Prospective validation of a single sample technique to determine technetium-99m-MAG3 clearance.
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Technetium-99m-MAG3 clearance is proportional to OIH clearance and can be used directly as a measure of renal function. Multiple plasma sample, two-compartment clearance data from three studies were recently pooled to develop a single-sample regression equation for determining the clearance of 99mTc-MAG3. To test this published equation, a prospective study was conducted in 34 patients with a wide range of renal function. Multiple plasma samples were obtained from 9 to 60 min following the bolus injection of 99mTc-MAG3 and the clearances were calculated based on a single injection, two-compartment model. Clearances were also calculated using a single 43-min plasma sample and the published regression equation. There was an excellent correlation (r = 0.976) between the two clearances; the slope of the regression line was 1.01 with an intercept of -26.6; the standard error of the estimate was 24 ml/min. In conclusion, the current regression equation provides a good estimate of 99mTc-MAG3 clearance. (+info)
Prognostic value of captopril renal scintigraphy in renovascular hypertension.
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This study evaluates the prognostic value of captopril renal scintigraphy in hypertensive patients undergoing renal artery revascularization. Preoperative studies of 51 patients were correlated with blood pressure results at 6- and 12-mo follow-up. Captopril-renal scintigraphy was carried out 1 hr after oral administration of 50 mg of captopril, using either 220 MBq of 99mTc-DTPA or 74 MBq of 99mTc-MAG3, followed by a baseline study in case of abnormal results. Evidence of amelioration or normalization in relation to captopril study was considered predictive of blood pressure control following treatment. Blood pressure response was favorable in 37 patients, but failed to show any improvement in 14. The scintigraphic test was positive in 33 patients (15 cured, 17 improved, 1 failed) and negative in 18 (3 cured, 2 improved, 13 failed). Sensitivity and specificity for renovascular hypertension was 86.5% and 93%, respectively. For blood pressure cure and improvement, the test had positive and negative predictive values of 97% and 72%, respectively. A positive preoperative captopril renal scintigraphic result is a strong predictor of hypertension curability by renal artery revascularization. (+info)
The "well tempered" diuretic renogram: a standard method to examine the asymptomatic neonate with hydronephrosis or hydroureteronephrosis. A report from combined meetings of The Society for Fetal Urology and members of The Pediatric Nuclear Medicine Council--The Society of Nuclear Medicine.
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Perinatal hydronephrosis (HN) and hydroureteronephrosis (HUN) are recognized more frequently as the routine use of prenatal ultrasonography increases. The decision-making process for those instances of urinary tract dilatation that require surgical correction and those that do not is based in part on the findings of diuresis renography. The methodology for performing this test has differed among nuclear medicine practitioners and the surgical findings are occasionally discrepant from the diuretic renogram interpretation. Consequently, the Society of Fetal Urology (SFU) and the Pediatric Nuclear Medicine Council (PNMC) of the Society of Nuclear Medicine met to develop by consensus a more uniform methodology. A standard method has been agreed upon for the following facets of diuretic renography: patient preparation (hydration and bladder catheterization), diuresis renography technique (radiopharmaceutical used, patient position during examination, data acquisition parameters, diuretic pharmaceutical and dosage, time of injection and regions of interest to monitor diuretic effect), and data analysis (percent differential renal function, curve pattern analysis and methods of measuring diuretic response). Pooled diuresis renogram data are being collected for analysis for correlation with surgical results and clinical outcomes to determine the most appropriate information to be derived from the diuretic renogram in neonates with HN and HUN. (+info)
Administered activity optimization in 99mTc-MAG3 renography for adults.
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OBJECTIVE: The objective of this work was to determine the minimum administered activity of (99m)Tc-mercaptoacetyltriglycine (MAG3) needed both to estimate effective renal plasma flow (ERPF) with adequate precision and to obtain good image quality. METHODS: Three groups of 10 patients each were injected with 45, 71, or 132 MBq of MAG3. Renograms and perfusion and clearance images were obtained. The age, sex, and weight of the patients; the labeling yield; the mean count and counting rate 2 min after injection; the kidney-to-background and cortex-to-background ratios; the uptake time from the renograms; the percentage of the injected activity 2 min after injection in the left and right kidneys (A2(LK) and A2(RK), respectively); and the ERPF for both kidneys were obtained and analyzed. Discriminant analysis of image quality was used to select the variables that most affected image quality. The selected variables were studied among activity groups to optimize the amount of activity administered in these studies. RESULTS: Precision in ERPF assessment did not significantly differ among administered activity levels (P = 0.824). The SDs of the ERPF were +/-1.5 for 132 MBq, +/-1.7 for 71 MBq, and +/-2.0 for 45 MBq. The labeling yield, the ratios of counts in the left and right kidneys to the background and in the left and right cortices to the background, and A2(LK) and A2(RK) were the only variables that provided a significant discriminant function for image quality. The only variable that significantly differed with the variation in administered activity was the ratio of counts in the right kidney to the background (P = 0.026), most likely because of the labeling yield. CONCLUSION: A 45-MBq activity is sufficient to guarantee good image quality and adequate precision in ERPF determination from the time-activity curve, provided the labeling yield is kept high. (+info)
Transport of 99mTc-MAG3 via rat renal organic anion transporter 1.
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Recently, complementary DNA (cDNA) encoding a p-aminohippurate (PAH) transporter designated rat organic anion transporter 1 (OAT1) was isolated. OAT1, a multispecific organic anion transporter at the basolateral membrane, is exclusively expressed in the middle segment of the proximal tubule in the rat kidney. It has been proposed that OAT1 is indirectly involved in PAH uptake via the Na(+) dicarboxylate cotransporter. In this study, in molecular biologic experiments using OAT1-expressing Xenopus laevis oocytes, we obtained evidence that (99m)Tc-mercaptoacetylglycylglycylglycine (MAG3) is transported via OAT1. METHODS: Capped OAT1 complementary RNA (cRNA) was synthesized from library plasmid cDNA linearized with BamHI using in vitro transcription. Defolliculated oocytes were injected with 10 ng of OAT1 cRNA. Two to 3 d after injection, uptake of (99m)Tc-MAG3 was measured using ND96 solution containing 18.5 kBq of (99m)Tc-MAG3. Before the uptake experiments, OAT1-expressing oocytes were preincubated for 2 h with 1 mmol/L glutarate (a dicarboxylate), to generate an outwardly directed glutarate gradient. Then, after incubation for 60 min at room temperature, radioactivity of oocytes was determined. For the inhibition experiments, uptake was assessed in the absence or presence of inhibitor: 2 mmol/L of PAH, o-iodohippurate (OIH), probenecid, 3,5-diiodo-4-pyridone-N-acetate (iodopyracet), furosemide, ethacrynic acid, glucoheptonate, maleic acid, L-Tyr, or tetraethylammonium (TEA) or 0.1 mmol/L of 2,4-dinitrophenol (DNP). RESULTS: Na(+) had a significant effect on (99m)Tc-MAG3 uptake (P < 0.05). Accumulated glutarate stimulated simultaneous (99m)Tc-MAG3 uptake and glutarate excretion (P < 0.001). The following compounds significantly inhibited (99m)Tc-MAG3 uptake: PAH, 8.5% +/- 16.2% of (99m)Tc-MAG3 uptake in the absence of an inhibitor; OIH, 26.4% +/- 21.7%; probenecid, 29.1% +/- 12.4%; iodopyracet, 15.8% +/- 7.9%; furosemide, 30.5% +/- 15.7%; ethacrynic acid, 21.6% +/- 10.6%; glucoheptonate, 35.6% +/- 22.6%; and maleic acid, 60.1% +/- 18.7%. (99m)Tc-MAG3 accumulation in Xenopus laevis oocytes was not significantly inhibited by TEA, L-Tyr, or DNP. CONCLUSION: The following substances had a cis-inhibitory effect on (99m)Tc-MAG3 transport: PAH, OIH, probenecid, iodopyracet, furosemide, ethacrynic acid, and glucoheptonate. Glutarate had a trans-stimulative effect on (99m)Tc-MAG3 transport. (99m)Tc-MAG3 acts as a substrate of OAT1, an organic anion/dicarboxylate exchanger. (+info)
New automated physical phantom for renography.
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Physical phantoms have been used to test the diagnostic proficiency of nuclear medicine professionals and the accuracy of their equipment in external quality assurance surveys. No dynamic renal phantoms are commercially available. A new renal phantom, presented in this paper, was constructed and patented in the United States. METHODS: The organs to be simulated by the phantom were in the form of containers filled with radioactive solution, and the device further comprised movable steel and lead plates between the containers and the gamma-camera. The detectable radiation was regulated in accordance with automated computer-controlled step motors to move the attenuators to simulate a given patient situation. The reproducibility of the phantom measurements was defined as a coefficient of variation. Four different kidney-function simulations were repeated 3 times, and 6 parameters were compared. RESULTS: The average root mean square deviation of the coefficient of variation was 6.7% for the perfusion integral, 1.3% for time to reach the maximum activity, 19.7% for mean transit time, 3.3% for function (Patlak [%]), 1.0% for outflow index (%), and 6.5% for time to reach the half-activity from maximum. CONCLUSION: With this phantom, the true values of most parameters measured are well known; it closely approaches true extraction, washout, and attenuation properties and curves, and the images produced are similar to those of patient studies. Compared with the first manual version, this new automated phantom is easy to use. Any desired clinical situation can be programmed. It is a promising tool for quality assurance and calibration of renography. (+info)
Elimination of the influence of total renal function on renal output efficiency and normalized residual activity.
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One of the potential limitations in the usefulness of both renal output efficiency (ROE) and normalized residual activity (NORA) is their residual dependence on total renal function. The purpose of this study was to present and examine a new quantitative method whereby the effects of this dependence may be removed. METHODS: The analytic method involves the determination of a retention function using an unconstrained matrix algorithm deconvolution technique followed by reconvolution with a chosen standard input function to yield a new secondary renal activity time (A/T) curve from which normalized values of ROE and NORA, denoted as N_ROE and N_NORA, respectively, can then be obtained using conventional definitions. The method has been applied in a series of 50 patient studies, which had been acquired using (99m)Tc-mercaptoacetyltriglycine (99(m)Tc-MAG3) and a standard F+18 furosemide protocol, with values of the ratio of plasma clearance to plasma volume (C/V) in the range 0.013-0.242 min(-1). RESULTS: Pre- and postnormalization values of NORA, calculated at 30 min after injection, showed a significant difference in mean values (paired t test; P < 0.001), with a maximum observed difference, DeltaNORA(30), of -4.82 (-482%) and with a SD on the paired differences, DeltaNORA(30), of 0.56 (56%) or 0.63 (63%) if background subtraction on the input function (BSIF) had been performed. In contrast, corresponding values of ROE showed a nonsignificant difference in means (P > 0.05) and a SD on the paired differences, DeltaROE(30), of 3.7% or 3.2% with and without BSIF, respectively. The normalized parameters N_ROE and N_NORA were found to be strongly linearly correlated (r = -0.99; P < 0.001), in agreement with theoretical predictions. CONCLUSION: These results suggest that renal function affects NORA significantly more than ROE. The effects can be corrected by our normalization technique, resulting in equivalent values of normalized ROE and normalized NORA. (+info)
99mTc-MAEC complexes: new renal radiopharmaceuticals combining characteristics of (99m)Tc-MAG3 and (99m)Tc-EC.
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99mTc-Mercaptoacetyltriglycine ((99m)Tc-MAG3) and (99m)Tc-L,L-ethylenedicysteine ((99m)Tc-LL-EC) are useful renal radiopharmaceuticals; however, both agents have renal clearances less than that of (131)I-orthoiodohippurate ((131)I-OIH), and (99m)Tc-LL-EC exists in dianionic and monoanionic forms at physiologic pH. In an effort to develop a superior (99m)Tc agent with a rapid clearance comparable with that of (131)I-OIH, we have designed a new ligand system, mercaptoacetamide-ethylene-cysteine (MAEC), which combines important structural features of both MAG3 and EC. METHODS: Biodistribution and clearance studies were performed on Sprague-Dawley rats using syn- and anti-(99m)Tc-L- and -D-MAEC coinjected with (131)I-OIH. Studies were also performed by coinjecting each isomer ( approximately 74 MBq [ approximately 2 mCi]) and 7.4-11.1 MBq (200-300 micro Ci) of (131)I-OIH in 3 volunteers with dual-isotope imaging performed using a camera system fitted with a high-energy collimator. Blood samples were obtained from 3 to 90 min after injection and urine samples were obtained at 30, 90, and 180 min. RESULTS: In the rats, <10% of the injected dose remained in the blood at 10 min after injection for all isomers, and the urine dose at 60 min ranged from 84% to 99% that of (131)I-OIH. The clearances of syn- and anti-(99m)Tc-L-MAEC in the rats were higher than the clearances for the D-isomers (P +info)