midterm 3 Flashcards
(38 cards)
Biological Effects
- STRENGTH,
- FREQUENCY
- DURATION OF EXPOSURE
- Magnetic fields used in everyday devices are typically low frequency, ___
- Not have enough energy to remove electrons from atoms or molecules, meaning it doesn’t directly damage DNA or cause ionization in tissues.
non-ionizing radiation.
MRI uses strong magnetic fields to align protons in the body. The magnetic fields can cause temporary sensations _____ and affect implanted medical devices like pacemakers.
like feeling warm
Some studies suggest that prolonged exposure to low-frequency EMFs might have subtle effects on tissues, like _____ though these effects are not well-established or universally accepted.
altering cell behavior, increasing oxidative stress, or influencing the nervous system,
Therapeutic Use of Magnetic Fields
- Pulsed Electromagnetic Field (PEMF) Therapy
- Transcranial Magnetic Stimulation (TMS)
form of therapy that uses electromagnetic fields to promote healing in damaged tissues, such as bones or muscles. Studies have shown it may improve circulation and accelerate the healing process by affecting cellular functions.
Pulsed Electromagnetic Field (PEMF) Therapy
non-invasive procedure used to treat conditions like depression and anxiety. It uses magnetic fields to stimulate specific areas of the brain, influencing neuron activity.
Transcranial Magnetic Stimulation (TMS)
- such as those used in certain industrial applications or scientific research, can have more direct effects on living tissues.
- They can interfere with the electrical activity of the heart or the nervous system if the field strength is
High-Intensity Magnetic Fields
effect of RF fields on living tissue primarily depends on factors
- Strength of the field
- Frequency
- Duration of exposure
- Type of tissue
- RF energy can be absorbed by tissues and converted into heat, which can raise the temperature of the tissue.
- They cause charged particles to move, which generates heat. The extent of heating depends on the frequency of the RF field and the properties of the tissue
- Tissues like muscle, fat, and skin absorb RF energy to varying degrees, with fat typically absorbing more energy than muscle. Small increases in temperature are generally harmless. However, if the temperature rises significantly (by 10°C or more), it can cause thermal damage to tissues
Heating Effects (Thermal Effects)
These limits are based on the heating effects of RF fields, which are considered the primary mechanism of harm.
Regulations and Safety Standards
SAR
Exposure Limits
measure of the rate at which the body absorbs RF energy. For mobile phones, the ___ limit is set by various regulatory bodies like the International Commission on Non-Ionizing Radiation Protection (ICNIRP) to ensure safe levels of exposure.
Specific Absorption Rate (SAR)
- vary depending on the frequency of the radiation. For example, in the case of mobile phones, ___ are typically set at levels that prevent the temperature of tissues from rising to dangerous levels.
- Workplace settings or medical environments, specific guidelines are in place to prevent excessive RF exposure.
exposure limits
Contraindications of MRI
Metal Implants or Foreign Objects
Pregnancy (First Trimester)
Severe Renal Dysfunction (for Gadolinium-based Contrast
Agents)
Claustrophobia
Contraindications of MRI
Metal Implants or Foreign Objects
- Pacemakers
- Implanted Defibrillators (ICDs)
- Cochlear Implants
- Metallic Clips or Staples
- Joint Implants or Prostheses
- Foreign Metallic Objects
- Dental Fillings and Braces
- Hearin Aids
- Insulin Pumps
While MRI is generally considered safe during pregnancy, particularly in the second and third trimesters, it is typically avoided during the ___ unless absolutely necessary. This is because of the limited research on the effects of strong magnetic fields and radiofrequency radiation on fetal development, though there is no conclusive evidence that MRI harms the fetus.
first trimester
Patients with severe renal dysfunction or kidney disease may be at risk of _____, a rare but serious condition caused by the use of gadolinium in patients with compromised kidney function. In these cases, MRI with gadolinium contrast should be avoided or used with extreme caution.
nephrogenic systemic fibrosis (NSF)
- MRI scanners are typically narrow and enclosed, which can cause discomfort or anxiety in patients with _____ (fear of enclosed spaces).
- While this is not a strict medical contraindication, it can make the procedure difficult. Sedation or the use of an open MRI machine may be considered in these cases.
claustrophobia
Uncontrolled Medical Conditions
Uncontrolled Medical Conditions
Implanted Neural Stimulation Devices
patients with ___may not be suitable candidates for MRI, as the magnetic field may interfere with electrical impulses in the heart, complicating control
uncontrolled arrhythmias
Patients with _____ may be at risk, as the strong magnetic field can interfere with the functioning of the device.
implanted brain stimulators or other neural devices
- Many MRI machines have a weight
limit for patients (usually around ___) - Larger patients may have difficulty
fitting into the MRI machine itself.
300 pounds or 136 kg
- cause heating or discomfort during an MRI. This is because certain metallic pigments can react to the magnetic field. However, the risk is typically low unless the tattoo contains large amounts of metallic pigment.
certain tattoos or body art
Safety measure in Magnetic field
Pre-screening for Metal Objects
- Screening of Patients and Personnel
- Metallic Objects
- Implanted Devices
