Unit 1 Flashcards
Higher atomic number means….
More x-ray absorption
Calcium (bone) has a high or low atomic number?
High
Soft tissue has a high or low atomic number?
Low (more matter more scatter)
What is Contrast Media?
Contrast media are diagnostic agents that are instilled into the body orifices or injected into the vascular system, joints, and ducts to enhance subject contrast in anatomic areas where low subject contrast exists
State the purpose of contrast media
The purpose is to provide a more significant distinction between adjacent anatomical structures
or in other words (from the book)….
anatomic detail to be visualized, its ability to distinguish between radiographic densities enables differences in anatomic tissues to be visualized.
What factors affect the degree of radiographic density differences?
- Absorption characteristics of the tissues that comprise the anatomic part
- Technical factors used
- Characteristics of the image receptor
- Automatic image processing
- The use of contrast media agents
What is the term:
Atomic Numbers
Numbers of photons in the nuclei of the different elements
What is the term:
Bronchospasm
Involuntary constriction of the bronchial tubes usually resulting from an immune system reaction to a foreign particle or molecule
What is the term:
Contraindications
Factors of a patient’s history or present status that indicate that a medical procedure should not be performed or that a medication should not be given
What is the term:
Creatinine
Nitrogen-containing waste products of metabolism excreted by the kidneys filtration system; high blood plasma levels indicate poor filtration by the kidney
What is the term:
Extravasation
Leakage from a vessel into the tissue
What is the term:
Flocculation
Formation of flaky masses resulting from precipitation or coming out of a suspension or solution
What is the term:
Osmolality
Measurement of the number of particles (molecules or ions or cations) that can crowd out water molecules in a measured mass (kilogram) of water
What is the term:
Osmosis
Movement of water from an area of high concentration to an area of low concentration through a semipermeable membrane such as blood vessel walls and cell membrane
What is the term:
Shock
Inadequate blood flow within the body with resulting loss of oxygen and therefore energy
What is the term:
Solution
Uniform mixture of two or more substances composed of molecule-sized particles that do not react together chemically
What is the term:
Suspension
Nonuniform mixture of two or more substances, one of which is composed of larger than molecule size particles that have a tendency to cluster together
Contrast media are generally classified as….
negative or positive contrast agents
Negative Contrast Agent
Allows x-ray photons to penetrate the medium easily
Ex: air (gas)
Positive Contrast Agent
Will absorb most (more) of the x-ray photons leading to a radiopaque appearance on the produced images
What are 3 types of contrast agents?
Radiolucent (negative), Radiopaque (positive), & Specialty Contrast Agents (US & MRI)
Radiolucent (negative) contrast media
X-ray photons are easily transmitted or scattered through radiolucent contrast media. These media are relatively lucent to x-rays. The anatomic areas filled by these agents appear dark (increased density) on radiographs. These media care composed of elements with low atomic numbers.
Radiopaque (positive) contrast media
X-ray photons are absorbed by radiopaque contrast media because these media are opaque to x-rays. The anatomic areas filled by these agents appear light (decreased density) on radiographs. These media are composed of elements with high atomic numbers
What are the five radiographic densities?
- Air (gas)
- Fat
- Water
- Mineral (contrast)
- Metal (Markers)
What is the difference between negative and positive contrast material?
Negative contrast is composed of low atomic number elements which appears radiolucent on an image, whereas positive contrast is composed of higher atomic number elements which appears radiopaque on an image (absorbs more radiation)
What are some specialty contrast agents?
Ultrasound (soundwaves - microbubbles)
&
MR scanning (uses magnetic energy - gadolinium & NSF: nephrogenic systemic fibrosis)
What is optimal contrast material?
- Very-high contrast visualization (makes it easy to visualize)
- Extremely low toxicity to patient
- Persistence in patient anatomy until imaging is completed
- Low cost
- Minimal or no side effects
- No residual effects within patient
What are key contrast characteristics?
- Ability of agent to mix with body fluids (uniform appearance)
- Viscosity
- Ionic Strength (want to avoid)
- Persistence in the body
- Iodine content
- Osmolality (Vital)
- Potential for toxicity (could be toxic)
What are some radiographic contrast media choices?
(Primary)
-
Barium
- Atomic number 56
-
Iodine
- Atomic number 53
The higher atomic number = more radiation = more white on the image
(Other choices that are not as common)
- Air/gas
- Average atomic number 8
- Carbon Dioxide
- Room air
- Average atomic number 8
Lower atomic number = absorbs less radiation = more darker on the image
Barium studies of the GI tract can use what two types of contrast?
Single contrast (contrast only)
OR
Double contrast (barium + air)
Is barium sulfate water soluble or not water soluble?
Barium sulfate is not water soluble!
What factors should you consider when giving contrast (barium) to a patient?
- Age (ability to communicate/follow directions + increase risk for colon perforation cause by loss of tissue tone)
- Diverticulitis or Ulcerative Colitis (increase difficulty holding enema + increase risk for colon perforation)
- Long-term steroid therapy (increase risk for colon perforation)
- Colon biopsy within previous 2 weeks (Lower gastrointestinal series contraindicated)
- Pregnancy (inform before proceeding)
- Mental retardation, confusion, or dizziness (increase risk for aspiration during upper gastrointestinal series)
- Recent onset of constipation or diarrhea (increase risk for colon perforation or tumor rupture)
- Nausea & vomiting (increase risk for aspiration during upper gastrointestinal series)
What are 5 important things to know about contrast media?
- Human tissues inherently have low subject contrast (visualize anatomy normally not seen)
- Takes advantage of the photoelectric effect and high-atomic number elements
- Requires the administration of media into patient (contrast is classified as a drug)
- Requires attention to indications and contraindications (when is it safe to use contrast considering a patient’s medical history)
- Warrants serious attention to patient reaction
What is the term:
Compound
Substance composed of two or more elements combined in definite ratios that give the substance specific properties
What is the term:
Ionic
Atom or molecule having a negative charge (anion) or positive charge (cation)
What are 2 important things to know about ionic contrast agents?
- Uses iodine as the contrast molecule (iodine atomic number of 53 - excellent positive contrast agent) (tri-iodinated)
- Dissociates into two ions: Anion (-) & Cation (+)
Ionic contrast agents dissociates into what two ions?
Anion ( - )
Cation ( + )
What does anion and cation eventually do regarding contrast?
Eventually joins with carbon atoms or a combination of atoms (these combinations affect how the body excretes the contrast and the osmotic effects of the contrast)
What does anion do regarding contrast?
Joins other carbon atoms to form a 3 ionized atom termed tri-ionated
What are 5 important things to know about osmolality?
- The measure of the total number of particles in solution per kilogram of water.
- Great biological significance.
- Most adverse reactions to contrast result from the osmolality of the agent (dangerous to utilize) (increase number of particles).
- Nonionic contrast agents are typically LOCM and do not contain ions (primary contrast agent used today).
- High osmotic contrast has an increase number of particles in the solution such as blood plasma. The particle pulls water towards them which affect the osmotic pressure within the body.
What are 3 important things to know about nonionic contrast agents?
- Too big to have a osmotic effect on the body giving these types of contrast the designation of lower osmolality contrast media.
- Does not break down into anions or cations but can be dissolved by water (even with the larger molecules making it safer to inject into the bloodstream) the body can filter and discrete the contrast.
- Water soluble
What are the advantages of nonionic, LOCM?
- Nonionic contrast is safer because it has a lower osmolality pressure therefore does not draw water into the molecular components like ionic contrast.
- Nonionic breakdown and less toxic at cellular level (does less damage to the body than ionic contrast)
- Warmed to increase viscosity, although this is not typically used anymore but the contrast can be thick which is why they warm it to reduce thickness.
- Less likely to cause patient reaction
- More tolerable by patients
- High contrast effect resulting from number of iodine atoms per molecule.
What is the term:
Blood Urea Nitrogen (BUN)
BUN test can reveal whether the urea nitrogen levels are higher than normal, suggesting that the kidneys or liver may not be working properly
What are some general effects of water soluble ionic contrast agents?
- Most contrast reactions occur relating to osmolality
- Dehydrated patients are vulnerable to hypovolemic shock (could be critical for the patient)
- Greater the number of particles in a contrast agent, the more molecules there are to pull water from the patient
- Expressed as milliosmoles per kilogram of water at 37 degrees C
What are some considerations to think about when giving contrast?
- Patient history - allergies, asthma, diabetes, diseases or general health problems.
- Renal function (most important) kidneys are responsible for filtering out the contrast agent and removing it from bloodstream.
- BUN (if kidneys are not functioning, contrast can damage them)
- Creatinine also a waste product of metabolism.
- Metformin (glucophage) should be discontinued for 48 hours before and 48 hours after the use of iodine contrast media.
(contrast enhanced CT studies)
What are some anaphylactoid reactions?
- Urticaria (hives)
- Wheezing
- Throat swelling (edema)
- Bronchospasm (involuntary constriction of the bronchial tubes)
- Nausea
- Vomiting
- Cardiac arrest
Contrast Reactions
- Generally occur within the first (5) minute(s) of injection
- Can be unpredictable
- Mild reaction may worsen to severe at any time
- Reaction is different from a side effect
Monitor patient continually!
MILD REACTION - signs and symptoms
Nausea
Vomiting
Cough
Warm Feeling
Headache
Dizziness
Shaking
Itching
Strange taste in mouth
Pallor (patient color)
Flushing chills
Sweats
Urticaria (hives)
Nasal stuffiness
Swelling about the eyes and face
Anxiety (nervousness)
MODERATE REACTION - signs and symptoms
Tachycardia
Bradycardia
Hypertension
Pronounced cutaneous reaction
Hypotension
Dyspnea
Bronchospasm
Wheezing
Laryngeal Edema
SEVERE REACTION - signs and symptoms
Laryngeal edema
Convulsions
Profound Hypotension
Cardiac arrhythmias
Unresponsiveness
Cardiac arrest
What are some health professional responsibilities when administering contrast agents?
- Administered under the supervision of a licensed physician with proper qualifications.
- Patient assessment and history
- Patient comfort and education
- Recognize signs and symptoms of reaction and act appropriately
- Patient care and surveillance
- Post exam considerations for patient
- Remain calm and reassuring during procedures
What are the routine projections for sacrum and coccyx?
AP or PA Axial Sacrum
Lateral Sacrum
AP or PA Axial Coccyx
Lateral Coccyx
How many segments does the coccyx have?
Why isn’t there specific number of segments?
Consists of 3-5 segments
There isn’t a specific number of segments because each person is different so one person might have 3 segments and other could have 4 or 5 segments, depends on how they were born.
What angle should the coccyx have for an AP Axial projection?
10 degrees Caudal
What angle should the sacrum have for an AP Axial projection?
15 degree Cephalic
What angle should the coccyx have for an PA Axial projection?
10 degrees Cephalic
What angle should the sacrum have for an PA Axial projection?
15 degrees Caudal
Name the anatomy that is circled in green on the coccyx
- Base
- Apex
Describe the patient position for a AP or PA Sacrum Axial Projection
The patient is positioned supine for the AP Axial projection and prone for the PA Axial projection. The patient should be adjusted so both ASIS are equal distance from the IR