Basic Physics And Brief History Flashcards
Base on the physic principle of nuclear magnetic resonance (NMR), 1st describe in the 1930s and 40s
Magnetic resonance imaging (MRI)
Part of electromagnetic spectrum that includes visible light and x-rays
Radio frequency energy
In electromagnetic spectrum where is the radio frequencies located?
Far left
In electromagnetic spectrum where is the visible light located?
Middle
In electromagnetic spectrum where is the x-rays located?
Far right
All of these waved are defined by?
Wavelength and frequency
The __ is the distance between peaks of wave
Wavelength
Is how many cycles are completed in a seconds
Frequency
Is the height or power of the wave
Amplitude
When talking! About 2 or more waves we can also describe a?
Phase
Blue and orange waves have the same frequency and line up completely so they are also?
In phase
If we shift the orange wave to the right the frequency remains __ but the waves are now?
The same, out of phase
Described by their unique phase and frequency
Radio frequency signals
A point on the computer is called a __ a concatenation of the words picture and element
Pixel
Mr images are made up of a series __ or volume and element
Voxel
each square on the picture corresponds to a?
volume of tissue on the body
The mri machine is designed to measure the __ from each of the small volumes, localized them in 3D space and plot them on a __x__ or __x__ matrix to make a visible picture
NMR signal, 256x256, and 512x512
Describe the principles of NMR in a?
Single small square or box of tissue
Where a flowing current electrons has an associated magnetic field oriented 90 degrees from the direction of current flow
Electromagnetism
The direction of the __ associated with the coil is defined by the right hand rule curl the fingers of your right hand in the direction of the current flow through the coil and your outstretched thumb will point at the direction of the associated ___
magnetic field
Consist of a single proton in the nucleus with a single circulating electron orbiting around that proton for the principal of NMR
Hydrogen atom
An adult is about 60% in __ which contains two hydrogen atoms for every __
Water, oxygen
Ones with little extra energy possibly from some local increased heat will line up against main magnetic field and therefore considered to be in a?
High energy state
The ones liningg up in with the main magnetic field are in a?
Low energy state
These protons don’t simply point with or against the main magnetic field they actually precess much like a?
Spinning top
The rate of __ can be determined exactly by the larmor frequency equation
Precession
States that the rate of rotation is directly proportional to the strength of the local magnetic field
Larmor frequency equation
1tesla the larmor frequency of a hydrogen proton or spin is?
42.58 megahertz
2 tesla
85.16 megahertz
3 tesla
127.74 megahertz
Most of the protons are in a __ pointing in the direction of the main magnetic field
low energy state
Few energetic protons ate oriented against the main magnetic field in the?
Higher energy state
Even though each proton is precessing in space when you cancel all ths opposing vectors you end up in with a __ pointing with a large main external magnetic field this is called a __
Net magnetization vectors, longitudinal magnetization
The sinusoidal radio frequency pushes the protons to synchronize and spin together this is the __ portion of an NMR
resonance
If we add up all the magnetic moment you can see we now have a net magnetic force oriented horizontally or 90 degrees to the longitudinal magnetization this is called the?
Transverse magnetization
Transverse magnetization can be detected with a?
Coil and antenna
A current can create a?
Magnet
A magnet can create a?
Current
Being all positively charged, will repel each other and move apart as they spread apat we lose that transverse magnetization this process is called? Because it has to do with the interaction of protons or spin themselves
T2 or spin spin relaxation
No ___ transfer occurs with this relaxation
Net energy
As these protons fall back down to baseline, we regrow the longitudinal magnetization this is referred to as the? Because it involves the transfer energy from the spins to the surrounding tissues or lattice
T1 or spin lattice relaxation
As the resonant frequency of the local protons produces a radio signal of the same frequency that can be detected by a coil of wire as the energy is removed the proton first move apart in a? Destroying the transverse magnetization
T2 or spin-spin relaxation
By changing how quickly we put in the radio frequency energy or the?
Repetition time (TR)
How quickly we choose to listen to the signal coming back from the transverse magnetization or?
Echo time (TE)
Process referred to as?
Pulse sequence
Are accentuated by rapidly exposing the protons to radio frequency energy and keeps the spins in high energy state and thus reducing the effective longitudinal magnetization tissue that recover quickly will have a large signal although slow to recover will have a low signal
T1 relaxation effects
Are accentuated by a prolonged echo time to allow the spins to move away from each other and accentuate the differences in t2 relaxation between regional tissue or chemicals
T2 effect
Is obtained with a pulse sequence of a long TR and long TE decreasing the T1 affect with along TE
T2 weighted image
Is obtained with a pulse sequence of short TR in a short TE enchancing T1 relaxation and minimizing T2 effects
T1 weighted image
In between these two is the __ which is obtained with a long TR and short TE effectively minimizing T1 and T2 effects and basically giving us idea of the absolute number or density of protons in the region
Proton density pulse sequence
1st to propose NMR to diagnose disease in human who in march 1971 addition of the journal science published a short article entitled tumor detection by NMR in which he suggested that the NMR signal from tumors of the body could be differentiated from the normal tissue and therefore could be detected
Dr. Raymond damadian
In conjunction with a standard MR image to help distinguish benign from malignant processes in the body
MR spectroscopy
We have to be able to localize the signals coming from the sample or tissue in 3D space the 1st to propose a technique to do just that was __ in march 19,1973 addition of nature he published a brief article entitled image formation by induced local interactions he describe a technique using magnetic radiance to identify location of 2 1mm capillsry tubes filled with water both of which were submerged in a larger 4.2 mm tube filled with heavy water
Dr. Paul lauterbur
Standard hydrogen atom
Protium
Contains a neutron as well as proton which limits the spin of the nucleus and therefore does not give a good NMR signal
Deuterium
Dr paul lauterbur called his technique?
Zeumatography
