ARRT PRINCIPLES OF MRI FINAL EXAM 2023.

ARRT PRINCIPLES OF MRI FINAL EXAM 2023. 3D gradient echo axial views can be used in cervical spine imaging to provide - ANSWER Thin, contiguous sections of the spine, the ability to reformat into any other imaging plane, retrospectively, the 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 - ANSWER metastatic lesions enhance and normal cord does not Due to the differences in frequencies across the magnetic field we - ANSWER 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, - ANSWER use a longer TE, reposition the knee, orient the affected anatomy to another angle To best visualize the anterior cruciate ligament on knee MR - ANSWER externally rotate the leg about 15 When using MRA to evaluate intracranial vascularity, flow within smaller vessels can best be demonstrated by - ANSWER 3D time of flight MRA or 3D phase contrast MRA To produce the echo, a gradient echo pulse sequence uses - ANSWER a gradient magnetic field only The rate of dephasing due to inhomogeneities is called - ANSWER 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 - ANSWER steady state The gradient that is on during the production of the echo is the __________ encoding gradient - ANSWER frequency The gradient that is on longest is the __________ encoding gradient - ANSWER frequency The four phases of a spin echo pulse sequence, in correct order, are - ANSWER Excitation, encoding, refocusing, readout.