Purpose: 99mTc-tricarbonyl-nitrilotriacetic acid, [99mTc]Tc(CO)3(NTA), is a new 99mTc-renal radiopharmaceutical with a clearance equal to that of 131I-ortho-iodohippuran, [131I]I-OIH. Our purpose was to compare the performance of [99mTc]Tc(CO)3(NTA) and [99mTc]Tc-MAG3 in patients with suspected obstruction. Methods: [99mTc]Tc(CO)3(NTA) was prepared with commercially available NTA ligand and CRS Isolink kit, and isolated by HPLC. Eighteen adult patients referred for diuretic renography received an intravenous injection of approximately 40 mg of furosemide 15 min prior to either [99mTc]Tc(CO)3(NTA) or [99mTc]Tc-MAG3 (mean activity of 47 ± 4.4 MBq). Data were acquired for 24 min followed by an anterior image of the liver and gall bladder and a measure of voided volume. Patients received a second furosemide injection equal to one third of the original dose followed fifteen minutes later by administration of the alternate tracer, mean activity of 320 ± 34 MBq. Clearances were measured using a camera-based technique. Results: The clearance of NTA was greater than that of MAG3, 331 ± 146 versus 271 ± 105 mL/min/1.73 m2, respectively, p < 0.0001. The kidney to background ratio for NTA was greater than that of MAG3 for both left and right kidneys, p < 0.001; the 20 min/maximum count ratio was significantly less, p < 0.0001. There was no significant difference in the voiding volumes following NTA and MAG3 administration, 598 ± 237 mL versus 498 ± 170 mL, respectively, p = 0.07. Gall bladder activity was not observed with NTA but was present in 6/17 MAG3 studies. Images and renogram curves were comparable except for two patients where the NTA study excluded obstruction but the MAG3 study suggested an indeterminate or obstructed kidney. Conclusions: Unlike MAG3, NTA is not eliminated via the hepatobiliary track. Moreover, NTA has a higher kidney to background ratio and more rapid clearance than MAG3. These advantages should allow more robust camera-based clearance measurements and may lead to better discrimination between obstructed and non-obstructed kidneys.

Objective iRENEX is a software module that incorporates scintigraphic and clinical data to interpret 99mTc- mercaptoacetyltriglycine (MAG3) diuretic studies and provide reasons for their conclusions. Our objectives were to compare iRENEX interpretations with those of expert physicians, use iRENEX to evaluate resident performance and determine if iRENEX could improve the diagnostic accuracy of experienced residents. Methods Baseline and furosemide 99mTc-MAG3 acquisitions of 50 patients with suspected obstruction (mean age ± SD, 58.7 ± 15.8 years, 60% female) were randomly selected from an archived database and independently interpreted by iRENEX, three expert readers and four nuclear medicine residents with one full year of residency. All raters had access to scintigraphic data and a text file containing clinical information and scored each kidney on a scale from +1.0 to -1.0. Scores ≥0.20 represented obstruction with higher scores indicating greater confidence. Scores +0.19 to -0.19 were indeterminate; scores ≤-0.20 indicated no obstruction. Several months later, residents reinterpreted the studies with access to iRENEX. Receiver operating characteristic (ROC) analysis and concordance correlation coefficient (CCC) quantified agreement. Results The CCC among experts was higher than that among residents, 0.84, versus 0.39, respectively, P < 0.001. When residents reinterpreted the studies with iRENEX, their CCC improved from 0.39 to 0.73, P < 0.001. ROC analysis showed significant improvement in the ability of residents to distinguish between obstructed and non-obstructed kidneys using iRENEX (P = 0.036). Conclusion iRENEX interpretations were comparable to those of experts. iRENEX reduced interobserver variability among experienced residents and led to better agreement between resident and expert interpretations.

The purpose of the study was to compare diuresis renography scan interpretation generated by a renal expert system with the consensus interpretation of 3 expert readers.Methods The expert system was evaluated in 95 randomly selected furosemide-augmented patient studies (185 kidneys) obtained for suspected obstruction; there were 55 males and 40 females with a mean age ± SD of 58.6 ± 16.5 y. Each subject had a baseline 99mTc-mercaptoacetyltriglycine (99mTc-MAG3) scan followed by furosemide administration and a separate 20-min acquisition. Quantitative parameters were automatically extracted from baseline and furosemide acquisitions and forwarded to the expert system for analysis. Three experts, unaware of clinical information, independently graded each kidney as obstructed/probably obstructed, equivocal, and probably nonobstructed/nonobstructed; experts resolved differences by a consensus reading. These 3 expert categories were compared with the obstructed, equivocal, and nonobstructed interpretations provided by the expert system. Agreement was assessed using weighted κ, and the predictive accuracy of the expert system compared with expert readers was assessed by the area under receiver-operating-characteristic (ROC curve) curves. Results The expert system agreed with the consensus reading in 84% (101/120) of nonobstructed kidneys, in 92% (33/36) of obstructed kidneys, and in 45% (13/29) of equivocal kidneys. The weighted κ between the expert system and the consensus reading was 0.72 and was comparable with the weighted κ between experts. There was no significant difference in the areas under the ROC curves when the expert system was compared with each expert using the other 2 experts as the gold standard. Conclusion The renal expert system showed good agreement with the expert interpretation and could be a useful educational and decision support tool to assist physicians in the diagnosis of renal obstruction. To better mirror the clinical setting, algorithms to incorporate clinical data must be designed, implemented, and tested.

Our objective was to design and implement a clinical history database capable of linking to our database of quantitative results from 99mTc-mercaptoacetyltriglycine (MAG3) renal scans and export a data summary for physicians or our software decision support system. Methods For database development, we used a commercial program. Additional software was developed in Interactive Data Language. MAG3 studies were processed using an in-house enhancement of a commercial program. The relational database has 3 parts: a list of all renal scans (the RENAL database), a set of patients with quantitative processing results (the Q2 database), and a subset of patients from Q2 containing clinical data manually transcribed from the hospital information system (the CLINICAL database). To test interobserver variability, a second physician transcriber reviewed 50 randomly selected patients in the hospital information system and tabulated 2 clinical data items: hydronephrosis and presence of a current stent. The CLINICAL database was developed in stages and contains 342 fields comprising demographic information, clinical history, and findings from up to 11 radiologic procedures. A scripted algorithm is used to reliably match records present in both Q2 and CLINICAL. An Interactive Data Language program then combines data from the 2 databases into an XML (extensible markup language) file for use by the decision support system. A text file is constructed and saved for review by physicians. Results RENAL contains 2,222 records, Q2 contains 456 records, and CLINICAL contains 152 records. The interobserver variability testing found a 95% match between the 2 observers for presence or absence of ureteral stent (κ = 0.52), a 75% match for hydronephrosis based on narrative summaries of hospitalizations and clinical visits (κ = 0.41), and a 92% match for hydronephrosis based on the imaging report (κ = 0.84). Conclusion We have developed a relational database system to integrate the quantitative results of MAG3 image processing with clinical records obtained from the hospital information system. We also have developed a methodology for formatting clinical history for review by physicians and export to a decision support system. We identified several pitfalls, including the fact that important textual information extracted from the hospital information system by knowledgeable transcribers can show substantial interobserver variation, particularly when record retrieval is based on the narrative clinical records.

Kidney motion during dynamic renal scintigraphy can cause errors in calculated renal function parameters. Our goal was to develop and validate algorithms to detect and correct patient motion.Methods We retrospectively collected dynamic images from 86 clinical renal studies (42 females, 44 males), acquired using the following protocol for 99m Tc Mertiatide (MAG3) imaging: 80 128×128 image frames (24 2-second frames, 16 15-second frames, 40 30-second frames, 128×128, 3.2 mm/pixel). We simulated ten types of vertical motion in each patient study, resulting in 860 image sets. Motion consisted of up or down shifts of magnitude 0.25 pixels to 4 pixels per frame, and were either A) gradual shift additive over multiple frames or B) abrupt shift of one or more consecutive frames, with a later return to the start position. Additional horizontal motion was added to test its effect on detection of vertical motion. Original and shifted files were submitted to a motion detection algorithm. Corrective shifts were applied, and corrected and original, unshifted images were compared on a pixel by pixel basis. Motion detected in the shifted data was also tabulated before and after correcting for motion detected in the original unshifted data. A detected shift was considered correct if it was within 0.25 pixel of the simulated magnitude. Software was developed to facilitate visual review of all images, and to summarize kidney motion and motion correction using linograms. Results Overall detection of simulated shifts was 99% (3068/3096 frames) when the existing motion in the original images was first corrected. When the original motion was not corrected, overall shift detection was 76% (2345/3096 frames). For image frames in which no shift was added, (and original motion was not corrected) 87% (27142/31132 frames) were correctly detected as having no shift. When corrected images were compared to original, calculated count recovery was 100% for all shifts that were whole pixel magnitudes. For fractional pixel shifts, percent count recovery varied from 52–73%. Visual review suggested that some original, unshifted frames exhibited true patient motion. Conclusions The algorithm accurately detected motion as small as 0.25 pixels. Whole pixel motion can be detected and corrected with high accuracy. Fractional pixel motion can be detected and corrected but with less accuracy. Importantly, the algorithm accurately identified unshifted frames, which helps to prevent the introduction of errors during motion correction.

An image processing algorithm (AUTOROI) has been developed to totally automatically (or manually assisted) detect whole-kidney contours and generate renal regions of interest (ROI) for the extraction of the quantitative measurements used in the interpretation of Tc-99m-MAG3 renograms.Methods The 18-20th min dynamic frames post MAG3 injection were used to automatically define boxes surrounding each kidney which were then transposed to an early composite image for interpolative and directional background subtraction. Sobel operator and unsharp masking were applied for edge enhancement and resulting image histograms were equalized to better define poorly functioning kidneys. AUTOROI searched radially from the center of mass to define each kidney's ROI coordinates. AUTOROI was validated using MAG3 studies from 79 patients referred for suspected obstruction (79 L, 77 R kidneys) and 19 kidney donors with normal kidney function and no obstruction. Renal ROIs were manually defined by a nuclear medicine technologist with 20+ years of experience (reference standard) and an ABNM certified physician. AUTOROI and physician ROIs were automatically compared to the reference standard for determining border definition error. Results AUTOROI detected totally automatically the renal borders in 89% (172/194) of the kidneys from the entire group of 98 patients. The 22 kidneys missed automatically were subsequently detected by the assistance of a single manually placed fiducial point demarcating the liver/kidney boundary. These 22 kidneys were shown to be associated with markedly reduced MAG3 clearance. The mean error of AUTOROI for all 194 kidneys was 6.66 ± 3.77 mm and 7.31 ± 4.52 mm for the left and right kidneys respectively. The physician's error was 6.78 ± 2.42 mm and 6.65 ± 2.05 mm for the left and right kidneys respectively. This error difference between AUTOROI and the physician was not statistically significant. Conclusion AUTOROI provides an objective and promising approach to automated renal ROI detection.

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 CARTAN, 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.

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.

The International Scientific Committee of Radionuclides in Nephro-urology (ISCORN; http://www.iscorn.org) began in the late 1960s as an independent group of physicians and scientists working to facilitate radionuclide renal research and the practice of renal nuclear medicine. This group has subsequently issued a series of Consensus reports and has now developed a Guidance Document for quality assurance and structured reporting of diuresis renography in adults. ISCORN chose diuresis renography for its first Guidance Document for several reasons: suspected obstruction is the most common reason for referral, most radionuclide renal studies are conducted at institutions that perform fewer than 3 studies per week, and a large percentage of radionuclide renal studies are interpreted by physicians with limited training in nuclear medicine. An additional rationale was the observation that diuresis renography reports from ISCORN member institutions showed marked variation in the elements included in the reports as well as considerable variation in how the results were communicated to the referring physicians. Reports that omit the essential components of the procedure, that lack the necessary elements required for quality assurance and interpretation, that fail to indicate the rationale supporting the conclusions, and that fail, in some cases, to even clearly state the conclusions are a disservice to patients and reflect badly on nuclear medicine and radiology. To address these concerns, this Guidance Document was developed through an iterative series of comments and questionnaires regarding the reporting structure and importance of specific elements in the report. Panelists were asked to categorize each element as essential, recommended but not essential, local option (possibly useful but without sufficient data to support a higher ranking), and unnecessary (does not contribute to quality assurance or scan interpretation). Each element was independently scored by panelists without access to the individual scores of the other members or knowledge of the identity of panel members making specific comments. A majority vote was required to place an element in a specific category. The Guidance Document recommends a reporting structure organized into indications, clinical history, study procedure, findings and impression. The Guidance Document also specifies the elements considered essential or recommended in each of the reporting categories and provides a brief discussion of specific elements. Few elements, however, achieved unanimous agreement and the panel recognizes the need for innovation and the possibility of constraints imposed by local circumstances. Consequently, the Guidance Document is not intended to be restrictive but rather to provide a basic structure and rationale for diuresis renography reports in adults so that a report: (1) communicates the results to the referring physician in a clear and concise manner designed to optimize patient care; (2) contains the essential elements required to evaluate and interpret the study; (3)clearly documents the technical components of the study necessary for accountability, quality assurance and reimbursement; and (4) encourages clinical research by facilitating better comparison and extrapolation of results between institutions.

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.