new onset of neurological signs and symptoms not explained by rebleed or hydrocephalus A total of 20 SPECT studies were performed for 16 patients during their admission and 14 of 16 patients had a single angiographic study RESULTS Thirteen of 16 patients had 14 episodes of clinical evidence of vasospasm and 14 SPECT studies were performed in these 13 patients The sensitivity and specificity of SPECT in this retrospective study were 89% (8/9) and 71% (5/7), respectively Our small sample of arteriograms yielded in comparison a sensitivity of 67% (2/3) and specificity of 100% (9/9) The one false-negative SPECT study occurred in conjunction with the one false-negative arteriogram in the presence of clinical findings consistent with vasospasm Three false-positive SPECT studies occurred in 2 patients who had perfusion abnormalities in areas of normal CT findings without clinical or arteriographic evidence of vasospasm Five of 5 patients who died became unresponsive as a result of clinically presumed vasospasm and 4 of 5 of these patients had diffuse or hemispheric SPECT perfusion defects Of the 11 patients who survived, none became unresponsive; 1 of 11 had positive diffuse or hemispheric perfusion defects CONCLUSION SPECT is a sensitive and fairly specific test for corroboration of clinical findings of vasospasm A negative SPECT study may obviate the need for arteriography Unresponsiveness is the best predictor of poor outcome; however, hemispheric SPECT perfusion deficits are also associated with poor outcome

https://jnm.snmjournals.org/content/jnumed/39/5/765.1.full.pdf

SPECT imaging in cerebral Vasospasm following subarachnoid hemorrhage

Continuous carotid infusion of short-lived krypton-81m (t1/2 13 sec) yields an assessment of regional cerebral perfusion. This assessment can be obtained in three dimensions if activity is recorded with a rotating gamma camera and a computer to reconstruct krypton-81m distribution in tomographic sections. These showed several advantages over conventional views: (a) visualization of blood-flow distribution within brain structures (gray and white matter, basal ganglia); (b) more accurate location and evaluation of areas of relatively reduced or increased perfusion; (c) better definition of patterns of collateral circulation; (d) greater sensitivity and specificity in detecting and defining blood-flow changes during physiological activation studies. A limitation of the krypton-81m technique is its invasiveness. However, this study shows that the combination of new advances in radiochemistry with single-photon emission computed tomography may result in accessible methods for assessing, noninvasively and in three dimensions, the behavior of cerebral function in man.

https://jnm.snmjournals.org/content/21/12/1139.full.pdf

Tomographic assessment of cerebral perfusion using a single-photon emitter (krypton-81m) and a rotating gamma camera.

The rCBF was evaluated using I-123 HIPDM and single photon emission computed tomography (SPECT) on 14 patients undergoing extracranial-intracranial (EC-IC) bypass surgery because of internal carotid artery (ICA) occlusion. Before surgery, all patients showed cortical areas of hypoperfusion over the affected cerebral hemisphere. Shortly after EC-IC bypass a rCBF increase was observed in six patients. However, at the 6 and 12 month follow-ups, with angiographic control of bypass patency, rCBF studies did not show any significant rCBF change. Long-term noninvasive tomographic monitoring of perfusion changes occurring after EC-IC bypass surgery failed to show a long-lasting improvement in perfusion.

https://jnnp.bmj.com/content/jnnp/50/8/988.full.pdf

Long-term noninvasive single photon emission computed tomography monitoring of perfusional changes after EC-IC bypass surgery.

The aims of this paper are (1) to report post-operative angiographic results obtained in a series of 40 patients treated by an extra-intracranial arterial bypass (EIAB) procedure, and (2) to describe the patterns of postoperative regional brain perfusion (rBP), as investigated in a limited series of patients, by a new method.

Angiographic Findings and Cross-Sectional Brain Perfusion Studies after Extra-Intracranial Arterial Bypass

Functional images of brain perfusion can be obtained by a steady-state method which exploits the peculiar physical characteristics of the radioactive gas 81mKr.2 This is a very short half-lived isotope (13 sec half-life), which can be continuously produced either in the gaseous or the solution phase from its parent 81Rb (4.6 hours half-life). It emits 190 keV γ rays, an ideal energy for recording with an Anger γ camera. Because of its short half-life, continuous carotid infusion of 81mKr in solution will never eventually result in the equilibrium of this diffusible tracer within the brain; during continuous infusion continuous recording of the activity over the brain will therefore reflect at any time regional arrival of tracer, which is a linear function of regional perfusion. Thus, when used in conjunction with an ordinary Anger γ camera, it provides images of cerebral perfusion in two dimensions.

Regional Cerebral Perfusion Assessed with 81mKr and Emission Computerized Tomography

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Tomographic assessment of cerebral perfusion using a single-photon emitter (krypton-81m) and a rotating gamma camera.

Long-term noninvasive single photon emission computed tomography monitoring of perfusional changes after EC-IC bypass surgery.

Angiographic Findings and Cross-Sectional Brain Perfusion Studies after Extra-Intracranial Arterial Bypass

Regional Cerebral Perfusion Assessed with 81mKr and Emission Computerized Tomography