UNLABELLED: This study was designed to evaluate the interobserver variability in reporting on 99mTc-dimercaptosuccinic acid (DMSA) scanning performed 6 mo after an acute episode of pyelonephritis for the detection of late renal sequelae. METHODS: Forty-six children were selected, who had early and late DMSA studies for evaluation of acute pyelonephritic lesions as well as sequelae. Three observers reported independently and separately on the early and late DMSA scans and, in a second step, on the late scan in the presence of the early scan. Interobserver reproducibility was evaluated for the early DMSA scan, the late DMSA scan alone, and the late DMSA scan with the early scan for comparison. RESULTS: Complete agreement between the three observers was reached in 75%, 78%, and 77% for the early DMSA scan, the late DMSA scan alone, and the late DMSA scan with the early scan for comparison, respectively. CONCLUSION: Interobserver reproducibility was high and was comparable for both early and late DMSA scintigraphy.

Acute Disease↗

PubMed2000

[On what is renal clearance based].

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Algorithms↗

PubMed2000

Atlas on acute pyelonephritis in children.

The authors describe various patterns of Tc-99m DMSA images that correspond to a diagnosis of acute pyelonephritis. Only those children with complete scintigraphic healing or considerable improvement after 6 months have been considered.

Acute Disease↗

PubMed2000

Simplified algorithms for the estimation of 99Tcm-MAG3 clearance.

The aim of this study was to evaluate two formulae allowing the determination of MAG3 clearance by means of a single blood sample, namely Bubeck's formula and Russell's formula. As a first step, a simulation study was performed with the two single-sample algorithms to predict MAG3 clearance as a function of plasma concentration, using various times for blood sampling and various body surface areas. As a second step, a validation study on 47 adult patients with varying renal function allowed a clinical comparison between the reference technique, namely the multiple blood sample technique, and the two simplified techniques. The simplified algorithms were calculated using the fitted value at 44 min. In the simulation study, whatever the time of blood sampling or the level of correction introduced for body surface area, the results obtained by means of Bubeck's algorithm diverged significantly from those of Russell's algorithm, for low clearance values as well as for high clearance values. The curve of the differences between the two methods had a typical boomerang shape. In the clinical study, the difference between Russell's algorithm and the reference method was generally within 20 ml.min-1, with no systematic bias; with Bubeck's algorithm there was a marked underestimation, both in the low and high clearance ranges. We suggest Russell's single-sample method is the method of choice.

Adult↗

PubMed2000

NORA: a simple and reliable parameter for estimating renal output with or without frusemide challenge.

The aim of this study was to evaluate a simple parameter describing renal output, namely NORA (normalized residual activity). We first compared, in a simulated model, different parameters of transit to an ideal standard; we then compared, in a clinical study, NORA and output efficiency. 123I-hippurate, 99Tcm-DTPA and 99Tcm-MAG3 plasma curves, each with two levels of renal clearance, were convoluted by means of different types of simulated retention functions, with different mean transit times. On the reconstructed renograms, several parameters reflecting renal transit were determined and compared with mean transit time. In a second step, in 33 patients, we compared output efficiency and NORA (i.e. the residual renal activity), normalized by the renal activity at 2 min. These two parameters were calculated at the end of the renogram, at the end of the frusemide test and after the micturition phase. In the simulated model, both output efficiency and NORA were only slightly influenced by the level of overall renal function. In the clinical study, a good correlation was found between output efficiency and NORA, whatever part of the study considered (renogram, frusemide test, post-voiding image). NORA is a simple and reliable parameter that allows quantification of renal output; it is almost independent of the level of renal function and can be used whatever the timing of the frusemide injection.

Adolescent↗

PubMed2000

Inter-observer reproducibility of relative 99Tcm-DMSA uptake.

99Tcm-DMSA planar images of 49 randomly selected patients (10 adults, 39 children) were sent to 15 physicians at various centres in Belgium. They were asked to calculate, using their own routine program, the relative uptake (expressed as a percentage) of each kidney. The data were sent on disks formatted so that they could be read by all participants, using their own computer systems. For each scan, the inter-observer variability was expressed using the maximum difference and the standard deviation of left renal uptake. Left renal uptake measured by the 15 observers in the 49 patients was 29.0-72.0% (mean +/- s = 49.8 +/- 6.4%). The maximum differences in left renal uptake ranged between 1.7% and 12.0% (4.5 +/- 2.6%); however, the maximum difference did not exceed 8% in about 90% of the patients. The standard deviations of the individual left renal uptake were between 0.6 and 3.9 (1.3 +/- 0.8). The standard deviations were significantly higher in adults (mean standard deviation = 2.05) than in children (mean standard deviation = 1.12) (P < 0.001); this was probably related to the high background observed in three adults with severe renal impairment. Indeed there was a significant correlation (P < 0.001) between the standard deviation and both the signal-to-noise ratio and the degree of asymmetry between the right and left kidneys. The differences between right and left kidney uptake were systematically lower for some observers, suggesting an influence of the calculation programs.

Belgium↗

PubMed2000

How good is the slope on the second exponential for estimating 51Cr-EDTA renal clearance? A Monte Carlo simulation.

It has been suggested that the slope of the second exponential of the plasma disappearance curve may be used to monitor changes in renal function instead of plasma clearance calculated using the slope-intercept method. The purpose of this study was to evaluate the magnitude of error in the slope induced by errors in sampling time and in activity measurement, and to compare it with the error observed in clearance. A model of mono-exponential curves based on two blood samples, taken at 120 and 240 min, was created. Normally distributed random errors were introduced into the sampling times and activity measurements. For each setting, the random errors were successively introduced 200 times and the coefficients of variation of the calculated slopes and clearances were determined. Variable errors in slope and clearance were induced by errors in sampling time and activity measurement. In general, the observed errors in the slope were high in the case of low slope values, decreasing progressively for increasing slope values. The errors in clearance followed a different pattern: highest errors were observed in the case of very low clearance, decreasing progressively for higher clearance values and attaining the minimal value at a lambda around 0.006 min-1, which corresponds to clearance of about 90 ml.min-1. The magnitude of the errors then started to increase again for higher clearance. For a large range of clearance values, the errors in the slope were higher than the errors in clearance. The only exceptions were cases with very high clearance rates. In conclusion, clearance calculation using the slope-intercept method should be preferred to that using the slope alone for monitoring changes in renal function.

Chelating Agents↗

PubMed2000

Influence of time interval and number of blood samples on the error in renal clearance determination using a mono-exponential model: a Monte Carlo simulation.

Mono-compartmental analysis based on 2- and 4-h blood samples (BS) of 51Cr-EDTA (EDTA, ethylenediaminetetraacetic acid) is commonly used for the calculation of the glomerular filtration rate (GFR). The purposes of this study were to estimate the magnitude of error in clearance induced by errors in the time of sampling and activity measurement; to estimate the impact of changing the interval between the BS; and to assess the influence of a higher number of BS in reducing the error. A model of mono-exponential curves based on a finite number of BS was created. Normally distributed random errors were introduced in the time of sampling and activity measurement. In a first step, three different time intervals were used; in a second step, seven different numbers of BS were used, all taken between 120 and 240 min. For each setting, the random errors were successively introduced 200 times and the coefficients of variation (CV) of the calculated clearances were determined. Variable errors in clearance were induced by errors in the time of sampling and activity measurement. In general, the observed errors were higher for high and low clearance, with lower errors for moderately reduced clearances. The errors in indicating the time of sampling played an important role for high clearance, whereas the errors in activity measurements led to important errors for low clearance. Prolonging the interval from 1 to 2 h resulted generally in an important decrease in error, except in the range 60-100 ml x min(-1). Prolonging the interval from 2 to 3 h resulted in only a small additional decrease in error, except for very low clearance. Errors in indicating the time of sampling and in activity measurements induce errors in clearance determination. These errors cannot be significantly reduced by simply increasing the number of BS or by prolonging the interval between the samples. It is probably better, in most cases, to keep using the 2-4-h method and to take extreme care when indicating the time of sampling and when measuring the activity, instead of increasing the number of samples or lengthening the procedure.

Algorithms↗

PubMed2000

Factors influencing the accuracy of renal output efficiency.

Output efficiency (OE) has been proposed as an objective tool for the estimation of renal emptying. The aim of this paper was to evaluate some factors that may affect the value of this parameter obtained by a 99Tcm MAG3 renogram. In 22 patients, the effect of different types of renal background correction was calculated. In 10 patients, simultaneous gamma camera renography and multiple blood sampling allowed the error of using a heart curve instead of a plasma curve to be evaluated. Finally, an evaluation was carried out on the effect of neglecting the change of plasma activity between the end of the furosemide acquisition and the post-micturition view obtained after repositioning of the patient on the gamma camera: 142 patients who had had multiple blood sampling were retrospectively selected for that purpose. It has been shown that all these factors may significantly affect the value of OE, particularly in cases with poor renal drainage. Unless standardization of the procedure is introduced for some of these factors, the cut-off levels for good, fair and poor drainage may vary between centres.

Algorithms↗

PubMed2000

Plasma clearance of 99Tc(m)-MAG3: accuracy of five single-sample methods.

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Algorithms↗

PubMed2000

A multicenter trial on interobserver reproducibility in reporting on 99mTc-DMSA planar scintigraphy: a Belgian survey.

UNLABELLED: Conflicting opinions have been expressed regarding reproducibility in 99mTc-dimercaptosuccinic acid (DMSA) planar renal image interpretation. The purpose of this investigation was to determine the level of interobserver variability among a large group of Belgian nuclear medicine physicians who evaluated a randomly selected series of DMSA planar scintigraphic examinations performed on children and adults. METHODS: All Belgian nuclear medicine centers (n = 82) were invited to participate in a reproducibility study on 99mTc-DMSA scintigraphy. 99mTc-DMSA scans obtained on 10 adults and 40 children were randomly selected from the databases of 2 hospitals. Those participating in this investigation (65 centers = 79%) received a series of computer disks containing 50 99mTc-DMSA studies. To avoid potential problems related to unfamiliar display, the disks were formatted to be interpretable using the participants' own computer systems. Each participant was then free to use his or her usual display (hard copies, contrast enhancement, color scale, gray scale, and so forth). For each kidney, the observers had to choose between the following answers: normal, abnormal, equivocal, and lack of quality. RESULTS: Forty-two responses were obtained from a wide variety of institutions and from observers with different levels of experience in interpreting 99mTc-DMSA scintigraphy. Altogether, the following data were obtained: 60.8% normal, 25.2% abnormal, 7.0% equivocal, and 3.2% lack of quality. The median percentage of agreement (overall reproducibility) for the 42 observers was 92%. When the results of all 42 observers were compared, the median agreements on normality and abnormality were 93.5% and 90.5%, respectively. In a small number (n = 4) of kidneys, reproducibility was poor and ranged from 51% to 70%. Except for 2 outliers, all observers had almost the same level of performance. CONCLUSION: A large number of Belgian nuclear medicine physicians participated in evaluating a large randomly selected sample of 99mTc-DMSA studies, and excellent interobserver agreement was found.

Adolescent↗

PubMed2000

Deconvolution analysis or renal outflow efficiency?

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Humans↗

PubMed1999

Evolution of single kidney glomerular filtration rate in urinary tract infection.

The aim of this study was to evaluate renal function during the acute phase of symptomatic urinary tract infection and the changes observed several months later. Overall glomerular filtration rate (GFR) as well as single kidney GFR (SKGFR) were calculated using the combination of a left/right uptake ratio obtained from technetium 99m-dimercaptosuccinic acid (DMSA) scintigraphy and 51chromium-EDTA plasma clearance. Forty-four patients with obvious unilateral or bilateral DMSA abnormalities were studied. In patients with unilateral lesions, both the overall GFR and the SKGFR were significantly higher during the acute phase of infection than several months later, on the abnormal side as well as the normal side. The relative percentage uptake was lower on the abnormal side than the normal side, obviously due to loss of functional parenchyma. This percentage increased significantly during the recovery phase, reflecting the total or partial healing of the renal lesions, despite the decrease of the corresponding SKGFR. However, during both the acute and the recovery phase, the relative percentage uptake of the abnormal kidney was in the normal range and often close to 50%. In patients with bilateral lesions, no significant changes were observed between the acute phase and the recovery phase.

Adolescent↗