Armrit stuvia Study guides, Class notes & Summaries

For the following spin-echo protocol: FOV: 320/ TR:500/ TE:25/ SliceThick.:5mm/ Slice Gap:1mm/ Slice.#:9/ NEX:4, Matrix:192 Decreasing TE will: a. Decrease the # of allowable slices. b. Increase the # of allowable slices. c. Increase scan time. d. Decrease scan time. - Answer b. Increase the # of allowable slices. A linear relationship between frequency and position is superimposed on Bo by the Gp. The H protons' relative precessional frequencies determine: a. Phase coherence. b. Pha...

Signal - Answer Current induced iby receiver coil. Also comes from the procession of protons in the patient. Chemical pre saturation - Answer Selectively apply 90 degree pulse at frequency of tissue to be saturated. Moves fat or HBO 90 degrees. 2nd puse wider bandwidth moves both fat and water 90 degrees. One will be saturated so will not be read. Saturating out normal anatomy, pathology is often seen more clearly. NEX number of excitations - Answer is the number of times each line is fill...

The tissue characteristic that depends heavily on the relative content of fat molecules and free water is: - ANSWER-Hydrogen concentration. T1 is the measurement of time for the longitudinal component of the net magnetization vector to recover what percentage of its original value after the application of a 90 degree radio-frequency pulse? - ANSWER-63% Immediately after an initial 90 degree radio-frequency pulse is turned off, the hydrogen protons will begin to: - ANSWER-Dephase A 90 de...

An analogy for the decoding of the MR signal through Fourier Transform - ANSWER-Basilar membrane processing sound Logically each line of phase encoding data is combined to allow the FT to determine the position along the y-axis. The number of phase encoding steps determines - ANSWER-the number of pixels along the y-axis In a gradient echo pulse sequence, which flip angle will produce a T2 weighted gradient echo image. - ANSWER->20 - <45 degree flip angle In a horizontal magnet, wh...

The exact middle of the bore of the magnet is termed: - ANSWER-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: - ANSWER-Including electrical current in the patient's tissues Faraday's Law deals with induction of a current by a magnet. true or false? - ANSWER-true The orientation of the main magnetic field of a low field permanent magnet is verti...

ARMRIT - Practice Test (Part 3: MRI Safety) with Complete SolutionsARMRIT - Practice Test (Part 3: MRI Safety) with Complete SolutionsARMRIT - Practice Test (Part 3: MRI Safety) with Complete Solutions The factor which determines the calculated SAR average is: - ANSWER-The Patient weight in kilograms The maximum exposure to the head and trunk from the main magnetic field (Bo) is: - ANSWER-3T

Chemical pre saturation - ANSWER-Selectively apply 90 degree pulse at frequency of tissue to be saturated. Moves fat or HBO 90 degrees. 2nd puse wider bandwidth moves both fat and water 90 degrees. One will be saturated so will not be read. Saturating out normal anatomy, pathology is often seen more clearly. NEX number of excitations - ANSWER-is the number of times each line is filled with the data in K space, the number of times and echo is encoded with the same slope of phase encoding gradi...

different tissues that have signals that appear similar on a mr image are described as: - ANSWER-isointense In a large main magnetic field such as those employed in MRI, the motion of a hydrogen proton has been described as wobbling like a spinning top. This motion is called: - ANSWER-Prescession Magnetic resonance imaging is derived from the process known as: - ANSWER-Nuclear magnetic resonance Once the net magnetization vector (nmv) has moved away from equilibrium, the following will ...

For the following spin-echo protocol: FOV: 320/ TR:500/ TE:25/ SliceThick.:5mm/ Slice Gap:1mm/ Slice.#:9/ NEX:4, Matrix:192 Increasing the FOV will: a. Increase SNR. b. Decrease SNR. c. Decrease Matrix. - ANSWER-a. Increase SNR A gradient is employed exposing the patient's body to a series of increasing or decreasing magnetic field strengths for slice selection. In what relation to the slice is this gradient? a. Anti-parallel. b. Perpendicular. c. Parallel. d. Oblique. - ANSWER-b. P...

The tissue characteristic that depends heavily on the relative content of fat molecules and free water is: - Answer Hydrogen concentration. T1 is the measurement of time for the longitudinal component of the net magnetization vector to recover what percentage of its original value after the application of a 90 degree radio-frequency pulse? - Answer 63% Immediately after an initial 90 degree radio-frequency pulse is turned off, the hydrogen protons will begin to: - Answer Dephase A 90 de...