Biomedical subjects

H Schöder

Publications and source records attributed to H Schöder.

14 recordsLinked to original sources

PubMed2002

Diagnostic and prognostic value of [(18)F]fluorodeoxyglucose positron emission tomography for recurrent head and neck squamous cell carcinoma.

PURPOSE: Patients with recurrent head and neck squamous cell carcinoma (HNSCC) present a diagnostic and therapeutic challenge. We evaluated the diagnostic accuracy and prognostic value of [(18)F]fluorodeoxyglucose positron emission tomography (PET) in this patient population. PATIENTS AND METHODS: We performed a retrospective review of 143 patients with previously treated HNSCC who underwent 181 PET scans at our institution from May 1996 through April 2001 to detect recurrent disease. Disease recurrence within 6 months was used as the gold standard for assessing true disease status at PET. RESULTS: With equivocal sites considered positive, the sensitivity and specificity of PET for detecting recurrence overall were 96% and 72%, respectively. PET was highly sensitive and specific at regional and distant sites. At local sites, sensitivity was high, but specificity was lower because of false-positive findings. One fifth of all false-positive PET scans occurred at sites of known inflammation or infection. The area under the curve for a receiver operator characteristic curve on the basis of standardized uptake value (SUV) was 0.882 +/- 0.025. PET interpretation, SUV, and physical examination were independent predictors of relapse-free and overall survival in a time-dependent, multivariate proportional hazards model. An increase in SUV by one unit increased the relative risk (RR) of relapse by 11% and the RR of death by 14%. A positive PET interpretation increased the RR of relapse by four-fold and the RR of death by seven-fold. CONCLUSION: PET was a highly sensitive method of detecting recurrent HNSCC and provided important prognostic information for relapse-free and overall survival.

Adolescent↗

PubMed2001

Effect of whole-body (18)F-FDG PET imaging on clinical staging and management of patients with malignant lymphoma.

UNLABELLED: Correct staging is important in selecting the appropriate treatment for lymphoma patients. PET imaging with (18)F-FDG is useful for staging of lymphoma as well as for monitoring of therapy. However, to our knowledge, the clinical impact of PET on staging and management of lymphoma patients has not been reported. METHODS: Standardized questionnaires were mailed to referring physicians asking them whether and how the results of PET imaging had influenced clinical staging and management of the disease in their patients. Management changes, when present, were classified as intermodality (e.g., medical to surgical, surgical to radiation, medical to no treatment) or intramodality (e.g., altered medical, surgical, or radiotherapy approach). RESULTS: The referring physicians returned 52 of 108 questionnaires (48.1%). Physicians indicated that PET led to a change in the clinical stage in 44% of patients: 21% were upstaged and 23% were downstaged. Findings of the PET examination resulted in intermodality changes in management in 42% of patients, in intramodality changes in 10%, and in a combination of the management changes in 10%. Other, not further specified, treatment changes were reported in 6% of patients. PET did not result in any management changes in only 32% of patients. CONCLUSION: This survey-based study of referring physicians indicates that FDG PET has a major impact on the management of lymphoma patients, contributing to changes in clinical stage in 44% and changes in treatment in >60% of cases.

Adolescent↗

PubMed2000

Glucose metabolism in reperfused myocardium measured by [2-18F] 2-fluorodeoxyglucose and PET.

OBJECTIVE: [2-18F] 2-fluorodeoxyglucose (FDG) is widely used to trace glucose metabolism for cardiac imaging with positron emission tomography. Because the transport and phosphorylation rates differ for glucose and FDG, a lumped constant (LC) is used to correct for these differences. The effects of ischemia and reperfusion on the LC in vivo are unknown. To determine the validity of FDG as a tracer of glucose metabolism in post-ischemic myocardium in vivo, the relationship between glucose uptake (GU) and FDG metabolic rate (FDG-MR) was assessed early post-reperfusion following a transient ischemic event. METHODS: FDG metabolic rate, measured with FDG and PET, was compared to invasive measurements of substrate metabolism in reperfused and global myocardium of dogs subjected to 25 min ischemia and 2 h reperfusion. RESULTS: The FDG metabolic rate was decreased 20 +/- 4% in reperfused relative to remote myocardium. Glucose oxidation and lactate uptake were also decreased in reperfused relative to global myocardium, by 26 +/- 6% and 60 +/- 8% respectively. Glucose uptake did not differ significantly between reperfused and global myocardium. A linear correlation between FDG metabolic rate and glucose uptake was found in both reperfused and remote myocardium. Estimates of the LC from the slopes of the regression lines were similar in reperfused and remote myocardium, 1.25 and 1.44 respectively, and did not differ significantly from the LC determined in control dogs, 1.1. CONCLUSIONS: We conclude that the FDG metabolic rate continues to correlate well with glucose metabolism in reperfused myocardium. While FDG metabolic rate was modestly decreased in the absence of a significant change in glucose uptake, large alterations in the LC are not found 2 h post-reperfusion in vivo.

Animals↗

PubMed2000

Regulation of myocardial blood flow response to mental stress in healthy individuals.

Mental stress testing has been proposed as a noninvasive tool to evaluate endothelium-dependent coronary vasomotion. In patients with coronary artery disease, mental stress can induce myocardial ischemia. However, even the determinants of the physiological myocardial blood flow (MBF) response to mental stress are poorly understood. Twenty-four individuals (12 males/12 females, mean age 49 +/- 13 yr, range 31-74 yr) with a low likelihood for coronary artery disease were studied. Serum catecholamines, cardiac work, and MBF (measured quantitatively with N-13 ammonia and positron emission tomography) were assessed. During mental stress (arithmetic calculation) MBF increased significantly from 0.70 +/- 0.14 to 0.92 +/- 0.21 ml x min(-1) x g(-1) (P < 0.01). Mental stress caused significant increases (P < 0.01) in serum epinephrine (26 +/- 16 vs. 42 +/- 17 pg/ml), norepinephrine (272 +/- 139 vs. 322 +/- 136 pg/ml), and cardiac work [rate-pressure product (RPP) 8,011 +/- 1,884 vs. 10,416 +/- 2,711]. Stress-induced changes in cardiac work were correlated with changes in MBF (r = 0.72; P < 0.01). Multiple-regression analysis revealed stress-induced changes in the RPP as the only significant (P = 0.0001) predictor for the magnitude of mental stress-induced increases in MBF in healthy individuals. Data from this group of healthy individuals should prove useful to investigate coronary vasomotion in individuals at risk for or with documented coronary artery disease.

Adult↗

PubMed2000

Effect of mental stress on myocardial blood flow and vasomotion in patients with coronary artery disease.

UNLABELLED: In patients with coronary artery disease (CAD), mental stress may provoke ischemic electrocardiograph changes and abnormalities in regional and global left ventricular function. However, little is known about the underlying myocardial blood flow response (MBF) in these patients. METHODS: We investigated the hemodynamic, neurohumoral, and myocardial blood flow responses to mental stress in 17 patients with CAD and 17 healthy volunteers of similar age. Mental stress was induced by asking individuals to solve mathematic subtractions in a progressively challenging sequence; MBF was quantified at rest and during mental stress using 13N ammonia PET. RESULTS: Mental stress induced significant (P < 0.01) and comparable increases in rate-pressure product, measured in beats per minute x mm Hg, in both patients (from 7826 +/- 2006 to 10586 +/- 2800) and healthy volunteers (from 8227 +/- 1272 to 10618 +/- 2468). Comparable increases also occurred in serum epinephrine (58% in patients versus 52% in healthy volunteers) and norepinephrine (22% in patients versus 27% in healthy volunteers). Although MBF increased in patients (from 0.67 +/- 0.15 to 0.77 +/- 0.18 mL/min/g, P < 0.05) and healthy volunteers (from 0.73 +/- 0.13 to 0.95 +/- 0.22 mL/min/g, P < 0.001), the magnitude of flow increase was smaller in patients (14% +/- 17%) than in healthy volunteers (29% +/- 14%) (P = 0.01). The increase in MBF during mental stress correlated significantly with changes in cardiac work in healthy volunteers (r = 0.77; P < 0.001) but not in patients. CONCLUSION: Despite similar increases in cardiac work and comparable sympathetic stimulation in CAD patients and healthy volunteers, CAD patients exhibit an attenuated blood flow response to mental stress that may contribute to mental stress-induced ischemic episodes in daily life.

Ammonia↗

PubMed1999

Prevalence of myocardial viability as detected by positron emission tomography in patients with ischemic cardiomyopathy.

BACKGROUND: Detection of myocardial viability is important in patients with ischemic cardiomyopathy. Restoration of blood flow to viable myocardium is associated with improved left ventricular function and improved patient prognosis. However, the prevalence of viable myocardium in patients with ischemic cardiomyopathy is unknown. METHODS AND RESULTS: To determine the prevalence of myocardial viability, clinical [13N]ammonia/18F-deoxyglucose PET studies performed in 283 patients (age, 63+/-10 years) with ischemic heart disease (mean ejection fraction, 26+/-8%) were visually analyzed for the presence and extent of viable and nonviable myocardium. The myocardium was divided into 19 segments. The extent of viable myocardium was considered "functionally" significant if >/=5 segments ( approximately 25% of the left ventricular myocardium) exhibited a blood flow/metabolism mismatch and "prognostically" significant if 1 to 4 left ventricular segments did so. Of all patients, 41% had no evidence of viable myocardium, 55% had viable myocardium, and 4% had normal blood flow and metabolism within an enlarged left ventricle. Functionally significant viability was found in 27% and prognostically significant viability in 28% of the patients. Multivariate analysis revealed the presence of angina to be the only clinical parameter associated with the presence of functionally significant viability. CONCLUSIONS: Revascularization might improve patient prognosis in 55% and result in improved left ventricular function in 27% of all patients with ischemic cardiomyopathy.

Aged↗

PubMed1999

L-Arginine normalizes coronary vasomotion in long-term smokers.

BACKGROUND: Noninvasive measurements of myocardial blood flow (MBF) with PET revealed an abnormal coronary vasomotor response to cold pressor test in healthy long-term smokers. If coronary endothelial dysfunction accounted for this abnormality, we hypothesized that it could be reversed by L-arginine as the substrate for NO synthase. METHODS AND RESULTS: MBF was quantified with 13N-labeled ammonia and PET in 11 healthy smokers (age, 45+/-10 years; 27+/-10 years of smoking) and in 12 age-matched nonsmokers on 2 separate days. On day 1, MBF was measured at rest and, after intravenous L-arginine, during cold pressor test. On day 2, MBF was measured during cold pressor test and then at rest during L-arginine. Baseline rate-pressure product (RPP) (6559+/-1590 versus 7144+/-1157 bpmxmm Hg) and MBF (0.65+/-0.14 versus 0.73+/-0.13 mL x g-1 x min-1) were similar in nonsmokers and smokers. Cold pressor test increased RPP similarly in both groups (53+/-26% versus 46+/-26%), whereas MBF increased in nonsmokers (to 0.93+/-0.25 mL x g-1 x min-1; P<0.05) but not in smokers (0.80+/-0.16 mL x g-1 x min-1). The percent MBF increase differed between nonsmokers and smokers (44+/-25% versus 11+/-14%; P=0.0017). However, after L-arginine, the magnitude of MBF response to cold pressor test no longer differed between groups (48+/-36% versus 48+/-28%), whereas RPP again increased similarly in the 2 groups (59+/-30% versus 44+/-16%). L-Arginine had no effect on resting MBF in smokers or nonsmokers. CONCLUSIONS: Our findings implicate the coronary endothelium as the major site of the abnormal vasomotor response in long-term smokers. Cold pressor test combined with PET imaging may allow the noninvasive identification of coronary endothelial dysfunction in humans.

Adult↗

PubMed1999

Blood flow-metabolism imaging with positron emission tomography in patients with diabetes mellitus for the assessment of reversible left ventricular contractile dysfunction.

OBJECTIVES: The purpose of this study was to evaluate the predictive accuracy of positron emission tomography (PET) blood flow-F-18 fluorodeoxyglucose (FDG) imaging in coronary artery disease (CAD) patients with diabetes mellitus (DM). BACKGROUND: Positron emission tomography accurately predicts the postrevascularization improvement in left ventricular dysfunction in unselected patients with CAD. In diabetic patients, however, poor myocardial glucose utilization may limit the accuracy of the approach. METHODS: Forty patients (64+/-10 years old; 19 with DM = group I; 21 without DM = group II) with reduced left ventricular ejection fraction (LVEF = 29+/-6%) were studied with N-13 ammonia and FDG PET before coronary revascularization. Studies were performed after intravenous injection of regular insulin (group I) or oral glucose administration (group II). Blood flow-FDG mismatches and matches were identified by polar map analysis in the three vascular territories of the left anterior descending, left circumflex and right coronary artery. Wall motion and LVEF were assessed by two-dimensional echocardiography before and 158+/-123 days after revascularization. RESULTS: Of 107 vascular territories analyzed, 46 were classified as mismatch, 29 as match and 32 as normal. The FDG image quality, assessed by F-18 myocardium to blood pool activity ratios, and the predictive accuracy were similar in both groups; presence of a blood flow/FDG mismatch had a sensitivity of 92% (group I) and 94% (group II) and a specificity of 85% (group I) and 79% (group II) for an improvement in regional left ventricular function. A postrevascularization improvement in global left ventricular function was related to the extent of blood flow/FDG mismatch; LVEF increased from 30+/-7% to 35+/-7% (p = 0.017) in patients with one mismatch and from 27+/-4% to 41+/-7% (p < 0.001) in those with two mismatches. CONCLUSIONS: The predictive accuracy of blood flow/FDG imaging is maintained in patients with DM when a clinically acceptable study protocol, which guarantees good FDG image quality, is used. The extent of a blood flow/metabolism mismatch is correlated with the magnitude of the postrevascularization improvement in global left ventricular function.

Aged↗

PubMed1999

Relationship between coronary function by positron emission tomography and temporal changes in morphology by intravascular ultrasound (IVUS) in transplant recipients.

BACKGROUND: Transplant coronary vasculopathy is one of the major causes of graft failure and death in cardiac transplant recipients. A non-invasive test of coronary function to predict the course of this disease would be desirable. METHODS: To determine whether the degree of abnormalities in endothelial dependent coronary vasomotion (cold pressor testing) or endothelial independent vasodilatory capacity (intravenous dipyridamole) as determined by positron emission tomography (PET) one to two years after heart transplantation is correlated with the course of transplant vasculopathy. Nineteen patients had baseline PET and intravascular ultrasound studies (IVUS) at 18 +/- 6 months after cardiac transplantation and a follow up IVUS study 15 +/- 5 months later. RESULTS: Myocardial blood flow was higher in patients than in healthy controls (p < 0.002) but increased during cold pressor testing only in controls (p < 0.005). Myocardial blood flow normalized to the rate pressure product declined in patients (p < 0.001). Dipyridamole-induced hyperemic blood flow and the flow reserve normalized to the resting rate pressure product were lower in patients than in controls (p < 0.001 and p < 0.01). The normalized flow reserve was correlated with changes in total vessel area (r = 0.55; p = 0.02) and lumen diameter (r = 0.52; p < 0.05). CONCLUSION: These findings suggest that the degree of abnormalities in endothelial independent myocardial flow as detected by PET one to two years after transplantation is associated with morphological indices of disease progression by IVUS.

Cold Temperature↗

PubMed1998

Effects of long-term smoking on myocardial blood flow, coronary vasomotion, and vasodilator capacity.

BACKGROUND: The effect of long-term smoking on coronary vasomotion and vasodilator capacity in healthy smokers is unknown. METHODS AND RESULTS: Myocardial blood flow (MBF) was quantified with [13N]ammonia and positron emission tomography (PET) at rest, during cold pressor testing (endothelium-dependent vasomotion), and during dipyridamole-induced hyperemia in 16 long-term smokers and 17 nonsmokers. MBF at rest did not differ between the 2 groups. Cold induced similar increases in rate-pressure product (RPP) in smokers and nonsmokers. However, MBF increased only in nonsmokers and was, during cold, higher than in smokers (0.91+/-0.18 versus 0.78+/-0.14 mL x g(-1) x min(-1), P<0.05). MBF normalized to the RPP (derived from the ratio of MBF ([milliliters per gram per minute] to RPP [beats per minute times millimeters of mercury] times 10000) declined in smokers but remained unchanged in nonsmokers (0.86+/-0.10 versus 0.72+/-0.11, P=0.0006, and 0.99+/-0.25 versus 0.96+/-0.27, P=NS). The hyperemic response to dipyridamole and the myocardial flow reserve did not differ between the 2 groups. In a multiple regression model adjusted for age, sex, serum lipid levels, years of smoking, and pack-years, years of smoking was the strongest predictor of the normalized blood flow response to cold (P<0.001), followed by the HDL/LDL ratio. CONCLUSIONS: The normal hyperemic response to dipyridamole in long-term smokers indicates a preserved endothelium-independent coronary vascular smooth muscle relaxation, whereas the abnormal response to cold suggests a defect in coronary vasomotion likely located at the level of the coronary endothelium. Its severity depends on the total exposure time to smoking.

Adult↗

PubMed1998

Regulation of pyruvate dehydrogenase activity and glucose metabolism in post-ischaemic myocardium.

Pyruvate dehydrogenase (PDH) is regulated both by covalent modification and through modulation of the active enzyme by metabolites. In the isolated heart, post-ischaemic inhibition of PDH, leading to uncoupling of glycolysis and glucose oxidation and a decrease in cardiac efficiency, has been described. In vivo, post-ischaemic reperfusion leads to metabolic abnormalities consistent with PDH inhibition, but the effects of ischaemia/reperfusion on PDH are not well characterized. We therefore investigated PDH regulation following transient ischaemia in vivo. In 33 open-chest dogs, the left anterior descending (LAD) was occluded for 20 min followed by 4 h reperfusion. In 17 dogs, dichloroacetate (DCA) was injected prior to reperfusion, while 16 dogs served as controls. In dogs without DCA, glucose oxidation and lactate uptake were lower in reperfused than in remote tissue, suggesting reduced flux through PDH. However, percent active and total PDH measured in myocardial biopsies were similar in both territories, excluding covalent enzyme modification or loss of functional enzyme. DCA activated PDH activity similarly in both regions and abolished differences in glucose oxidation and lactate uptake. Thus, decreased PDH flux in reperfused myocardium does not result from covalent modification or loss of total enzyme activity, but more likely from metabolite inhibition of the active enzyme. DCA leads to essentially complete activation of PDH, increases overall glucose utilization and abolishes post-ischaemic inhibition of glucose oxidation.

Animals↗

PubMed1995

[Fistula carcinoma in chronic soft tissue infection].

Squamous cell carcinoma without accompanying osteomyelitis is a rare complication in chronic soft tissue inflammation. We report on a patient with soft tissue squamous cell carcinoma developing only two years after a war accident.

Aged↗

PubMed1994

[Solitary metastasis of prostate cancer in the tibia].

We report about a patient with a solitary tibial metastasis of a prostatic carcinoma. Metastases to the peripheral skeleton are relatively rare with a frequency of only 1-2% and are mainly found in cases of general spread of the disease. Complaints due to peripheral solitary metastases often cause misinterpretations. Bone scintigraphy is the primary method in the diagnosis of skeletal metastases, and is sometimes supported by specific radiographs. MRI yields excellent images of the extension of the tumor. It is therefore of high diagnostic value in the preoperative definition of the metastatic spread in bone and neighbouring soft tissue structures.

Aged↗

PubMed1991

[Hepatic hydrothorax without ascites].

A case of hepatic hydrothorax without clinical ascites is reported. The diagnosis was confirmed by intraperitoneal injection of 99mTc-tin colloid: scintigraphic images taken between 5 min and 18 h p.i. demonstrated a one-way transdiaphragmatic flow into the pleural cavity. The therapy consisted of diuretic treatment, pleural drainage and chemical pleurodesis, and resulted in prompt clinical improvement.

Adult↗