MRI Hardware, History and Magnetism Flashcards
Gadolinium contrast gets first approval by FDA in what year?
1988!!
How does Gad function as a contrast agent?
it SHORTENS the t1 time of tissue
The substances that bind to gadolinium ions are defined as
Chelates
Gadolinium chelates used in MR imaging are :
diamagnetic or paramagnetic?
paramagnetic
Gadolinium has ___ unpaired electrons?
7
Gadolinium makes bowel appear T1 and T2 Hypointense
True or False
True
an anti-peristalsis agent in MR Enterography procedures.
Glucagon
How come when we use contrast, a metastatic lesion will enhance?
has to do with the breakdown in the blood brain barrier
What is the standard dose of gadolinium?
0.1 mmol/KG (pay attention, must be in KG)
Following the administration of IV gadolinium contrast, it is recommended to:
Follow the injection with a flush of 5 mL saline
VoLumen is a contrast agent used for
bowel enhancement
The location of the coils installed in the MRI scanner, from the inner point closest
to the patient to the outer most edge are :
shim coils, main magnet, RF coils and gradient coils..what order?
RF radiofrequency coils, gradient coils,
shim coils, main magnet
the time it takes for the gradient to reach its full amplitude is called
gradient rise time
think about the time it takes for you to fully stand up/rise up??
What rise time measured in?
microseconds “mT/m (millitestla / meter)
s the speed rate of ascent or descent of a gradient from
zero to its maximum amplitude, either positive or negative
the gradient slew rate
How do we calculate the gradient slew rate
it is the amplitude divided by the rise time in msec.
the time the gradients are on during a TR period, the
“gradient working time.”
duty cycle
What is the primary cause of the noise in the MRI room?
the rapid successive switching of gradient coils
If a sagittal slice plane has been selected, the ___ gradient is enabled to alter the
magnetic field around the patient’s body.
x y or z
x
If a coronal slice plane has been selected, the __ gradient is enabled to alter the
magnetic field around the patient’s body.
x y or z
Y
If a axial slice plane has been selected, the ___ gradient is enabled to alter the
magnetic field around the patient’s body.
z
Applying two gradients simultaneously during slice selection would produce an
____ slice
oblique
what is an example of when we do a “oblique” slice?
YX gradient combination in a coronal
oblique of the shoulder, parallel to the supraspinatus tendon
In a cross sectional view of MRI system coils, the RF coils are closest to the patient.
True or False?
true
Why is a fast spin echo the most concerning in regards to RF heating?
it has multiple echo train lengths leading to potential increase in tissue heating.
What is the SAR measured in?
watts / kg
Larger patient = increased or decrease SAR??
large patient = increased SAR
When going from a linear coil to a quadrature coil, SNR is increased by ___ %?
40 , 60 , 80
40
Radiofrequency (RF) shielding can be achieved by lining the scanner room walls
with copper.
True or False
True
doubling the magnetic field strength will double the SNR
True
What is the ideal consistent room temp that the MRI scanning room should be?
65-75 with humidity of 50-70%
what is a positive to using the body coil?
the large FOV capability, but it lacks the high SNR.
The MRI system component that produces the magnetization of proton spins
(alignment) is known as the
main magnet or the gradient system?
main magnet
The MRI system component that provides the ability to perform spatial
encoding is the
main magnet or gradient system?
gradient system
The liquid cryogens are cooled in a superconducting magnet at a temperature of _________
4 Kelvin
The purpose of shimming the magnet is to make the B0 field as homogenous as possible
True or False?
True
The array processor is responsible for reconstructing the collected MR images/data using the Fourier transform, and is located in the MR equipment room.
True
Field strength at magnet isocenter is measured in units of:
tesla or gauss?
Tesla
The unit of measurement of the magnetic field surrounding the periphery of the MR scanner is expressed as:
Gauss or Tesla?
gauss
The liquid cryogens most often used to maintain field strength in a super conducting MR system are
Helium
Doubling the magnetic field strength will ___ the SNR.
double or decrease?
double
who coined the word electricity?
William Gilbert
What is Joseph Fourier famous for?
he developed the mathematical equation to analyze the heat transfer between solid bodies
Who first realized that the earth was one big giant?
William Gilbert, same person that coined the world electricity
Who discovered that an electric current could produce a magnetic field?
Oersted
Who is Michael Faraday?
He discovered electromagnetic induction. When a magnet was moved inside a coil of copper, a tiny electric current flows through the wire (aka Faradays Law)
Whos equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents?
Maxwell
Who is Nikola Tesla?
He discovered the first rotating magnetic field. aka Tesla :)
who developed the equation showing precession of nuclear spins being proportional to magnetic field strength?
Larmor
In 1946 _____ proposed a Nobel Prize winning paper stating that the nucleus behaves like a magnet. He realized that a charged particle (proton) spinning on its own axis has a _____ momentum.
Feliz Bloch, and magnetic momentum
Who created the fourier transform?
Richard Ernst in 1975
Who obtained the first MRI picture?
Lauterbur
The type of rock upon which magnetism was discovered is called?
magnetite
______ discovered that tumors and normal tissue can be distinguished by NMR because of their relaxation times
Damadian
What is the principle nucleus utilized in MR and why is it it used so much in MR?
hydrogen, bc our body has an abundance of it and its a primary element in both water and fat
Magnetic field inhomogeneity is expressed in ____ per million
parts per million (ppm)
10,000 gauss= __ tesla?
10,000 gauss= 1 tesla
The main magnetic field is parallel to the long axis of B___
b0 or b1?
.
b0
one of the three magnetic states of matter :
weak magnetic moment
paramagnetic
one of the three magnetic states of matter :
relatively strong magnetic field..are iron or iron-like substances
ferromagnetic
one of the three magnetic states of matter :
no magnetic field
Diamagnetic
Gadolinium is considered what type of magnetic state?
Ferromagnetic, paramagnetic, or diamagnetic
Paramagnetic because it creates a weak magnetic field
