magnetism Flashcards
what type of magnet is used with most mri systems currently manufactured?
superconducting
the precessional frequency of hydrogen according to the larmor equation at 3T is
127.71MHz
what substance is noferromagnetic
gold
the first documented human mr image was obtained on a 15MHz rf system what field strength did it operate at?
.352 T
The RF fiels oscillates at the
larmor frequency
what is defined as the excess number of hydrogen protons aligned with the static magnetic field direction(b0)
longitudinal magnetization
_______ is a ferrous substance
iron
if the rf energy transmitted is _ MHz the slice through the pt would be in a magnetic field of .995T
42.36
___________ magnets can be shut off the quickest in case of an emergency
resistive
the ____ is defined as the resonant frequency and is equal to the product of the magnetic field and the gyromagnetic ratio
processional frequency
hydrogen is used in mr imaging bc
of its abundance in the body
hydrogen protons in the anti parallel state are referred to as
spin down and high energy spins
immediately following the application of the 90 degree rf pulse the transverse magnetization is
non zero
in one t2 relaxtion time
63% of the transverse magnetization had decayed
in one t1 relaxation time
63% of the longitudinal magnetization has recovered
