Effects of aging on the cerebral distribution of technetium-99m hexamethylpropylene amine oxime in healthy humans

Abstract

Some brain functions decline at a linear rate throughout adulthood. Others remain relatively stable until very late in the life cycle. This study characterized the effects of aging on the regional cerebral distribution of hexamethylpropylene amine oxime (HMPAO) in healthy human volunteers. The sample consisted of 26 men and 18 women with a mean age of 41.6+/-14.9 years (range: 19-73). Their past medical histories, physical examinations, and laboratory screening tests were normal. Single-photon emission tomography (SPET) scans of the brain were performed with a standardized acquisition and processing protocol on a triple-headed camera equipped with fan beam collimators. A 3-D restorative filter and a correction for uniform attenuation were applied before the images were reinterpolated in planes parallel to the line connecting the frontal and occipital poles. Mean counts per pixel were measured in multiple regions of interest (ROIs) within each hemisphere by custom fitting a set of templates to the images. The mean activity in each ROI was compared with the mean activity per pixel in the whole brain. Regression analyses were used to relate the activity ratios to age with both linear and nonlinear models. The relative concentration of radioactivity decreased significantly with age in most, but not all, gray matter structures. It increased in the white matter regions. The nonlinear model of aging fit the data significantly better than a straight line did. Most of the changes with age occurred during young adulthood. No further changes were detectable after the onset of middle age. The median breakpoint age at which the rate of change became negligible was 36.6 years. Aging significantly affects the relative uptake of HMPAO in healthy humans. It decreases in many gray matter regions and increases in most white matter regions. However, the changes do not appear to be linear. Most seem to occur during young adulthood before people reach their late thirties. The distribution then appears to remain relatively stable throughout middle age.

Does Everyday Conversation Contribute to Cognitive Functioning? A Comparison of Brain Activity During Task-Oriented and Life-Worldly Communication Using Near-Infrared Spectroscopy

“…A comparison of mean baseline oxyHb levels by age found levels to be significantly lower for the older adults in eight channels, as supported by studies suggesting that cerebral blood flow declines with age in the gray matter (Mozley et al, 1997), the regions of the inferior frontal gyrus, both sides of the middle frontal gyrus, the left superior temporal gyrus, both sides of the cingulate gyrus (Takahashi et al, 2005), the parietal region, the left frontotemporal cortex, and the temporal cortex (Pagani et al, 2002). Although Takahashi et al (2011) suggested that in the frontal region, blood flow in the scalp accounts for most NIRS signals, even our study found that from the parietal to the frontal region, there was a significant age-related decline in blood flow.…”

Changes in the Heterogeneity of Cerebral Glucose Metabolism with Healthy Aging: Quantitative Assessment by Fractal Analysis

“…Age-related and regionally specific decreases in resting cerebral glucose metabolism and similar age-related declines in CBF and oxygen consumption have been reported in many articles in which modern, highresolution PET scanners were used. [12][13][14][15][16][17][18][19][20][21][22][23] Consistently, the slope of the metabolic decline relative to the age and the degree of difference in metabolism between young and older people varied according to the regions examined. For example, in a recent study in which the effects of healthy aging on the regional cerebral glucose metabolism were assessed with SPM, 23 the bilateral and symmet- rically distributed effects of age were most marked in the inferior and posterior lateral frontal, anterior cingulate, perisylvian temporoparietal and anterior temporal cortices, left caudate head, and anterior thalamus.…”

“…9 However, proper assessment of elderly patients with neurodegenerative diseases, such as Alzheimer's disease, requires knowledge about the effects of aging. There have been many reports showing age-and/or gender-related effects on the regional CBF, [12][13][14] glucose metabolism, [15][16][17][18][19][20][21][22][23] and several neuroreceptor systems. [24][25][26] Usually, those effects are regionally specific.…”

A new automated method for analysis of rCBF‐SPECT images based on the active‐shape algorithm: normal values

“…The reason that we only found weak age-related changes can be that our study group was older than in these studies. Mozley et al (1997) showed that most of age-related changes occur during young adulthood. They found that the rate of change became negligible after 36 years of age, i.e.…”