Bio-Imaging Exam 3

Front 1

X-Ray CT uses _____ _____ _______ and it is good for _____ tissues (3 examples)

Back 1

ionizing X-ray radiation; dense (bone, coins and nails)

Front 2

MRI uses __________ ______ and a ______ ______ and it is good for ____, _____ tissues (3 examples)

Back 2

radiofrequency signals and a magnetic field; soft, non-calcified (muscle, cartilages, and Kiwi)

Front 3

Why MRI?

1) The human body is approx. ___ % water.
2) ____ ____ has an NMR signal
3) In most biomedical applications, MRI senses the presence and amount of ___ ____ (____) in a tissue
4) The _____ of the proton MRI signal depends on various factors.

Back 3

1) 75
2) hydrogen nuclei
3) hydrogen nuclei (proton)
4) intensity

Front 4

MRI relies on the _______ properties of _____
hydrogen nuclei in water.

Back 4

relaxation ; excited

Front 5

When the object is placed in a powerful, uniform magnetic field the spins of the atomic nuclei with _______ spin numbers (essentially, an unpaired proton or
neutron) within the tissue all align in one of two opposite
directions: ______ to the magnetic field or _______.

Back 5

nonzero ; parallel or antiparallel

Front 6

In the clinic, common magnetic field strengths range
from _ to _ teslas, and 7 tesla magnets are being
introduced, (up to __ are being used in animal studies)

Earth’s Magnetic Field on average is around 50 μT, that
is more than 100,000 times lower.

Back 6

0.3 to 3 ; 20T

Front 7

In order to understand MRI contrast, it is important to
have some understanding of the ____ _______ involved
in relaxation processes that establish ______
following RF excitation. As the high-energy nuclei _____
and ______, they emit energy at rates which are
recorded to provide information about their environment
(__ signal).

Back 7

time constants ; equilibrium ; relax ; realign ; MR

Front 8

The realignment of nuclear spins with the magnetic field
is termed _____ ______ and the time (typically
about 1 sec) required for a certain percentage of the
tissue nuclei to realign is termed _______.

Back 8

longitudinal relaxation ; "Time 1" or T1

Front 9

______ imaging relies upon local dephasing of
spins following the application of the ______ energy
pulse; the ______ relaxation time (typically < 100 ms
for tissue) is termed "Time 2" or T2.

Back 9

T2-weighted ; transverse ; transverse

Front 10

Image contrast is created by using a selection of image
acquisition parameters that weights signal by __ or __,
among others.

Back 10

T1, or T2

Front 11

In the brain, T1-weighting causes ____ ____ (nerve
connections, i.e. white matter) to appear white,
congregations of _____ (i.e. gray matter) to appear
gray, and ________ ______ to appear dark.

In a T2-weighetd image, the contrast of "white matter,"
"gray matter'" and "cerebrospinal fluid" is _______.

Back 11

fiber tracts ; neurons ; cerebrospinal fluid

reversed

Front 12

Both T1-weighted and T2-weighted images are acquired
for most medical examinations. However, these 2 sets of images are not always sufficient to adequately show anatomy or pathology. One option is to administer a
______ ____ to delineate areas of interest.

Back 12

contrast agent

Front 13

Most commonly, a ________ contrast agent is given. _______-enhanced tissues and fluids appear extremely bright on T1-weighted images. When injected I.V., it provides ____ sensitivity for the detection of abnormalities in the vasculature.

Back 13

paramagnetic ; Gadolinium ; high

Front 14

More recently, _________________ contrast agents (e.g.
____ ____ _____________) have become available. These
agents appear very dark on T2-weighted images. These
agents may be used for liver imaging - normal liver
tissue retains the agent, but abnormal areas (e.g. scars,
tumors) do not.

Back 14

superparamagnetic ; iron oxide nanoparticles

Front 15

Specialized MRI scans

Back 15

MR Angiography
MR Spectroscopy
Functional MRI
Interventional MRI
MR-guided focused ultrasound

Front 16

Increased neural activity causes an increased demand for ______, and the vascular system actually overcompensates for this, increasing the amount of oxygenated hemoglobin
(haemoglobin) relative to deoxygenated hemoglobin. Because deoxygenated hemoglobin attenuates the MR signal, the vascular response leads to a signal ______ that is related to the neural activity.

Back 16

oxygen ; increase

Front 17

MRI is used to locate a tumor or fibroid while high energy ultrasound is used to treat it

Back 17

MR-Guided Focus Ultrasound

Front 18

Contrast is achieved by the amount of water (proton) in different organs.

% Water Content of Tissue:
-Grey Matter
-White Matter
-Heart
-Blood
-Bone

Back 18

-Grey Matter 70.6
-White Matter 84.3
-Heart 80
-Blood 93
-Bone 12.2

Front 19

Gadolinium Chelates

• A __ agent
• Make MRI signal _______
• Gadolinium is _____ and needs to be chelated
• However, coordination with at least one _____ molecule is
required
• These chelates contain an ion (Gd+3) with a large number of unpaired electrons (paramagnetic) and therefore a larger ______ ______ than the water proton
• This enhances the local magnetic field, in the vicinity of the proton
• Since this is a small molecule, it would be rapidly cleared by the kidneys
• (short circulating MRI contrast agent)

Back 19

T1
brighter
toxic
water
magnetic moment

*Short-Circulation Agents (Both T1 and T2 agents) are cleared from the body after 1-2 hours

Front 20

These nanoparticles could be engineered to carry multiple _______ _______ on its surface.
PFC- is a ________ which is FDA approved and known to be non-toxic. It is known to be exhaled through the lungs.
These “nanobubbles” are approximately 100 nm is size and are ____ circulating

Back 20

gadolinium chelates ; perfluorocarbon ; long

Front 21

Iron Oxide Nanoparticles

. ____ circulating T2-agent
. It makes the MRI signal _____
. They are superparamagnetic
. They are not magnetic until they are in the presence of an ____ ____ __.
. The induced nanoparticle magnetic field affects the NMR/MRI signal of neighboring water molecules
. They are ____ and ______.

Back 21

- Long
- darker
- external magnetic field (external magnet)
- biodegradable & non-toxic

Front 22

MRI relies on the ____ properties of ____ ____ ____ in water.

Back 22

relaxation ; excited hydrogen nuclei

Front 23

Types of Contrast agents (Image Probes) (3)

Back 23

1) Non specific probe
2) Targeting probe (Drug/NP that has Ab)
3) Activatable probe

Front 24

Discuss Non specific probes

Back 24

Physiology/Morphology

Conventional Contrast

Front 25

Discuss Targeting probes

Back 25

Molecular Signature

High Background

Front 26

Discuss activatable probes

Back 26

Enzymatic activity

Better signal/noise

Front 27

______ _____ – first generation, they are not target specific, they enhanced the MRI or X-ray contrast non specifically by accumulating in a particular tissue

Back 27

Contrast agent

Front 28

_____ ____ _____ – next generation, they specifically target a tissue and can report on the state of a disease. Example: using antibody or peptide that targets
a particular receptor overexpress in cancer or an atherosclerotic plaque

Back 28

Molecular Imaging Agent

Front 29

Activatable Nanoparticles
(when magnetic nanoparticles cluster, the T2 signal _______)

Back 29

decreases

Front 30

This medical imaging technique is based on the acquisition of a large
series of two-dimensional x-ray images taken around a single axis of rotation

Back 30

X-Ray Computed Tomography
(X-Ray CT)

Front 31

For fluorescent imaging – The agent emits a ____ that can be detected

For MRI – The agent _____ the spins of neighboring water molecules

For PET – The agent emits a ______

Back 31

photon

alters (dephases)

positron

Front 32

• One of the most
common imaging
modalities.
• 58 million
examinations a
year in the US
alone
• Adquisition times
are fast

Back 32

Basic X-Ray CT Imager

Front 33

___ will cause coagulation

Back 33

Heat

Front 34

Must use __ nanorods b/c:

Back 34

gold ; they can get excited in near-infared

Front 35

A radioactive material is administered to a patient, then its distribution
and localization is determined by external detectors (scintillation)
The radioactive material can be used for imaging (detection) or therapeutic purposed

Back 35

Nuclear medicine

Front 36

Tumors typically have enhanced _____ ____ to sustain their growth
Therefore, tumors cells typically have a higher number of glucose receptors
and enhanced rate of glycolysis

Back 36

glucose uptake