Be 583 Exam Iv

Front 1

The phase shift between E and B in EM waves

Back 1

90 degrees

Front 2

MRI Energy Frequency

Back 2

3-100MHZ

Front 3

Relation between number of energy states with S

Back 3

Number=2S+1

Front 4

Dipole-Dipole interaction definition:

Back 4

Intercation between proton-proton or proton -electron

Front 5

Three classes of magnetic susceptibility:

Back 5

dimagnetic, paramagnetic, ferromagnetic

Front 6

Diamagnetism, definitions, features, examples:

Back 6

X<1, no unpaired e, a weak opposite field is generated, reducing the effective field; most tissue in body are diamagnetic

Front 7

What gives water its diamagnetic properties?

Back 7

The electrons in water gives it diamagnetic properties.

Front 8

Paramagnetism, defin, features, examples:

Back 8

X >1 slightly, unpaired e; small field to increase effective strength ONLY under external field; Gd has the largest number of unpaired e.

Front 9

Superparamagnetism: features:

Back 9

A subclass of paramagnetic material with X>100

Front 10

Ferromagnetism: definition, features, examples:

Back 10

X>>100 (larger than para); attracts magnetic field and can be permanently magnetized. Fe, Co and Ni are examples

Front 11

At T1, ___% of M0 is recovered:

Back 11

At T1, 63% of M0 is recovered.

Front 12

Mz=?

Back 12

Mz=M0(1-e^(-t/T1))

Front 13

T1 can depend on these two general factors:

Back 13

Tissue and main field strength

Front 14

Hydrogen Gyromagnetic ratio:

Back 14

Hydrogen GR = 42.6MHz/Tesla

Front 15

RF wave equation:

Back 15

cos(wt)

Front 16

T2 decay are typicaly this much faster than T1:

Back 16

Typically 5 to 10 times faster.

Front 17

Three factors causing T2 dephasing:

Back 17

1. External field inhomogeneity; 2. Spin-spin interaction exert slight field on each other (distance dependent); 3. Diffusion (small role)

Front 18

R2*=?

Back 18

R2*=R2+γ*ΔB

Front 19

The max signal at t=nTR is ___than after the first 90 pulse.

Back 19

The max signal at t=nTR is less than after the first 90 pulse.

Front 20

The more __ the protons, the higher the FID signal induced.

Back 20

The more mobile the protons, the higher the FID signal induced.

Front 21

To measure T1 signal, TR should be around __, why?

Back 21

TR should around T1 to max contrast and to give enough Mz to give a signal.

Front 22

To measure T2* contrast, TE should be ___, but at the cost of ___:

Back 22

To measure T2* contrast, TE should be long, but at the cost of SNR.

Front 23

Order in terms of T2: fat/protein, water, solid

Back 23

T2 (slowest to fastest): water>fat/protein>solid

Front 24

T1 shortest (most efficient) at this:

Back 24

T1 fastest when proton natural movement frequency ~ larmor freq of hydrogen

Front 25

Fat/protein, water, solid nature freq vs Larmor Freq w0

Back 25

Fat/Protein~w0 (shortest T1); water>>w0; solid<w0; so in T1: Fat/Protein<solid<water

Front 26

Increasing proportion of hydration water can cause:

Back 26

Shorter T1 (brigter T1); shorter T2 (darker T2)

Front 27

For T1 image: these TE should be __, TR should be__;

Back 27

For T1 image: these TE should be short, TR should be short

Front 28

For T2 image: these TE should be __, TR should be__;

Back 28

For T2 image: these TE should be long, TR should be intermediate/long.

Front 29

For ProtDen image: these TE should be __, TR should be__;

Back 29

For ProtDen image: these TE should be short, TR should be long.

Front 30

Partial saturation PS produces this image:

Back 30

Partial saturation PS produces T1 weighted image. (incomplete T1 recovery with short TE); hard to use due inability to use short TE

Front 31

Saturation recovery PS produces this image:

Back 31

Saturation recovery PS produces Proton Density weighted image. full T1 recovery with short TE); hard to use due inability to use short TE.

Front 32

In Inversion Recovery PS, the null point is:

Back 32

Ti(null)=ln(2)*T1=0.693T1

Front 34

STIR pulse sequence:

Back 34

Short T1 Inversion Recovery; uses TI=fat T1 (null), so as to supprese fat signal.

Front 35

Assymetric echoes:

Back 35

if tau differs in a series of echos.

Front 36

The RF pulse for a range of frequencies is generally this shape:

Back 36

The RF pulse for a range of frequencies is generally a sinc wave.

Front 37

Cross talk in slice selection: cause, solution and consequence.

Back 37

Cross talk is causes by overlaps between Gaussian frequency selection spectrum (Gaussian in reality), gaps can be created between Gaussian slices, so this creates gaps in image slices.

Front 38

Frequency encoding is applied on this gradient and during___:

Back 38

Frequency encoding is applied on Gx during readout.

Front 39

Phase encoding gradient is on this gradient and between:

Back 39

Phase encoding gradient is on this gradient and between:

Front 40

The phase shifts required for n rows is __; the image time is ___.

Back 40

The phase shifts required for n rows is 360/n; the image time is TR*n;

Front 41

Six factors that influence SNR in MRI:

Back 41

1. B0; 2. TE & TR times; 3. RF coil & sample; 4. Number of repetitions; 5. Resolution (inverse); 6. Slice thickness

Front 42

Generally speaking, T1 (increase/decrease) with B0

Back 42

Generally speaking, T1 (increases) with B0

Front 43

Four factors influencing CNR:

Back 43

1. B0 (better CNR for T1 at lower B0); 2.TR and TE times; 3. Tissue relaxation difference; 4.Proton density.

Front 44

Four benefits of having higher B0:

Back 44

Shorter scan time; better SNR; better T1 CA visualization; Better MRS results

Front 46

Rank T1 longest-shortest for GM, WM, CSF, Edema

Back 46

T1 longest to shortest: CSF>Edema>GM>WM

Front 47

Rank T2 longest-shortest for GM, MW, CSF, Edema

Back 47

T2 longest to shortest: CSF>Edema>GM>WM

Front 48

Time of Flight MRA uses blood's ___T1eff, the pulse sequence is ____weighted.

Back 48

Time of Flight MRA uses blood's shortened T1eff, the pulse sequence is heavily T1 weighted.

Front 49

1/T1(eff)=

Back 49

1/T1(eff)=1/T1+velocity/slice thickness

Front 50

Phase contrast Angiography requires this two types of images; the moving objects appear (darker/brighter).

Back 50

Phase contrast Angiography requires this a motion compensated and a noncompensated images; the moving objects appear (brighter).

Front 51

Diffusion weighted imaging uses this pulse sequence:

Back 51

Symmetric gradients before/after pi pulses; the first gradient encodes a phase, the second rephase; if diffusion occurred, depahsing more prominent.

Front 52

Two factors that may contribute to greater pixel signal loss in diffusion weighted pulse sequences:

Back 52

1. Faster diffusion; 2. Greater gradient used.

Front 53

Diffusion tensor imaging technique, target?

Back 53

Utilizes diffusion tensor PS but with multiple directions of gradient, calculates tensor in each voxel. Usually images white matter's axon direction.

Front 54

Hemoglobin is ___in oxygenated state; and ___ in deoxygenated state; The Fe form is :

Back 54

Hemoglobin is diamagnetic in oxygenated state; and paramagnetic in deoxygenated state; The Fe form is: Ferrous Fe+2 in deoxygenated.

Front 55

BOLD stands for?

Back 55

Blood Oxygenation Level Dependent Signal.

Front 56

How does BOLD respond to neurotic activity?

Back 56

More activty gives a greater net amount of oxygenated Hb (Greater delivery-greater used), this gives less paramagnetic blood, hence make T2 and T2* longer due to less dephasing

Front 57

What does STEAM stand for? Features:

Back 57

Stimulated Echo Acquisition Mode; uses 3 orthogonal gradients to select voxel; use other gradient to crush unwanted magnetization. Used in MRS

Front 58

What does PRESS stand for? Features:

Back 58

Point Resolved Spectroscopy; uses two 180 pulse on two axis.

Front 59

CSI stands for what and features:

Back 59

Chemical Shift Imaging; can be used in 2D or 3D; can be used to do tumor metabolic mapping.

Front 60

Application of Diffusion weighted spectroscopy?

Back 60

To exam cell sin perfusion culture; fluid movement can be excluded.

Front 61

31P imaging features, resolution, general uses:

Back 61

31P is 100% abundant but only 6.7% of proton sensitivity; voxel sizes are large 3cm^3; good for bioenergetics, pH and PL metabolism.

Front 62

5 chemicals that can be observed in 31P imaging:

Back 62

NTP/NDP, Pi, PCr, PME, PDE

Front 63

Paramagnetic CA can ___T1 and ___T2.

Back 63

Paramagnetic CA can shorten both T1 and T2.

Front 64

Primary mechansim (general) of T1 shortening by paramagnetic ion is ___.

Back 64

Primary mechansim of T1 shortening by paramagnetic ion is dipole-dipole coupling.

Front 65

Gd can enhance T1 rexlation because:

Back 65

Gd's electron make strong fields that oscillate at Larmor Freq, hence relaxing water.

Front 66

Two factors that are required for water to achieve high relaxivity when used with Gd

Back 66

Rapid water exchange and slow Gd complex rotation.

Front 67

Inner sphere vs outer sphere relxation:

Back 67

Inner sphere occurs if water binds to the Gd

Front 68

How can chelate by itself be toxic?

Back 68

Chelate can bind to important physiological ions.

Front 69

Gd(DTPA) has __ exchange sites, is highly ___, hence helps with renal clearnance; demetallation occurs at long residence time such as?

Back 69

Gd(DTPA) has one exchange sites, is highly hydrophilic, hence helps with renal clearnance; demetallation occurs at long residence time such as renal failure.

Front 70

Gd(DTPA) vs Gd(DTPA)-BMA?

Back 70

Gd(DTPA)-BMA replaces two carboxyl with neutral N; better osmolality.

Front 71

Gd chelate pharmacokinetics:

Back 71

Ionic and non-ionic forms similar; rapid interstitium and plasma exchange, rapid renal elimination, do not cross healthy BBB; can be used for GFR.

Front 72

Gd chelate dynamic imaging of meningiomas vs other lesions:

Back 72

Meningiomas can show up in 5min, others 5-30 mins.

Front 73

How can Gd chelate be used to distinguish low grade vs high grade tumors in brain?

Back 73

Low grade tumors shows little enhancement, while high grade shows ring enhancement (so does MS plaques and metastatic tumors).

Front 74

How is Gd chelate used in breast and liver lesions:

Back 74

In breast Gd reflects angiogenesis; in liver, imaging best down before equilibrium with interstitium

Front 75

How is Gd chelate used in heart imaging:

Back 75

One image per beat approach allows for the construction of a time intensity curve and hence calculation of dynamic parameters. Ischemic tissues can also be seen.

Front 76

Relaxivity unit:

Back 76

1/(s*mM)

Front 77

Macromolecular Gd agents, size, general purpose, come hurdles?

Back 77

Macromolecular agents are generally >20KD, serve as blood pool agent to investigate permeability; renal toxicity and immunogenicity are hurdles.

Front 78

Macromolecular Gd agents: clearance and relaxivity features:

Back 78

Macromolecular Gd agents are too large for Glomerular filtration; rather slowly broken down by hepatobilliary system; they have high relaxavity due to slow rotation and more Gd per molecule.

Front 79

Macromolecular Gd's benefit and down sides in MRA applications:

Back 79

Macromolecular CA overcomes velocity range flow problem and high lights tumor's complex flow really well; but it's hard to distinguish arteries from veins.

Front 80

Two things measured by microvascular permeability using macrovascular Gd agents:

Back 80

Microvascular hyperpermeability is a reflection of malignancies, specific transport mechanism can also be imaged using such method.

Front 81

Parametric mapping using macromolecular agents reflects this two paratmeters:

Back 81

Parametric mapping using macromolecular agents can reflect fractional blood volume or permeability-surface area. All related to tissue hyperpermeability.

Front 82

General concentration range for Gd ions needed for imaging:

Back 82

Gd are generally the micromolar range.

Front 83

The three types of MR targeted imaging involve using:

Back 83

Targeted CA are small molecules, macromolecules and particles.

Front 84

The small molecule targeted CA uses these two factors to target:

Back 84

The small molecule targeted CA uses protein binding and lipophilicity to target.

Front 85

What targeted small molecule CA is used for liver imaging, how?

Back 85

Gd DTPA is used for pre equilibrium liver imaging; Or can use Gd BOPTA that is specifically uptaken by hepatocyte transporters.

Front 86

How is targeted small molecule Gd CA used as blood pool agents:

Back 86

Targeted small Gd CA can bind reversibly to albumin, which enhances Gd's blood life time and relaxivity.

Front 87

Three factors that determine if targeted macromolecular Gd CA will be intravascular

Back 87

Size, charge, 3D shape.

Front 88

Four reasons why Gd labeled antibodies are inefficient:

Back 88

Higher concentration needed, low relaxivity due to flexible linker, limited Gd can be attached, polyfunctional linker will hamper biodistribution.

Front 89

Copolymeric Targeted Gd CA

Back 89

Chelating monomers linked to give slower rotational times. Targeting moieties can be added on the monomers. Hard to make monodisperse

Front 90

Dendrimeric Targeted Gd CA

Back 90

Branching appearnce polymer, easy to make monodisperse.

Front 91

Unique features of linear polylysine and dextran based polymer targeted Gd CA?

Back 91

Polylysin free amines must be masked using PEG; Dextran can allow functionalization.

Front 92

Larger particles tend to be cleared faster due to these cells:

Back 92

Larger particles tend to be cleared faster due to macrophages cells of the RES system.

Front 93

Particulate agents that are cleared by RES tend to have higher concentration in (spleen or liver)?

Back 93

Agents that are cleared by RES tend to have higher concentration in (spleen).

Front 94

This type of particulate surface coating makes clearance slower:

Back 94

Neutral hydrophilic particulate surface coating makes clearance slower.

Front 95

Features of Gd-loaded liposomes as a particulate CA

Back 95

Small relaxivity due to limted water diffusion across membrane, smaller particle have higher relaxivity.

Front 96

What's another form of Gd liposome (besides Gd-loaded liposome)? Size effects?

Back 96

Gd can also be directly incorporated on the liposome membrane; small liposomes in this case shows higher relaxivity (possible steric hinderance reason.)

Front 97

Manganese Hydroxyapatite synthesis and usage?

Back 97

Made by precipitating calcium and phosphorous with Mn doping; good for liver and spleen imaging and can be modified for targeting.

Front 98

Features of gas bubbles as used in targeted CA imaging:

Back 98

Bubles can nonuniformly shorting T2/T2*; higher concentration needed than US; also uniform with pressure.

Front 99

Examples of types of particulate targed Gd CAs:

Back 99

liposomes loaded, embedded liposome, hydroxyapatite precipitate, microbubbles.

Front 100

Examples of types of macromoleculare targed Gd CAs:

Back 100

Antibody, Copolymeric, dendrimeric

Front 101

Superparamagnetic agents produces much ___R1 and R2 than Gd CA.

Back 101

Superparamagnetic agents produces much (higher) R1 and R2 than Gd CA.

Front 102

Uncoated SPIOs may activate this immune system:

Back 102

Uncoated SPIOs may activate the complement system.

Front 103

Which one differs more for SPIO and USPIO, R1 or R2?

Back 103

R1 is almost identical, but R2 for SPIO is twice as large.

Front 104

SPIO usage in GI imaging:

Back 104

300nm SPIO with silicone coating are orally administered for GI imaging.

Front 105

SPIO usage in liver imaging:

Back 105

Ferumoxide (150nm) SPIO can be used to darken normal liver tissues; arabinogalactan-labeled particles can bind to hepatic asialoglyccoprotein receptors.

Front 106

Lymph node imaging with SPIOs:

Back 106

Small and long lasting USPIO (<30nm) can get into healthy lymph; metastaic lymph appears bright on T2 due to inability for USPIO to enter.

Front 107

SPIO atherosclerosis/inflammation imaging:

Back 107

Small USPIO (<30nm) can be taken up by macrophages at plaque sites.

Front 108

SPIO as a blood pool agent:

Back 108

Small SPIOs can stay in blood vessle for a long time.

Front 109

SPIO cell tracking can be done in these cells:

Back 109

Leukocyte or T cells

Front 110

SPIO use in neuronal tracing and axonal transport:

Back 110

When injected into ganglia and nerves, axonal transport occurs.

Front 111

Seven uses of SPIOs

Back 111

GI imaging, Liver imaging, lymph node imaging, artherosclerosis imaging, blood pool imaging, Cell tracking, axonal transport imaging.