Renogram and deconvolution parameters in diagnosis of renal artery stenosis. Variants of background subtraction and analysis techniques.

AIM: Multivariate statistical methods can be used for objective analysis. The emphasis is on analysing renal function parameters together, not one at a time. The aim is to identify curve parameters useful in making predictions in kidneys with and without renal artery stenosis (RAS). PATIENTS, METHODS: 68 patients with resistant hypertension were subjected to captopril renography with (99m)Tc-DTPA. Variants of background areas and background subtraction methods were employed. A correction was applied for loss of renal parenchyma. Parameters from time-activity curves and retention curves from deconvolution were calculated. Renal angiography established the presence or absence of RAS. Logistic regression analysis, using age- and kidney size-adjusted models, was performed to assess the capability of renography and deconvolution to differentiate between kidneys with and without RAS. RESULTS: Discrimination between normal kidneys and RAS was achieved by deconvolution and by renography. Deconvolution was the method of first rank with a sensitivity of 87% and a specificity of 98%. For separation of RAS and kidneys with parenchymal insufficiency deconvolution was the method of first rank with a sensitivity of 80 % and specificity of 89 %, whereas renography produced poor results. CONCLUSION: The best performance with (99m)Tc-DTPA was based on normalised background subtraction using a rectangular area between the kidneys. Deconvolution produced the most favourable results in the separation of kidneys with and without RAS. For separation of RAS and kidneys with parenchymal insufficiency conventional renography produced poor results. Conceptually, the results of a logistic regression analysis of renal function parameters may raise possibilities in the field of computer-aided diagnosis.

Estimating the diagnostic yields resulting from renography and deconvolution parameters: a logistic regression analysis.

METHODS: Seventy patients with established diagnoses of normal, parenchymally insufficient or acutely obstructed kidneys were subjected to gamma camera renography. Deconvolution was then performed using three main techniques subdivided into six variants. Parameters from time-activity curves as well as retention curves were calculated. Logistic regression analysis was performed to assess the ability of renography and deconvolution methods to differentiate between kidney groups. RESULTS: Discrimination between the groups was achieved by standard renography using six of 17 tested renogram parameters. Based on a set of six curve parameters, the correct classification rates ranged 86%-100%. Five of the six variants of the deconvolution technique used produced similar results. None, however, produced results which were as robust as those from renography. The sixth deconvolution method was consistently worse than the others. CONCLUSION: Standard renography was consistently better than any of the deconvolution techniques used in the separation of the kidney groups. Conceptually, the results of a logistic regression analysis of renogram parameters may raise possibilities in the field of computer-aided diagnosis.

Constrained least-squares restoration and renogram deconvolution: a comparison with other techniques.

It has previously been shown that an iterative constrained least-squares (CLSR) technique using a noise-based constraint may be superior to other methods of renogram deconvolution analysis. To test this hypothesis on real data, renography was performed on 70 patients with established diagnoses of normal, insufficient or acutely obstructed kidneys. Standard renography parameters were obtained from the time activity curves which were then deconvolved using three techniques. One kidney per patient was chosen at random for analysis resulting in a total of 43 normal and 27 diseased kidneys. The ability of each of the analytical techniques to discriminate between normal and diseased kidneys was assessed using logistic regression. CLSR proved to be robust and provide the best discrimination of the deconvolution techniques. However, the best overall discrimination was provided by a model based on the renography parameters excretion ratio, rate of uptake and time to peak activity which correctly classified 86% of the kidneys. It is possible that the renogram parameters could be used to produce notional probabilities of renal dysfunction which the physician could use as an aid in the interpretation of gamma-camera renography.

Cholescintigraphy and biochemical tests in cholecystitis--an evaluation with discriminant analysis.

The biochemical values of 76 patients with suspected cholecystitis were subjected to discriminant analysis. The final diagnoses, i.e. acute cholecystitis, chronic cholecystitis and non-biliary disease, were used as the grouping variable. Cholescintigraphy identified patients with acute cholecystitis. Routine preoperative biochemical tests were found to be of limited value. Only alkaline phosphatase was of help in predicting common-duct stones, especially in patients with acute cholecystitis. The conclusion is that many biochemical tests presently in common use could as well be dispensed with.

Renal function not impaired by hip arthroplasty. A prospective study of 26 patients.

To evaluate the importance of various changes during major surgery, 26 patients, electively chosen for total hip replacement (THR), were investigated for renal function preoperatively and postoperatively. In most of the patients, surgery was performed ad modum Charnley (n 25), and anesthesia was given mainly by continuous administration of bupivacaine or mepivacaine through an epidural catheter. Postoperatively, there was an improvement in glomerular filtration rate (GFR) and a reduction in renal concentrating ability (RCA), but no change in diurnal albumin excretion. No correlation was found between the change in GFR and, e.g., the degree of peroperative hypotension, bleeding, transfusions, or volume of infusions. There was a correlation between the impairment of RCA and the lowering of serum albumin concentration. In 3 patients the GFR was slightly impaired. The risk of contracting severe, acute renal failure seems low in THR performed on patients with reduced or normal kidney function.

Constrained least-squares restoration and renogram deconvolution: a comparison by simulation.

Before deconvolution can be used in renography, it is necessary to decide whether the renal function is sufficiently good to allow it. To see if this decision can be circumvented, an iterative constrained least-squares restoration (CLSR) method was implemented in which the point of termination of the iteration occurs when a residual vector has a value less than an estimate of the noise in the original renogram curve. The technique was compared with the matrix algorithm and with direct FFT division. The comparison was achieved by deconvolving simulated renogram data with differing transit time spectra and statistics. As expected, the FFT technique produced results of little value whereas the CLSR and matrix methods produced values of mean transit time (MTT) that differed slightly from the expected results. Analysis indicated that the matrix approach was superior when the percentage noise component was less than 6% and vice versa. No technique produced useful transit time spectra. As the CLSR technique produced better results than the matrix method in simulations with relatively long MTTs and high noise, it seems reasonable to suggest that it might be used for renogram deconvolution without the need for previous inspection of the curves.

Long-term effect of dopaminergic drugs in restless legs. A 2-year follow-up.

Thirty patients with restless legs syndrome, who initially had all responded well to treatment with levodopa and benserazide, were studied as to the long-term effect of the drugs (at least 2 years). During the 2-year period, two patients were switched from levodopa to bromocriptine. Two patients no longer needed levodopa; one of them had developed paraplegia and in the other the symptoms of restless legs syndrome had disappeared completely. The remaining 26 patients continued to use levodopa. Eight patients maintained the original dose, nine had to use an increased dose, and nine found a decreased dose to be sufficient. The only side effect was transient nausea reported by two of the 30 patients. The study showed that the relief of symptoms of restless legs syndrome by dopaminergic drugs does not wear off with the passage of time, that side effects are minimal even with long-term use, and that the dose needed to obtain relief may increase as well as decrease.

Cholescintigraphy versus infusion cholecystography in acute cholecystitis.

Patients with the clinical diagnosis of acute cholecystitis were studied with intravenous cholecystography and cholescintigraphy. The two examinations alternated in a random order. The final diagnosis was ascertained by surgery in most patients. Either cholecystography or cholescintigraphy could be used in the diagnostics of patients with suspected acute cholecystitis. The methods have about the same accuracy. However, cholescintigraphy is performed more easily and more rapidly than intravenous cholecystography.

A study of so-called hypochondriasis.

Twenty-four patients with unexplained somatic complaints were subjected to a thorough somatic examination. Only when the examination proved negative was the patient entered into the study. The patients were clinically appraised according to criteria given in DSM-III. Generalized anxiety disorder (GAD) was diagnosed in 12, somatization disorder (SD) in 8, and hypochondriasis in 4 patients. Seventeen of the 24 patients agreed to participate in biochemical investigations including a TRH load, a dexamethasone test, and a determination of the monoamine metabolites 5-HIAA and HVA in cerebrospinal fluid (CSF). A normal TSH increase and a normal suppression of cortisol were registered. The HVA values correlated significantly with the 5-HIAA values as well as with the alexithymia scores. Concerning alexithymia and maturity level, no difference as to social class was found. The patients filled in a Zung depression chart. The Zung scale and the 5-HIAA values were both inconsistent with depressive illness. In so-called hypochondriasis a long-term relationship, including selected somatic and biochemical examinations and thorough information, was crucial in abating the patient's distrust and thus the need for health care.

Deconvolution analysis of renograms obtained with simultaneously administered 99mTc-DTPA and 131I-hippuran.

Seventy patients were studied with a dual radionuclide technique. The conventional renograms and the blood curve were subjected to deconvolution analysis using the matrix algorithm method, and the following curve data calculated from the retention functions: absolute and relative amplitudes, minimum time of the retention function, maximum time of the retention function and mean transit time. The findings with the two radiopharmaceuticals 99mTc-DTPA and 131I-Hippuran were compared under normal and pathological conditions. The correlations between the data with 99mTc-DTPA and those with 131I-Hippuran were highly significant (p less than 0.01). So was the correlation between the absolute amplitude of the retention curve and the rate of uptake based on the corresponding renogram (p less than 0.01). Due to the difference in the renal handling of the two tracers, longer maximum times were obtained with 99mTc-DTPA. The mean transit times were also longer with 99mTc-DTPA, except in kidneys with parenchymal insufficiency. The highest amplitudes were found in normal kidneys, while the lowest values were observed in parenchymal insufficiency. In the group with acute ureteral obstruction, the mean transit times tended to be increased. The maximum times were even more increased. With both tracers it is possible to distinguish between the three groups of renal conditions studied here: Normal, parenchymal insufficiency, and acute ureteral obstruction.

A FORTRAN program for deconvolution analysis using the matrix algorithm method with special reference to renography.

A FORTRAN IV program is presented for deconvolution analysis using the matrix algorithm method. With the deconvolution technique retention functions are calculated from time-activity curve data representing both kidneys and blood background. The program computes for each kidney the minimum and maximum time of the retention function. It also calculates the initial amplitudes, absolute as well as relative, and the mean transit time of the retention functions. The design of the program allows for optional reviews of intermediate outputs at important stages. It also allows for the plotting of conventional time-activity curves of both kidneys corrected for blood background. Finally, the program plots the retention functions and some of their characteristics.

A FORTRAN program for ranking and for calculation of Spearman's correlation coefficient.

A FORTRAN IV program is presented for ranking data in ascending order. The ranks corrected for ties are printed together with the corresponding raw data, if requested. After ranking, the Spearman's rank correlation coefficient, rs, as well as the corresponding t-value, can be calculated. In these calculations corrections are made for tied values.

In vitro interaction between venous blood clots and radiopharmaceuticals.

Clots of 1 ml venous blood formed in glass tubes after 10 min at room temperature were incubated at 37 degrees C with the radiopharmaceutical to be studied. Methods for quality control of the radiopharmaceuticals were compared. Gel chromatography scanning was found to give reliable information. The incorporation into the clot was studied at different pH values and after various time intervals. The highest incorporation was found for 125I-fibrinogen and for 99mTc-macroaggregates of albumin, followed by 99mTc-sulphur colloid and 99mTc-streptokinase at pH less than 2. The titrated initial dose of 99mTc-streptokinase was studied at various pH levels. The lysing effect was less in the pH range 1-2.5, where the best labeling yield was obtained. The inactivation of streptokinase by the labeling procedure was also studied with immunoelectrophoresis and decomposition of casein. In vitro studies of the interaction of radiopharmaceuticals with clots add information for the clinical use of radiopharmaceuticals for thrombus localization.

Bile flow before and after cholecystectomy: a study with 99mTc-HIDA.

Computer-assisted 99mTc-HIDA cholescintigraphy was performed before and after elective cholecystectomy in 24 patients. Preoperative cholecystography had shown gallstones in a well visualized gallbladder in 12 of the patients, and in 12 the gallbladder had not been visualized. Liver function tests gave normal results in all 24 patients, and peroperative cholangiography showed no common duct stones in any patient. In the series with functioning gallbladder, comparison of the preoperative and postoperative scintigrams showed that cholecystectomy was followed by significantly earlier visualization of the lower part of the common duct and of the duodenum. The number of times that passage of activity to the duodenum was observed also rose significantly. Comparison of the time-activity curves showed that after cholecystectomy the liver activity reached its maximum value significantly earlier post-injection as compared with the preoperative values. All of these changes were absent in the series with nonfunctioning gallbladder. Removal of a functioning gallbladder results in accelerated, though still irregular flow of activity to the duodenum.

Filling of the gallbladder as studied by computer-assisted Tc-99m HIDA scintigraphy: concise communication.

Gallbladder filling was studied using computer-assisted cholescintigraphy in normal subjects who had fasted overnight. The gallbladder tended to visualize earlier than the distal part of the common bile duct. It appeared at approximately the same time regardless of whether or not there was passage of activity into the duodenum. This suggests that filling is not dependent on contraction of the sphincter of Oddi. Sequential images demonstrated that the activity entering the gallbladder rapidly reached the fundus. Time-activity curves showed a gradual buildup of activity in the bile ducts followed by sudden entrance into the gallbladder. Time-activity curves of the gallbladder's proximal and distal parts showed signs of an exchange of activity, suggesting that the gallbladder's motor function is not quiescent during fasting. Gallbladder motility could explain the periodic irregularities on the time-activity curve. These irregularities were smaller but not less frequent after morphine administration.

Function of liver, gallbladder and sphincter of Oddi after major surgery studied by computer-assisted cholescintigraphy and real-time ultrasonography.

Patients with normal gallbladders were subjected to computer-assisted Tc-HIDA cholescintigraphy at fixed intervals after major surgery. Hepatic time--activity curves showed that hepatic excretion of the material was first reduced and later a reduction of hepatic uptake followed. The gallbladder responded first by dilatation and reduction of motility and later by delay in or even absence of visualization. Postoperative dilatation was confirmed with real-time ultrasonography. No tracer passed into the duodenum in the early postoperative stage indicating spasm of the sphincter of Oddi. Healthy volunteers were studied with and without morphine and with and without a 24 h fast. The sphincter of Oddi closed after morphine but not after fasting. Transient non-visualization of the gallbladder after surgery makes the diagnosis of postoperative cholecystitis more difficult.

Jaundice in acute cholecystitis without common duct stones.

Patients with acute cholecystitis without common duct stones were studied pre- and postoperatively with 99mTc-HIDA scintigraphy. The resulting hepatic time-activity curves were analyzed. Preoperative serum bilirubin levels were closely correlated with hepatic discharge but not with hepatic uptake of the radiopharmaceutical. Cholecystectomy resulted in prompt improvement of hepatic discharge but did not affect uptake. In acute as well as in chronic cholecystitis cholangiograms taken before removal of the gallbladder were compared with those taken after. In acute cholecystitis the former view frequently showed medial displacement of the biliary tract and incomplete filling of its proximal part. Displacement of the duct was also apparent in comparisons of pre- and postoperative scintigrams. Jaundice in acute cholecystitis is due to reduced excretion which may be caused by pressure on the ducts by the distended gallbladder.

Evaluation of renal function parameters with simultaneously administered 99mTc-DTPA and 131I-hippuran.

The present study aimed at comparing two renal function tests using 99mTc-DTPA (diethylene triamine penta acetic acid) and 131I-labeled hippuran (o-hippuric acid). A mixture of 80 MBq 99mTc-DTPA and 7.4 MBq 131I-hippuran in a total volume of 1.5 ml or less was injected into an arm-vein. Both radiopharmaceuticals have identical initial distributions in the blood pool when injected in this manner. Seventy-two patients were studied with the present dual radionuclide technique. The following parameters were derived from the renogram: area under curve, uptake ratio, Tmax, decrease ratio, excretion ratio, and rate of decrease. The parameters for 99mTc-DTPA and 131I-hippuran were compared for various kidney groups. Generally the renographic parameters were well correlated. Apart from the systematic differences due to different modes of renal excretion, the curve patterns virtually agreed. The differences that were observed between the two tracers lacked clinical significance.

Determination of bone blood supply with Tc-99m red blood cells and In-113m transferrin in fractures of femoral neck: concise communication.

The uptake of in vivo labeled Tc-99m RBCs and In-113m transferrin was studied in femoral bone of 21 patients who had recent operations for fracture of the femoral neck. Femoral bone biopsies and blood samples were obtained during the operation. The activity values for bone biopsies, erythrocytes, and serum were determined, and the uptake ratios between bone and erythrocyte cpm/g and between bone and serum were calculated. Biopsy samples were taken from the femoral head in 21 cases and from the trochanteric region in 14. The activity ratios for the two tracers correlated well: r = 0.94 for femoral head biopsies (P less than 0.001) and r = 0.98 for samples from the trochanteric region (P less than 0.001). Thus, the procedures are interchangeable and either may be valuable in assessing bone blood supply. An additional patient, studied only with Tc-99m RBCs, had a subsequent operation for nonunion of a fracture. Samples of both cancellous and cortical bone were obtained from the removed head. The activity ratios for the two types of bone tissue differed significantly (P = 0.02).