Biomedical subjects

M Teräs

Publications and source records attributed to M Teräs.

At least 19 recordsLinked to original sources

PubMed2005

Non-Gaussian smoothing of low-count transmission scans for PET whole-body studies.

A non-Gaussian smoothing (NGS) technique is developed for filtering low count transmission (TR) data to be used for attenuation correction (AC) of positron emission tomography (PET) studies. The method is based on a statistical technique known as the generalized linear mixed model that allows an inverse link function that avoids the inversion of the observed transmission data. The NGS technique has been implemented in the sinogram domain in one-dimensional mode as angle-by-angle computation. To make it adaptive as a function of the TR count statistics we also develop and validate an objective procedure to choose an optimal smoothing parameter. The technique is assessed using experimental phantoms, simulating PET whole-body studies, and applied to real patient data. Different experimental conditions, in terms of TR scan time (from 1 h to 1 min), covering a wide range of TR counting statistic are considered. The method is evaluated, in terms of mean squared error (MSE), by comparing pixel by pixel the distribution for high counts statistics TR scan (1 h) with the corresponding counts distribution for low count statistics TR scans (e.g., 1 min). The smoothing parameter selection is shown to have high efficiency, meaning that it tends to choose values close to the unknown best value. Furthermore, the counts distribution of emission (EM) images, reconstructed with AC generated using low count TR data (1 min), are within 5% of the corresponding EM images reconstructed with AC generated using the high count statistics TR data (1 h). An application to a real patient whole-body PET study shows the promise of the technique for routine use.

Algorithms↗

PubMed2002

Implementation and evaluation of an ordered subsets reconstruction algorithm for transmission PET studies using median root prior and inter-update median filtering.

An ordered subsets (OS) reconstruction algorithm based on the median root prior (MRP) and inter-update median filtering was implemented for the reconstruction of low count statistics transmission (TR) scans. The OS-MRP-TR algorithm was evaluated using an experimental phantom, simulating positron emission tomography (PET) whole-body (WB) studies, as well as patient data. Various experimental conditions, in terms of TR scan time (from 1 h to 1 min), covering a wide range of TR count statistics were evaluated. The performance of the algorithm was assessed by comparing the mean value of the attenuation coefficient (MVAC) of known tissue types and the coefficient of variation (CV) for low-count TR images, reconstructed with the OS-MRP-TR algorithm, with reference values obtained from high-count TR images reconstructed with a filtered back-projection (FBP) algorithm. The reconstructed OS-MRP-TR images were then used for attenuation correction of the corresponding emission (EM) data. EM images reconstructed with attenuation correction generated by OS-MRP-TR images, of low count statistics, were compared with the EM images corrected for attenuation using reference (high statistics) TR data. In all the experimental situations considered, the OS-MRP-TR algorithm showed: (1) a tendency towards a stable solution in terms of MVAC; (2) a difference in the MVAC of within 5% for a TR scan of 1 min reconstructed with the OS-MRP-TR and a TR scan of 1 h reconstructed with the FBP algorithm; (3) effectiveness in noise reduction, particularly for low count statistics data [using a specific parameter configuration the TR images reconstructed with OS-MRP-TR(1 min) had a lower CV than the corresponding TR images of a 1-h scan reconstructed with the FBP algorithm]; (4) a difference of within 3% between the mean counts in the EM images attenuation corrected using the OS-MRP-TR images of 1 min and the mean counts in the EM images attenuation corrected using the OS-MRP-TR images of 1 h; (5) preservation of "good" image quality for both TR and EM reconstructed images. In conclusion, the OS-MRP-TR algorithm is particularly suitable for WB PET studies, allowing: (1) the acquisition of a very short TR scan (within 1 min), (2) the reconstruction of such TR data in low-noise TR images and (3) the use of the reconstructed OS-MRP-TR images for attenuation correction of corresponding EM data.

Algorithms↗

PubMed2002

PET studies on the memory processing of word pairs in bilingual Finnish-English subjects.

This study examined the fundamental question whether verbal memory processing in two unrelated languages is mediated by a common neural system or by distinct cortical areas. Ten right-handed, male Finnish--English adult late bilinguals who had acquired the second language after the age of 10 were scanned whilst either encoding/retrieving word pairs in their mother tongue (Finnish) or in a foreign language (English). Within each language, subjects had to encode and retrieve four sets of 12 visually presented paired word associates which were not semantically related. Two sets consisted of highly imageable words (e.g. monkey-table; koira-lasi) and the other two sets of abstract word pairs (e.g. freedom-moral; uhka-suure). Presentation of pseudowords served as a reference condition. An emission scan was recorded after each intravenous administration of O-15 water. Encoding was associated with prefrontal and hippocampal activation. During memory retrieval, precuneus showed a consistent activation in both languages and for both highly imageable and abstract words. Although the brain mechanisms of the two languages share common components, differential activations were found in Broca's area and in the cerebellum as well as in the angular/supramarginal gyri according to the language used.

Adult↗

PubMed2001

Perfusion heterogeneity in human skeletal muscle: fractal analysis of PET data.

Muscle blood flow has been shown to be heterogeneous at the voxel by voxel level in positron emission tomography (PET) studies using oxygen-15 labelled water. However, the limited spatial resolution of the imaging device does not allow direct measurement of true vascular flow heterogeneity. Fractal dimension (D) obtained by fractal analysis describes the relationship between the relative dispersion and the size of the region studied, and has been used for the assessment of perfusion heterogeneity in microvascular units. This study was undertaken to evaluate fractal characteristics of PET perfusion data and to estimate perfusion heterogeneity in microvascular units. Skeletal muscle blood flow was measured in healthy subjects using [15O]water PET and the fractal characteristics of blood flow in resting and exercising skeletal muscle were analysed. The perfusion heterogeneity in microvascular units was estimated using the measured heterogeneity (relative dispersion, RD = SD/mean) and D values. Heterogeneity due to methodological factors was estimated with phantoms and subtracted from the flow data. The number of aggregated voxels was inversely correlated with RD both in phantoms (Pearson r = -0.96-0.97) and in muscle (Pearson r = -0.94) when both parameters were expressed using a logarithmic scale. Fractal dimension was similar between exercising (1.13) and resting (1.14) muscles and significantly lower than the values in the phantoms with different activity levels (1.27-1.29). Measured flow heterogeneity values were 20% +/- 6% (exercise) and 27% +/- 5% (rest, P < 0.001), whereas estimated flow heterogeneity values in microvascular units (1 mm3) were 35% +/- 14% (exercise) and 49% +/- 14% (rest, P < 0.01). In conclusion, these results show that it is feasible to apply fractal analysis to PET perfusion data. When microvascular flow heterogeneity is estimated using fractals, perfusion appears to be more heterogeneous in microvascular units than when obtained by routine spatial analysis of PET data. Analysis of flow heterogeneity using PET and fractals could provide new insight into physiological conditions and diseases associated with changes in peripheral vascular function.

Adult↗

PubMed2000

The translating brain: cerebral activation patterns during simultaneous interpreting.

Brain activation was measured in professional interpreters during simultaneous interpreting (SI) vs. repetition (shadowing) of auditorily presented text by positron emission tomography (PET). SI into the native language (Finnish) elicited left frontal activation increases. SI into the non-native language (English) elicited much more extensive left-sided fronto-temporal activation increases. Our results indicate that SI activates predominantly left-hemispheric structures (particularly the left dorsolateral frontal cortex) previously related to lexical search, semantic processing and verbal working memory. Brain activation patterns were clearly modulated by direction of translation, with more extensive activation during translation into the non-native language which is often considered to a be more demanding task.

Adult↗

PubMed2000

Radiotherapy treatment planning and long-term follow-up with [(11)C]methionine PET in patients with low-grade astrocytoma.

PURPOSE: To evaluate the feasibility of [(11)C]-methionine positron emission tomography (MET PET) in radiotherapy (RT) treatment planning and long-term follow-up in patients with low-grade glioma. PATIENTS: Thirteen patients with low-grade astrocytoma and 1 with anaplastic astrocytoma underwent sequential MET PET and magnetic resonance imaging (MRI) before and 3, 6, 12, and 21-39 months after RT, respectively. Ten patients were studied after initial debulking surgery or biopsy and 4 in the recurrence phase. METHODS: A total of 58 PET scans were performed. After transmission scanning, a median dose of 425 MBq of MET was injected intravenously and emission data was acquired 20 min after injection for 20 min. The uptake of MET in tumor area was measured as standardized uptake value (SUV) and tumor-to-contralateral brain SUV ratios were generated to assess irradiation effects on tumor metabolism. Functional imaging with PET was compared with concurrent MRI in designing the RT planning volumes and in assessment of response to RT during a median follow-up time of 33 months. RESULTS: In 12 patients (86%), tumor area was clearly discernible in the baseline PET study. In the remaining 2 patients with a suspected residual tumor in MRI, PET showed only a diffuse uptake of MET interpreted as negative in the original tumor area. In the dose planning of RT, MET PET was helpful in outlining the gross tumor volume in 3 of 11 cases (27%), whereas PET findings either coincided with MRI (46%) or were less distinctive (27%) in other cases. In quantitative evaluation, patients with a low tumor SUV initially had significantly better prognosis than those with a high SUV. Tumor-to-contralateral brain uptake ratios of MET discriminated well patients remaining clinically stable from those who have since relapsed or died of disease. CONCLUSION: Quantitative MET PET has prognostic value at the time of initial treatment planning of low-grade glioma. Some patients may benefit of RT volume definition with MET PET, which seems to disclose residual tumor better than MRI in selected cases. Stable or decreasing uptake of MET in tumor area after RT during follow-up seems to be a favorable sign.

Adult↗

PubMed2000

Nodal staging of lymphoma with whole-body PET: comparison of.

UNLABELLED: Accurate staging is elementary for optimal management of malignant lymphoma. Advanced cases may be curable with multidrug chemotherapy combined with radiotherapy, whereas limited disease can sometimes be cured by local radiotherapy only. Recently, FDG imaging with whole-body PET (WB PET) has been introduced as an accurate method for staging lymphoma. We evaluated the usefulness of L-[methyl-11C]methionine (MET) in comparison with FDG as a tracer for nodal staging of lymphoma with WB PET. METHODS: Nineteen patients with untreated, histologically proven malignant lymphoma underwent WB PET imaging with MET and FDG within 1 wk before treatment. Fourteen patients had non-Hodgkin's lymphoma (NHL), and 5 had Hodgkin's disease (HD). Two of these 19 patients were excluded from the final analysis because of hyperglycemia. WB PET images using FDG and MET were visually compared by 3 independent interpreters, and the PET findings were correlated with the data on the basis of conventional staging studies. RESULTS: Fifty-five of 178 lymph node regions were classified as diseased both by FDG PET and by CT, and 54 of 178 were classified as diseased both by MET PET and by CT. In addition, 11 lymph node regions that CT showed to be normal avidly accumulated FDG. Ten of these lymph node regions also had clear uptake of MET. Another 4 and 5 lymph node regions were enlarged at CT but were judged to be normal by FDG and MET PET, respectively. In nodal staging, both FDG PET and MET PET would have upstaged the disease in 3 patients. MET PET would also have downstaged the disease in 1 patient. CONCLUSION: FDG and MET seem to be comparable in the detection of lymphoma by WB PET. However, visual interpretation of the images tends to be hampered more by physiologic accumulations of MET than by normal accumulations of FDG, and MET may be preferable to FDG in hyperglycemic patients undergoing staging studies with PET.

Adult↗

PubMed1999

Cardiac positron emission tomography imaging with [11C]hydroxyephedrine, a specific tracer for sympathetic nerve endings, and its functional correlates in congestive heart failure.

The integrative mechanisms of autonomic dysfunction in congestive heart failure (CHF) remain poorly understood. We sought to study cardiac retention of [11C]hydroxyephedrine (HED), a specific tracer for sympathetic presynaptic innervation, and its functional correlates in CHF. Thirty patients with mild to moderate heart failure underwent resting cardiac HED positron emission tomography imaging, spectrum analysis testing of systolic pressure and heart rate variability in the resting supine and 70 degrees head-up tilt positions, and testing of baroreflex sensitivity. Compared with control subjects, global myocardial HED retention index was reduced by 30% (p <0.01) in patients with CHF. The HED retention index did not correlate significantly with heart rate variability. However, it correlated with baroreflex sensitivity at rest (r = 0.43, p = 0.05) and with systolic pressure low-frequency (0.03 to 0.15 Hz) variability at head-up tilt (r = 0.76, p <0.01), as well as with low-frequency systolic pressure variability response from baseline to tilt (r = 0.75, p <0.01). We conclude that cardiac HED retention is reduced in patients with CHF. This correlates with blunted vascular sympathetic effector responses during posture-induced reflex activation and baroreflex control of heart rate, suggesting an interdependence between cardiac presynaptic innervation abnormalities and neural mechanisms important to blood pressure maintenance in CHF.

Blood Pressure↗

PubMed1999

Left hemisphere activation during processing of morphologically complex word forms in adults.

Functional neuroanatomy of the processing of morphologically complex words was studied by measuring regional brain activity by positron emission tomography (PET) during encoding of auditorily presented inflected versus monomorphemic Finnish nouns. Significant increases of activation occurred particularly in the left inferior posterior frontal lobe, corresponding to Broca's area. This suggests that besides their role in the production of grammatical morphology documented earlier, Broca's area and adjacent regions are important for the input processing of morphologically complex words.

Adult↗

PubMed1997

Cerebral metabolic rate for glucose after neonatal hypoglycaemia.

OBJECTIVE: We studied the effect of neonatal hypoglycaemia on the local cerebral metabolic rate for glucose (LCMRglc). MATERIALS AND METHODS: Eight newborn infants with neonatal hypoglycaemia were studied. The LCMRglc in the whole brain, in five cerebral regions and in skeletal muscles were quantitated using positron emission tomography (PET) and 2-[18F]Fluoro-2-deoxy-D-glucose (FDG). The PET studies were performed at the age of 5.3 +/- 6.2 days during normoglycaemia. The LCMRglc of these infants were compared to the age-adjusted LCMRglc of eight infants with suspected hypoxic-ischaemic brain injury but with normal neurological development. RESULTS: After neonatal hypoglycaemia the age-adjusted LCMRglc in the whole brain was not lower than LCMRglc of the control infants (5.33 +/- 0.60 mumol/100 g/min vs. 6.71 +/- 0.60 mumol/100 g/min). Also the metabolic rate for glucose (MRglc) in the skeletal muscles was similar in hypoglycaemic and control infants (5.56 +/- 2.48 mumol/100 g/min vs. 6.99 +/- 2.41 mumol/100 g/min). CONCLUSION: MRglc in brain and in skeletal muscle seems to be normal after neonatal hypoglycaemia, although larger group of patients with more severe hypoglycaemia are needed to confirm this finding.

Animals↗

PubMed1997

Quantitative blood flow measurement of skeletal muscle using oxygen-15-water and PET.

UNLABELLED: The aim of the present study was to evaluate quantitation of muscle blood flow using [15O]H2O and PET. METHODS: The autoradiographic (ARG) and the steady-state methods using PET were used to measure femoral muscle blood flow. A simulation study was performed to examine the errors due to contamination of radioactivity in the blood content in muscle tissue, statistical noise and delay and the dispersion of the input curve in the ARG method. Five separate paired muscle blood flow examinations were carried out for comparison of the ARG and the steady-state techniques, including measurement of muscle blood volume in each subject. To obtain the normal range for resting muscle blood flow, additional measurements with the ARG method were performed in 16 normal subjects. RESULTS: When the integration time in ARG was increased to 200-300 sec, the errors due to arterial blood volume, statistical noise, delay and dispersion of the input curve were significantly reduced. Muscle blood flow values in the ARG (200 sec) and the steady-state studies were in good agreement, and each provided an estimated accuracy of 5%. Resting muscle blood flow averaged 3.12 +/- 1.55 ml/min.100 g muscle (range 1.43-6.72 ml/min.100 g muscle, n = 18). CONCLUSION: The ARG and the steady-state methods provided consistent blood flow values for skeletal muscle when a long tissue integration time (> or = 200 sec) was applied in the ARG study. Based on the lower effective radiation dose and the shorter total scan duration, the ARG method is favored over the steady-state method in the measurement of muscle blood flow.

Adult↗

PubMed1997

Transport of carbon-11-methionine is enhanced by insulin.

UNLABELLED: The anabolic effects of insulin are not restricted to carbohydrate and lipid metabolism but also include protein metabolism. However, the effects of insulin on protein metabolism have been difficult to demonstrate in vivo. Amino acid transport is partly regulated by insulin according to the experimental data. PET provides a way to measure fractional uptake rates of amino acids. The purpose of this study was to measure the effect of insulin on amino acid transport from the plasma to the human parotid glands. METHODS: We compared the uptake of L-[methyl-11C]methionine ([11C]methionine) into the parotid glands and cerebellum in seven healthy volunteers during the fasting state and euglycemic insulin clamp technique (1 mU/kg per minute). RESULTS: The fractional uptake rate of [11C]methionine was increased by 31% for the right parotid gland (p = 0.003) and by 29% for the left parotid gland (p = 0.009) during insulin clamp, while the increase was 19% for the cerebellum (p = 0.01). The concentration of amino acids typical for the hormone-sensitive transport system A was 11% lower during insulin infusion than in the fasting state. CONCLUSION: The uptake of methionine into brain tissue does not seem to be under major control by insulin, while the transport of methionine in the parotid glands is stimulated by insulin. PET provides a sophisticated method to study the transport system of amino acids in vivo.

Adult↗

PubMed1996

Relationship between limb and muscle blood flow in man.

1. Since direct measurement of muscle blood flow in humans has been difficult, estimations of muscle flow have been made from measured total limb blood flow using a classic equation that predicts that the fraction of resting blood flow through muscle tissue decreases as total limb flow increases. 2. We used positron emission tomography and 15O-labelled water to directly quantify resting muscle and total limb blood flow in cross-sections of the femoral region in twenty-eight normal subjects (age, 30 +/- 8 years; body mass index, 24.1 +/- 3.3 Kg m-2) under conditions of constant environmental temperature of 22-23 degrees C. 3. Muscle blood flow averaged 3.1 +/- 1.7 ml (100 ml muscle)-1 min-1 (range, 1.1-7.5 ml (100 ml muscle)-1 min-1 and cross-sectional limb blood flow averaged 2.5 +/- 1.1 ml (100 ml limb)-1 min-1) (range, 1.0-4.8 ml (100 ml limb)-1 min-1). A linear relationship was observed between limb and muscle blood flow, and a regression equation was calculated for estimation of muscle blood flow bases on limb flow: muscle flow = (1.41 +/- 0.10) limb flow - (0.43 +/- 0.28). The slope of this equation was significantly greater than 1 (P < 0.001) indicating that the fraction of blood flow perfusing muscle tissue increases as a function of total limb flow. 4. These data provide a new equation for estimation of resting muscle blood flow in normal subjects, and demonstrate that muscle blood flow is the primary determinant of resting blood flow in man.

Adult↗

PubMed1996

Evidence for dissociation of insulin stimulation of blood flow and glucose uptake in human skeletal muscle: studies using [15O]H2O, [18F]fluoro-2-deoxy-D-glucose, and positron emission tomography.

We determined the effect of insulin on muscle blood flow and glucose uptake in humans using [15O]H2O, [18F]fluoro-2-deoxy-D-glucose ([18F]FDG), and positron emission tomography (PET). Femoral muscle blood flow was measured in 14 healthy volunteers (age 34 +/- 8 years, BMI 24.6 +/- 3.4 kg/m2 [means +/- SD]) before and at 75 min during a 140-min high-dose insulin infusion (serum insulin 2,820 +/- 540 pmol/l) under normoglycemic conditions. A dynamic scan of the femoral region was performed using PET for 6 min after injection of [15O]H2O to determine the 15O concentration in tissue. Regional femoral muscle blood flow was calculated using an autoradiographic method from the dynamic data obtained with PET and [15O]H2O. Femoral muscle glucose uptake was measured during hyperinsulinemia immediately after the flow measurement using PET-derived [18F]FDG kinetics and a three-compartment model. Whole-body glucose uptake was quantitated using the euglycemic insulin clamp technique. In the basal state, 84 +/- 8% of blood flow was confined to skeletal muscle. Insulin increased leg blood flow from 29 +/- 14 to 54 +/- 29 ml x kg-1 leg x min-1 (P < 0.001) and muscle flow from 31 +/- 18 to 58 +/- 35 ml x kg-1 muscle x min-1 (P < 0.005). Under insulin-stimulated conditions, 81 +/- 8% of blood flow was in muscle tissue (NS versus basal). Skeletal muscle explained 70 +/- 25% of the increase in leg blood flow. No correlation was observed between blood flow and glucose uptake when analyzed individually in identical regions of interest within femoral muscles. These data demonstrate that skeletal muscle accounts for most of the insulin-induced increase in blood flow. Insulin-stimulated rates of blood flow and glucose uptake do not colocalize in the same regions of muscle tissue, suggesting that insulin's hemodynamic and metabolic effects are differentially regulated.

Adult↗

PubMed1996

Estimated radiation dose to the newborn in FDG-PET studies.

UNLABELLED: The aim of this study was to estimate the radiation dose due to intravenous injection of 2-[18F]fluoro-2-deoxy-D-glucose (FDG) for infants studied with PET. METHODS: The radioactivity concentration in the brain and bladder content was measured with PET to determine the cumulated activity in these organs in 21 infant FDG studies. The individual organ masses were estimated according to the whole-body and brain masses, and they were used to calculate the absorbed dose per unit cumulated activity (S values). For organs other than brain and bladder, the cumulated activity was defined from adult studies. For each individual patient, the absorbed dose to the brain, bladder wall and selected organs were calculated. An estimation of the effective dose was determined. RESULTS: Whole-body distribution of FDG in the infants differed from adults: a greater proportion of the injected activity accumulated into the brain (9% versus 7%) and less was excreted to urine (7% versus 20% respectively). The measured cumulated activity in the brain was 0.25 MBq.h/MBq and in the bladder content 0.04 MBq.h/MBq with a large individual variation in latter. The calculated absorbed dose was 0.24 mGy/MBq to the brain and 1.03 mGy/MBq to the bladder wall. The estimated effective dose was 0.43 mSv/MBq. CONCLUSION: The dose to the bladder wall was lower in infants as compared to adults with ordinary amounts of injected activity. The greater amount of activity remaining in the body may increase the dose to other organs. The effective dose was lower compared to adults and conventional nuclear medicine studies of infants. PET can be a valuable tool in pediatric nuclear medicine because of good resolution images, sensitive radiation measurement and a variety of tracers labeled with short-lived isotopes.

Adult↗

PubMed1995

Evaluation of response to radiotherapy in head and neck cancer by positron emission tomography and [11C]methionine.

PURPOSE: To evaluate the usefulness of positron emission tomography (PET) and L-[methyl-11C]methionine in assessing treatment response to radiotherapy in head and neck cancer. METHODS AND MATERIALS: Fifteen patients with head and neck cancer (13 with squamous cell carcinoma, 1 with adenocystic carcinoma, and 1 with paranasal plasmocytoma) underwent a PET study with [11C]-methionine both before and after preoperative radiotherapy to the total tumor dose of 61-73 Gy. Twelve primary and 12 metastatic tumor sites were within the field of view. Nineteen of the 24 tumor sites were surgically explored after radiotherapy, and the tumor standardized uptake values (SUVs) of [11C]methionine were compared with histological findings. RESULTS: All 24 malignant lesions were detectable in the pretreatment study. In all but one case, the tumor SUV decreased after radiotherapy. The median SUV of the tumor site was smaller (1.9, range, 1.3-3.1, n = 7) in cases with histologically verified complete response than in cases with persistent cancer (median 4.1, range, 2.8-7.6, n = 12, p = 0.0008). A complete histological response was verified in none of the 9 cases with a postirradiation SUV larger than the median (3.1), whereas 7 of the 10 cases with a SUV of 3.1 or smaller had complete response (p = 0.003). The preirradiation uptake of [11C]methionine in tumors did not have significant association with histological response (p = 0.45). The PET findings correlated well with follow-up data in five cases with unoperated tumor sites. The [11C]methionine uptake of the submandibular salivary glands decreased after radiotherapy (p = 0.04). CONCLUSION: PET with [11C]methionine as a tracer may be useful in assessing response to radiotherapy in head and neck cancer. High uptake of [11C]methionine in the postirradiation scan suggests the presence of persistent disease.

Adult↗

PubMed1995

Insulin increases blood volume in human skeletal muscle: studies using [15O]CO and positron emission tomography.

High insulin concentrations increase blood flow in the leg, but it is unknown whether this effect is associated with a change in muscle blood volume. In the present study, we used positron emission tomography combined with inhalation of [15O]carbon monoxide to quantitate the effect of insulin on skeletal muscle blood volume in humans. The reproducibility of the method was determined from two consecutive measurements performed in the basal state in five normal subjects. The coefficient of variation of the repeated measurements was 3.0 +/- 1.8%. In 14 normal subjects [age 35 +/- 3 yr, body mass index 24.9 +/- 1.3 (SE) kg/m2], skeletal muscle blood volume was determined in the femoral region in the basal state and during euglycemic hyperinsulinemia (serum insulin 3,200 +/- 190 pmol/l). The mean muscle blood volume was 3.3 +/- 0.1 ml/0.1 kg muscle in the basal state. Insulin increased muscle blood volume by 9 +/- 2% to 3.6 +/- 0.2 ml/0.1 kg muscle (P < 0.01). The rate of whole body glucose uptake was 53 +/- 6 mumol.kg-1.min-1 and correlated with muscle blood volume during insulin stimulation (r = 0.65, P < 0.02). We conclude that high insulin concentrations exert a true vasodilatory effect in human skeletal muscle.

Adult↗

PubMed1995

Gender and insulin sensitivity in the heart and in skeletal muscles. Studies using positron emission tomography.

Good insulin sensitivity is independently associated with a low risk for coronary heart disease, but it is unclear whether this risk factor differs between men and women. We compared insulin sensitivity of glucose uptake directly in muscle and heart tissues between healthy women (age 29 +/- 2 years, body mass index [BMI] 22 +/- 1 kg/m2, VO2max 39 +/- 4 ml.kg-1.min-1) and men matched for age (31 +/- 2 years), BMI (23 +/- 1 kg/m2), and VO2max (44 +/- 3 ml.kg-1.min-1) using [18F]fluoro-2-deoxy-D-glucose and positron emission tomography under hyperinsulinemic (insulin infusion rate 1 mU.kg-1.min-1) normoglycemic conditions. Whole body insulin sensitivity was 41% greater in women (52 +/- 6 mumol.kg body wt-1.min-1) than in men (37 +/- 3 mumol.kg body wt-1.min-1, P < 0.05). This difference was explained by a 47% greater rate of glucose uptake by femoral muscles (113 +/- 10 vs. 77 +/- 7 mumol.kg muscle-1.min-1, women vs. men, P < 0.01). Insulin-stimulated glucose uptake rates in the heart were similar in women (738 +/- 58) and men (749 +/- 62 mumol.kg muscle-1.min-1). Femoral muscle insulin sensitivity was closely correlated with whole body insulin sensitivity (r = 0.84, P < 0.001). Gender and VO2max together explained 68% of the variation in femoral muscle glucose uptake. We conclude that women are more sensitive to insulin than equally fit men because of enhanced muscle but not heart insulin sensitivity.

Adult↗