Biomedical subjects

U Ruotsalainen

Publications and source records attributed to U Ruotsalainen.

At least 37 records · Page 2Linked to original sources

PubMed1998

Insulin resistance in essential hypertension is characterized by impaired insulin stimulation of blood flow in skeletal muscle.

OBJECTIVE: To determine whether insulin-stimulated blood flow in patients with mild essential hypertension is altered. SUBJECTS: Eleven untreated mildly hypertensive patients [aged 35 +/- 2 years, body mass index 25.1 +/- 0.4 kg/m2, mean arterial pressure 110 +/- 2 mmHg (means +/- SEM) and 10 matched normotensive subjects (mean arterial pressure 94 +/- 3 mmHg). METHODS: Blood flow was quantitated directly in skeletal muscle both basally and during supraphysiologic hyperinsulinemia (serum insulin approximately = 450 mU/l) using radiowater ([15O]H2O) and positron emission tomography. Whole-body and femoral muscle glucose uptakes were determined using the euglycemic insulin clamp technique, [18F]-2-fluoro-2-deoxy-D-glucose and positron emission tomography. RESULTS: Rates of whole-body and femoral muscle glucose uptake were significantly lower in the hypertensive than in the normotensive group. Insulin increased muscle blood flow by 91% in the normotensive group, but only by 33% in the hypertensive group. CONCLUSIONS: The ability of insulin to stimulate blood flow in patients with mild essential hypertension is impaired.

Adult↗

PubMed1997

Intact insulin stimulation of skeletal muscle blood flow, its heterogeneity and redistribution, but not of glucose uptake in non-insulin-dependent diabetes mellitus.

We tested the hypothesis that defects in insulin stimulation of skeletal muscle blood flow, flow dispersion, and coupling between flow and glucose uptake contribute to insulin resistance of glucose uptake in non-insulin-dependent diabetes mellitus (NIDDM). We used positron emission tomography combined with [15O]H2O and [18F]-2-deoxy--glucose and a Bayesian iterative reconstruction algorithm to quantitate mean muscle blood flow, flow heterogeneity, and their relationship to glucose uptake under normoglycemic hyperinsulinemic conditions in 10 men with NIDDM (HbA1c 8.1+/-0.5%, age 43+/-2 yr, BMI 27.3+/-0.7 kg/m2) and in 7 matched normal men. In patients with NIDDM, rates of whole body (35+/-3 vs. 44+/-3 micromol/kg body weight.min, P < 0.05) and femoral muscle (71+/-6 vs. 96+/-7 micromol/kg muscle.min, P < 0.02) glucose uptake were significantly decreased. Insulin increased mean muscle blood flow similarly in both groups, from 1.9+/-0.3 to 2.8+/-0.4 ml/100 g muscle.min in the patients with NIDDM, P < 0.01, and from 2.3+/-0.3 to 3.0+/-0.3 ml/100 g muscle.min in the normal subjects, P < 0.02. Pixel-by-pixel analysis of flow images revealed marked spatial heterogeneity of blood flow. In both groups, insulin increased absolute but not relative dispersion of flow, and insulin-stimulated but not basal blood flow colocalized with glucose uptake. These data provide the first evidence for physiological flow heterogeneity in human skeletal muscle, and demonstrate that insulin increases absolute but not relative dispersion of flow. Furthermore, insulin redirects flow to areas where it stimulates glucose uptake. In patients with NIDDM, these novel actions of insulin are intact, implying that muscle insulin resistance can be attributed to impaired cellular glucose uptake.

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

Bayesian image reconstruction for emission tomography based on median root prior.

The aim of the present study was to investigate a new type of Bayesian one-step late reconstruction method which utilizes a median root prior (MRP). The method favours images which have locally monotonous radioactivity concentrations. The new reconstruction algorithm was applied to ideal simulated data, phantom data and some patient examinations with PET. The same projection data were reconstructed with filtered back-projection (FBP) and maximum likelihood-expectation maximization (ML-EM) methods for comparison. The MRP method provided good-quality images with a similar resolution to the FBP method with a ramp filter, and at the same time the noise properties were as good as with Hann-filtered FBP images. The typical artefacts seen in FBP reconstructed images outside of the object were completely removed, as was the grainy noise inside the object. Quantitatively, the resulting average regional radioactivity concentrations in a large region of interest in images produced by the MRP method corresponded to the FBP and ML-EM results but at the pixel by pixel level the MRP method proved to be the most accurate of the tested methods. In contrast to other iterative reconstruction methods, e.g. ML-EM, the MRP method was not sensitive to the number of iterations nor to the adjustment of reconstruction parameters. Only the Bayesian parameter beta had to be set. The proposed MRP method is much more simple to calculate than the methods described previously, both with regard to the parameter settings and in terms of general use. The new MRP reconstruction method was shown to produce high-quality quantitative emission images with only one parameter setting in addition to the number of iterations.

Algorithms↗

PubMed1997

Acute effects of celiprolol on muscle blood flow and insulin sensitivity: studies using [15O]-water, [18F]-fluorodeoxyglucose and positron emission tomography.

OBJECTIVE: Recently the role of peripheral vasoconstriction in the aetiology of insulin resistance has been proposed. Celiprolol is a beta 1-selective adrenoceptor antagonist with partial agonist activity at the beta 2-receptor as well as vasodilator properties. The acute effects of celiprolol on skeletal muscle blood flow and insulin sensitivity were measured in this study. METHODS: Celiprolol (2 times 0.5 mg.kg-1) or saline was given intravenously to five healthy males in random order. Muscle blood flow was measured in femoral regions using [15O]-labelled water and positron emission tomography (PET) during euglycaemic hyperinsulinaemia (serum insulin approximately 65 mU.1(-1)) after an overnight fast. Thereafter, skeletal and heart muscle glucose uptake were determined using [18F]-2-deoxy-D-glucose. RESULTS: Celiprolol increased muscle blood flow by 74%, from 3.4 to 5.9 ml.min-1.100 g-1 muscle in the basal state. It decreased peripheral resistance by 40%, from 32.0 to 19.2 mmHg.ml-1.min-1.100 g-1. Celiprolol significantly decreased diastolic blood pressure from 82 to 73 mmHg and increased heart rate from 61 to 68 beats.min-1, which suggests sympathetic activation. Insulin-stimulated glucose uptake was reduced by 46% in the whole body, from 39 to 21 mumol.kg-1.min-1 and by 59% in the femoral muscles, from 99 to 41 mumol.kg-1.min-1, with celiprolol as compared to saline. The effect on heart glucose uptake did not statistically differ between the treatments. CONCLUSION: Celiprolol given intravenously increased muscle blood flow and decreased peripheral resistance at rest. It also acutely increased heart rate probably via sympathetic activation, and decreased insulin sensitivity in the muscles of healthy male volunteers. The enhanced muscle perfusion when celiprolol is given intravenously does not explain the improved insulin sensitivity seen in the long-term oral use in dyslipidaemic hypertensive patients.

Adrenergic beta-1 Receptor Antagonists↗

PubMed1997

Comparison of [18F]FDG-PET, [99mTc]-HMPAO-SPECT, and [123I]-iomazenil-SPECT in localising the epileptogenic cortex.

OBJECTIVES: Firstly, to compare the findings of interictal 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and of single photon emission computed tomography (SPECT) using 99mTc-hexamethyl propylene-amine-oxime (HMPAO) and 123I-iomazenil in localising the epileptogenic cortex in patients who were candidates for epilepsy surgery, but in whom clinical findings, video EEG monitoring (V-EEG), MRI, and neuropsychological evaluations did not give any definite localisation of the seizure onset. Secondly, to assess the ability of these functional methods to help in the decision about the epilepsy surgery. METHODS: Eighteen epileptic patients were studied with FDG-PET and iomazenil-SPECT. HMPAO-SPECT was performed in 11 of these 18 patients. Two references for localisation was used--ictal subdural EEG recordings (S-EEG) and the operated region. RESULTS: Fifteen of 18 patients had localising findings in S-EEG. FDG-PET findings were in accordance with the references in 13 patients and iomazenil-SPECT in nine patients. HMPAO-SPECT visualised the focus less accurately than the two other methods. In three patients S-EEG showed independent bitemporal seizure onset. In these patients FDG-PET showed no lateralisation. However, iomazenil-SPECT showed temporal lobe lateralisation in two of them. CONCLUSION: FDG-PET seemed to localise the epileptogenic cortex more accurately than interictal iomazenil-SPECT in patients with complicated focal epilepsy.

Adolescent↗

PubMed1997

Effects of insulin on blood flow and volume in skeletal muscle of patients with IDDM: studies using [15O]H2O, [15O]CO, and positron emission tomography.

Exaggerated vasoconstriction and blunted vasodilation of peripheral resistance arteries to various vasoactive agents characterize patients with IDDM. We characterized the hemodynamic effects of insulin in skeletal muscle in patients with IDDM. Muscle blood flow and blood volume were measured basally and during a high-dose insulin infusion (5 mU x kg(-1) x min[-1]) in seven normotensive patients with IDDM (age, 30 +/- 6 years; BMI, 24.5 +/- 2.0 kg/m2; blood pressure, 124 +/- 12/78 +/- 11 mmHg) and nine matched normal subjects, using [15O]H2O, [15O]CO, and positron emission tomography (PET). Whole-body insulin sensitivity was determined using the euglycemic insulin clamp technique. Insulin-stimulated whole-body glucose uptake was significantly lower in the patients with IDDM (45 +/- 15 micromol x kg(-1) x min[-1]) than in the normal subjects (62 +/- 14 micromol x kg(-1) x min[-1]) (P < 0.05). Insulin increased muscle blood flow by 111 +/- 69% above basal from 3.0 +/- 2.0 to 5.8 +/- 3.0 ml x 100 g(-1) muscle x min(-1) (P < 0.005) in the normal subjects, but only by 42 +/- 30% from 2.0 +/- 0.9 to 2.9 +/- 1.4 ml x 100 g(-1) muscle x min(-1) (P < 0.005) in patients with IDDM (P < 0.05 for change in flow in IDDM vs. normal subjects). The calculated muscle vascular resistances were comparable basally, but higher during hyperinsulinemia in the patients with IDDM (37 +/- 17 mmHg x 100 g x min x ml[-1]) than in the normal subjects (16 +/- 7 mmHg x 100 g x min x ml[-l]) (P < 0.05). Muscle blood volume increased significantly by insulin in both groups without any difference between the groups. We conclude that the ability of supraphysiological concentrations of insulin to stimulate muscle blood flow is blunted in patients with IDDM, because of the inability of insulin to stimulate linear flow velocity rather than blood volume in skeletal muscle. This defect adds yet another defect to the list of abnormalities in vascular function in IDDM, which might predispose these patients to develop hypertension.

Adult↗

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

Glucose uptake in the chronically dysfunctional but viable myocardium.

BACKGROUND: The regulation of glucose uptake in the dysfunctional but viable myocardium has not been studied previously in humans. METHODS AND RESULTS: Seven patients with an occluded major coronary artery but no previous infarction were studied twice with 2-[(18)F]fluoro-2-deoxy-D-glucose positron emission tomography, once in the fasting state and once during hyperinsulinemic euglycemic clamping. Myocardial blood flow was measured with [(15)O]H2O. The myocardial region beyond an occluded artery that showed stable wall-motion abnormality represented chronically dysfunctional but viable tissue. Six of the patients were later revascularized, and wall-motion recovery was detected in the corresponding regions, which confirmed viability. A slightly reduced myocardial blood flow was detected in the dysfunctional than in the remote myocardial regions (0.81 +/- 0.27 versus 1.02 +/- 0.23 mL x g(-1) x min(-1),P=.036). In the fasting state, glucose uptake was slightly increased in the dysfunctional regions compared with normal myocardium (15 +/- 10 versus 11 +/- 10 micromol/100 g per minute, P=.038). During insulin clamping, a striking increase in glucose uptake by insulin was obtained in both the dysfunctional and the normal regions (72 +/- 22 and 79 +/- 21 micromol/100 g per minute, respectively; P<.001, fasting versus clamping). CONCLUSIONS: Contrary to previous suggestions, glucose uptake can be increased strikingly by insulin in chronically dysfunctional but viable myocardium. This demonstrates that insulin control over glucose uptake is preserved in the dysfunctional myocardium and provides a rational basis for metabolic intervention.

Aged↗

PubMed1996

Role of blood flow in regulating insulin-stimulated glucose uptake in humans. Studies using bradykinin, [15O]water, and [18F]fluoro-deoxy-glucose and positron emission tomography.

Defects in insulin stimulation of blood flow have been used suggested to contribute to insulin resistance. To directly test whether glucose uptake can be altered by changing blood flow, we infused bradykinin (27 microgram over 100 min), an endothelium-dependent vasodilator, into the femoral artery of 12 normal subjects (age 25+/-1 yr, body mass index 22+/-1 kg/m2) after an overnight fast (n = 5) and during normoglycemic hyperinsulinemic (n = 7) conditions (serum insulin 465+/-11 pmol/liter, 0-100 min). Blood flow was measured simultaneously in both femoral regions using [15O]-labeled water ([15O]H2O) and positron emission tomography (PET), before and during (50 min) the bradykinin infusion. Glucose uptake was measured immediately after the blood flow measurement simultaneously in both femoral regions using [18F]-fluoro-deoxy-glucose ([18F]FDG) and PET. During hyperinsulinemia, muscle blood flow was 58% higher in the bradykinin-infused (38+/-9 ml/kg muscle x min) than in the control leg (24+/-5, P<0.01). Femoral muscle glucose uptake was identical in both legs (60.6+/-9.5 vs. 58.7+/-9.0 micromol/kg x min, bradykinin-infused vs control leg, NS). Glucose extraction by skeletal muscle was 44% higher in the control (2.6+/-0.2 mmol/liter) than the bradykinin-infused leg (1.8+/-0.2 mmol/liter, P<0.01). When bradykinin was infused in the basal state, flow was 98% higher in the bradykinin-infused (58+/-12 ml/kg muscle x min) than the control leg (28+/-6 ml/kg muscle x min, P<0.01) but rates of muscle glucose uptake were identical in both legs (10.1+/-0.9 vs. 10.6+/-0.8 micromol/kg x min). We conclude that bradykinin increases skeletal muscle blood flow but not muscle glucose uptake in vivo. These data provide direct evidence against the hypothesis that blood flow is an independent regulator of insulin-stimulated glucose uptake in humans.

Adult↗

PubMed1996

CT, MRI, and PET in a case of intractable epilepsy.

We report the case of a child with drug-refractory partial epilepsy in whom computed tomography showed no abnormality and magnetic resonance imaging showed a noninvasive cystic lesion in the left hippocampus. The finding in the positron emission tomography study with L-[methyl-11C]-methionine as a tracer suggested a tumor. This finding was confirmed histologically.

Brain Neoplasms↗

PubMed1996

Striatal dopamine D1 receptors in narcolepsy: a PET study with [11C]NNC 756.

We investigated dopamine D1 receptors in the putamen and caudate nucleus with positron emission tomography in six patients with narcolepsy and five healthy controls using [11C]NNC 756 as ligand. The caudate-to-cerebellum and putamen-to-cerebellum ratios of [11C]NNC 756 were within normal limits in patients with narcolepsy. No evidence of increased D1 receptor binding in narcolepsy was found.

Adult↗

PubMed1996

Cerebral metabolic rate for glucose during the first six months of life: an FDG positron emission tomography study.

AIM: To measure the local cerebral metabolic rate for glucose (LCMRGlc) in neonatal brains during maturation using positron emission tomography (PET) and 2-[18F]fluoro-2-deoxy-D-glucose (FDG). METHODS: Twenty infants were studied using PET during the neonatal period. The postconceptional age ranged from 32.7 to 60.3 weeks. All infants had normal neurodevelopment and were normoglycaemic. The development of the infants was carefully evaluated (follow up 12-36 months) clinically, and by using a method based on Gesell Amatruda's developmental diagnosis. LCMRGlc was quantitated using PET derived from FDG kinetics and calculated in the whole brain and for regional brain structures. RESULTS: LCMRGlc for various cortical brain regions and the basal ganglia was low at birth (from 4 to 16 mumol/100 g/minute). In infants 2 months of age and younger LCMRGlc was highest in the sensorimotor cortex, thalamus, and brain stem. By 5 months, LCMRGlc had increased in the frontal, parietal, temporal, occipital and cerebellar cortical regions. In general, the whole brain LCMRGlc correlated with postconceptional age (r = 0.90; P < 0.001). The change in the glucose metabolic pattern observed in the neonatal brain reflects the functional maturation of these brain regions. CONCLUSION: These findings show that LCMRGlc in infants increases with maturation. Accordingly, when LCMRGlc is measured during infancy, the postconceptional age has to be taken into account when interpretating the results.

Age Factors↗

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

Increased glucose metabolism in untreated non-Hodgkin's lymphoma: a study with positron emission tomography and fluorine-18-fluorodeoxyglucose.

Glucose metabolism has been shown to be increased in neoplastic tissue. It has been suggested that high activity of glucose metabolism is associated with a high grade of malignancy of human cancer. We studied in vivo glucose metabolism in 22 patients with untreated non-Hodgkin's lymphoma with fluorine-18-fluorodeoxyglucose (FDG) and positron emission tomography (PET). FDG uptake in lymphoma deposits was measured blinded to clinical data, and compared with histologic classification and proliferative activity. Tracer uptake was measured by using two indices of FDG accumulation: the standardized uptake value (SUV) and the regional metabolic rate (rMR) for the tracer. The median SUV of the lymphomas was 8.5 (range, 3.5 to 31.0), and the median rMR 22.7 mumol/100 g/min (range, 9.0 to 124.3 mumol/100 g/min). A high FDG uptake in tumors was associated with high histologic degree of malignancy as defined by the Working Formulation (P = .005 for the SUV, and P = .04 for the rMR) or by the Kiel classification (P = .003 for the SUV, and P = .02 for the rMR). A high FDG accumulation was also associated with a high S-phase fraction (r = .786 for the SUV, P = .0002; and r = .774 for the rMR, P = .02). We conclude that in untreated non-Hodgkin's lymphomas high FDG uptake is associated with high histologic grade of malignancy and a high proliferation rate. This minimally invasive method may find application in assessing lymphoma lesions in patients who are poor candidates for surgery, and it may provide further information in cases where the grade of aggressiveness of lymphoma is not settled based on clinical or histologic data.

Adult↗