MR renography: An algorithm for calculation and correction of cortical volume averaging in medullary renographs

We evaluated a mathematical algorithm for the generation of medullary signa l from raw dynamic magnetic resonance (MR) data. Five healthy volunteers we re studied. MR examination consisted of a run of 100 TI-weighted coronal sc ans (gradient echo: TR/TE 11/3.4 msec, flip angle 60 degrees; slice thickne ss 6 mm; temporal resolution 2 seconds). Gadolinium-diethylene triamine pen taacetic acid (DTPA; 0.05 mmol/kg) was Injected with an injector pump (5 ml /sec). Medullary MR renographs (MRRs) were calculated for regions of intere st with strong and moderate cortical volume averaging (CVA). A reference me dullary MRR, devoid of CVA, was obtained. Percentual signal differences bet ween calculated and reference medullary MRRs were estimated for each consec utive scan. Run averaged values of these differences were calculated. Mean values, after subtraction of the resting state signal, were +0.2% (SD 9.7%) and +0.7% (SD 9.0%) for areas with strong and moderate CVA, respectively. We conclude that with this algorithm reliable extraction of medullary MRRs is feasible, providing a unique tool for clinical evaluation of medullary d isease. (C) 2000 Wiley-Liss, Inc.