Contrast

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If you have this discussion with Siemens, one of the first things that they will tell you is that cone beam CT imaging requires diluted contrast. However, one thing that they perhaps are overlooking is that there is a large range of contrast concentrations being utilized as a matter of routine in neurendovascular labs. Visipaque, for example, is sold in the following concentrations: 270 and 320. In our lab, we have had success with Visipaque 270 for both planar angiography and cone beam CT acquisitions without the use of dilution. This is extremely helpful for workflow, where a dilution step is not required between planar and cone beam CT acquisition. We have not had issues with streak artifact nor resolving attenuation differences between contrast opacified vessel and lower attenuating braided tools. If using 300, 320 or higher concentrations we would recommend dilution to bring the concentration closer to 270. 

For labs utilizing 300 or 320 iodine concentration contrast in a 150 ml contrast injector but aiming to achieve performance of Visipaque 270, a simple dilution formula can approximate the desired concentration.

The goal is to dilute the contrast to a concentration of around 270 mgI/mL. To calculate the required dilution, use this formula:

Volume of contrast (mL)=Target concentration (270 mgI/mL)×Total volume (150 mL)Stock concentration (300 or 320 mgI/mL)Volume of contrast (mL)=Stock concentration (300 or 320 mgI/mL)Target concentration (270 mgI/mL)×Total volume (150 mL)​

• Target concentration: 270 mgI/mL
• Total volume: 150 mL

Volume of 300 mgI/mL contrast=270×150300=135 mLVolume of 300 mgI/mL contrast=300270×150​=135 mL

• Add 15 mL of saline to reach the total injector volume of 150 mL.

• Target concentration: 270 mgI/mL
• Total volume: 150 mL

Volume of 320 mgI/mL contrast=270×150320=126.56 mLVolume of 320 mgI/mL contrast=320270×150​=126.56 mL

• Add 23.44 mL of saline to reach the total injector volume of 150 mL.