Subtraction of extra‐renal background in ^99mTc‐DTPA renography: comparison of various regions of interest

Abstract

Quantitative evaluation of renal function in 99mTc-DTPA isotope renography is hampered by high background activity. This study compares various background regions of interest (ROIs) to obtain the most accurate estimate of the extra-renal background, taking both total counts (integral value) and change by time (slope) into account. Gamma camera renography was performed in 21 patients with a single kidney. Time-activity histograms obtained from 8 different background ROIs were compared in the time interval corresponding to the uptake phase of the renogram with the histogram obtained from a ROI over the empty kidney area. A significant difference could be demonstrated between the slope values of the histograms of the right and left empty kidney ROIs, but not for the integral values. Backgrounds taken over the heart, liver, between the kidneys, and under the kidneys had significantly different characteristics than the one in the empty kidney area. Only background ROIs surrounding each kidney area gave integral and slope values with close resemblance to those recorded over the empty kidney area. The results emphasize the necessity for an individual background ROI for each kidney and the need to separate extra- and intra-renal background activities before subtraction.

Reproducibility of 99mTc-mercaptoacetyltriglycine renography: population comparison

“…A unified method of DRF calculation and background ROI type and placement was, in our case, achieved by using the same processing software, which the observers were used to. An integral method was used for DRF calculation and perirenal ROI [21][22][23] was used for background subtraction; both methods were validated with respect to reproducibility [13] and are recommended by guidelines [1][2][3][4]. As both methods are routinely used at our institution and our goal was to assess reproducibility of our routine work, alternative methods of background subtraction and DRF calculation were not used in the analysis.…”

EFFECT OF REGION OF INTEREST SELECTION AND UPTAKE MEASUREMENT ON GLOMERULAR FILTRATION RATE MEASURED BY99mTc‐DTPA SCINTIGRAPHY IN DOGS

“…To correct for this directly requires a heart ROI plasma curve, of standard size and consistent placement, in itself a source of error. 'y, 20,26 The regression equation used to predict GFR may be different in each laboratory. ' A 99"Tc-DTPA labeling efficiency may vary from one laboratory to the other.…”

Effect of Observer Variability on Glomerular Filtration Rate Measurement by Renal Scintigraphy in Dogs

“…Manually drawing the background ROI is common, with many methods of placing the ROI. A circumferential background ROI has been found to be the most reliable, 8,24 and in normal dogs its position and width caused considerable differences in percent uptake and accuracy 7 . Manual background ROI drawing is likely to introduce more variation.…”

“…Overcorrection or undercorrection of background activity will cause errors in the calculated percentage uptake of DTPA. Many different regions have been used in humans to represent background activity, 8,12,13 the perirenal being one of the most accurate 8 . With the 64 × 64 matrix size of the dynamic study, we found in normal dogs that a perirenal background ROI at one pixel out from the kidney ROI gave the best correlation between percentage uptake and GFR by plasma clearance, with both manual ROI and semi‐automatic ROI 7 …”

“…In dogs, uptake of DTPA is corrected for background activity and kidney depth 4–6 . Many factors are sources of variability: selection of the uptake part of the time activity curve (TAC) which includes the earliest filtration part of the curve after the vascular phase and fulfills the physiologic requirement that no activity has left the kidney, 7 drawing of kidney and background region of interest (ROI), and kidney depth measurement for correction of soft tissue attenuation 6,8,9 …”