MRI PHYSICS FINAL PRACTICE EXAM WITH CORRECT ANSWERS 100% VERIFIED.

Nuclei that have the strongest magnetic moments are those with - correct answer only hydrogen The Larmor frequency of nuclei depends on: - correct answer # of protons and neutrons in the nucleus gyromagnetic ratio main magnetic field strength molecule in which nuclei are located The spin-lattice relaxation time in MRI is also called the - correct answer longitudinal relaxation time The shortest relaxation time in MRI is the - correct answer t2* The coil that provides the best signal to noise ratio is the - correct answer surface coil The relaxation time that controls the FID is the - correct answer t2* Cryogenic superconductive magnets have their electrical windings cooled by - correct answer liquid helium The Larmor frequency of hydrogen nuclei at 1.5T is about - correct answer 63.9 MHz The brightest signal from a T2- weighted spin echo MRI image would be from - correct answer pure water (3000 ms) The brightest signal from a T1- weighted spin echo MRI image would be from - correct answer adipose tissue (180 ms) A T1 weighted spin echo image is produced by using a pulse sequence with ________ TE time and a ______ TR time. - correct answer short, short A T2 weighted spin echo image is produced by using a pulse sequence with ______ TE time and a _______ TR time. - correct answer long, long A proton density weighted spin echo image is produced by using a pulse sequence with ______ TE time and a _______ TR time. - correct answer short, long The pulse sequence most often used to nullify the signal from adipose tissue is - correct answer STIR The fastest MRI pulse sequence is - correct answer echo planner Name all the ways you can improve the SNR for a spin echo image. - correct answer Thick slice More NEX Greater magnet strength Larger pixel size The 180 degree-90 degree- 180 degree RF pulse sequence is employed in - correct answer inversion recovery The reconstruction technique used for most MRI image is - correct answer 2DFT As the magnetic field strength increases, the ____________ parameter also increases - correct answer T1 The scan time for a spin echo pulse sequence depends on all of the following: - correct answer NEX TR # of phase encodings Use of Fourier symmetry The spatial resolution in body MRI images is about - correct answer 0.7 LP/mm In MRI, ______ gradient is on when the RF is applied - correct answer slice selection gradient _______________ MRI artifacts are repeated low- intensity images in the phase-encoding direction - correct answer Motion ghost _____________ MRI artifacts cause images wrap around to the opposite side and overlap other parts of the anatomy. - correct answer Aliasing ____________ MRI artifacts displace fat and tissue to create voids and bright areas of overlap in the frequency- encoding direction of units with large field strength. - correct answer chemical shift ________________ artifacts cause voids and distortions near air -tissue interfaces - correct answer Susceptibility Fringe fields from MRI units must be less than _________ gauss in areas where individuals with pacemakers, biostimulators, insulin infusers, and other similar biologic electronic devices have unrestricted access. - correct answer 5.0 gauss Tissue heating from MRI RF signals should be such that SAR does not deposit more than ______ watts/ kg averaged over the body of the patient. - correct answer 4.0 watts/kg In MRI, ______ gradient is on during the time applied between the RF pulse and the echo. - correct answer phase encoding gradient The MRI pulse sequence that is most likely to cause the most RF heating in the patient's tissue is - correct answer fast spin echo In MRI, which of the following statements is true regarding the function of RF coils? A. the same coil may be used to transmit the RF pulses and to receive the MR echoes. B. separate coil may be used to transmit the RF pulses and to receive the MR echoes. C. the surface coil would be optimal for imaging structures deep within the brain D. they digitize the received echoes E. A and B - correct answer E. A and B Which one of the following is NOT characteristic of superconducting magnets? A. Requires the use of cryogen B. Shuts off as soon as the electrical current supply to its windings is stopped C. Available in clinical systems to produce a magnetic field of 1.5 Tesla D. Uses electrical current running through the wire that has no electrical resistance when kept cold E. Often used in mobile MRI settings - correct answer B. In MRI, ______ gradient is on during the time the echo is measured. - correct answer frequency encoding After collecting an echo from one slice, what must the MR system do in order to collect an echo from the next adjacent slice. - correct answer Increase of decrease the center frequency at which the RF energy is transmitted. In an NMR spectrum, the field homogeneity can assessed by measuring the: - correct answer line width of a single peak The dominant artifact affecting image quality most often in the phase encodi