Which is better?
It is not possible to give a general answer to the question of which examination method is better than the other, as both MRI and CT have their clear advantages and disadvantages depending on the question. For example, it can be stated that the MRI works with radiation-free magnetic fields, whereas the CT works with radiation-emitting X-rays, so that the indication has to be determined precisely in order to decide which procedure is more suitable (e.g. avoiding harmful X-rays in CT in pregnant women). Furthermore, the preference for an examination procedure also depends on the question behind the imaging: MRI is particularly suitable for imaging soft tissue, CT is particularly suitable for imaging bony structures.
Depending on the problem, one or the other method is therefore the better choice. There is also an economic aspect that can play a role in the answer to the question “What is better? “: an MRI examination is usually much more expensive than a CT examination, so that costs can be saved if the desired structure can be displayed in both procedures.
The question of whether an MRI or CT is better for an examination of the head cannot be answered in general terms, but depends on the medical question.In the vast majority of cases, an MRI examination is more meaningful. Especially the brain can be assessed much better with this examination. For example, a stroke due to a circulatory disorder shows up much earlier in the MRI than in the CT. A stroke due to a cerebral haemorrhage, on the other hand, can be detected early using CT. Certain forms of cerebral hemorrhage can even be detected much better by CT than by MRI.
MRI is more suitable for assessing the remaining soft tissues of the head. However, CT is clearly superior to MRI in some aspects, so that CT examination is often the method of choice in many cases. While an MRI takes 15-20 minutes, a CT can be performed in just a few seconds.
This aspect is particularly important in emergency situations, so that a CT of the head is definitely preferable to an MRI after an accident, for example. This is also supported by the additional advantage that CT provides better images of bony structures than MRI. In order to detect or rule out injuries to the cranial and facial bones, for example after a traffic accident, a CT is better than an MRI.
For imaging examinations of the lungs, CT is preferable to MRI. Changes, lung tumors or metastases can usually be depicted well. Also in the case of pulmonary embolism (blockage of a pulmonary artery by a dissolved blood clot), vascular imaging of the lung using CT is the method of choice.
Only if there is an intolerance to contrast media can an MRI examination be used. However, it should be noted that a lung image (whether CT or MRI) requires a justified indication and should not be performed for every possible lung disease. In many cases, simpler examinations such as an X-ray or ultrasound are sufficient and in some cases even more meaningful.
Any abnormalities detected in the X-ray image can still be further clarified with a subsequent CT examination, if necessary. Whether an MRI or CT examination of the abdomen is better cannot be generally answered. Depending on the indication or question, one examination method may be superior to the other or both are considered equivalent.
CT is more suitable for a general examination, for example, to determine whether a tumor disease has already spread to other organs (staging examination). In contrast, MRI is preferable for the exact depiction of liver changes. MRI is also more precise in imaging the bile ducts and pancreas.
For a specific examination of changes or space requirements of the kidney, a CT is usually preferred. An exception is the imaging of the renal blood vessels. In this case, the MRI vessel imaging (MRI angiography) is the method of choice.
MRI is also the method of choice for examining organs in the pelvis, such as the bladder, prostate or rectum. Abdominal wall defects (hernias) can also be detected better by MRI than by CT. However, a good physical examination and, if necessary, an ultrasound are usually sufficient in this case and complex imaging such as MRI is not necessary.
Whether an examination of the cervical spine by means of CT or MRI should be carried out depends on the question posed. If there is a suspicion that a bony injury may be present, for example after a traffic accident, a CT examination should be performed. This is the best way to detect or rule out bone fractures.
For all other questions that require precise imaging of the cervical spine, MRI is to be preferred. Even if a herniated disc in this area of the spine is detected, an MRI should be performed immediately instead of a CT. Due to overlapping by the shoulders, the imaging of the intervertebral discs by CT is often difficult. As a matter of principle, imaging of the lumbar spine should only be performed under strict indication.
For example, if there is a reasonable suspicion that a herniated disc may be present, this can be confirmed or rejected by both an MRI and a CT. Which examination should be performed depends on the circumstances. A CT examination is usually more quickly accessible and feasible.
However, especially with younger patients, a CT should be avoided and an MRI preferred due to the radiation exposure. Patients who have already undergone surgery due to a herniated disc and who are again developing complaints should also be given preference for an MRI.The heart consists mainly of muscle tissue, which is why an MRI is in most cases much more suitable for imaging than a CT. It is even possible to generate three-dimensional images using MRI images of all levels.
This provides information about the size of the heart, the thickness of the heart walls and the structure of the heart valves, for example. Nevertheless, an MRI examination of the heart is only indicated in rare cases. Other examination methods, such as ultrasound, were available that were sufficient for the particular problem or even more informative than MRI.
Both MRI and CT are suitable for examining whether a patient has a herniated disc. Only in the area of the lower cervical spine is the MRI examination superior, since bone overlaps often make the CT more difficult to assess there. In principle, spinal imaging should only be performed if there is a well-founded suspicion of a structural disease such as a herniated disc.
Prior to this, the physician should conduct a detailed conversation and a physical examination. A serious herniated disc sometimes causes paralysis in addition to pain and discomfort in an arm or leg. In such a case, an early imaging by means of CT should be carried out, since this examination is faster to perform and easier to reach than an MRI.
If only back pain is present, imaging should not be performed at all, but movement and, if necessary, special exercises should be prescribed. However, there is also an indication where MRI is justified and is also better than CT. If a patient has had a herniated disc that has already been operated on and pain reoccurs in the course of the operation, MRI can differentiate whether the pain is caused by a new herniated disc or by scarring changes.
In most cases, a brain tumor can be detected by both MRI and CT. However, in the case of a soft organ such as the brain, MRI is superior in its imaging. The spread and limitation of the tumor can often be shown well by this examination, which is particularly important for planning the therapy (surgery or radiation).
In most cases, the MRI examination is performed with a simultaneous administration of a contrast medium via a vein access on the arm. Based on the accumulation behavior of the brain tumor, further important findings for diagnosis and therapy can be obtained. If a patient is suspected of having a brain haemorrhage, the fastest possible imaging is necessary.
CT is to be preferred to MRI for several reasons. Firstly, the CT examination only takes a few seconds to minutes, whereas an MRI takes considerably longer and would thus delay any necessary therapy. On the other hand, fresh cerebral hemorrhages can be detected much better by CT than by MRI.
Even small bleedings can be detected by the doctor in charge in the CT and often the source of the bleeding can be identified immediately. In the case of headaches, imaging by MRI or CT should not normally be performed immediately. In most cases, a diagnosis of the cause of the headache can be made using other methods.
These include first and foremost a medical consultation. Depending on the type of headache, accompanying symptoms or triggers, the type can often already differentiate what the possible cause is and recommend a therapy. Only if the doctor suspects that a brain disease is responsible for the headache, for example due to other symptoms such as sensation in the arms or legs, can an MRI examination be considered.
An exception is made for suddenly occurring extremely severe headaches that have never been felt like this before. This is also called a destructive headache. This can be a sign of bleeding in the brain, which is best detected or ruled out by a CT scan as soon as possible.
