Download MRI Safety and Physics: Multiple Choice Questions and Answers and more Exams Health sciences in PDF only on Docsity!
MRSO EXAM 3 | QUESTIONS & 100 %
VERIFIED ANSWERS | LATEST UPDATE |
GRADED A+
Which of the following are physiologic factors that occur from an anaphylactic reaction? Select all that apply. a. Elevated creatinine levels b. Vasodilation c. Bronchial smooth muscle contraction d. Increased vascular permeability Correct Answer: b, c, d A non-emergent quench can take approximately how long? a. 1 minute b. 20 seconds c. 5-15 mins d. 2- 4 mins Correct Answer: c. 5-15 mins An emergent quench will take approximately 1 minute.
The roaring sound heard during a quench is caused by what? a. The sound of the ignition of the coils of wire used to heat the cryogen b. The massive volume of helium boiling off through the quench vent c. If a loud noise is heard, something is going wrong and you should evacuate. d. The sound of the system shutting down. Correct Answer: b. The massive volume of helium boiling off through the quench vent Which of the following will reduce the risk of patient burning in a pacing wire? a. Place pacing wire outside RF field b. Advance patient into scanner head first c. Don't scan patient d. Place an ice pack on patient's chest Correct Answer: a. Place pacing wire outside RF field A patient has removed a vagus stimulator with the leads left in, and is having a MR knee performed with the transmit-receive coil. In terms of patient heating, is it safe to scan? a. No
Correct Answer: a. A level 1 or 2 personnel should be available to help a MR personnel in Zone IV in non-emergent situations Lorenz's force can be used to describe what? a. Translation force b. The noise heard in the MRI c. Peripheral nerve stimulation d. Resonance heating Correct Answer: b. The noise heard in the MRI The rapids turning on & off of gradient coils causes a torque against the gantry. A contrast media with high relaxivity will do what when compared to contrast media with lower relativity? a. Produce more signal b. Produce less signal c. Improve resolution d. Produce more image noise Correct Answer: a. Produce more signal
To reduce pressure in an MR scan room during a quench with a faulty vent, what can be done? a. Drill a hole into the wall to Zone IV b. Wait 20 minutes for pressure to dissipate c. Open the door to Zone IV d. Break the window to Zone IV Correct Answer: d. Break the window to Zone IV Which of the following concerns can be caused by the time-varying gradient magnetic field? a. Anaphylaxis b. Diaphragm contractions c. Difficulty swallowing d. All of the choices Correct Answer: b. Diaphragm contractions Peripheral nerve stimulation that affects the diaphragm can cause it to contract in patients. This can cause problems for our patient making it difficult to breathe. Typically, where is the area surrounding the MR unit with the highest spatial magnetic gradient field? a. At the 5 Gauss line
Which of the following will create localized patient heating? a. None of the choices b. Body RF coil c. Receive only coil d. Transmit-receive coil Correct Answer: d. Transmit-receive coil Eddy currents are produced from which of the following? a. Moving MR table b. Gradient magnetic field c. All of the choices d. Static magnetic field Correct Answer: b. Gradient magnetic field As gradient coils are activated and deactivated, currents can be produced in conductive materials in our MR unit. These are eddy currents and cause artifact in our images. Which of the following is true if we increase the image matrix from 256 x 256 to 512 x 512? a. We use a weak time-varying gradient magnetic field b. We reduce patient heating
c. We reduce peripheral nerve stimulation d. We use a stronger time-varying gradient magnetic field Correct Answer: d. We use a stronger time-varying gradient magnetic field Larger image matrix will produce higher resolution exams. The size of the image matrix is dependent on the phase encoding gradient coil. When we increase the image matrix, we increase the amplitude of our gradient coil. The slew rate influences which of the following? a. Both the minimal TE and image matrix size b. The size of the image matrix c. The minimal matrix size d. Shorter echo spacing Correct Answer: d. Shorter echo spacing The speed of the gradient coils activating and deactivating will affect the speed of our scanner. Faster slew rates will decrease the minimal TE & TR. The faster our gradient coils can turn on & off means that the rise time is faster. This will allow our echo spacing to shorten and therefore promote faster imaging. What zone is the quench pipe located where it vents outside? a. Zone II
a. Use parallel imaging b. Using a conventional gradient sequence c. Increasing the TR d. Increase the ETL e. Decrease phase encoding f. Increase slices Correct Answer: a, b, c, e Parallel imaging will collect multiple lines of K space per each coil element. This reduces heating. The number of TR we need depends on the number of phase encoding lines that need to be filled in our K space. That means we need to deliver more RF pulses to fill more lines of K space. By reducing our phase encoding, we can reduce heating. If we increase the slices we need to collect, we will need to fill more K spaces. This means that more RF pulses are delivered during each TR. A phase encoding line is filled after every one of these 180 degree RF refocusing pulses. When discussing the distance from an RF transmitter and the biological effects witnessed, which of the following describes the area where the most energy is absorbed in implants? a. Danger zone b. MR table
c. Near field d. Patient's abdomen Correct Answer: c. Near field Which of the following are responsible for testing the safety of implants? a. EPA b. HIPPA c. FDA d. ASTM Correct Answer: d. ASTM ASTM is responsible for labeling of implants as MR safe, MR conditional, and MR unsafe. FDA doesn't do testing; reviews other testing to determine safety of objects. What is a risk with a non-ferrous pain pump? a. All the choices b. Lenz's force c. Translation force d. Rotational force Correct Answer: b. Lenz's force
a. Fast spin echo b. Gradient echo c. Inverse recovery d. Conventional spin echo Correct Answer: b. Gradient echo Gradient echo lacks 180 pulse and requires use of gradient coil to refocus hydrogen nuclei. This allows this sequence to be performed faster and will increase the speed of our working gradient coils. The changing gradient magnetic fields produced from the gradient echo will therefore produce faster time-varying magnetic activation that induction can occur in a patient. The result is peripheral nerve stimulation. Which of the following produce the least possibility of peripheral nerve stimulation using the same slew rate? a. 150 mm field of view b. 192 x 192 image matrix c. 320 x 320 image matrix d. 120 mm field of view Correct Answer: b. 192 x 192 image matrix Small image matrix forces use of shallow gradient amplitude, thus decreasing amount of gradient magnetic amplitude, so less opportunity for peripheral nerve stimulation.
Which of the following is true of gad contrast? Select all that apply. a. Gad has 7 unpaired electrons b. Gad is toxic to humans c. Gad is paramagnetic d. Gad will lengthen T1 relaxation times Correct Answer: a, b, c A patient has an insulin pump that is MR conditional. The manufacturer limits the implants to a spatial gradient of 5 T/m. According to this spatial gradient map, is it safe to scan this patient who is 6'5" for a foot MRI? a. Yes b. Any exam would be safe c. Have the patient apply pressure to the implant d. No Correct Answer: a. Yes Earplugs can reduce noise when used properly by how much? a. 0-20 dB b. 70-90 dB c. 0-10 dB d. 40-50 dB Correct Answer: a. 0-20 dB
A patient is undergoing an MR brain and has pacing wires. What would make this exam safe to perform? Select all that apply. a. Use only spin echo sequences b. Ice pack on the patient chest c. Using a transmit-receive brain coil d. It is not safe ever e. Increase the flip angle f. Increase TR Correct Answer: c. Using a transmit-receive brain coil Which of the following are considered biological effects of the static magnetic field? a. All of the choices b. Rotational forces c. Translational forces d. Magnetohydrodynamic effect Correct Answer: d. Magnetohydrodynamic effect Rotational and translational forces are mechanical, not biological Which of the following organizations is responsible for researching the effects of MRI environment on humans?
a. ICNIRP b. JCAHO c. FDA d. ACR Correct Answer: a. ICNIRP (International Commission on Non-Ionizing Radiation Protection) ACR - Safety policies When concerned with only the static magnetic field, which of the following is true of an object that deflects 30 degrees with a spatial gradient of 440g/cm? Your patient will be experiencing a maximum of 440g/cm during their scan. a. It is undetermined when discussing the static magnetic field. b. It is conditional only when discussing the static magnetic field. c. It is MR safe only when discussing the static magnetic field d. It is unsafe only when discussing the static magnetic field Correct Answer: c. It is MR safe only when discussing the static magnetic field We are currently subjected to 1 gravity (G) force in normal conditions. A deflection of 45 degrees indicates that the translational force is equal to gravity we are currently experiencing. Anything less than 45 degrees of deflection will have translational force
b. Captured c. Macrocyclic d. Polarized Correct Answer: c. Macrocyclic A patient is sweating profusely during an MR pelvis exam. What can be done to reduce this heating? Select all that apply. a. Increase the concentrations/number of acquisitions b. Decrease TR c. Scan the patient feet first d. Use fat sat sequences e. Use a gradient echo sequence Correct Answer: a, e The process where a gad ion breaks away from the ligand, and a phosphate and zinc ion attach to the ligand is called? a. Transmetallization b. Gad deposition c. Anthropogenic d. Chelation Correct Answer: a. Transmetallization
Which of the following will reduce patient heating? Select all that apply. a. Decreasing the bandwidth b. Increase TR c. Increase flip angle d. Using saturation bands e. Increase duration of RF exposure Correct Answer: a, b Which of the following can be given to a patient to relieve the symptoms of an allergic reaction? Select all that apply. a. Epinephrine b. Advil c. Diphenhydramine d. Corticosteriod Correct Answer: a, c, d A patient has a carotid stent and is having an MR knee performed. In terms of patient heating, is this patient safe to scan? a. Yes b. No
