Detection of early changes in renal function using 99mTc-MAG3 imaging in a murine model of ischemia-reperfusion injury.
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Accurate determination of renal function in mice is a major impediment to the use of murine models in acute kidney injury. The purpose of this study was to determine whether early changes in renal function could be detected using dynamic gamma camera imaging in a mouse model of ischemia-reperfusion (I/R) injury. C57BL/6 mice (n = 5/group) underwent a right nephrectomy, followed by either 30 min of I/R injury or sham surgery of the remaining kidney. Dynamic renal studies (21 min, 10 s/frame) were conducted before surgery (baseline) and at 5, 24, and 48 h by injection of (99m)Tc-mercaptoacetyltriglycine (MAG3; approximately 1.0 mCi/mouse) via the tail vein. The percentage of injected dose (%ID) in the kidney was calculated for each 10-s interval after MAG3 injection, using standard region of interest analyses. A defect in renal function in I/R-treated mice was detected as early as 5 h after surgery compared with sham-treated mice, identified by the increased %ID (at peak) in the I/R-treated kidneys at 100 s (P < 0.01) that remained significantly higher than sham-treated mice for the duration of the scan until 600 s (P < 0.05). At 48 h, the renal scan demonstrated functional renal recovery of the I/R mice and was comparable to sham-treated mice. Our study shows that using dynamic imaging, renal dysfunction can be detected and quantified reliably as early as 5 h after I/R insult, allowing for evaluation of early treatment interventions. (+info)
Noninvasive imaging of human telomerase reverse transcriptase (hTERT) messenger RNA with 99mTc-radiolabeled antisense probes in malignant tumors.
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The expression of human telomerase reverse transcriptase (hTERT) is present in most malignant cells (>85%) but is undetectable in most normal somatic cells. Visualization of hTERT expression using radionuclide targeting can provide important diagnostic information in malignant tumors. The overall aim of this study was to evaluate whether (99m)Tc-radiolabeled antisense oligonucleotide (ASON) targeting hTERT messenger RNA (mRNA) can be used for imaging of hTERT expression in vivo. METHODS: One 18-mer antisense or sense uniformly phosphorothioate-modified oligonucleotide targeting hTERT mRNA was radiolabeled with (99m)Tc through the bifunctional chelator N-hydroxysuccinimidyl derivative of S-acetylmercaptoacetyltriglycine (S-acetyl NHS-MAG3). Then the radiolabeled probe was characterized in vitro. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to assay the mRNA level after proliferating cells had been incubated with the antisense and sense probes. (99m)Tc-MAG3-ASON or (99m)Tc-MAG3-SON was injected intravenously in mammary tumor-bearing BALB/c nude mice. Biodistribution and in vivo imaging was performed periodically. All data were analyzed by statistical software. RESULTS: The labeling efficiencies of (99m)Tc-MAG3-ASON/SON reached 76% +/- 5% (n = 5) within 15-30 min at room temperature, the specific activity was up to 1,850 kBq/mug, and the radiochemical purity was >96% after purification. (99m)Tc-MAG3-ASON showed complete stability at room temperature and in fresh 37 degrees C human serum. In comparison with (99m)Tc-MAG3-SON, (99m)Tc-MAG3-ASON preserved the capacity to bind living hTERT-expressing cells specifically and to inhibit the expression of hTERT mRNA significantly as well as ASON. In nude mice bearing hTERT-expressing MCF-7 xenografts, tumor radioactivity uptake of (99m)Tc-MAG3-ASON after injection was significantly higher than that of (99m)Tc-MAG3-SON after injection (P < 0.05). The hTERT-expressing xenografts were clearly imaged at 4-8 h noninvasively after injection of (99m)Tc-MAG3-ASON, whereas the xenografts were not imaged at any time after injection of (99m)Tc-MAG3-SON. CONCLUSION: This in vivo study provides evidence that (99m)Tc-MAG3-ASON targeting hTERT mRNA can be used as a potential candidate for visualization of hTERT expression in carcinomas. (+info)
Optimal scintigraphic evaluation of a hydronephrotic horseshoe kidney.
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A 25-y-old man with horseshoe kidney was referred for diuretic-augmented renal scintigraphy. Single-detector dynamic posterior imaging was performed and revealed asymmetric retention of radiotracer in the left collecting system. Renal scintigraphy was repeated with a modified protocol. Dynamic imaging was performed this time using dual-detector acquisition of both anterior and posterior data. Thereafter, pregravity and subsequently postgravity static images were obtained in both anterior and posterior projections. This second study showed near-complete emptying of the left collecting system. This case illustrates the utility of using simultaneous anterior and posterior imaging and geometric mean calculations for functional analysis and also highlights the value of physiologic maneuvers to augment the traditional diuretic challenge. (+info)
Decision support systems in diuresis renography.
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The volume of diagnostic imaging studies performed in the United States is rapidly increasing resulting from an increase in the number of patients as well as an increase in the volume of studies per patient. Concurrently, the number and complexity of images in each patient data set are also increasing. Nuclear medicine physicians and radiologists are required to master an ever-expanding knowledge base whereas the hours available to master this knowledge base and apply it to specific tasks are steadily shrinking. The convergence of an expanding knowledge base and escalating time constraints increases the likelihood of physician errors. The problem is particularly acute for low-volume studies such as MAG3 diuresis renography where many imagers may have had limited training or experience. To address this problem, renal decision support systems (DSS) are being developed to assist physicians evaluate suspected obstruction in patients referred for diuresis renography. Categories of DSS include neural networks, case-based reasoning, expert systems and statistical systems; RENEX and CART are examples of renal DSS currently in development. RENEX (renal expert) uses a set of rules obtained from human experts to analyze a knowledge base of expanded quantitative parameters obtained from diuresis MAG3 scintigraphy whereas CART (classification and regression tree analysis) is a statistical method that grows and prunes a decision tree based on an analysis of these quantitative parameters in a training data set. RENEX can be queried to provide the reasons for its conclusions. Initial data show that the interpretations provided by RENEX and CART are comparable to the interpretations of a panel of experts blinded to clinical information. This project should serve as a benchmark for the scientific comparison and collaboration of these 2 fields of medical decision-making. Moreover, we anticipate that these DSS will better define the essential interpretative criteria, foster standardized interpretation, teach trainees to better interpret renal scans, enhance diagnostic accuracy and provide a methodology applicable to other diagnostic problems in radiology and medicine. (+info)
Stabilization of renal function, improvement in blood pressure control and pulmonary edema symptoms after opening a totally occluded renal artery.
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Stenting has emerged as a procedure associated with low mortality and morbidity for symptomatic renovascular disease. However, percutaneous revascularization of chronically occluded renal arteries has not been reported. We report a case of a patient with refractory hypertension and congestive heart failure with unilateral occlusion of the left renal artery. Renal radionuclide scintigraphy with Tc-MAG3 showed residual left renal function for which percutaneous revascularization and stenting were successfully performed with improvement in symptoms and blood pressure control. Following recanalization, the presence of collateral vessels through the capsule of the kidney was noted, possibly maintaining viability of the renal parenchyma. This is a case of percutaneous revascularization of a chronic total occlusion leading to improvement in hypertensive and congestive symptoms. (+info)
Diagnostic performance of an expert system for interpretation of 99mTc MAG3 scans in suspected renal obstruction.
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Use of technetium-99m-MAG3 for renal scintigraphy after angiotensin-converting enzyme inhibition.
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Technetium-99m-mercaptoacetyltriglycine (99mTc-MAG3) was tested in 82 hypertensive patients submitted to renal scintigraphy 1 hr after oral premedication with 50 mg of Captopril. Baseline studies were obtained only for those patients showing abnormal findings in the provocative study. All patients underwent renal arteriography. Sensitivity and specificity for the detection of renal artery stenosis (RAS) greater than 50% were 89% and 91%, respectively. After Captopril administration, tracer parenchymal transit time increased significantly in ischemic kidneys (334 +/- 93 sec in baseline conditions versus 468 +/- 96 sec after Captopril, p less than 0.001) but not in kidneys with no RAS or RAS less than 50% (243 +/- 46 sec versus 271 +/- 95 sec, p = ns). False-positive responses were mostly bilateral and associated with a marked decrease in blood pressure. Technetium-99m-MAG3 is an effective compound for detecting RAS greater than or equal to 50% with Captopril renal scintigraphy. Performing the provocative test as a first step considerably reduced the number of scintigraphic studies required. (+info)
Estimation of technetium-99m-MAG3 renal clearance in children: two gamma camera techniques compared with multiple plasma samples.
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Dynamic renal scintigraphy using technetium-99m mercaptoacetylglycylglycylglycine (MAG3) has been described in adults, and clearance values have been established using multiple plasma samples. This study of renal clearance has compared two fundamentally different gamma camera techniques (both of which require a single blood sample) with the multiple blood sampling technique in children (n = 30). Results show that a 40-min dynamic 99mTc-MAG3 renal scintigram coupled with a single plasma sample will allow analysis of the data so that clearance values, which are similar to those from multiple plasma samples, may be calculated. The curve generated from the cardiac region of interest (ROI) provided clearances values that had a high correlation coefficient (0.939-0.951) compared to the multiple-plasma sample technique immaterial of the timing of the blood sample. The renal uptake method of clearance had a lower correlation coefficient (0.89-0.92), which varied with the timing of the blood sample compared to the multiple-plasma sampling technique. This study has demonstrated that an extended gamma camera acquisition coupled with a single-plasma sample may be used for quantitative renal function studies using 99mTc-MAG3. (+info)