Download Armrit review test (380 Questions with Precise Solutions) 2025 latest updated and graded 1 and more Exams Magnetic Resonance Imaging (MRI) in PDF only on Docsity!
Armrit review test (380 Questions with Precise
Solutions) 2025 latest updated and graded 100%
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The exact middle of the bore of the magnet is termed: - Solution Isocenter Without proper safety limits on the MR system exposure to the time-varying magnetic fields created by the rapid switching of the gradient could create a potential environment for: - Solution Including electrical current in the patient's tissues Faraday's Law deals with induction of a current by a magnet. true or false?
- Solution true The orientation of the main magnetic field of a low field permanent magnet is vertical. True or false? - Solution True ; permanent lowfield magnets utilize a magnetic field oriented vertically Superconductive magnets have high homogeneity compared to other magnets types. true or false? - Solution true ; One advantage of a superconductive magnet is its excellent homogeneity The start up cost for a superconductive magnet is high. true or false? - Solution true ; Initial cost may exceed two million dollars in addition to the expensive cyrogen up keep. A type of magnet that is generally used for a 1.0t or a 1.5t system is a: - Solution Superconductive magnet The basic type of magnets used in MR are: - Solution Permanent, resistive , superconductive A procedure called shimming: - Solution Adjust the magnetic field to achieve the most homogenous field Superconductive magnets utilize two types of cyrogens. - Solution Helium and nitrogen
Types of transmit coils are: - Solution a) Body, b) head, c) volume coils, d) all of the above. D all of the above Various types of receiver coils are: - Solution a) solenoidal coil, b) volume,birdcage,surface coil, c) Helmholtz pair coil, d) All of the above: D all of the coils are true receiver coils To gain SNR and gain high resolution: - Solution Use a small surface coil Which of the following is not an example of a surface coil: - Solution body coils are not surface coils In a cross-sectional view of the magnet bore, which set of coils are the closest to the bore? - Solution RF coil- the cross sectional of the MR system reveals the order of thecoils: the magnet bore, then the RF coils, Then the gradient coils, then the shim coils & the outer most are magnet coils. MR systems can be shielded by two processes. They are: - Solution Passive and active shielding The more expensive type of shielding that uses additional solenoid magnets outside the cyrogen bath that restricts the magnetic field line to an acceptable location is the: - Solution Active- passive shielding can be accomplished by lining the walls with steel while the more expensive alternative is active shielding Surface coils are connected inside the scanner by cables. These cables shouldnt touch the patient because: - Solution They could burn the patient. Quadrature design coils give you a lower SNR. true or false? - Solution True: Quadrature coil designs improve SNR due to increased coverage. The two coils in a magnet used to transmit RF are the shim and tune coils. true or false? - Solution False: transmit coils are usually the body and head coils. Magnetic field gradients are generated by what? - Solution coils of wire situated within the bore of the magnet.
If the Nyquist theorem is not adhered to in the MR experiment what is the result? - Solution Aliasing At equilibrium more nuclear spines are________ with the magnetic field. - Solution In Alignment When the magnetic field is energized the nuclear spins start to return to process, as they return to equilibrium they give of: - Solution NMR signal Repeatedly applying RF pulses at time internals less than the T2 & T times of the tissues refers to: - Solution A steady state- a steady state is a condition where the TR is shorter than the T1 & T2 times of tissues. In an MRI expirement , what occurs first after RF excitation - Solution T2* Decay The most widely used pulse sequence is: - Solution Spin-Echo For the spin-echo pulse sequence, FID is the signal used to create the image. true or false? - Solution False- pulse sequence echoes are the MR signals that make an image in SE scans The signal produced immediately after a RF pulse is: - Solution FID - signal produced immediately after a RF pulse. Which of the following is not an intrinsic parameter effecting image contrast? - Solution Repetition time At 1.0T fat has a T1 relaxation time of approximately: - Solution 180msec At 1.0T the T2 relaxation time of water is approximately: - Solution 2500msec At 1.0T the T1 relaxation time of CSF is approximately: - Solution 2000msec At 1.0T the T2 relaxation time of white matter is approximately: - Solution 80msec The T1 time of fat is said to be: - Solution Short
The molecular mobility in water (CSF) causes the T1 time of water (CSF) to be: - Solution Long- The NMV of water takes longer to realign & the T1 of water is long The T2 time of fat is said to be: - Solution Short The T2 time of water is said to be: - Solution Long The relative number of protons per unit volume defines: - Solution PD - Protons denisty refers to the relative # of protons per unit volume of tissues An example of tissue with a low proton density would be: - Solution Cortical Bone Which of the following statements is true: - Solution Fat has a Short T1 & a short T How does the signal from fat & water appear on T2-weighted images? - Solution Dark fat & bright water Which of the following statements is true of T1-weighting? - Solution TR controls the amount of T1-weighting. (because the TR controls how each vector can recover before it is excited by the next RF pulse to achieve T1- weighting the TR must be short) Which of the following statements is true of T2-weighting? - Solution TE controls the amount of T2-weighting; for T2-weighting the TE must be long on SE The contrast from PD, T1, T2, occur simultaneously & contribute to the image contrast; true or false? - Solution True For a T1-weighted image you would want to: - Solution exaggerate T1 & diminish T For a T2-weighted image you would want to: - Solution Exaggerate T2 & diminish T For a T1-weighted image you would use a: - Solution Short TR & Short TE
Fat has a short T1 & a short T2. true or false? - Solution true What timing parameters are selected by the operator when performing a gradient recalled echo sequence? - Solution Flip angle, TR, TE In order to produce images based on differences in T1, the time interval between 90-degree excitation pulses should be: - Solution Short how does signal from cerebral spinal fluid appear on a standard short TR & short TE, Spin echo pulse sequence in which no suppression techniques have been used? - Solution Dark - T1 water & CSF appear dark How does signal from fat appear on a standard short TR & short TE, SE pulse sequence in which no suppression techniques have been used? - Solution Bright - Fat is bright on T How does signal from CSF appear on a standard long TR & Long TE. Spin echo pulse sequence in which no suppression techniques have been used? - Solution Bright - water appear bright on T In gradient echo imaging what parameters control the amount of T wieghting of the images? - Solution TR & Flip angle To be considered a T2 weighted image the TE range of a SE sequence shoulde be: - Solution 80 to 120ms As the TE is increased the signal intenstity of successive SE will: - Solution Decrease in a gradient echo pulse sequences a steady state is achieved & in the condition the TR is: - Solution Less than the T1 & T2 of the tissues When doing a coherent gradient echo pulse sequence that is T2* weighted in order to maintain the steady state the flip angle should be in the range of:
- Solution 30 to 45 degrees There are two methods to acheive RF spoiling with a gradient echo sequence that relies on incoherent residual transverse magnetization. They are used mainly to produce what type of image? - Solution T
When performing a conventional gradient echo sequence with a flip angle of 60 degrees. What type of images will be produced? - Solution T weighted When doing a fast gradient echo sequence, one way to decrease the sequence time is by increasing the receiver bandwidth. However what would be the disadvantage to this? - Solution Reduce SNR the driven equilibrium tissue prepared gradient echo sequences will produce what type of image contrast? - Solution T A gradient echo image with a Flip angle of 10 degrees will exhibit what type of contrast? - Solution T2-the larger the flip angle increase the degree os saturation therefore T1 contrast is increased Gradient echo acquistion techniques are divided into two catergories. Which of the following is not one of them? - Solution a) spin density b) 2D c) 3D d) all of the above:: A in a gradient echo imaging TR of 200-400ms & large FA provide T weighted images. true or false? - Solution False In a spin echo sequence if the operator selects along TR & a long TE what will be the effect on the apperance of CSF? - Solution Will appear High intensity In order to increase the T2 weighting of a scan the operator increases the TR from 200ms to 4000ms. What will be the effect on the scan time? - Solution Scan time will Increase The # of protons in the area under examination determines the amplitude of signal received. true or false? - Solution True - The more protons the more signal TR determines the amount of T1 & PD weighting. true or false? - Solution true The TE controls the amount of T2 weighting. true or false? - Solution True
- TE controls the amount of T2 decay that is allowed to occur before the signal is received.
What intentsity will a tissue that has a large transverse component of magnetization have compared to other tissues with smaller transverse components? - Solution High Generally speaking , the two extremes of contrast in MR are: - Solution Water and Fat What happens to the TR & TE in a gradient echo sequences as opposed to a spin echo sequence? - Solution TR & TE can be shorter How is the scan time affected in gradient echo sequences as compared to spin echo sequences? - Solution It is shorter - shorter TR=shorter scan time A disadvantage of gradient echo sequences is: - Solution There is no compensation for magnetic field inhomogenetics In gradient echo imaging what parameters control the amount of T weighting of the images? - Solution TE & Flip Angle In gradient echo imaging a short TR; a short TE & a large FA will produce what type of: - Solution T In a gradient echo imaging a fairly short TR a short TE & a small FA will produce what type of? - Solution PD In a gradient echo imaging a short TR, a Long TE & a small FA will produce what type of image? - Solution T2* Flow that is at a consistent velocity is known as: - Solution laminar flow Flow at different velocities that fluctuates randomly & changes drastically across the vessel is known as: - Solution Turbulent Flow First order motion refers to which type of flow: - Solution Laminar At nornal blood flow velocities , what type of flow will predominate? - Solution laminar
how does rapidly flowing blood appear on the spin echo MR image? - Solution Dark - rapidly flowing blood generates a signal void on SE scans In order to maintain the SNR of an image acquireed with a 256x256 matrix at 1 NEX. An image acquired using a 512x512 matrix would require a NEX of: - Solution 8 NEX - SNR is proportional to (squareroot of imaging time) 1x(pixelsize) SNR is proportional to the square root of the # of singal averages. If the # of signal averages is increased from 2 to 4 what is the increase in SNR? - Solution 0.6 - SNR=squareroot of 2=1. What three factors of a pulse sequence have an effect on the acquisition time? - Solution Matrix, TR, NSA The spatial resolution of an image depends on which of the following: - Solution Voxel size In order to have the optimum image quality , one should seek to have the highest SNR: This can be achieved by using a: - Solution Large FOV The difference in the SNR between two adjacent area's is known as the: - Solution contrast to noise ratio Which parameter would provide the better SNR? - Solution a)3mm slice, 256x128 b)3mm slice, 256x256 c)5mm slice, 512x512 d)5mm slice, 256x128: D What effect will increasing the TR have on SNR? - Solution Increase SNR What effect would increasing the TE have on the SNR? - Solution Decrease SNR Which of the following will produce the best SNR? - Solution 10mm slice, 256matrix, 24cm fov Which of the following will have the best SNR? - Solution 80TE, 2500TR, 12KHz bandwidth
Which of the following would provide the best SNR? - Solution a)512x512,5mmslice,48fov (b)512x256,5mmslice,24fov (c)256x256,5mmslice,24fov (d)256x128,5mmslice,40fov;;;;;(D) Which of the following would have the best SNR? - Solution a)2500TR,30TE,256x128 (b)2500TR,100TE,256x (c)1000TR,30TE,256x128 (d)1000TR,100TE,256x128 ;;;;(A) Which of the following would not be a result of reducing the receive bandwidth? - Solution Increase in the noise being sampled The matrix determines the # of pixel in the FOV. true or false? - Solution True In order to optimize image quality the SNR should be the highest possible. true or false? - Solution true Which of the following will have the best spatial resolution? - Solution a)3mmslice,512x384,40fov (b)3mmslice,512x192,24fov (c)3mmslice,256x256,24fov (d)3MMSLICE,512X256,40FOV;;;;;;;;;;(B) Which of the following would not be a result of increasing the NEX? - Solution increase in Voxel Size, NEX has nothing to do with voxel size. What would be the factor of increase in SNR if you increase the NEX from 2 to 4? - Solution 1. In order to maintain the SNR of an image acquired with a 24fov, 1 nex, an acquired with a fov would require a nex of? - Solution 2, If the fov is halved then the SNR is reduced by 1/4 of its original value. Which of the following would have the worst SNR? - Solution a)256x128,16fov,4mmslice (b)256x256,16fov,5mmslice (c)256x128,24fov,7mmslice (d)512x512,48fov,7mmslice;;;;(B) which of the following would have the worst spatial resolution? - Solution a)256x128,16fov,4mmslice (b)256x256,16fov,5mmslice (c)256x128,24fov,7mmslice (d)512x512,48fov,7mmslice;;;;;;(C)
Which of the following would have the shortest scantime? - Solution a)2500TR,256x256,4NEX (b)2500TR,256x256,2NEX (c)2500TR,512x512,1NEX,16etl (d)3000TR,256x256,1NEX,16etl;;;;;;;;(D) trxphasexnsa To increase resolution, the technologist should? - Solution Increase matrix, decrease slice thickness and FOV To increase SNR, the technologist could: - Solution Increase NEX Increasing the matrix will increase the SNR. true or false? - Solution False
- increasing matrix will decrese the SNR and increase the resolution Which of the follwoing parameters would have the best scantime? - Solution a)800tr,256x256,2nex (b)500tr,256x128,4nex (c)400tr,256x128,8nex (d)600tr,256x192,3nex;;;;;;(B) The size of the voxel is not affected by which of the following: - Solution NEX If a patient is not able to hold still for the scan the tech may decrease the scantime of the SE by: - Solution Decreasing the NEX If the NEX is doubled you will get a doubling of the SNR. true or false? - Solution false - snr increase with Square root of the NEX To obtain a high resolution image, Increase the matrix. true or false? - Solution true, What effect would decreasing the TR 2500 to 2000 have on the T weighting of an image? - Solution Decrease What would be the effect on contrast to noise ration of the following parameters: TR1500,TE80,256x256,16fov,3mmslice. - Solution Good CNR What effect will applying a steep slice select slope and/or narrow bandwidth have on the slice thickness? - Solution Slice will be thin
Which gradient axis in orthogonal plane imaging is used for sagittal or the axial body phase-encoding slice selection? - Solution Y Which gradient axis in orthogonal plane imaging is used for axial head or coronal phase-encoding slice selection? - Solution X Which gradient axis in orthogonal plane imaging is used for axial head Phase-encoding? - Solution X Which gradient axis in orthogonal plane imaging is used for axial head frequency-encoding? - Solution Y Which gradient axis in orthogonal plane imaging is used for sagittal & coronal frequency-encoding? - Solution Z Which gradient performs the task of slice selection within the scan plane selected? - Solution Slice selection Which gradient performs the task of spatially locating slice along the long axis of the anatomy? - Solution Frequency encoding Which gradient performs the task of spatially locating slice along the short axis of the anatomy? - Solution Phase encoding (short axis) Another name for the frequency encoding gradient is: - Solution Readout gradient How is scantime reduced in fast spin-echo? - Solution By performing more than one phase encoding step per TR. The maximuum # of slices that can be selected & encoded depends on the length of the: - Solution TR In 2D fourier transformation imaging, the strength of the phase encoding gradient is different in each cycle. true or false? - Solution True In 3D fourier transformation the signals are collected from an entire imaging volume? true or false? - Solution True, Nx,Ny,Nz
The slope of the gradient determines the size of the phase shift. What type of phase encoding gradient slope is need to produce a large difference between 2 points? - Solution Steep. ---Steep slopes produce large phase encoding. An efficient technique used by an MR system to create the 2D & 3D images is known as: - Solution Fourier Transformation The acquired data held in K-space is converted into an image by a process known as the: - Solution Fast Fourier Transformation (FFT) By selecting the phase encodinh direction correctly one can minimize the overlap of the artifact & organs of interest. true or false? - Solution True frequency encoding in sagittal spine imaging is usually oriented along the long axis of the spine to reduce? - Solution Aliasing (wrap) One of the big problems with using RF receive only small FOV coils in the knee imaging is: - Solution Aliasing On Liver images ghosting artifacts caused from the bowel anterior to the liver can be decreased by: - Solution Placing phase encoding direction RT to LT Motion causes degradation of the MR images as: - Solution ghost like artifacts, reduced intensity of ,moving structures, blurring or un-sharpness, all of the above Motion artifacts that may occur with images of the lumbar spine includes: - Solution Respiration, abdominal peristalsis, vascular phase-shifts, all of the above Patients with Swanz Ganz catheters should not undergo MR procedure because: - Solution Eddy current inductive heating may melt the catheter Ghosting artifacts always occur in the: - Solution Phase encoding direction To compensate for the ghosting artifact one should: - Solution change phase direction, use pre-saturation band, use respiratory compensation or breath hold technique
Eddy currents cannot be minimized with active gradient shielding. true or false? - Solution false Which of the following would produce a gibbs artifact in a T1 weighted image? - Solution 256x128. undersmapling of data in phase direction Truncation artifact on T1 weighted spinal cord imaging maybe falsely interpreted as: - Solution A syrinx Gibbs artifact or truncation artifact happens when: - Solution Undersampling of the data occurs What is the image artifact that results from partial excitation of a slice of tissue as data from an a adjacent slice is acquired? - Solution Cross talk An example of a patient & or tissue dependent artifact is: - Solution Metal artifact A zipper artifact is caused by which of the following: - Solution RF leak A zipper will occur in which direction? - Solution Frequency An artifact due to contamination of the MR signal by transient signal from tissues that are located outside of the slice is called: - Solution Zipper What is the name given to the substances that "bind" to the gadolinium ions? - Solution Chelates Some of the newer gadolinium agents are non-ionic. How do they differ from ionic? - Solution They possess a lesser tendency for release of the toxic gadolinium atom. What is the contraindication for using gadolinium contrast agents? - Solution Sickle cell, hemolytic anemia, pregnancy patients are contraindicated What is the excretion rate for gadolinium in healthy patients? - Solution 80% excreted by the kidneys in 3 hours
what is a clinical indication in the central nervous system for the use of gadolinium? - Solution Tumors & infection post operative disc & post radiotherapy Which of the following brain tissues demonstrate normal post gadolinium enhancement: - Solution Pituitary gland In the brain, what has signal on short TR & short TE images & mimics enhancement with the use of gadolinium? - Solution Cavernous sinuses, areas with slow flowing blood such as the cavernous sinus & the venous drainage system may mimic ehancement Gadolinium chelates are: - Solution Paramagentic Gadolinium enhances intra-axial lesions associated with disruption of the blood brain barrier such as: - Solution Gliomas, metastases, abscesses The most commonly noted reaction to intravenous administration of gadolinium chelates is: - Solution Headaches Breast feeding for women who have received intravenous gadolinium contrast should be suspended for: - Solution 2 days One disadvantage of intravenous contrast agents in MR is the increase in flow motion artifacts. true or false? - Solution True An intravenous paramagnetic contrast agent ______________ the T relaxation time of tissue? - Solution Shortens An intravenous paramagnetic contrast agent ____________ the intact blood brain barrier. - Solution Does not cross If the parameters selected for an imaging sequence will expose the patient to specific absorption rate levels in excess of the FOA defined level of concern. They should never be employed on patients who are: - Solution Febrile The FDA defines the SAR to be below the level of concern at: - Solution Less that or equal to 0.4W/Kg averaged over the body
