Technetium 99m mercaptoacetyltriglycine gamma camera clearance calculations: methodological problems.

Major sources of errors in the gamma-camera methods for the calculation of renal clearance are the accuracy of background correction for obtaining the true renal time-activity curve and the validity of the externally recorded pre-cordial activity as an estimate of the plasmatic time-activity curve. With technetium 99m mercaptoacetyltriglycine (99mTc-MAG3), because of its high protein plasma binding, one could expect minimal extravascular diffusion and hence a more accurate externally detected plasmatic curve. The high extraction rate should reduce the influence of the background, but, on the other hand, the effect of hepatobiliary excretion on the calculation of renal clearance might be significant. Our results suggest that the hepatobiliary excretion of 99mTc-MAG3 does not influence the gamma-camera renal clearance determination, even in patients with low renal function. However, the pre-cordial curve does not reflect accurately the plasmatic disappearance curve; its calibration with a single plasma sample taken at the 20th min is responsible for significant errors, probably because of an unfavourable ratio between the intravascular and extravascular activities at the 20th min.     

Characteristics and biological behaviour of 99mTc-labelled hydroxyacetyltriglycine, a potential alternative to 99mTc-MAG3

Substitution of the oxidation-sensitive thiol function of mercaptoacetyltriglycine (MAG3) by a hydroxyl group yields a tetraligand (hydroxyacetyltriglycine or HAG3) which is almost insensitive to oxidation and has the advantage over MAG3 that it can be stored safely without protection of the alcohol function. We found that deprotected HAG3 could be directly labelled at alkaline pH (pH≥11.5) and room temperature in high yield (>95%). Results of electrophoresis experiments suggested a comparable structure for ^99mTc-HAG3 and ^99mTc-MAG3, namely binding of an oxotechnetium(V)core via three deprotonated amides and a deprotonated hydroxyl group. Biodistribution studies in mice at 10 min and 30 min p.i. showed a slightly higher urinary excretion, a faster renal transit and a significantly lower hepatobiliary handling for ^99mTc-HAG3 than for ^99mTc-MAG3. In a baboon, the 1-h plasma clearance of ^99mTc-HAG3 was clearly higher than that of ^99mTc-MAG3. Its plasma protein binding was in the same order as that of Hippuran and much lower than that of ^99mTc-MAG3. Evaluation in a human volunteer confirmed the favourable biological characteristics of ^99mTc-HAG3, namely a rapid renal excretion, a high 1-h plasma clearance and a negligible hepatobiliary handling. The results indicate that ^99mTc-HAG3 may be an easy-to-prepare and practical substitute for ^99mTc-MAG3 with improved renal excretion characteristics. Received 1 May and in revised form 18 July 1997     

99mTc-MAG3: Dynamic studies in patients with renal disease

Animal studies have suggested that ^99mTc-mercapto-acetylglycyl-glycyl-glycine (^99mTc-MAG3) might be suitable for the determination of the renal plasma flow (RPF) because of its high renal clearance. In this study ¹³¹I-orthoiodohippurate (¹³¹I-OIH) and ^99mTc-MAG3 (labeling always >95%) were administered simultaneously in 11 patients (creatinine clearance ranging from 14 to 130 ml/min per 1.73 m²) to measure effective RPF(ERPF) using the standard technique (UV/P). Glomerular filtration rate (GFR; clearance of ¹²⁵I-thalamate, ¹²⁵I-OT) was also measured. The mean ratio of ^99mTc-MAG3 clearance to ¹³¹I-IOH clearance was 0.55±0.02 (SEM), P<0.01, n=16, and was independant of GFR and ERPF. To study this difference in renal handling ofthe radiopharmaceuticals, renal extractions by the right kidney were determined in another six patients after a single shot of the agents. Renal extraction of ^99mTc-MAG3 was 0.60±0.03 after 5 min, and 0.41±0.08 after 30 min. Renal extraction of ¹³¹I-OIH amounted to 0.86±0.04 and 0.77±0.03, respectively. Using renal extractions of 0.41 and 0.77, respectively, it appeared that calculated renal plasma flows measured simultaneously with ^99mTc-MAG3 and ¹³¹I-OIH were similar. Protein binding 30 min after the priming dose was 66% for ^99mTc-MAG3 and 47% for ¹²³I-OIH. We conclude that in spite of a high renal clearance (ratio to ¹²⁵I-OT clearance 2.69±0.27), ^99mTc-MAG3 seems unsuitable for an accurate determination of the RPF. This conclusion is strongly supported bythe observation that the ratio of ^99mTc-MAG3 to ¹³¹I-IOH clearance markedly decreased from 0.66 to 0.32 in a patient with an increase in urinary protein loss.     

Transplant renography: 99m-Tc-DTPA versus 99m-Tc-MAG3. a preliminary note

^99mTc-MAG3 has been proposed as a replacement for both ¹³¹I-hippuran and ^99mTc-DTPA on clinical grounds. We undertook a prospective preliminary study to ascertain whether ^99mTc-MAG3 works better than ^99mTc-DTPA in the follow up of renal transplant recipients. Seventeen patients (21 renograms each MAG3 and DTPA) were studied, together, with a reference group of 10 patients in whom MAG3 and Hippuran clearance rates were determined simultaneously. As expected, ^99mTc-MAG3 analog images were excellent and ^99mTcMAG3 clearance correlated very well with ¹³¹I-hippuran clearance (r=0.978). MAG3 values were 60% of hippuran values. However, when the corresponding renographic and perfusion findings were faced with different diagnostic challenges, such as post transplant renal failure and rejection, ^99mTc MAG3 did not differ from ^99mTc-DTPA in a significant way. ^99mTc-DTPA was superior to ^99mtc-MAG3 in one case of rejection.     

Evaluation of the renal excretion characteristics of technetium-99m mercaptoacetylglycyl-D-alanylglycine in healthy volunteers

During a study of C-methyl derivatives of technetium-99m mercaptoacetyltriglycine (^99mTc-MAG3) it was found that the isomer of ^99mTc-mercaptoacetylgly-cyl-D-alanylglycine (^99m-TC-MAGAG-DA) is superior to ^99mTc-MAG₃ with regard to its renal excretion characteristics in both mice and the baboon. We have now compared the renal handling of ^99mTc-MAGAG-DA and ^99mTc-MAG₃ in 6 healthy volunteers in a paired study. Renograms of ^99mTc-MAGAG-DA show a shorter time to renal maximum and a lower residual renal activity at 30 min post-injection (p.i.). The urinary excretion of ^99mTc-MAGAG-DA is higher at both 30 and 60 min p.i. The plasma concentration of ^99mTc-MAGAG-DA is lower than that of ^99mTc-MAG₃ at each moment up to 60 min p.i., and the plasma clearance is accordingly higher. It is concluded that ^99mTc-MAGAG-DA is excreted more efficiently than ^99mTc-MAG₃, but the preparation of ^99mTc-MAGAG-DA requires a HPLC purification step, and this limits its practical clinical usefulness. Offprint requests to: G.M. Bormans     

Effect of renal maturation on the clearance of technetium-99m mercaptoacetyltriglycine

To investigate the effect of growth and maturation on the global kidney clearance of technetium-99m mercaptoacetyltriglycine (^99mTc-MAG3), we investigated 509 children who attended for^99mTc-MAG3 renography in our department. In order to estimate the normal maturation of the kidney, only children who were classified as “normal” using diagnostic criteria were included in this study (n=109). Kidney clearance was calculated using a gamma camera technique and a 20-min blood sample. There was a progressive increase in the clearance of^99mTc-MAG3 thoughout childhood and into adolescence (mean clearance value below 2 month was 31.4 ml/min, mean clearance value above 12 years was 287 ml/min). When clearance was normalised to body surface area (BSA) a different pattern was seen, with a progressive increase from 3 weeks of age (mean value <0.2 years: 208 ml/min/1.73 m²) to a plateau at the end of the first year of life (mean value >2 years: 303 ml/min/1.73 m²). Maturation of the kidney as defined by the normalised clearance of^99mTc-MAG3 is therefore complete by the end of the 1st year of life, after which any change in non-corrected clearance values may be attributed to growth. To investigate the appropriate normalisation factor for^99mTc-MAG3 clearance in children, clearance values were compared to height, weight and BSA. The relationships were described using a linear model; the correlation coefficients demonstrated that BSA has the highest strength of relationship with^99mTc-MAG3 clearance. Body surface area may be used over 1 year of age to normalise the clearance values of^99mTc-MAG3 Surprisingly, when clearance values are normalised to BSA, 68% of the mature clearance value is achieved at the age of <2 months of life.     

Technetium-99m ethylene dicysteine: a new renal tubular function agent

Technetium-99m ethylene dicysteine (EC), a metabolite of ethylene cysteine dimer (ECD), is a new technetium-labelled renal tubular function tracer introduced as an alternative to ortho-iodohippurate (OIH) and with imaging qualities similar to 99mTc-mercaptoacetyltriglycine (MAG3). The elimination of ^99mTc-EC is principally via active tubular transport. It is available in lyophilised kit form which can be easily prepared at room temperature, and the compound remains stable for at least 8 h. Both in normal individuals and in patients, plasma clearance of ^99mTc-EC has been reported to be around 0.75 of OIH clearance. Thus there is a very strict correlation between ^99mTc-EC and OIH clearance, and several algorithms are available to estimate OIH clearance from ^99mTc-EC clearance. The renal extraction ratio of ^99mTc-EC is 0.70. The distribution volume of ^99mTc-EC is twice that of ^99mTc-MAG3 (20% of body weight) and slightly higher than that of OIH. The plasma protein-bound fraction of ^99mTc-EC (30%) is significantly lower than that of ^99mTc-MAG3 and OIH. The same applies to red blood cell binding of ^99mTc-EC (5.7%). There is negligible uptake in the liver and intestines. Within 1 h 70% of ^99mTc-EC is excreted in the urine. ^99mTc-EC provides the same scintigraphic information as ^99mTc-MAG3. The lower liver activity makes ^99mTc-EC particularly attractive in patients with renal failure. The ^99mTc-EC clearance can be accurately estimated from a single plasma sample obtained at 54 min after injection. In conclusion, ^99mTc-EC is a suitable renal imaging agent and for some applications is even more attractive than OIH: it provides an index of tubular function and yields high-quality images. The labelling procedure is easy, radiochemical purity is high and the complex is stable for a long time. The extent to which ^99mTc-EC is adopted for clinical use will ultimately depend upon its cost and availability.     

Complexes of technetium-99m with tetrapeptides containing one alanyl and three glycyl moieties

Recently, we have shown that tetrapeptides can be efficiently labelled with technetium-99m by direct labelling at alkaline pH. Tetrapeptides can be considered derivatives of mercaptoacetyltriglycine (MAG3) in which the mercaptoacetyl moiety is replaced by an amino acid residue. In view of the interesting biological properties of some C-methyl substituted derivatives of^99mTc-MAG3, we have now synthesised and evaluated the complexes of^99mTc with tetrapeptides containing three glycyl (G) moieties and oned- orl-alanyl (A) moiety. In mice,^99mTc-l-GAGG,^99mTc-d-GGAG and^99mTc-l-GGAG showed a rapid and high renal excretion, comparable to that of^99mTc-MAG3. Renal handling was somewhat reduced for isomersd andl of^99mTc-AGGG and^99mTc-d-GAGG and markedly inferior for^99mTc-l-GGGA and^99mTc-d-GGGA. In the baboon,^99mTc-l-AGGG,^99mTc-d-AGGG and^99mTc-l-GAGG showed a comparable or even higher 1-h plasma clearance than^99mTc-MAG3.^99mTc-d-GAGG,^99mTc-l-GGAG and^99mTc-d-GGAG were characterised by a lower plasma clearance and the clearance of^99mTc-l-GGGA and^99mTc-d-GGGA was remarkably low. The three^99mTc-labelled tetrapeptides with the highest plasma clearance in a baboon were compared with^99mTc-MAG3 in a human volunteer.^99mTc-l-AGGG and^99mTc-l-GAGG had a roughly similar plasma clearance as^99mTc-MAG3. The clearance of^99mTc-d-AGGG was significantly lower and liver uptake was clearly visible with this compound. Left kidney renograms of^99mTc-l-AGGG and^99mTc-d-AGGG indicated moderate kidney accumulation. On the other hand, the renogram obtained after injection of^99mTc-l-GAGG had an excellent shape and the maximum kidney concentration was slightly higher than for^99mTc-MAG3. These results show the importance of the position of the methyl substituent on the^99mTc-tetrapeptide with respect to its biological behaviour.     

Technetium-99m-L,L-ethylenedicysteine scintigraphy in patients with renal disorders

Technetium-99m-L,L-ethylenedicysteine (^99mTc-L,L-EC), a new renal imaging agent, was introduced as an alternative to^99mTc-mercaptoacetyltriglycine (MAG3). This radiopharmaceutical can be easily labelled at room temperature and has high radiochemical purity and long stability. The aim of this study was to gain clinical experience in using^99mTc-L,L-EC in normal volunteers and patients. The clearance of this radiopharmaceutical was compared with that of iodine-131ortho-iodohippurate (OIH) in five healthy volunteers. In addition, conventional renogram and whole-body distribution of^99mTc-L,L-EC (40 min and 3 h post-injection) were evaluated in these subjects. Subsequently, ten patients with suspected obstructive nephropathy, four with renovascular disorders and two in acute renal failure were imaged. In five patients with impaired renal function both^99mTc-MAG3 and^99mTc-L,L-EC studies were performed. In each case the scintigraphic images and time/activity curves were evaluated and various semiquantitative parameters calculated and compared. No adverse effects were noted during and after^99mTc-L,L-EC scintigraphy. The mean clearance values for^99mTc-L,L-EC and¹³¹I-OIH in volunteers were 504 and 663 ml/min respectively. The total plasma clearance of^99mTc-L,L-EC was about 75.8% of the¹³¹I-0IH value. In volunteers the parenchymal transit time index, whole kidney transit time index and mean parenchymal transit time for^99mTc-L,L-EC were 63 s, 124 s and 175 s respectively. The mean time to peak activity was 235 s and the time from peak to 50% of peak activity was 402 s. In all patients the results of scintigraphy were concordant with clinical findings and subsequently influenced patient management. Furthermore,^99mTc-L,L-EC scintigraphy provided high-quality images similar to those obtained with^99mTc-MAG3, even at low glomerular filtration rates (18 ml/min). It is concluded that^99mTc-L,L-EC has excellent imaging characteristics similar to^99mTc-MAG3 and excretion properties similar to OIH. This radiopharmaceutical can be used routinely to evaluate patients with renal disorders.     

Extravascular chest wall technetium 99m diethylene triamine penta-acetic acid: implications for the measurement of renal function during renography

Measurement of individual kidney glomerular filtration rate (IKGFR) from the gamma-camera technetium 99m diethylene triamine penta-acetic acid (^99mTc-DTPA) renogram requires a continuous measurement of arterial activity. This is usually based on a region of interest (ROI) placed over the cardiac blood pool on the posterior view, with the assumption of negligible contamination from activity in the extravascular space of the chest wall. By injecting a small dose of technetium 99m human serum albumin (HSA) before the^99mTc-DTPA in 12 patients undergoing routine renography, the contribution of extravascular activity to the total signal recorded over the cardiac blood pool was calculated to be 11.0% (SE 2.1%) 1.5 min after DTPA injection, rising to 35.1% (SE 2.5%) at 15 min. Subtraction of the time-activity curve recorded from a ROI of the same size over the right lung generated a pure blood signal as shown by almost identical HSA/DTPA signal ratios recorded in blood samples taken 5 min after HSA and 15 min after DTPA and from the gamma-camera at the corresponding times. The effect of using a cardiac blood pool time-activity curve uncorrected for extravascular activity was to overestimate IKGFR by an average factor of 1.17 (SE 0.03). Offprint requests to: A.M. Peters     

Technetium-99m mercaptoacetyltriglycine clearance values in children with minimal renal disease: can a normal range be determined?

Use of technetium-99m labelled mercaptoacetyltriglycine (^99mTc-MAG3) simplifies and improves the quantification of renal clearance in children by virtue of its permanent availability, good imaging properties and low radiation exposure. Due to the lack of reference values for ^99mTc-MAG3 clearance in children, the Paediatric Task Group of the EANM initiated a multicentre study to evaluate ^99mTc-MAG3 clearance values in children with minimal renal disease. One hundred and twenty-five children aged between 12 months and 17 years, classified as renally healthy using defined diagnostic criteria, were included in the study. ^99mTc-MAG3 clearance was calculated using an algorithm on the basis of a single blood sample taken at any time between 30 and 40 min after tracer injection. In addition, the absolute ^99m-Tc-MAG3 clearance values were normalized to body surface area. For further evaluation the children were classified into several groups according to age. There was a continuous increase in non-corrected ^99mTc-MAG3 clearance values from the age of 1 year up to the age of 17 years (mean value <2 years: 98±57 ml/min; mean value >8 years: 208±66 ml/min). Normal clearance values for adults were achieved by the age of 8 years. Analysis of the relationship between non-corrected clearance and age yielded a correlation coefficient of r=0.7. When these absolute clearance values were normalized to body surface area, we found nearly constant clearance values for all age groups, with a mean clearance value of 315±114 ml/min×1.73 m². The correlation coefficient for the relationship between normalized clearance and age was r=0.28. In conclusion, the clearance of ^99mTc-MAG3 increases continuously throughout childhood into adolescence due to the maturation and growth of the kidney. After normalization of the absolute clearance to body surface area, no correlation between clearance and age could be proven. Received 16 June 1997 and in revised form 1 September 1997     

A new principle to normalize plasma concentrations allowing single-sample clearance determinations in both children and adults

A sufficiently accurate quantification of renal function requiring only one plasma sample without an additional gamma-camera study has, until now, only been possible in adults. A new principle will be presented here allowing the universal application of known algorithms, regardless of the clearance substance used, by normalizing the plasma concentrations with respect to the individual body dimensions of the patients - for infants as well as for adults. In this respect, algorithms are developed for clearance determinations using technetium-99m mercaptoacetyltriglycine (^99mTc-MAG3), which are based on steady-state studies as the reference. They allow the calculation of quantitative clearance values in infants, requiring only one blood sampling at any time between the 25th and the 40th min postinjection. The comparison with a combined camera/two-plasmasample technique performed in 46 children aged between 9 days and 14 years (mean 6.05 years) resulted in a standard error of 8.5% from the line of identity (r = 0.94). Moreover, this procedure also increases the accuracy of results in adults.Dedicated to Professor Peter Georgi on the occasion of his 60th birthday Offprint requests to: B. Bubeck     

Reproducibility of technetium-99m mercaptoacetyltriglycine clearance

The aim of this paper was to determine the reproducibility (precision) of technetium-99m mercaptoacetyltriglycine (MAG3) clearance and to compare it with that of chromium-51 ethylenediamine tetra-acetic acid (EDTA). Twelve young volunteers (aged between 21 and 34 years), without any history of medical problems, were enrolled in this study. The test was performed twice, at an interval of 8 days and under similar physiological conditions. After the intravenous injection of both tracers, 15 blood samples were taken between 3 and 240 min. A biexponential fit was adapted to the plasma disappearance curves (5- to 120-min samples for^99mTc-MAG3 and 10- to 240-min samples for⁵¹Cr-EDTA); the clearances were calculated according to Sapirstein and corrected for body surface area. The mean clearance values were 110 (range 85–130) and 226 (range 109–319) ml/min/1.73 m², respectively, for⁵¹Cr-EDTA and^99mTc-MAG3. For⁵¹Cr-EDTA clearance, the mean difference between the first and the second measurement was –2.1% of the mean of the two successive values (SD: 8.4%). In ten cases, the difference was less than 12%; in two cases, the differences were 15% and 18%, respectively. For^99mTc-MAG3 clearance, the mean difference between the first and the second measurement was –20% of the mean of the two successive values (SD: 25%). In six cases, the difference was less than 12%; in four cases, between 15% and 40%; and in two cases, more than 60%. Methodological factors (impurites contained in the commercial kit, variable protein binding) as well as physiological factors (pH of urine, sodium load, stress) may explain the lack of precision of the^99mTc-MAG3 clearance. It is concluded that changes in^99mTc-MAG3 plasma clearance should be interpreted with care in daily routine.     

Extravascular chest wall technetium 99m diethylene triamine penta-acetic acid: implications for the measurement of renal function during renography

Measurement of individual kidney glomerular filtration rate (IKGFR) from the gamma-camera technetium 99m diethylene triamine penta-acetic acid (99mTc-DTPA) renogram requires a continuous measurement of arterial activity. This is usually based on a region of interest (ROI) placed over the cardiac blood pool on the posterior view, with the assumption of negligible contamination from activity in the extravascular space of the chest wall. By injecting a small dose of technetium 99m human serum albumin (HSA) before the 99mTc-DTPA in 12 patients undergoing routine renography, the contribution of extravascular activity to the total signal recorded over the cardiac blood pool was calculated to be 11.0% (SE 2.1%) 1.5 min after DTPA injection, rising to 35.1% (SE 2.5%) at 15 min. Subtraction of the time-activity curve recorded from a ROI of the same size over the right lung generated a "pure" blood signal as shown by almost identical HSA/DTPA signal ratios recorded in blood samples taken 5 min after HSA and 15 min after DTPA and from the gamma-camera at the corresponding times. The effect of using a cardiac blood pool time-activity curve uncorrected for extravascular activity was to overestimate IKGFR by an average factor of 1.17 (SE 0.03).     

99mTc-DTPA gamma-camera renography: Normal values and rapid determination of single-kidney glomerular filtration rate

A method for ^99mTc-diethylenetriaminepentaacetate (DTPA) gamma-camera renography is presented. From each renogram, an uptake index (UI) proportional to the single-kidney glomerular filtration rate (SKGFR) is defined. If the proportionality factor between UI and SKGFR is the same in all patients, UI can be used as an accurate measure of SKGFR. In order to test this, ^99mTc-DTPA renography was performed in 101 patients with glomerular filtration rates (GFR) varying between 4 and 172 ml/min. The sum of the right-and left-kidney UIs correlated well with the total GFR calculated from the simultaneously measured plasma clearance of ^99mTc-DTPA after a single injection. The correlation coefficient was 0.97. The method was tested in a prospective study of 57 patients. The total GFR estimated from the renograms was not significantly different from the GFR calculated from the plasma clearance of ^99mTc-DTPA. The coefficient of variation—a combination of inaccuracy and imprecision in the estimates as well as in the reference values — was 11.8% at a GFR of 100 ml/min. It is concluded that, in adults, the SKGFR can be calculated as part of the clinical routine from ^99mTc-DTPA gamma-camera renography without determining the injected dose or collecting urine or blood samples. Normal values for some parameters of the renogram obtained in 25 normal subjects are given.     

Comparisons of the time-activity curves of the cardiac blood pool and liver uptake by99mTc-GSA dynamic SPECT and measured99mTc-GSA blood concentrations

OBJECTIVES: The aim of this study was to determine the time-activity curve in the cardiac and hepatic region by 99mTc-GSA dynamic SPECT which is clinically used in liver scintigraphy and evaluate the temporal changes in the consistency and errors at the absolute scale using the regression equation of changes in the blood concentration of 99mTc-GSA. METHODS: In 11 patients who underwent 99mTc-GSA dynamic SPECT over the 30 min period after IV injection, the percentages of activity in the collected blood and in the blood pool estimated by dynamic SPECT were determined as the plasma clearance by blood collection and as the blood clearance by cardiac pooling. Extrahepatic uptake, expressesd as 100--(% uptake in the liver by dynamic SPECT (%)) was calculated as the blood clearance by the liver. The regression equation (Y = Y0 + Ae(-alphat)) was determined from the changes in the counts, expressed as a percent. Percent errors and the differences in the Y-intercept (Y0), coefficient (A) and slope (alpha) on the regression curve were compared. RESULTS: Blood pool clearance gradually exceeded the measured plasma clearance. The clearance by the liver started from a very low initial value and gradually became equal to that of plasma clearance over the first 15 minutes and exceeded it over the second 15 minutes. The Y-intercept was significantly higher in the blood pool clearance than that in the measured plasma clearance (p < 0.001), and the coefficient was significantly lower in the former than the latter (p < 0.001). The coefficient and slope were significantly lower in the hepatic clearance than the plasma clearance (p < 0.001, p < 0.005). Conclusion: The time-activity curve of the blood pool showed a tendency towards overestimation in the second half of the examination, probably due to scatter effect from the liver. The time-activity curve of liver uptake showed a tendency towards overestimation in the first half of the examination, probably due to the high concentration in the hepatic blood pool, and underestimation in the second half.     

Differences between99mTc-DTPA and99mTc-MAG3 captopril renographies in renovascular hypertension

Captopril renography (CRS) with^99mTc-DTPA and^99mTc-MAG3 was performed on a 21-year-old woman with renovascular hypertension due to right renal artery stenosis caused by fibromuscular dysplasia. In the affected kidney, the renogram pattern was substantially changed with^99mTc-DTPA and^99mTc-MAG3 following the administration of captopril, and the quantitated renal uptake indicating individual renal function was significantly decreased in^99mTc-DTPA and slightly decreased in^99mTc-MAG3. In the contralateral normal kidney, the renogram showed some minor changes with both radioagents, while the quantitated renal uptake was significantly decreased with^99mTc-DTPA and substantially increased with^99mTc-MAG3. The combined use of physiologically different renal agents^99mTc-DTPA and^99mTc-MAG3 is helpful in investigating hemodynamic and functional changes in the stenosed kidney as well as the normal kidney in RVH.     

Technetium Tc 99m plasmin in the diagnosis of inflammatory disease

The localization characteristics of technetium Tc 99m plasmin were studied in experimental animals to investigate the use of^99mTc-plasmin for imaging inflammatory processes. At various times after abscess induction using turpentine in rats, the in vivo distribution properties of^99mTc-plasmin, gallium citrate Ga 67,¹²⁵I-fibrinogen, and^99mTc-human serum albumin (HSA) were studied by gamma-camera imaging. The in vivo binding of each radiopharmaceutical was also tested in rat and human plasma clots. Region-of-interest analyses of gamma-camera images showed relatively poor^99mTc-plasmin localization at sites of abscess formation. The ratio of abscess-to-control activity of this radiopharmaceutical did not exceed that of⁶⁷Ga,¹²⁵I-fibrinogen, or^99mTc-HSA. In vitro assays of each of the radiopharmaceuticals in plasma clots showed^99mTc-phasmin and¹²⁵I-fibrinogen to have the best localization characteristics.     

Comparison of 99mTc-mercaptoacetyltriglycine and [131I]-o-iodohippurate elimination in perfused rat kidney

Renal elimination of two renal radiodiagnostic agents, (99m)Tc-mercaptoacetyltriglycine ((99m)Tc-MAG3) and [(131)I]-o-iodohippurate (OIH) has been studied using the method of the perfused rat kidney. The experiments showed significant differences between renal handling of (99m)Tc-MAG3 and OIH in the perfused rat kidney. While the renal clearance for (99m)Tc-MAG3 was relatively stable, the renal clearance values of OIH rapidly decreased after the OIH administration in a bolus dose. The infusion administration of OIH resulted in stable clearance values during the perfusion. The OIH/(99m)Tc-MAG3 renal clearance ratio was 2.47. Both compounds were bound to proteins in the perfusate to a considerable extent. An analysis of renal handling showed that contribution of tubular secretion to the total excretion was 95% for OIH, and 97% for (99m)Tc-MAG3.     

Comparison of radionuclide estimation of glomerular filtration rate using technetium 99m diethylenetriaminepentaacetic acid and chromium 51 ethylenediaminetetraacetic acid

Simultaneous measurements of the clearance rates of technetium 99m diethylenetriaminepentaacetic acid (^99mTc-DTPA) and chronium 51 ethylenediaminetetraacetic acid (⁵¹Cr-EDTA) were performed in 30 patients with a range of renal function (glomerular filtration rates between 9 and 120 ml/min). Using multiple blood samples, the two clearance values correlated well (r=0.991, standard error 3.9 ml/min), but DTPA clearance was systematically higher by 7.6%. For each radiopharmaceutical, an equation was derived to correct clearance values obtained using only plasma samples taken at 2 and 4 h for the systematic error inherent in this technique compared with analysis of the complete plasma concentration-time curve. The root mean square error remaining after application of these equations was 1.9 ml/min for both the EDTA and DTPA data. The corresponding errors obtained using the equation derived by Brochner-Mortensen for EDTA plasma clearance were 2.2 ml/min and 1.9 ml/min, respectively, these values were not significantly different from those obtained using the equations derived in this study.