5.1 Contrast Agents Part 1 Flashcards
Contrast Agents introduced in practice by ______,
a Urologist in _____
Moses Swick,
1928
Any substance that renders an organ or
structure more visible than is possible without its addition
Radiographic Contrast Media
Allows visualization of structures that
can not be seen well or at all under
normal circumstances
Radiographic Contrast Media
Substances which help in better
differentiation between adjacent tissues
Radiographic Contrast Media
Substances which increase beam
attenuation
Radiographic Contrast Media
Contrast media is needed because:
Soft tissue has a ____
absorption/interaction ratio
low
Absorption is dependent on
- atomic number
- atomic density
- part thickness
- K-shell binding energy (K-edge)
is the process of absorption
Photoelectric Interaction
An oral or intravenous administration of a contrast agents is often used to create a _______ between objects
temporary, artificial density difference
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
Types of Contrast Media
- Radiopaque/Positive Agent
- Radiolucent/Negative Agent
- Neutral Agents
- Radionuclides
Higher density than the tissue and absorbs radiation
Radiopaque/Positive Agent
Contrast agent appears more radiopaque (white) than surrounding tissues
Radiopaque/Positive Agent
High atomic number
Radiopaque/Positive Agent
Radiopaque/Positive Agent examples
Barium Sulfate and Iodinated (soluble)
Lower density than the surrounding tissue
Radiolucent/Negative Agent
Decrease density
Radiolucent/Negative Agent
Low atomic number
Radiolucent/Negative Agent
Organs with contrast agent becomes more radiolucent than surrounding tissues
Radiolucent/Negative Agent
X-rays penetrate more easily
Radiolucent/Negative Agent
Radiolucent/Negative Agent examples
Air and Carbon Dioxide
GI agents possess a density similar to water
Neutral Agents
Appears similar to surrounding tissues
Neutral Agents
Neutral Agents example
Water, VoLumen
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
Iodinated Agents
- Water soluble
- Easy to administer intravascularly
- 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
10
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
46
Hounsfield Units of Grey Matter
43
Hounsfield Units of Blood
40
Hounsfield Units of Muscle
10 to 40
Hounsfield Units of Kidney
30
Hounsfield Units of Cerebrospinal Fluid
15
Hounsfield Units of Water
0
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
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
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