Single-photon emission computed tomography of brain perfusion: analysis of 60 paediatric cases

Sixty-nine brain perfusion single-photon emission computed tomography (SPECT) scans were performed on 60 paediatric patients with various neurological diagnoses. SPECT was abnormal more frequently in degenerative brain diseases (82 per cent), than in epilepsy (63 per cent), encephalitis (62 per cent), cerebrovascular disease (43 per cent), or other brain disorders (43 per cent). SPECT was more sensitive than EEG, CT and MRI results. SPECT was of considerable value for diagnosis in many cases. It was a decisive aid in two cases, but misleading in another two, so SPECT must be related to findings obtained by clinical and other laboratory methods.     

Single-photon emission computed tomography in distal field hypoperfusion.

To assess the ability of technetium-99m hexamethylpropyleneamineoxime single-photon emission computed tomography (SPECT) imaging to differentiate distal field hypoperfusion from other stroke mechanisms, 24 patients with acute cerebral ischemia were studied. SPECT scans were read by two physicians according to a preestablished set of criteria for distal field hypoperfusion. SPECT patterns read as "probable" or "definite" for distal field hypoperfusion were found in 42% (10/24); of these, 80% (8/10) had ipsilateral carotid occlusion or high-grade stenosis. Severe carotid stenosis was found in 43% (6/14) with SPECT scans negative for distal field hypoperfusion (Fisher exact test [1-tailed] p = 0.0796). The results suggest that a distal field hypoperfusion pattern on SPECT may identify patients with hemodynamically significant large vessel disease.     

Single-photon emission computed tomography of the dopamine transporter in parkinsonism.

The known dopaminergic abnormalities in Parkinson's disease have facilitated the development of radiolabeled biomarkers for diagnostic and research applications in humans. Presynaptic, intrasynaptic, and postsynaptic imaging now is possible using single-photon emission computed tomography. In particular, the development of new radiotracers that target the dopamine transporter located on degenerating dopamine neurons in Parkinson's disease and related disorders is directly relevant to improved clinical diagnosis, disease monitoring, and assessment of putative neuroprotective strategies in patients. In addition, the ability to characterize in vivo neuronal degeneration in these disorders provides a powerful research tool to better understand the natural course of these disorders and could provide clues to etiology.     

Single-photon emission computed tomography and early death in acute ischemic stroke

Single-photon emission computed tomography with thallium-201-labeled diethyldithiocarbamate was performed in 26 consecutive patients less than or equal to 24 hours after a supratentorial brain infarction. Computed tomography excluded other relevant pathology. Two observers assessed the initial regional cerebral blood flow deficit using a semiquantitative visual method. The size of the initial flow deficit correlated negatively with the Barthel Index score (performance of the activities of daily living) after 6 months but not with the motricity index score (a measure of severity of the hemiparesis) after 6 months. The initial flow deficit was strongly correlated with early death from tentorial herniation; all five patients with the largest initial flow deficits died less than or equal to 6 days after the stroke, but among the 21 patients with smaller initial flow deficits only one died early (p = 0.00018, Fisher's exact two-tailed test). Although depressed level of consciousness, conjugate gaze deviation, and severe hemiparesis were more prevalent in the group of six patients who died early, the differences in prevalence between this group and the 20 patients who survived were not significant. Single-photon emission computed tomography is a relatively simple method to semiquantitatively measure a blood flow disturbance immediately after its occurrence. The magnitude of this blood flow disturbance is strongly related to early death from tentorial herniation. Because of these properties, single-photon emission computed tomography to measure regional cerebral blood flow can be of great use in acute stroke research.     

Single-photon emission computed tomography in a patient with ictal metamorphopsia.

Metamorphopsia is a type of visual illusion, which has been reported as a rare ictal manifestation. The patient presented with a simple partial status epilepticus characterised by continuous facial metamorphopsia, intermittently accompanied by elementary visual hallucinations or other types of visual illusions. Subtraction single-photon emission computed tomography images showed an increased perfusion in the ventrolateral aspect of the right temporo-occipital junction (middle and inferior occipital, and inferior temporal gyri). The result suggests that the anatomical substrate involved in the generation of ictal facial metamorphopsia is located in the visual association areas at the right temporo-occipital junction.     

Single-photon emission computed tomography (SPECT) perfusion and neuropsychological performance in mild cognitive impairment

Single-photon emission computed tomography (SPECT) is an affordable neuroimaging technique that measures cerebral perfusion and has been utilized repeatedly in aging populations. However, we are aware of no studies to date examining relationships between SPECT imaging and comprehensive neuropsychological evaluations in a clinical sample of patients with mild cognitive impairment (MCI). Participants were 124 older adults with MCI (age, M = 75.07 years, SD = 7.65; years of education, M = 14.03, SD = 3.09; 60.2% female) who underwent neuropsychological evaluations and brain SPECT scans as part of their routine clinical care. Based on SPECT interpretations, participants were grouped by suspected etiology (i.e., the neuroradiologists noted that hypoperfusion patterns were most consistent with Alzheimer’s disease, AD; frontotemporal lobar degeneration, FTLD; or other disease processes) and regional hypoperfusion (e.g., frontal, temporal, right/left hemisphere). Neuropsychological tests were grouped into domain scores (i.e., attention/processing speed, language, visuospatial, memory, executive; verbal/nonverbal). Consistent with a priori predictions, patients with an AD pattern of hypoperfusion scored lower than comparison groups on the attention/processing speed (partial χ² = 0.10) and memory (partial χ² = 0.07) composites. More patients with the AD-hypoperfusion signal met criteria for amnestic MCI (82%) than did those with a non-AD pattern (70%); this result approached statistical significance (p = .07). Contrary to hypotheses, patients whose SPECT scans were most consistent with FTLD did not underperform on the executive composite, and most regional analyses were nonsignificant. When integrating SPECT data into their clinical conceptualizations of MCI, neuropsychologists should place more weight on AD patterns of hypoperfusion, while de-emphasizing data suggestive of FTLD or regional pathology. Alternative neurodiagnostic markers may be more informative in these instances.     

Single-photon emission computed tomography studies with 99mTc-hexamethylpropyleneamine oxime in dementia: effects of acute administration of L-acetylcarnitine

The acute effects of intravenously administered L-acetylcarnitine (LAC) were evaluated with single-photon emission computed tomography (SPECT) and 99mTc-hexamethylpropyleneamine oxime in 30 demented patients (21 with a clinical diagnosis of Alzheimer's dementia and 9 with mixed-type dementia). Two SPECT scans were performed: in basal conditions, and 30 min after the administration of 500, 1,000, 1,500, or 2,000 mg LAC intravenously. Tracer activity ratios were determined in 10 pairs of cerebellar, cortical and subcortical regions. After administration of the lowest dose of LAC, no changes from the basal values were observed in any of the regions examined. The higher doses of the drug significantly elevated the tracer activity in cortical regions, particularly in the parietal lobe, which showed an impaired regional cerebral blood flow in the basal study. These effects of LAC and their relation with the cholinomimetic properties of the drug are discussed.     

Single photon emission computed tomography (SPET) of the brain

The X-Ray CT scanner and MRI imaging of the brain have changed the study of this organ, in health and in disease. To add to the detailed demonstration of anatomy, functional imaging of the human brain is now carried out by either positron emission computed tomography (PET) or by single photon emission computed tomography (SPET). PET allows for the investigation of brain blood flow, metabolism and many neuroreceptors and is well placed to study the interaction between a drug and the brain. Its clinical (patient-orientated) problem solving potential remains limited--it is too costly a methodology. SPET of the human brain is the affordable, patient-dedicated, alternative. SPET is available in hundreds of departments throughout the U.K. and the E.E.C. Significant progress has been achieved with 99mTc and or 123I-labelled radiopharmaceuticals. Flow studies can be obtained with almost as much detail as most PET flow studies, and progress is at hand with the mapping of neuroreceptor ligands. A metabolic marker for SPET studies is still missing. However flow and metabolism follow a parallel course in most clinically relevant entities (for instance in epilepsy and dementia) -- hence SPET flow maps appear as an attractive alternative to PET. SPET studies of transit (flow/volume) offer an alternative to PET studies of oxygen extraction, since these parameters appear to correlate with each other.     

Positron emission tomography of the cerebellum in autism

On the basis of neurological evidence that autistic patients have fewer Purkinje and granule cells in the cerebellum as well as vermal cerebellar hypoplasia, the authors tested the hypothesis that autistic patients have cerebellar hypofunctioning. They used positron emission tomography of the cerebellum with 18F-labeled 2-deoxyglucose to study seven autistic patients and eight age-matched control subjects. The results showed no significant difference in mean cerebellar glucose metabolism between the two groups, but all mean glucose rates of the autistic patients were either equal to or greater than those of the control subjects. The implications of these findings are discussed.     

Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) of brain tumors

In summary, PET and SPECT are versatile imaging modalities capable of providing dynamic information regarding the metabolism and physiology of brain and brain tumor. PET and SPECT are useful adjuncts to MRI and CT scanning in the important clinical areas of presurgical estimations of tumor grade. In addition, PET can be used to differentiate tumor necrosis from recurrence noninvasively, which is important for patient management. PET also may prove useful in early assessments of metabolic and physiologic changes in brain tumors following treatment and in monitoring drug delivery to tumor. Studies of drug delivery to and metabolic and physiologic responses of brain and brain tumor to treatment provide a quantitative handle on tumor response and patient prognosis. The ability to acquire such quantitative data may lead in the future to more efficient brain tumor treatment algorithms and to the development of more effective treatment protocols.     

Single photon emission computed tomography in long-term survivors of adult brain tumours.

Sixteen patients with primary brain tumours were examined on average eight years after treatment with surgery or whole brain irradiation using standard clinical assessment, CT, a neuropsychological test battery, and single photon emission CT (SPECT) with 99mTc-exametazime. Seventeen lesions were discovered on inspection of SPECT images, 11 with x-ray CT. Quantitative assessment of tracer uptake compared with 16 matched healthy volunteers was consistent with the presence of lesions. Measurement of uptake in brain regions of the hemisphere not containing the primary tumour still showed significant reductions in patients. This may be due to remote direct effects of the tumour or, more likely, to the whole brain irradiation received. Psychometric performance on most tests was significantly impaired in the patient group and was correlated with abnormalities of tracer uptake to relevant brain regions.     

Single-photon emission-computed tomography of the brain in craniopharyngiomas in the late postoperative period

The paper analyzes tomographic scanning images of 32 patients with craniopharyngiomas in the late postoperative period. Computed tomographic data allowed the patients to be divided into 3 groups: 1) 10 patients without signs of tumor recurrence or hydrocephalus; 2) 14 patients with recurrent cystic craniopharyngiomas; 3) 8 patients with severe hydrocephalus. Single photon emission computed tomography (SPECT) of the brain indicated regional disturbances of brain tissue blood supply in the frontobasal or frontobasotemporal regions of the right hemisphere (the area of an surgical access and of the removed tumor) and revealed them in the distal areas (frontobasotemporal regions of the left hemisphere, parietal and occipital cortices of the cerebral hemisphere or cerebellar tissue). The compensatory reserves of cerebral circulation were assessed by the foci of relative physiological hyperemia of brain tissue (the cerebellum and the medial portions of the occipital regions of the brain). The findings provide evidence for that the vascular factor is involved in the late postoperative pathological picture in patients with craniopharyngiomas.     

Predictive value of brain perfusion single-photon emission computed tomography in acute ischemic stroke

We investigated 32 patients with completed ischemic stroke less than or equal to 6 hours after the onset of symptoms by means of computed tomography, cerebral angiography, and technetium-99m-labeled hexamethylpropyleneamine oxime single-photon emission computed tomography to study cerebral blood flow. Follow-up computed tomography and cerebral blood flow studies were performed 1 week and 1 month after admission. Poor outcome at 1 month was evident in 18 (78%) of the 23 patients with severe neurologic deficit on admission and in 11 (92%) of the 12 patients with severe hypoperfusion in the affected hemisphere on admission. All 10 patients with severe impairment of both neurologic status and cerebral blood flow had a poor outcome at 1 month. We detected severe hypoperfusion in patients with large lesions on computed tomograms or cerebral artery occlusions on angiograms. Cerebral blood flow had increased at the 1-week follow-up despite different clinical outcomes. Our data provide evidence that early evaluation of cerebral blood flow with single-photon emission computed tomography is useful to detect subgroups of patients with different clinical outcomes during the acute phase of ischemic stroke.     

Forensic applications of cerebral single photon emission computed tomography in mild traumatic brain injury

Traumatic brain injury (TBI) is a substantial source of mortality and morbidity world wide. Although most such injuries are relatively mild, accurate diagnosis and prognostication after mild TBI are challenging. These problems are complicated further when considered in medicolegal contexts, particularly civil litigation. Cerebral single photon emission computed tomography (SPECT) may contribute to the evaluation and treatment of persons with mild TBI. Cerebral SPECT is relatively sensitive to the metabolic changes produced by TBI. However, such changes are not specific to this condition, and their presence on cerebral SPECT imaging does not confirm a diagnosis of mild TBI. Conversely, the absence of abnormalities on cerebral SPECT imaging does not exclude a diagnosis of mild TBI, although such findings may be of prognostic value. The literature does not demonstrate consistent relationships between SPECT images and neuropsychological testing or neuropsychiatric symptoms. Using the rules of evidence shaped by Daubert v. Merrell Dow Pharmaceuticals, Inc., and its progeny to analyze the suitability of SPECT for forensic purposes, we suggest that expert testimony regarding SPECT findings should be admissible only as evidence to support clinical history, neuropsychological test results, and structural brain imaging findings and not as stand-alone diagnostic data.     

Brief report: Attention performance in autism and regional brain metabolic rate assessed by positron emission tomography

The Stallone Foundation and the MacArthur Foundation provided partial support for this research. Andrew Russell, Linda Bott, and Cathy Sammons did the diagnostic interviews.     

Positron emission tomography of the brain

Positron emission tomography (PTE) is a technique that allows imaging of the temporal and spatial distribution of positron-emitting radionuclides. The purpose of this article is to outline the current clinical use for PET imaging in the brain and other radiopharmaceutical used for assessing various physiologic parameters pertaining to tumor metabolism.