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21 Cards in this Set
- Front
- Back
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How MRI is Used |
-been used for abnormalities with pregnancy for 15 years -utilized to assess a wide range of conditions and diseases that affect the pregnant patient and fetus |
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Polices Regarding Pregnant Patients and Staff |
1983, British Nuclear Regulatory Policy Bureau -“It might be prudent to exclude women (from MRI) during the first three months of pregnancy” 1989, US FDA -“ The safety of MRI when used to image fetuses and infants has not been established” |
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Standard of Care Policy |
1991, ACR: -MRI may be used on pregnant women if other non-ionizing forms of DI are inadequate or if the examination provides important information that would otherwise require exposure to ionizing radiation. Pregnant patients must be informed that, to date, there has been no indication that the use of clinical MR during pregnancy has produced any harmful effects |
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Safety Issues |
-possible effects of the static field -risks associated with the rapidly changing gradient magnetic field and gradient noise -potential adverse effects of the RF field -possible adverse effects related to the use of MRI contrast |
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Gradient Issues |
can be determined at the location of the fetus -but several different pulse sequences may be used during each exam |
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Static Magnetic Field |
no known side effects, but time in the scan room should be limited |
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RF Deposition and Absorption |
-will vary considerably with the MR system, RF coil and the pulse sequence that is used *EPI and TSE will deposit more energy than a gradient echo pulse sequence |
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RF Absorption |
varies considerably within the human body (87% would be deposited in the outer 1/3 of the body) -fetus will receive relatively small RF exposure -convective heat transfer to the amniotic fluid will enhance cooling -decreased radiate heat loss due to filling the bore |
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Acoustic Gradient Noise |
greatly reduced: due to position and amniotic fluid |
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MRI Contrast |
placenta is very vascular therefore MRI agents show prominent placenta localization when used during MRI Examinations - should only be used during pregnancy if the potential benefits justifies the potential risk to the fetus -animal effects: adverse and non-adverse -human effects: non-adverse |
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MRI Contrast: Brain Imaging |
-best evaluated with MRIs -Contrast should be reserved for those patients in whom diagnosis or therapy is needed immediately |
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Spine Imaging |
used for disc protrusion, spinal tumor, infection, syrinx or unstable fracture -all would require emergency c-section |
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Head and Neck Imaging |
-better than CT because no ionizing radiation -less chance of using contrasT -CT is the best modality for imaging bone fractures |
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Chest and Cardiac Imaging |
Can see: Hilar and mediastinal nodes, coarctation of the aorta, aortitis, aortic dissection, and arterial myxoma -echocardiogram is still the standard for many heart studies |
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Abdominal Imaging |
-sonography = modality of choice -use MRI for: tumors, pseudocytes and abscesses |
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Musculoskeletal Imaging |
-Routine exams can often be delayed until after the delivery -Suspected tumors or infections should be dealt with immediately |
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Pelvis Imaging |
-Pregnancy can accelerate the growth of benign and malignant pelvis masses -sonography may have difficulty with distinction of abnormalities --> MRI may better delineate and characterize these abnormalities. -used over x-ray and CT |
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Imaging of a Fetus |
-not widely used -confirms most ultrasound detected abnormalities --> most often used for the brain |
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MRI Contrast |
-massive doses have been shown to cause post-implantation fetal loss, retarded development, increased locomotive activity and skeletal and visceral abnormalities |
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Guidelines for the use of MR in Pregnant Patients |
MR should not be withheld in the following: -patient with active brain or spine signs & symptoms requiring imaging -cancer that requires imaging -Patients with Chest Abdomen & Pelvis signs and symptoms of active disease and ultrasound is non diagnostic -cases of suspected fetal anomalies |
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Pregnant Healthcare Workers |
-permitted to work in and around the magnet room -can be exposed to several hundred guass for a prolonged period time -there are no increase in adverse outcomes for pregnant MRI workers |
