ARMRIT Practice test questions and Answers Latest Update Fully Solved 100%
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Course
ARMRIT
Institution
ARMRIT
In MRI, substances respond to a specific radio frequency which is known as: - Resonance
frequency
The effects of main magnetic field inhomogeneities on the FID signal are corrected for in a Spin-echo
sequence by applying a second radio-frequency pulse. The flip angle of this radio-frequency puls...
ARMRIT STUDY GUIDE PACKET
RADIOFREQUENCY (RF) - ELECTROMAGNETIC RADIATION LOWER IN ENERGY THAN INFRARED. THE
RF USED IN MRI IS IN THE FORM OF A BURST OF RF ENERGY (PULSE) I THE 10 MHZ TO 100MHZ RANGE
RF PULS, DELIVERED TO THE PATIENT BY RF TRANSMITTER. THE RF FREQUENCY, AT THE LARMOR
FREQUENCY, RESULTS IN ROTATION OF THE NET MAGNETIZATION VECTRO AND PHASE COHERENCE OF
THE NUCLEAR SPINS. AN RF COIL IS USED FOR TRANSMITTING AND RECEIVING MRI SIGNALS (RF).
FRINGE FIELDS - WEAKER MAGNETIC FIELDS THAT ARE AWAY FROM THE ISOCENTER, IN MRI
OUTSIDE OF THE SCANNING AREA.
PROTON - A SUBATOMIC PARTICLE HAVING A POSITVIE CHARGE IDENTICAL IN MAGNITUDE TO
THE NEGATIVE CHARGE OF AN ELECTRON AND, TOGETHER WITH THE NEUTRON, A COMPONENT OF ALL
ATOMIC NUCLEI. THE PROTON FORMS, BY ITSLEF, THE NUCLEUS OF THE HYDROGEN ATOM. THE MASS OF
A PROTON IS APPROXIMATELY 1836 TIMES THAT OF AN ELECTRON AND THE MASS OF AN ATOM IS
CONTAINED ALMOST ENTIRELY IN THE NUCLEUS. THE PROTON HAS AN INTRINSIC ANGULAR
MOMENTUM OR SPIN AND THUS A MAGNETIC MOMENT (VERY SMALL MAGNETIC FIELD). THE NUMBER
OF PROTONS IN THE NUCLEUS OF AN ATOM DETERMINES WHAT ELEMENT IT IS; THE ATOMIC NUMBER
OF AN ELEMENT DENOTES THE NUMBER OF PROTONS IN THE NUCLEUS.
ELECTRON - A SUBATOMIC MPARTICLE THAT, ALONG WITH PROTONS AND NEUTRONS, MAKE UP
THE ATOMS THE FLOW OF AN ELECTRIC CURRENT IN A CONDUCTOR IS CAUSED BY THE DRIFTING OF
FREE ELECTRONS IN THE CONDUCTOR. HEAT CONDUCTION IS ALSO PRIMARILY A PHENOMENON OF
ELECTRON ACTIVITY. THE CHARGE OF THE ELECTRON IS THE BASIC UNIT OF ELECTRICITY. ELECTRONS
HAVE HALF-INTEGRAL SPIN; SPIN IS A PROPERTY OF SUBATOMIC PARTICLES THAT INDICATES THE
PARTICLE'S ANGULAR MOMENTUM.
NEUTRON - A SUBATOMIC PARTICLE THAT IS NEUTRAL THEREFORE HAS NO CHARGE. IT IS
LOCATED IN THE NUCLEUS AND SERVES AS A STABILIZER. THE MASS OF A NEUTRON IS SLIGHTLY
GREATER THAN THE PROTON MASS AND HAS AN ENORMOUS EFFECT ON THE QUANTUM SPIN VALUE OF
AN ELEMENT. THE NET CHARGE ON A NEUTRON IS 0
MAGNETISM - IS DESCRIED AS THE ABILITY OF A SUBSTANCE TO ATTRACT IRON, COBALT AND
NICKEL. IT IS THE POWER OR FORCE CREATED BY A SUBSTANCE HAVING THE PROPERTY OF CREATING OR
INDUCING MAGNETIC DIPOLES. THE MAGNETIC FIELD OF ANY MAGNET HAS A DIRECTION, SIGNIFIED
NORTH AND SOUTH. THIS PROPERTY OF A MAGNET MAKES IT A DIPOLE. DIPOLE - A MAGNETIC FIELD
CHARACTERIZED BY ITS OWN MAGNETIC NORTH AND SOUTH POLES SEPARATED BY A FINITE DISTANCE.
,MAGNETIC SUSCEPTIBILITY - DEFINED AS THE TENDENCY OF A SUBSTANCE TO ATTRACT OR REPEL
MAGNETIC LINES OF FORCE DEPENDENT ON THE MAGNETIC PROPERTIES OF ITS ELECTRONS.
DIAMAGNETIC - THE PROPERTY OF MOST SUBSTANCES WITH PAIRED ORBITAL ELECTRONS THAT
HAVE OPPOSITE SPINNING AND THEIR MAGNETIC MOENTS CANCEL EACH OTHER OUT. SUBSTANCES
WITH DIAMAGNETIC SUSCEPTIBILITY WEAKLY ATTRACT OR REPEL MAGNETIC LINES OF FORCE.
MAGNETIC SUSCEPTIBILITY OF MOST HUMAN BODY TISSUES ARE DESCRIBED AS DIAMAGNETIC.
PARAMAGNETIC - THE PROPERTY OF SUBSTANCES WITH POSITIVE MAGNETIC SUSCEPTIBILITY
THAT ATTRACT AND REPEL MAGNETIC LINES OF FORCE. THESE SUBSTANCES (GADOLINIUM,
METHEMOGLOBIN, FREE RADICALS) CONTAIN ONE OR MORE UNPAIRED ORBITAL ELECTRONS AND
PRODUCE MARKED REDUCTIONS IN THE T1 AND T2 RELAXATION TIMES. UNPAIRED ORBITAL ELECTRONS
SPIN IN THE SAME DIRECTION AND HAVE THE TENDENCY TO LINE UP WITH THE MAGNETIC FIELD.
THEREFORE PRODUCING ADDITIONAL MAGNETIC FIELDS.
ATOMS - FUNDAMENTAL SUBMICROSCOPIC UNIT OF ALL MASS. SIZE OF THE ATOM AND ITS
WEIGHT HAVE INTERESTED SCIENTISTS FOR A LONG PERIOD. SUBSEQUENTLY, EXPERIMENTS WERE
DEVISED TO DETERMINE THE SIZE AND WEIGHT OF THE VARIOUS ATOMS. THE LIGHTEST OF ALL ATOMS
IS HYDROGEN.
SUPER-PARAMAGNETIC - THE PROPERTY OF SUBSTANCES WITH LARGE POSITIVE MAGNETIC
SUSCEPTIBILITY WHICH STRONGLY ATTRACT OR REPEL MAGNETIC LINE SOF FORCE. THESE SUBSTANCES
(HEMOSIDERIN AND SUPERPARAMAGNETIC IRON OXIDE -SPIO) HAVE A SINGLE MAGNETIC DOMAIN AND
ARE MAGNETIZED IN A MAGNETIC FIELD. THEIR MAGNETIC SUSCEPTIBILITIES ARE MUCH LARGER THAN
THOSE OF PARAMAGNETIC SUBSTANCES AND SIMILAR TO THOSE OF FERROMAGNETIC MATERIALS.
UNLIKE FERROMAGNETIC SUBSTANCES, SUPERPARAMAGNETIC MATERIALS DO NOT EXHIBIT RESIDUAL
MAGNETISM WHEN THE EXTERNAL FIELD IS REMOVED.
FERROMAGNETIC - THE PROPERTY OF SUBSTANCES WITH LARGE POSITIVE MAGNETIC
SUSCEPTIBILITY THAT BECOME MAGNETIZED WITHIN A MAGNETIC FIELD AND REMAIN MAGNETIZED
AGTER BEING REMOVED FROM THE MAGNETIC FIELD. FERROMAGNETIC SUBSTANCES INCLUDE A
NUMBER OF IRON AN COBALT-CONTAINING METALS.
MAGNETIC FIELD - A VECTOR QUANTITIY CONSISTING OF BOTH A NORTH AND SOUTH POLE; IT
EXERTS AN INDUCTION FORCE ON FERROMAGNETIC AND PARAMAGNETIC SUBSTANCES. WHEN
, SYMBOLIZING THE FLOW AND AREA OF A MAGNETIC FIELD, SPECIAL LINES ARE USED; THEY ARE FIELD
OR FLUX LINES
FIELD OR FLUX LINES - MEASURE THE FLOW AND AREA OF A MAGNETIC FIELD. THE STRONGEST
AREA OF THE MAGNETIC FIELD IS WHERE THE FIELD OR FLUX LINES CONVERGE AND IS CALLED THE
ISOCENTER. AWAY FROM THE ISOCENTER THE FIELD OR FLIX LINES REPRESENT THE FRINGE FIELDS.
ISOCENTER - AREA OF THE MAGNETIC FIELD WHERE THE FIELD STRENGTH IS THE GREATEST, IN
MRI THE CENTER OF THE SCAN AREA
FLUX - FLOW OF ENERGY; MAGNETIC FIELD FLOWING FROM NORTH TO SOUTH POLES
REPRESENTED BY MAGNETIC LINES OF FORCE.
FORCE - THE ABILITY TO CREATE WORK OR CHANGE (MEASURED IN HORSEPOWER). WHEN
DESCRIBING THE STRENGTH OF AN MRI MAIN MAGNETIC FIELD, THE SI UNIT MOST COMMONLY USED IS
TESLA. A SYMBOL TO DESCRIBE THE DIRECTION AND STRENGTH OF A MAGNETIC FIELD IS CALLED
VECTOR.
VECTOR - A MATHEMATICAL ENTITIY CHARACTERIZED BY STRENGTH (MAGNITUDE) AND
DIRECTION. VECTOR QUANTITIES CAN BE ADDED OR SUBTRACTED FROM ON ANOTHER. VECTORS WITH
THE SAME DIRECTION - ADD UP; OPPOSITE DIRECTION - CANCEL EACH OTHER OUT. THE SYMBOL USED
TO DESCRIBE THE STATIC (MAIN) MAGNETIC FIELD AND ITS VECTOR IS BO.
HOMOGENEITY - TERM USED TO DESCRIBE MAGNETIC UNIFORMITY IN THE LARGE STATIC
MAGNETIC FIELD IS HOMOGENEITY. THE SPECIFICATION THAT IS ACCEPTABLE FOR FIELD HOMOGENEITY
OF AN MRI MAGNET FOR CLINICAL SCANNING IS 20-30 PP M
FARADAY'S LAW - IN A LOOP OF CONDUCTOR WHERE AN ELECTRIC CURRENT IS INTRODUCED AND
MAINTAINED, A MAGNETIC FIELD WILL BE PRODUCED IN THE CENTER. THIS IS ALSO TRUE INVERSELY.
FLEMINGS RIGHT HAND RULE - IF THE ELECTRON FLOW IS IN THE DIRECTION OF THE CURLED
FINGERS, THE THUMB WILL POINT IN THE DIRECTION OF ITS MAGNETIC NORTH POLE.
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