The value of parenchymal transit time index of Tc-99m DTPA diuretic renography in the evaluation of surgery in chronic bilharzial obstructive uropathy.

Selection of patients with chronic bilharzial uropathy (CBU) for surgery is a difficult problem due to the presence of grossly dilated urinary tracts without a significant obstruction in most of the cases. In this prospective study of 40 patients with CBU, the time-activity curve (TAC) patterns of the pre- and postoperative Tc-99m DTPA diuretic renography (RDR) studies were compared with the corresponding parenchymal transit time indices (PTTI). The aims were to find out which of these renographic parameters was more accurate in identifying obstruction and which was better in predicting the outcome of surgery. PTTI was more sensitive than TAC in identifying obstruction (96% and 92%, respectively) but it was less specific (78% and 98%). The detection accuracy of RDR for obstruction using TAC patterns was 96% compared to 84% using PTTI. Being independent of renal uptake function, PTTI could not predict the outcome of surgery as TAC could. In contrast to PTTI, TAC patterns could differentiate obstructed kidneys from severely nephropathic kidneys. However, PTTI was useful in identifying kidneys with residual nephropathy.

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.

Reproducibility and action levels for gamma camera uniformity.

Deciding on the action level for gamma camera non-uniformity is difficult because the reproducibilities of quality control measurements and service adjustments are usually unknown. This work evaluated the reproducibilities of integral uniformity (IU), differential uniformity (DU) and the corrected relative standard deviation (CRSD). The latter was calculated by removing from the relative standard deviation of the pixel counts the component due to statistical fluctuations. The reproducibility of each parameter was evaluated by analysing 10 intrinsic flood acquisitions with total counts of 2, 5, 10 and 30 million. All three parameters were less reproducible at the lower count densities, but as expected IU and DU also showed higher mean values. CRSD was consistent and highly reproducible, at all count densities. At 10 million counts CRSD had a coefficient of variation (COV) of 1.3% which was a five-fold improvement over the 6.6% and 6.1% found for IU and DU, respectively. The relative sensitivity of IU, DU and CRSD was compared in monthly measurements on 10 gamma cameras over one year. No significant difference in relative sensitivity was demonstrated: a change in camera performance produced about the same percentage change in each parameter. The precision with which service engineers adjust gamma cameras was also assessed by measuring the uniformity of 10 gamma cameras immediately after service adjustment at monthly intervals over one year. Finally, general action levels were defined for IU, DU and CRSD at 7%, 5% and 2.5% respectively.

Effect of cyclosporin A on bile flow in experimental animals using technetium-99m EHIDA.

The effect of cyclosporin A (CyA) on bile flow was studied in experimental rabbits by radionuclide imaging and measurement of bilirubin levels. The rabbits were dosed intravenously with 15 mg/kg CyA for 4 consecutive days. Each rabbit served as its own control. The rabbits were injected IV with technetium (Tc)-99m EHIDA, and dynamic images were obtained prior to and 1, 4, 8, and 15 days after CyA treatment. There was no difference in half-times of blood clearance in control and CyA-treated rabbits. There were differences in the half-times of liver curve and bilirubin measurements between control and 4-day treated rabbits. By the 15th day after CyA treatment both the radionuclide findings and bilirubin levels became normal. The results suggest that CyA causes intrahepatic cholestasis and demonstrate evidence of reversibility of CyA's toxic effect on bile flow after treatment is discontinued.

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.

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.

Experimental complete ureteric occlusion in sheep: radionuclide renography and histopathologic findings.

Complete ureteric occlusion produces various pathophysiological changes that can be monitored externally by technetium 99m diethylenetriamine penta-acetic acid (99mTc-DTPA) diuretic renography (RDR). Being a dynamic imaging study, it reflects the function of the kidneys and the urodynamics of the urinary tract. The aim of this study was to correlate the changes in parameters of RDR with the histological changes before and after the release of complete ureteric occlusion. In 9 sheep, RDR studies were performed serially after various periods of complete ureteric occlusion (up to 7 weeks) and after release of the occlusion (up to 5 weeks). The histological changes were correlated with changes in RDR. The progressive decrease in renal flow seen on renal images and flow time-activity curves (TACs) was explained by the development of endarteritis and thrombosis of small renal arteries. The progressive decrease in the renal uptake as indicated by the percentage renal uptake and the extraction slope of TAC is related to the progressive damage to the renal parenchyma, initially affecting the collecting ducts and tubules, with increasing interstitial fibrosis in the later stages. Obstruction for 3 weeks or less was associated with moderate damage to the parenchyma from which recovery was possible. Obstruction for 7 weeks was associated with marked damage without chance of recovery. The RDR is a non-invasive technique that can be used to monitor kidney damage after various periods of complete ureteric occlusion and to predict the outcome of surgery before the release of occlusion.

Evaluation of 99Tcm mercaptoacetyltriglycine for the detection and localization of gastrointestinal bleeding in an experimental animal model.

Technetium-99m mercaptoacetyltriglycine (99Tcm-MAG3) was evaluated for the detection and localization of the site of gastrointestinal bleeding in a sheep model. Radioactivity was detected in both the stomach and lower abdomen. However, 99Tcm-MAG3 is partially excreted by the liver and in the bile. The radioactivity in the bile moved to the small bowel. This movement of radioactivity in the lower abdomen can lead to a misinterpretation of the site of bleeding. Hence, 99Tcm-MAG3 may not be an effective radiopharmaceutical for the localization of the site of bleeding in the gastrointestinal tract, particularly the lower abdomen.

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.

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.

Development of an animal model using a closed system to study the sensitivity of a radiopharmaceutical for the detection of gastrointestinal bleeding.

An experimental animal model using a closed system to study the sensitivity of radiopharmaceuticals for the detection and localization of gastrointestinal (GI) bleeding site in a sheep was developed. This model was validated with 99mTc-DTPA. Radioactivity as low as 85.47 +/- 13.32 kBq in a volume of 2.1 +/- 0.14 ml at a bleeding rate of 0.07 ml/min was detected. Simulated intermittent bleeding experiments indicated that at 1 h after injection of 99mTc-DTPA there was still enough circulating radioactivity to bleed into the gut and that it was possible to perform repeat injection of 99mTc-DTPA as early as 2 h after the first injection.

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.

Dynamic lymph flow imaging in lymphedema. Normal and abnormal patterns.

Dynamic imaging of lymphatic flow was performed in 23 patients complaining of lymphedema of the lower extremities. All were injected intradermally with 1 mCi of Tc-99m human serum albumin (HSA) in the medial web on the dorsum of both feet. Image acquisition for the lower pelvis and both thighs was started within 5 minutes. An extra-large field-of-view gamma camera (General Electric 500A) with a low-energy, all-purpose collimator interfaced to a General Electric Star computer was used. Images were acquired in dynamic-byte mode, 128 X 128 matrix size, every one minute up to 40 minutes. Delayed images for the same region and for both legs were taken at 90 minutes. Time-activity curves from equal regions of interest over the inguinal regions on both sides were generated. Three patterns were recognized. Normal flow (12 patients) with symmetric or slightly increased or decreased flow on one side than the other and characterized by early appearance of medial bands, inguinal and pelvic lymph nodes in the early and the delayed images. Time-activity curves showed a stepladder rise in pulses every 3 to 4 minutes. Enhanced pattern (six patients), characterized by fast flow of lymph through the dilated lymphatics, and occasionally by subcutaneous pooling and increase in the number and size of inguinal and pelvic lymph nodes on the affected side.(ABSTRACT TRUNCATED AT 250 WORDS)

An experimental model for the detection and localisation of gastrointestinal bleeding using 99mTc-DTPA.

99mTc-DTPA was successfully used to detect simultaneously gastrointestinal bleeding sites in experimentally created mucosal ulcers in the colon and stomach of rabbits. Unlike the other radiopharmaceuticals that are currently used, 99mTc-DTPA was rapidly cleared from the vascular, hepatic and splenic circulation. The overall background radioactivity was low. 99mTc-DTPA appears to be an ideal agent for detection and localisation of gastrointestinal bleeding sites.

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.

Lymphscintigraphy in peripheral lymphedema using technetium-labelled human serum albumin: normal and abnormal patterns.

Lymphscintigraphy using Tc-99m human serum albumin (HSA) was examined in 23 patients with peripheral leg lymphedema. Each was injected intradermally with one mCi in the medial web space bilaterally. Images of the lower pelvis and both thighs were obtained within five minutes after injection using an extralarge field view camera GE 500A with low energy all purpose collimator interfaced with G.E. Star computer. These images were acquired in dynamic byte mode, 128 X 128 matrix size, every minute for 40 minutes. Delayed images for this region and of both legs were also taken at 90 minutes and time activity curves from comparable regions of interest over the inguinal area bilaterally were generated. Three patterns emerged: 1--normal lymph flow (12 patients) characterized by symmetrical or nearly symmetrical early appearance of lymphatics (medial bands) with visualization of inguinal and pelvic lymph nodes in both early and delayed images. Time activity curves showed step ladder rise, in "pulses" every three to four minutes. 2--enhanced lymph flow pattern (6 patients) was characterized by rapid movement of radiolabelled albumin through dilated lymphatics, occasionally with subcutaneous pooling, and both larger and more numerous inguinal and pelvic nodes on the lymphedematous side. 3--obstructed lymph flow (5 patients) was characterized by subcutaneous pooling, absent lymphatics, (medial bands) and flat, time activity curve on the lymphedematous side (only background activity) and absent inguinal and pelvic nodes. On delayed images, where lymphatic obstruction was incomplete there was delayed appearance of inguinal pelvic nodes which were fewer and smaller compared to the nonedematous side.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Marijuana and second-degree AV block.

A 21-year-old black man without history of heart disease had severe sinus bradycardia and intermittent second-degree AV block after the use of marijuana. After he had abstained from marijuana for 72 hours, the AV block disappeared. We have discussed possible effects of marijuana on the cardiovascular system.