Partitioning microbial respiration between jet fuel and native organic matter in an organic-rich long time-contaminated aquifer.

The relative importance of jet fuel biodegradation relative to the respiration of natural organic matter in a contaminated organic-rich aquifer underlying a fire training area at Tyndall Air Force Base, Florida, USA was determined with isotopic measurements. Thirteen wells were sampled and analyzed for BTX (benzene, toluene, xylene), dissolved inorganic carbon (DIC) and CH4 concentrations, and delta13C and 14C of DIC. Results range from non-detectable to 3790 ppb, 1.

Quadricyclane hydration kinetics in natural waters.

Hydration rates of quadricyclane were measured over a pH range of 3 to 8 in phosphate buffer, carbonate buffer, and nitric acid solutions. Norbornadiene was a minor impurity in the quadricyclane, and its hydration rate was also measured. Hydration products were exo-5-norbornen-2-ol (bicyclo[2.

Scintigraphic detection of post-pneumonectomy bronchopleural fistulae.

A total of 20 ventilation studies [16 with xenon-133 and four with technetium-99m diethylenetriamine pentaacetic acid (DTPA)] were performed in 11 patients with suspected post-pneumonectomy bronchopleural fistulae. The findings on the ventilation scan were correlated with bronchoscopy, taken as the gold standard for purposes of comparison. The sensitivity and specificity for 133Xe scans were 83% and 100% respectively, while the sensitivity for 99mTc-DTPA aerosol studies was poor at 0%.

Viable neurons with luxury perfusion in hydrocephalus.

A woman with hydrocephalus due to aqueductal stenosis had functional imaging of cerebral perfusion and metabolism to demonstrate the effects of endoscopic third ventriculostomy--a new form of internal surgical shunting. Technetium-99m-ECD SPECT and 18F-FDG PET showed regional luxury perfusion at the left frontal region. Three months after a successful third ventriculostomy, a repeated imaging of cerebral perfusion and metabolism showed resolution of luxury perfusion and global improvement of both perfusion and metabolism.

Myocardial viability studies using fluorine-18-FDG SPECT: a comparison with fluorine-18-FDG PET.

Unlabelled: Multidetector SPECT systems equipped with a high-energy, or 511-keV collimator, have been proposed to offer a less expensive alternative to PET in myocardial viability studies with [18F]FDG. The objectives of this investigation included: (a) measuring the physical imaging characteristics of SPECT systems equipped with either a high-energy general-purpose collimator (HE), or the dedicated 511-keV collimator (UH), when imaging 511-keV photons, and comparing them with conventional FDG PET; and (b) directly and quantitatively comparing the diagnostic accuracy of SPECT, with either an UH or HE collimator, to that of PET in myocardial viability studies using 18F-FDG.

Methods: Physical imaging characteristics of SPECT and PET were measured and compared.

Regional body FDG-PET in postoperative recurrent hyperparathyroidism.

Purpose: The use of preoperative imaging studies in patients with persistent or recurrent hyperparathyroidism after initial operation is generally accepted to improve the success rate and minimize the morbidity from reoperative surgery. The purpose of this study was to define the performance of FDG-PET for the localization of hyperfunctioning parathyroid tissue prior to reoperation.

Method: Twenty patients with biochemical evidence of recurrent or persistent hyperparathyroidism following previous neck surgery were investigated.

Present assessment of myocardial viability by nuclear imaging.

Prospective delineation of viable from nonviable myocardium in patients with coronary artery disease in an important factor in deciding whether a patient should be revascularized or treated medically. Two common techniques--single-photon emission computed tomography (SPECT) and positron-emission computed tomography (PET)--are used in nuclear medicine using various radiopharmaceuticals for the detection of myocardial viability in patients. Thallium-201 (201Tl) and technetium-99m (99mTc)-sestamibi are the common radiopharmaceuticals used in different protocols using SPECT, whereas fluoride-18 (18F)-fluorodeoxyglucose (FDG) and rubidium-82 (82Rb) are most widely used in PET.

Is image subtraction necessary in the clinical interpretation of single-day split-dose stress cerebral perfusion single-photon emission tomography using technetium-99m compounds?

The aim of this study was to validate a simplified semiquantitative method of evaluating a single-day stress cerebral perfusion test to obtain cerebrovascular reserve capacity (CVRC) for routine clinical uses. A split-dose protocol was tested in 36 pairs of technetium-99m hexamethylpropylene amino oxime baseline (low dose) and acetazolamide (high dose) stress brain single-photon emission tomographic (SPET) studies from 16 patients with cerebrovascular disease. The images were displayed on a semiquantitative color scale with (corrected) and without (uncorrected) image subtraction, dose adjustment, and decay correction.

Measurement of cardiac output with first-pass determination during rubidium-82 PET myocardial perfusion imaging.

In addition to providing useful clinical information, cardiac output determined during rubidium-82 positron emission tomographic (PET) myocardial perfusion studies can be used in the measurement of absolute regional myocardial blood flow using Sapirstein's method. This investigation was conducted to compare cardiac output values obtained by post-processing data acquired in a list mode PET myocardial perfusion study with those obtained using a technetium-99m-labeled red blood cell method on the same patients. Results from 14 patients showed that cardiac output can be accurately measured simultaneously in a 82Rb PET myocardial study, allowing determination of multiple perfusion and functional parameters of the heart, thus improving the cost-effectiveness of the 82Rb PET study.

Outcome of temporal lobe epilepsy surgery predicted by statistical parametric PET imaging.

Unlabelled: PET is useful in the presurgical evaluation of temporal lobe epilepsy. The purpose of this retrospective study is to assess the clinical use of statistical parametric imaging in predicting surgical outcome.

Methods: Interictal 18FDG-PET scans in 17 patients with surgically-treated temporal lobe epilepsy (Group A-13 seizure-free, group B = 4 not seizure-free at 6 mo) were transformed into statistical parametric imaging, with each pixel representing a z-score value by using the mean and s.

The incidence of scintigraphically viable and nonviable tissue by rubidium-82 and fluorine-18-fluorodeoxyglucose positron emission tomographic imaging in patients with prior infarction and left ventricular dysfunction.

Background: Although reversible perfusion defects, perfusion-metabolism mismatch and match patterns are important for differentiating viable from nonviable myocardium, the frequency of these scintigraphic patterns has not been reported. The study objective was to establish the incidence of these scintigraphic patterns to estimate the clinical need for metabolic positron emission tomography for evaluating tissue viability in patients with prior myocardial infarction (MI).

Methods And Results: 82Rb perfusion images were interpreted to identify reversible or irreversible defects, followed by determination of their 18F-fluorodeoxyglucose (18F-FDG) uptake pattern.

Use of positron emission tomography for prediction of perioperative and late cardiac events before vascular surgery.

The efficacy of myocardial perfusion imaging for cardiac-risk stratification of patients undergoing vascular surgery has been disputed recently. In comparison with conventional techniques, positron emission tomography (PET) has the benefit of permitting a true resting scan, allows accurate measurement of the extent of ischemia, and is highly specific for the diagnosis of coronary disease. We therefore investigated the use of PET for risk stratification at the time of vascular surgery and subsequent follow-up in 78 patients (aged 67 +/- 11 years, 52 men), selected for testing before the performance of extensive surgery or because of one or more clinical risk factors.

Hibernating myocardium versus scar: severity of irreversible decreased myocardial perfusion in prediction of tissue viability.

Purpose: To determine whether quantitation of the relative severity of decreased perfusion in irreversible defects on myocardial perfusion images enables differentiation of viable hibernating myocardium from scar.

Materials And Methods: In 145 patients with previous myocardial infarction, 1,252 regions with irreversible defects proved by means of rubidium-82 rest-stress imaging were analyzed for relative severity (percentage decrease in perfusion). Myocardial tissue viability was determined by means of positron emission tomography with fluorine-18 fluorodeoxyglucose (FDG).

Prognosis of patients with left ventricular dysfunction, with and without viable myocardium after myocardial infarction. Relative efficacy of medical therapy and revascularization.

Background: The uptake of F-18 deoxyglucose into dysfunction segments after myocardial infarction identifies metabolically active (FDG+) or inactive (FDG-) myocardium. Although patients with FDG+ segments have been found to be at risk for adverse events, the prognostic significance of viable myocardium in relation to other influences on postinfarction prognosis, including revascularization, remain ill defined. The purpose of this study was to investigate the relative prognostic significance of FDG+ tissue and to establish whether myocardial revascularization in patients with viable tissue attenuates the risk of adverse outcome.

Radiopharmaceuticals for brain imaging.

Brain imaging is performed using radiopharmaceuticals by single photon emission computed tomography (SPECT) and positron emission tomography (PET). SPECT and PET radiopharmaceuticals are classified according to blood-brain-barrier permeability, cerebral perfusion and metabolism receptor-binding, and antigen-antibody binding. The blood-brain-barrier (BBB) SPECT agents, such as 99mTcO4-, [99mTc]DTPA, 201TI and [67Ga]citrate are excluded by normal brain cells, but enter into tumor cells because of altered BBB.

Primary hyperparathyroidism: preoperative parathyroid imaging with regional body FDG PET.

Purpose: To explore the feasibility of use of positron emission tomography (PET) with 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG) to localize abnormal parathyroid tissue.

Materials And Methods: Regional body FDG PET with attenuation correction was performed in 17 adult patients with primary hyperparathyroidism (HPT) prior to surgical neck exploration. The regional body FDG PET results were correlated with surgical and histopathologic findings.

Current status of the clinical applications of cardiac positron emission tomography.

At the present time, positron emission tomography (PET) has evolved into an accurate clinical diagnostic imaging procedure for coronary artery disease that provides unique information, presently unavailable from other imaging modalities, for the management of patients with previous myocardial infarction. The superior accuracy of PET for the diagnosis of coronary artery disease has had a positive influence on the management decision process to perform revascularization. In addition to the superior accuracy of PET compared with single photon emission computed tomography, PET has the advantage of being able to identify viable hibernating myocardium.

Correlation between electron capture negative chemical ionization mass spectrometric fragmentation and calculated internal energies for polychlorinated biphenyls.

Correlationbse tween molecular structure and fragmentation observed in electron capture negative chemical ionization mass spectra (moderator gas = methane) of 49 selected tetrachlorinated, pentachlorinated, and hexachlorinated biphenyls have been investigated by using molecular modeling. The semiempirical general molecular orbital program MOPAC was used to calculate molecular properties for biphenyl and the 209 polychlorinated biphenyls. The mass spectrometric ionization and fragmentation processes were found to be linked to the number of chlorine atoms present on the biphenyl, and to the number of those chlorine atoms in the ortho (2, 2', 6, and 6') positions.

Planar imaging with single-head large-field-of-view cameras: are they still the workhorse?

The large-field-of-view (LFOV) scintillation camera was developed in 1975 with a field of view 50% larger than the conventional camera used at that time. Not only was the new model more adaptable to large-area imaging needs, such as lungs, bone, liver, and spleen, but it could be used for small-organ imaging with a converging collimator that yielded both high resolution and high efficiency. LFOV cameras still offer the most flexibility for all of the common procedures encountered in the nuclear medicine clinic.

Parametric phase display for biventricular function from gated cardiac blood pool single-photon emission tomography.

Complete assessment of biventricular function from planar ECG-gated cardiac blood pool studies has been limited because of the overlap of adjacent activity-containing structures. Theoretically, single-photon emission tomography (SPET) can be used to comprehensively evaluate both ventricles by isolating them from surrounding anatomy. However, an enormous amount of parametric data is generated from gated SPET studies, and much of it is diagnostically irrelevant for ventricular wall motion analysis.

Parathyroid adenoma localization by PET FDG.

A patient with primary hyperparathyroidism was examined with positron emission tomography using [18F]-2-fluorodeoxyglucose. The radioactive tracer accumulated in a cervical mass that proved to be a parathyroid adenoma resulting in the correct preoperative localization of the parathyroid tumor.