Inflammation and infection imaging with a 99mTc-neutrophil elastase inhibitor in monkeys.
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A radiolabeled human neutrophil elastase inhibitor (EPI-HNE-2) may represent an improved nuclear medicine imaging agent for inflammation and infection. This peptide displays rapid pharmacokinetics due to its low molecular weight and localizes specifically on neutrophil elastase released in inflammatory sites by activated neutrophils. METHODS: In this investigation, the peptide was radiolabeled with 99mTc using N-hydroxysuccinimidyl S-acetylmercaptoacetyltriglycline (NHS-MAG3) as a bifunctional chelator and was administered on 18 occasions to 5 rhesus monkeys with inflammation/infection. RESULTS: Plasma clearance was rapid, with liver and kidneys representing the major organs of accumulation. No evidence of toxicity, dosage effects, or circulating antiMAG3-EPI-HNE-2 antibodies was observed. Specificity of localization was established using radiolabeled bovine pancreatic trypsin inhibitor (a non-hNE-binding peptide of similar size) as a nonspecific negative control peptide and by predosing with unlabeled EPI-HNE-2 to block receptor sites before the administration of radiolabeled EPI-HNE-2. The ability of radiolabeled EPI-HNE-2 to image inflammation/infection was evaluated in 12 studies in monkeys receiving only radiolabeled EPI-HNE-2 and with lesions in the arm, shoulder, or lower back. Positive images were obtained in all studies, uptake was apparent almost immediately, and images were still positive 24 h later. As a positive control, animals also received nonspecific IgG antibody radiolabeled with 99mTc either directly or by NHS-MAG3. Compared with labeled antibody, plasma clearance of 99mTc was faster with labeled EPI-HNE-2 and accumulation in liver and heart was lower. Uptake of radioactivity in the inflammation was higher during the first hour with EPI-HNE-2 versus antibody but lower thereafter. CONCLUSION: When radiolabeled with 99mTc, EPI-HNE-2 localized specifically in inflammations in a monkey model and provided early images of diagnostic quality. (+info)
Diuretic renography with the addition of quantitative gravity-assisted drainage in infants and children.
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The aim of this study was to evaluate the use of quantitative gravity-assisted drainage (GAD) using >50% residual activity as an indicator to confirm obstruction in diuretic renography in the investigation of hydronephrosis and hydroureteronephrosis in infants and children. This was evaluated in 2 groups: furosemide clearance half-time (t 1/2) > 20 min (obstructed range) and t 1/2 = 10-20 min (indeterminate range). METHODS: Two hundred children (155 boys, 45 girls; age range, 2 d to 16 y; median age, 26 wk) were studied over a 2-y period. One hundred thirty-five F+20 (diuretic given 20 min after radiopharmaceutical) and 65 F+0 (simultaneous administration of diuretic and radiopharmaceutical) studies were performed with intravenous administration of 99mTc-mercaptoacetyltriglycine (MAG3) and furosemide. At the end of the 20-min diuretic phase, a 5-min post-GAD image was obtained, and the percentage of residual activity was calculated by comparison with the last 5 min of the diuretic phase. All patients were monitored for 6-12 mo, and the final diagnoses were based on either surgical findings or conservative management with follow-up sonography or 99mTc-MAG3 studies. Results of the diuretic renography using quantitative GAD were then compared with the final diagnoses. RESULTS: A renal unit was defined as a kidney and its ureter. In the 200 patients studied, 256 hydronephrotic renal units were analyzed: 10 units showed no function, 1 unit showed poor function, 131 units had t 1/2 < 10 min, 62 units had t 1/2 > 20 min, and 52 units had t 1/2 = 10-20 min. Of the 131 renal units with t 1/2 < 10 min, there was only 1 case of obstruction. Using GAD > 50% residual activity for the diagnosis of obstruction in 62 renal units with t 1/2 > 20 min, the sensitivity was 88.4%, the specificity was 73.7%, and the accuracy was 83.9%. Similarly, using GAD > 50% residual activity for the diagnosis of obstruction in 52 units with t 1/2 = 10-20 min, the sensitivity was 100%, the specificity was 79.5%, and the accuracy was 82.7%. CONCLUSION: The quantitation of GAD > 50% residual activity in diuretic renography can help to differentiate between obstruction and nonobstruction in renal units with t 1/2 > 20 min and t 1/2 = 10-20 min. The quantitation of GAD when t 1/2 < 10 min is not useful because obstruction has already been excluded. (+info)
Diuretic MAG3 scintirenography in children with HIV nephropathy: diffuse parenchymal dysfunction.
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HIV nephropathy (HIVN) is prevalent in 15%-56% of HIV-infected children and induces mild to severe progressive nephropathy. METHODS: A total of 33 renal diuretic scintirenographic studies with 99mTc-mercaptoacetyltriglycine (MAG3) were reviewed and analyzed from 23 HIV pediatric patients, 21 of whom had HIVN with varying degrees of renal impairment. Results were compared with 10 studies of control patients of matching ages. Visual interpretation of images and renograms as well as semiquantitative analyses were performed. Variables compared were size of kidneys, time of peak and one-half peak activities, residual (or retained) cortical activity at 20 min, ratio of cortical activity at 2.5-20 min, and ratio of kidney activity to kidney plus background activity at 2 min. The results of MAG3 renal studies were also compared with laboratory data pertaining to creatinine clearance in all patients and with sonography in 17 patients. RESULTS: In most patients with HIVN (18/21), the kidneys were larger than normal, with a diffuse parenchymal dysfunction (decreased uptake, slow processing, and increased retention of activity) and flat renograms, findings similar to those observed in other diffuse parenchymal diseases. In all patients with HIVN, semiquantitative analysis (paired t test) showed statistically significant differences from control patients for all variables. On ANOVA, a statistically significant correlation was found between most scintigraphic parameters and the severity of renal impairment. Of the 17 concurrent sonographic studies in HIVN patients, 7 showed no abnormalities, whereas the results of scintigraphy were abnormal. CONCLUSION: Diuretic MAG3 scintirenography shows nonspecific diffuse parenchymal dysfunction in pediatric patients with HIVN. Such dysfunction may provide corroborative evidence of HIVN and should be recognized when the test is performed for standard indications. Further work is necessary to prove that the test has indeed the high sensitivity and good correlation with the seventy of HIVN suggested in this population; the test may be useful to follow up the progression of disease and the effect of treatment. (+info)
Captopril-induced changes in MAG3 clearance in patients with renal arterial stenosis and the effect of renal angioplasty.
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Angiotensin-converting enzyme inhibition by captopril decreases renal (131)I-o-iodohippurate sodium or iothalamate extraction in patients with renal artery stenosis (RAS). This study investigated the effect of captopril on another renal radiopharmaceutical, (99m)Tc-mercaptoacetyltriglycine (MAG3), in particular its plasma clearance. METHODS: Three groups of patients were studied. Group I contained 22 patients with hypertension but a low likelihood of RAS according to negative captopril renography results, confirmed by angiography in 5. Group II contained 22 hypertensive patients with RAS documented by angiography and positive captopril and plasma renin response. Group III contained 10 patients after successful percutaneous transluminal renal angioplasty (PTRA) with negative captopril renography results. The 60-min, single-sample technique was used for measurement of the plasma clearance of MAG3 during baseline and captopril renography. RESULTS: In 18 of 22 group I patients, clearance increased (P < 0.01) during captopril renography compared with baseline conditions, whereas in 18 of 22 group II patients, clearance decreased (P< 0.01). In group III patients, clearance was not significantly altered. The clearance decrease in group II did not correlate with the blood pressure decrease or plasma renin activity increase during captopril renography. CONCLUSION: Renal function assessed by MAG3 plasma clearance decreases in hypertensive patients with RAS but increases in patients without RAS. MAG3 clearance measurements during baseline and captopril renography can thus serve as additional diagnostic information when investigating patients with hypertension for the possibility of an RAS. (+info)
Prediction of renal transplant survival from early postoperative radioisotope studies.
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It has been routine at the University of Alabama Medical Center to obtain a radionuclide renal function study immediately after transplantation (usually within 3 d) that includes estimation of effective renal plasma flow (ERPF) from a single plasma sample in addition to imaging. We present here the correlation between baseline measurements and the 1-y graft survival. METHODS: Two cohort years were reviewed: 1988, when 131I-orthoiodohippurate (OIH) was used; and 1995, when 99mTc-mercaptoacetyltriglycine (MAG3) was used. ERPF was measured concurrently with gamma-camera imaging by previously published single-injection, single-sample methods (converting MAG3 clearance to ERPF by means of a correction factor). RESULTS: Graft survival during the first postoperative year improved significantly in the interval between cohort years, from 74% of 147 cadaver (CD) grafts in 1988 to 91% of 200 CD grafts in 1995 (log rank test, P < 0.05). In contrast, for living related donor (LRD) grafts there was no significant change, from 91% of 66 in 1988 to 91% of 83 in 1995. The baseline ERPF was a significant predictor of graft survival in both 1988 and 1995 (Wilcoxon test, P > 0.05). For LRD grafts the association was not significant in either year. Using MAG3 (1995), the peak time and the ratio of counting rate (R) at 20 min to that at 3 min (R20:3) were also significant predictors for CD graft survival. Using OIH (1988 cohort), the correlation with peak time did not reach significance, and the R20:3 measurement was not available. Although multivariate combinations (Cox proportional hazards model) did not have significantly more predictive value at the 95% confidence level than ERPF or R20:3 alone, some statisticians suggest a 75% confidence level for adding an additional covariate to a multivariate model. Use of this level led to a model including both ERPF and R20:3. CONCLUSION: Single-sample ERPF measured in the immediate post-transplant period, whether from OIH clearance or MAG3 clearance, was a statistical predictor of graft survival for CD transplants. For MAG3, the peak time and R20:3 were also significant predictors. These associations held only for CD transplants and not for LRD transplants. (+info)
Aspirin renography and captopril renography in the diagnosis of renal artery stenosis.
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Preliminary data suggest that aspirin renography is more sensitive than captopril renography for indicating renal artery stenosis (RAS). Considering that aspirin, compared with captopril, reduces renal blood flow and, thus, tubular tracer delivery in poststenotic kidneys, aspirin renography is expected to be more useful, particularly if tubular tracers are used. METHODS: We prospectively compared aspirin renography (20 mg/kg orally) and captopril renography (25 mg orally) with 99mTc-mercaptoacetyltriglycine in 75 consecutive patients suspected of having RAS. RESULTS: RAS, diagnosed as stenosis of more than 50% on angiography, was found unilaterally in 34 patients and bilaterally in 17 patients. RAS was absent in 24 patients. The sensitivities for unilateral RAS or bilateral RAS (i.e., stenosis that was at least unilateral) were, respectively, 88% and 88% for captopril renography and 82% and 94% for aspirin renography (not significant). The overall specificity was 75% for captopril renography and 83% for aspirin renography (not significant). Tracer uptake ratios, time to peak activity, and percentage of 20-min tracer retention were also not significantly different for captopril and aspirin renography. Subgroup analysis of modest (50-75%) and severe (> or =75%) RAS, or of plasma creatinine greater than 120 micromol/L, also showed no difference between captopril and aspirin renography. CONCLUSION: We conclude that for identification of RAS, the usefulness of aspirin renography equals, but does not surpass, that of captopril renography. (+info)
How gender and age affect iodine-131-OIH and technetium-99m-MAG3 clearance.
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OBJECTIVE: The relationship between age and effective renal plasma flow (ERPF) results, as measured in nuclear medicine, is well known. This paper explores the relationships among gender, age, and ERPF measurements. After reading this paper, the nuclear medicine technologist should be able to: (a) discuss the importance of establishing normal range values for ERPF that include age and gender variables; (b) state how age affects ERPF results; and (c) state how gender affects ERPF results. (+info)
Urinary extravasation and leakage after renal transplantation: a case report.
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OBJECTIVE: This case report illustrates urinary extravasation and leakage after renal transplantation, as documented by nuclear medicine renal imaging. The extravasation and leakage were identified only on images acquired after the patient voided. The surgical wound site dressings were found to contain radioactive contamination as well. (+info)