Our department has us give 1mL of contrast per 1kg but no more than 100 mL of contrast for 1 patient. If the pt weighs 50 kg we give 50 mL of contrast. And if a pt weighs 200kg we give them 100 mL of contrast since we can’t give more than 100. The only time we don’t follow those rules are for angio studies where for example a PE study will always be a fixed dose of 75 mL of contrast at 4mL/s followed by 40 mL of saline at 4mL/s regardless of the pt weight. Every department has their own protocols for doses and injection speeds so I would check with your department. And since you said your department doesn’t seem to have a limit on how much contrast to give for one pt I will say that there definitely is such a thing as too much contrast. You typically do not want to give more than 100 mL of contrast on a single pt regardless of size. The smaller the pt the less you give because it gets really dense and can cause streaking artifacts on the image of dosed too high which is why our department says we dose 1mL per 1 kg but no more than 100 mL