Measurement of effective renal plasma flow (ERPF) with 123I-orthoiodohippurate (I-123-OIH).

We evaluated the necessity of attenuation correction for calculating effective renal plasma flow (ERPF) using I-123-orthoiodohippurate (OIH), an agent introduced recently to replace I-131-OIH. From a kidney phantom experiment, the attenuation coefficient (mu) for I-123-OIH in the human body was determined as 0.1262 cm-1. I-123-OIH renal scintigraphy was performed in 23 patients with urinary diseases with blood sampling for calculation of ERPF by Tauxe's method. Calculated renal uptake, with or without attenuation correction, was compared with ERPF determined by Tauxe's method. There was good correlation between renal uptake without attenuation correction and ERPF obtained by Tauxe's method (r = 0.737), while much better correlation was found between attenuation-corrected renal uptake and ERPF calculated by Tauxe's method (r = 0.816). In conclusion, attenuation correction for renal uptake is an important technique for estimating ERPF using I-123-OIH renal scintigraphy.