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Biomedical subjects

A Ahonen

Publications and source records attributed to A Ahonen.

At least 19 recordsLinked to original sources
PubMed1992

Euglycemic hyperinsulinemic clamp and oral glucose load in stimulating myocardial glucose utilization during positron emission tomography.

To enable assessment of myocardial viability, myocardial glucose utilization has commonly been stimulated by oral glucose loading. To compare the effects of glucose loading and insulin and glucose infusion (insulin clamp) on PET fluorodeoxyglucose ([18F]FDG) myocardial scan image quality and regional myocardial glucose utilization rate (rMGU), eight patients with angiographically documented coronary artery disease and previous myocardial Q-wave infarction were studied twice, once during insulin clamp and once 1 hr after oral glucose loading. The rMGU rates were derived by graphic Patlak analysis in 33 normal, 10 scar and 6 "hot spot" myocardial segments. Infusion of insulin and glucose gave stable plasma-glucose and serum-insulin levels during imaging. In contrast, glucose loading caused marked changes in plasma-glucose and insulin concentrations. The image quality was clearly superior and the fractional utilization rates of [18F]FDG were twice as high during insulin clamp than after glucose loading (p less than 0.0001). Due to the higher plasma-glucose levels after glucose loading, the calculated rMGU in normal, scar and hot spot myocardial segments was comparable between the two protocols. The insulin clamp technique makes it possible to adjust and maintain a metabolic steady state during the PET study. It does not alter [18F]FDG uptake patterns in different myocardial areas when compared to the standard glucose loading protocol, but this technique results in superior image quality and permits the use of smaller [18F] FDG patient doses.

Administration, Oral↗
PubMed1991

Auditory evoked magnetic fields after ischemic brain lesions.

Auditory evoked magnetic fields to noise/square-wave sequences, presented once every 2.2 seconds, were recorded in 8 patients who had ischemic lesions in the auditory cortex or in its vicinity. In 2 patients with large temporoparietal lesions, the magnetic 100-msec deflection (N100m) was absent over the damaged side. In 1 patient with a large but less deep frontotemporal lesion, a small N100m could be discerned on the defective side. Frontal lesions or small lesions in the vicinity of the supratemporal plane had no effect on N100m. Auditory evoked magnetic field recordings may be useful in clinical studies of auditory cortical functions.

Adolescent↗
PubMed1991

Radiation effects on uptake of 99Tcm-hexamethylpropylen amine oxime (HMPAO) in head and neck tumours.

Twenty patients with malignant head and neck tumours were imaged with 99Tcm-labelled hexamethylpropylene amine oxime (HMPAO), a radiopharmaceutical generally used for blood flow studies. Before radiotherapy (RT), 93% of the tumours could be detected with single photon emission computed tomography (SPECT) and 45% with planar imaging. Whole tumour-to-background 99TcmHMPAO uptake ratios ranged from 3.6 to 1.0 (mean 1.7 +/- 0.6) in untreated tumours. There was a good correlation between tumour volume and uptake (r = 0.69, P = 0.002). Sixteen patients were reimaged during or shortly after radical RT. 99TcmHMPAO uptake was significantly lower after treatment (mean uptake ratio 1.2 +/- 0.3, P less than 0.001). However, RT associated changes in 99TcmHMPAO uptake were in agreement with the clinical response in only 63% of the studies. This study indicates that 99TcmHMPAO SPECT imaging can be used for pretherapeutic localisation of head and neck tumours. Although most tumours show a decrease in uptake after irradiation the poor association with tumour regression does not allow for reliable assessment of treatment response.

Adult↗
PubMed1991

Inhaled bronchodilator's in asthma: low or high dose?

We studied the effect of regular inhalations of low-dose and high-dose fenoterol and low-dose and high-dose combinations of fenoterol and ipratropium bromide in maintenance treatment of 120 adults with moderately severe asthma. We used a double-blind, randomized, parallel group design comparing 12 weeks of treatment with four regimens: fenoterol, 100 micrograms/dose; fenoterol, 200 micrograms/dose; fenoterol, 50 micrograms; and ipratropium, 20 micrograms/dose in a single inhaler (Berodual) and fenoterol, 100 micrograms and ipratropium, 40 micrograms/dose in a single inhaler (Duovent). During the baseline and active treatment period the patients recorded PEFR in the morning and evening, symptoms and use of a rescue inhaler. Changes in twice daily peak expiratory flow rates or asthma symptoms did not show any significant differences among the four treatment regimens during the 12 weeks compared with the baseline period. Use of the rescue inhaler did not differ among the four groups during the active treatment. The patients' assessment of the efficacy of the active treatment favored the low-dose fenoterol and low-dose combination. More side effects were recorded in the high-dose combination group during the first 4 weeks compared with the other groups. We conclude that in maintenance therapy of chronic asthma high doses of fenoterol alone or in combination with ipratropium bromide offer no clinical advantage over low doses. On the contrary, the low-dose fenoterol and the low-dose combination are better accepted and tolerated by the patients.

Administration, Inhalation↗
PubMed1990

Effects of captopril on blood pressure and respiratory function compared to verapamil in patients with hypertension and asthma.

Seventeen adult patients with moderate and stable bronchial asthma and established essential hypertension (WHO I or II) were evaluated in a randomized, double-blind, crossover study of the effects of captopril (50-100 mg/day) and verapamil (160-240 mg/day) on blood pressure, orthostatic reactions, respiratory function, and asthmatic symptoms. The effect of both drugs on blood pressure was significant. Blood pressure (mean of 161/98 mm Hg initially) decreased to a mean of 147/90 and 160/91 mm Hg on captopril and verapamil, respectively, with normal orthostatic changes. There were no significant differences in forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), maximal expiratory flow at 50% of FVC (MEF50), or peak expiratory flow (PEF) measurements at the end of each treatment period. The subjective severity of asthma did not change significantly during the trial. No significant cough symptoms were reported on captopril.

Aged↗
PubMed1989

F-18 fluorodeoxyglucose: its potential in differentiating between stress fracture and neoplasia.

F-18 fluorodeoxyglucose (FDG) accumulates into regions of enhanced glucose uptake and metabolism such as the brain, heart, and malignant tumors. The clinical usefulness of this positron-emitting radiopharmaceutical is illustrated in a case where the clinical picture and CT indicated a malignant bone lesion in the clavicle. Histologically a stress fracture was found secondary to chronic strain on the clavicle. On follow-up the lesion's course was benign. Planar imaging with F-18 FDG was performed twice during follow-up, and on both occasions there was no accumulation of radioactivity over the suspicious area, indicating normal glucose consumption. This case demonstrates the differential diagnostic potential of F-18 FDG and shows that clinically useful information may be obtained without a position emission tomograph.

Adolescent↗
PubMed1989

Psychosocial effects of continuous oxygen therapy in hypoxaemic chronic obstructive pulmonary disease patients.

Twenty six hypoxaemic patients with severe and stable chronic obstructive pulmonary disease (COPD) were treated with continuous domiciliary oxygen for a six month period. The patients were evaluated 1, 3 and 6 months after the start of oxygen therapy. In addition to blood gas analysis, 15 coping skills were evaluated by the patient and by the nurse, who also rated the general activity of the patients. Depression was measured by Beck Depression Inventory (BDI) at the start of the trial and after six months' oxygen therapy. The general psychosocial response was meagre; no significant changes were observed in any psychosocial measures. The response was slightly better in younger and less hypoxaemic patients. We conclude that the psychosocial response to oxygen therapy in severely hypoxaemic COPD patients is limited.

Adaptation, Psychological↗
PubMed1988

Fluorodeoxyglucose imaging: a method to assess the proliferative activity of human cancer in vivo. Comparison with DNA flow cytometry in head and neck tumors.

Thirteen patients with malignant head and neck tumors were studied before they were treated with (18F) fluorodeoxyglucose (FDG) imaging and DNA flow cytometry (FCM). The nuclear DNA content and the percentage of proliferative cells (S + G2/M) were compared with the FDG uptake; FDG was retained in the primary tumor and/or neck metastasis in all patients. The accumulation of FDG did not correlate with histologic grade of the tumors, but there was a clear correlation (r = 0.86, P less than 0.001) between the proportion of the cells in S + G2/M phases of the cell cycle and the intensity of FDG accumulation. The uptake of FDG by the tumor also correlated with the percentage of S-phase cells (r = 0.82, P less than 0.001). The result suggests that enhanced glucose metabolism, measured by FDG uptake, is associated with the proliferative activity of the tumor. Thus, imaging with FDG may offer a new method to assess the aggressiveness of human cancer growth in vivo.

Aneuploidy↗
PubMed1988

18F-fluorodeoxyglucose imaging in preoperative diagnosis of thyroid malignancy.

Fourteen human thyroid tumors were studied with 18F-fluorodeoxyglucose (FDG) imaging. The proliferative activity and DNA ploidy of the tumors was assessed by DNA flow cytometry. FDG accumulated in a Hürthle cell carcinoma, an anaplastic carcinoma and a thyroid lymphoma, but only slightly or not at all in the three papillary carcinomas studied. Three of the eight benign tumors also accumulated FDG, but two of these were selected for imaging because of a large number of proliferating cells in DNA flow cytometry. Two carcinomas with increased nuclear DNA content retained FDG, but a histologically benign follicular adenoma with DNA aneuploidy did not. We conclude that in addition to malignant thyroid tumors, histologically benign tumors may also accumulate FDG, and therefore the value of FDG scanning in the preoperative diagnosis of thyroid malignancy is limited.

Adenoma↗
PubMed1988

Evaluation of treatment response to radiotherapy in head and neck cancer with fluorine-18 fluorodeoxyglucose.

Nineteen patients with malignant head and neck tumors were imaged before and during radiation therapy with 18F-2-fluoro-2-deoxy-D-glucose (FDG) to study the effect of radiotherapy (RT) on FDG uptake. All tumor images were FDG-positive before treatment. After RT, a decrement of tumor FDG uptake was found in all but two patients; these were nonradioresponders. There was a significant decrement (p less than 0.001) in uptake ratios after irradiation of 30 +/- 5 Gy among the radioresponsive (CR + PR) but not among the radioresistant (NC + PD) tumors. The administered dose of RT correlated (r = 0.47, p less than 0.05) with the decrement in FDG activity among the CR + PR but not among the NC + PD patients. The biologic half-life of FDG radioactivity in tumor tissue was evaluated by dynamic scintigraphy. A change in the half-life of FDG toward the value observed in normal tissue was associated with treatment response. The results suggest that FDG imaging can be used for follow-up of RT in patients with head and neck cancer.

Deoxy Sugars↗
PubMed1987

Imaging of metastases of thyroid carcinoma with fluorine-18 fluorodeoxyglucose.

Three patients with multiple metastases of thyroid carcinoma were studied with 18F-2-fluoro-2-deoxy-D-glucose (FDG) and iodine-131 (131I) imaging. Metastases that accumulated only FDG, only 131I, or both FDG and 131I could be demonstrated. Metabolic heterogeneity was seen between different metastases in all patients. The accumulation of FDG may also differ between different metastases of the same patient. The uptake of FDG in metastases was shown to increase parallel with their progression. Metastases of thyroid carcinoma that have ceased to accumulate 131I after treatment with radioiodine may still be demonstrated with FDG. Metastases that accumulate FDG, but not 131I, may behave more aggressively than metastases that accumulate 131I, but not FDG.

Adenocarcinoma↗
PubMed1986

Scintigraphy with [18F]2-fluoro-2-deoxy-D-glucose of cancer patients.

Computerized dynamic gamma camera scintigraphy was performed with [18F]2-fluoro-2-deoxy-D-glucose [( 18F]FDG) on 10 patients with different cancers; tumor perfusion was evaluated in four patients with 99mTc-DPD. All tumors were visible in the [18F]FDG scans with tumor-to-tissue image contrast ratios of 1.2-11.7. Tumor perfusion exceeded that of the surrounding normal tissue in three of the four patients studied. Tumor-to-normal tissue [18F]FDG ratios were plotted as a function of the time. Two types of curves emerged: curves showing a linear increase in the ratio and curves showing a constant value for the ratio. These studies show that [18F]FDG can be used for clinical tumor imaging with a gamma camera, and that there appears to be biological differences in tumor uptake of [18F]FDG.

Adult↗