Effects of radiofrequency ablation on individual renal function: assessment by technetium-99m mercaptoacetyltriglycine renal scintigraphy.
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We quantitatively evaluated total and individual renal function by technetium-99m mercaptoacetyltriglycine (Tc-99m MAG3) renal scintigraphy before and after radiofrequency ablation (RFA) of renal tumors. Eleven patients who underwent Tc-99m MAG3 renal scintigraphy 1 week before and after RFA were evaluated (7 men and 4 women; age range: 23-83 years; mean age: 60.6 years). Five patients had solitary kidneys, and five had normally or minimally functioning contralateral kidneys. One patient had a renal cell carcinoma in the contralateral kidney. One patient with a solitary kidney underwent RFA a second time for a residual tumor. In patients with a solitary kidney, MAG3 clearance decreased after 5 of 6 RFAs, and in patients with a normally functioning contralateral kidney, MAG3 clearance decreased after 4 of 5 RFAs, but no significant differences were observed between before and after treatments. In addition to the total MAG3 clearance, the split MAG3 clearance was evaluated in patients with a normally functioning contralateral kidney. MAG3 clearance decreased in 4 of 5 treated kidneys, while it adversely increased in the contralateral kidneys after 4 of 5 RFAs. No significant differences, however, were observed between before and after treatments. The results of our study revealed no significant differences in sCr, BUN, CCr, or MAG3 clearance between pre- and post-RFA values. These results support data regarding the functional impact and safety of renal RFA in published reports. We evaluated total and individual renal function quantitatively using Tc-99m MAG3 renal scintigraphy before and after treatment. This scintigraphy was very useful in assessing the effects of RFA on renal function. (+info)
Simplified method for determining the radiochemical purity of 99mTc-MAG3.
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99mTc-Mercaptoacetyltriglycine is used for dynamic renal imaging, and the summary of product characteristics (SPC) for the European formulation specifies a shelf life of 1 or 4 h, depending on the reconstitution volume of the kit. To minimize the time required to test the radiochemical purity, a simplified quality control method was developed. METHODS: To satisfy the recommendations of the International Commission on Harmonisation, results obtained with the methods described in the European and American SPCs were compared with those obtained with the simplified method. Further validation of the new method was performed by comparison with the standard 2-strip thin-layer chromatographic method as well as tests for linearity and limits of detection and quantification. RESULTS: The simplified method provided results comparable to those provided by the registered SPC methods but was more rapid to perform and used smaller volumes of solvents. CONCLUSION: The simplified method is a reasonable alternative to the registered SPC methods. (+info)
Can renal doppler sonography replace diuretic radionuclide renography in infants with hydronephrosis?
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Reliable differentiation between obstructive and non-obstructive hydronephrosis is decisive for the further therapeutic management in infants. The results of renal Doppler sonography were compared with diuretic radionuclide renography and with the follow-up results in 33 patients (range: 21 to 98 days). In Doppler sonography, a resistive index (RI) of > 0.9 was considered to be abnormal in the sense of an obstruction. In diuretic renography, a T1/2 value (time until a 50% decrease in activity in the kidneys was observed after injection of furosemide) of >20 min was appraised as obstructive hydronephrosis. In six patients an obstructive (T1/2 >20 min) and in 27 patients a non-obstructive (T1/2 <20 min) hydronephrosis was found. All patients with obstruction in diuretic renography showed an abnormal RI (>0.9) in Doppler sonography. In addition, all patients with surgery and obstruction in diuretic radionuclide renography showed an improvement in hydronephrosis. However, seven patients had a false-positive result in Doppler sonography. All patients with non-obstruction in diuretic radionuclide renography showed no worsening of hydronephrosis without surgery in the follow-up. We found a RI of 0.84 +/- 0.07 in the non-obstructive group and of 0.96 +/- 0.05 (p = 0.018) in the obstructive group. Doppler sonography showed discrepant results compared to diuretic radionuclide renography and therefore cannot replace this method. (+info)
Use of classification and regression trees in diuresis renography.
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RATIONALE AND OBJECTIVES: Decision support systems have the capacity to improve diagnostic performance and reduce physician errors. The purpose of this study was to evaluate the use of classification and regression trees (CART) with bootstrap aggregation as a decision support system in the baseline plus furosemide (F + 20) diuresis renography protocol to determine when obstruction can be excluded without the furosemide acquisition and to identify the key parameters for making this determination. MATERIALS AND METHODS: Patients with suspected ureteral obstruction were randomly assigned to a training set (80 patients, 157 kidneys) and a validation set (64 patients, 124 kidneys). Forty quantitative parameters (curve parameters, MAG3 clearance and voiding indices) were generated from each baseline Tc-99m mercaptoacetyltriglycine (MAG3) scan. Three expert readers independently evaluated each kidney regarding the need for furosemide and resolved differences by majority vote. CART with bootstrap aggregation was applied to the training set to generate prediction algorithms which were tested in the validation set. RESULTS: The algorithm agreed with the expert decision on the necessity of furosemide in 90% (111 of 124 kidneys), with misclassification rates of 10.0% and 10.9% for the left and right kidneys, respectively. The most important discriminators were the postvoid-to-maximum count ratio, the cortical 20-minute-to-maximum count ratio, and the postvoid-to-1-to-2-minute count ratio. CONCLUSION: CART can identify the key parameters for discriminating between nonobstruction and possible obstruction, has the potential to serve as a decision support tool to avoid unnecessary furosemide imaging, and can be applied to more complex imaging problems. (+info)
A software engine to justify the conclusions of an expert system for detecting renal obstruction on 99mTc-MAG3 scans.
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The purposes of this study were to describe and evaluate a software engine to justify the conclusions reached by a renal expert system (RENEX) for assessing patients with suspected renal obstruction and to obtain from this evaluation new knowledge that can be incorporated into RENEX to attempt to improve diagnostic performance. METHODS: RENEX consists of 60 heuristic rules extracted from the rules used by a domain expert to generate the knowledge base and a forward-chaining inference engine to determine obstruction. The justification engine keeps track of the sequence of the rules that are instantiated to reach a conclusion. The interpreter can then request justification by clicking on the specific conclusion. The justification process then reports the English translation of all concatenated rules instantiated to reach that conclusion. The justification engine was evaluated with a prospective group of 60 patients (117 kidneys). After reviewing the standard renal mercaptoacetyltriglycine (MAG3) scans obtained before and after the administration of furosemide, a masked expert determined whether each kidney was obstructed, whether the results were equivocal, or whether the kidney was not obstructed and identified and ranked the main variables associated with each interpretation. Two parameters were then tabulated: the frequency with which the main variables associated with obstruction by the expert were also justified by RENEX and the frequency with which the justification rules provided by RENEX were deemed to be correct by the expert. Only when RENEX and the domain expert agreed on the diagnosis (87 kidneys) were the results used to test the justification. RESULTS: RENEX agreed with 91% (184/203) of the rules supplied by the expert for justifying the diagnosis. RENEX provided 103 additional rules justifying the diagnosis; the expert agreed that 102 (99%) were correct, although the rules were considered to be of secondary importance. CONCLUSION: We have described and evaluated a software engine to justify the conclusions of RENEX for detecting renal obstruction with MAG3 renal scans obtained before and after the administration of furosemide. This tool is expected to increase physician confidence in the interpretations provided by RENEX and to assist physicians and trainees in gaining a higher level of expertise. (+info)
Development and prospective evaluation of an automated software system for quality control of quantitative 99mTc-MAG3 renal studies.
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Quantitative nuclear renography has numerous potential sources of error. We previously reported the initial development of a computer software module for comprehensively addressing the issue of quality control (QC) in the analysis of radionuclide renal images. The objective of this study was to prospectively test the QC software. METHODS: The QC software works in conjunction with standard quantitative renal image analysis using a renal quantification program. The software saves a text file that summarizes QC findings as possible errors in user-entered values, calculated values that may be unreliable because of the patient's clinical condition, and problems relating to acquisition or processing. To test the QC software, a technologist not involved in software development processed 83 consecutive nontransplant clinical studies. The QC findings of the software were then tabulated. QC events were defined as technical (study descriptors that were out of range or were entered and then changed, unusually sized or positioned regions of interest, or missing frames in the dynamic image set) or clinical (calculated functional values judged to be erroneous or unreliable). RESULTS: Technical QC events were identified in 36 (43%) of 83 studies. Clinical QC events were identified in 37 (45%) of 83 studies. Specific QC events included starting the camera after the bolus had reached the kidney, dose infiltration, oversubtraction of background activity, and missing frames in the dynamic image set. CONCLUSION: QC software has been developed to automatically verify user input, monitor calculation of renal functional parameters, summarize QC findings, and flag potentially unreliable values for the nuclear medicine physician. Incorporation of automated QC features into commercial or local renal software can reduce errors and improve technologist performance and should improve the efficiency and accuracy of image interpretation. (+info)
Monitoring renal function: a prospective study comparing camera-based technetium-99m mercaptoacetyltriglycine clearance and creatinine clearance.
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OBJECTIVES: To determine the value and limitations of technetium-99m mercaptoacetyltriglycine (MAG3) clearance measurements obtained using a gamma camera (camera-based MAG3 clearance), a prospective study was conducted to evaluate the reproducibility of camera-based MAG3 clearance compared with that of conventional creatinine clearance. METHODS: A total of 24 male patients with stable renal function were entered into the study. The mean age was 66.5 +/- 7.9 years, and the mean serum creatinine was 1.38 +/- 0.57 mg/dL. MAG3 renal scans and 24-hour creatinine clearance measurements were performed 11 +/- 8 days apart. A camera-based MAG3 clearance was obtained at each MAG3 scan; no blood samples were required. Bland-Altman plots were constructed to assist in data analysis. RESULTS: The Pearson correlation for the first and second camera-based MAG3 clearances (mean 151 versus 158 mL/min/1.73 m2, respectively) was 0.965 compared with 0.729 for the two creatinine clearance measurements (mean 62 versus 72 mL/min/1.73 m2, respectively). Even with the omission of two outliers, the creatinine clearance would have to change by 58.2% compared with the baseline measurement before the clinician could be confident the change exceeded the error of measurement. In contrast, the change required for the camera-based MAG3 clearance was 30.8%. CONCLUSIONS: The results of this study have demonstrated that MAG3 clearance obtained using a camera-based technique shows greater precision than the conventional creatinine clearance and is superior to the conventional creatinine clearance for monitoring changes in renal function. (+info)
Evaluation of two diuresis renography decision support systems to determine the need for furosemide in patients with suspected obstruction.
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OBJECTIVE: The purpose of this study was to compare the decisions regarding the need for furosemide made by two independent renal decision support systems, RENEX and CAR-TAN, with the need for furosemide determined in clinical practice and by expert reviewers using the baseline plus furosemide protocol. SUBJECTS AND METHODS: RENEX and CARTAN are independent decision support systems that reach their conclusions without operator input. RENEX is a knowledge-based system and CARTAN is a statistical decision support system. Both were trained using the same pilot group of 31 adult patients (61 kidneys) referred for suspected obstruction. Subsequently, both systems were prospectively applied to 102 patients (200 kidneys) of whom 70 received furosemide; decisions regarding the need for furosemide were compared with the clinical decisions and the decisions of three experts who independently scored each kidney on the need for furosemide. Differences were resolved by consensus. RESULTS: RENEX agreed with the clinical and experts' decisions to give furosemide in 97% (68/70) and 98% (65/66) of patients, respectively, whereas CARTAN agreed in 90% (63/70) and 89% (59/66), respectively, p < 0.03. In contrast, CARTAN agreed with the experts' decision to withhold furosemide in 78% of kidneys (87/111), whereas RENEX agreed in only 69% of kidneys (77/111), p = 0.008. CONCLUSION: Use of RENEX or CARTAN as decision support tools in the baseline plus furosemide protocol has the potential to help the radiologist avoid unnecessary imaging and reduce the technologist, computer, camera, and physician time required to perform the procedure. (+info)