image formation Flashcards
a ____ is defined as a picture element and has _____ characteristics
pixel, two dimensional
if the radiologist requires 3mm slices axially acquired through the IAC with a slice gap of .5mm and requires 4.2 cm total coverage, how many slices must be selected?
12
anatomic slice coverage: slice thickness + interslice gap x # of slices
if 24 4 mm slices are planned with a gap of 1 mm the total anatomic coverage is ____cm
12
24 slices x 5 mm (4thickness + 1 gap)= 120; divide by 10 to calculate the coverage in cm
the signal produced immediately following the rf pulse is
FID
_______is defined as a small change in the magnetic field along a particular axis
a gradient
_______is a file on the computer where the collected echoes are stored prior to being processed into an image by the fourier transform
raw data
which factors affect the flip angle
strength and duration of the rf field
to obtain a then slice thickness
a steep gradient is applied with the transmit bandwidth at the larmor frequency of H
when gradient moment nulling is used as an imaging option in MR sequences
the minimum TE is increased
gradient moment nummling is used to compensate for
first order motion and slow flowing vessels
as the TR is increase
SNR is increased, available number of slices is increased
in a gradient echo reducing the flip angle while maintaining the TR reduces
saturation
complete saturation is a condition where
longitudinal magnetization is not allowed to recover between excitations
gradient echos use flip angles
to control saturation effects
decreasing the rBandwidth
decreases the number of slices available
