5.1 Contrast Agents Part 1 Flashcards by Dana Athena Augusto

Contrast Agents introduced in practice by ______,

a Urologist in _____

Moses Swick,

1928

How well did you know this?

Not at all

Perfectly

Any substance that renders an organ or

structure more visible than is possible without its addition

Radiographic Contrast Media

How well did you know this?

Not at all

Perfectly

Allows visualization of structures that
can not be seen well or at all under
normal circumstances

Radiographic Contrast Media

How well did you know this?

Not at all

Perfectly

Substances which help in better

differentiation between adjacent tissues

Radiographic Contrast Media

How well did you know this?

Not at all

Perfectly

Substances which increase beam

attenuation

Radiographic Contrast Media

How well did you know this?

Not at all

Perfectly

Contrast media is needed because:
Soft tissue has a ____
absorption/interaction ratio

low

How well did you know this?

Not at all

Perfectly

Absorption is dependent on

atomic number
atomic density
part thickness
K-shell binding energy (K-edge)

How well did you know this?

Not at all

Perfectly

is the process of absorption

Photoelectric Interaction

How well did you know this?

Not at all

Perfectly

An oral or intravenous administration of a contrast agents is often used to create a _______ between objects

temporary, artificial density difference

How well did you know this?

Not at all

Perfectly

Goal of Contrast Agent

To give different tissues, which would ordinarily have similar attenuations, different attenuation coefficients making them more readily visible on the image

How well did you know this?

Not at all

Perfectly

Types of Contrast Media

Radiopaque/Positive Agent
Radiolucent/Negative Agent
Neutral Agents
Radionuclides

How well did you know this?

Not at all

Perfectly

Higher density than the tissue and absorbs radiation

Radiopaque/Positive Agent

How well did you know this?

Not at all

Perfectly

Contrast agent appears more radiopaque (white) than surrounding tissues

Radiopaque/Positive Agent

How well did you know this?

Not at all

Perfectly

High atomic number

Radiopaque/Positive Agent

How well did you know this?

Not at all

Perfectly

Radiopaque/Positive Agent examples

Barium Sulfate and Iodinated (soluble)

How well did you know this?

Not at all

Perfectly

Lower density than the surrounding tissue

Radiolucent/Negative Agent

How well did you know this?

Not at all

Perfectly

Decrease density

Radiolucent/Negative Agent

How well did you know this?

Not at all

Perfectly

Low atomic number

Radiolucent/Negative Agent

How well did you know this?

Not at all

Perfectly

Organs with contrast agent becomes more radiolucent than surrounding tissues

Radiolucent/Negative Agent

How well did you know this?

Not at all

Perfectly

X-rays penetrate more easily

Radiolucent/Negative Agent

How well did you know this?

Not at all

Perfectly

Radiolucent/Negative Agent examples

Air and Carbon Dioxide

How well did you know this?

Not at all

Perfectly

GI agents possess a density similar to water

Neutral Agents

How well did you know this?

Not at all

Perfectly

Appears similar to surrounding tissues

Neutral Agents

How well did you know this?

Not at all

Perfectly

Neutral Agents example

Water, VoLumen

How well did you know this?

Not at all

Perfectly

low density form of barium sulfate suspension

VoLumen

emits radiation

Radionuclides

used in nuclear medicine

Radionuclides

Common Route of Administration

- Intravascular | - Gastrointestinal

Less Common Route of Administration

- Intrathecally | - Intraarticularly

subarachnoid space surrounding the spinal cord

Intrathecally

directly into a joint space

Intraarticularly

universally used for a variety of radiology examinations

Iodinated Agents

1. Water soluble 2. Easy to administer intravascularly 3. Have a high safety index

has high attenuation compared with human soft tissue, therefore, wherever it distributes it increases the ability of the enhanced structure to attenuate the x-ray beam

Intravascular Contrast Media

two tissues must differ by at least ___ Hounsfield units (HU) to be visibly different on a CT Scan

Proper administration of contrast media can easily provide a ___ HU increase in the natural difference of attenuation between tissues, thus making them visibly different in the image

40-75

Hounsfield Units of Bone

1000

Hounsfield Units of Liver

40 to 60

Hounsfield Units of White Matter

Hounsfield Units of Grey Matter

Hounsfield Units of Blood

Hounsfield Units of Muscle

10 to 40

Hounsfield Units of Kidney

Hounsfield Units of Cerebrospinal Fluid

Hounsfield Units of Water

Hounsfield Units of Fat

-50 to -100

Hounsfield Units of Air

-1000

are not used for their therapeutic qualities, but rather for their distribution and elimination from the body

Iodinated agents

____ of CM differs from other pharmaceuticals

Dose and delivery

Iodinated agent example

Morphine Sulfate

2 to 10 mg diluted in 5 - 15 mL of sterile water | Given at regular intervals of 4 hours

iodinated contrast agents

Bolus injection

100 to 150 mL in less than 1 min

have nearly the same number of particles in solution per unit of liquid as blood

Isotonic

the structural property of a liquid regarding the number of particles in solution, per unit liquid, as compared with blood

Osmolality

Osmolality unit

milliosmoles per kg (mOsm/kg) of water

290 mOsm/kg water

Blood plasma

4-7x the osmolality of blood

High-osmolality Contrast Media (HOCM)

2-3x the osmolality of blood

Low-osmolality Contrast Media (LOCM)

same osmolality as blood

Isosmolar Contrast Media (IOCM)

most brands of iodinated CM have a greater osmolality than blood plasma, therefore most CM are said to be

hyperosmolar/hypertonic solution

older iodinated CM

HOCM

1,300 - 2,140 mOsm/kg

HOCM

Year of LOCM

1980's

600-850 mOsm/kg

Low-osmolality Contrast Media

Year of IOCM

1996

osmolality equal to blood

IOCM

more expensive than LOCM

IOCM

example of IOCM

Visipaque

offer some advantages for patients at risk of renal complications

IOCM (Visipaque)

Year of HOCM

less than 1980's

plays a major role in nonalleregic reactions to CM

Osmolality

a bolus injection of a hypertonic contrast agent causes a _____ in the osmolality of the plasma

rapid increase

The ____ the agent's osmolality, the more pronounced the effects of this increase

higher

physical property that may be described as the thickness or friction of the fluid as it flows

Viscosity

an important quality that will influence the injectability of intravascular agents through small-bore needles and intravenous catheters

Viscosity

affects viscosity

Molecular structure and concentration

different brands of iodinated contrast media will possess ___ viscosities

varying

Increase Iodine Content, ____ Viscosity

Increases

intravascular contrast agents can be classified as to whether the molecules they contain will separate into charged particles (i.e., ions) when dissolved in an aqueous solution

Ionicity

will dissociate into ions when in solution

Ionic contrast agents

do not dissociate

Nonionic contrast media

Although most nonionic contrast also have low osmolality, the two terms are not ____

synonymous

An ____, may be ionic

LOCM | Ex. Hexabrix

once injected, all types of iodinated contrast media undergo very rapid distribution throughout the entire extracellular space

Clearance

iodinated contrast media has a half-life approx. ____

2 hrs.

powder, dissolves in water, oral or rectal, cheaper

Barium Sulfate

liquid, oral or IV, for pediatric patients

Iodinated Contrast Media

oral contrast media is excreted through

Defecation

IV contrast media is excreted through

Urination

Iodinated contrast media excreted by _____ via _____

kidney, | via glomerular filtration

not metabolized

Iodinated contrast media

number of particles in solution

Osmolality

described as the thickness or friction of the fluid as it flows

Viscosity

structural property of intravascular CM

Osmolality

physical property of intravascular CM

Viscosity

molecules that will form ions

Ionic

not synonymous with LOCM

Ionic

molecules do not dissociate

Nonionic

Normal renal function (CM clearance)

2 hours though kidney via glomerular filtration

consider the iodine concentration and the volume

Dose

is directly related to the concentration of iodine

Beam attenuation abilities

measured in mg of iodine per mL (mgI/mL) of solution

LOCM

LOCM examples

- Iopamidol (isovue) - Iohexol (omnipaque) - Iopromide (ultravist) - Ioversol (optiray) - Ioxilan (oxilan)

are labeled in terms of their percent weight per volume

HOCM

HOCM examples

- Diatrizoate sodium/meglumine (Gastrogafin, MD-Gastroview, Cystografin) - Iothalamate sodium/meglumine (Cconray, Cysto-Conray)

Total Iodine Delivered

Volume (mL) x Iodine Concentration (mg I/mL)

The combination of volume and concentration to be used should be individualized accounting for factor such as:

- age - body weight - the size of the vessel into which it will be injected

Other factors include:

- anticipated pathology - degree and extent of opacification required - structure(s) or area to be examined - disease processes affecting the patient - the specific equipment available

CT examinations perform on pediatric patient is calculated by ____

weight

most common formula for pediatric patients

2 mL per kg

the quality of examinations are the ______

same, or better when a weight-based protocol is used

an example of a weight-based calculation for routine body scanning is 1.5 mL/kg (not to exceed ____)

200 mL

there is no proof that contrast agents present a risk to the ____. However, there is not evidence to be certain they pose no risk

fetus