Pregnancy as it Pertains to MRI - Essay Example

Pregnancy and MRI Jan 7, 2008 MRI Magnetic resonance imaging or what we usually call MRI is a method of obtaining extreme detailed images of organs and tissues throughout the body without the use of an x-rays. This technique makes use of a powerful magnetic field, radio waves, a continuously varying magnetic field and a computer system to illustrate and identify the presence of any injury or disease process. In order to carry out the process of MRI, the patient is placed within the MR scanner. A MRI scanner is a large, doughnut or a tunnel shaped magnet open at both ends. The magnetic field generated aligns the atomic particles, known as protons which are positively charged particles and are present in most of the body's tissues. These particles produce signals due to Radio waves that are collected by a receiver within the scanner. These signals are characterized with the use of varying magnetic field and are further processed by a computer in order to create ultra sharp images of tissues in the form of "slices" that can be viewed in any plane and from any direction. The key advantage of MRI is that it causes no pain and the responsible magnetic fields cause no damage of any kind to human tissues. The MR scanner used may generate considerably loud tapping or knocking noises during the process but it can be prevented using earplugs. A patient can easily communicate with the technologist or radiologist at any instant with the use of an intercom. Safety The magnetic field generated in the MR system is quite powerful and will attract Ferro-magnetic objects and can cause them to move suddenly and with a considerable force. Thus, there can be a risk to the person in the flight path of the object. Due to this reason, great care is taken and ferromagnetic objects like screwdrivers and oxygen tanks are not allowed into the MR system area. A patient is asked to remove all kind of metallic belongings like watches and jewelry before going for an MRI. The magnetic field of the MR system is of considerable magnitude and can pull on any iron-containing object in the body like medication pumps or aneurysm clips. Every MRI facility has a strict protocol that ensures that the MRI technologist and radiologist know about the presence of all metallic implants and materials so that special precautions can be taken. Sometimes, even the exam may have to be canceled. In case a bullet or other metallic fragments are present in the body, there is a risk that it could change position leading to an injury. A metallic implant can not only distort the MR images but also make it difficult for the MRI system to tune to your body. It is not possible to avoid it but allowance can be made while interpreting the images only if the radiologist is aware of their presence. Some MRI examines a gadolinium that may be injected into a vein in order to help the interpretation. a gadolinium is a contrast agent that does not contain iodine like those materials which are commonly used in x-ray process and hence rarely causes any problem or allergic reaction. Preparation for MRI The patient is asked to wear a special gown during the MRI study. The person (generally a friend or relative) accompanying you will be asked questions regarding the presence of implants and will be instructed to remove all metal objects from pockets and hair even before entering the room. A screening form is filled to ensure that the patient may safely enter the MR system room. The patient is asked to fill out a screening form before MRI exam asking about the possibility of anything that might create a health risk or interfere with the images obtained. Following items can create a health hazard or other problem during an MRI exam (Safety: Magnetic Resonance Imaging (MRI), 2005): Cardiac pacemaker or implantable defibrillator Catheter that has metal components that may pose a risk of a burn injury A metal clip placed to prevent bleeding from an intracranial aneurysm A medication pump (such as that used to deliver insulin or a pain-relieving drug) A cochlear (inner ear) implant Following items are need to be removed by patients and individuals before entering the MR system room1: Purse, wallet, money clip, credit cards, cards with magnetic strips Electronic devices such as beepers or cell phones Hearing aids Metal jewelry, watches Pens, paper clips, keys, coins Hair barrettes, hairpins Any article of clothing that has a metal zipper, buttons, snaps, hooks, underwires, or metal threads Shoes, belt buckles, safety pins Following objects can interfere with image quality if brought close to the area being scanned2: Metallic spinal rod Plates, pins, screws, or metal mesh used to repair a bone or joint Joint replacement or prosthesis Metal jewelry such as that used with body piercing Some tattoos or tattooed eyeliner (these alter MR images, and there is a chance of skin irritation or swelling; black and blue pigments are the most troublesome) Bullet, shrapnel, or other type of metal fragment Metallic foreign body within or near the eye (such an object generally can be seen on an x-ray; metal workers are most likely to have this problem) Dental fillings (while usually unaffected by the magnetic field, they may distort images of the facial area or brain; the same is true for orthodontic braces and retainers) Pregnancy and MRI Generally there is no risk of using MRI in pregnant patients. But still, MRI is restricted to be used for pregnant patients only in case of very important problems or suspected abnormalities. However MRI is quite safe for the fetus than imaging with x-rays. A patient should inform the radiologist in case she is breast-feeding at the time of a scheduled MRI exam and about to receive an MR contrast agent. Pumping breast milk before the study in an option in this situation which is to be used until injected contrast material has cleared from the body. These materials normally take 24 hours to get cleared from the body. Usually, MRI is not believed to be hazardous to the fetus (Curry, Dowdey, Murry and Christensen, 502). MRI is all safe and accurate for diagnosing pregnant women with acute pain in the abdomen and pelvis, where both CT as well as ultrasound is not used, says a study by researchers from University of North Carolina Hospitals in Chapel Hill, NC (American Journal of Roentgenology, 2005). The researchers analyzed the MR images of 29 pregnant patients who had been experiencing acute abdominal pain. The correct diagnosis was made in 28 patients. An exception was a case of ovarian torsion i.e. twisting of the ovary which was correctly identified in another patient. Around 14 different causes for the abdominal pain were diagnosed on MRI which includes appendicitis, ovarian cysts, hemorrhage and pancreatitis. The diagnosis of acute abdominal pain in pregnant patients can be a difficult task. "Diagnosis is complicated since the enlarged pregnant uterus pushes organs out of their normal locations, so that pain is not in the usual place. Also, there are more possible causes for pain, including not only non-pregnancy associated diseases, but conditions more common in pregnancy and conditions unique to pregnancy," said Richard C. Semelka, MD3. This study states that CT is normally used for diagnosing abdominal pain but a considerable dose of radiation is conferred to the fetus and can increase the risk of cancer in the fetus as well as mother. Sonography is safe from radiation but it is limited in what it can reveal for diagnosis. Ultrasound and magnetic resonance imaging (MRI) should be considered as alternatives in pregnant patients to computed tomography (CT) scans because both are non-invasive and are not associated with ionizing radiation (Pelsang, 287). The MR scanner uses a strong magnet in order to collect the naturally occurring magnetic fields inside the body. MRI causes a slight heating of the body which is not desirable for pregnant women. The effects of this on the woman's pregnancy are not yet completely known. Therefore, it is usually avoided especially during the first 10 weeks of pregnancy unless it is necessarily required (Littleton and Engebretson, 662). A decision to perform an MRI during pregnancy should be done only after discussing the issue with a doctor. There can be a situation where MRI is required for the diagnosis of a health condition and cannot wait until the baby is born and the only other possible alternative is an x-ray which is not desirable in case of pregnant women. however, the effects of magnetic field on the human fetus can not be easily determined (Yao, Malhotra and Fontes, 1235). There are no harmful effects of MRI prctise on the fetus. In fact, MRI avoids the use of ionizing radiation to which the fetus is quite sensitive. But still, MRI is recommended to pregnant women only when really required. The care taken for MRI in pregnancy is the same as for MRI in general but the only difference is that fetus may be more sensitive to the effects especially to the heat and noise. Also the use of contrast agents; gadolinium compounds which are known to cross the placenta and enter the fetal bloodstream. Hence, these compounds should be avoided. The importance of MRI is increasing due to the fact that it is a way of diagnosing and monitoring congenital defects of the fetus since it can provide more diagnostic information as compared to ultrasound without the ionizing radiation of CT. MRI is the imaging mode of choice especially as far as pre-surgical, primarily teratomas, in-utero diagnosis, evaluation of fetal tumors, facilitating open fetal surgery, other fetal interventions and planning for procedures to safely deliver and treat babies are concerned. The use of ultrasonography during pregnancy gives all the information about fetal and maternal well-being. But the image quality may be poor in some cases due to various reasons like maternal fat tissue and fetal position. MRI can provide clear images from multiple angles even without an exposure to the harmful X-ray. The clinical indications for MRI during pregnancy are limited but well defined (Takahashi, Iwagaki and Tamaya). References 1. American Journal of Roentgenology. Feb, 2005. 2. Curry, Thomas S. Dowdey, James E. Murry, Robert C. Christensen, Edward E. Christensen's Physics of Diagnostic Radiology. Lippincott Williams & Wilkins, 1990. 502. 3. Littleton, Lynna Y. Engebretson, Joan. Maternal, Neonatal, and Women's Health Nursing. Thomson Delmar Learning, 2002. 662. 4. MRI 'Excellent Choice' for Overcoming Challenges of Diagnosing Pregnant Women With Abdominal Pain. Retieved on Jan 6, 2008 from http://www.emaxhealth.com/84/1721.html . 5. Pelsang RE. Diagnostic imaging modalities during pregnancy. Obstet Gynecol Clin North Am 1998; 25: 287. 6. Takahashi, Y. Iwagaki, S. Tamaya, T. MRI during pregnancy. Volume: 31, Issue: 6. Nov 2003. 449-459. 7. Yao, Fun-Sun F. Malhotra, Vinod. Fontes, Manuel L. Yao and Artusio's Anesthesiology: Problem-Oriented Patient Managemen. Lippincott Williams & Wilkins, 2007. 1235. Read More