title: Tc-99m mercaptoacetyltriglycine clearance: comparison of camera-assisted methods.
abstract: OBJECTIVE
  To compare the accuracy of three camera-assisted methods for the measurement of Tc-99m mercaptoacetyltriglycine (MAG3) clearance.
  
  
  METHODS
  MAG3 renal scintigraphy was performed in 21 adults with different degrees of renal function. Posterior views were obtained that included the heart and the kidneys in the camera field of view. The syringe for injection was imaged before and after injection. Blood samples were drawn 24 and 43 minutes after injection and plasma radioactivity was measured. Three camera-assisted techniques to measure MAG3 clearance were tested: 1) Biexponential fitting of the left ventricular curve, normalized to plasma activity at 24 minutes; 2) calculation of clearance by relating the integral of the plasma curve (normalized to plasma activity) to the kidney activity using the Rutland-Patlak space method; and 3) a regression equation measuring clearance from the percentage of the injected dose accumulating in the kidneys during the 1- to 2.5-minute period. The camera-assisted clearances were compared with the single-sample MAG3 clearances calculated using the Russell equation. Linear regression analysis was used to measure the correlation between the camera-based methods and the single-sample techniques.
  
  
  RESULTS
  Correlation with r > 0.900 was found for all three techniques. The difference in correlation coefficients between the three methods was not significant; however, the regression line of method 3 was significantly closer to the line of identity (P = 0.005).
  
  
  CONCLUSIONS
  Method 3 most closely fits the line of identity and is probably the most practical because no blood sample is needed.
authors.affiliation: Department of Medical Biophysics and Nuclear Medicine, Hadassah Hebrew University Hospital, Kiryat Hadassah, 91120 Jerusalem, Israel. moshe@hadassah.org.il
authors.forename: M
authors.initials: M
authors.lastname: Bocher
authors.forename: Y
authors.initials: Y
authors.lastname: Shrem
authors.forename: A
authors.initials: A
authors.lastname: Tappiser
authors.forename: M
authors.initials: M
authors.lastname: Klein
authors.forename: D
authors.initials: D
authors.lastname: Schechter
authors.forename: A
authors.initials: A
authors.lastname: Taylor
authors.forename: R
authors.initials: R
authors.lastname: Chisin
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D015902:Gamma Cameras; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging / Q000378:metabolism; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D017263:Technetium Tc 99m Mertiatide / Q000493:pharmacokinetics*; D016277:Ventricular Function, Left
chemical_list: D019275:Radiopharmaceuticals; D017263:Technetium Tc 99m Mertiatide