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PubMed1989

Current diagnostic imaging modalities of the liver.

Although there are many complementary and supplementary types of diagnostic imaging of the liver, a logical sequence for most liver pathology begins with high-quality ultrasound. It is noninvasive and inexpensive but very operator dependent. In other settings, CT may be the preferable screening modality, as it gives an excellent picture of the global anatomy and is easily reproducible. Frequently, the two modalities are complementary and indicated; on other occasions, one method will suffice. Radionuclide evaluation of the liver is usually reserved for hepatobiliary imaging for biliary obstruction or the question of acute cholecystitis and tagged-red cell scanning for hemangioma. It is also frequently used for gallium scanning in hepatoma, but lymphoma and inflammatory diseases are also gallium avid. The invasive imaging tests of the liver--angiography and transhepatic and endoscopic retrograde cholangiography--are performed when insufficient information is obtained by the other methods (as in diagnostic transhepatic cholangiography) or when the procedure offers therapy (as for biliary drainage, percutaneous transhepatic removal of common bile duct stones, percutaneous cholecystosis with gallstone dissolution and liver embolization, or the angiographic evaluation for portal shunting or liver resection). The impact of magnetic resonance imaging and fourth-generation raid angiotomography CT scanning has yet to be felt. The use of intraoperative ultrasound is to be encouraged prior to liver resection because it can demonstrate lesions as small as 3 mm in diameter.

Angiography↗
PubMed1987

Noninvasive evaluation of right ventricular function.

Numerous technologic advances have greatly facilitated the noninvasive analysis of right ventricular function. Nevertheless, important clues continue to be available to the astute clinician by physical examination. The chest x-ray is of rather limited utility. The electrocardiogram can show evidence of right atrial enlargement or right ventricular hypertrophy. Unfortunately, both sensitivity and specificity are deficient. Echocardiography is a widely available and potentially very accurate source of information concerning right ventricular dysfunction. Careful temporal analysis of the M-mode echocardiogram can give information beyond chamber size and wall thickness. Two-dimensional echocardiography allows more accurate determination of chamber size and wall thickness and also permits analysis of segmental wall motion and chamber contour. Doppler echocardiography allows measurement of pressure differences and flow kinetics. Preliminary data indicate that one can accurately assess pulmonary artery pressure and possibly right ventricular diastolic function. Color-flow mapping allows for accurate determination of valvular regurgitation and enhances the accuracy of standard Doppler echocardiographic techniques. Radionuclide analysis of the right ventricle by blood-pool imaging allows accurate determination of ejection fraction and wall motion. In addition, it may be possible to estimate pulmonary artery pressure. Use of short-acting radionuclides allows for serial imaging of the right ventricle after pharmacologic intervention or exercise. Perfusion scanning can show evidence of exercise-induced ischemia, although applicability to the right ventricle is somewhat limited. Avid scanning allows localizing of myocardial injury to the right ventricle. CT scanning of the heart is of limited clinical utility, because cardiac motion occurs too rapidly for accurate imaging. The advent of the cine-CT may overcome this problem and allow evaluation of right ventricular volumes and wall motion. Digital subtraction imaging allows for accurate video densitometric calculation of ejection fractions, but offers no advantage over other currently available techniques. Magnetic resonance imaging may prove to be the methodology of choice for analysis of right ventricular function, because it can give accurate measurement of right ventricular wall motion, ejection fraction, and (similar to Doppler flow studies) some indication of flow within the right-sided chambers. It will soon be possible to generate information concerning the biochemical content of the right ventricular myocardium, perhaps providing early evidence of hypertrophy or myopathy.(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiac Output↗
PubMedDate not supplied

Cardiac phase: amplitude analysis using macro programming.

The analysis of EKG gated radionuclide cardiac imaging data with Fourier amplitude and phase images is becoming a valuable clinical technique, demonstrating location, size, and severity of regional ventricular abnormalities. Not all commercially available nuclear medicine computer systems offer software for phase and amplitude analysis; however, many systems do have the capability of linear image arithmetic using simple macro commands which can easily by sequenced into stored macro-strings or programs. Using simple but accurate series approximations for the Fourier operations, macro programs have been written for a Digital Equipment Corporation Gamma-11 system to obtain phase and amplitude images from routine gated cardiac studies. In addition, dynamic cine-mode presentation of the onset of mechanical systole is generated from the phase data, using only a second set of macro programs. This approach is easily adapted to different data acquisition protocols, and can be used on any system with macro commands for image arithmetic.

Computers↗
PubMed1991

CBF measured by Xe-CT: approach to analysis and normal values.

Normal reference values and a practical approach to CBF analysis are needed for routine clinical analysis and interpretation of xenon-enhanced computed tomography (CT) CBF studies. We measured CBF in 67 normal individuals with the GE 9800 CT scanner adapted for CBF imaging with stable Xe. CBF values for vascular territories were systematically analyzed using the clustering of contiguous 2-cm circular regions of interest (ROIs) placed within the cortical mantle and basal ganglia. Mixed cortical flows averaged 51 +/- 10ml.100g-1.min-1. High and low flow compartments, sampled by placing 5-mm circular ROIs in regions containing the highest and lowest flow values in each hemisphere, averaged 84 +/- 14 and 20 +/- 5 ml.100 g-1.min-1, respectively. Mixed cortical flow values as well as values within the high flow compartment demonstrated significant decline with age; however, there were no significant age-related changes in the low flow compartment. The clustering of systematically placed cortical and subcortical ROIs has provided a normative data base for Xe-CT CBF and a flexible and uncomplicated method for the analysis of CBF maps generated by Xe-enhanced CT.

Adult↗
PubMed1985

Patient motion artifacts on scintigraphic gastric emptying studies.

Patient motion during scintigraphic gastric emptying studies can result in the false diagnosis of gastroesophageal reflux or of accelerated gastric emptying. A simple means of detecting patient motion, by generating a time-activity curve from a region of interest drawn about a Tc-99m marker, is described.

Esophagus↗
PubMed1982

Functional imaging in the early diagnosis of dysbaric osteonecrosis.

Eight divers who developed permanent scintigraphic bone changes following dives to various depths took part in a study to determine the nature of these lesions. Only one of these divers had radiologically evident bone changes in his scintigraphic lesion. Dynamic scintigrams of the bones containing the lesions were obtained from all eight divers and functional images generated of both amplitude (osteoblastic activity) and accretion (microvasculature) rate constants. All had increased amplitude in the area of the scintigraphic lesion indicating continuing osteoblastic activity. Three divers showed a decreased accretion rate in the lesions, indicating impairment or absence of local microcirculation; one of these was the diver who showed radiological changes prior to the study and the other two subsequently developed radiologically evident osteonecrosis. It is concluded that functional images, generated from dynamic bone scintigrams, can successfully predict dysbaric osteonecrosis.

Barotrauma↗
PubMed1993

Beta camera low activity tumor imaging.

A new technique, the beta camera, to complement film autoradiography, with fast quantitative imaging of beta particle-emitting radionuclides has been developed. It consists of a thin plastic scintillator and a light-sensitive microchannel plate detector. The thin tissue sample is mounted on the scintillator. Our first system had a high background and a moderate spatial resolution of 900 microns. We now report an improved system with a photomultiplier tube mounted on the scintillator of the microchannel plate detector. Only events registered by both detectors are accepted. A fast coincidence unit processes the signals, and if a time overlap exists, an event is generated in the beta camera. In the coincidence mode, images with low activity distribution of 201Tl (count rate 1 s-1) in 50 microns-thick slices of a human glioma tumor could be recorded with a spatial resolution of 500 microns.

Brain Neoplasms↗
PubMed1990

Direct simultaneous production of [15O]water and [13N]ammonia or [18F]fluoride ion by 26 MeV proton irradiation of a double chamber water target.

A simple double liquid chamber target was developed to provide the option for simultaneous production of [15O]H2O and either 13N or 18F using a single proton beam. Irradiation of natural water in a thin aluminium front chamber produced [15O]H2O by the 16O(p, pn)15O reaction directly. Large (0.5-1.0 Ci) doses of sterile [15O]H2O (greater than 99.95% radionuclide purity) were routinely prepared in 1 min from end of 20 microA bombardments using this target and an in-line mixed bed ion exchange column purification. Water in the thin front chamber degraded proton energies on exit to 20-18 MeV. The rear silver liquid chamber was threefold thick to 17 MeV protons in water and it efficiently produced either 13N by the 16O(p, alpha)13N reaction or [18F]fluoride ion by the 18O(p, n)18F reaction. Both target chambers were overpressurized with at least 6 atm of gas to minimize boiling/cavitation of water at high beam currents. Using hydrogen as the overpressure gas on the back chamber and an in-line anion exchange column radionuclidic cleanup process, high yields of sterile, aqueous [13N]NH3 (40-200 mCi; 20 microA) were produced directly from the back chamber at the same time that [15O]H2O was being produced from the front chamber. The combination of this target system with a cyclotron capable of generating 26-30 MeV protons provides great flexibility and simplicity for rapid, high volume production of the three best validated and most widely used radiopharmaceuticals at the present time in clinical positron emission tomography: [15O]H2O, [13N]NH3 and [18F]FDG.

Ammonia↗
PubMed1987

[Perspectives in the use of monoclonal antibodies in the therapy of neoplastic diseases].

In order to improve the efficiency of monoclonal antibodies against tumor-associated antigens, conjugates with toxins, cytostatics or radionuclides have been tested. Furthermore, antibody genes or gene segments can be altered or exchanged to reach enhanced specificity or novel biological functions of immunoglobulin molecules. In addition, monoclonal antibodies have been used recently for the direction, stimulation and activation of T lymphocytes, which are able to generate cytolytic potential against tumor cells. In this study we demonstrate selective activation and expansion of T-cell subpopulations by cross-linking the T-cell receptor complex with other differentiation antigens.

Antibodies, Monoclonal↗
PubMed2003

Generation and stability of bentonite colloids at the bentonite/granite interface of a deep geological radioactive waste repository.

The possible mechanisms of colloid generation at the near field/far field interface of a radioactive repository have been investigated by means of novel column experiments simulating the granite/bentonite boundary, both in dynamic and in quasi-static water flow conditions. It has been shown that solid particles and colloids can be detached from the bulk and mobilised by the water flow. The higher the flow rate, the higher the concentration of particles found in the water, according to an erosion process. However, the gel formation and the intrinsic tactoid structure of the clay play an important role in the submicron particle generation even in the compacted clay and in a confined system. In fact, once a bentonite gel is formed, in the regions where the clay is contacted with water, clay colloids can be formed even in quasi-static flow conditions. The potential relevance of these colloids in radionuclide transport has been studied by evaluating their stability in different chemical environments. The coagulation kinetics of natural bentonite colloids was experimentally studied as a function of the ionic strength and pH, by means of time-resolved light scattering techniques. It has been shown that these colloids are very stable in low saline (approximately 1 x 10(-3) M) and alkaline (pH > or = 8) waters.

Aluminum Silicates↗
PubMed2001

Effect of fluoxetine on regional cerebral metabolism in autistic spectrum disorders: a pilot study.

The regional metabolic effects of fluoxetine were examined in patients with autism spectrum disorders. Six adult patients with DSM-IV and Autism Diagnostic Interview (ADI) diagnoses of autism (n = 5) and Asperger's syndrome (n = 1), entered a 16-wk placebo-controlled cross-over trial of fluoxetine. The patients received (18)F-deoxyglucose positron emission tomography with co-registered magnetic resonance imaging at baseline and at the end of the period of fluoxetine administration. After treatment, the patients showed significant improvement on the scores of the Yale--Brown Obsessive--Compulsive Scale -- Obsessions subscale and the Hamilton Anxiety Scale; Clinical Global Impressions -- Autism scores showed 3 of the patients much improved and 3 unchanged. Relative metabolic rates were significantly higher in the right frontal lobe following fluoxetine, especially in the anterior cingulate gyrus and the orbitofrontal cortex. Patients with higher metabolic rates in the medial frontal region and anterior cingulate when unmedicated were more likely to respond favourably to fluoxetine. These results are consistent with those in depression indicating that higher cingulate gyrus metabolic rates at baseline predict SRI response.

Adult↗
PubMed1994

A clinical rule to predict preserved left ventricular ejection fraction in patients after myocardial infarction.

OBJECTIVE: To derive and validate a clinical prediction rule that identifies patients after myocardial infarction who have preserved left ventricular systolic function. DESIGN: Retrospective analysis of a prospective cohort study, with a derivation set to generate a clinical prediction rule and a validation set to test the prediction rule. SETTING: Urban tertiary care hospital. PATIENTS: 314 consecutive patients admitted with myocardial infarction who had one or more of the following tests to determine left ventricular ejection fraction: transthoracic echocardiography, contrast left ventriculography, or radionuclide ventriculography. MEASUREMENTS: Left ventricular ejection fractions were determined by transthoracic echocardiography, contrast left ventriculography, and gated blood pool scan. RESULTS: Multivariate analysis of patients in the derivation set yielded the following rule: The left ventricular ejection fraction is predicted to be 40% or more in patients who have 1) an interpretable electrocardiogram, 2) no previous Q-wave myocardial infarction, 3) no history of congestive heart failure, and 4) an index myocardial infarction that is not a Q-wave anterior infarction. In the derivation and the validation sets, the positive predictive value of the prediction rule was more than 0.98. CONCLUSIONS: A simple clinical prediction rule using easily obtained historical and electrocardiographic data reliably identifies a substantial percentage of patients after myocardial infarction (40% in our hospital) who are likely to have preserved left ventricular systolic function. If validated in other patient populations, application of this prediction rule in clinical practice could result in a substantial decrease in the cost of treating uncomplicated myocardial infarction.

Aged↗
PubMed1988

Dynamic ventilation scintigraphy: a comparison of parameter estimation gating models.

Two procedures for providing the synchronization of ventilation scintigraphic data to create dynamic displays of the pulmonary cycle are described and compared. These techniques are based on estimating instantaneous lung volume by pneumotachometry and by scintigraphy. Twenty-three patients were studied by these two techniques. The results indicate that the estimation of the times of end-inspiration and end-expiration are equivalent by the two techniques but the morphologies of the two estimated time-volume waveforms are not equivalent. Ventilation cinescintigraphy based on time division gating but not on isovolume division gating can be equivalently generated from list mode acquired data by employing either technique described.

Humans↗
PubMed1986

Miniature thermoluminescent dosimeter absorbed dose measurements in tumor phantom models.

Miniature teflon-imbedded CaSO4:Dy thermoluminescent dosimeter(s) (TLD) have been sized and cut to fit inside a syringe needle. These dosimeters have been shown to be linear in response to beta and high energy gamma radiation. This allows for their direct implantation into tumor-bearing animals undergoing radioimmunotherapy and subsequent measurement of dose deposition on a per organ basis. In order to perform these radiolabeled antibody dose measurements with sufficient accuracy, static calibration data must first be generated. Consequently, phantom models were constructed with artificial tumors of diameters ranging from 3-30 mm contained in a surrounding tissue equivalent medium. The TLD were used to characterize dose distributions in a radial direction from the center of the cylindrical tumor volumes containing 131I, 32P, or 90Y radionuclides. Absorbed dose measurements in the boundary region between tumor and outer medium were found to be dependent on the: tumor specific activity, average range of the beta radiation, and radial tumor dimensions.

Antibodies, Monoclonal↗
PubMed1981

[Ventilation studies of the lung with krypton-81m].

During a 2-year study period it was found that krypton-81m was useful in routine clinical practice. During this period 1563 technetium-99m perfusion studies and 807 krypton-81m ventilation studies were performed. A distinct advantage of krypton-81m was the ease with which multiple views could be obtained. These views could be directly compared with those of preceding perfusion studies. However, interruptions in the regular supply of rubidium-81/krypton-81m generators affected 17,1% of perfusion studies and xenon-127 should be a suitable substitute for these periods.

Humans↗
PubMed1997

[Diagnostic possibilities of left ventricular systolic-diastolic volume curve computed in patients with vascular diseases by means of multigated radionuclide angiocardiography].

MATERIALS AND METHODS: In this study the multigated radionuclide angiography was performed in 54 patients with and without vascular diseases; the humeral arterial pressure was measured and the BMI was calculated in each patient by mean of the weight and height. The curve expressing the variations of the sisto diastolic volume of the left ventricle was generated from an analysis of the radioisotopic angiocardiography, and the curve, the BMI and the arterial pressure were used to calculate 14 different numeric values for each patient consisting of hemodynamic parameters of the left ventricular function. The diagnosis for each patient was then examined a posteriori and the patients were divided in 15 groups of which 1 with non-cardiovascular pathologies and 14 with cardiovascular pathologies alone or in association. A statistical analysis was performed to ascertain whether the parameters could be used to classify patients into the diagnostic groups using the Fisher's discriminant analysis. RESULTS: The obtained classification agreed in the 63% of the cases. CONCLUSIONS: This paper proved the possibility offered by the curve expressing the changes in the sisto diastolic volume of the left ventricle to discriminate between the various cardiovascular pathologies.

Adult↗
PubMedDate not supplied

[Modeling of different types of size-effect in accumulation of 137Cs in fish from the cooling pond of the Chernobyl Power Plant].

All known types of size-effect in accumulation of radiocesium in fish are described on the basis of the dynamic model of distribution and migration of the radionuclide in aquatic ecosystem. The time-dependent activity of 137Cs in different age classes of carp and pike-perch from the Chernobyl Nuclear Power Plant Cooling Pond is calculated. It is shown that during the first year after the accident the activity of 137Cs in the young generations of fish was higher (negative size-effect) owing to higher feeding rate of young fish. During the following years the increase of activity in the older fish generations takes place (positive size-effect). It is shown that size-dependence is more clear for the predatory species.

Animals↗
PubMed1978

Ventricular volume in man computed from CAT scans.

A new interactive computers has been developed to measure ventricular volume from CAT scans. Testing this system on phantoms demonstrated an accuracy to within 16%. Then a series of scans of patients with obstructive hydrocephalus was analyzed using both tradional linear measures and the computer method. None of the traditional measures were directly proportional to the calculated volume. The area measure of ventricular volume correlated well with the computer-generated values. Clinical studies which attempt to quantitate ventricular volume should use a computerized or planigraphic measure.

Cerebral Ventricles↗