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Biomedical subjects

G Hutchins

Publications and source records attributed to G Hutchins.

At least 19 recordsLinked to original sources
PubMed2001

FDG-PET sensitivity for melanoma lymph node metastases is dependent on tumor volume.

BACKGROUND AND OBJECTIVES: The purpose of this study is to determine the tumor volume threshold for successful positron emission tomography (PET) imaging of melanoma nodal metastases. METHODS: Review of a clinical series of patients who had FDG-PET imaging of regional lymph node basins followed by lymphadenectomy. Lymph node tumor volumes were calculated from direct measurements of metastatic nodule(s) in formalin fixed specimens. PET scan interpretations were correlated with histology to determine sensitivity. Sensitivity was correlated with the aggregate lymph node tumor volume in the nodal basin and with AJCC stage group. RESULTS: Forty-five patients with 49 pathologically positive regional nodal basins comprised the study group. Median total basin tumor volume was 28.3 mm(3)(range 0.004-22,879 mm(3)). FDG-PET sensitivity for detection of all tumor volumes was 0.49. The observed 90% sensitivity threshold for detection of nodal metastases was > or = 78 mm(3). PET sensitivity was 0.14 for detection of tumor volumes < 78 mm(3). PET sensitivity differed by prescan AJCC stage: I-0.0; II-0.24; III-0.81; IV-1.0 (P < 0.001). CONCLUSIONS: FDG-PET reliably detects lymph node tumor deposits greater than approximately 80 mm(3) volume, but sensitivity falls rapidly below this. This amount of tumor is most likely to occur in patients with AJCC stage III or IV disease.

Fluorodeoxyglucose F18↗
PubMed1999

Lymph node tumor volumes in patients undergoing sentinel lymph node biopsy for cutaneous melanoma.

BACKGROUND: Regional lymph node tumor volumes in patients undergoing sentinel lymph node (SN) biopsy (SNB) for treatment of cutaneous melanoma have not been described. The objectives of this study were to describe the lymph node tumor volumes typically seen in this population and to correlate tumor volumes with tumor thickness and positive SN characteristics. METHODS: Review of a consecutive series of patients with clinically localized cutaneous melanoma who underwent SNB of nonpalpable regional lymph node basins followed by complete lymphadenectomy (LND) was performed. Multiple lymph node sections from positive SNs and nonsentinel nodes (NSNs) in LND specimens were examined microscopically. Individual tumor deposit diameters were measured using an ocular micrometer. Aggregate tumor volumes were calculated for SN and LND specimens. Tumor volumes and SN and LND positivity rates were correlated with tumor thickness, the number of positive SNs, and the presence of multiple SN tumor deposits. RESULTS: SNB procedures were performed for 149 melanomas in 189 regional nodal basins. The mean tumor depth was 2.48 mm. The mean number of SNs/basin was 2.1. Thirty-two of 149 SNB procedures (21.5%) revealed a total of 34 nodal basins with at least one positive SN. The median tumor volume in positive SNs was 4.7 mm3 (range, 0.1-3618 mm3; mean, 209 mm3). The median aggregate tumor volume in positive LND specimens was 4.9 mm3 (range, 0.1-3618 mm3; mean, 224 mm3). Six basins (17.6%) contained at least one positive NSN. The regional node aggregate tumor volume correlated weakly with tumor thickness (Pearson's correlation coefficient = .302, P = .0934). NSN positivity was not predicted by tumor thickness, American Joint Committee on Cancer tumor stage, number of positive SNs, or number of metastatic deposits within SNs. CONCLUSIONS: Most melanoma-positive SNs contain minute tumor volumes. Tumor thickness and patterns of SN metastases may not be predictive of tumor burden or the presence of positive NSNs.

Biopsy↗
PubMed1999

Prospective study of fluorodeoxyglucose-positron emission tomography imaging of lymph node basins in melanoma patients undergoing sentinel node biopsy.

PURPOSE: To prospectively compare positron emission tomography (PET) imaging of regional lymph node basins to sentinel node biopsy (SNB) in patients with American Joint Committee on Cancer (AJCC) stage I, II, and III melanoma localized to the skin. METHODS: Patients with cutaneous melanoma with Breslow's depth greater than 1 mm (AJCC T2-4N0M0) or localized regional cutaneous recurrence (TxN2bM0) underwent whole-body imaging of glucose metabolism with fluorodeoxyglucose (FDG) PET followed by SNB. PET scans were interpreted in a blinded fashion and compared with histologic analyses of SNB specimens and clinical follow-up examination. Nodal tumor volumes were estimated. RESULTS: Eighty-nine lymph node basins were evaluated by FDG-PET and SNB in 70 assessable patients. Eighteen patients (25.7%) had lymph node metastases at the time of FDG-PET imaging: 17 proved by SNB (24.3%) and one by follow-up examination (1.4%). Median tumor volume in positive sentinel node basins was 4.3 mm3 (range, 0.07 to 523 mm3). Sensitivity of SNB for detection of occult regional lymph node metastases was 94.4%, specificity was 100%, positive predictive value (PPV) was 100%, and negative predictive value (NPV) was 98.6%. Sensitivity of FDG-PET was 16.7%, specificity was 95.8%, PPV was 50%, and NPV was 81.9%. At a median follow-up duration of 16.6 months, seven patients (10%) developed recurrent disease. PET predicted one recurrence (14.3%) in a node basin missed by SNB. CONCLUSION: FDG-PET is an insensitive indicator of occult regional lymph node metastases in patients with melanoma because of the minute tumor volumes in this population. FDG-PET does not have a primary role for staging regional nodes in patients with clinically localized melanoma.

Adult↗
PubMed1999

Positron emission tomography in cochlear implant and auditory brain stem implant recipients.

OBJECTIVE: The purpose of this study was to determine whether similar cortical regions are activated by speech signals in profoundly deaf patients who have received a multichannel cochlear implant (CI) or auditory brain stem implant (ABI) as in normal-hearing subjects. STUDY DESIGN: Positron emission tomography (PET) studies were performed using a variety of discrete stimulus conditions. Images obtained were superimposed on standard anatomic magnetic resonance imaging (MRI) for the CI subjects. The PET images were superimposed on the ABI subject's own MRI. SETTING: Academic, tertiary referral center. PATIENTS: Five subjects who have received a multichannel CI and one who had received an ABI. INTERVENTION: Multichannel CI and ABI. MAIN OUTCOME MEASURE: PET images. RESULTS: Similar cortical regions are activated by speech stimuli in subjects who have received an auditory prosthesis. CONCLUSIONS: Neuroimaging provides a new approach to the study of speech processing in CI and ABI subjects.

Acoustic Stimulation↗
PubMed1998

Heterogeneous atrial denervation creates substrate for sustained atrial fibrillation.

BACKGROUND: Heterogeneous electrophysiological properties, which may be due in part to autonomic innervation, are important in the maintenance of atrial fibrillation (AF). We hypothesized that heterogeneous sympathetic denervation with phenol would create a milieu for sustained AF. METHODS AND RESULTS: After the determination of baseline inducibility, 15 dogs underwent atrial epicardial phenol application and 11 underwent a sham procedure. After 2 weeks of recovery, the animals had repeat attempts at inducing AF and effective refractory period (ERP) testing. Epicardial maps were obtained to determine local AF cycle lengths. ERPs were determined at baseline and during sympathetic, vagal, and simultaneous vagal/sympathetic stimulation. Dogs then underwent PET imaging with either a sympathetic ([11C]hydroxyephedrine, HED) or parasympathetic (5-[11C]methoxybenzovesamicol, MOBV) nerve label. None of the animals had sustained AF (>60 minutes) at baseline. None of the sham dogs and 14 of 15 phenol dogs had sustained AF at follow-up. Sites to which phenol was applied had a significantly shorter ERP (136+/-17.6 ms) than those same sites in the sham controls (156+/-19.1 ms) (P=0.01). Although there was no difference in the ERP change with either vagal or sympathetic stimulation alone between phenol and nonphenol sites, the percent decrease in ERP with simultaneous vagal/sympathetic stimulation was greater in the phenol sites (17+/-8%) than in the nonphenol sites (9+/-9%) (P=0.01). There was a significantly increased dispersion of refractoriness (21+/-6.4 ms in the sham versus 58+/-14 ms in the phenol dogs, P=0.01) as well as dispersion of AF cycle length (49+/-10 ms in the sham versus 105+/-12 ms in the phenol dogs, P=0.0001). PET images demonstrated defects of HED uptake in the areas of phenol application, with no defect of MOBV uptake. CONCLUSIONS: Heterogeneous sympathetic atrial denervation with phenol facilitates sustained AF.

Animals↗
PubMed1998

Pitch processing in the human brain is influenced by language experience.

Positron emission tomography (PET) was used in a cross-linguistic study to compare pitch processing in native speakers of English, a nontone language, with those of Thai, a tone language. When discriminating pitch patterns in Thai words, only the Thai subjects showed activation in the left frontal operculum. Activation of this region near the classically defined Broca's area suggests that the brain recognizes functional properties, rather than simply acoustic properties, of complex auditory cues in accessing language-specific mechanisms in pitch perception.

Acoustic Stimulation↗
PubMed1998

FDG-PET and MRI in temporal lobe epilepsy: relationship to febrile seizures, hippocampal sclerosis and outcome.

OBJECTIVE: To correlate the volumetric head magnetic resonance imaging (MRI) and fluorodeoxyglucose-positron emission tomography (FDG-PET) scan findings with the history, intracarotid amobarbital procedure, pathology, and outcome in patients with medically refractory temporal lobe epilepsy. MATERIAL AND METHODS: Thirty-eight patients with temporal lobe epilepsy treated surgically following a comprehensive presurgical evaluation. Follow-up ranged from 12 to 44 months. RESULTS: Volumetric MRI showed ipsilateral hippocampal atrophy in 29 (76%), and PET scan showed ipsilateral temporal hypometabolism (PET-TH) in 31 (81.5%) of patients. Eighty-three percent of those patients with hippocampal sclerosis on MRI (MRI-HS) had ipsilateral PET-TH. Sixty-six percent of patients with MRI-HS had a history of prolonged febrile convulsions or a childhood febrile illness accompanied by convulsions, and 77% of patients with MRI-HS had pathologically proven hippocampal sclerosis (HS). Ninety percent became seizure free or had rare seizures. CONCLUSION: FDG-PET scans and head MRIs were complementary; 95% of patients had either MRI-HS or temporal hypometabolism. MRI-HS correlated with a history of febrile seizures and pathologically demonstrated hippocampal sclerosis. Ninety-three percent of patients had focal functional deficits on the epileptogenic side. Concordance between PET temporal hypometabolism and MRI-HS correlated with better outcome.

Adolescent↗
PubMed1997

Initial assessment of positron emission tomography for detection of nonpalpable regional lymphatic metastases in melanoma.

BACKGROUND: The purpose of this pilot study is to determine the feasibility of positron emission tomography with fluorodeoxyglucose (FDG-PET) for detection of nonpalpable regional lymph node metastases in patients with melanoma. METHODS: Adult patients with histologically proven cutaneous melanoma planned to undergo surgical lymphadenectomy for treatment of nonpalpable subclinical or residual metastatic melanoma in regional lymph node basin(s) participated. Each patient underwent attenuation-corrected PET imaging of the regional lymph node basin(s) with F18 fluorodeoxyglucose (FDG) followed by complete surgical lymphadenectomy. FDG-PET scans were interpreted prospectively by an experienced nuclear medicine physician. FDG-PET scan interpretations and histologic results were then correlated. RESULTS: Eleven patients underwent 12 FDG-PET scans followed by 12 operations to clear 14 regional lymph node basins. FDG-PET correctly predicted the presence of metastatic melanoma in seven of seven surgical specimens. FDG-PET scans correctly predicted the absence of disease in seven of seven histologically negative node basins. Sensitivity was 1.0; specificity was 1.0. CONCLUSIONS: This study suggests that increased fluorodeoxyglucose uptake in palpably unremarkable regional lymph node basins in patients with melanoma is highly suggestive of metastatic disease.

Adult↗
PubMed1996

Myocardial rubidium-82 tissue kinetics assessed by dynamic positron emission tomography as a marker of myocardial cell membrane integrity and viability.

BACKGROUND: Recent reports have demonstrated the clinical use of rubidium-82 chloride (Rb-82) in combination with positron emission tomography (PET) not only as a tracer of myocardial blood flow but also as a marker of cell membrane integrity using static imaging early and late after tracer injection. The purpose of this study was to compare myocardial Rb-82 kinetics assessed by dynamic PET imaging as a marker for tissue viability with regional fluorine-18 fluorodeoxyglucose (FDG) uptake in patients with coronary artery disease. METHODS AND RESULTS: Twenty-seven patients with angiographically proven coronary artery disease and 5 subjects with a low likelihood for coronary artery disease underwent dynamic PET imaging under resting conditions using Rb-82 and FDG. Both image sequences served as input data for a semiautomated regional analysis program. This program generated polar maps representing Rb-82 tissue half-life and FDG utilization assessed by Patlak's approach. Myocardial tissue viability was visually determined from static Rb-82 and FDG images. Regions were categorized as normal, ischemically compromised, and scar tissue. Their coordinates were subsequently copied to the functional polar maps for further analyses. In normal subjects, Rb-82 tissue half-life was homogeneous throughout the left ventricle (90 +/- 11 seconds). In coronary patients, differences between Rb-82 tissue half-lives in normal and scar tissue were highly significant (95 +/- 10 and 57 +/- 15 seconds, respectively; P < .0001). FDG uptake in these two tissue groups was 78 +/- 12% and 40 +/- 13%, respectively (P < .0001). Ischemically compromised tissue with reduced perfusion but maintained FDG uptake displayed an Rb-82 half-life of 75 +/- 9 seconds, indicating active cellular tracer retention, which was significantly different from scar tissue. Overall agreement of tissue categorization as either viable or scar was 86% between Rb-82 kinetics and FDG utilization. In a subgroup of 11 patients with all three tissue types within one image set, Rb-82 tissue half-life discriminated between normal, ischemic, and scar tissue (97 +/- 9, 75 +/- 9, and 60 +/- 15 seconds, respectively; P < .01). CONCLUSIONS: This study demonstrated a significant relationship between cell membrane integrity as assessed by dynamic Rb-82 PET imaging and myocardial glucose utilization as a marker for tissue viability. In regions with reduced perfusion, Rb-82 kinetics was different in compromised but metabolically active and irreversibly injured myocardium. The predictive value of this approach must be evaluated in follow-up studies.

Adult↗
PubMed1995

Quantification of regional myocardial perfusion by PET: rationale and first clinical results.

With the recent advances in interventional cardiology there is increasing need for characterization of the functional effects of coronary artery stenosis. Stress echocardiography and SPECT perfusion imaging are standard techniques for the qualitative assessment of regional function and perfusion in patients with proven or suspected coronary artery disease. However, Positron emission tomography (PET) provides quantitative measurements of regional myocardial perfusion. In combination with pharmacological stress testing, relative and absolute coronary reserve measurements can be used to define functional significance of regional coronary artery disease. First clinical results indicate that there is an overall agreement between angiographic and functional disease severity. However, there is a relatively large scatter of coronary reserve flow in patients with 50-90% coronary artery stenosis, which emphasizes the complimentary role of perfusion imaging in the prediction of functional severity. In addition, first studies in asymptomatic patients with a high risk for coronary artery disease suggest that PET coronary reserve flow measurement may be more sensitive than angiographic criteria for detection of early alterations in coronary vascular reactivity. Absolute quantification of blood flow may be useful in disease processes which affect the entire left ventricle such as vasculopathy in cardiac transplants, as well as endothelial dysfunction in patients with hypertension and cardiomyopathy. Future studies have to demonstrate the prognostic value of the quantitative estimate of coronary reserve as regards clinical outcome in patients with various coronary abnormalities. Quantitative flow measurements will be useful for monitoring progression and regression of coronary artery disease as well as assessment of acute and chronic therapy.

Blood Flow Velocity↗
PubMed1993

Use of carbon-11 acetate and dynamic positron emission tomography to assess regional myocardial oxygen consumption in patients with acute myocardial infarction receiving thrombolysis or coronary angioplasty.

Carbon-11 (C-11) acetate has been introduced for the noninvasive measurements of myocardial oxygen consumption. This study was designed to assess regional C-11 acetate clearance in patients with acute myocardial infarction. Thirty-one patients were studied within 8 days of acute myocardial infarction. C-11 acetate washout-rate constants were significantly lower in the infarct territory than in the remote myocardium (p < 0.008). The scintigraphic measurements correlated with heart rate-blood pressure product in the remote as well as infarct areas (0.52 and 0.48, respectively). There was no significant correlation to left ventricular ejection fraction. C-11 washout rates were significantly affected by beta-receptor therapy as assessed by multiple regression analysis. Thus, C-11 acetate kinetics allow noninvasive characterization of regional myocardial oxygen demand, which may be useful in assessing the extent of myocardial injury and myocardial oxygen demand of remote myocardium.

Adult↗
PubMed1992

Correlation of the complete version of the Selvester QRS scoring system with quantitative anatomic findings for multiple left ventricular myocardial infarcts.

The correlation between myocardial infarct size estimated by the complete version of the Selvester QRS scoring system and that documented by pathoanatomic studies has been reported for single anterior, inferior and posterolateral infarcts. Although previous studies described electrocardiographic changes in patients with multiple infarcts, no quantitative documentation of the ability of such changes to estimate the total amount of left ventricular infarction has been reported. This study of 32 patients with anatomically documented multiple infarcts shows a significant correlation between QRS-estimated and anatomically documented sizes (r = 0.44; p = 0.01), which is less than that previously reported for single infarcts in the anterior, inferior and posterolateral locations. Several of the 54 electrocardiographic criteria were never satisfied. Criteria for posterior infarction were seldom present, suggesting "cancellation effect" of coexisting anterior infarction. These results will be the basis for future modification of QRS criteria for estimating myocardial infarct size.

Adult↗
PubMed1991

Imaging of renal cancer using positron emission tomography with 2-deoxy-2-(18F)-fluoro-D-glucose: pilot animal and human studies.

The feasibility of imaging renal cancers with 2-deoxy-2-[18F]-fluoro-D-glucose (FDG) and whole-body positron emission tomographic scanning was assessed in nude mice with human renal adenocarcinoma xenografts and then in 5 patients with primary renal cancer (4 adenocarcinomas and 1 transitional cell carcinoma). In nude mouse biodistribution studies tumor FDG uptake was maximal at 0.33 to 2 hours but tumor-to-blood ratios increased continuously to 7.8/l. by 4 hours after intravenous FDG injection. In all 5 patients primary and metastatic tumors were imaged within 1 hour by FDG positron emission tomography following intravenous injection of the FDG. By contrast, an hepatic hemangioma did not accumulate FDG. In summary, FDG metabolic and anatomical imaging of primary and metastatic renal cancer is feasible and in these pilot studies appears to be a promising imaging methodology that may be further enhanced by delayed imaging times. Additional study in a larger number of patients is essential to define better the accuracy and potential clinical use of this method.

Adenocarcinoma↗
PubMed1991

Quantitative evaluation of regional substrate metabolism in the human heart by positron emission tomography.

Meaning interpretation of metabolic images obtained by positron emission tomography for evaluation of cardiac disease requires a knowledge of the normal variation in regional myocardial substrate metabolism. Recent studies with fluorine-18 (F-18) fluorodeoxyglucose suggest inhomogeneity of myocardial glucose metabolism in the normal human heart, which may relate to substrate availability. Therefore, quantitative evaluation of myocardial oxidative metabolism and glucose metabolism, as derived by dynamic positron emission tomography with carbon-11 (C-11) acetate and F-18 fluorodeoxyglucose, was performed in nine healthy male volunteers. All were studied under tightly controlled metabolic conditions of hyperinsulinemic-euglycemic clamping with and without a concurrent lipid emulsion infusion. Significant inhomogeneity of regional glucose metabolism was noted although it was less than that described under fasting conditions. Glucose utilization was 13% lower in the septum compared with the lateral wall both without and with lipid infusion (0.34 vs. 0.39 mumol/g per min, respectively, p less than 0.05; and 0.33 vs. 0.38 mumol/g per min, respectively, (p less than 0.05). Relatively decreased septal glucose utilization could not be explained by decreased metabolic demand because C-11 clearance constants were marginally higher in the septum than in the lateral wall in both studies (0.055 vs. 0.054 per min, respectively, p = NS; and 0.061 vs. 0.056 per min, respectively, p less than 0.05). Relatively decreased septal glucose utilization could reflect regional variation in substrate use and possible preferential free fatty acid utilization by the septum. These data provide a useful framework for assessing altered cardiac metabolism in disease and support standardization of metabolic conditions during metabolic imaging with positron emission tomography.

Acetates↗
PubMed1990

Effect of regional myocardial ischemia on sympathetic nervous system as assessed by fluorine-18-metaraminol.

With the introduction of radiolabeled catecholamine analogues, the noninvasive evaluation of the cardiac sympathetic nervous system has become possible. This study evaluated the effect of regional ischemia on myocardial retention of the new norepinephrine analogue 6-[18F] fluorometaraminol (FMR) in the open chest dog model. Six dogs were injected intravenously with FMR following 30-min occlusion of the left anterior descending artery. Six sham animals served as control group. Regional myocardial blood flow as determined by microspheres decreased 87% during ischemia (p less than 0.01), but was not significantly different from control myocardium following reperfusion. Regional myocardial 18F activity as determined postmortem was significantly reduced in reperfused myocardium (-34%), which paralleled an 18% reduction of tissue norepinephrine concentration. Thus, short time periods of coronary occlusion affect neuronal function indicating the sensitivity of the sympathetic nerve terminals to ischemia. FMR provides a new tracer approach for the characterization of neuronal integrity in postischemic myocardium.

Animals↗
PubMed1979

The pregnant Syrian hamster as a model to study intravascular trophoblasts and associated maternal blood vessel changes.

In pregnant Syrian hamsters (Mesocricetus auratus) used as an animal model for studying the migration of fetal trophoblasts and the associated changes in maternal blood vessels, intravascular trophoblasts migrated well beyond the blood vessels of the uterus and into the vessels of the mesometrium. They migrated beyond the decidua of the uterus, into the lumina of maternal uterine and mesometrial arteries, but not into veins. The arterial changes, which were often segmental, resembled those seen in the decidua and consisted of a replacement of normal smooth muscle cells by poorly differentiated stromal cells. Ultrastructurally, the trophoblasts were either above or below maternal endothelial cells. They occurred also as single or multiple layers within the lumina of arteries that lacked an endothelial lining. Apparent penetration of the elastic membrane by the fetal trophoblasts brought them into close apposition to maternal cells in the arterial wall. Histochemical studies showed heightened metabolic activity of the intravascular trophoblasts as suggested by strong histochemical reactions to nonspecific esterase, succinic dehydrogenase and the glycerophosphate dehydrogenase reactions. Thus, these metabolically active fetal trophoblasts actively migrate into the maternal arterial system, resulting in loss of endothelial cells and changes in the wall of the maternal arteries similar to those in the decidua at the uteroplacental junction.

Animals↗
PubMed1975

Vascular interdependence in postmortem human lungs.

Interdependence of arteries and the surrounding lung was estimated in excised, postmortem human lungs. At low vascular pressures, vessel diameter increased as the lung was inflated. At high vascular pressures, vessel diameter decreased as the lung was inflated. Compared to the effects of interdependence in excised dog lobes, those in human lungs at low transpulmonary pressures were small. The following conclusions were reached: (1) the diameter of intrapulmonary arteries is stabilized (more constant with changes in intravascular pressure) when the lung has a high transpulmonary pressure; (2) increases in pulmonary vascular resistance at high lung volumes may be related to extra-alveolar, as well as intra-alveolar, vessel compression; (3) interdependence in human lungs differs markedly from interdependence in dog lungs.

Adolescent↗