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Questions and Answers

What are the risks associated with MR scanning of active devices?

  • Device malfunction and therapeutic inhibition
  • Excess stimulation and damage to the device
  • Loss of data or communication and changing of detection sensitivity
  • All of the above (correct)

Which of the following is a risk for patients with passive implants during an MRI scan?

  • Induction of electrical currents (correct)
  • Increased heart rate
  • Allergic reaction to contrast dye
  • Nausea

What is the mechanism attributed to magnetic stimulation?

  • Change in the induced magnetic field along the axon (correct)
  • Direct stimulation of retinal receptors or optic nerve
  • Changes in calcium ion flux across cell membranes
  • Induction of electric fields in tissue

What is the role of the MR Medical Director (MRMD)?

<p>To ensure policies and procedures for MR safety are appropriate (C)</p> Signup and view all the answers

What are some potential consequences of thermal load on patients?

<p>Disrupted neural function (C)</p> Signup and view all the answers

Which weighting system for measuring sound levels is most suited to high SPL situations and is more linear than dB(A)?

<p>dB(C (C)</p> Signup and view all the answers

What is the torque on non-ferromagnetic objects?

<p>Very small (B)</p> Signup and view all the answers

What is the purpose of consulting MR conditions for medical devices?

<p>To obtain safety information for the medical device (D)</p> Signup and view all the answers

Which method is simpler and more commonly used for measuring magnetically induced torque according to ASTM F2213?

<p>The low friction surface method (C)</p> Signup and view all the answers

What is the HML rating used for in relation to ear protection devices?

<p>To determine the level of noise exposure at the ear with an ear protection device (B)</p> Signup and view all the answers

What is the importance of spatial gradient field and dB/dz in MR conditions?

<p>They differ between different MR scanners (C)</p> Signup and view all the answers

What is the term used to describe the average B1 exposure in MRI?

<p>B1+rms (B)</p> Signup and view all the answers

What is the frequency range of the RF region of the electromagnetic spectrum?

<p>3 kHz to 300 GHz (D)</p> Signup and view all the answers

Which two components make up MRI safety training?

<p>Academic training and local MRI-specific safety training (B)</p> Signup and view all the answers

What is the clinically relevant metric for measuring the stability of contrast agents used in MRI?

<p>Log Kcond (D)</p> Signup and view all the answers

What is responsible for PNS during MRI scans?

<p>Change in B (B)</p> Signup and view all the answers

What is the main cause of heating in metallic implants?

<p>RF transmission (B)</p> Signup and view all the answers

What is the recommended parameter for scan condition instead of SAR?

<p>B1+ RMS (A)</p> Signup and view all the answers

What is B1+ RMS?

<p>A new RF metric that reduces approximation, uncertainty, and potential error in SAR estimations (B)</p> Signup and view all the answers

What is the estimated incidence of Gd-related stillbirth or neonatal death?

<p>1 in 50 (C)</p> Signup and view all the answers

What is SAR in an MRI scan?

<p>A measure of the RF energy absorbed by the patient during the scan (B)</p> Signup and view all the answers

What is the purpose of a quench pipe in an MRI room?

<p>To exhaust helium gas in the event of a magnet quench (C)</p> Signup and view all the answers

What is the commonly used alloy for MRI magnets?

<p>Nb-Ti (A)</p> Signup and view all the answers

What is lead maturation?

<p>The formation of scarring around the embedded lead tip (B)</p> Signup and view all the answers

What determines the level of magnetization of a ferromagnetic object?

<p>The demagnetizing factors (C)</p> Signup and view all the answers

What is the magneto-hydrodynamic effect observed as?

<p>An artifact on electrocardiogram (ECG) traces (B)</p> Signup and view all the answers

What is the parameter used in time-varying noise measurement to measure equivalent constant SPL?

<p>Leq (B)</p> Signup and view all the answers

What is the Octave band method used for?

<p>To measure noise over eight octave bands and device attenuation figures (A)</p> Signup and view all the answers

What must be done to ferromagnetic firefighting equipment before entry into Zone IV?

<p>It must be quenched (B)</p> Signup and view all the answers

What are the three designated MR safety definitions for devices?

<p>MR Safe, MR Conditional, and MR Unsafe (C)</p> Signup and view all the answers

What is the recommended approach to limit SAR during MRI scans of pregnant women?

<p>Using hyperechoes and reduced flip angles (C)</p> Signup and view all the answers

What is the most important material for safety in the MRI environment?

<p>Ferromagnetic materials (C)</p> Signup and view all the answers

What are the three categories of medical devices in the MR environment?

<p>MR Safe, MR Conditional, MR Unsafe (B)</p> Signup and view all the answers

What is the maximum torque on a ferromagnetic object?

<p>Occurs at 45 degrees to B0 (B)</p> Signup and view all the answers

Which type of aneurysm clips can be unsafe in MRI?

<p>Those made of certain materials (D)</p> Signup and view all the answers

What is the role of the MR Safety Officer (MRSO)?

<p>To supervise day-to-day safe operation of the MRI unit (A)</p> Signup and view all the answers

What is the most plausible explanation for observed effects from SMF on diamagnetic molecules with a paramagnetic ion?

<p>Magnetic torque (D)</p> Signup and view all the answers

Which materials do not present a hazard in the MR environment?

<p>Diamagnetic materials (A)</p> Signup and view all the answers

What is the most sensitive bio-effect of time-varying magnetic fields?

<p>Peripheral nerve stimulation (D)</p> Signup and view all the answers

What is the recommended frequency for inspecting the quench pipe and vent?

<p>Annually (C)</p> Signup and view all the answers

Which type of stimuli has lower thresholds in magnetic stimulation?

<p>Both have the same threshold (C)</p> Signup and view all the answers

What is the ratio of σ/ρ shown in Table 9.3?

<p>The conductivity and resistivity of different materials (D)</p> Signup and view all the answers

What should be followed when using MR devices?

<p>The manufacturer's instructions (A)</p> Signup and view all the answers

What is the main interaction of RF with tissues in MRI?

<p>Faraday induction of an electric field E by the time-varying B1 RF magnetic field (B)</p> Signup and view all the answers

What does Example 11.10 outline?

<p>The maximum spatial gradient and static magnetic field conditions for a tibial external fixation frame (B)</p> Signup and view all the answers

What changes have in-vitro studies shown from RF induced tissue heating?

<p>Changes in cell morphology (B)</p> Signup and view all the answers

What do the dissociation half-lives of contrast agents used in MRI indicate?

<p>Speed of dissociation or kinetic stability (D)</p> Signup and view all the answers

How are dB/dz and B0 values shown in MR scanners?

<p>As contour maps (C)</p> Signup and view all the answers

Which factors affect SAR during an MRI scan?

<p>Flip angle, pulse duration, and RF pulse type (D)</p> Signup and view all the answers

How many deaths have been attributed to MR scanning of pacemakers?

<p>13 (D)</p> Signup and view all the answers

What are MR conditional pacemakers and ICDs?

<p>Pacemakers and ICDs that are designed to function safely in the MR environment (D)</p> Signup and view all the answers

Which zone requires lockable doors with restricted access for security?

<p>Zone IV (D)</p> Signup and view all the answers

Which material absorbs more power and heats tissue more?

<p>High conductivity, low permeability materials (B)</p> Signup and view all the answers

What is the estimated theoretical minimum ΔB for cardiac stimulation?

<p>480 mT (B)</p> Signup and view all the answers

What are the MR conditions that must be complied with for scanning patients with MR conditional pacemakers and ICDs?

<p>All of the above (D)</p> Signup and view all the answers

What is the significance of compliance with MR conditions?

<p>It ensures patient safety (B)</p> Signup and view all the answers

What is gadolinium?

<p>A rare earth transition metal used in MR for its paramagnetic properties (C)</p> Signup and view all the answers

What is the purpose of accreditation or certification in healthcare?

<p>To ensure the professional conduct of healthcare workers (B)</p> Signup and view all the answers

What is the role of the gradient coils in MRI?

<p>To vary the value of magnetic field in the z- or B0 direction (D)</p> Signup and view all the answers

What happens to PNS threshold as stimulus duration decreases or frequency increases?

<p>It increases (B)</p> Signup and view all the answers

Which frequency range is most likely to cause hearing impairment?

<p>4-6 kHz (C)</p> Signup and view all the answers

What is the purpose of gradient coils in MRI machines?

<p>To generate magnetic field gradients for spatial encoding (C)</p> Signup and view all the answers

What does Example 11.11 estimate for a tibial external fixation frame?

<p>The induced electric field, current density, and average SAR in tissue (B)</p> Signup and view all the answers

What is the most efficient way to reduce SAR during an MRI scan?

<p>Hyperechoes (D)</p> Signup and view all the answers

What is the unit of Specific Absorption Rate (SAR)?

<p>Watt per kilogram (W kg−1 (C)</p> Signup and view all the answers

Which scanning modes are used in MRI?

<p>Normal, First-level controlled, Second-level controlled (B)</p> Signup and view all the answers

What is the SLC80 method designed to be valid for?

<p>80% of wearers (C)</p> Signup and view all the answers

What is the fixed parameter option?

<p>A set of MR exposure parameters agreed by implant and MRI manufacturers (A)</p> Signup and view all the answers

What is the risk associated with magnetic forces on pacemakers and cochlear implants?

<p>Mechanical displacement (C)</p> Signup and view all the answers

When was FDA approval granted for full-body MRI for certain DBS systems?

<p>2015 (C)</p> Signup and view all the answers

What have cellular studies shown about amplitude modulated VHF exposures?

<p>They increase Ca++ flow from cells (D)</p> Signup and view all the answers

What is the role of the MR Safety Expert (MRSE)?

<p>To provide high-level advice on the safe use of MR equipment (B)</p> Signup and view all the answers

What is the torque on paramagnetic objects dependent on?

<p>The square of B0 (C)</p> Signup and view all the answers

Which type of orthopedic devices pose significant risks during MRI?

<p>External fixation devices, frames, and prosthetic limbs (B)</p> Signup and view all the answers

What other ions may compete for the ligands’ metal binding sites in vivo?

<p>Calcium, zinc, and iron (B)</p> Signup and view all the answers

What are the acute effects of exposure to strong magnetic fields from modern MR systems?

<p>Vertigo, nausea, and nystagmus (B)</p> Signup and view all the answers

What is the minimum magnetic field required for a 10% change in nerve impulse conduction velocity?

<p>24 T (C)</p> Signup and view all the answers

What are the contraindications for MRI?

<p>All of the above (D)</p> Signup and view all the answers

What is the effect of a magnetic field on reed switches in pacemakers?

<p>They become magnetized and have a directionality with respect to the magnetic field (B)</p> Signup and view all the answers

What is B1+ RMS in an MRI scan?

<p>A measure of the average B1+ over each 10-second period (C)</p> Signup and view all the answers

How can SAR be reduced during MRI scans?

<p>By decreasing the number of slices/echoes (B)</p> Signup and view all the answers

Which material produces similar heating to pure metal during the RF heating test?

<p>Carbon fiber (A)</p> Signup and view all the answers

What is the key tool for neuroscience research and therapeutic applications?

<p>Transcranial magnetic stimulation (B)</p> Signup and view all the answers

What is the criterion for MR safety in the deflection test?

<p>A deflection angle of less than 45° (A)</p> Signup and view all the answers

What is the orientation of a ferromagnetic object that experiences the maximum force?

<p>Parallel to the magnetic field (B)</p> Signup and view all the answers

What is the overall prevalence of allergic-like reactions to GBCA?

<p>0.092% (B)</p> Signup and view all the answers

What is a temporary threshold shift (TTS)?

<p>A short-term hearing loss (B)</p> Signup and view all the answers

What should practitioners provide for safe scanning of patients with active implants?

<p>Robust written policies and procedures (A)</p> Signup and view all the answers

How do GBCAs work in MR imaging?

<p>By reducing the relaxation time T1 in regions where the agent accumulates (B)</p> Signup and view all the answers

What is the American Board of Magnetic Resonance Safety (ABMRS) responsible for?

<p>Offering certification in MRMD, MRSO, or MRSE by examination (C)</p> Signup and view all the answers

What is the purpose of a ferromagnetic detection system in an MRI room?

<p>To detect objects in patients or staff (B)</p> Signup and view all the answers

What is the Lorentz force?

<p>The force on a current-carrying conductor at an angle to B0 (A)</p> Signup and view all the answers

Can magnetic stimulation affect respiration or the cardiac cycle in MRI scanner gradients?

<p>No (B)</p> Signup and view all the answers

Are all devices approved as MR conditional in every country?

<p>No (B)</p> Signup and view all the answers

What is the basis for testing device safety in the MR environment?

<p>The fringe field gradient dB/dz (C)</p> Signup and view all the answers

What is CEM43 used for in hyperthermia studies?

<p>Measuring thermal damage (C)</p> Signup and view all the answers

Which type of incident is the most frequent in MRI?

<p>Thermal incidents (B)</p> Signup and view all the answers

What is the purpose of Example 11.12?

<p>To modify a T2-weighted sequence to comply with SAR conditions for a medical device (D)</p> Signup and view all the answers

What is the ICNIRP guideline limit for MRI in the "First Level Controlled Mode"?

<p>8 T (B)</p> Signup and view all the answers

Which standard specifies 5 levels of protection based on LAeq,8 hr?

<p>Australian/New Zealand standard AS/NZS 1269.3 (B)</p> Signup and view all the answers

What is the purpose of demodulation and digitization in MRI?

<p>To process the MR signal (C)</p> Signup and view all the answers

What is the role of the MR Responsible Person?

<p>To mirror the administrative activities of the MRMD (D)</p> Signup and view all the answers

Why is SAR not uniform throughout the patient in MRI?

<p>All of the above (D)</p> Signup and view all the answers

Which contrast agent has the highest reported incidence of NSF?

<p>Omniscan (C)</p> Signup and view all the answers

Which type of medical devices are particularly susceptible to RF heating in MRI?

<p>Guidewires, catheters, and leads (C)</p> Signup and view all the answers

What is the most correct statement about lead dislodgement in active devices?

<p>It is unlikely to happen due to the Lorentz force (B)</p> Signup and view all the answers

What do Maxwell's equations allow for the existence of?

<p>Electromagnetic fields (A)</p> Signup and view all the answers

What is the purpose of a safety checklist in the MR environment?

<p>To detect unsafe objects in the MR environment (A)</p> Signup and view all the answers

What is the magnitude of the magnetic force compared to the force due to gravity when the object's long axis is aligned with the magnetic field?

<p>2.5 times greater (C)</p> Signup and view all the answers

What is the magneto-hydrodynamic effect?

<p>The generation of an electric field by the flow of charge within an external magnetic field (A)</p> Signup and view all the answers

What do radiologists, physicians, and medical physicists all require training in?

<p>MR safety (C)</p> Signup and view all the answers

What type of fire extinguisher should be available in Zone III?

<p>Carbon dioxide (C)</p> Signup and view all the answers

What is the basic restriction for movement lasting one second or more in the ICNIRP guidelines for MRI exposure?

<p>A peak B of 2 T or a field change ΔB of 2 T (A)</p> Signup and view all the answers

What is the correlation between power transmission frequency magnetic fields and childhood leukemia?

<p>Weak correlation (B)</p> Signup and view all the answers

What is the mean dB/dt rheobase for PNS from MRI gradient coils and its chronaxie?

<p>19.4 T s−1 and 0.42 ms (A)</p> Signup and view all the answers

What is off-label scanning?

<p>Scanning a patient with a medical device that exceeds or has unknown exposures (B)</p> Signup and view all the answers

What is the cooling mechanism in tissue that is most important?

<p>Perfusion of tissues by blood (D)</p> Signup and view all the answers

What is the proper term for "magnetic field strength" and what is its unit?

<p>Magnetic flux density, tesla (A)</p> Signup and view all the answers

What is the relationship between B1+ RMS and MR frequency?

<p>B1+ RMS increases with increasing MR frequency (C)</p> Signup and view all the answers

What is the most common detrimental bio-effect from RF exposure in MRI?

<p>Skin burns (C)</p> Signup and view all the answers

How is B1+ RMS calculated in an MRI scan?

<p>From the transmitter voltage required for a given flip angle (C)</p> Signup and view all the answers

What is the most problematic condition in interpreting the conditions for a particular implant?

<p>The spatial gradient condition (B)</p> Signup and view all the answers

What is the easiest method for applying hearing protection using the C-weighted average LCeq?

<p>The SNR method (B)</p> Signup and view all the answers

Which type of pulse sequence is used in MRI to reduce the number of lines of signal required to form an image?

<p>Parallel imaging (C)</p> Signup and view all the answers

What are commonly used for hearing protection in MRI?

<p>Ear plugs and ear defenders (B)</p> Signup and view all the answers

What is the standard patient dose for GBCAs?

<p>0.1 mmol−1kg−1 (C)</p> Signup and view all the answers

Which of the following is true about neurostimulators in the MR environment?

<p>Some neurostimulators are unsafe in the MR environment (B)</p> Signup and view all the answers

What is the heat transfer coefficient of the phantom material?

<p>0.54 (W m−1 °C−1 (A)</p> Signup and view all the answers

What is the strength of interactions dependent on in the MR environment?

<p>All of the above (D)</p> Signup and view all the answers

What is the MagnaSafe Registry trial?

<p>A trial that showed pacemaker-dependent patients can be scanned with appropriate safety measures (A)</p> Signup and view all the answers

What is the range of dB(A) considered to be unsafe in most countries if continuously exposed to for eight hours?

<p>Greater than 85 dB(A (B)</p> Signup and view all the answers

What is the website recommended for checking device-specific MR safety information?

<p>MRIsafety.com (D)</p> Signup and view all the answers

Why is patient weight essential for determining the safe limits of RF exposure in an MRI scan?

<p>It affects the scanner's estimation of SAR (A)</p> Signup and view all the answers

What is the region where magnetic field lines diverge and B-field decreases called?

<p>Fringe field (B)</p> Signup and view all the answers

How can RF burns be avoided?

<p>By limiting SAR (B)</p> Signup and view all the answers

Which is more effective in reducing SAR for spin echo sequences?

<p>Changing the RF pulse type (A)</p> Signup and view all the answers

What should be done with transdermal medicinal patches with metal foil backing prior to scanning in MRI?

<p>They should be removed (B)</p> Signup and view all the answers

What percentage of NSF cases occur in patients with chronic kidney disease?

<p>81% (A)</p> Signup and view all the answers

What is the primary way humans maintain their core body temperature at 37 °C?

<p>Metabolic activity (C)</p> Signup and view all the answers

Which gradient has the lowest thresholds for PNS?

<p>y-gradient (B)</p> Signup and view all the answers

Who is responsible for overseeing off-label MRI and recording details of the examination?

<p>The radiologist (B)</p> Signup and view all the answers

What are neurostimulators?

<p>Devices that stimulate the brain or nervous system (B)</p> Signup and view all the answers

What is the mechanism used for electrical stimulation?

<p>Induction of electric fields in tissue (B)</p> Signup and view all the answers

What is the most likely cause of metallic taste during an MRI scan?

<p>Direct stimulation of taste buds (A)</p> Signup and view all the answers

What is the purpose of the MR-linac machine?

<p>To administer radiation therapy (B)</p> Signup and view all the answers

What is the relationship between SAR and flip angle?

<p>SAR is proportional to the square of the flip angle (B)</p> Signup and view all the answers

What is the effect of abandoned leads in active devices?

<p>They pose a greater heating hazard than those connected to the pulse generator (A)</p> Signup and view all the answers

What is the translational magnetic force like within the bore of an MRI scanner?

<p>Very low (B)</p> Signup and view all the answers

What do MR safety guidelines cover?

<p>All of the above (D)</p> Signup and view all the answers

What can extend the RF fields in tissue beyond the volume of the RF transmit coil?

<p>Near field radiative effects (A)</p> Signup and view all the answers

What happens to non-spherical objects at an angle with respect to the magnetic field?

<p>They experience a twisting force or torque (C)</p> Signup and view all the answers

How can vagus nerve stimulators be safely scanned during MRI?

<p>Using a head T/R coil (B)</p> Signup and view all the answers

What should patients do before entering the MR environment?

<p>Remove all loose metal objects and change into scrubs or hospital gowns (A)</p> Signup and view all the answers

How are GBCAs cleared from the body?

<p>Through the kidneys (C)</p> Signup and view all the answers

What level of protection do formable ear plugs made of polyurethane foam offer?

<p>20-30 dB protection (C)</p> Signup and view all the answers

Which law describes how electrical charge and electric fields behave?

<p>Gauss's Law (A)</p> Signup and view all the answers

What can happen if the patient's weight is incorrect during an MRI scan?

<p>SAR limits may be exceeded, leading to potential burns (D)</p> Signup and view all the answers

What is the role of the RF transmit coil in MRI?

<p>To produce radiofrequency energy (C)</p> Signup and view all the answers

What is responsible for the attractive force on ferromagnetic objects in the fringe field?

<p>Fringe field spatial gradient (B)</p> Signup and view all the answers

What are the three types of materials that can be used in MRI?

<p>Diamagnetic, Paramagnetic, Ferromagnetic (A)</p> Signup and view all the answers

What is the material saturation point in T for ferromagnetic objects?

<p>1.0 T (B)</p> Signup and view all the answers

What is the resonant length?

<p>The length of a conductor that is close to one half wavelength λ/2 (C)</p> Signup and view all the answers

What is the "Second Level Controlled Mode" of MRI scanning?

<p>A mode that allows for research scanning at fields greater than 8 T but requires institutional research board (IRB) or medical ethics committee (MEC) approval (B)</p> Signup and view all the answers

What is the strength-duration curve used for?

<p>To show the minimum threshold for long stimuli and the stimulus duration for a threshold double the rheobase (C)</p> Signup and view all the answers

At what percentage of the threshold does a stimulus become uncomfortable?

<p>150% (C)</p> Signup and view all the answers

What is the upper critical temperature for thermoregulation?

<p>41 °C (D)</p> Signup and view all the answers

What are patient RF exposure limits set by?

<p>All of the above (D)</p> Signup and view all the answers

What are the three parts of the human auditory system?

<p>External, middle, and inner ear (A)</p> Signup and view all the answers

How does the level of protection offered by ear defenders compare to ear plugs?

<p>Ear defenders offer approximately the same level of protection as ear plugs (B)</p> Signup and view all the answers

What is the range of biological half-lives for GBCAs?

<p>12 to 24 hours (D)</p> Signup and view all the answers

What is the recommended course of action for administering GBCA during pregnancy?

<p>Use with caution if benefits outweigh risks (B)</p> Signup and view all the answers

Which materials are weakly ferromagnetic?

<p>Austenitic stainless steels (D)</p> Signup and view all the answers

What is necessary to assess heating risk of implants?

<p>Both A and B (C)</p> Signup and view all the answers

What causes artefacts in MRI?

<p>Disruption of magnetic fields (A)</p> Signup and view all the answers

What is the most correct statement about lead configuration in active devices?

<p>Bipolar leads may heat up more than unipolar (A)</p> Signup and view all the answers

What is the online device database?

<p>A database that contains information about MR unsafe and conditional neurostimulation systems (B)</p> Signup and view all the answers

What can happen with spinal cord stimulators during body MRI?

<p>Heating of the IPG and increased intensity of stimulation (B)</p> Signup and view all the answers

What are examples of MR conditional devices?

<p>Prosthetic heart valves, coils, filters, and stents (C)</p> Signup and view all the answers

What is the maximum time limit for SAR during scanning?

<p>15 minutes (C)</p> Signup and view all the answers

What does compliance with MR conditions ensure for patients?

<p>Safety during MRI scans (D)</p> Signup and view all the answers

What is the main safety concern with helium gas in an MRI room?

<p>Its displacement of air (D)</p> Signup and view all the answers

What is the purpose of quenching the magnet in an MRI unit?

<p>To release stored energy in the magnet (A)</p> Signup and view all the answers

What do industry standards for active implant manufacturers outline?

<p>Design specifications and testing methodology to establish and determine MR compatibility of active implants for hydrogen scanning at 1.5T in closed-bore systems (A)</p> Signup and view all the answers

What is the term used to describe the direction of magnetic field lines?

<p>Right-hand rule (B)</p> Signup and view all the answers

What is the maximum current density in an elliptical cross-section dependent on?

<p>Semi-major and semi-minor axes of the ellipse (C)</p> Signup and view all the answers

How is acoustic noise measured in an MRI scan?

<p>In decibels (A)</p> Signup and view all the answers

Why may passive implants have different interpretations for spatial gradient conditions?

<p>They do not have a clear maximum spatial gradient and static magnetic field condition (C)</p> Signup and view all the answers

What is the main limitation of the deflection test?

<p>Both A and B (C)</p> Signup and view all the answers

What factors affect SAR?

<p>Patient size, B0 and B1, number of RF pulses, and tissue conductivity (A)</p> Signup and view all the answers

What is the total ingested dose of GBCA for a breastfed infant?

<p>Less than 0.0004% (B)</p> Signup and view all the answers

What is the law of stimulation in terms of the imaging gradient parameters expressed as?

<p>Equation 4.9 (C)</p> Signup and view all the answers

What is the purpose of phase-encoding in MRI?

<p>To localize the MR signal within a slice (A)</p> Signup and view all the answers

What is the impact of high dB/dt on patients with active implants?

<p>It can cause overstimulation (B)</p> Signup and view all the answers

What should be done in case of impalement, trapping, or serious injury in the MR environment?

<p>The magnet should be quenched immediately (A)</p> Signup and view all the answers

What is the rate of metabolic activity in humans?

<p>1.4 W kg−1 (D)</p> Signup and view all the answers

What is the ratio of the force from torque to the translational force within the bore of an MRI scanner?

<p>12:1 (C)</p> Signup and view all the answers

What is the recommended approach to limit acoustic noise during MRI scans of pregnant women?

<p>Using acoustically optimized gradient pulses (A)</p> Signup and view all the answers

What is the relationship between the intensity of electromagnetic plane waves and distance?

<p>The intensity decreases with the inverse square law (B)</p> Signup and view all the answers

What is the force difference between RBC and plasma in comparison to the force difference arising from the magnetic field?

<p>Greater than the force difference arising from the magnetic field (A)</p> Signup and view all the answers

When are sacral nerve stimulators MR conditional?

<p>Only for head coil transmit (C)</p> Signup and view all the answers

What type of objects cause significant geometric distortions and signal loss/pile-up in MRI?

<p>Ferromagnetic objects (D)</p> Signup and view all the answers

Who should have contact with cryogenic equipment in an MRI room?

<p>Only cryogen-trained personnel (B)</p> Signup and view all the answers

What is the purpose of RF receiver coils in MRI machines?

<p>To detect micro-volt MR signals (C)</p> Signup and view all the answers

What happens when double protection is used for hearing protection?

<p>The attenuations do not result in the summation of attenuations (D)</p> Signup and view all the answers

What is the purpose of the NEMA MS 10 standard?

<p>To determine local SAR in diagnostic MRI systems (A)</p> Signup and view all the answers

What is the effect of reducing gradient amplitude, dB/dt or the number of gradient pulses per second on acoustic noise?

<p>Decrease in acoustic noise (C)</p> Signup and view all the answers

What is the implication of the in-vitro cellular effects of SMF for MRI exposures?

<p>They are unclear and require further investigation (B)</p> Signup and view all the answers

Why is accurate positioning of DBS electrodes important?

<p>To ensure proper stimulation of the brain or nervous system (B)</p> Signup and view all the answers

What is the effect of broken or intermittent leads in active devices?

<p>They present a different level of hazard (B)</p> Signup and view all the answers

What is the consequence of the static field B0 in relation to the spatial gradient condition?

<p>It creates a magnetic field gradient that is present at all times for a superconducting or permanent MRI magnet. (A)</p> Signup and view all the answers

What is the current advice regarding the use of GBCA during pregnancy and lactation?

<p>Use with caution (A)</p> Signup and view all the answers

What is the nervous system's response to high frequency fields?

<p>Insensitive stimulation (B)</p> Signup and view all the answers

What is the recommended way to handle excess extension lead for DBS electrodes?

<p>Coil the excess extension lead around or underneath the IPG can (B)</p> Signup and view all the answers

Can MR staff work normally in MRI at any time during pregnancy?

<p>Yes, but precautions relating to acoustic noise should be considered (B)</p> Signup and view all the answers

Are gastric electro-stimulators MR safe?

<p>No (B)</p> Signup and view all the answers

What mandates workplace noise levels for staff working in MRI?

<p>The IEC-60601-2-33 standard (A)</p> Signup and view all the answers

What is the Lorentz force in an MRI scan?

<p>The force that produces the knocking sound of the scanner (C)</p> Signup and view all the answers

What type of implants can pose a significant risk during MRI?

<p>Active implanted medical devices (C)</p> Signup and view all the answers

What is the formula for converting G cm-1 to T m-1?

<p>Divide by 100 (B)</p> Signup and view all the answers

What is the maximum core temperature increase unlikely to exceed during MRI examinations?

<p>2°C (A)</p> Signup and view all the answers

What is the most common type of sequence that produces loud acoustic noise in MRI?

<p>EPI (A)</p> Signup and view all the answers

How can gradient slew rates be reduced during MRI scans?

<p>By selecting a low acoustic noise waveform and reducing scanner noise (D)</p> Signup and view all the answers

What is the name of the coil that generates the B1 pulse in MRI?

<p>Birdcage coil (A)</p> Signup and view all the answers

Which model is used for peripheral nerve stimulation prediction and which model is used for cardiac stimulation in the IEC standard 60601‐2‐33?

<p>Hyperbolic model for PNS and exponential model for cardiac stimulation (C)</p> Signup and view all the answers

What is the purpose of the ACR Zoning system?

<p>To designate four distinct areas or zones for MR safety (A)</p> Signup and view all the answers

What is the effect of extremely low-frequency time-varying magnetic fields on excitable tissues?

<p>Moderate effect (C)</p> Signup and view all the answers

What is the vestibular ocular reflex (VOR)?

<p>The link between head rotational movement and eye viewing direction that can cause nystagmus (A)</p> Signup and view all the answers

What is the significance of induced electric fields from motion in the static field spatial gradient?

<p>They are implicated in some of the acute sensory effects (A)</p> Signup and view all the answers

What is the purpose of an electrical interlock on an MRI room door?

<p>To prevent or interrupt scanning (A)</p> Signup and view all the answers

What is the effect of time-varying magnetic fields on tissue?

<p>They induce electric fields in tissue (A)</p> Signup and view all the answers

What determines the magnetic force on a paramagnetic or diamagnetic object?

<p>The spatial gradient of the field (D)</p> Signup and view all the answers

What is the equation used to calculate the field generated at the center of a solenoid of length d with windings of density N turns per meter?

<p>B = μ0NI (B)</p> Signup and view all the answers

What is the RF exposure limit given in terms of?

<p>Core body temperature rise (B)</p> Signup and view all the answers

What should be included in a written MR safety policy?

<p>All of the above (D)</p> Signup and view all the answers

How can testing for artefacts in MRI be done?

<p>By scanning the device with a non-magnetic reference object in a paramagnetic solution (B)</p> Signup and view all the answers

What is important for maximum power transfer from amplifier to coil in MRI machines?

<p>Impedance matching (A)</p> Signup and view all the answers

What is the effect of scar tissue around the lead tip in MRI?

<p>It decreases the risk of thermal injury (B)</p> Signup and view all the answers

Which objects experience greater forces when aligned with the Bz axis?

<p>Elongated objects (B)</p> Signup and view all the answers

What is the method used to calculate the actual attenuation of hearing protective equipment?

<p>HML method (C)</p> Signup and view all the answers

What is the most common cause of MR accident deaths?

<p>Overdosing due to failure to follow instructions for using the device in the MR environment (C)</p> Signup and view all the answers

What is the preferred loop configuration for DBS electrodes?

<p>More smaller loops (B)</p> Signup and view all the answers

What is the main purpose of suitable sound proofing and acoustic noise survey in an MRI room?

<p>To reduce acoustic noise during scanning (C)</p> Signup and view all the answers

Which type of coil technology improves signal-to-noise ratio and enables parallel imaging?

<p>Array coil (D)</p> Signup and view all the answers

What type of objects should be approached with caution in MRI?

<p>Tattoos, piercings, cosmetics, and clothing with metallic components (A)</p> Signup and view all the answers

What is the maximum core temperature rise allowed during Normal Mode human scanning?

<p>0.5 °C (A)</p> Signup and view all the answers

What can result in surprisingly large eddy currents in implants during an MRI scan?

<p>Movement of the implant through dB/dz (A)</p> Signup and view all the answers

What is the term used to describe the rate of change of the magnetic field produced by gradients in MRI?

<p>Peripheral nerve stimulation (D)</p> Signup and view all the answers

What is the purpose of scanner software designed to assist with implant scanning?

<p>To report or restrict gradient dB/dt (A)</p> Signup and view all the answers

At what frequency does the SD curve depart from the usual hyperbolic or exponential form?

<p>Above 25 kHz (D)</p> Signup and view all the answers

What is the ACR Manual on Contrast Media's recommendation regarding breastfeeding after Gd administration?

<p>Safe to continue breastfeeding (C)</p> Signup and view all the answers

What can be created when the patient dimension or a conductor length is close to one half wavelength?

<p>Standing waves or resonances (B)</p> Signup and view all the answers

What is repetitive TMS (rTMS) used to treat?

<p>Psychiatric conditions, particularly depression (B)</p> Signup and view all the answers

Which organization has issued MRI safety guidelines that recommend the roles of MRMD, MRSO, and MRSE?

<p>The Royal Australian and New Zealand College of Radiologists (C)</p> Signup and view all the answers

How are SAR limits specified?

<p>For whole-body, partial body, head, and local transmit coils, and are averaged over six minutes (A)</p> Signup and view all the answers

What can be used if the deflection angle is less than 2°?

<p>A mathematical extrapolation (A)</p> Signup and view all the answers

What should be considered when designing the extent of the fringe field?

<p>The weight, expense, and effect on the magnet's shim of magnetic shielding (D)</p> Signup and view all the answers

What reduces the toxicity of gadolinium?

<p>Chelation (A)</p> Signup and view all the answers

What is the purpose of the side view diagram shown in Figure 11.3b?

<p>To show the exact location of the maximum value along the z-axis. (A)</p> Signup and view all the answers

How many pacing modes do pacemakers have?

<p>4 (C)</p> Signup and view all the answers

How can noise exposure be attenuated during an MRI scan?

<p>By using ear protection (D)</p> Signup and view all the answers

What is the dependence of magnetic torque on?

<p>Susceptibility (C)</p> Signup and view all the answers

What is the importance of engaging with the wider medical/hospital community in MR safety?

<p>To ensure the MR safety framework exists beyond the MR or radiology department (D)</p> Signup and view all the answers

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Study Notes

  • MRI is a widely used diagnostic imaging modality with superior soft tissue discrimination and no exposure to ionizing radiation.
  • MRI uses magnetic fields of varying frequencies that do not damage atoms, molecules, or cells.
  • MRI can involve significant risk to the patient and others present during the examination if safety protocols are not fully observed or understood.
  • The most hazardous environment within the radiology department is the MRI examination room.
  • The practice of MRI may involve significant risk when patients have implants, particularly active implanted medical devices (AIMDs).
  • MRI relies upon the properties of nuclear magnetism, specifically the nucleus of hydrogen.
  • The radiofrequency energy is applied as a magnetic field B1 orthogonal to the direction of B0.
  • Image formation is achieved by varying the value of magnetic field in the z- or B0 direction using gradient coils.
  • The localization of the MR signal within a slice is usually achieved by two processes: phase-encoding (PE) and frequency-encoding (FE).
  • Image acquisition requires multiple repetitions of the basic block of a pulse sequence using a different amplitude of PE pulse each time.
  • MRI uses pulse sequences and magnetic fields to produce images of the body's internal structures.
  • Gradient echo (GRE) and spin echo (SE) are two types of pulse sequences used in MRI.
  • Parallel imaging reduces the number of lines of signal required to form an image.
  • MRI has a wide range of clinical applications including brain, spine, musculoskeletal, and oncology imaging.
  • MRI hardware includes a magnet, RF transmit coil, gradient coils, and receiver coils.
  • Array coil technology improves signal-to-noise ratio and enables parallel imaging.
  • Demodulation and digitization of the MR signal are applied to the amplified RF signal.
  • The gradient and RF amplifier systems, control and signal processing systems, and cooling equipment are situated in the equipment or technical room.
  • The console and host computer are located in the control room.
  • MRI continues to evolve and expand its clinical applications.

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