Lege Artis Medicinae

[BASICS OF MRI MAGNETIC RESONANCE IMAGING]

MARTOS János

SEPTEMBER 18, 2004

Lege Artis Medicinae - 2004;14(08-09)

[Magnetic resonance imaging (MRI) is a young, developing technology used to create images with extraordinary detail of body tissue or the brain by applying nuclear magnetic resonance phenomena. The MRI technique uses a pulse of radio-frequency energy to excite the hydrogen nuclei, the protons. The distribution of hydrogen nuclei of water and fat in the body depends on the tissue type and whether or not the tissue is healthy or diseased. The image brightness is a complex function of properties in the region of interest, which include parameters of protons density and the relaxation times of the protons. Manipulating these properties is accomplished by varying the experiment (pulse sequence) used at the time of examination to yield images that contains different contrast. Although MRI is normally a noninvasive technique, contrast agents can be administered to a subject to enhance a region of interest. There are now more than 22,000 MR systems in use worldwide. MR is one of the best diagnostic exams for imaging many types of soft-tissue including: the brain, the spine, the heart, aorta and coronary arteries, the organs of the upper abdomen and the pelvis as well as the joints.]

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Lege Artis Medicinae

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[The Hungarian Case-Control Surveillance System of Congenital Abnormalities can provide appropriate data for the evaluation of risk and benefits of drugs and pregnancy supplements in pregnant women. Among the main principles, the importance of time factor (the first trimester concept is outdated) and the explanation of frequent false teratogenic findings (e.g. recall bias, chance effect, etc.) are discussed. The main conclusion is that at present the exaggerated teratogenic risk of drugs is much more harmful for the fetus than the rare teratogenic effect of some drugs themselves. Medical doctors and other experts therefore need more education to know the principles and findings of modern human teratology because it may help us to have a better balance between the risks and benefits of drug use during pregnancy. On the other hand, the primary prevention of neural-tube defects and some other congenital abnormalities is demonstrated by periconceptional folic acid or folic acid-containing multivitamin supplementation. Unfortunately, this new method is used rarely and inappropriately (due to the late onset of supplementation) in Hungary.]

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