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Biomedical subjects

G T Krishnamurthy

Publications and source records attributed to G T Krishnamurthy.

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

Design and operation of a nuclear medicine picture archiving and communication system.

Construction of a new Veterans Administration Medical Center provided a unique opportunity to design and implement a state-of-the-art nuclear medicine department in a large teaching and research hospital. The new medical center allowed the acquisition of all new gamma cameras and computer systems without any historical need to patch together a system of old and new equipment. The picture archiving and communication system (PACS) was designed to link five gamma cameras to four image viewing areas, followed by digital archive on an optical disc. The gamma cameras' computers and viewing areas' computers are linked to a central networking computer in a manner that provides nine independent but digitally communicating image computers. Each nuclear medicine computer is capable of acquiring gamma camera data while possibly also performing up to three other simultaneous tasks: analysis of image data, transfer of image data from node to node, and patient database manipulation. The nine image computers each appear to the user as a digital file cabinet, containing various folders, which in turn contain patient studies. To transfer a patient study from one location to another, the user simply queues a transfer request by selecting a file drawer-folder combination for the source and destination locations. It takes only a few seconds to queue a transfer request, and the transfer is complete about a minute later without any further user intervention. A computer genie awakens during the early morning off-hours and performs housekeeping tasks, including movement of patient studies (based on date of acquisition) from active viewing folders to inactive archive folders. All scheduling, workload data, patient image reports, etc, are handled by a patient textual information database system. Patient reports and scheduling information are transmitted to the medical center's central computer where they are made readily available throughout the medical center. The PACS, in clinical use since the spring of 1988, is practical and well-received by technologists, nuclear medicine physicians, and more importantly, our consumer, the referring physicians.

Hospital Information Systems↗
PubMed1990

Pharmacokinetics and clinical application of technetium 99m-labeled hepatobiliary agents.

Hepatobiliary imaging, introduced first in late 1950s with iodine 131 rose bengal, has undergone major changes since the introduction of technetium 99m-labeled agents in the late 1970s. 99mTc-labeled iminodiacetic acid (IDA) agents, with their high hepatic uptake and fast biliary excretion, provide superior image resolution in addition to supplying simultaneous physiologic parameters quantitatively. The measurement of hepatic extraction fraction by deconvolutional analysis aids in separating hepatocyte from biliary disease. Excretion half-time calculation by nonlinear least square fit provides a quantitative method of analyzing hepatobiliary function and correlates directly with the severity of disease. The measurement of gallbladder ejection fraction, ejection rate, and common bile duct bile reflux index following cholecystokinin, enables quantification of the degree of obstruction to bile flow through the common bile duct. The combined application of morphologic and physiologic parameters enables diagnosis of various hepatobiliary disease, especially in early stages. Quantitative functional parameters not only provide criteria for diagnosis, but also assist in monitoring the therapeutic benefit from drugs and interventional techniques such as endoscopic sphincterotomy or balloon dilation of the obstruction. Biliary dynamic studies with cholecystokinin assist in distinguishing common bile duct dilation without obstruction from dilation with obstruction. Methods of application of 99mTc-IDA agents in quantitative physiologic studies are reviewed and future direction of their use is proposed.

Biliary Tract↗
PubMed1989

Technetium-99m-iminodiacetic acid organic anions: review of biokinetics and clinical application in hepatology.

Technetium-99m-labeled iminodiacetic acid analogs are a new class of organic anions, taken up and secreted by hepatocyte into hepatic bile by a carrier-mediated organic anion pathway. They provide a new dimension in the assessment of pathophysiology and morphology of the hepatobiliary system. The amount of uptake and the rapidity of its elimination from the liver is dependent upon the structural configuration of the agent as well as the functional integrity of the hepatocyte and the patency of the biliary system. The clinical areas for application are wide and include most of the hepatobiliary diseases. Technetium-99m-iminodiacetic acid, an agent well suited for both planar and single photon tomographic scintigraphy, is ideal for early diagnosis prior to anatomical changes in the hepatobiliary system. The data collection directly from the liver provides quantitation of both regional and global liver diseases. The count-based method for measuring gallbladder emptying overcomes the theoretical disadvantages of geometric tests. Biokinetics and current clinical application of six of the 99mTc-iminodiacetic acid agents are reviewed, and the potential future clinical and research areas of application are indicated.

Anions↗
PubMed1989

Primary lung cancer: biodistribution and dosimetry of two In-111-labeled monoclonal antibodies.

This study was undertaken to measure the biokinetics and organ dosimetry of indium-111-labeled monoclonal antibodies (MoAbs) with a whole-body gamma camera imaging technique. Twenty patients with primary lung cancer were studied with two different MoAb agents (anti-carcinoembryonic antigen ZCEO25 and antiadenocarcinoma LA20207). Imaging was performed at 1, 24, 72, and 144 hours after injection. Scintigraphic whole-body retention was verified by means of comparison with the results from in vitro counting of excreta. Organ retention was verified in an abdominal phantom. The MoAb cleared slowly from the heart and lungs, the brain and spleen showed no clearance, and the liver showed increased activity over the 6-day period. Dosimetry for ZCE025 showed a dose to the liver of 1.3 rad/mCi (0.36 mGy/MBq); heart, 1.5 rad/mCi (0.40 mGy/MBq); spleen, 1.1 rad/mCi (0.29 mGy/MBq); total body, 0.49 rad/mCi (0.13 mGy/MBq); and testes, 0.39 rad/mCi (0.11 mGy/MBq). The dosimetry for LA20207 was similar.

Adenocarcinoma↗
PubMed1988

Left ventricular response to submaximal and maximal exercise in asymptomatic aortic regurgitation.

In patients with chronic aortic regurgitation the quantitative changes in loading conditions and left ventricular performance from rest to submaximal exercise have not been related to the magnitude of change observed from rest to maximal exercise. Changes in end-diastolic volume index, as a measure of preload, and measures of contractile performance (ejection fraction and the systolic blood pressure/end-systolic volume index ratio) were assessed at rest, submaximal and maximal supine bicycle exercise using radionuclide angiography in 74 patients with chronic moderate to severe aortic regurgitation. With exercise, end-diastolic volume index decreased in a stepwise manner from 166 +/- 47 to 152 +/- 41 to 143 +/- 41 ml/m2 at rest, submaximal and maximal exercise, respectively. For the entire group, these changes were not associated with a significant change in ejection fraction but were associated with stepwise increases in systolic blood pressure to end-systolic volume index ratio. However, when patients were divided into 3 subgroups based on an increase (group I), minimal change (group II) or a decrease (group III) in ejection fraction from rest to maximal exercise, stepwise increases in systolic blood pressure to end-systolic volume index were again observed in groups I and II but not in group III. These changes were significantly greater in group I than in group II at submaximal and maximal exercise levels. Differences in ejection fraction response and end-diastolic and end-systolic volumes with exercise in the 3 groups were evident at the submaximal exercise level.(ABSTRACT TRUNCATED AT 250 WORDS)

Aortic Valve Insufficiency↗
PubMed1988

Scintigraphic criteria for the diagnosis of obstructive hepatobiliary diseases with Tc-99m IDA.

The purpose of this study is to define the scintigraphic parameters that reliably predict the presence of obstructive hepatobiliary diseases. Gallbladder and intestinal visualization times noted during cholescintigraphy with Tc-99m IDA were compared to functional and morphologic parameters for their ability to accurately diagnose biliary diseases. One hundred and twenty-five normal subjects and 127 patients with five different types of hepatobiliary diseases were studied. Bile pooling in segmental ducts with minimal prolongation of excretion t-1/2 was the feature most commonly seen in partial common bile duct obstruction, and biliary nonvisualization with marked prolongation of excretion t-1/2 was the primary feature of total obstruction. Sclerosing cholangitis showed band constrictions and beading along bile ducts with regional variation in excretion t-1/2, and primary biliary cirrhosis demonstrated normal bile ducts with uniform prolongation of excretion t-1/2. Patients with cholelithiasis showed normal image patterns of the major ducts. Intestinal visualization by 60 minutes was only 46% sensitive and 77% specific with an overall accuracy of 74% in the detection of biliary obstruction. Delayed gallbladder visualization and reduction in ejection fraction were sensitive but nonspecific indicators of biliary disease. We conclude that Tc-99m-IDA imaging is an accurate test for the diagnosis of obstructive hepatobiliary disease provided both quantitative functional and qualitative morphologic parameters are analyzed. Intestinal nonvisualization at 60 minutes alone is not reliable as a sole parameter for the detection of partial biliary obstruction.

Adult↗
PubMed1988

Gallbladder filling and post-ceruletide emptying in prairie dogs and rabbits.

The filling and emptying characteristics of the gallbladder in prairie dogs and rabbits were studied to assess the importance of the residual bile in the pathogenesis of gallstones. In prairie dogs under ketamine/xylazine anesthesia, a significantly larger fraction (p = 0.001) of hepatic bile entered the gallbladder (87 +/- 8%) than the intestine during fasting and very little bile emptied (0-3% ejection fraction) following ceruletide infusion. In rabbits under similar anesthesia, only a small fraction of hepatic bile entered the gallbladder (4 +/- 2%) during fasting, and the gallbladder emptied almost completely (85% ejection fraction) following ceruletide infusion. The resultant higher residual bile in the prairie dog gallbladder and lower residual bile in the rabbit gallbladder may explain why gallstones form so readily in prairie dogs but not in rabbits when fed a lithogenic diet. These similarities and differences in gallbladder function must be taken into account when considering any animal as a model for gallstone formation.

Animals↗
PubMed1988

Primary biliary cirrhosis: Tc-99m IDA planar and SPECT scanning.

The authors studied ten patients with primary biliary cirrhosis using planar and single photon emission computed tomography (SPECT); results were compared with those from 13 healthy subjects. Patients with primary biliary cirrhosis had six- to tenfold prolongation of mean halflife (t 1/2) hepatic excretion of technetium-99m iminodiacetic acid (IDA) compared with mean t 1/2 excretion in healthy subjects. All patients with primary biliary cirrhosis had diffuse, uniform hepatic isotope retention and normal major bile ducts on planar and SPECT scans. The gallbladder was seen within 60 minutes in nine of nine patients who had intact gallbladders. The mean gallbladder volume was normal, but gallbladder ejection fractions and ejection rates were reduced in patients with primary biliary cirrhosis compared with those of healthy subjects. In contrast with previous studies of patients with sclerosing cholangitis and common bile duct obstruction, patients with primary biliary cirrhosis had different findings on scintiscans. In the early evaluation of patients with cholestasis, Tc-99m IDA hepatobiliary scintigraphy may be useful in the selection of the most appropriate invasive diagnostic test to enable a definitive diagnosis.

Adult↗
PubMed1988

Hepatocyte versus biliary disease: a distinction by deconvolutional analysis of technetium-99m IDA time-activity curves.

A combination of quantitative hepatobiliary imaging techniques was developed to study normal control subjects and patients with 3 categories of hepatobiliary disease: 1) alcoholic cirrhosis; 2) sclerosing cholangitis; and 3) isolated common bile duct obstruction. Scintigraphic images were supplemented by quantitative measurement of hepatic extraction fraction by deconvolutional analysis and liver excretion T 1/2 by a nonlinear least squares method. In diseases confined primarily to the biliary tract (isolated common bile duct obstruction and sclerosing cholangitis), the mean hepatic extraction fraction as measured by deconvolutional analysis was not different from that in normal controls. In severe alcoholic cirrhosis, considered primarily a hepatocyte disease, the hepatic extraction fraction was markedly reduced. The T 1/2 excretion, compared to normal subjects, was prolonged in all three liver disease categories. We conclude that these quantitative parameters were able to detect hepatobiliary disease and to separate severe hepatocyte disease from biliary tract disease.

Biliary Tract Diseases↗
PubMed1987

Diagnosis of sclerosing cholangitis with technetium 99m-labeled iminodiacetic acid planar and single photon emission computed tomographic scintigraphy.

The purpose of this study was to determine whether 99mTc-iminodiacetic acid planar biliary scintigraphy combined with single photon emission computed tomography could detect sclerosing cholangitis and provide additional information regarding the extent and severity of disease. Thirteen patients with sclerosing cholangitis and 13 normal control subjects were studied. Scintigraphic results were also compared with previously reported studies of patients with isolated common bile duct obstruction and with primary biliary cirrhosis. The planar scintigraphy in patients with sclerosing cholangitis showed beading or bandlike constrictions of the biliary tract corresponding to lesions seen on cholangiography, and the image pattern was distinctly different from images obtained from patients with isolated common bile duct obstruction or primary biliary cirrhosis. The single photon emission computed tomography images of the liver in patients with sclerosing cholangitis demonstrated multiple focal areas of 99mTc-iminodiacetic acid retention, representing bile stasis in intrahepatic bile ducts. Compared to controls, the mean hepatic clearance half-time of 99mTc-iminodiacetic acid was markedly delayed in patients with sclerosing cholangitis (6-10 times normal). Individual patients with sclerosing cholangitis had wider variation in isotope clearance half-time from three regions of the liver than patients with isolated common bile duct obstruction, consistent with regional difference in disease severity and variable impairment of bile flow. In 4 patients with sclerosing cholangitis with incomplete filling of the right and left hepatic ducts at cholangiography, planar and single photon emission computed tomographic scintigraphy provided evidence of significant intrahepatic sclerosing cholangitis. In conclusion, combined 99mTc-iminodiacetic acid planar and single photon emission computed tomographic scintigraphy is a sensitive noninvasive test for the diagnosis of sclerosing cholangitis and reliably differentiates sclerosing cholangitis from isolated common bile duct obstruction or primary biliary cirrhosis. Measurement of isotope clearance half-time provides quantitative physiologic data that may be useful in the longitudinal follow-up of patients with sclerosing cholangitis.

Adult↗
PubMed1987

Detection of bile leakage from traumatic right hepatic duct laceration with technetium-99m DISIDA cholescintigraphy.

A woman was admitted to the hospital after blunt abdominal trauma. Initial ultrasound was equivocal but suggested a localized hepatic laceration. The patient was discharged but returned three weeks later with ascites and mild pain in the right upper abdominal quadrant. Hepatobiliary imaging identified a large bile leak originating from the porta hepatis but showed no evidence of parenchymal injury. No hepatic injury was found at surgery, but a laceration of the right hepatic duct was identified. Hepatobiliary imaging is the procedure of choice in diagnosing bile leaks from the extrahepatic biliary system.

Adolescent↗
PubMed1986

Intrahepatic versus extrahepatic cholestasis. Discrimination with biliary scintigraphy combined with ultrasound.

Biliary scintigraphy and ultrasound imaging were performed in 52 patients with suspected biliary tract pathology. Results were correlated with the findings of direct cholangiography. Several new innovations in scintigraphic technique were used. The combination of ultrasound imaging and scintigraphy correctly identified biliary tract obstruction in 17 of 19 patients, 12 of whom had dilated bile ducts on ultrasonography. Intrahepatic cholestasis was correctly diagnosed in 11 of 13 patients. Accurate discrimination between intrahepatic and extrahepatic cholestasis was achieved in 28 of 32 patients (88%) with the combined studies. Scintigraphy also provided a correct diagnosis of acute cholecystitis in all 9 patients with surgically confirmed disease. Eleven additional patients with gallbladder or pancreatic disease had normal bile ducts at scintigraphy, which was confirmed with cholangiography. When combined with ultrasound imaging, modern biliary scintigraphy can (a) provide excellent discrimination between intrahepatic and extrahepatic cholestasis and (b) help determine the need for subsequent invasive diagnostic studies in selected patients.

Adult↗
PubMed1986

Measurement of gallbladder volume and dynamics by combined SPECT and planar scintigraphy.

A new method is described for measurement of gallbladder volume based on three-dimensional single photon emission computed tomography (SPECT). The technique was first validated in a body phantom that used a balloon to represent the gallbladder. The balloon was inflated with a known volume and SPECT volume was calculated by summing the voxels in each transaxial slice above a percentage count threshold. The SPECT and true volume showed a high linear correlation between 15 to 90 ml (r = 0.99). The mean fasting gallbladder volume using a technetium-99m-labelled hepatobiliary agent in nine normal subjects was 26 +/- 2 ml (range 18 to 39 ml). By combining the SPECT measurement with a planar technique, it was also possible to evaluate gallbladder emptying parameters. Following a 3 min infusion of 10 ng kg-1 of cholecystokinin octapeptide (CCK), the mean gallbladder ejection rate was 1.2 +/- 0.2 ml min-1 and the residual volume was 12 +/- 2 ml. SPECT offers a new noninvasive method for accurate measurement of gallbladder volume.

Adult↗
PubMed1986

Effects of common therapeutic concentrations of oxygen on lung clearance of 99mTc DTPA and bronchoalveolar lavage albumin concentration.

We studied the effects of oxygen concentrations (21 to 50%) considered clinically "safe" on clearance of inhaled technetium-labeled diethylene triamine pentaacetate (99mTc DTPA) and the concentration of albumin in bronchoalveolar lavage (BAL) fluid of normal subjects. We also measured several markers of cell injury and inflammation in the BAL fluid including total and differential cell counts, lactate dehydrogenase, alkaline phosphatase, extracellular potassium, and several eicosanoids. Subjects inhaled oxygen (50, 40, 30, or 21%) for a mean of 45 h; there were no symptoms or bronchoscopic signs of oxygen toxicity. The concentration of albumin in BAL fluid was increased compared with baseline measurements in a dose-dependent manner in subjects exposed to 30% oxygen and above. Clearance of 99mTc DTPA was increased only in subjects who inhaled 50% oxygen. There were no significant changes in BAL fluid volume or total and differential cell counts after oxygen exposure. A trend towards an increased percentage of polymorphonuclear leukocytes was noted in the 50% oxygen group. We found no evidence of cell injury or inflammation in the BAL fluid. Supplemental humidity did not appear to influence the findings in the 50% oxygen group. Thus, oxygen in concentrations considered clinically "safe" increases clearance of 99mTc DTPA and BAL albumin concentration in normal subjects after a relatively short time of exposure.

Adult↗
PubMed1985

Ceruletide intravenous dose-response study by a simplified scintigraphic technique.

The intravenous dose response of a ceruletide diethylamine (ceruletide) was established by a simplified scintigraphic technique where multiple graded doses were given sequentially on a single occasion. The gallbladder volume was represented nongeometrically by 99mTc-IDA counts. The mean latent period, ejection period, and ejection rate were similar for all four groups of subjects given 1-20 ng/kg of ceruletide. The mean (+/- SD) ejection fractions after 1, 5, 10, and 15 ng/kg of ceruletide as the single dose were 19.4 +/- 11.9%, 59.6 +/- 26.0%, 55.2 +/- 23.3%, and 67.8 +/- 8.7%, respectively. These ejection fractions were similar to the values when the identical dose of ceruletide was administered sequentially either before or after another dose. A dose of 5 ng/kg produced the most physiologic type of emptying. Intravenous doses of 10 ng/kg and larger caused adverse reactions in 42% of the total doses in the form of abdominal pain, nausea, systolic and diastolic hypotension, or bradycardia. It is concluded that the dose response of a cholecystokininlike agent (ceruletide) can be established reliably by a scintigraphic technique where multiple graded doses are given on a single occasion.

Adult↗
PubMed1985

Detection, localization, and quantitation of degree of common bile duct obstruction by scintigraphy.

The detection, localization, and quantitation of the degree of obstruction was successfully accomplished by [99mTc]IDA scintigraphy in 13 of 14 patients with cholangiographically documented common bile duct (CBD) obstruction. Ductal dilatation was present on ultrasound examination in only seven patients. The accuracy of biliary scintigraphy was enhanced by several innovations including: (a) selection of a radiopharmaceutical with rapid hepatic uptake and excretion; (b) shorter imaging interval over longer period of time; (c) substitution of image parameter for appearance time; and (d) quantitative measurement of bile emptying parameters following cholecystokinin infusion. Scintigraphically, the partial obstruction was characterized by CBD segmental narrowing or intraluminal filling defects and bile stasis within the area and segmental ducts. The gallbladder mean (+/- s.d.) ejection fraction of 20.0 +/- 17.5%, ejection period of 6.8 +/- 1.6 min, and ejection rate of 3.1 +/- 2.6% per min following 3-min infusion of 10 ng/kg of cholecystokinin octapeptide were reduced significantly when compared to control subjects. The level of CBD obstruction correlated well with the results of cholangiography. It is concluded that quantitative biliary dynamic scintigraphy employing modern techniques can accurately detect and localize CBD obstruction.

Adult↗