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Biomedical subjects

K Kouris

Publications and source records attributed to K Kouris.

At least 37 records · Page 2Linked to original sources
PubMed1990

99mTc DTPA diuretic renography in the evaluation of surgery in chronic schistosomal and non-schistosomal obstructive uropathy.

The selection of patients with chronic obstructive uropathy for surgery is difficult because of problems in identifying true obstruction in a grossly dilated urinary tract. This is especially so in schistosomal (bilharzial) obstructive uropathy. A prospective study of 90 patients (68 with chronic schistosomal and 22 with non-bilharzial obstructive uropathy) was carried out. All patients underwent pre-operative and post-operative radionuclide 99mTc DTPA diuretic renography (RDR). The aims were to assess the value of RDR in the pre- and post-operative management of these patients and whether it could predict the outcome of surgery. Distinctive renogram patterns were identified in patients who required surgical management. These were found useful in monitoring the results and in predicting the outcome of surgery.

Humans↗
PubMed1990

Factors affecting the Gates' measurement of glomerular filtration rate.

The following technical factors affect the Gates' measurement of glomerular filtration rate (GFR): 1) net injected activity, 2) kidney depth, 3) corrected kidney counts. In the syringe measurement prior to injection, self-attenuation causes 16% data loss for a volume of 0.5 ml if the syringe is positioned perpendicular to the collimator face. A +/- 1 cm error in true kidney depth may cause a 16% difference in GFR in an adult. The choice of the background region of interest (ROI), for background subtraction significantly affects the calculation. To minimize errors in the Gates' estimate of GFR we recommend 1) that syringe counting be done with the syringe parallel to the collimator face; 2) that the i.v. set be included in the postsyringe measurement; in cases of extravasation, the injection site should also be counted; 3) that kidney depth, especially for ectopic and transplanted kidneys be estimated by ultrasound or using lateral views; and 4) that a background ROI for each kidney be used.

Glomerular Filtration Rate↗
PubMed1990

The predictive value of Tc-99m DTPA renography in obstructive uropathy using animal model.

There is no simple analytical test. Radionuclide diuretic renography (RDR), being a dynamic imaging study reflecting the function of the kidney and the urodynamics of the urinary tracts, has the potential to predict the outcome of surgery in obstructive uropathy. In 12 sheep, we occluded one ureter for a maximum of seven weeks and followed up for a maxim of five weeks after release of occlusion. Repeated Tc-99m DTPA diuretic renography studies were performed and the results were correlated with the duration of complete ureteric occlusion. The renal uptake percentage and the extraction slope of the time activity curve (TAC) showed progressive and steady decrease over the period of the occlusion. By the fifth week there was very low uptake (less than 18%) and the TAC was almost flat, suggestive of severe nephropathy. The parenchymal transit time index (PTTI) showed immediate rise after occlusion but with no progressive increase in its value. By the fifth week it dropped down to normal. After release, the recovery of function showed good correlation with the renal uptake percentage and extraction slope of TAC before release of occlusion. Therefore both these parameters, rather than PTTI, can be used to predict the outcome of surgery before the release of complete obstruction of the ureter.

Animals↗
PubMed1989

Ventricular systolic and diastolic rate indices in patients with either normal or low resting left ventricular ejection fraction.

To investigate the potential uses of right and left ventricular systolic and diastolic rate indices in identifying patients with ischaemic heart disease (IHD), gated blood-pool imaging was performed for 19 normal subjects (group 1) and 56 patients, of whom 31 had resting LVEF greater than or equal to 50% (group 2) and 25 had resting LVEF less than or equal to 50 (group 3). The peak ejection rate (PER) and peak filling rate (PFR), their timing and the mean filling rate (MFR) were derived from the time-activity curves analysis. Group 2 patients had significantly reduced LV PER and PFR (3.00 +/- 0.58 EDV/s, p less than 0.005, 2.29 +/- 0.54 EDV/s, p less than 0.0009) as compared to normal (3.90 +/- 0.70 EDV/s and 3.35 +/- 0.80 EDV/s respectively). Patients with profoundly depressed LVEF had significantly low PER and PFR (1.96 +/- 0.50 EDV/s, 1.46 +/- 0.27 EDV/s respectively). However, there was considerable overlap in values between groups. Therefore, we conclude that there is no single parameter more sensitive than LVEF in identifying IHD patients with normal LVEF at rest.

Adult↗
PubMed1989

Radionuclide methodology for the assessment of the microcirculation in island pedicle flaps in a sheep model.

Island pedicle flaps with a proximal well-perfused part and a distal poorly-perfused part were raised in eight anaesthetized sheep. Autologous red blood cells were labelled in vitro with 99TcmO4 and plasma with 111In chloride. The labelled cells and plasma were injected intraarterially and both dynamic and static images of the time-course of radioactivity were obtained with a gamma camera. Time activity curves were generated for selected regions of interest of the flap. For both plasma and red cells there was a substantial decline in the amount of tracer reaching the distal part of the flap; the time to maximum counts increased and the time activity curves indicated a minor uptake and almost no clearance pattern. In general there were marked local differences in the flow of plasma and red cells. The flow of plasma was more rapid than that of the red cells in five of the eight sheep. The model provides a standardized pedicle flap having a proximal part with adequate circulation and a distal part with inadequate circulation. It is concluded that this sheep model is suitable for radionuclide studies examining those factors that influence the distribution of blood flow within this tissue.

Animals↗
PubMed1988

The use of 99mTc-DTPA for detection and localization of site of acute gastrointestinal bleeding.

Intravenously injected 99mTc-DTPA was evaluated in 64 patients for its efficiency in detecting and localizing sites of acute upper and lower gastrointestinal (G.I.) bleeding. These studies were correlated with endoscopic and surgical findings. There were 34 bleeders and 30 non bleeders giving a sensitivity of 90%, specificity of 82% and accuracy of 86%. Of these, 49 were upper G.I. studies (stomach 21 and duodenum 28) and 15 were lower G.I. studies (small intestine 8, large bowel 7). Of the 49 upper G.I. studies, 27 showed active bleeding while 22 showed no bleeding at the time of the study resulting in a sensitivity of 87.5%, specificity of 76% and accuracy of 82%. Of the 15 lower G.I. studies, 7 were bleeders while 8 were non bleeders. All the lower G.I. bleeding sites were accurately localized with the 99mTc-DTPA. An incidental finding of these studies was the localization of 99mTc-DTPA in the site of inflammatory and malignant lesions of the G.I. tract. Of the 64 studies, 18 inflammatory and malignant lesions were detected with the IV injected 99mTc-DTPA; 10 were bleeders while 8 were non bleeders. Image subtraction of early from delayed images was helpful to differentiate bleeding from non bleeding cases in this last group of studies.

Acute Disease↗
PubMed1988

Transfer of medical technology from a developed to a developing country.

Medical care is increasingly dependent on technology, but what are the problems involved in the transfer of technology from a developed to a developing country? What are the administrative, personnel and engineering problems? We address these questions in the context of our experience of transferring the medical technology and knowledge necessary for the development of nuclear medicine facilities in Kuwait.

Biomedical Engineering↗
PubMed1988

Response of left and right ventricle rate indices to exercise in normal volunteers.

Changes in left ventricular (LV) performance between rest (Re) and exercise (Ex) in normal hearts has been analysed in great detail using various parameters (P) of radionuclide MUGA studies. Little attention was given in this regard to right ventricular (RV) performance. We developed a program on the Informatik Sims V Computer applying the first derivative technique to analyse the time activity curve of both R and LV to study the changes in the following (P) between Re and Ex. 1. Ejection fraction (EF) 2. Peak ejection rate (PER) 3. Time to peak ejection rate (TPER) 4. Normalized TPER to the ejection period (EP) 5. Peak filling rate (PFR) 6. Time to peak filling rate (TPFR) 7. Normalized TPFR to the filling period (FP) 8. The time from peak filling rate to peak ejection rate (TPFR-TPER). Nineteen volunteers performed gated blood pool studies at Re and Ex in the semi-supine bicycle position. The results show that there were significant differences (P less than 0.0001) between all the parameters of the right and left ventricles at rest in comparison with those during exercise except for the normalized TPER in both right and left ventricles. In this study not only do we confirm the changes in LV performance between Re and Ex in healthy volunteers that has been previously reported, but we also report for the first time the changes in RV (P) in the same group of volunteers.

Adult↗
PubMed1988

Chronic urinary schistosomiasis: patterns of abnormalities in radionuclide Tc-99 m DTPA diuretic renogram.

The aim of this study was to describe the abnormal morphological and functional patterns observed in radionuclide diuretic renograms (RDR) in patients with chronic urinary schistosomiasis. A retrospective analysis of RDR for 92 patients was made. It revealed the following abnormalities: A) Morphological changes observed in the images: Pelvicalyceal retention of tracer (and dilatation) was seen in 68% of kidneys. Calyceal retention alone was seen in 5% and pelvic retention alone in 9%. An atrophic kidney was noted in 5%, nephropathic pattern in 3% and normal kidneys in 10%. Ureteric retention of tracer was seen in 64% of ureters. This was frequently associated with pelvicalyceal retention (61%) and this abnormality was bilateral in 44% of the urinary systems. B) Functional changes observed in the time activity curves: Non-obstructive delayed excretion was noted in 71% of kidneys. An obstructed kidney pattern nonresponsive to lasix was seen in 12%, plateau curve due to nephropathic kidney in 3% and atrophic kidney pattern in 4% of kidneys.

Adult↗
PubMed1987

Changes in cerebral perfusion after acute head injury: comparison of CT with Tc-99m HM-PAO SPECT.

Technetium-99m hexamethylpropyleneamine oxime (Tc-99m HM-PAO) was successfully used with single photon emission computed tomography (SPECT) on fourteen comatose patients who had acute head injuries. The SPECT scans were correlated with computed tomography (CT) scans obtained within 24 hours of the injury. Tc-99m HM-PAO SPECT was shown to have the following advantages: It reflected perfusion changes, was more sensitive than CT in demonstrating more lesions, and demonstrated lesions at an earlier stage than those demonstrated with CT. Different types of lesions, as evidenced by cerebral perfusion changes, have been described and categorized. The lesions that had a favorable prognosis could be separated from those with an unfavorable prognosis on the basis of the findings of Tc-99m HM-PAO SPECT.

Accidental Falls↗
PubMed1987

Effects of radioactive decay and their implications on in vivo metabolic imaging.

In the context of medical radionuclide imaging, possible consequences of molecular disruption that is due to radioactive decay and of the positron range are discussed. Radioactive decay may cause extensive disruption to the labeled molecule particularly if the transformation involves the creation of an inner shell vacancy. The movement of a positron away from the site of emission implies that the positron will annihilate in a region not disrupted by the decay. Neglect of the photon angular correlation disregards information on the physical and chemical state of the sample.

Humans↗
PubMed1986

Evaluation of technetium-99m DTPA for localization of site of acute upper gastrointestinal bleeding.

Intravenous Tc-99m DTPA was evaluated in 34 patients with active upper gastrointestinal bleeding. Active bleeding was detected in 25 patients: nine in the stomach, 12 in the duodenum, and four from esophageal varices. No active bleeding was seen in nine patients (two gastric ulcers and seven duodenal ulcers). Results were correlated with endoscopic and/or surgical findings. All completely correlated except: 1) one case of esophageal varices in which there was disagreement on the site, 2) three cases of duodenal ulcers that were not bleeding on endoscopy but showed mild oozing on delayed images and 3) one case of gastric ulcer, in which no bleeding was detected in the Tc-99m DTPA study, but was found to be bleeding at surgery 24 hours later. The Tc-99m DTPA study is a reliable method for localization of upper gastrointestinal bleeding with an agreement ratio of 85%. This method also can be used safely for follow-up of patients with intermittent bleeding. It is less invasive than endoscopy, is easily repeatable, and has the same accuracy.

Acute Disease↗
PubMed1986

99mTc-DTPA uptake in malignant and inflammatory bowel disease: experience from gastrointestinal bleeding studies.

During the evaluation of 99Tcm-DTPA for localization of acute gastrointestinal bleeding in 81 studies (78 patients), it was observed that there was an increased 99Tcm-DTPA at sites of inflammatory and malignant lesions of the GI tract in 18 studies. Active bleeding was detected only in 10 and no bleeding was detected in the remaining eight studies. In all the increased DTPA uptake helped to localize the site of bleeding. Image subtraction of early from delayed images according to a predefined acquisition and processing protocol helped to differentiate bleeding from non bleeding lesions. We conclude that increased 99Tcm-DTPA uptake in malignant and inflammatory lesions of the bowel is an additional advantage for its use in localizing the site of acute GI bleeding. Technetium-99m diethylenetriamine pentaacetic acid (99Tcm-DTPA) has been widely used for imaging the brain and kidneys since it was introduced by Hauser in 1970. Kadir and Strauss in 1979 reported that 99Tcm-DTPA localizes in segments of bowel with inflammation due to ulcerative colitis, regional enteritis and other forms of enterocolitis. Recently we reported the advantages of 99Tcm-DTPA in localizing the site of acute gastrointestinal bleeding. Inflammatory bowel diseases are among the causes of gastrointestinal bleeding. One of the problems in localizing the site of the bleeding by radionuclide procedures is the intermittent nature of the bleeding. We have reviewed all gastrointestinal bleeding studies in our department using 99Tcm-DTPA from January 1984 till September 1985 in order to find out whether increased uptake of 99Tcm-DTPA was helpful in localizing the bleeding lesion due to malignancy and/or inflammation.

Adult↗
PubMed1985

Effective dose equivalent and associated risks from mass chest radiography in Kuwait.

The number of x-ray examinations performed on persons undergoing mass chest radiography in Kuwait reached a maximum of 1.858 X 10(5) in 1982 with miniature radiography (70 mm) claiming more than 90% of the total number and the rest done with the large film technique. The annual prevalence of asymptomatic tuberculosis patients diagnosed by x rays, as reported by the project statistics, does not, in our opinion, justify exposing such a large population. In this paper, the effective dose equivalent is calculated from both miniature and large film mass chest radiography as applied in Kuwait. The values obtained are 283 mu Sv and 35.5 mu Sv, respectively. These figures yield calculated risks of fatal malignancies per examination of 3.37 X 10(-6) and 0.422 X 10(-6), respectively. The annual collective effective dose equivalent to the population undergoing mass chest radiography in Kuwait during the 7 y 1977-1983 is found to vary between 38-48 man-Sv. These figures are used to calculate an average of 0.5 additional cases of fatal malignancies per year, or about 12 excess fatalities in the forthcoming 25-y period if the number of mass chest x-ray examinations stays at its existing level. A total of 98% of these calculated excess fatalities result from the predominant technique, miniature radiography.

Adolescent↗
PubMed1985

Image subtraction in acute gastrointestinal bleeding studies using 99Tcm-DTPA.

99Tcm-DTPA has been evaluated in our clinical and experimental programme for the detection of acute gastrointestinal bleeding. As an adjunct to this programme, a protocol for image subtraction has been developed. The patient remains still while sequential static images I(i) (i = 1, . . ., N) are taken. They are first normalized to equal total counts and then subtracted images are produced according to the following three methods (a) I(i + 1)-I(i) (b) I(i) - I(mask) (c) I(mask) - I(i) where i not equal to mask and I(mask) denotes a user-selected mask image. Method (a) demonstrates fresh bleeding and sequential movement of blood in the bowel. Methods (b) and (c) demonstrate overall migration of blood and accumulated bleeding depending on the choice of the mask image.

Acute Disease↗
PubMed1984

Emission tomography: a concise theoretical overview.

A concise theoretical overview of emission tomography is presented aiming at physical interpretation of the equations so that fundamental concepts, similarities and differences between SPECT and PET, become transparent. The framework is that of an indirect sensing problem and image reconstruction from projections. The projections are expressed in terms of: the activity distribution, the attenuation distribution, the interactions of the radiation with matter, and the measurement geometry. In discussing the attenuation problem, recourse is made to the projections obtained by a gamma-ray (or a hypothetical monoenergetic X-ray) transmission CT scanner. This expression would be the one to which the corresponding expressions for SPECT and PET would reduce to if the attenuation distributions were known. Although the attenuation problem is less severe in PET, its extent is demonstrated with results from computer simulations. Finally, under conditions of 'adequate sampling', equations are given relating administered activity to spatial resolution, time for data collection, noise/signal ratio and system sensitivity.

Humans↗