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RT411- Exam 1
| Question | Answer |
|---|---|
| Zone 1 | Open and freely accessible to the public |
| Zone 2 | supervised area, usually for patients and their families |
| Zone 3 | computer/control area; locked and restricted to only MRI personell or screened individuals; non MRI personell must be accompanied |
| Zone 4 | MRI Room; only patients and MRI personnel with screened individuals |
| What areas are considered zone 1 | entrance to hospital, public hallways |
| What areas are considered zone 2? | changing areas; pt. interview space; bathrooms |
| What places are considered zone 3? | MRI control room, patient holding, transfers to MRI safe mobility aides |
| What places are zone 4? | the MRI room |
| What is the job of the MR Medical Director (MRMD)? | Physician responsible for the MRI safety program of an MR department; defines the MR Safety educational requirements |
| What is the job of the MR Safety Officer (MRSO)? | used a specialized technologist; will maintain safety policy and procedures in concert with the MRMD |
| MRI Personnel Level One | Those who have passed minimal safety educational efforts to ensure their own safety as they work within Zone 3 |
| MRI Personnel Level Two | those who have been more extensively trained and educated in the broader aspects of MR safety issue |
| Non MRI Personnel | any individual or group who within the previous 12 months have not undergone designated formal training in MR safety issues defined by the MR safety director |
| Translational Forces | attraction of objects to the bore of the magnet |
| What happens to translational forces as they approch the magnet's isocenter? | Increases |
| Rotational Force | Torque or twisting of devices |
| Where is the greatest movement for rotational force? | at the isocenter |
| Who should be screened before entering MRI department? | everyone |
| What are the two types of screening before an MRI? | written and verbal |
| How often should you be screened for MRI? | Every time you enter |
| What research should you do before scanning an unconscious, unresponsive, or altered mental state patient? | Gather info from family & friends, look in medical records, Use X-ray |
| How to screen minors/pediatrics? | gather information from family, screen once with parents, then again without |
| T/F: it's okay to assume the safety of an implant or device if it isn't clearly documented in writing | False |
| T/F: Never take a phycisian's verbal statement regarding an implant | True |
| What documented proof does a patient need for implants or devices | Device/implant card, operative notes with details on the device |
| T/F: If a patient has gotten an MRI somewhere else, they are also safe for your machine? | False |
| What should you assess regarding patient attire/cosmetics? | remove all metallic personal belongings, look for metallic cosmetics, change into MR safe hospital gown |
| What six questions should be asked when screening? | previous surgery, previous injury, metallic foreign bodies, metallic objects, chance of pregnancy, contrast reactions |
| What can be used over metallic objects that cant be removed? | Ice |
| Who is the largest group needing MRI sedation? | Pediatric Patients |
| T/F: Every patient should be verbally and visually monitored during an MRI | True |
| Who may need to be physiologically monitored during an MRI? | Sedated, comatosed, unresponsive, pediatric, deaf, or mute patients |
| T/F: Pregnant patients face no risk during MRIs | False, unknown potential risk is heating |
| Green square with MR in the middle means? | MR safe (no hazards in any environments) |
| Yellow Triangle with MR in the middle? | MRI conditional (can pose risk in specified MR environment) |
| Red circle crossed off with MR in middle? | MARI Unsafe (item has a known hazard) |
| What to do if you discover an implant during a scan? | contact radiologist/ MRMD, continue the scan or immobilize the patient (depending on multiple factors), contact physician who manages the device |
| T/F: the T wave can be elevated during an MRI scan? | True |
| How should you remove a patient from the scanner if you discover a device? | slowly, along a straight parallel to the center of the magnet |
| Where should a code blue never be ran? | Zone 4 |
| If a patient has a MRI card from 2008 or before, can you trust their card? | No |
| Temperature and humidity in an MRI room? | 65-70 degrees, 50-60% humidity |
| Why is the humidity and temperature important in an MRI room? | maintains the magnetic field of the permanent magnets |
| what gauss line is the public restricted to? | The 9 Gauss line |
| What is used for magnetic field shielding? | Passive- steel or concrete walls Active- solenoid magnets to force field lines to an acceptable location |
| RF Shielding? | uses faradays cage; keeps RF from entering or leaving zone 4 |
| What does a quench do? | boils off the liquid helium in the machine (shuts off magnet) |
| T/F: Emergency shut down turns off the magnetic field | false |
| What is the static magnetic field? | the main magnetic field |
| What is the static magnetic field expressed in? | Tesla |
| 1 Tesla is equal to? | 10 kilogauss (kG) or 10,000 gauss (G) |
| Magneto-hydrodynamic effect? | change in T-wave of ECG because of flowing blood moving across a magnetic field; proportional to strength of magnetic field |
| Faradays' Law | changing a magnetic field will induce a voltage and current in a perpendicularly oriented electrical conducto |
| Lenz's Law | The induced current will generate a secondary magnetic field that opposes the original magnetic field |
| Eddy currents | swirling magnetic currents that can produce heating in tissues or peripheral nerve stimulation |
| What are Gauss Lines | invisible lines that show the magnet's strength |
| What happens to Gauss lines as they get further away from the magnet? | they get further away (magnet gets weaker) |
| What gauss line was public restricted to until 2024 | 5 gauss line |
| What do mobile MRI units use as shielding? | Active shielding (two magnets with the same poles) |
| Faradays cage is what? | Room lined with copper to keep radio frequencys in |
| Permanent Magnet | once magnetized it is always on |
| resistive magnet | creates a magnetic field through copper wires providing electricity |
| conductive magnet | magnet cooled with helium which allows electricity to be used with no resistance |
| when does a quench occur | installation, deinstallation, emergency, spontaneous |
| what can happen if you're in the room during a quench with white fog/clouds in the room | asphyxia, hypoxia, confusion, frostbite, fire |
| why are doors that open in bad for MRI? | gas pressure build up will not allow you to open the door in |
| static magnetic field | magnetizes tissues (specifically hydrogen) |
| Radiofrequency field | protons absorb energy from RF pulse |
| gradient field strength | take a signal from the patient and puts it in a matrix |
| biological effects of static magnetic field | elevated t-wave, fatigue, headache, hypotension, irritability |
| what is the magneto-hydrodynamic effect | change in t-wave because flowing blood gets messed up from magnetic field |
| T/F: magneto-hydrodynamic effect gets worse with stronger magnets | True |
| What are the FDA guidelines for how many tesla can be used in an MRI machine | 8T |
| MRI concerns with Eddy currents | they can produce heating in tissues or peripheral nerve stimulation (Heats up implanted devices in patients) |
| biological effects of radio frequency | heating of tissues and structures such as lens of the eye (causes cataracts) |
| specific absorbtion rate (SAR) | rate of heat/energy dissipation in a patient's tissues is expressed in W/kg |
| FDA guidelines for SAR | 4.0 W/kg for whole body; 3.2W/kg for head |
| best measurement of SAR | patients height and weight, resonance frequency, type of RF pulse, type of RF coil used, volume of tissue with RF coil, orientation of body to MRI field |
| the higher the RF pulse the higher the ________? | heat in the patient |
| normal mode MR operation | Will not cause stress – suitable for all patients up to 2T (limits heating to 2 W/kg) |
| First Level Controlled Mode | may cause stress – requires medical supervision up to 4T and positive action by operator to enter; (limits heating to (4 W/kg) |
| Second Level Controlled Mode | to enter into this mode- IEC says needs IRB approval for use in over 4T- FDA says over 4T requires investigational device exemption (IEC) (heating that would be greater that 4 W/kg |
| Time Varying Magnetic Field | the magnetic field is varied linearly over time by the application current to the gradient coils |
| effects of time varying magnetic field | mild cutaneous sensations, involuntary muscle contractions, cardiac arrhythmias, acoustic noise, magneto-phosphenses |
| Acoustic noise | Gradient coils allow for the manipulation of the strength of the static magnetic field |
| Acoustic noise FDA guidelines | 02 decibels for one hour of continuous noise exposure |
| Magneto-phosphenes | visual disturbances caused by the stimulated retinal phosphenes; “star in the eye” or “light flashes |
| FDA guidelines for time varying magnetic field | Limit to when the patient experiences discomfort. |
| other names for gradient magnetic fields | time varying magnetic field, moving magnetic field, transient magnetic field |
Created by:
jayciebest