Mri Test

Front 1

What is the Definistion of a Radiographer?

Back 1

Diagnostic radiographers are responsible to perform safe and accurate imaging examinations and post processing using a wide range of sophisticated equipment and techniques.

Front 2

what are potencial dangers in MRI?

Back 2

Glasses / shoes / tool / pins

Front 3

In the event of an emergency

Back 3

youshould first remove the subject from the MRI scan room

Standnear the doors to the scan room to insure no unauthorized emergency personnelcan enter

Front 4

Proper Safety is Done by

Back 4

Keep the doors to the MR control area shut

Monitoryour subjects while they are in the MRI area

Front 5

When the MRI Scanner is not in use?

Back 5

The magnet is always on

Front 6

Type of magnets that can be commercially used in clinical applications

Back 6

Electromagnet

Front 7

Electromagnetsutilize thelaws of electromagnetic induction by

Back 7

passingan electrical current through a series of wires to produce a magnetic field

Front 8

As absolute zero of temperature ( ________________ ) is approached resistance is virtually absent, so that a high magneticfield can be maintained..

Back 8

− 273 ° C or 4 ° K

Front 9

1.machinesare super-cooled withsubstances known as _______________________ to eliminate resistance.

Back 9

cryogens (usually liquid helium [He] or liquid nitrogen [N])

Front 10

Superconducting electromagnets advantage

Back 10

Advancedapplications and optimum image quality are possible

Front 11

Superconducting electromagnets disadvantage

Back 11

Fringefields are significant, so shielding is necessary

Front 12

______________criticalpart of image optimization

Back 12

Receiver coils

Front 13

Largecoils provide large coverage but ____________

Back 13

relatively poor SNR

Front 14

Phasearray coils of the linear and volume typeare the best as,

Back 14

they combine the benefits of using small coils with those of using large ones

Front 15

Transmit coils

Back 15

Energy is transmitted at the resonantfrequency of hydrogen in the form of a short, intense burst of radiofrequencyknown as a radiofrequency pulse.

Front 16

Receiver Coils

Back 16

Receives MR signal that is sampled toform an image. In order to induce an MR signal, the transverse magnetizationmust occur perpendicular to the receiver coils

Front 17

Magneticresonance imaging (MRI) is an imaging technique used primarily

Back 17

to produce high quality images of thesoft tissues of the human body.

Front 18

Magnetizationcan be manipulated by

Back 18

changing the magnetic field environment(static, gradient, and RF field).

Front 19

RF (radiofrequency) fields are electromagnetic fields that

Back 19

oscillate at RF’s (ten of millions oftimes per second).

Front 20

Gradientmagnetic fields ______

Back 20

Change gradually over space and canchange Quicly over time (thousands of times per second)

Front 21

What are the four steps of getting an MR Image,

Back 21

1. Placing the patient in the magnet

2. Sending Radiofrequency (RF) pulse by coil

3. Receiving signals from the patient by coil

4. Transformation ofsignals into image by complex processing in the computers.

Front 22

63% of human body is ____

Back 22

Hydrogenatoms

Front 23

The hydrogen atom’s proton, possesses a property called _______

Back 23

Spin

Front 24

Spin is __________

Back 24

A small magnetic field, which Will causethe nucleus to produce a NMR signal

Front 25

Phase refers to ?

Back 25

position of a magnetic moment of a spin on its precessional path at any moment in time

Front 26

Frequency refers to ?

Back 26

How fast the magnetic moments of spins are precessing and is measured in MHz in MRI

Front 27

At rest the magnetic moments of the spinsare ?

Back 27

Out of phase

Front 28

At thermal equilibrium_________

Back 28

Thereare more spin-up, low-energy than spin-down

Front 29

The difference in energy between Spins is

determined by_________

Back 29

The strength of B0

Front 30

The spinning protons “precess” about that axis of the external B0 field at the precessional__________

Back 30

Larmoror resonance frequency.

Front 31

Field strengths used in clinical imaging, the Larmor frequency of hydrogen is in theradiofrequency band of the _______

Back 31

Electromagneticspectrum

Front 32

Once the RF transmitter is turned off threethings happen simultaneously?

Back 32

1. The absorbed RF energy is retransmitted(at the resonance frequency).

2. The excited spins begin to return to theoriginal Mzorientation. (T1 recovery to thermal equilibrium).

3. Initially in phase, the excited protonsbegin to dephase (T2 and T2* relaxation)

Front 33

The T1 recovery time is defined as the time it takes for _______of the longitudinal magnetization to ____

Back 33

63% / recover in that tissue.

Front 34

Fat has a_________ & Waterhas a _______ T1 recovery time.

Back 34

short / long

Front 35

T1 recovery times are dependent on _________

Back 35

magnetic field strength

Front 36

TheT2 decay Itis the time it takes for_______of the transverse magnetization to _________

Back 36

63% / be lost due to dephasing

Front 37

Fat has a_____ &,Water has a________ T2 decay time

Back 37

short / long

Front 38

T2 decay times are dependent on_______. As itincreases, tissues take longer to dephase

Back 38

magnetic field strength

Front 39

To Create T1-weighted image magnetization should be allowed to ________by changing the _______________

Back 39

Recover before measuring the MR signal / Repetition time (TR)

Front 40

T1 image weighting is useful for _______

Back 40

Assessing the cerebral cortex, identifying fatty tissue, characterizing focal liver lesions and in general for obtaining morphological information, and, post-contrast imaging

Front 41

To create a T2-weighted image magnetization should be allowed to __________ before measuring the MR signal by changing ______

Back 41

Decay / The echo time (TE).

Front 42

T2 image weighting is useful For _____

Back 42

detecting edema and inflammation, revealing white matter lesions and assessing zonal anatomy in the prostate and uterus.

Front 43

Short TE values are generally used to

Back 43

Reduce T2 contrast contamination and to maintain a relatively high signal intensity

Front 44

The quality of an MR image depends on?

Back 44

Spatial resolution and image contrast/

Signal to noise ratio /and contrast to noise ratio

/Artifacts

Front 45

An MR exploration is a compromise between?

Back 45

Spatial resolution/ SNR/ Scan time

Front 46

To distinguish different tissues

Back 46

obtain contrast between them

Front 47

MRI contrast is due to

Back 47

differences in the MR signal, which depend on the T1, T2 and proton density of the tissues and sequence parameters

Front 48

Bright Hyper-intense on T1W

Back 48

Fat, Subacutehemorrhage, Melanin, Protein-richfluid, Slowly flowing blood, Paramagnetic substances, such asgadolinium, manganese, copper, Corticalpseudolaminarnecrosis

Front 49

Bright Hyper-intense on T2 W

Back 49

Morewater content, as in edema, tumor, infarction, inflammation and infection, Extracellularlylocated methemoglobinin subacutehemorrhage

Front 50

Intermediate T1W

Back 50

Gray matter darker than

white matter

Front 51

Intermediate T2W

Back 51

White matter darker

than grey matter

Front 52

Dark Hypo-intense on T1W

Back 52

Bone, Air,Morewater content, as in edema, tumor, infarction, inflammation, infection, hyperacuteor chronic hemorrhage, Lowproton density as in calcification

Front 53

Dark Hypo-intense on T2 W

Back 53

Bone, Air, Fat, Low proton density, as incalcification and fibrosis, Paramagneticmaterial, such as deoxyhemoglobin, intracelullarmethemoglobin,iron, ferritin, hemosiderin, melanin,Protein-richfluid

Front 54

Movment Artefact results from

Back 54

patient /encoding/ signal processing

Front 55

The patient's movements are the most common cause of image artifacts

Back 55

Ghosting artefacts

Front 56

Magnetic susceptibility

Back 56

interfaces between air and tissue orbetween trabecular bone and tissues/These static field inhomogeneities /The presence of any metal