Magnetic resonance angiography is a form of magnetic resonance imaging (MRI). MRI is a non-invasive method of taking images of the body. Electromagnetic radio waves create 2-dimensional or 3-dimensional images. The effects of magnetic resonance imaging, unlike computer tomography (CT scan) and X-rays, offer no risk to the humanbody. The principle of the MRI is not commonly known. It is in fact quite simple and unique.
The coils of the MRI machine create powerful electromagnetic fields. These electromagnetic fields cause hydrogen atoms inside the body to align themselves like the way the magnetic needle of a compass behaves when it is brought near to a magnetic field. The radio waves from the MRI machine impinge on these aligned hydrogen atoms causing them to bounce back. The computer records this movement in the form of a signal. The computer then interprets the signal and gives us information about the condition of that area of the body which is being scanned.
This is a special kind of magnetic resonance imaging where images of the vascular system (blood vessels, such as veins and arteries) are taken. This kind of test detects anomalies such as atherosclerosis, clots, and aneurisms and so on. The flow of blood can also be evaluated in this way.
The vascular system of the human body is a life-supporting network. If there are any aberrations in this, the body is adversely impacted. It can lead to illness and in more extreme cases, death. Therefore it is very important that the vascular system is kept healthy. Due to the location of the vascular system in the human body, it is not possible to detect a problem through external means. The only way to diagnose abnormalities in the vascular system is by studying the symptoms or by the use of sophisticated diagnostic equipment. Magnetic resonance angiography allows us to scan the entire vascular system the heart and all the associated blood vessels (veins and arteries).
The following parts of the body come under the purview of magnetic resonance angiography:
From what we have seen so far, it is obvious that an MRA is a more specialized form than an MRI. It should be however understood as to when an MRA needs to be done, rather than an MRI.
To highlight the difference between magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA), we can say that an MRI on the brain will show ventricles, tissue, internal auditory canals, ventricles, pituitary gland and sinus cavities. An MRA will show only the blood vessels in the brain. In the case of a neck MRI, the spinal canal will be shown in detail, including soft tissue, intervertebral disc spaces and thyroid gland. An MRA will show the carotid artery and associated blood vessels only.
An MRI creates images based on the difference in concentration of water in human tissues. It is mostly useful for detection of tumors and disorders of the nervous system, basically anomalies in the structure of the tissue. An MRA on the other hand is able to highlight irregularities in the blood vessels of the head and neck and is best for detecting aneurysms and blockages.
Therefore, it is seen that there is actually a very thin line between magnetic resonance angiography and magnetic resonance imaging. The equipment is more or less the same for both processes and the difference more or less the way in which the test is conducted. It can be then concluded that it is appropriate to conduct an MRA when the imaging needs to highlight the vascular system.