ARRT Principles of MRI Final Exam Review Questions with 100% Correct Answers | Updated & Verified | 2024

Document Content and Description Below

3D gradient echo axial views can be used in cervical spine imaging to provide - ✔✔Thin, contiguous sections of the spine, the ability to reformat into any other imaging plane, retrospectively, th... e ability to get either T1, spin density or T2* information by changing parameters. In complete spine imaging, to rule out metastatic lesions of the spinal cord, contrast enhancement can be used with T1 weighted images because - ✔✔metastatic lesions enhance and normal cord does not Due to the differences in frequencies across the magnetic field we - ✔✔use gradients, use sat bands, . use different coils To avoid the "magic angle" (an artifactual brightness seen in the medial segment of the posterior horn of the lateral meniscus when short TEs are used) artifact when imaging the knee, - ✔✔use a longer TE, reposition the knee, orient the affected anatomy to another angle To best visualize the anterior cruciate ligament on knee MR - ✔✔externally rotate the leg about 15 When using MRA to evaluate intracranial vascularity, flow within smaller vessels can best be demonstrated by - ✔✔3D time of flight MRA or 3D phase contrast MRA To produce the echo, a gradient echo pulse sequence uses - ✔✔a gradient magnetic field onlyThe rate of dephasing due to inhomogeneities is called - ✔✔T2 inhomogeneity If the TR of a gradient echo pulse sequence is considerably less than the T2 (and T2*), the condition that will exist is known as - ✔✔steady state The gradient that is on during the production of the echo is the __________ encoding gradient - ✔✔frequency The gradient that is on longest is the __________ encoding gradient - ✔✔frequency The four phases of a spin echo pulse sequence, in correct order, are - ✔✔Excitation, encoding, refocusing, readout. Using an NSA of 3, if a phase resolution of 192 is desired, then the TR must be repeated - ✔✔576 times In a fast spin echo sequence, the effective TE is the echo that is performed with the - ✔✔Low amplitude phase encoding gradient. In a 2D multiecho pulse sequence, ETL = 8, scan time is given by the equation TR x - ✔✔Number of signals averaged x number of phase encodings / the number of echoes. When using MRA to evaluate extracranial vascular flow, such as that within common carotid arteries, a recommended technique is - ✔✔2D time of flight MRAWhen using bright blood MRA to evaluate peripheral vascular flow, such as that within the arteries of the legs, saturation pulses are - ✔✔placed inferior to the acquired slices In a 3D acquisition, the slices are produced by - ✔✔A phase encoding gradient applied in the slice direction. Acquired by volume imaging. To create a projection image in MRA, the technique MOST commonly employed is - ✔✔19. maximum intensity pixel If a given conventional spin echo pulse sequence takes 12 minutes to acquire, a multiecho sequence, using a 6 echo train, with all factors that affect scan time remaining the same, will take ________________ to acquire the same images - ✔✔2 minutes Gadolinium chelates are - ✔✔Paramagnetic. Acquiring half the phase views of k space and then calculating the data for the other half is a technique known as - ✔✔partial Fourier The MRA sequence that is more sensitive to slow flow is - ✔✔2D time of flight A major advantage of MRA over conventional angiography is that - ✔✔2D time of flight The removal of signal from vessels in an MRA sequence is achieved by - ✔✔spatial presaturationIn a spin echo sequence, flowing blood is normally seen as a signal void because - ✔✔the 90o pulse and the 180o pulse are both slice selective In a time of flight sequence, the tissue is hypointense relative to flowing blood because of - ✔✔saturation effects Phase contrast techniques produce image in which the signal intensity within the vessel is dependent on (among other parameters) the - ✔✔velocity of the flowing blood A major advantage of 3D time of flight techniques over 2D time of flight is the ability to - ✔✔visualize smaller vessels A major advantage of a 2D time of flight sequence over a 3D time of flight is the ability to - ✔✔image a larger area without saturation of the flowing blood. The presaturation pulses usually occur - ✔✔prior to the excitation pulse The time during which the frequency encoding gradient is on __________________ a reduction in receiver bandwidth - ✔✔increases with If a STIR sequence using a TR of 3000, a TE of 20, and a TI of 140 in a 1.5 T imager, produces an image with dark fat and bright water. The contrast in such an image is primarily based on - ✔✔T2 weighted Cardiac cine acquisitions typically utilize a / an __________________ pulse sequence. - ✔✔T1When triggering a scan from the patient's EKG, the TR of the sequence is determined by the - ✔✔patient's heart rate The liquid cryogen (s) commonly used to maintain the primary magnet coil at superconducting temperature is / are - ✔✔helium The type of RF coil configuration that uses a pair of coils perpendicular to each other to transmit and receive signal is known as a ______________________ coil. - ✔✔quadrature Which coil has a characteristic drop off of signal beyond the physical edge of the coil? - ✔✔surface In an MRI system that uses shim coils, B0 homogeneity is adjusted by - ✔✔changing current in the shim coil Isotopes are a product of - ✔✔fewer neutrons than protons The time it takes for a tissue's bulk longitudinal magnetization to return to 63% of its original value, following excitation, is known as - ✔✔T1 The time it takes for transverse magnetization to decay to 37% of its original value, following excitation, is known as - ✔✔T2* This is describe as movement of molecules in the extra cellular space - ✔✔diffusion imagingDWI sequences are being tested for use in what? - ✔✔characterizing liver lesion, imaging the left ventricle, imaging skeletal muscle injuries Interventional MRI is used for. - ✔✔imaging skeletal muscle injuries Calculate the pixel area for the following seuqence: TR 4000 TE 120 FOV 36 cm MATRIX 408 x 512 NEX 2 ETL 12 - ✔✔Formula: (FOV / MATRIX) x (FOV / MATRIX) = ____ mm (*remember to convert FOV from cm to mm by multiplying it by 10) (360/480) x (360/512) .075 x .0703 = ANSWER: .62MM Calculate imaging time for a patient with a heart rate of 90 b/min, trigger window 15% and trigger delay of 80ms. - ✔✔Formula: TR - (trigger + delay)1. Calculate TR (formula - 60,000 / b/mn = TR) 60,000 / 90 = 666 TR 2. Calculate trigger (formula - TR x trigger window %) 666 x 15% = 100 3. Imaging Time = TR - (trigger + delay) 666 - (100+80) 666 - 180 = 486 ms Chemical shift occurs primarily along which axis? - ✔✔frequency ________ is more susceptible to metallic artifacts due to the lack of the 180 refocusing pulse that would reduce field inhomogeneities - ✔✔Gradient echo To minimize CSF flow artifacts on a cervical spine, what type of sequence could be used? - ✔✔gradient moment nullingArtifact that occurs in the phase direction and is caused by anatomy outside the FOV. Is under sampled, causing a misregistration, resulting in what is commonly called wrap around is what type of artifact? - ✔✔aliasing What is a Gibb's artifact? - ✔✔Gibbs artifacts (also known as truncation, ringing, or spectral leakage artifacts) typically appear as multiple fine parallel lines immediately adjacent to high-contrast interfaces. These artifacts are particularly problematic in spinal imaging, in which they may artifactually widen or narrow the cord or mimic a syrinx. How can we correct for a Gibb's artifact? - ✔✔Increase number of phase encodings or decrease FOV Fat and water precess at different frequencies, causing a _________ artifact. - ✔✔chemical shift What can be done to the receiver bandwidth to compensate for chemical shift? - ✔✔Increase receiver bandwidth Artifacts from motion will appear in which direction? - ✔✔Phase encoding direction Energy given to nuclei in adjacent slices due to spin lattice relaxation can cause adjacent slices in an acquisition to have different image contrast. What type of artifact is this? - ✔✔Cross Talk An artifact seen in a GRADIENT ECHO image that appears as black and white banding on the edges of the FOV - ✔✔MoireDiseases, such as Malaria, in which microorganisms are transferred via an insect are classified as - ✔✔vector borne A complication or illness caused by the treatment from a healthcare professional is termed - ✔✔latrogenic In a medical malpractice lawsuit, the ____ must be able to prove medical malpractice - ✔✔plaintiff / patient During transport of the patient, the urinary collection bag should be placed - ✔✔below the bladder The stray magnetic field outside the bore of the magnet is termed - ✔✔fringe field FDA revision in 2003 on RF absorption limits the absorption to ______ for the head - ✔✔3 w/kg - 10 min Which of the following has been documented to cause muscle contractions, alterations in vision and biochemistry of cells? - ✔✔time varying magnetic fields What is the RF absorption limit for the whole body based off the 2003 FDA revision? - ✔✔4 w/kg - 15 min When a sudden loss in temperature occurs which causes the coils to no longer be superconducting, resulting in helium escaping from the cryogenic bath is termed: - ✔✔a quenchForce of an object in a magnetic environment depends on the following: - ✔✔mass of the object, strength of the magnet, ferromagnetic properties of the object The medial and lateral rectus muscles are located where? - ✔✔The eye The first major branch of the abdominal aorta is the: - ✔✔celiac trunk The largest ventricle in the heart - ✔✔left ventricle In what plane would a tear of the collateral ligaments of the knee be best evaluated? - ✔✔coronal The ______ valve lies between the left atrium and left ventricle - ✔✔bicuspid / mitral Which fissure divides the frontal lobe from the temporal lobes? - ✔✔Sylvian The common carotid bifurcates into the internal and external carotid artery at the level of ______ - ✔✔C3 / C4 What three branches come off the aorta? - ✔✔brachiocephalic, left subclavian, left carotid Which veins transport oxygenated blood? - ✔✔pulmonary Which valve lies between the right atrium and right ventricle? - ✔✔tricuspidWater has a ______ T1 relaxation time and a _______ T2 relaxation time - ✔✔long / long The transmit bandwidth of the RF pulse effects: - ✔✔spatial resolution, SNR, slice thickness The process the digitizes the MR signal is known as: - ✔✔Fourier / Fast Fourier Reducing the TE results in images with what change in contrast? - ✔✔decreased T2 information The phase encoding step is performed prior to the ________ step - ✔✔frequency encoding What element in the body is the principle nucleus used in MR? - ✔✔hydrogen In a super conducting magnet, the magnetic field strength is increased by increasing the - ✔✔# of turns in the wires Which parameter adjustments would shorten scan time? - ✔✔Decrease TR Increase echo train length Decrease NEX Reducing the FOV will result in - ✔✔decreased SNR How can thin slices be selected? - ✔✔Steep slice gradientnarrow bandwidth All the following result in increased SNR - ✔✔Parameter adjustments that increase SNR are: Increase TR Reduce phase matrix Increase FOV Reduce receiver bandwidth Increase NEX The readout gradient is turned on during the sampling or readout of the peak echo and also during which other process? - ✔✔frequency encoding Reducing the number of lines filled in K space will produce an image with: - ✔✔decreased spatial resolution increased SNR Decreased scan time Reducing scan time can be achieved by: - ✔✔reducing TR reducing NEX using half fourier using a course matrix increased parallel imaging factorWhich will lengthen scan time in a pulse sequence: - ✔✔increase TR decrease echo train length increase NEX decrease parallel imaging factor Reducing FOV by a factor of 2 will reduce the voxel volume by a factor of _____ - ✔✔4 If the desire is to null the signal from a specific tissue using an IR sequence, the TI selected should be _____% of the T1 relaxation time - ✔✔69% Reducing the flip angle will result in images with what change in contrast? - ✔✔Less T1 Which protocol would be used to rule out islet tumors? - ✔✔pancreas How would you best describe EPI (echo planar imaging) sequences? - ✔✔a train of gradient echoes In fast spin echo, the number of shots is calculated by what? - ✔✔The # of phase encodings and echo train length Hemangiomas of the liver are best visualized with: - ✔✔contrast enhanced study with delayed images What best describes an inversion recovery sequence? - ✔✔180 degree pulse followed by a combination of 90 degree and 180 degree pulsesDescribe FSE - ✔✔a train of spin echoes The gradient slew rate is: - ✔✔the rate of speed of descent to ascent of a gradient from zero to maximum STIR sequences are typically used to evaluate: - ✔✔fat suppression lesions within retro-orbital fat muskuloskeletal contusions compression fractures Magnetic susceptibility artifacts are more prominent with ______ sequences - ✔✔gradient echo A gradient echo sequence in which all the remaining residual transverse magnetization is removed prior to the next excitation pulse is - ✔✔incoherent/spoiled If a patient has a history of back surgery with hardware that is MR safe, which sequence should NOT be used - ✔✔Gradient echo Coherent gradient echo pulse sequences usually produce rapid images that are _____ weighted - ✔✔T2* A STIR sequence with a T1 time of 160 ms will null signal from fat at what field strength? - ✔✔1.5 tT2 weighted FLAIR are typically used for evaluation of what? - ✔✔white matter diseases When imaging a hemorrhagic infarct in the brain, which pulse seuqence would best demonstrate the magnetic susceptibility effects? - ✔✔gradient echo CSF suppression is performed with what sequence? - ✔✔FLAIR Which sequence is most INSENSITIVE to magnetic field inhomogeneity? - ✔✔SPIN ECHO When scanning a patient with chiari malformation, which would be the best imaging plane? - ✔✔saggital Fat has a ______ T1 relaxation time and a ______ T2 relaxation time - ✔✔short / short When performing images of the brain to rule out a brain tumor, what images would be acquired post gad? - ✔✔T1 To visualize arterial flow during an MRA study of arterial flow, where should pre-saturation pulse be applied to remove signal from venous flow? - ✔✔superior to the slice stack During a study for venout flow, where should the pre saturation pulse to applied to remove signal from arterial flow? - ✔✔Inferior to the slice stack How does a double IR prep sequence begin - ✔✔two 180 degree RF pulsesWhich is the best sequence to use to evaluate a patient with MS? - ✔✔T2 FLAIR Which gradient echo sequence will give us TRUE T2? - ✔✔SSFP (steady state free precession) As the number of phase encodings increase from 250 to 500, the SNR will _______ - ✔✔decrease (less protons per voxel) Choose the correct slice thickness to create an isotropic voxel for the following: TR2000 TE 90 matrix 272 x 272 FOV 24cm - ✔✔Formula: FOV / matrix *remember to convert FOV from cm to mm by multiplying it by 10 240 / 272 = .88235 .88 slice thickness What would the scan time be in a 3D volume acquisiton as this: TR 24ms TE 7ms Flip angle 15 degreesFOV 20cm 2mm slice thickness 76 slices 176 x 256 matrix 1 NEX - ✔✔Formula: TR x Phase matrix x NEX x # slices 24 x 176 x 1 x 76 = 321024 * next step, divide by 60,000 321024 / 60000 = 5.35 5 min / 35 sec In a FSE, what would scan time be for: 25cm FOV 224 x 320 matrix TR 2500 100 TE 3mm slice thickness 12 ETL 4 NEX - ✔✔Formula: TR x Phase Matrix x NEX / ETL 2500 x 224 x 4 = 22400002240000 / 12 = 186666 *next, divide answer by 1000 to convert ms into sec 186.66 *next, divide by 60 to get mins and secs 3 min, 11 sec. [Show More]

Last updated: 10 months ago

Preview 4 out of 18 pages