99mTc-MAG3: Image Wisely

Abstract

Purpose To determine if commonly administered doses of technetium 99m (^99mTc) mertiatide (MAG₃) in the range of 300-370 MBq (approximately 8-10 mCi) contribute to image interpretation and justify the resulting radiation exposure. Materials and Methods The respective institutional review boards approved this HIPAA-compliant study and waived informed consent. Baseline and furosemide ^99mTc-MAG₃ imaging examinations in 50 patients suspected of having renal obstruction and 48 patients suspected of having renovascular hypertension (RVH) were randomly selected from archived databases and were independently scored by three experienced readers without access to 2-second flow images. Readers were blinded to their original scores, and then they rescored each examination with access to high-activity 2-second flow images. Relative renal function was determined after a low activity (62.9 MBq ± 40.7) baseline acquisition for RVH and a high activity (303.4 MBq ± 48.1) acquisition after administration of enalaprilat. Data were analyzed by using random effects analysis of variance and mean and standard error of the mean for the difference between sets of scores and the difference between relative function measurements. Results There was no significant difference in the scores without flow images compared with blinded scores with high-activity flow images for patients suspected of having obstruction (P = .80) or RVH (P = .24). Moreover, there was no significant difference in the relative uptake measurements after administration of low and high activities (P > .99). Conclusion Administered doses of ^99mTc-MAG₃ in the range of 300-370 MBq (approximately 8-10 mCi) do not affect the relative function measurements or contribute to interpretation of images in patients suspected of having RVH or obstruction compared with administration of lower doses; unnecessary radiation exposure can be avoided by administering doses in the range of 37-185 MBq as recommended incurrent guidelines. ^© RSNA, 2017.

Figure 1a:

Planar ^99mTc-MAG₃ images of the kidneys in an 84-year-old man with hypertension, mild bilateral renal artery stenosis, diabetes with proteinuria level of 3 or more, and a serum creatinine level of 2.8 mg/dL. (a) Sequential 2-minute images after administration of low-dose (43.3 MBq,1.17 mCi) ^99mTc-MAG₃. (b) Sequential 2-minute images after administration of high-dose (203.5 MBq, 5.5 mCi) ^99mTc-MAG₃.

Figure 1b:

Planar ^99mTc-MAG₃ images of the kidneys in an 84-year-old man with hypertension, mild bilateral renal artery stenosis, diabetes with proteinuria level of 3 or more, and a serum creatinine level of 2.8 mg/dL. (a) Sequential 2-minute images after administration of low-dose (43.3 MBq,1.17 mCi) ^99mTc-MAG₃. (b) Sequential 2-minute images after administration of high-dose (203.5 MBq, 5.5 mCi) ^99mTc-MAG₃.

Figure 2a:

Planar ^99mTc-MAG₃ images of the kidneys in a 52-year-old woman suspected of having RVH and serum creatinine level of 0.7 mg/dL. (a) Sequential 2-minute images after administration of low-dose (74 MBq, 2.0 mCi) ^99mTc-MAG₃. (b) Sequential 2-minute images after administration of high-dose (370MBq, 10.0 mCi ) ^99mTc-MAG₃.

Figure 2b:

Planar ^99mTc-MAG₃ images of the kidneys in a 52-year-old woman suspected of having RVH and serum creatinine level of 0.7 mg/dL. (a) Sequential 2-minute images after administration of low-dose (74 MBq, 2.0 mCi) ^99mTc-MAG₃. (b) Sequential 2-minute images after administration of high-dose (370MBq, 10.0 mCi ) ^99mTc-MAG₃.

Figure 3a:

Planar ^99mTc-MAG₃ images of the kidneys in a 76-year-old man with hypertension, chronic renal failure, creatinine level of 1.3 mg/dL, and history of prostate cancer with pelvic radiation. (a) Sequential 2-minute images after administration of low-dose (40.7 MBq 1.1 mCi) ^99mTc-MAG₃. (b) Sequential 2-minute images after administration of high-dose (347.8 MBq, 9.4 mCi) ^99mTc-MAG₃.

Figure 3b:

Planar ^99mTc-MAG₃ images of the kidneys in a 76-year-old man with hypertension, chronic renal failure, creatinine level of 1.3 mg/dL, and history of prostate cancer with pelvic radiation. (a) Sequential 2-minute images after administration of low-dose (40.7 MBq 1.1 mCi) ^99mTc-MAG₃. (b) Sequential 2-minute images after administration of high-dose (347.8 MBq, 9.4 mCi) ^99mTc-MAG₃.

Figure 4:

Sequential 2-second planar flow images of the intial ^99mTc-MAG₃ bolus (373.7 MBq [10.1 mCi]) as it transits abdominal aorta and kidneys in 44-year-old man with creatinine level of 1.05 mg/dL and moderate left hydronephrosis.

Figure 5:

Scatterplot shows relative uptake of left kidney after low-dose (62.9 MBq ± 40.7) acquisition and high-dose (303.4 ± 48.1 MBq) acquisition after administration of enalaprilat. Mean slope of regression line ± standard error of the mean for respective relative uptake values was 1.02 ± 0.04, not significantly different from unity (P = .65). Correlation coefficient was 0.96 and mean intercept ± standard error of the mean was −0.23 ± 2.29, not significantly different from zero (P = .92). CI = confidence interval.