The brain is hidden from direct view by the skull, which not only shields it from injury but also hinders the study of its function in both health and disease. The complexity of the organ that determines how a person thinks, moves, feels, and remembers is overshadowed only by its unique vulnerability. MRI allows the evaluation of structures that may be obscured by artifacts from bone in CT images.MRI contrast agents have a considerably smaller risk of causing potentially lethal allergic reaction.
MRI has a much greater range of available soft tissue contrast, depicts anatomy in greater detail, and is more sensitive and specific for abnormalities within the brain itself.MRI does not use ionizing radiation, and is thus preferred over CT in children and patients requiring multiple imaging examinations.CT can be performed at no risk to the patient with implantable medical devices, such as cardiac pacemakers, ferromagnetic vascular clips, and nerve stimulators.CT allows accurate detection of calcification and metal foreign bodies.CT provides detailed evaluation of cortical bone.CT may be easier to perform in claustrophobic or very heavy patients.because the imaging can be performed much more rapidly CT is less sensitive to patient motion during the examination.CT can be obtained at considerably less cost than MRI, and is sufficient to exclude many neurological disorders.CT is much faster than MRI, making it the study of choice in cases of trauma and other acute neurological emergencies.The advantages of each modality listed below serve as general guidelines that doctors use to decide between head CT and MRI: Advantages of Head CT The utility of “screening” CT or MRI, in which a scan is obtained in a healthy patient without any symptoms to look for a brain tumor or any other condition, has not been established. Both techniques are designed to examine specific problems. All imaging studies that are not performed for research should be obtained in close consultation with a physician.
The choice of which examination is appropriate depends upon how quickly it is necessary to obtain the scan, what part of the head is being examined, and the age of the patient, among other considerations. CT and MRI are complementary techniques, each with its own strengths and weaknesses. The answer to which imaging modality is better for imaging the brain is dependent on the purpose of the examination.
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