Radionuclides in nephrourology, part 1: Radiopharmaceuticals, quality control, and quantitative indices

Abstract

Radionuclide renal scintigraphy provides important functional data to assist in the diagnosis and management of patients with a variety of suspected genitourinary tract problems, but the procedures are underutilized. Maximizing the utility of the available studies (as well as the perception of utility by referring physicians) requires a clear understanding of the clinical question, attention to quality control, acquisition of the essential elements necessary to produce an informed interpretation, and production of a report that presents a coherent impression that specifically addresses the clinical question and is supported by data contained in the report. To help achieve these goals, part 1 of this review covers information that should be provided to the patient before the scan, describes the advantages and limitations of the available radiopharmaceuticals, discusses quality control elements needed to optimize the study, summarizes approaches to the measurements of renal function, and focuses on recommended quantitative indices and their diagnostic applications. Although the primary focus is the adult patient, aspects of the review also apply to the pediatric population.

Keywords: 99mTc-DTPA; 99mTc-MAG3; clearance; effective renal plasma flow; glomerular filtration rate; relative function; renal function; renal scintigraphy.

FIGURE 1

Images were obtained in patient with renal failure 30–45 min and 180–210 min after intravenous injection of ^99mTc-MAG3. Activity can be seen in gallbladder on both early and late images, and bowel activity is clearly visualized on delayed images. Bowel activity on delayed images should not be confused with urine leak.

FIGURE 2

(A and B) Two-minute kidney images after simultaneous injection of 95.8 MBq (2.59 mCi) of ^99mTc(CO)₃(NTA) (A) and 11.8 MBq (0.32 mCi) of ¹³¹I-OIH (B) in 74-y-old man with stage 3 chronic kidney disease. (C and D) Whole-kidney and cortical (parenchymal) renogram curves for ^99mTc(CO)₃(NTA) (C) and for ¹³¹I-OIH (D). Renogram curves for ¹³¹I-OIH are quite noisy because of relatively low counting rate resulting from lower administered dose, poor capture of 364-keV photon of ¹³¹I by 9.5-mm (3/8-in) crystal, and high-energy collimator not optimized for ¹³¹I. Difference in relative height of cortical curves in C and D is due to differences in size of relative cortical ROIs. It is shape of cortical renogram curve that is important, not absolute height.

FIGURE 3

Whole-kidney, cortical, and collecting system ROIs are illustrated on images from baseline and postfurosemide ^99mTc-MAG3 scans. (A) Whole-kidney ROI is illustrated on image obtained 2–3 min after injection. (B) Parenchymal (cortical) ROIs were assigned using 19- to 20-min image to ensure that parenchymal ROI excludes collecting system; assigning parenchymal ROI on 2- to 3-min image is problematic because collecting system is not visualized on this image. (C) Whole-kidney ROI was assigned using 1- to 2-min image after furosemide injection (2-stage diuretic acquisition protocol). (D) Collecting system ROI was assigned using 1- to 2-min image after furosemide injection. (Reprinted with permission of (50).)