Читать книгу Essentials of MRI Safety - Donald W. McRobbie - Страница 47

1 The Larmor frequency of a 1.5 T MRI scanner is approximately:10 MHz42.58 MHz64 MHz85 MHz128 MHz

2 In a 1.5 T MRI scanner, if the B1+ amplitude required to produce a 90° flip angle is 10 μT, what B1+ amplitude is required in a 3T scanner if the pulse shape is unchanged?5 μT10 μT20 μT40 μT0.01 mT

3 Which of the following is true for B1?It is applied along the z‐direction along the magnet boreIt is a single sinusoidIt is a radio waveIt is generated by the x and y gradient coilsIt rotates with the magnetization precession.

4 Which of the following is untrue for the static field spatial gradient in a superconducting MRI system?It is measured in tesla per meterIt is required for image acquisitionIt is always presentIt is responsible for the translational magnetic forceIt is reduced in extent in a self‐shielded magnet.

5 If an imaging gradient system has a peak amplitude of 50 mT m−1 and a slew rate of 200 T m−1 s−1 what is the minimum achievable rise time for a full amplitude pulse?10 μs0.1 ms0.2 ms0.25 ms0.4 ms

6 Which of the following is not acceptable terminology for MR safety according to ASTM‐F2503?MR safeMR unsafeMR compatibleMR conditionalMR acceptable.