Single photon emission tomography using 99mTc-HM-PAO in the investigation of dementia.

Single photon emission tomographic imaging of the brain using 99mTc HM-PAO was carried out in patients with a clinical diagnosis of Alzheimer's disease, non-Alzheimer frontal-lobe dementia, and progressive supranuclear palsy. Independent assessment of reductions in uptake revealed posterior hemisphere abnormalities in the majority of the Alzheimer group, and selective anterior hemisphere abnormalities in both other groups. The findings were consistent with observed patterns of mental impairment. The imaging technique has potential value in the differential diagnosis of primary cerebral atrophy.     

躯体形式障碍35例SPECT研究

目的　探讨躯体形式障碍脑灌注特点与潜在意义。方法　开放性收集门诊和住院诊断 为躯体形式障碍病人35例;进行99mTc 双半胱乙脂(ECD)单光子发射型计算机断层显像(SPECT)脑血 流灌注(rCBF)断层显像,半定量测定rCBF。结果　35例躯体形式障碍病人均出现有不同部位的脑 低灌注现象;具体为右额叶(13例,37%),左额叶(11例,31%),右颞叶(13例,37%),左颞叶(11例, 31%),右顶叶(11例,31%),左顶叶(4例,11%),右基底节(14例,40%),左基底节(17例,49%),右丘 脑(1例,3%),左丘脑(1例,3%),盐酸文拉法辛治疗2周后不同部位脑血流低灌注均明显改善,差异 有显著性(P<0.05)。结论　躯体形式障碍不同临床表现相应呈现额叶、基底节、颞叶、顶叶不同区域 脑血流低灌注,治疗后明显改善。     

Diagnosing Alzheimer's disease in elderly,mildly demented patients: the impact of routine single photon emission computed tomography

Based on the observation of bilateral temporoparietal hypoperfusion in Alzheimer's disease (AD), single photon emission computed tomography (SPECT) is advocated by some as a powerful diagnostic tool in the evaluation of demented patients. We studied whether routine brain SPECT in elderly, mildly demented outpatients increases the a priori diagnostic sensitivity and specificity of a careful clinical examination.^99mTc-HMPAO SPECT imaging was performed in 110 patients for a first evaluation for dementia. A semiquantitative measure of temporoparietal (TP) perfusion was calculated as the ratio of the activity in the temporoparietal cortex to activity in the cerebellum. A diagnosis of probable AD according to the McKhann criteria was made in 68 patients (mean age of 79.3 years) based on the results of a clinical examination, ancillary investigations and a 6-month follow-up. TP perfusion was significantly lower in AD patients than in 18 age-matched, non-demented controls. However, at a specificity of 89%, sensitivity was only 43% for detecting probable AD. The clinicians judged that SPECT had contributed to the final diagnosis in only 8% of the demented patients investigated. Routine brain SPECT in elderly, mildly demented outpatients does not contribute substantially to diagnostic accuracy after a careful clinical examination using current diagnostic criteria. Clinical guidelines have to be developed for the use of SPECT in patients with (suspected) dementia.     

Predicting the accuracy of a diagnosis of Alzheimer's disease with 99mTc HMPAO single photon emission computed tomography

The current clinical practice of reporting images obtained with single photon emission computed tomography (SPECT) with 99mTc-d,l-hexamethylpropylene amine oxime (99mTc HMPAO) images was examined by having 16 experts evaluate the appearance of SPECT images in patients with probable Alzheimer type dementia (ATD), patients with major depressive episode (DSM-IV), and healthy volunteers. The experts rated diagnostic criteria of scan appearance in respect of importance for their individual diagnostic practice. Experts were nuclear medicine specialists, psychiatrists and physicists taking part in a European multi-centre collaborative project. They examined 158 perfusion scans and then the same perfusion scans together with statistical parametric maps (SPMs). The sensitivity of experts' diagnostic judgments was significantly and negatively correlated with the importance they attributed to reduced regional perfusion in the parietal lobes. A corresponding positive correlation was observed for diagnostic specificity against depressed and healthy volunteers. Similar results were observed with SPMs, where in addition area under the receiver operating characteristic (ROC) curve was significantly reduced with raters' increased diagnostic reliance on frontal lobe perfusion deficits. Sensitivity was greater with SPM for patients younger than 70 years and with dementia severity. The more importance experts placed on parietal (symmetrical) perfusion deficits, the less sensitive and the more specific their diagnostic judgment was. Using multiple raters in large patient samples may provide a way of identifying successful explicit diagnostic strategies for clinical image analysis.     

Single photon emission computed tomography with99mTc HM-PAO in the study of focal epilepsy

We used^99mTc HM-PAO SPECT to study 50 patients with partial epilepsy: 47 interically and 3 during a seizure. All 3 patients studied during a seizure presented an area of increased tracer uptake. Of those in whom recordings were taken during seizure-free intervals 35 (74%) showed perfusion asymmetries: 27 (57%) with decreased and 8 (17%) with increased uptake. We discuss the findings and compare them with those of similar studies using SPECT and positron emission tomography.     

Single photon emission computed tomography in Alzheimer's disease. Abnormal iofetamine I 123 uptake reflects dementia severity

To determine whether abnormalities in regional cerebral functional activity estimated by iofetamine hydrochloride I 123 and single photon emission computed tomography can be detected in mild or moderate as well as severe cases of Alzheimer's disease (AD), we performed iofetamine I 123-single photon emission computed tomography in 37 patients with probable AD (nine patients with mild, 18 patients with moderate, and ten patients with severe dementia) and nine age-matched control subjects. Iofetamine I 123 uptake was measured in right and left frontal, temporal, parietal, and occipital cortices. Mean (right and left) iofetamine I 123 activity was lowest in the parietal region of patients with AD and was significantly reduced in the other three regions compared with control subjects. Only in the parietal region was lower relative iofetamine I 123 activity associated with an impaired level of patient function and with cognitive deficit.     

Single photon emission computed tomography using perfusion tracers in seizure disorders.

Single photon emission computed tomography (SPECT) using perfusion tracers makes it possible to estimate regional cerebral blood flow (rCBF) and, indirectly, local brain metabolism. It may be possible to detect and follow physiopathological alterations, such as may be seen in seizure disorders. The authors review the principles of and some data on perfusion SPECT in seizure disorders, stress advantages as well as major drawbacks and add their initial experience with Tc-99m hexamethylpropyleneamine oxime (HMPAO) SPECT in febrile convulsions.     

Single photon emission computed tomography studies of partial epilepsies

Abstract At present, in the field of clinical epilepsy, it has been established that single photon emission computed tomography (SPECT) is useful for the regional determination of epileptic foci. In particular, it seems to be of great advantage to the field of clinical epilepsy that epileptic foci situated in the deep regions of the brain are detectable by the three-dimensional resolution power in SPECT, because such foci are not often represented on routine scalp electroencephalograph (EEG). In reference to our review published previously,¹ recent findings in SPECT studies of partial epilepsies are surveyed here.     

Single photon emission computed tomography with99mTc HM-PAO in the study of focal epilepsy

We used^99mTc HM-PAO SPECT to study 50 patients with partial epilepsy: 47 interically and 3 during a seizure. All 3 patients studied during a seizure presented an area of increased tracer uptake. Of those in whom recordings were taken during seizure-free intervals 35 (74%) showed perfusion asymmetries: 27 (57%) with decreased and 8 (17%) with increased uptake. We discuss the findings and compare them with those of similar studies using SPECT and positron emission tomography.

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Sommario Sono stati studiati mediante SPECT con^99mTc HM-PAO 50 pazienti affetti da epilessia parziale, 47 in fase intercritica e 3 durante la crisi. Tutti i pazienti registrati in fase critica hanno dimostrato un focolaio di iperfissazione del tracciante. Tra quelli registrati in fase intercritica 35 (74%) hanno evidenziato asimmetrie di perfusione di cui 27 (57%) ipofissanti ed 8 (17%) iperfissanti. I risultati sono discussi e confrontati con quelli di analoghi lavori condotti mediante tomoscintigrafia e tomografia a positroni.

     

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.     

A high-resolution single photon emission computed tomography study of verbal recognition memory in Alzheimer's disease

BACKGROUND: In view of the recent technological advances and its ease of availability, we used single photon emission computed tomography (SPECT) to examine the performance of early Alzheimer's disease (AD) subjects on a verbal recognition memory task. METHODS: Eighteen early AD and 10 matched healthy control subjects underwent split-dose (99m)Tc-HMPAO (Ceretec) SPECT using a verbal recognition memory and control task. SPECT images co-registered with MRI scans were used to determine relative regional cerebral blood flow (rCBF) changes in regions of interest. RESULTS: In healthy control subjects, verbal recognition increased rCBF in the right occipital region, thalamus, left prefrontal pole, posterior parietal region and cerebellum, and decreased rCBF in the right hippocampus. AD subjects showed bilateral prefrontal, posterior parietal and occipital increases, unilateral increase in the left posterior temporal region, and bilateral reductions in the hippocampus. Although activation was significantly different between the two groups in the right thalamus and left medial prefrontal region, the verbal recognition task did not enhance discrimination between groups. CONCLUSIONS: Compared with controls, AD subjects activate a similar but more extensive bilateral network during verbal recognition, possibly reflecting an attempt to compensate for impaired processing.     

Single photon emission computed tomography perfusion differences in mild cognitive impairment

Objective

To relate cerebral perfusion abnormalities to subsequent changes in clinical status among patients with mild cognitive impairment (MCI).

Methods

Perfusion single photon emission computed tomography (SPECT) images were acquired in 105 elderly patients without dementia with MCI, using 99mTc‐HMPAO. Clinical outcome after a 5‐year follow‐up period was heterogeneous.

Results

Baseline SPECT data differed in those patients with MCI who were later diagnosed with Alzheimer''s disease (the converter group) from those patients with MCI who experienced clinically evident decline but did not progress to a diagnosis of Alzheimer''s disease within the follow‐up period (the decliner group), from patients with MCI who had no clinical evidence of progression (the stable group), and from a group of 19 normal subjects (the control group). The most consistent decreases in relative perfusion in converters compared with the normal, stable and decliner groups were observed in the caudal anterior cingulate, and in the posterior cingulate. In addition, converters showed increased relative perfusion in the rostral anterior cingulate in comparison to the stable and decliner groups. A group of patients with Alzheimer''s disease were also included for purposes of comparison. The group of patients with Alzheimer''s disease at baseline differed from each of the other groups, with temporoparietal regions showing the most significant reductions in perfusion.

Conclusions

These results suggest that clinical heterogeneity in MCI is reflected in SPECT perfusion differences, and that the pattern of perfusion abnormalities evolves with increasing clinical severity.Regional abnormalities in glucose metabolism and cerebral perfusion are known to occur in patients with a diagnosis of probable Alzheimer''s disease, based on positron emission tomography (PET) and single photon emission computed tomography (SPECT). Decreased metabolism and/or perfusion has been reported primarily in temporoparietal, posterior cingulate and medial temporal regions, and such abnormalities seem to reflect the severity and progression of both clinical impairment and pathological involvement.^1,2,3,4,5Identification of Alzheimer''s disease at the earliest possible time is crucial for optimal care and treatment. Therefore, recent studies have focused on prodromal Alzheimer''s disease. This has been studied by examining baseline PET or SPECT images in patients who are at increased risk for developing Alzheimer''s disease because of mild cognitive impairment, and who then go on to be diagnosed with probable Alzheimer''s disease. Brain regions reported to show metabolism or perfusion abnormalities in those who progress to Alzheimer''s disease have included the temporoparietal neocortex, posterior cingulate, anterior cingulate and medial temporal lobe regions.^{3,6,7,8,9,10,11,12,13,14,15}Few of these studies have compared those patients with MCI who will progress over the next few years to the point where they satisfy the diagnostic criteria for probable Alzheimer''s disease with those who decline to a more limited extent and are not diagnosed with Alzheimer''s disease and with those who remain stable. Only one previous study, to our knowledge, has dealt with this issue.⁸ The authors reported that left temporoparietal reductions in glucose metabolism, in combination with performance on a neuropsychological task (ie, block design), considerably discriminated those people with memory problems who developed Alzheimer''s disease within 3 years from those who remained stable. This study targeted a small number of brain regions for examination, as sample size was limited.We dealt with this question by examining whole brain SPECT datasets using statistical parametric mapping (SPM) in a large number of subjects, some of whom were normal and some of whom had mild cognitive impairments but did not have dementia when the data were acquired. The subjects were then followed longitudinally, and we were able to identify perfusion differences at baseline between subjects who progressed to a diagnosis of Alzheimer''s disease, versus those who remained stable, and those who declined, but were not diagnosed with Alzheimer''s disease during the follow‐up interval. We also determined whether the changes were consistently decreased in cerebral perfusion, or whether increases were also observed, as reported by a recent study.¹⁴ Lastly, we examined the relationship between SPECT perfusion measures and neuropsychological test scores in the same subjects.     

Lack of initiative and interest in Alzheimer's disease: a single photon emission computed tomography study

Apathy is defined as a lack of motivation. The aim of this study was to investigate the relation between two major dimensions of apathy (lack of initiative and lack of interest) and brain perfusion. in patients with Alzheimer's disease (AD). Brain perfusion was measured by single photon emission tomography (SPECT). Thirty-one AD patients were included. Lack of initiative and interest were assessed with the Apathy Inventory. Nineteen AD subjects presented a lack of initiative and interest pathological score whereas 12 AD subjects did not. The lack of initiative and interest score correlated significantly with the right frontal and the right inferior temporal lobes. The AD patients with lack of initiative and interest showed a significantly lower perfusion in the right anterior cingulate than the AD patients without lack of initiative and interest. These results derive from rather small subgroups of patients but have the interest to dismantle the complementary aspects of emotion and motivation in apathy and suggest that the latter one is more related to cingulate area.     

Single photon emission computed tomography (SPECT) in cerebellar disease: cerebello-cerebral diaschisis.

Single photon emission computed tomography assessments were conducted in normal controls (n = 25), patients with unilateral cerebellar infarctions (n = 4), patients with olivopontocerebellar atrophy (OPCA; n = 15) and patients with Friedreich's ataxia (FA; n = 6). In subjects with unilateral cerebellar infarctions, crossed cerebellar-cortical diaschisis was observed: reduced cerebellar hexamethylpropyleneamine oxime (HMPAO) uptake was invariably accompanied by a diminution of HMPAO in the contralateral basal ganglia and frontoparietal cortex. OPCA and FA patients had various degrees of decreased HMPAO uptake in both the cerebellum and cerebral hemispheres.