Iodine contrast iso-attenuating with diagnostic gadolinium doses in CTA and angiography results in ultra-low iodine doses. A way to avoid both CIN and NSF in azotemic patients?

Objectives To establish iodine (I) contrast medium (CM) doses iso-attenuating with gadolinium (Gd) CM doses regarded diagnostic in CTA and percutaneous catheter-angiography/vascular interventions (PCA/PVI) in azotemic patients. Methods CT Hounsfield units (HU) were measured in 20-mL syringes containing 0.01/0.02,/0.05/0.1 mmol/mL of iodine or gadolinium atoms and placed in phantoms. Relative contrast were measured in 20-mL syringes filled with iohexol at 35/50/70/90/110/140 mg I/mL and 0.5 M gadodiamide using radiofluoroscopy (RF), digital radiography (DX) and x-ray angiography (XA) systems. Clinical doses of Gd-CM at CTA/PCA/PVI were reviewed. Results At CT 91-116 and 104–125 mg I/mL in the chest and abdominal phantoms, respectively, were iso-attenuating with 0.5 M Gd at 80–140 kVp. At RF/DX/XA systems 35–90 mg I/mL were iso-attenuating with 0.5 M gadodiamide at 60–115 kVp. Clinically, 60 mL 91–125 mg I/mL (5.5–7.5 gram-iodine) at 80–140 kVp CTA and 60 mL of 35–90 mg I/mL (2.1–5.4 gram-iodine) at 60–115 kVp PCA/PVI would be iso-attenuating with 60 mL 0.5 M Gd-CM (=0.4 mmol Gd/kg in a 75-kg person). Conclusions Meticulous examination technique and judicious use of ultra-low I-CM doses iso-attenuating with diagnostic Gd-CM doses in CTA and PCA/PVI may minimise the risk of nephrotoxicity in azotemic patients, while there is no risk of NSF.