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Evaluation of Two Diuresis Renography Decision Support Systems to Determine the Need for Furosemide in Patients with Suspected Obstruction

Andrew Taylor1, Andrew N. Hill2, José N. E. Binongo2, Amita K. Manatunga2, Raghuveer Halkar1, Eva V. Dubovsky3 and Ernest V. Garcia1

1 Department of Radiology, Division of Nuclear Medicine, Emory University School of Medicine, 1364 Clifton St., Atlanta, GA 30322.
2 Department of Biostatistics, Emory University School of Public Health, Atlanta, GA.
3 Department of Radiology, Division of Nuclear Medicine, University of Alabama School of Medicine, Birmingham, AL.


Figure 1
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  		Fig. 1A —Knowledge library was generated for each parameter to convert any given parameter value into certainty factor. Graph shows parameter knowledge library to convert any time to half maximum count value for left kidney (whole-kidney region of interest [ROI]) to certainty factor value. Boundary values (see Subjects and Methods section for more detail) were 8, 11, 13, 15, and 20 minutes, respectively.

 

Figure 2
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  		Fig. 1B —Knowledge library was generated for each parameter to convert any given parameter value into certainty factor. Graph shows parameter knowledge library to convert any 20 minute to maximum count ratio for left kidney (cortical ROI) to certainty factor value. Boundary values were 0.17, 0.27, 0.32, 0.43, and 0.92, respectively.

 

Figure 3
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  		Fig. 2A —50-year-old woman referred for mercap-toacetyltriglycine (MAG3) scanning because of suspected obstruction QuantEM (developed at Emory University, licensed to GE Healthcare) review of baseline scan shows no infiltration. MAG3 clearance is reduced. Right kidney shows prompt uptake and excretion and is not obstructed. Left kidney shows reduction in relative function (18%). There was uniform uptake in left kidney with slow washout, but, importantly, there was no retention of tracer in collecting system. Clinically, study was interpreted as not obstructed and furosemide was not administered. RENEX, CARTAN, and experts agreed with this decision. Tmax = time to maximum counts, T1/2 = half-time, 20 min/max = 20-minute-to-maximum-count ratio, k = kilo.

 

Figure 4
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  		Fig. 2B —50-year-old woman referred for mercap-toacetyltriglycine (MAG3) scanning because of suspected obstruction Expanded QuantEM review display shows patient values for MAG3 clearance; residual urine volume; percent relative uptake; and time to maximum counts (Tmax), 20-minute-to-maximum-count ratio (20/max), half-time (T1/2), and postvoid to maximum (postvoid/max) ratios for whole-kidney and cortical regions of interest as well as normal ranges for each of these values. Expanded review page also shows enlarged parenchymal image obtained at 2-3 minutes, enlarged display of 19- to 20-minute image, and quality control images showing preinjection and postinjection syringe counts and time of bolus arrival in kidneys. Postvoid to maximum count ratio of left kidney is slightly elevated at 23%, but this ratio tells clinician that almost 80% of maximal activity has washed out of left kidney by conclusion of study. Such high washout percentage is strong evidence against obstruction.

 

Figure 5
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  		Fig. 3A —40-year-old man referred for mercaptoacetyl-triglycine (MAG3) scanning because of suspected obstruction. QuantEM (developed at Emory University, licensed to GE Healthcare) review of baseline scan shows no infiltration. Camera-based MAG3 clearance is normal. Left kidney shows rapid uptake and washout of tracer in sequential 2-minute images (center). Relative uptake of left kidney is 56%, whole-kidney half-time (T1/2) is 10.8 minutes, and postvoid to maximum count ratio (postvoid/max) is normal (B) excluding obstruction. Relative function of right kidney was 46%, and right kidney showed dilatation of renal pelvis, which can be appreciated on 2-minute image as well as on enlarged 2- to 3-minute image (B). T1/2 for whole-kidney region of interest (ROI) was prolonged at 20.3 minutes and 20-minute-to-maximum-count ratio (20/max) was elevated at 0.58. However, visually pelvis empties after voiding and postvoid/max was 0.20 (B). Although postvoid/max count ratio is slightly elevated (0.16 is the upper limit of normal [15]), experts' and clinical decisions were that furosemide was not indicated. CARTAN agreed with experts, but RENEX concluded that furosemide was needed to exclude obstruction of right kidney (see Discussion). Tmax = time to maximum count ratio, 20/max = 20-minute-to-maximum-count ratio, k = kilo.

 

Figure 6
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  		Fig. 3B —40-year-old man referred for mercaptoacetyl-triglycine (MAG3) scanning because of suspected obstruction. Expanded QuantEM review display shows patient values for MAG3 clearance; residual urine volume; percent relative uptake; and time to maximum (Tmax), 20-minute-to-maximum-count ratio (20/max), half-time (T1/2), and postvoid to maximum count (postvoid/max) ratios for whole-kidney and cortical ROIs as well as normal ranges for each of these values. Expanded review page also shows enlarged parenchymal image obtained at 2-3 minutes, enlarged display of 19- to 20-minute image, and quality control images showing preinjection and postinjection syringe counts and time of bolus arrival in kidneys. In particular, enlarged 2- to 3-minute image shows dilated renal pelvis, and postvoid/max ratio for right kidney is slightly elevated.

 

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