**7. Conclusion**

204 Coronary Interventions

Attenuation increases with the atomic number (Z) of the atom (iodine, Z = 53; gadolinium, Z = 64). At photon energies between the k-edge of iodine (33.2 keV) and that of gadolinium (50.2 keV), iodine attenuates roughly twice as many photons as does gadolinium (Nyman et al., 2002). At all other photon energies the opposite prevail. Thus, a gadolinium (Gd) CM may be used as an x-ray CM. Before the advent of nephrogenic systemic fibrosis (NSF) (Thomsen, 2009), some investigators reported on the use of Gd-CM in a variety of diagnostic angiographic and interventional procedures (Spinosa et al., 2002; Strunk & Schild, 2004) including PCA (Barcin et al., 2006; Briguori et al., 2006; Gupta & Uretsky, 2005; Sarkis et al., 2003; Voss et al., 2004) in patients at risk of CIN due to its perceived non-nephrotoxicity (Prince et al., 1996). However, the non-nephrotoxicity of Gd-CM has been proved wrong (Buhaescu & Izzedine, 2008; Ergun et al., 2006; Sam et al., 2003). In fact, Gd-CM may have a higher, both general and renal, toxicity than I-CM in concentrations and volumes causing the same attenuation as Gd-CM (Elmståhl et al., 2004; Elmståhl et al., 2008; Nyman et al.,

Moreover, the maximum dose of Gd-CM according to the manufacturers' recommendations is only 0.2-0.3 mmol/kg, though average doses used for x-ray angiographic procedures have ranged from 0.2-0.8 mmol/kg. However, average clinical I-CM doses of 40-100 grams of iodine, results in about 4-10 mmol/kg in a 75 kg individual. Thus, the use of Gd-CM is limited in terms of volume and radiodensity (Nyman et al., 2011). Despite this, diagnostic satisfactory PCA has been achieved with 1.0M Gd-CM (Briguori et al., 2006; Voss et al., 2004) or 2:1 (Barcin et al., 2006; Sarkis et al., 2003) and 1:1 mixtures (Gupta & Uretsky, 2005)

Angiographic experiments with a 30 cm thick water-equivalent phantom at 70 and 95 kVp indicate that iodine concentrations at 60 and 80 mg/mL, respectively, are iso-attenuating with 0.5M Gd-CM (Nyman et al., 2011). The attenuation of the 1.0M Gd-CM and the mixtures between 0.5M Gd-CM and I-CM at 320 or 350 mg I/mL would correspond to about 140-200 mg I/mL of a pure I-CM at 70-95 kVp, concentrations that are commercially available. Thus, it seems possible to perform coronary procedures with half or even one third of the standard concentrations, not at least in thinner patients patients in whom automatic or manual down-regulation of the x-ray tube potential will increase attenuation

Precautions and techniques to save contrast media during PCA/PCI in azotemic patients are

• Consider to use commercially available concentrations in the range of 140-200 mg I/mL,

• Avoid excessive "puffs" and scrutinize each series before the next one to avoid

• Substitute measurements with pressure wires of indeterminate stenotic lesions for

• If possible, delay examination, treat risk factors and institute hydration.

• Substitute echocardiography for left ventriculography.

**6.1 Iodine concentration iso-attenuating with gadolinium CM** 

2002).

by iodine.

summarized as follows:

• Use biplane technique if available.

especially in thinner patients.

multiple projections.

unnecessary standard projections.

of 0.5M Gd-CM and I-CM.

	- CT-angiography: 100-150 mg I/kg by using 80 kVp, mAs-compensation for constant CNR, fixed injection duration adapted to scan time, automatic bolus tracking and a saline chaser.
	- Coronary arteriography and interventions: 140-200 mg I/mL, especially in thinner patients in whom automatic or manual down-regulation of the x-ray tube potential will increase iodine attenuation.
