Biomedical subjects

P Julin

Publications and source records attributed to P Julin.

At least 19 recordsLinked to original sources

PubMed2006

Can dynamic susceptibility contrast magnetic resonance imaging replace single-photon emission computed tomography in the diagnosis of patients with Alzheimer's disease? A pilot study.

PURPOSE: To compare single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) in a cohort of patients examined for suspected dementia, including patients with no objective cognitive impairment (control group), mild cognitive impairment (MCI), and Alzheimer's disease (AD). MATERIAL AND METHODS: Twenty-four patients, eight with AD, 10 with MCI, and six controls were investigated with SPECT using 99mTc-hexamethylpropyleneamine oxime (HMPAO) and dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) with gadobutrol. Three observers performed a visual interpretation of the SPECT and MR images using a four-point visual scale. RESULTS: SPECT was superior to DSC-MRI in differentiating normal from pathological. All three observers showed statistically significant results in discriminating between the control group, AD, and MCI by SPECT, with a P value of 0.0006, 0.04, and 0.01 for each observer. The statistical results were not significant for MR (P values 0.8, 0.1, and 0.2, respectively). CONCLUSION: DSC-MRI could not replace SPECT in the diagnosis of patients with Alzheimer's disease. Several patient- and method-related improvements should be made before this method can be recommended for clinical practice.

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PubMed2001

Evaluation of linear registration algorithms for brain SPECT and the errors due to hypoperfusion lesions.

The semiquantitative analysis of perfusion single-photon emission computed tomography (SPECT) images requires a reproducible, objective method. Automated spatial standardization (registration) of images is a prerequisite to this goal. A source of registration error is the presence of hypoperfusion defects, which was evaluated in this study with simulated lesions. The brain perfusion images measured by 99mTc-HMPAO SPECT from 21 patients with probable Alzheimer's disease and 35 control subjects were retrospectively analyzed. An automatic segmentation method was developed to remove external activity. Three registration methods, robust least squares, normalized mutual information (NMI), and count difference were implemented and the effects of simulated defects were compared. The tested registration methods required segmentation of the cerebrum from external activity, and the automatic and manual methods differed by a three-dimensional displacement of 1.4+/-1.1 mm. NMI registration proved to be least adversely effected by simulated defects with 3 mm average displacement caused by severe defects. The error in quantifying the patient-template parietal ratio due to misregistration was 2.0% for large defects (70% hypoperfusion) and 0.5% for smaller defects (85% hypoperfusion).

Aged↗

PubMed2000

Spatial pattern of cerebral glucose metabolism (PET) correlates with localization of intracerebral EEG-generators in Alzheimer's disease.

BACKGROUND: Since the measurement of human cerebral glucose metabolism (GluM) by positron emission tomography (PET) and that of human cerebral electrical activity by EEG reflect synaptic activity, both methods should be related in their cerebral spatial distribution. Healthy subjects do indeed demonstrate similar metabolic and neuroelectric spatial patterns. OBJECTIVE: The aim of the study was to show that this similarity of GluM and EEG spatial patterns holds true in a population with a high variability of glucose metabolism. METHODS: We investigated healthy control subjects and patients with varying degrees of cognitive dysfunction and varying GluM patterns by applying [18F]FDG PET and EEG. RESULTS: We demonstrated that the localization of intracerebral generators of EEG correlates with spatial indices of GluM. CONCLUSION: These results indicates that EEG provides similar spatial information about brain function as GluM-PET. Since EEG is a non-invasive technique, which is more widely available and can be repeated more often than PET, this may have important implications both for neuropsychiatric research and for clinical diagnosis. However, further studies are required to determine whether equivalent EEG dipole generators can yield a diagnostic specificity and sensitivity similar to that of GluM-PET.

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PubMed2000

Discrimination of Alzheimer's disease and mild cognitive impairment by equivalent EEG sources: a cross-sectional and longitudinal study.

OBJECTIVES: The spatial aspects of brain electrical activity can be assessed by equivalent EEG frequency band generators. We aimed to describe alterations of these EEG generators in Alzheimer's disease (AD) and healthy aging and whether they could serve as predictive markers of AD in subjects at risk. METHODS: The amplitude and 3-dimensional localization of equivalent EEG sources were evaluated using FFT dipole approximation in 38 mild AD patients, 31 subjects with mild cognitive impairment (MCI) and 24 healthy control subjects. RESULTS: AD patients showed an increase of delta and theta global field power (GFP), which corresponds to the generalized EEG amplitude, as well as a reduction of alpha GFP when compared to the controls. A decrease of alpha and beta GFP was found in AD patients, as compared to the MCI subjects. With respect to topography in the antero-posterior direction, sources of alpha and beta activity shifted more anteriorly in AD patients compared to both the controls and MCI subjects. No significant difference was found between MCI and controls. Combined alpha and theta GFP were the best discriminating variables between AD patients and controls (84% correct classification) and AD and MCI subjects (78% correctly classified). MCI subjects were followed longitudinally (25 months on average) in order to compare differences in baseline EEG variables between MCI subjects who progressed to AD (PMCI) and those who remained stable (SMCI). Compared to SMCI, PMCI had decreased alpha GFP and a more anterior localization of sources of theta, alpha and beta frequency. In a linear discriminant analysis applied on baseline values of the two MCI subgroups, the best predictor of future development of AD was found to be antero-posterior localization of alpha frequency. CONCLUSIONS: FFT dipole approximation and frequency analysis performed by conventional FFT showed comparable classification accuracy between the studied groups. We conclude that localization and amplitude of equivalent EEG sources could be promising markers of early AD.

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PubMed2000

Visual rating and volumetry of the medial temporal lobe on magnetic resonance imaging in dementia: a comparative study.

OBJECTIVES: It has been shown that atrophy of medial temporal lobe structures such as the hippocampus and entorhinal cortex shown on MRI may distinguish patients with Alzheimer's disease from healthy controls. However, the diagnostic value of visual inspection and volumetry of medial temporal lobe atrophy (MTA) on MRI in a clinical setting is insufficiently known. METHODS: Medial temporal lobe atrophy in 143 patients was visually rated from hard copies, using a 0-4 rating scale and a comparison was made with the volumes (cm(3)) of the medial temporal lobe as estimated with volumetry, using a stereological method. All patients were recruited in an unselected way in a clinical setting in the centre for memory impairments at the Huddinge University Hospital. Patients with Alzheimer's disease (n=41), patients with other dementias (vascular dementia, frontotemporal dementia, and unspecified dementia; n=36) as well as non-demented subjects (n=66) were included. Medial temporal atrophy and volumetry were evaluated as a diagnostic tool by performing logistic regression analysis including age, sex, and mini mental state examination (MMSE) score and calculating the sensitivity and specificity and percentage correct classification. RESULTS: Visual and volumetric analysis yielded statistically significant differences between patients with Alzheimer's disease and non-demented subjects, as well as between those with other dementias and non-demented subjects. Combining MMSE scores and visually rated MTA ratings yielded a sensitivity of 95% for Alzheimer's disease, 85% for other dementias. Non-demented subjects were identified with a specificity of 96%. Volumetry did not have an added value over the MMSE score alone. CONCLUSIONS: Visual rating of MTA is a clinically useful method for differentiating Alzheimer's disease from controls and is both quicker and more accurate than volumetry.

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PubMed1999

Visual assessment of medical temporal lobe atrophy in demented and healthy control subjects: correlation with volumetry.

The present study evaluated the validity of visual rating of medial temporal lobe atrophy on coronal magnetic resonance imaging scans in a population of demented and non-demented individuals. Medial temporal lobe atrophy in 194 subjects was visually rated from hard copies, using a 0-4 rating scale, and a comparison was made with the absolute volumes (ccm) of the medial temporal lobe as estimated with volumetry, using a stereological method. We found a highly significant correlation between the estimated and stereologically measured volumes. There was a 10-fold difference in time spent on rating medial temporal lobe atrophy (1-2 min) vs. time spent calculating the medial temporal lobe volume (10-12 min) on a single subject. The diagnostic accuracy of both methods showed that visual rating was more efficient than volumetry in differentiating Alzheimer's disease from control subjects, We conclude that visual rating is a reliable and fast method to estimate medial temporal lobe atrophy in demented subjects in a clinical setting.

Adult↗

PubMed1998

EEG slowing and cerebrospinal fluid tau levels in patients with cognitive decline.

We explored the relationship between cerebrospinal fluid (CSF) tau levels as indirect markers of tau-related pathology in Alzheimer's disease (AD) and EEG slowing, a typical neurophysiological finding in the disease. A positive correlation between CSF tau levels and ratio of alpha/delta global field power was found in 14 AD patients (r = 0.65, p = 0.01). This relationship was better approximated by polynomial fit of 2nd degree (p = 0.002). A subgroup of AD patients (n = 7) with higher tau levels and shorter duration of illness showed a strong relationship between CSF tau levels and alpha/theta (r = 0.83, p = 0.02), and alpha/delta (r = 0.87, p = 0.01) ratios of the global field power. There were no significant correlations between EEG slowing and CSF tau levels in 12 patients with mild cognitive dysfunction or in 14 healthy control subjects. That a strong inverse linear correlation exists in AD patients with higher levels of tau and shorter duration of illness may imply that with longer illness duration CSF tau levels decrease due to neuronal death.

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PubMed1998

Brain volumes and regional cerebral blood flow in carriers of the Swedish Alzheimer amyloid protein mutation.

As a preliminary part of a longitudinal clinical study of carriers of the Swedish amyloid precursor protein (APP) 670/671 mutation, 13 members of a family were investigated with magnetic resonance imaging (MRI) brain volumetry and single photon emission computed tomography (SPECT) cerebral blood flow (CBF) measurements. Five of the family members were mutation carriers; eight were not carriers. Two carriers were younger than 40 years of age and had no evidence of cognitive dysfunction or structural or functional brain changes. One carrier with 4 years to expected disease onset showed poor performance in episodic memory tests and also slightly low temporal lobe CBF, although there were no clearly abnormal findings. One carrier with mild Alzheimer disease (AD) had no clear structural brain changes, although CBF measurements showed clear reduction of temporal lobe CBF. One carrier with severe AD had both temporal lobe atrophy and CBF reduction. This indicates that in carriers of the APP 670/671 mutation, reduction of regional CBF is more severe than regional atrophy. The clearest change related to development of clinical AD was a reduction of CBF in the basal and lateral temporal lobes. Further longitudinal studies of these subjects are needed to confirm these preliminary findings, which might provide important data regarding early brain changes in AD.

Adult↗

PubMed1997

Reliability of interactive three-dimensional brain volumetry using MP-RAGE magnetic resonance imaging.

We assessed the reliability of an interactive 3-dimensional methodology for magnetic resonance imaging (MRI) brain tissue segmentation and volumetry using a 3-dimensional magnetization prepared rapid gradient echo pulse sequence (3D MP-RAGE). The methodology was intended to be practically useful to study structural brain changes in larger groups of patients investigated for suspected dementia. The pulse sequence combines volume acquisition, excellent tissue contrast and short patient scan-time. The volumetric method is fully interactive, requiring a minimum of image pre-processing. Ten healthy controls and 10 patients with dementia were included in the study. Six healthy controls were scanned twice. The method is based on thresholding combined with manual tracing in a 3D volume. The 3-dimensional measurement method reduces the measurement time considerably compared to that of slice by slice measurement and permits 3-dimensional display of measured volumes. For different brain regions the intra-study (0.5-1.3%), study-study (1.8-4.7%) and inter-operator (7.1%) variability of this method compared favourably with other manual or automated methods reported. The major advantages of the method are its simplicity and speed, which permits measurement and display of regional brain volumes and tissues in larger patient groups.

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PubMed1997

Bilateral temporal lobe volume reduction parallels cognitive impairment in progressive aphasia.

BACKGROUND: Patients with isolated aphasia in the absence of other cognitive abnormalities have been the focus of several studies during the past decade. It has been called primary progressive aphasia (PPA), and the typical features of this syndrome are marked atrophy of the left temporal lobe according to the radiological examination and a language disorder as the initial symptom. In previous studies of PPA, the selection of the patients was based mainly on linguistic symptoms. Now, when computed tomography or magnetic resonance imaging scans are part of the routine investigation of cognitive impairment and suspected dementia, the patients with lobar atrophy will be found at an earlier stage. In the present study, we used a new approach and defined the study group by selecting patients with obvious left temporal lobe atrophy, assessed by MRI, and we referred to them as patients with temporal lobe atrophy (TLA). OBJECTIVE: To identify the features that distinguish TLA from other primary neurodegenerative disorders. PATIENTS: Six patients with TLA were compared with patients with Alzheimer disease (AD), patients with frontal lobe dementia (FLD), and healthy control subjects. METHODS: The investigations included magnetic resonance imaging volumetry, single photon emission computed tomography, and neuropsychologic and linguistic evaluations. RESULTS: In the TLA group, the mean volume of the left temporal lobe was 35% smaller than the right, while in the AD and FLD groups, the atrophy was symmetrical and bilateral. In the TLA group, the absolute volumes of the temporal lobes were significantly smaller on the left side compared with the AD and FLD groups, whereas there was no difference on the right side. The cerebral blood flow pattern in TLA was asymmetric and differed from that in the other study groups. All patients with TLA had a history of progressive Wernicke-type aphasia, ranging from 2 to 6 years. They showed primary verbal memory impairment but had preserved visuospatial functions. The clinical condition of all patients with TLA deteriorated during the study period; severe aphasia developed, and the patients exhibited signs of frontal lobe dysfunction. Serial volumetric measurements in 4 of 6 patients showed an annual 8% to 9% decrease of both left and right temporal lobes. CONCLUSIONS: The initial marked asymmetry in cognitive function found in patients with TLA contrasts with the general decline found in patients with AD. The bilateral degenerative process evident in patients with TLA paralleled the clinical deterioration, indicating TLA to be a non-AD lobar atrophy that develops into generalized cognitive dysfunction and dementia.

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PubMed1997

EEG-microstates in mild memory impairment and Alzheimer's disease: possible association with disturbed information processing.

The only available functional neuroimaging methods reaching the time resolution of human information processing are EEG and MEG. Since spectral analysis implies analysis of longer time epochs, the high temporal resolution of EEG is partly lost. By dividing the EEG in the time-domain into segments of similar spatial distribution on the scalp (microstates) it has been possible to assess patterns of neuronal activity representing the information process currently performed by the brain. In the present study alterations of EEG microstates in subjective (n = 31) and objective (n = 38) memory impairment as well as in probable Alzheimer disease (DAT: n = 64) compared to healthy controls (n = 21) were investigated. The main findings were reduced segment durations and a more anterior center of gravity of the microstate topography in DAT. With more pronounced cognitive dysfunction larger window sizes were found. Shorter microstates and larger windows reflect more rapidly changing spatial activation patterns, and are interpreted as an impaired capability to establish stable brain states necessary for normal brain function. The anteriorization of the microstates is consistent with results in the frequency domain and may reflect neuropathological changes in DAT.

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PubMed1997

Apolipoprotein E epsilon4 allele decreases functional connectivity in Alzheimer's disease as measured by EEG coherence.

OBJECTIVES: The epsilon4 allele of apolipoprotein E (APOE) represents a major biological risk factor for late onset Alzheimer's disease. However, it is still not known whether the APOE genotype affects the progression of the disease, assessed by different functional methods. METHODS: The study sample included 41 patients with probable Alzheimer's disease. Subjects had similar severity of disease, age of onset, and duration of illness, and were subcategorised according to their APOE genotypes: 17 with no epsilon4 allele, 14 with one epsilon4 allele, and 10 with two epsilon4 alleles. The control group consisted of 18 healthy subjects comparable with the patients in age and education. Analysed quantitative EEG (qEEG) variables were the ratio of alpha and theta absolute power and EEG coherence in alpha frequency band, representing major cortical association pathways. RESULTS: There was pronounced EEG slowing in all three patient subgroups compared with the controls for the alpha/theta ratio, but there was no significant difference across the patient subgroups. Patients homozygous for the APOE epsilon4 allele had reduced right and left temporoparietal, right temporofrontal, and left occipitoparietal coherence. Patients without and with one epsilon4 allele showed an overlap between the control group and group with two epsilon4 alleles in coherence measures. CONCLUSIONS: APOE epsilon4 does not influence EEG slowing, an index which reflects severity of the disease in patients with Alzheimer's disease, but seems to be associated with selective decreases in functional connectivity as assessed by EEG coherence. This finding might be of clinical importance when considering different pathogenetic mechanisms.

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PubMed1997

MRI-guided SPECT measurements of medial temporal lobe blood flow in Alzheimer's disease.

UNLABELLED: In this study, we assessed the accuracy and reliability of MRI-guided SPECT measurements of medial temporal lobe blood flow in Alzheimer's disease (AD). METHODS: Interactively aligned three-dimensional MP-RAGE MRI and 99mTc-HMPAO SPECT images were used for MRI-guided measurement of medial temporal lobe CBF in eight control subjects and eight patients with probable AD. Intraoperator reliability was assessed by repeated alignment and measurement by one experienced operator. Accuracy was assessed by examining two subjects with fiducial markers. RESULTS: The alignment error was less than 1 SPECT pixel size (3.5 mm) and the coefficient of variation in repeated measures of medial temporal-to-cerebellar CBF ratios was 3.2%. The difference in mean medial temporal-to-cerebellar CBF ratios between eight control subjects and eight AD patients was 12%. Also by using three-dimensional seed-grow defined healthy brain reference regions, there were significant differences between control subjects and AD patients in medial temporal blood flow. Furthermore, the volumes of the MRI-defined medial temporal ROIs were smaller in the AD patients. The best separation between AD patients and control subjects was achieved by combining MRI measurements of atrophy and SPECT measurements of CBF. CONCLUSION: These data show that the accuracy and reliability of MRI-guided SPECT measurements of medial temporal CBF clearly allow the detection of changes in AD. Also, a direct comparison of structural and functional changes is possible by this methodology, which might improve the early diagnosis of AD.

Alzheimer Disease↗

PubMed1996

MRI in successful aging, a 5-year follow-up study from the eighth to ninth decade of life.

PURPOSE: This study aimed at evaluate the effect of aging on the central nervous system in "successfully aged" elderly subjects. The brain was studied with magnetic resonance imaging and neuropsychological tests at three different occasions during a time period of 5 yr. MATERIALS AND METHODS: Twenty-four successfully aged elderly were repeatedly examined with cerebral MRI and neuropsychological tests. The first examinations were performed in 1987 and then followed-up in 1989 and 1993. Two different MRI systems were used, in 1987 and 1989, a system operating at 0.02 T and in 1993 a system operating at 0.5 T. Ten subjects (42%) did not participate in the follow-up studies. MRI was used to study the degree of and increase in signal hyperintensities in the cerebrum, the basal ganglia, and in the infratentorial areas as well as changes in the volumes of the cerebro spinal fluid (CSF) spaces. RESULTS: At the start of the study in 1987, mild signal hyperintensities were observed in 11 of the 13 subjects who completed the follow up study. A modest increase in signal hyperintensity was found in almost all of the subjects, with the increases in cerebral white matter and basal ganglia signal hyperintensity being statistically significant (p < .03 and p < .05). The increases in periventricular hyperintensity and the hyperintensity from the infratentorial areas did not reach statistical significance. Volumes of the lateral ventricles and the frontal CSF spaces increased significantly (p < .03 in both cases) during the observation period, whereas the other volumes remained unchanged. The neuropsychological tests were unchanged during the observation period with the exception of the psychomotor capacity, which deteriorated. No statistical significant correlations were seen between the degree of or increase in signal hyperintensities and results from any of the neuropsychological tests. CONCLUSION: During a 5-yr observation of successfully aged elderly it was found that there was a mild increase in signal hyperintensity in the cerebral white matter and basal ganglia, as well as an increase in the frontal and ventricular CSF volumes. These changes were not related to changes in psychometric test results, nor were they related to the clinical outcome during the time of observation.

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PubMed1995

EEG in successful aging; a 5 year follow-up study from the eighth to ninth decade of life.

Fifteen out of 25 successfully aged individuals completed a 5 year EEG follow-up study from the eighth to ninth decade of life with comprehensive neuropsychological investigation. One subject suffered from stroke and one developed symptoms of dementia during the follow-up. Of 13 subjects who completed the follow-up as being healthy, MRI showed subtle enlargement of ventricles or subarachnoid spaces and mild signal hyperintensities in a few regions in 2 subjects. General cognitive decline was not observed (WAIS-R IQ: 113.4 at entry, 114.3 five years later). There were no EEG dominant frequencies below 8 c-sec and no more background slowing than a few theta waves per 10 sec, either at entry or 5 years later. Intermittent slowing was observed in 9 subjects at entry and in 8 subjects 5 years later. The prevalence of intermittent slowing was suggested to increase with advancing age when compared to previous studies with younger elderly. However, intermittent slowing occurred only a few times in an EEG test and lasted for less than 2 sec. Moreover, the presence of intermittent slowing did not correlate with any neuropsychological decline or any MRI change. This type of intermittent slowing was regarded as non-specific and clinically silent.

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PubMed1994

White matter hyperintensities in dementia: does it matter?

The aim of the study was to investigate whether the regional distribution of white matter hyperintensities (WMH) observed by magnetic resonance imaging differed between vascular dementia and patients with late onset Alzheimer's disease. Another aim was to investigate the relations between the occurrence and degree of WMH and clinical and laboratory data as well as measures of cognitive decline. White matter hyperintensities were assessed with a low field magnetic resonance imager on 23 subjects with probable Alzheimer's disease, 25 with possible Alzheimer's disease and 31 subjects with vascular dementia. The degree and regional distribution of the WMH (expressed as relative volumes) were calculated and compared in the three groups. The relation between cognitive impairment and the degree of the WMH was also studied. The regional distribution of the WMH differed between the groups with significantly more changes in the posterior part of the brain (p < .0001) as well as in the right hemisphere (p < .0005) in the vascular demented as compared to the patients with Alzheimer's disease. No significant correlations between cognitive impairment and the degree of the WMH were found in any of the groups. The total volume of the WMH as well as the regional distribution of these changes differed significantly between vascular dementia and Alzheimer's disease. White matter hyperintensities seem not to be related to the degree of global cognitive decline in dementia and whether it plays a causative role in the development of dementia symptoms needs to be more thoroughly investigated.

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PubMed1992

Quantitative estimation of brain white matter abnormalities in elderly subjects using magnetic resonance imaging.

Twenty-five elderly subjects were examined with brain magnetic resonance imaging (MRI). The subjects were divided into two groups: those with Mini-Mental State Examination (MMSE) scores above 25, and those subjects with MMSE scores between 18 and 24. The degree of white matter abnormalities (WMA) (expressed as relative volumes) as well as the presence of cerebrovascular risk factors were evaluated in the two groups. We found that a) subjects with low MMSE scores had significantly larger relative volumes of WMA than the subjects with higher scores, b) a significant correlation (rs = 0.53, p < 0.009) between MMSE scores and the relative volume of WMA was also established, and c) a weak significant correlation (rs = -0.51, p < 0.05) between arterial blood pressure and WMA was found in the subjects with high MMSE scores. Besides these findings no other correlations between the presence of cerebrovascular risk factors and WMA were found in any of the groups.

Aged↗

PubMed1989

Absorbed doses and energy imparted from radiographic examination of velopharyngeal function during speech.

Absorbed doses of radiation were measured by thermoluminescent dosimeters (TLDs) using a skull phantom during simulated cinefluorographic and videofluorographic examination of velopharyngeal function in frontal and lateral projections. Dosages to the thyroid gland, the parotid gland, the pituitary gland, and ocular lens were measured. Radiation dosage was found to be approximately 10 times less for videofluoroscopy when compared with that of cinefluoroscopy. In addition, precautionary measures were found to reduce further the exposure of radiation-sensitive tissues. Head fixation and shielding resulted in dose reduction for both video- and cinefluoroscopy. Pulsing exposure for cinefluoroscopy also reduced the dosage.

Absorption↗