MRI Of The Head
Magnetic Resonance Imaging – better known as MRI – of the head is the head imaging technique that makes use of the radio-frequency waves, powerful magnetic fields, and advanced computer image processing to produce a detailed image of the brain and the cranial structures. With the aid of a contrast material, usually, gadolinium, MRI is capable of producing better images bearing more details than any other imaging method in use today. Additionally, the sharpness of the images is achieved without the use of ionizing radiation, which improves the safety of the procedure considerably.
However, despite being inherently safer than other imaging techniques in use today, patients looking to undergo MRI scanning of their heads should divulge any and every relevant medical information that may affect the procedure or their health.as such, patients should provide their doctors with information about recent surgeries, any prevailing health issues, as well as any allergies they may have.
The magnetic fields in use are quite harmless. However, they may affect the efficiency and functionality of some medical implants. With this in mind, even though the vast majority of orthopedic implants may not be affected, patients are best advised to divulge information regarding their presence.
Another benefit of using MRI is that even though the imaging technique is quite robust and developed, it does not necessarily need patients to change their routines. For instance, typically, patients do not have to change their diets or medications prior to having an MRI. Thus unless specifically given instructions by your doctor regarding eating, drinking, and taking medicine, one does not have to change anything. This bodes well with regular living as patients do not have to change their daily routines. The only thing they are asked to do is to wear loose fitting, comfortable clothes that are devoid of any metal as well avoid taking any jewelry to the MRI scanning session.
Understanding MRI Of The Head
MRI is simply a noninvasive medical test that is used to diagnose ailment affecting the head. As mentioned above, the imaging process is achieved by using a combination of strong magnetic fields and radio waves, while advanced computer image processing is used to develop a detailed picture of the parts of the brain that are of interest. This imaging technical is particularly adept in producing detailed pictures of the soft tissues, organs, and bones. Thus, it can be used to intricately understand the body part of interest. In fact, MRI is the most sensitive imaging technology we have today.
Obviously, doctors can develop hard copies of the detailed images of the part of the head that is of interest. However, the images can also be monitored on a computer screen, transmitted from the lab to the doctor’s office electronically, copied to a CD for storage or upload to the cloud for storage and transmission. As you can appreciate, MRI scans are quite versatile to use.
Uses Of The MRI Imaging Technology
MRI as an imaging technology can and has been used to diagnose long-standing as well as abrupt ailments affecting the head, including but not limited to:
- 1. Brain Tumors
- 2. Stroke
- 3. Infections in the head
- 4. Causes of epilepsy
- 5. Hemorrhage in some trauma patients
- 6. Anomalies in development
- 7. Pituitary gland disorders
- 8. Hydrocephalus
- 9. Multiple sclerosis and other conditions
- 10. Inner ear and eye disorders, and
- 11. Vascular ailments.
Preparing For MRI
As mentioned above, there is not a lot of preparation required before going for an MRI examination. The main thing that the patient has to do is to wear proper clothing (loose comfortable clothes) with no metal. However, some technicians will require the patient to wear a medical gown. With regards to drinking and eating, patients can typically maintain their eating routine as long as it entails a healthy diet. However, for some specific examinations, and eating, drinking, and medication routine will be recommended to the patient by the technologist or by the doctor.
Determining Whether The Patients Has Any Pre-Existing Condition
Right before going in for the examination, the nurse, radiologist, or technologists typically asks the patient about allergies to certain contrasting material environments, food, drugs, or contrasting material. Additionally, they are supposed to enquire about any pre-existing condition that may affect the examination including whether you have asthma and whether you are claustrophobic. In the instance that a patient is claustrophobic or suffering from anxiety disorders, a mild sedative is usually given right before the examination.
As mentioned before, it is important for patients to divulge any relevant medical information relating to health issues that they may have. However, the nurse, technologist, or radiologist will enquire about any health issues. For instance, he or she may enquire whether you have a history of suffering from kidney diseases or any liver-related issue such as a liver transplant. If you have a history of these sought of health issues, further study will be required to ensure that your kidneys and liver are performing fine.
Determining The Risk Associated With Any Medical Implants
Typically technologist will also be interested in finding out whether you have any medical devices installed in your body. The implanted devices may interfere with the examination, although this is dependent on the nature of the examination and the strength of the magnetic fields that will be used. Nonetheless, it is important for the radiologist to understand the risk associated with implanted devices. To this end, patients are encouraged to carry with them the pamphlet given to explain the risk associated with MRI examination. The information on the pamphlet makes it easy for the doctors and the radiologist to determine the risk levels and whether the risk associated can be mitigated. Some of the medical implants that are of interest to the radiologist include:
- 1. Implanted drug infusion ports
- 2. Artificial heart valves
- 3. Implanted nerve stimulators
- 4. Implanted screws, pins, stents, or staples
- 5. Implanted joint prostheses, or artificial limbs.
For the most part, MRI can be performed on patients with medical implants in a safe yet efficient manner. However, the following patients should not enter the MRI room, let alone undergo an MRI scan:
- 1. Patients with pacemakers or cardiac defibrillators
- 2. Patients with medical clips in their brains
- 3. Patients with metal coils in their blood vessels
- 4. Patients with ear/cochlear implants.
Determining Whether There Are Any Metal Foreign Objects In The Patient
It is not just medical implants that are of interest to the radiologist. He or she is also interested in finding out whether you have any foreign object in your body, especially of metallic nature as they may affect the MRI examination. To this end, radiologists usually make a point of finding out whether their patients have foreign materials such as bullets, shrapnel, or any other kind of piece of metal in the bodies.
Aside from affecting the examination and distorting resulting, the metal is prone to movements while undergoing examination due to the strong magnetic field. As such, foreign metal objects need to be accounted for and the risk associated with their presence determines. This is especially important when the object is near sensitive organs such as the eyes.
The risk associated with having tooth fillings and tattoos also need to be determined. Tattoos with metal-based (iron-based) inks may heat up when exposed to a strong enough magnetic field.
As for tooth fillings, their presence is usually a non-issue. However, they may affect the accuracy of the image of the brain of facial parts by distorting the magnetic field. It is thus important for the radiologist to know that they are present.
MRI And The Pregnancy Issue
Moreover, for women, the issue of pregnancy is a concern to the radiologists and as such, he or she will inquire about it. Even though MRI has been used extensively in the past on pregnant women (since 1984), no reports of ill-effects on pregnant women and their unborn children have been recorded. Nonetheless, precaution dictates that pregnant women should not receive MRI examination in the first three to four months of their pregnancies. The reason behind this is to reduce exposure of the unborn child to the strong magnetic fields. Additionally, pregnant women should not receive gadolinium treatment. As such, for pregnant mothers, MRI examination should be conducted only in the event where the benefits of the examination outweigh the cons.
After establishing your suitability for examination, the patient is injected with a contrasting material that will not affect them. In the event a patient has an allergy to the iodine-based contrasting material, gadolinium is usually used as the alternative. It is by far, less common for people to be allergic to gadolinium-based contrasting material that iodine-based material. And when one is allergic to both kids of contrasting materials, pre-medication treatment under the patient’s consent allows gadolinium to be used.
The more traditional MRI units bear a cylinder-shaped tube, with the surrounding wall being containing the magnet. Patients the lie on a motorized table where they can be inserted and removed from the MRI machine automatically. The new MRI machines tend to have a larger bore, which improves the comfort of the patients, especially those who are claustrophobic.
The short-bore MRI machine tend are designed to not have the magnet completely surrounding the patients. The Open MRI machines are designed to be open on one side. This variety of MRI unit is perfect for claustrophobic individuals as well as individuals who are large. While traditionally the Open MRI has not been quite powerful as the conventional MRI machine, advancements in technology have enabled it to attain improved accuracy.
Every MRI unit has a workstation from which the radiologist controls the machine while at the same time monitoring the imaging progress.
The MRI Procedure
The unique bit of MRI machines is that they do not make use of ionizing radiation much the same like X-rays and Computed tomography does. MIR uses radio-frequency pulses to realign the hydrogen atoms that our bodies have, all the while not causing any chemical change in our tissues.
While the hydrogen atoms align themselves to their original state, they emit different levels of energy. The variation in the level of energy emitted depends on the type of tissues emitting the energy. The MR scanner thus picks up the emitted energy and uses the variation in energy levels to create an image of the tissues involved.
In the MRI unit, an electric current is passed through wire coils which create the magnetic field required. Other coils in the unit are designed to emit and receive radio waves. The computer thereafter processes the image of the signals received, thus forming an image of a thin slice of the head.
How is an MRI Examination Performed?
MRI examinations can be performed on inpatients and outpatients. The patient is usually positioned on a movable examination table. Bolsters and straps are sometime used to ensure that patients remain still and maintain proper positioning while imaging is underway.
Devices containing coils that can send and receive radio waves are placed either adjacent or around the area under examination. If the MRI is for the head, a device is positioned around the head.
If the MRI examinations requires the use of a contrast material, a technologist, nurse, or physician inserts an intravenous catheter (IV line), into a vein in the patient’s arm or hand. A saline solution is sometimes used to inject contrast material. This saline solution drips through the IV to ensure that the IV catheter does not block before the completion of the injection of the contrast material.
The patient is placed into the MRI unit’s magnet where the technologist and radiologist perform the exam while working at a computer situated outside the MRI room.
Once the exam is complete, the patient may be asked to wait while the radiologist or technician checks the images to see whether any additional images are required. The intravenous line is then removed.
MRI examinations usually involve several runs or sequences that may last for several minutes. It takes an average of 45 minutes for the entire examination to be completed.
The MRI examination, an additional procedure known as MR spectroscopy that provides additional information on the chemicals found in the cells of the body may also be performed and can add about 15 minutes to the total examination time.
What Can Patients Expect During and After the MRI?
MRI examinations are generally painless, but remaining still while the procedure is underway is uncomfortable for some patients. Other patients experience claustrophobia (fear of being in enclosed spaces) while in the MRI scanner. Sedation can thus be arranged for patients that anticipate anxiety but less than 5 percent of cases require medication.
It is perfectly normal for the area being imaged to feel a bit warm. However, if it becomes too much of a bother, the patient should notify the technologist or radiologist. Patients should stay perfectly still while the imaging is underway, which is usually just a couple of seconds to a couple of minutes at a time. Patients know when the recording of images is underway since they will feel loud thumping or tapping sounds when the activation of the coils generating the radiofrequency pulses happens. Some facilities provide headphones while others provide earplugs to reduce the intensity of the sounds the MRI machine makes. Patients can relax between imaging sessions, but will be required to maintain their positions without movement as much as possible.
Patients are usually alone in the exam room while the MRI procedure is underway. However, technologists are still able to hear, see, and speak to patients using a 2-way intercom. MRI facilities usually allow parents or friends to stay in the room as long as they are screened for safety in the magnetic environment.
During the exam, children are usually given appropriately sized headphones or earplugs. MRI scanners are well-lit and air-conditioned. Music can be played through headphones to help patients pass the time.
Intravenous injection of contrast material is sometimes administered prior to capturing of the images. The intravenous needle may be the source of some discomfort once inserted and the patient may experience some bruising. Patients may also experience irritation of the skin at the point of insertion of the IV tube. Other patients may experience a metallic taste in their mouths once the contrast has been injected, but it is just temporary.
No recovery period is needed if sedation is not necessary. Patients can resume their usual diet and activities once the exam is complete. On some rare occasions, patients might experience side effects from the contrast material, including headache, nausea, and pain at the injection site. Patients allergic to the contrast material may experience itchy eyes, hives, or other side effects. Patients that experience allergic symptoms should notify the technologist, radiologist, or any other health practitioner available for immediate assistance.
Who is Responsible for Interpreting Results and How Does the Patient Get Them?
Supervision and interpretation of radiology examinations is done either a radiologist or a specifically trained physician. It is also his or her responsibility to analyze those images and send a signed report to the patients referring or primary care physician that will then share those results with the patient.
Follow-up exams may be required. The doctor provides reasons for requesting additional examinations. Follow-up exams are sometimes done because further evaluation with a special imaging technique or additional views is required for a potential abnormality. Follow-up exams are sometimes the best way to determine whether treatment is working or whether a finding changes over time or is stable.
Benefits Vs Risks of MRI Examinations
The MRI exam is a noninvasive technique for imaging that doesn’t require exposure to ionizing radiation.
MRI exams help physicians evaluate brain structures and even provide functional information in some cases.
MRI facilitates the discovery of abnormalities that might not be apparent when using other imaging techniques.
MRI produces much clearer and more detailed images of cranial structures including the brain than with other imaging methods. This is why MRIs are an indispensable tool in early evaluation and diagnosis of various conditions such as tumors.
Contrast material used for MRI examinations is less likely to trigger an allergic reaction compared to iodine-based contract materials used for CT scans and regular X-rays.
A variant of MRI known as angiography (MRA) produces detailed images of blood vessels in the brain often without the need for contrast material.
MRI is capable of detecting stroke at the very early stages by mapping the movement of water molecules in the tissue. The motion of water is known a diffusion and is impaired by most strokes, usually within less than 30 minutes from the onset of the symptoms.
MRI exams pose close to zero risk to the average patient, but only when the right safety guidelines are followed.
The risk of excessive sedation is always present if sedation is to be used. However, the nurse or technologist usually monitors the patient’s vital signs to minimize the risk.
The strong magnetic field might not be harmful in itself, but implanted medical devices containing metal could easily malfunction or cause problems while the MRI exam is underway.
A rare but recognized complication associated with MRI exams is known as Nephrogenic Systemic Fibrosis. It is believed to be caused by the injection of massive doses of gadolinium-based contrast in patients whose kidneys function very poorly. The risk of this rare complication can be minimized by carefully assessing kidney function before considering a contrast injection.
If contrast material is injected, there is a slight risk of an allergic reaction. The reactions are often mild and medication can be used to control them. If the patient experiences allergic symptoms, a radiologist or another physician is available to provide immediate assistance.
Intravenous contrast manufacturers have indicated that mothers should avoid breastfeeding their babies 24 to 48 hours after the contrast medium is administered. However, both the European Society of Urogenital Radiology and the American College of Radiology have noted that the data suggests that breastfeeding after the intravenous contrast has been administered is safe.
What Are the Limitations of MRI Exams of the Head?
High-quality images are only assured if the patient is able to stay perfectly still and follow the breath holding instructions while the recording of the images is underway. Patients that are confused, anxious, or in severe pain might find it hard to stay still while imaging is underway.
Very large individuals may not fit into the openings of some types of MRI machines.
The presence of implants or other metallic objects sometimes makes obtaining clear images hard due to the streak artifacts from the metallic objects. Patient movement also has a similar effect.
A heartbeat that is very irregular can affect the quality of images obtained using techniques which time imaging on the basis of the heart’s electrical activity, such as electrocardiography.
For patients that have been injured acutely, MRI is generally not recommended. However, the decision is on the basis of clinical judgment. The reason for this is that traction devices along with various types of life support equipment can distort MR images and should thus be kept away from the area to be imaged. The examination also takes longer than other imaging techniques such as CT scans and x-rays and results might not be available immediately, as is usually necessary in trauma situations.
While no evidence suggests that MRIs can harm a fetus, pregnant women are often advised not to undergo the procedure especially if they are in their first trimester unless it is medically necessary to do so.