Download MRI ARMRIT Exam Questions And Verified Solutions 2026 and more Exams Electromagnetic Engineering in PDF only on Docsity!
MRI ARMRIT Exam Questions And
Verified Solutions 2026
Spatial resolution in MRI - correct-answer - The smallest object or detail that can be distinguished in the image. Slice thickness in MRI imaging - correct-answer - Increasing this parameter results in thicker slices. Resistive magnets in MRI - correct-answer - These magnets require continuous electrical power and cooling, and are limited to low field strengths. 3D imaging sequences - correct-answer - These sequences allow for very thin, contiguous slices with higher SNR per slice than 2D imaging. Gadolinium-based contrast agents - correct-answer - These agents shorten the T relaxation time of tissues, increasing their T1 signal intensity.
Surface coils - correct-answer - They produce high SNR because they are positioned close to the region of interest. Scan time in spin echo imaging - correct-answer - Directly affected by the repetition time (TR). Fat-water interfaces artifact - correct-answer - Caused by the frequency difference between fat and water protons, resulting in misregistration. Image contrast in T2-weighted sequences - correct-answer - Mainly influenced by the echo time (TE). Temporal resolution in dynamic imaging studies - correct-answer - Improved by decreasing the repetition time (TR) to acquire images more frequently. Post-contrast imaging sequences - correct-answer - T1-weighted sequences, often with fat suppression for better contrast.
Parameter differentiating normal from abnormal tissue in DWI - correct-answer - Apparent Diffusion Coefficient (ADC) MRI perfusion imaging examines microscopic blood dynamics through - correct- answer - Capillaries Role of licensed MR physician regarding questionable implants - correct-answer - Determine if the scan can proceed safely Extension of breast tissue into the axilla - correct-answer - Tail of Spence How to reduce blood flow artifacts in MRI - correct-answer - Use flow compensation Cause of zipper artifacts in MRI - correct-answer - RF interference Another name for phase mismapping artifact - correct-answer - Aliasing
How to reduce chemical shift artifact in MRI - correct-answer - Increase bandwidth Cause of phase mismapping artifacts - correct-answer - Motion during acquisition Direction motion artifacts typically appear - correct-answer - Phase Cause of aliasing artifacts - correct-answer - Under-sampling in phase direction Slice excitation pulses causing artifact - correct-answer - Crosstalk Method to significantly reduce cardiac motion artifacts - correct-answer - Cardiac gating Most likely cause of a zipper artifact - correct-answer - Open scanner door
Effect of increasing repetition time (TR) on scan time - correct-answer - Increases scan time Best way to increase spatial resolution without increasing scan time - correct- answer - Increase matrix, decrease FOV Echo train lengths producing shortest scan time - correct-answer - ETL = 4 Formula to calculate scan time in spin echo sequence - correct-answer - TR Phase matrix NEX Dimension of a voxel used in acquisition - correct-answer - Volume element Scan time - correct-answer - Directly affected by TR, flip angle, bandwidth, and shim settings. SNR - correct-answer - Not directly affected by slice thickness, receiver bandwidth, gradient strength, or field of view.
Doubling NEX - correct-answer - Doubles the scan time and increases SNR by 2. Increasing slice thickness - correct-answer - Decreases SNR. Receiver bandwidth reduction - correct-answer - Increases SNR but worsens chemical shift. Highest SNR settings - correct-answer - Achieved with thick slices, high NEX, and large voxel. Large voxels - correct-answer - Result in higher SNR because they collect more signal from a larger volume. Best approach to improve SNR - correct-answer - Increase voxel size or use surface coils.
Magnetic field homogeneity measurement - correct-answer - Measured using field mapping sequences. Common cause of thermal injuries in MRI - correct-answer - Conductive loops from ECG leads or wires. Not increasing SAR - correct-answer - Low field strength does not increase SAR. SAR measurement - correct-answer - Measures RF energy converted to heat in tissue. Safe to scan pregnant patients - correct-answer - Generally safe during any trimester with radiologist approval. Peripheral nerve stimulation classification by FDA - correct-answer - Considered a nuisance-level concern.
Stable gadolinium agent formation - correct-answer - Gadolinium is bonded to a chelating ligand. MRI screening for unresponsive patients - correct-answer - Should be completed by technologist and supervising physician. Cryogen for superconducting magnets - correct-answer - Liquid helium is used to cool superconducting magnets. Copper windings in MRI - correct-answer - Primarily used in RF amplifiers. Gradient coil for axial slice selection - correct-answer - Z-gradient is used for axial slice selection. X-gradient - correct-answer - A gradient in the x-direction used in MRI. Y-gradient - correct-answer - A gradient in the y-direction used in MRI.
Phased array coil - correct-answer - Composed of multiple elements, each connected to a dedicated receiver channel. Shim coils - correct-answer - Ensure uniformity of the magnetic field in the bore. 90 RF pulse - correct-answer - Produces the primary MR signal known as FID. Spin echo sequence - correct-answer - Uses a 180 RF refocusing pulse to rephase dephased spins. 180 pulse in spin echo - correct-answer - Produces the echo signal by refocusing spins. Inversion recovery - correct-answer - Uses a 180 pulse to drive magnetization toward - Z. GRE parameter influencing T1 contrast - correct-answer - Flip angle.
Fast Spin Echo (FSE) sequence - correct-answer - Uses multiple 180 refocusing pulses. Superconducting magnets at critical temperature - correct-answer - Have no resistance. Permanent magnet - correct-answer - Has the main magnetic field direction as vertical. Precessional frequency - correct-answer - Increases as magnetic field strength increases. MR active nucleus property - correct-answer - Magnetic moment. Nucleus with net spin - correct-answer - Described as having a magnetic moment. Image reconstruction in MRI - correct-answer - Uses Fourier transform.
MRI safety zone IV - correct-answer - The MRI magnet (scanner) room is designated as which MRI safety zone? MRI safety zone II - correct-answer - In which MRI safety zone are patient screening procedures typically conducted? Essential part of MRI screening - correct-answer - Checking for implants, removing metal, asking about surgeries (All of the above) History of metal grinding - correct-answer - Obtain orbital X-rays to check for metal fragments Not an absolute contraindication to MRI - correct-answer - Orthopedic titanium hip replacement 'MR Conditional' on a device - correct-answer - Device can be safely scanned only under specific conditions MRI sequence with highest SAR - correct-answer - Fast spin-echo (turbo spin-echo)
SAR change from 1.5T to 3T - correct-answer - SAR approximately quadruples Maximum whole-body SAR for adults in normal mode - correct-answer - 4 W/kg First action if a patient goes into cardiac arrest during MRI - correct-answer - Remove patient from MRI scanner before resuscitation Primary safety concern during a magnet quench - correct-answer - Asphyxiation from helium displacing oxygen Action during a fire in the MRI room - correct-answer - Quench the magnet and evacuate NSF linked to - correct-answer - Gadolinium use in patients with severe kidney dysfunction
Cause of muscle twitching during MRI - correct-answer - Induced currents from switching gradient fields Danger of steel oxygen tanks in MRI - correct-answer - They can become projectiles 5 Gauss line indicates - correct-answer - Boundary beyond which magnetic field is safe for the public/devices Larmor frequency - correct-answer - The strength of the main magnetic field (B0) Net magnetization at equilibrium - correct-answer - Oriented parallel to the external magnetic field (B0) 90 radiofrequency pulse effect - correct-answer - It flips into the transverse plane (perpendicular to B0) T1 relaxation process - correct-answer - Spin-lattice relaxation
T2-weighted MR image appearance of short T2 tissue - correct-answer - Dark, because its transverse magnetization decays rapidly Comparison of 1.5 Tesla and 3 Tesla MRI scanners - correct-answer - Provide higher SNR but also higher RF energy absorption (increased SAR) Purpose of 180 RF pulse in spin-echo sequence - correct-answer - To create an echo by refocusing dephased spins Key difference between GRE and SE sequences - correct-answer - GRE sequences use a gradient field to rephase spins instead of a 180 RF refocusing pulse Excitation of a specific slice of tissue in MRI - correct-answer - By applying a selective RF pulse in the presence of a slice-select gradient Role of the phase-encoding gradient in MRI - correct-answer - To impart position- dependent phase shifts in spins for spatial localization
