Medical imaging
Because CT and MRI are sensitive to different tissue properties, the appearances of the images obtained with the two techniques differ markedly. In CT, X-rays must be blocked by some form of dense tissue to create an image, so the image quality when looking at soft tissues will be poor. In MRI, while any nucleus with a net nuclear spin can be used, the proton of the hydrogen atom remains the most widely used, especially in the clinical setting, because it is so ubiquitous and returns a large signal. This nucleus, present in water molecules, allows the excellent soft-tissue contrast achievable with MRI.
Aortic dissection
The disadvantage of the MRI scan in the face of aortic dissection is that it may be available only in larger hospitals, and the scan is relatively time-consuming, which could be dangerous in people who are already very unwell. Due to the high-intensity magnetic fields used during MRI, it cannot be used on individuals with metallic implants. In addition, some individuals experience claustrophobia while surrounded by the MRI magnet.