Cerebral Blood Flow Tomography Research Articles

Comparison of perfusion 18F-FP-CIT PET and 99mTc-ECD SPECT in parkinsonian disorders.

Early and accurate identification of various conditions that can cause parkinsonian symptoms is important for determining treatment policies. Currently dopamine transporter (DAT) imaging using FP-CIT, glucose metabolism imaging using fluorodeoxyglucose, cerebral blood flow image using ethyl cysteinate dimer (ECD), and others are used for differentiation. However, the use of multiple modalities is inconvenient and costly. In the present retrospective study, we evaluated the correlation between regional brain uptake ratios (URs) in perfusion FP-CIT PET and ECD SPECT images.Twenty patients with Parkinson's symptoms underwent perfusion DAT positron emission tomography (18F-FP-CIT PET/CT) and cerebral blood flow tomography (99mTc-ECD SPECT) within a 2-week period. Perfusion 18F-FP-CIT PET/CT and 99mTc-ECD SPECT URs of 19 brain regions (bilateral frontal, temporal, parietal and occipital lobes, bilateral caudate nucleus, bilateral putamen, bilateral insula, bilateral cingulate gyrus, bilateral thalamus, and brainstem) were directly compared and correlations were analyzed.Average 18F-FP-CIT PET/CT regional perfusion URs were higher than 99mTc-ECD SPECT URs. Uptake ratios were well correlated in all 19 regions (except right putamen), and especially in dopamine poor regions (cerebral cortex). In left putamen, URs were significantly correlated, but the correlation coefficient was lower than those of other regions.A single tracer dual phase N-3-fluoropropyl-2-beta-carboxymethoxy-3-beta-(4-iodophenyl) nortropane test seems to be helpful for differential diagnosis of parkinsonian disorders. Large-scale, longitudinal studies on complementary diseases with parkinsonian patterns are required to investigate differences in correlations between perfusion 18F-FP-CIT PET/CT and 99mTc-ECD SPECT over time.

Cerebral blood flow tomography by SPECT in Alzheimer's disease

A brief review is presented of the changes seen in cerebral blood flow (CBF) in probable Alzheimer's disease studied by 99mTc-HMPAO and SPECT. Compared with age-matched controls Alzheimer's disease subjects show abnormal flow reductions in practically 100% of cases even in fairly early stages of the disease. The pattern of flow reduction is variable. The most characteristic (diagnostic) abnormality is an almost symmetrical bitemporoparietal flow reduction. Highly asymmetric patterns are also seen. The abnormality is highly reproducible, showing a slow progression over years. These CBF images may in particular be of value in gerontopsychiatry and in pharmacological studies, where the diagnostic certainty should be as high as possible.

Frontal Impairment and Hypoperfusion in Neuroacanthocytosis

Cerebral blood flow tomography, by xenon 133 inhalation or HMPAO (99mTc-d, l-hexamethyl-propylene amine oxime) technetium Tc 99m injection, revealed a severe hypoperfusion in both frontal lobes of a 40-year-old woman with confirmed neuroacanthocytosis. This finding occurred in conjunction with neuropsychological deficits consistent with selective frontal lobe dysfunction. This observation is the first documentation of this type of dementia in neuroacanthocytosis.

Pathophysiology of Brain Ischemia as It Relates to the Therapy of Acute Ischemic Stroke

Current knowledge of the pathophysiology of cerebral ischemia, summarized in the present study, predicts that neurological deficits caused by moderate ischemia (flows in the penumbral range between 23 and 10 ml/100 g/min) are reversible provided flow is restored within 3-4 h of onset. It also predicts that areas of dense ischemia cannot be salvaged and that reperfusion of such areas is risky, because massive edema or even hemorrhage may develop following reperfusion. On this basis, it is argued that selection of stroke cases for thrombolysis or surgical revascularization must be based not only on computed tomographic (CT) scanning to exclude hemorrhagic stroke, but also on cerebral blood flow (CBF) tomography to exclude lacunar infarcts, early reperfusion, and dense ischemia. The methods available for routing CBF tomography in acute stroke cases are discussed, and it is concluded that single photon emission computed tomography (SPECT) using [99mTc]hexamethyl propyleneamine oxide (HM-PAO) or [99mTc]ethyl cysteinate dimer (ECD) should be explored for this use. In concluding, the glutamate receptor antagonist is mentioned. This compound is therapeutically active in some animal stroke models. In humans, it is probably used only in the acute phase, and in those in whom some degree of collateral flow is preserved. Therefore, even with this therapeutic approach, CBF tomography may be of value for patient selection.

Cerebral blood flow tomography with xenon-133

Cerebral blood flow (CBF) can be measured tomographically by inhalation of Xenon-133. The calculation is based on taking a sequence of tomograms during the wash-in and wash-out phase of the tracer. Due to the dynamic nature of the process, a highly sensitive and fast moving single photon emission computed tomograph (SPECT) is required. Two brain-dedicated SPECT systems designed for this purpose are mentioned, and the method is described with special reference to the limitations inherent in the soft energy of the 133Xe primary photons. CBF tomography can be used for a multitude of clinical and investigative purposes. This article discusses in particular its use for the selection of patients with carotid occlusion for extracranial/intracranial bypass surgery, for detection of severe arterial spasm after aneurysm bleeding, and for detection of low flow areas during severe migraine attacks. The use of other tracers for CBF tomography using SPECT is summarized with emphasis on the 99mTc chelates that freely pass the intact blood-brain barrier. The highly sensitive brain-dedicated SPECT systems described are a prerequisite for achieving high resolution tomograms with such tracers.