AI- rCM Flashcards
what is attenuation a combination of
absorption and scatter
what does att depend on
density/atomic number/thickness of tissue
define what RCM’s do ?
RCM’s artificially adjust the density and atomic number of the structure to increase /decrease x-ray absorption
define more radiolucent (see through image easier) ?
decreasing density and atomic number
define more radiopaque
increasing density and atomic number
requirements for RCM ?
- Easy to administer
- Easily visualised on imaging
- Tolerated by the patient
- Non-toxic
- Rapidly eliminated when necessary
- Cost effective
- Stable compound
- Non-carcinogenic
how can a rcm be administered ? (5 ways)
Orally- gastro-intestinal
(GI) tract
Intravascularly- blood vessel (vein/artery)
Intrathecally- spinal canal
Rectally- rectum
body cavity or joint- uterus, ovarian tube etc
name 3 types of RCM ?
Negative Contrast Media
Barium Sulphate (BaSO4)
Iodinated
what is negative contrast media usually used for ?
Gases used for
GI tract and Bladder imaging
what is barium sulphate used for
usually used for GI tract examinations
what can iodinated be used for
versatile in multiple modalities
(Fluoro, angiography, X-ray and CT)
visibility of organs and blood vessels in medical images, such as X-rays and CT scans
give 2 negative contrast medias
air
co2
give the major facts regarding negative contrast media ?
- All negative contrast agents are
gases - Radiolucent with low atomic
number - Low density
- Attenuate less X-rays than
surrounding tissue, appears
darker on the resultant image
how is air used as an RCM
- inspired or pumped in manually eg- double contrast barium enemma
how is oxygen used an rcm
- introduced into body cavities
how is carbon dioxide used as a rcm
- pumped in during a barium
enema, injected into the colon after the barium liquid to improve the quality of the X-ray
-during angiography
(alternative to iodinated
contrast)
give two examples of positive contrast media
- barium sulpahte iodine- based
main facts regarding positive contrast media
- Radiopaque with higher atomic
number (than body tissues) - High density
- Attenuate more X-rays than
surrounding tissue, appears bright on
the resultant image - E.g.
- Barium Sulphate
- Iodine
properties of barium sulphate
- Predominantly used in Fluoroscopy for GI
tract examinations - White, crystalline compound
- Radiopaque
- Excellent coating properties
- Insoluble – forms suspension in water
- Orally or rectally administered
- Stable
what is double contrast media
- Uses positive AND
negative contrast media
together
iodine rcm properties;
- Iodine based (a.k.a iodinated RCM)
- Colourless liquid
- Radiopaque
- Soluble in water
- Excreted via the kidneys in urine
how can iodine based contrast be administered ? (all 5)
- Oral
- Intravascular (artery or vein)
- Intracavital
- Rectal
- Intrathecal
what is special about iodinated contrast media ?
can be either ionic or non ionic
what differentiates different types of iodinated contrast media
- Physical and chemical characteristics
- Osmolality
- Viscosity
- Iodine Content
why are different types of iodinated contrast media used ?
- Different types used for different body
systems and examinations
state some facts regarding iodinated contrast media (ionic) ?
- Breaks apart (dissociates) when placed in fluid
creating charged particles (ions)
* This increases the number of particles in the
vascular system
BUT…
- Ions that are created can destroy electrical
charges associated with the brain and heart - Disruption is called neurotoxicity
- Considerably toxic
- Higher incidence of patient experiencing
adverse reactions
state some facts regarding iodinated contrast media (non ionic) ?
-Nothing happens when placed in fluid (no
charged particles)
- Low osmolality
- Comparatively less toxic
- Lower incidence of patient experiencing
adverse reactions (3%)
define hypertonic
Solution has HIGHER osmolality (little water) than the
cell, this is called Hypertonic, water moves from cell to solution
how can viscosity affect RCM ?
The viscosity of an RCM can affect the time it takes to
inject
difference between positive and negative contrast media ?
Negative contrast media:
Less opaque than body tissues, and absorbs less radiation than surrounding tissues. Negative contrast media appears darker grey or black than its surroundings on an image.(air,eg)
Positive contrast media:
More opaque than body tissues, and absorbs more radiation than surrounding tissues. Positive contrast media appears white on an image. (barium, iodine)
