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ELT-64206 Magnetic Resonance and Ultrasound Imaging
Hannu Eskola

Examination, May 5th, 2014 Use of non-programmable calculator accepted

1. Principle of ultrasound imaging. Answer shortly to these duestions:
a) Which properties of the tissue produce the tissue contrast?
b) Which parameters of the crystal affect the length of the near field?
c) Which ultrasound imaging modes are used for studying the valves and blood flow in the
heart?

2. Doppler ultrasound imaging.
a) In which direction the information is obtainable?
b) How are the colors and the greyscale coded in a Doppler image?
c) Whatis the effect of the position of the beam in the transducer to the measured velocity?

a) Whatis the difference between Spin echo and Gradient echo imaging seguences?
b) What are the advantages and drawbacks of these methods?

a) Whatis the basis of diffusion imaging?
b) Whatis fractional anisotropy (FA)?
c) What is expressed by tractography?

5. A patient with mild traumatic brain injury is be examined with a 3T MRI scanner using
Fast Spin Echo seguence (FSE).
a) What percentage of proton spins (in the brain) will align against the field at a
body temperature of 36.5 *C?
b) If the interested brain tissues haveaT 1 relaxation time of 900 ms, caleulate how long
will it last for the Z-magnetization M, to recover 95% of its eguilibrium value?

Boltzmann constant = 1.3806488 x 10 m? kgs?K"
Planck's constant = 6.62606957 x 10% m? kg/s
Gyrometric ratio for proton = 42.57 MHz/T