Measurement of single kidney contrast media clearance by multiphasic spiral computed tomography: preliminary results

Objective. We present preliminary results of a new method (hereinafter call ed 'CT-clearance') to measure single kidney contrast media clearance by per forming multiphasic helical CT of the kidneys. CT-clearance was calculated according to an extension of the Patlak-Plot. In contrast to prior investig ators, who repeatedly measured a single slice, this method makes it possibl e to calculate single kidney clearance from at least three spiral CTs, util izing the whole kidney volume. Methods. Spiral CT of the kidneys was perfor med unenhanced and about 30 and 100 s after administration of about 120 ml iopromide. Sum-density of the whole kidneys and aortic density was calculat ed from this data. Using this data, renal clearance of contrast media was c alculated by CT-clearance in 29 patients. As reference, Serum-clearance was calculated in 24 patients by application of a modified one-exponential slo pe model. Information on the relative kidney function was gained by renal s cintigraphy with Tc99m-MAG-3 or Tc99m-DMSA in 29 patients. Results. Linear regression analysis revealed a correlation coefficient of CT-clearance with Serum-clearance of r = 0.78 with Cl (CT) [ml/min] = 22.2 + 1.03 * Cl (seru m), n = 24. Linear regression of the relative kidney function (rkf) of the right kidney calculated by CT-clearance compared to scintigraphy results pr ovided a correlation coefficient r = 0.89 with rkf(CT)[%] = 18.6 + 0.58 * r kf(scintigraphy), n = 29. Conclusion. The obtained results of contrast medi a clearance measured by CT-clearance are in the physiological range of the parameter. Future studies should be performed to improve the methodology wi th the aim of higher accuracy. More specifically, better determination of t he aortic density curve might improve the accuracy. (C) 2001 Elsevier Scien ce Ireland Ltd. All rights reserved.