Biomedical subjects

J H Clorius

Publications and source records attributed to J H Clorius.

At least 37 records · Page 2Linked to original sources

PubMed1991

Renovascular hypertension: predicting surgical cure with exercise renography.

Renal artery stenosis with resultant renovascular hypertension has attracted clinical attention because the disease is potentially curable and because numerous diagnostic and therapeutic modalities compete for clinical acceptance. An exercise-mediated disturbance of renal hippurate transport was recently described, and has been implicated as having a role in nephrogenic fixed hypertension. To predict the final course of renovascular hypertension before operation we carried out a prospective study with the goal of verifying the predictive value of exercise hippurate scintigraphy. The study was to test the hypothesis that patients with disturbance of renal hippurate transport (pathologic renogram) induced by exercise would have stabilized hypertension and would continue to be hypertensive after operation. Thirty-one patients with hypertension who had unilateral or bilateral renovascular stenosis documented on angiography were referred to rest and exercise hippurate scintigrams before operation. The results of the examinations at rest served as standard and were compared with the exercise scintigrams. In 19 of the 31 (61%) patients a disturbance of transrenal hippurate transport evolved during exercise, whereas 12 (39%) patients failed to respond to exercise with altered hippurate kinetics. Twenty-six patients went on to renovascular operations; five had percutaneous transluminal angioplasty. Revascularization results differed markedly when the blood pressure response of patients with positive results on exercise (abnormal) and patients with negative results on exercise (normal) were compared. Ten of 12 patients with hypertension who had normal exercise renograms were cured. In comparison, blood pressure values were little influenced by therapy in patients with an abnormal response, where 17 of 19 patients continued to have hypertensive disease after therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗

PubMed1991

Renal studies in nuclear medicine.

Research in nephrologic nuclear medicine is presently concentrated in two well-defined areas: interventional procedures and the use of mercaptoacetyltriglycine. The ongoing evaluation of mercaptoacetyltriglycine continues to be a source of interesting research activity, with the distribution volume and the extent of hepatic excretion remaining points of discussion. This tracer permits quantitative determination of renal function. As an imaging agent, mercaptoacetyltriglycine compares favorably with hippurate and with diethylenetriamine penta-acetic acid, particularly in evaluating renal insufficiency. Renal function studies obtained during pharmacologic or physiologic intervention dominate research in hypertension and obstructive uropathy. Angiotensin-converting enzyme inhibition improved the renographic detection of renovascular lesions. Interventional renography with angiotensin-converting enzyme inhibition or ergometric exercise were both capable of generating useful prognostic data on the posttherapy blood pressure response in patients with renovascular hypertension. Interventional diuretic renography with furosemide permits surgical intervention to be reserved for organs at immediate risk because the degree of obstruction and the extent of renal function compromise are easily recognized.

Blood Pressure↗

PubMed1990

Investigations concerning the potential for using 1H NMR relaxometry or high-resolution spectroscopy of plasma as a screening test for malignant lung disease.

In 158 plasma samples, obtained from patients with lung carcinoma, lung metastases, and infectious or inflammatory lung diseases and from healthy controls, the NMR relaxation times T1 and T2 of water protons were measured at a resonance frequency of 20 MHz by pulsed NMR techniques and adjusted to a standardized total plasma protein concentration. For one-third of these samples water-suppressed 500-MHz 1H NMR spectroscopy at 37 degrees C was used (a) to determine the widths of the composite lipid methyl and methylene signals, and (b) to quantitate individual lipid methylene signal components that could be detected in resolution-enhanced spectra. In addition, hematological parameters and the plasma levels of several acute phase proteins and apolipoprotein-A were monitored. No diagnostically significant differences between lung carcinoma patients and patients with nonmalignant lung disease could be found for any of the plasma NMR parameters, nor could T1 or lipid linewidth data distinguish between any patient group and healthy controls. However, the mean T2 was significantly shortened by about 15% for any kind of lung disease compared to healthy controls. Similar but less significant results were found for apolipoprotein-A levels. A linear discriminant function, calculated from the apolipoprotein-A and T2 data, did not improve the differentiation between malignant and nonmalignant lung disease but did improve the discrimination between tumor patients and healthy controls up to a sensitivity and specificity of 80 and 96.5%, respectively. T2 correlates inversely with plasma fibrinogen levels and the blood sedimentation rate and, therefore, appears to monitor a general inflammatory status of a tumor patient rather than the presence or absence of cancer. For all groups except healthy pregnant women, the lipid methylene composite signal linewidth correlates inversely with the fraction of mobile triglyceride present (mainly as VLDL), as estimated from resolution-enhanced spectra.

Blood Proteins↗

PubMed1990

[Bronchial carcinoma. Nuclear medical diagnosis].

The primary indication for scintigraphy in the patient with bronchogenic carcinoma occurs during therapy planning, when scintigrams are obtained to prognosticate post-operative lung function. Ventilation and perfusion scintigrams are the procedures of choice for regional evaluation of lung function. Numerous radioisotope procedures have been introduced for recognition and evaluation of bronchogenic malignancies. In spite of the array of interesting diagnostic approaches, nuclear medicine has failed to reach a prominent position in the diagnostic evaluation of these malignancies. The limits and special indications for using scintigraphic procedures are discussed.

Carcinoma, Bronchogenic↗

PubMed1989

[Lung perfusion-ventilation scintigraphy in squamous cell carcinoma of the lung].

The effect of tumour size, as determined surgically, and tumour position, as determined by bronchoscopy, on ventilation and perfusion scintigraphy was examined in 53 patients with squamous cell carcinomas of the lung. The findings were compared with reduction in one-second-capacity. Central tumours were frequently associated with marked reduction in perfusion. In these patients there was a linear positive correlation between ventilation and one-second-capacity. The reduction in perfusion, and the need to measure this, became with more peripheral tumours. There was a correlation between ventilation and tumour size in patients with V/Q quotient of greater than 1.2. The results show that tumour size and position do not necessarily indicate operability. For planning surgery of central tumours, perfusion scintigraphy therefore occupies an important position.

Aged↗

PubMed1989

Recurrence of colorectal tumors: PET evaluation.

Positron emission tomography (PET) was used in the follow-up of patients with colorectal malignancies to differentiate between recurrent colorectal tumor and scar. Patients were examined with oxygen-15-labeled water and with fluorine-18-labeled deoxyglucose (FDG). FDG was injected intravenously to assess tumor metabolism. The tracer concentration was quantitatively evaluated by means of a region-of-interest technique and standardized for both injected dose and body volume. Of 29 patients, 21 had recurrent colorectal malignancy, and eight had a nonmalignant mass. All malignancies were seen on the PET cross sections. Nonmalignant lesions had a low FDG accumulation on images obtained 60 minutes after injection. While the tumor-soft tissue ratio was highest shortly after the intravenous injection of FDG, the tumor-scar ratio was highest 60 minutes after injection. It was possible to differentiate tumor from non-malignant tissue with FDG with the use of standardized concentration values and tumor-soft tissue ratios. Imaging with O-15-labeled water gave no additional information.

Adult↗

PubMed1989

[Positron emission tomography following brief infusion of 5-[18F]uracil: linear model for the kinetics of 18F radioactivity in tumors].

Patients with a colorectal malignancy were examined with a total body positron emission tomography, immediately following a brief infusion of 5-[18F]uracil. The radioactivity in normal liver tissue and in liver metastasis was monitored for two hours after infusion of the radiotracer. A kinetic model is described which permits calculation of the probable tissue concentration of 5-fluorouracil (FU) and its metabolites. Prerequisite for the model is that the time dependent plasma concentration of FU is known. It is hoped that such analysis will help predict therapeutic response, and permit evaluation of the kinetic consequences of different methods of drug application.

Colonic Neoplasms↗

PubMed1989

Imaging positron emitting radionuclides generated during radiation therapy.

In vivo generated positron emitting radioisotopes, primarily C-11 and N-13, have been documented following therapy with accelerators larger than 10 MeV. Six patients had positron emission tomography 15 to 25 minutes after radiation therapy with a 42 MeV accelerator. Five patients had recurrent colorectal malignancy, and one required therapy for a carcinoma of the common bile duct. We sought to determine whether state-of-the-art PET technology could be used to monitor the three-dimensional activity distribution of radiation-induced radioactivity. At the time of the examination all six patients had sufficient concentrations of C-11 and N-13 activity in the irradiated volume to permit the evaluation of the activity distribution. We found significant activity at the body surface, which permitted field delineation. We conclude that the in vivo generated radioactivity can be monitored with PET.

Aged↗

PubMed1988

Parametric imaging of blood flow.

The calculation of functional images was based on recorded fluoroscopic sequences. The Fourier coefficients of the first harmonic were calculated for each matrix element, and the amplitude and phase values were used for the generation of two synthetic images. The amplitude image demonstrated the maximum change in opacification with high image contrast. Phantom studies showed that a high correlation exists between the inverse phase differences and flow. The clinical application of the Fourier method revealed substantial additional information to conventional angiography in one of ten patients. While the morphological evaluation demonstrated no significant stenosis, the functional images showed a residual stenosis.

Algorithms↗

PubMed1987

NMR relaxation times T1 and T2 of water in plasma from patients with lung carcinoma: correlation of T2 with blood sedimentation rate.

The T1 and T2 NMR relaxation times of water protons in plasma, obtained from patients with lung carcinoma, healthy volunteers, and patients with nontumor diseases were measured at a resonance frequency of 20 MHz. Additionally hematologic parameters were determined. In tumor patients the mean plasma T2 was shortened by about 20%, and an increase in the blood sedimentation rate (BSR) was noted. Similar but less pronounced results were found for the nontumor group of patients, indicating that the shortening of T2 in plasma is a secondary host response. However, a plot of plasma 1/T2 versus BSR from tumor patients showed a significant correlation between these two parameters. No such correlation could be detected in the nontumor group of patients. The correlation of 1/T2 with BSR, found solely in the tumor patient group, increased the diagnostic sensitivity of T2 measurements and may help to differentiate between malignant and nonmalignant disease. No significant variation in the T1 spin-lattice relaxation time was observed.

Adult↗

PubMed1987

Predictive value of exercise renography for presurgical evaluation of nephrogenic hypertension.

Functional omicron-iodohippurate scintigrams were obtained in 18 hypertensive patients. Each patient was examined in the prone position and during exercise. An exercise-induced transient, bilateral, hippurate transport disturbance was sought as an expression of an exercise-mediated cortical perfusion abnormality. The study sought to test the hypothesis that patients who present evidence for an exercise-induced renal perfusion disturbance would have stabilized hypertension that was no longer surgically curable because of morphological changes of the peripheral vasculature. All 18 patients continued on to therapy: 13 proceeded to renovascular reconstructive surgery, 2 had a unilateral nephrectomy, and 3 were treated with percutaneous transluminal renal angioplasty. During preoperative exercise renography, evidence of bilateral renal dysfunction developed in 10 of 18 hypertensive patients during ergometric stress (abnormal exercise response). Following surgical therapy nine of these patients with abnormal exercise scintigrams continued to have hypertensive disease, while one patient was cured. The exercise renograms of eight hypertensive patients were not influenced by the exercise protocol, and operation cured seven of these eight patients. The results suggest that an accentuated vascular response to exercise occurs in the maintenance phase of renovascular hypertension, a disturbance not observed while the hypertension is curable by surgical therapy.

Antihypertensive Agents↗

PubMed1987

Clinical evaluation of patients with hypertension and exercise-induced renal dysfunction.

An exercise-mediated renal omicron-iodohippurate transport abnormality was recently identified in patients with hypertension. The disturbance was not observed in normotensive controls. To learn more about this transient functional disturbance of the kidney, we obtained gamma camera hippurate renograms in 45 patients with hypertension. The final diagnoses indicated that 27 patients had essential hypertension, 15 had renal parenchymal or renovascular hypertension, 2 had malignant hypertension, and 1 had hypertension of pregnancy. We documented age, height, weight, global and unilateral renal function, blood pressure status, and antihypertensive medication used at time of scintigraphy. We also noted the serum catecholamine, sodium, and potassium levels. All patients were scintigraphed at rest and during exercise. The scintigraphic examination documented exercise-induced renal dysfunction in 28 (62%) patients (abnormal exercise renogram), while 17 (38%) had renograms not noticeably influenced by the exercise protocol (normal exercise renogram). When the results of scintigraphy were compared with the clinical data, a weak correlation was found between patient overweight and an abnormal response to exercise. There was no significant difference between groups with normal and abnormal exercise renograms with respect to the other parameters assessed. Exercise renography was not useful for differentiating renal and essential hypertension. Renography appears to demonstrate an exercise-mediated, transient, renal perfusion disturbance in certain patients with hypertension. The examination appears to assess a new parameter in hypertensive disease. Thus, the gamma camera renogram should be reevaluated in the patient with hypertension.

Adolescent↗

PubMed1986

Evaluation of scintigraphic data of renal transplants.

Scintigraphic data obtained during 594 examinations of renal transplants were evaluated by an experienced physician. Each examination included both the measurement of a radioiodine hippurate uptake curve, and a technetium 99m diethylenetriamine pentaacetic acid (DTPA) time-activity curve describing renal perfusion. Features were extracted from both curves. Discriminant analysis of the features resulted in a computer classification of the grafts. This classification was compared with the physician's diagnosis. Congruence between the computer classification and the diagnosis supported the diagnosis, and revealed those features which were able to lead to the correct diagnosis. The analysis was used to assess graft function, and to identify acute tubular necrosis and acute, as well as chronic, rejection. The computer classification was in agreement with the diagnosis in about 80% of the acute rejections, in 86% of all instances of acute tubular necrosis, and in 80% of chronic rejections. The procedure can be used to mutually improve the diagnosis of both physician and computer.

Acute Disease↗

PubMed1986

Computer processed fluoroscopic images for digital intravenous renal angiography.

We investigated intravenous digital angiography using computer processed fluoroscopic images. Computer processed fluoroscopy (CPF) was compared to conventional digital subtraction angiography (DSA) in 39 patients referred for renal vessel evaluation. For assessment of CPF the anterior-posterior images were compared with the corresponding digital subtraction angiograms. 79% percent of DSA and 71% of CPF studies were diagnostic. Peripheral injection of contrast medium caused deterioration of CPF images. Skin dose measurements were obtained in 24 patients. The median dose for DSA was 8.2 rad, compared to 1.1 rad for CPF. It is concluded that sophisticated algorithms should be investigated for digital angiography, so that high image quality can be achieved with a reduced radiation exposure.

Adult↗

PubMed1985

Renal perfusion and mean vascular transit time.

A method was developed to determine the mean vascular (arterio-venous) transit time (MVTT) of renal transplants. The renal transit times were calculated from perfusion curves obtained when grafts were examined with 99mTc-DTPA. About 400 examinations were performed during a 6-month period. As a result, influences of clinical complications on transit times were demonstrated. It was found that the individual MVTT is not a suitable parameter for assessment of renal grafts since individual transit times vary widely.

Graft Rejection↗

PubMed1985

[Contribution of digital subtraction angiography to the diagnosis of rejection reactions after kidney transplantation].

The ability to diagnose rejection changes in renal transplants using DSA was evaluated retrospectively taking intrarenal vascular changes into consideration. The findings obtained with DSA were compared to those of scintigraphy in 26 graft recipients, on whom both methods had been performed within a narrow time period for evaluation of hypertensive disease. The scintigraphic diagnosis was based on function and perfusion studies. The intrarenal vascular tree was demonstrated on DSA better by intraarterial than by intravenous contrast media injection, however both techniques delivered useful diagnostic information. The status of the graft was evaluated with comparable results by DSA and scintigraphy in 73% of the cases. In our experience, functional effects produced by morphological changes demonstrated by DSA, can be defined better with the help of scintigraphy. On the other hand, by performing DSA it is possible to clarify morphologically functional findings, which may be detected by scintigraphy but often are diagnostically nonspecific. The availability of both morphological and functional data increases the diagnostic accuracy which can be obtained with these two low invasive procedures in the assessment of vascular changes in renal transplants.

Adolescent↗

PubMed1985

Contribution of paramagnetic trace elements to the spin-lattice relaxation time in the liver.

The relaxation times of water protons in rat liver tissue were measured with a NMR spectrometer at 20 MHz. The paramagnetic trace elements Cu, Fe, and Mn were determined by neutron activation analysis. No shortening of T1 could be observed when liver Cu or Fe concentration was increased in the microgram range. T1 was strongly correlated with the liver Mn concentration of untreated animals and animals whose liver Mn concentration was artificially increased or decreased by intravenous injection of manganous acetate or a metal chelating agent with high affinity for hepatobiliary excretion. Deviations from this Mn-T1 correlation were found in the initial phase of liver cirrhosis induced by thioacetamide (elongated T1, normal Mn concentration) and after stimulation of liver growth by phenobarbital (normal T1, decreased Mn concentration). An increased or decreased enhancement factor for Mn may have contributed to the observed deviations during phenobarbital and thioacetamide treatment.

Animals↗

PubMed1985

Estimating the effective renal plasma flow from the hippurate renogram.

A method for estimating the effective renal plasma flow (ERPF) from renograms is presented. Renograms obtained in 91 patients were used to test the method. The clearance values derived from renography were compared with those obtained with infusion clearance. It was shown that the ERPF was able to be estimated from the renogram with a standard error of +/- 94 ml min-1.

Glomerular Filtration Rate↗