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Biomedical subjects

U Buell

Publications and source records attributed to U Buell.

At least 73 records · Page 4Linked to original sources
PubMed1996

Fate of the resting perfusion defect as assessed with technetium-99m methoxy-isobutyl-isonitrile single-photon emission computed tomography after successful revascularization in patients with healed myocardial infarction.

It is concluded that in patients with healed myocardial infarction, MIBI uptake at rest underestimates myocardial viability and may improve significantly if blood flow is restored. Patients with MIBI defects at rest may therefore take advantage of revascularization.

Coronary Circulation↗
PubMed1996

Myocyte degeneration and cell death in hibernating human myocardium.

OBJECTIVES: The aim of this study was to analyze the morphologic characteristics of myocyte degeneration leading to replacement fibrosis in hibernating myocardium by use of electron microscopy and immunohistochemical techniques. BACKGROUND: Data on the ultrastructure and the cytoskeleton of cardiomyocytes in myocardial hibernation are scarce. Incomplete or delayed functional recovery might be due to variable degree of cardiomyocyte degeneration in hibernating myocardium. METHODS: In 24 patients, regional wall motion abnormalities were analyzed by use of the centerline method before and 6 +/- 1 months after coronary artery bypass surgery. Preoperative technetium-99m sestamibi uptake was measured by single-photon emission computed tomography for assessing regional perfusion. Fluorine-18 fluorodeoxyglucose uptake was measured by positron emission tomography to assess glucose metabolism. Transmural biopsy specimens were taken during coronary artery bypass surgery from the center of the hypocontractile area of the anterior wall. RESULTS: The myocytes showed varying signs of mild-to-severe degenerative changes and an increased degree of fibrosis. Immunohistochemical analysis demonstrated disruption of the cytoskeletal proteins titin and alpha-actinin. Electron microscopy of the cell organelles and immunohistochemical analysis of the cytoskeleton showed a similarity in the degree of degenerative alterations. Group 1 (n = 11) represented patients with only minor structural alterations, whereas group 2 (n = 13) showed severe morphologic degenerative changes. Wall motion abnormalities showed postoperative improvements, and nuclear imaging revealed a perfusion-metabolism mismatch without significant differences between the groups. CONCLUSIONS: Long-term hypoperfusion causes different degrees of morphologic alterations leading to degeneration. Preoperative analysis of regional contractility and perfusion-metabolism imaging does not distinguish the severity of morphologic alterations nor the functional outcome after revascularization. The insufficient act of self-preservation in hibernating myocardium may lead to a progressive structural degeneration with an incomplete and delayed recovery of function after restoration of blood flow.

Adult↗
PubMed1996

Recovery of regional left ventricular dysfunction after coronary revascularization. Impact of myocardial viability assessed by nuclear imaging and vessel patency at follow-up angiography.

OBJECTIVES: This study sought to evaluate an imaging approach using technetium-99m sestamibi scintigraphy and positron emission tomography with fluorine-18 fluorodeoxyglucose for assessment of myocardial viability proved by serial quantitative left ventricular angiography. Furthermore, the influence of successful long-term revascularization on functional recovery was studied. BACKGROUND: Previous studies using positron emission tomography of myocardial perfusion and metabolism have demonstrated accurate identification of myocardial viability. However, most of these studies used a qualitative or semiquantitative wall motion analysis approach. METHODS: Nuclear imaging with semiquantitative analysis of tracer uptake was performed in 193 patients with regional wall motion abnormalities. Regions were categorized as normal, viable with perfusion/metabolism mismatch, viable without mismatch (intermediate) and scar. Seventy-two of 103 patients with subsequent revascularization underwent follow-up angiography. In 52 of 72 patients, changes in regional wall motion were measured by the centerline method from serial angiography. RESULTS: Wall motion improved in mismatch regions from -2.2 +/- 1.0 to -1.1 +/- 1.4 SD (p < 0.001). In contrast, regions with an intermediate pattern and those with scar did not improve. Restenosis or graft occlusion influenced functional outcome because regions with preoperative mismatch and successful long-term revascularization improved at follow-up (from -2.3 +/- 1.0 to -0.8 +/- 1.4 SD, p < 0.001), whereas wall motion did not change with recurrent hypoperfusion. Metabolic imaging added diagnostic information, particularly in regions with mild and moderate perfusion defects. CONCLUSIONS: This imaging approach allows detection of viability in regions with myocardial dysfunction. Wall motion benefits most in myocardium with perfusion/metabolism mismatch and successful long-term revascularization.

Aged↗
PubMed1996

Imaging of beta-oxidation by static PET with 14(R,S)-[18F]-fluoro-6-thiaheptadecanoic acid (FTHA) in patients with advanced coronary heart disease: a comparison with 18FDG-PET and 99Tcm-MIBI SPET.

14(R,S)-[18F]-fluoro-6-thiaheptadecanoic acid (FTHA) has been proposed as a PET tracer of the beta-oxidation pathway. The aim of this study was to investigate the diagnostic value of FTHA using static PET imaging in patients with ischaemically reduced left ventricular function. Twenty-one patients with angiographically proven advanced coronary heart disease were examined. All patients underwent SPET with 400 MBq [99Tcm]-2-methoxy-isobutyl-isonitrile (MIBI) for perfusion assessment and PET with 250 MBq FTHA under fasting conditions and with 150 MBq 2-[18F]-fluoro-2-deoxyglucose (FDG) following an oral glucose load. The uptake of FTHA and FDG was analysed quantitatively in 33 regions. Regional uptake was normalized to the region with highest MIBI uptake and expressed as a percentage. FTHA uptake paralleled MIBI uptake (r = 0.80) but not FDG uptake (r = 0.57). Mean FTHA uptake (38.1 +/- 16.3%) in 190 regions with severely reduced perfusion (MIBI uptake < 50%, mean uptake 36.8 +/- 9.4%) was significantly lower compared to FDG uptake (54.6 +/- 25.0%). FTHA uptake was preserved (> or = 70%) in 8 of 52 (13%) regions only with severely reduced perfusion but preserved glucose metabolism (FDG uptake > or = 70%). The similarity between FTHA and MIBI uptake suggests that static PET imaging with FTHA is of limited value when distinguishing between ischaemic or hibernating myocardium and scar. The underestimation of viability may be caused both by the dependence of uptake on flow and the suppression of beta-oxidation in regional chronic ischaemia under fasting conditions.

Aged↗
PubMed1996

Prostate-specific antigen as a marker of bone metastasis in patients with prostate cancer.

OBJECTIVE: Staging in patients with newly diagnosed untreated cancer of the prostate has significant ramifications on the management of the disease. Currently measurement of the serum prostate-specific antigen (PSA) concentration and radionuclide bone scan are two important procedures in the metastatic workup of these patients. We retrospectively evaluated the efficacy of PSA as a staging marker to discriminate prostate cancer patients with bone metastases from those without bone metastases. MATERIALS AND METHODS: In a retrospective study 158 prostate cancer patients with (n = 21) and without (n = 137) bone metastases were analyzed. In all patients the initial PSA measurement as well as the radionuclide bone scan were evaluated. RESULTS: Patients with bone metastases demonstrated a median serum PSA concentration of 151 ng/ml and only 1 patient revealed a serum PSA concentration of <10 ng/ml. This resulted in a negative predictive value of 98%. In addition 67% of these patients demonstrated a serum PSA concentration of >100 ng/ml, which resulted in a positive predictive value of 74% and an overall accuracy of 92%. CONCLUSION: The serum PSA concentration seems to provide useful information with regard to the presence of bone metastasis in patients with newly diagnosed cancer of the prostate. A serum PSA value of <10 ng/ml nearly excludes bone metastases, whereas a serum PSA value of> 100 ng/ml is highly predictive of bone metastases.

Adult↗
PubMed1994

Comparison of thallium-201 single-photon emission tomography after rest injection and fluorodeoxyglucose positron emission tomography for assessment of myocardial viability in patients with chronic coronary artery disease.

This prospective study in 42 patients with chronic coronary artery disease and severe wall motion abnormalities (sWMA) on cineventriculography (24 patients with previous myocardial infarction; ejection fraction, 45% +/- 13%) was designed to compare myocardial thallium-201 uptake after rest injection and normalized fluorodeoxyglucose (18FDG) uptake (after oral glucose load) for assessment of a rest 201Tl protocol to evaluate myocardial viability. The left ventricle was divided into the supply territory of the left anterior descending coronary artery (LAD) and the lateral wall and posterior territory (inferior, posterior and posteroseptal segments) because of the high variability of left circumflex and right coronary artery supply territories. Segmental 201Tl uptake in single-photon emission tomography (SPET) and segmental normalized 18FDG uptake (13 segments per patient) showed a close linear relationship in the LAD territory (r = 0.79) and in the lateral wall (r = 0.77), while the correlation in the posterior territory was considerably lower (r = 0.52). 201Tl/18FDG concordance was defined as an 18FDG uptake exceeding 201Tl uptake by < 20%. Discordance was assumed if 18FDG exceeded 201Tl uptake by at least 20%. Concordant results were shown by 81% (439/541) of segments. In segments with severe 201Tl reduction (< or = 50% of peak, n = 78) discordance was observed in 10% of segments in the LAD territory and lateral wall (n = 62) and in 44% of segments in the posterior territory (n = 16).(ABSTRACT TRUNCATED AT 250 WORDS)

Artifacts↗
PubMed1994

Transoesophageal pacing echocardiography for detection of restenosis after percutaneous transluminal coronary angioplasty.

Non-invasive documentation of restenosis after successful percutaneous transluminal coronary angioplasty (PTCA) remains a problem. Thus, transoesophageal pacing echocardiography (TPE) with simultaneous rapid atrial pacing via the same probe, a recently validated method for detection of coronary artery disease, was used in 60 patients for detection of restenosis after successful PTCA (54 patients with one and six patients with multivessel PTCA). The patients came for routine follow-up angiography 5.4 +/- 3.7 months after PTCA regardless of clinical status. Restenosis (diameter stenosis > or = 50%) was demonstrated in 22 patients. Disease progression in previously normal vessels was noted in three additional patients. Results for detection of restenosis and disease progression were compared to exercise ECG and in 40 patients to Tc-99m methoxy-isobutyl-isonitrile (MIBI)-radionuclide perfusion imaging. Diagnostic standard exercise ECG could be performed in only 38 patients, due to peripheral vascular disease, joint disease or premature exhaustion in the rest of patients. TPE was non-diagnostic in two patients due to ineffective pacing or patient discomfort. Sensitivity of TPE for detection of restenosis and disease progression after PTCA was 84% compared with 50% and 86% for exercise ECG and Tc-99m MIBI-SPECT (P < 0.03 and ns), respectively. Specificity of TPE (85%) was also higher than that of exercise ECG (59%, P < 0.03) and comparable to the specificity of MIBI-SPECT (84%). Overall accuracy of TPE was far superior to exercise ECG and similar to MIBI-SPECT (84% vs 54% and 85%) (P = 0.0007 and ns, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1994

Significance of defect severity in technetium-99m-MIBI SPECT at rest to assess myocardial viability: comparison with fluorine-18-FDG PET.

UNLABELLED: The pathophysiological significance of 99mTc-MIBI uptake at rest for assessing myocardial viability in patients with coronary artery disease (CAD) is still controversial. Therefore, we studied the relationship of 99mTc-MIBI uptake at rest and preserved or absent uptake of 18FDG as assessed with PET in 111 consecutive patients after overnight withdrawal of their antianginal medication. METHODS: Each ventricle was evaluated in 13 segments derived from 25 regions of interest (ROIs) in short-axis cuts and 18FDG uptake was normalized to the intraindividual normal reference ROI (ROI with maximal = 100% 99mTc-MIBI uptake). Segments with a normalized 18FDG uptake > 70% were defined as viable while segments with a 18FDG uptake < 50% were defined as nonviable. RESULTS: Five to 11% of segments with 99mTc-MIBI uptake at rest < or = 30% of peak activity were viable and 80%-84% nonviable. Of moderate to severe 99mTc-MIBI defects at rest (31%-70% of peak), 13%-61% were viable. Segmental 99mTc-MIBI uptake and normalized 18FDG uptake were linearly correlated (r = 0.61, n = 1443, p < 0.001). In segments revealing severely reduced 99mTc-MIBI uptake (< or = 50% of peak) the correlation was considerably lower (r = 0.44, n = 295, p < 0.001). CONCLUSIONS: In patients with CAD, 99mTc-MIBI uptake underestimates myocardial viability in comparison to 18FDG-PET. Myocardial 99mTc-MIBI uptake therefore appears to reflect myocardial blood flow rather than myocardial viability. Patients with moderate and severe 99mTc-MIBI defects at rest may benefit from additional metabolic PET imaging prior to final therapeutic decisions.

Adult↗
PubMed1993

Uptake of radiolabeled anti-CEA antibodies in human colorectal primary tumors as a function of tumor mass.

An inverse correlation has been demonstrated between tumor uptake (u, in units of % injected dose/kg) of monoclonal antibody (Mab) and tumor mass (m, in units of g) for colorectal carcinoma in a series of 19 consecutive patients. The correlation (rho = -0.510), developed using surgical samples was of the form u = amb and was significant at the 2% level of confidence. All tumors were positive for carcinoembryonic antigen (CEA) and the radiopharmaceutical was an iodine-131 labeled anti-CEA Mab. Such correlations have been predicted earlier from murine and rat tumor uptake data. The slope parameter (b) was -0.362, a number consistent with the previous value (-0.382) found in anti-CEA experiments in mice bearing human xenograft LS174T tumors.

Carcinoembryonic Antigen↗
PubMed1993

The case of aphasia or neglect after striatocapsular infarction.

The occurrence of aphasia or neglect was related to anatomo-structural (CT/MRI), functional [regional cerebral blood flow (rCBF)] and pathogenetic features [duration of middle cerebral artery (MCA) occlusion and degree of cortical leptomeningeal anastomoses] in 57 cases (26 with and 31 without aphasia or neglect) with strictly subcortical infarcts of one defined type, i.e. striatocapsular infarcts. No distinct pattern of language disturbances was found. Aphasic syndromes did not differ in the amount of involvement of the putamen, pallidum, head of caudate nucleus and white matter. Patients with aphasia or neglect had larger infarcts than those without. However, there was no specific involvement of the basal ganglia, the internal capsule or the deep white matter in patients with aphasia or neglect. Patients with aphasia or neglect had a significantly longer duration of MCA occlusion and mostly poor leptomeningeal collaterals. The cortical rCBF was significantly decreased in the cortical MCA territory in the patients with aphasia or neglect only. The rCBF remained low at follow-up after 1 year and corresponded to focal cortical atrophy on MRI, although neglect had subsided completely in all patients and aphasia had improved considerably in almost 75% of the cases. Aphasia or neglect after striatocapsular infarcts are most likely due to selective neuronal loss of the cerebral cortex due to prolonged MCA occlusion and insufficient collateral blood flow. Individual differences in recovery from aphasia after striatocapsular infarction can be explained in terms of the number of surviving cortical neurons.

Adolescent↗
PubMed1993

99Tcm-methoxyisobutylisonitrile stress/rest SPECT in patients with constant complete left bundle branch block.

Numerous studies have revealed frequent false positive septal findings of 201Tl stress imaging in patients with left bundle branch block (LBBB) even with angiographically excluded significant coronary artery disease (CAD). To scrutinize this phenomenon for stress/rest 99Tcm-methoxyisobutylisonitrile (MIBI) single photon emission computed tomography (SPECT) was used to review 22 patients with constant LBBB. The findings were reversible septal defect in one patient, partially reversible septal defect in one patient and irreversible septal defects in eight patients. In four patients 99Tcm-MIBI scans were entirely normal. Thus, 12/22 (55%) patients revealed normal septal 99Tcm-MIBI uptake. Both patients with a stress-induced septal defect revealed a significant left anterior descending artery stenosis on coronary angiography. These preliminary results suggest, that 99Tcm-MIBI might be more specific and accurate than 201Tl in the evaluation of CAD in patients with LBBB because of apparently rare or absent false positive septal findings.

Adult↗
PubMed1993

Pancreatic cancer detected by positron emission tomography with 18F-labelled deoxyglucose: method and first results.

In order to evaluate the utility of positron emission tomography (PET) with 18F-labelled deoxyglucose (FDG) for detection of pancreatic cancer 15 patients with pancreatic masses shown by computed tomography were investigated. Static PET scans covering an axial field of view of 15 cm were obtained 45 min after intravenous injection of 150-300 MBq FDG. Focally increased FDG accumulation was present in 12 out of 13 patients with histologically proven adenocarcinoma, in particular in eight of nine lymph node and four of five liver metastases. Scans of two patients with chronic pancreatitis confirmed by surgery revealed a normal FDG distribution. Contrast between tumour and normal tissue depended the metabolic situation prior to FDG injection. High ratios were found in fasting patients whereas no elevated FDG uptake was measured in an insulin-dependent diabetic suffering from carcinoma of the pancreatic head. We conclude that FDG PET might have the potential for detection and even differentiation of pancreatic carcinoma from chronic pancreatitis. Further studies are necessary to substantiate these preliminary findings and to optimize results in diabetic patients.

Adenocarcinoma↗
PubMed1993

Septal glucose metabolism in patients with coronary artery disease and left bundle-branch block.

BACKGROUND: Positron-emission tomography (PET) using 18F-deoxyglucose (FDG) is used for assessment of myocardial viability in regions with impaired resting perfusion and contractility. This report describes FDG-PET septal findings in six patients with complete left bundle-branch block (LBBB) and chronic coronary artery disease (CAD) compared to a reference population without LBBB. METHODS: All patients had documented left anterior descending artery stenosis and septal wall-motion abnormality. Attenuation-corrected PET scans were acquired after the administration of oral glucose load, and myocardial perfusion at rest was assessed using 99mTc-methoxyisobutylisonitrile (MIBI) single-photon emission computed tomography (SPECT). Myocardial FDG and MIBI uptake in 25 regions of interest were expressed as percentage uptake of the individual reference region, and average uptake values as well as the FDG/MIBI ratio were calculated for the entire septum and lateral wall. RESULTS: Relative to septal MIBI uptake, septal FDG uptake was decreased in patients with LBBB and increased in patients with LBBB. The septal FDG/MIBI ratio was significantly lower in patients with LBBB than in those without LBBB (0.62 +/- 0.12 vs 1.24 +/- 0.24, respectively; P < 0.001) and did not exceed 0.8 in patients with LBBB. In patients without LBBB, the ratio constantly exceeded 0.8. CONCLUSIONS: In patients with LBBB and CAD, septal reduction of FDG uptake may significantly exceed the reduction of septal perfusion as assessed by MIBI-SPECT. Decreased septal FDG uptake may be attributed in part to the conduction abnormality, resulting in limited value for this tool as an assessment of septal viability in this patient group.

Bundle-Branch Block↗
PubMed1993

Bone marrow immunoscintigraphy compared with conventional bone scintigraphy for the detection of bone metastases.

Immunoscintigraphy of haematopoetic bone marrow was compared to conventional bone scanning in 141 patients with malignant disease. Forty patients had breast cancer, 25 prostatic carcinoma, 14 kidney or bladder cancer, 13 bronchial carcinoma, 39 malignant lymphoma and 10 multiple myeloma. A total of 18,800 skeletal regions were evaluated. Marrow scans showed more metastatic lesions than bone scanning in all patient subgroups. Computerized tomography was concordant with bone marrow scintigraphy in 83.3% of 323 skeletal sites. Bone marrow scans in 30 control patients with fever of unknown origin were abnormal only in 3 patients and in only 7 out of 2,135 skeletal regions examined. In patients with malignant lymphoma, bone marrow histology or aspiration cytology was concordantly positive in 14 and concordantly negative in 17 patients. We conclude that immunoscintigraphy of haematopoetic bone marrow provides a reliable, sensitive and safe novel approach for non-invasive detection of metastatic spread to the skeleton.

Aged↗
PubMed1993

Quantitative analysis of anti-CEA antibody accumulation in human colorectal carcinomas.

In order to obtain quantitative data on intratumoral antibody accumulation we analyzed resected colorectal adenocarcinomas of 25 patients who had undergone immunoscintigraphy 4-14 days earlier. All had been injected with 0.5-1.0 mg intact anti-CEA antibody (BW 431/26) labelled with 70-80 MBq131I. Correlation of tissue radioactivity concentrations with tumor characteristics revealed significantly higher values in necrotic compared to viable as well as in CEA-positive compared to CEA-negative viable tumor tissue indicating action of both specific and unspecific uptake mechanisms. In contrast, diagnostic results of immunoscintigraphy were influenced by tumor size only. 11 of 12 false-negative findings were obtained in tumors < 4 cm in diameter. Since ex-vivo scintigraphy of resected specimens correctly visualized all but one of these lesions, it is concluded that technical limitations of scintigraphy are the main cause of negative results of radioimmunoimaging with 131I-labelled antibodies.

Adenocarcinoma↗
PubMed1992

Fluorine-18 deoxyglucose PET for assessment of viable myocardium in perfusion defects in 99mTc-MIBI SPET: a comparative study in patients with coronary artery disease.

Extent and frequency of viable tissue in myocardial segments yielding a perfusion defect on technetium-99m methoxyisobutylisonitrile (99mTc-MIBI), single photon emission tomography (SPET) at rest was prospectively investigated with 2-18F-2-deoxyglucose (18FDG) positron emission tomography (PET) in 46 patients with chronic coronary artery disease (CAD). Of these, 43 had a history of old myocardial infarction. For comparative visual and quantitative evaluation of identical anatomical slices, PET image files were converted into the SPET file structure and into the same matrix size. SPET and PET images were documented and visually (9 segments/patient) or semiquantitatively evaluated by a target-like polar map. Relative perfusion was expressed in percentage of peak 99mTc-MIBI uptake. Sample 18FDG uptake was related to the 18FDG uptake in the area of such maximal perfusion (18FDG uptake was 100% at the 100% 99mTc-MIBI uptake area). Of 414 segments, 167 (40%) revealed a resting perfusion defect. 18FDG uptake was present in 38 (23%) of the defects, while another 40 (24%) segments yielded 18FDG uptake in the periphery of the defect. When grouped according to the degree of 99mTc-MIBI uptake-reduction (in percentage of peak activity), 80% of severe defects (less than or equal to 30% of peak uptake), 48% of moderate (31%-50% of peak uptake) and 31% of mild (greater than 50% of peak uptake) defects were considered as non-viable on the basis of 18FDG uptake. Complete viability was found in none of the severe defects in contrast to 29% of moderate and 35% of mild perfusion defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗
PubMed1992

The radiation dose to surgical personnel during intraoperative radioimmunoscintimetry.

To estimate the radiation exposure to surgical personnel caused by intraoperative radioimmunoscintimetry, we measured dose rates at different distances from patients who had been injected with 950 MBq technetium-99m-labelled intact carcinoembryonic antigen (CEA)-specific antibodies (Szintimun CEA, Behring AG Marburg, FRG) for immunoscintigraphy 24 h earlier. At 0.05 m (corresponding to working positions during surgery) we found 2.0-16.0 microSv h-1 (average 6.4), which is similar to results for nuclear medicine staff. Thus, if radioimmunoscintimetry is to become a routine procedure, according to national regulations in some countries of the European Communities surgical personnel might be regarded as professionally exposed to radiation.

Colorectal Neoplasms↗