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CT > IV Procedures And Contrast > Flashcards

IV Procedures And Contrast Flashcards

1
Q

Contrast agent may help with ?

A
  1. Improve the sensitivity and specificity of the clinical diagnosis.
  2. Differentiate anatomical structures on the images
  3. Help to define abnormalities on the images.
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2
Q

Any tissue that is perfused, or penetrated, by contrast agent becomes?

A

More dense

Has an increased ability to attenuate x-ray photons

Correlates with a higher CT number

Will appear brighter on the image

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3
Q

Contrast media that is administered by IV, the tissues that are perfused by the substance include:

A

Blood vessels
Vascular lesions
Abdominal organs

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4
Q

How to opacity the distal GI tract

A

Oral agents administered rectally

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5
Q

For a virtual colonoscopy study, what is administered rectally?

A

Air or CO2

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6
Q

It is ____ in the contrast compounds that is responsible for the increased ability to attenuate x-ray photons.

A

Iodine

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7
Q

Osmolality is the

A

Concentration of molecular particles in solution

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8
Q

LOCM has what range of osmolality

A

500 to 850 mOsm/kg

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9
Q

HOCM has what range of osmolality

A

1,300 to 1,600 mOsm/kg

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10
Q

Blood has what osmolality

A

285 mOsm/kg

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11
Q

In general IV contrast agents are ____ (hyper or hypo-osmolar) solutions, or _____ (hyper- or hypo-tonic), compared to blood plasma.

A

Hyperosmolar

Hypertonic

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12
Q

Hypertonic solutions will cause

A

A net movement of water from within the tissues, into the vascular space.

This can cause dehydration.

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13
Q

Why is it important to ensure the patient is well hydrated before and after the exam?

A

Because the contrast media is hypertonic

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14
Q

Viscocity

A

A measure of the thickness of a liquid, related to the frictional forces of the molecules of the substance as they flow past each other.

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15
Q

A contrast agent will have a high viscocity if it’s…..

A

Molecular particles are large

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16
Q

What is the significance of contrast with high viscocity ?

A
  1. A patient’s tolerance of the force of the injection

2. The kidneys have more difficulty clearing larger molecules from the blood.

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17
Q

Name 11 minor reactions that do not require treatment

A

Nausea, vomiting, chills, warmth, sweating, minor hives, metallic taste, itching, shaking, headaches, dizziness

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18
Q

Moderate reactions, that may require treatment and close observation, but typically not hospitalization 6

A
  1. Moderate hives
  2. Facial edema
  3. Change in pulse rate
  4. Hypo- or hypertension
  5. Wheezing
  6. Bronchospasm or laryngospasm
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19
Q

Some scientists group the mechanisms that cause contrast reactions, into 2 categories called:

A

Chemotoxic

Idiosyncratic

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20
Q

Chemotoxic reaction mechanisms are those that can be directly attributed to factors including:

A
  1. Physiological properties
  2. Total volume injected
  3. Rate of injection
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21
Q

Osmosis

A

Is the process in which the contrast particle draw water toward them and away from body tissue or cells

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22
Q

The rapid movement of fluid through osmosis. Into the blood vessels is believed to be contributed to?

A
  1. Pain associated with vessel dilation
  2. Flushing
  3. Changes to red blood cells
  4. Vascular endothelium damage
  5. Vomiting
  6. Nausea
  7. Dehydration
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23
Q

How can you reduce the viscosity of contrast?

A

Warming it

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24
Q

A high concentration of iodine in the contrast agent leads to

A
  1. Higher osmolality

2. Higher viscosity

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25
Q

Idiosyncratic reaction mechanisms can be caused by

A

Anything other than the properties of he contrast agent, the amount injected, or the injection rate.

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26
Q

Adverse reactions that are allergic in nature, means?

A

The patient’s physiology has trouble tolerating the introduction of a foreign substance. Their body will release histamine

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27
Q

Histamine acts by

A
  1. Constricting smooth muscles and venules
  2. Accelerating heart rate
  3. Lowering blood pressure
  4. Increasing gastric and mucous secretions
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28
Q

What happens when an excessive amount of histamine is released in he body?

A
  1. The vascular system becomes overloaded and histamine passes into th surrounding tissues.
  2. Believed to be responsible for reactions such as hypotension and hives
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29
Q

In order to prevent histamine reactions, you can

A

Pre-medicate with anti-histamine or steroids.

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30
Q

A precaution is?

A

A condition that would warrant a medical decision as to whether the benefits of the exam outweigh the risks posed to the patient.

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31
Q

A contraindication is

A

A condition that would preclude a patient from having a study performed in a given manner.

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32
Q

Contraindication to contrast includes

A

A known hypersensitivity to the compounds (medical history)

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33
Q

Extra caution should be taken with patients with the following precautions

A
  1. Liver or kidney disease
  2. Thyrotoxicosis
    3.myelomatosis
  3. Diabetes
  4. Anuria
  5. Multiple myeloma
  6. Sickle cell disease
  7. Pheochromocytoma
  8. Hyperthyroidism
    10 asthma
  9. Hay fever
  10. Food allergies
  11. Congestive heart disease
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34
Q

In normal patients, how long dose it take for 50% of the injected dose is recovered in the urine?

A

2 hours

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35
Q

In patients with severe renal impairment, how long dose it take for 50% of the injected dose is recovered in the urine?

A

16 to 84 hours.

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36
Q

Generally patients taking metformin, should not take it after IV contrast, because ?

A

To prevent lactic acidosis

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37
Q

Metformin should be resumed only after?

A

Kidney function has been reassessed and determined to be normal.

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38
Q

Patients that take metformin and have renal dysfunction should?

A

Not take metformin and follow-up renal function tests should be performed until metformin can be taken safely.

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39
Q

Advantages of power-injectors

A
  1. Consistent, reproducible flow rate.
  2. Precise volume and dose control.
  3. Optimum contrast enhancement is achieved with higher injection rates
  4. Rates allowed up to 5 or6 ml/sec
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40
Q

What type of needle is not used with a power injector?

A

Butterfly needle
And
Standard PICC lines (peripherally inserted central catheter)

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41
Q

Specially-labeled Power Piccs may be used with a power injector up to what rate?

A

5ml/sec

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42
Q

Routine exams use what injection rates

A

2 to 4 ml/sec

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43
Q

CTA exams use what injection rates

A

4 to 5 ml/sec

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44
Q

Injection rates are determined by

A
  1. Type of scan
  2. Volume of media
  3. IV gauge/pressure capacity
  4. Condition of patient
45
Q

Why is the cephalic vein less desirable to use for IV contrast?

A
  1. It’s tortuous route makes it more likely to be impeded when the arm is raised
46
Q

Why is the basilic vein more desirable to use for IV contrast?

A
  1. It has a more direct route to the axillary vein

2. Because of the anastomosis between the basilic and cephalic veins, the basilic vein remains more stationary.

47
Q

How to distend the vein

A

Apply tourniquet
Patient pump hand
Slap vein
Apply heat

48
Q

Slapping the vein briskly will

A

Double its size, due to reflex vasodilation

49
Q

Using a saline flush, with a dal-head power injector, increases ____ and decreases ____

A

Increases the contrast boils and can decrease both contrast usage and radiation dose to the patient.

50
Q

What venipuncture and contrast administration details should be recorded in the patient records?

A 
The injection site
Number of venipuncture attempts
Gauge of the catheter
Amount of contrast
Concentration of contrast
Rate of contrast injection
51
Q

If ______ of contrast media is injected into soft tissue, surgical consult is recommended

A

Over 100 ml

52
Q

Venous air emboli appear, how on images?

A

As dark bubbles o air in the most anterior aspects of contrast filled vessels and heart chambers.

53
Q

Signs and symptoms of larger air emboli include

A 
SOB
Chest pain
Hypotension
Paralysis 
Seizures
54
Q

Small to medium air emboli usually

A

Don’t need treatment
Close observation
Documentation of occurrence

55
Q

Larger air emboli require

A

Placing patient in the left lateral decubitus position.
Head angled down 30 to 40 degrees.
100% oxygen administered

56
Q

What does the required treatment, for larger air emboli do?

A

Allows air bubbles to rise to the apex of the right ventricle and prevents them from entering the pulmonary vascular system.

57
Q

If the scan is started too late?

A

The organs and lesions will both enhance.

58
Q

The 3 phases of tissue enhancement

A
  1. Bolus phase
  2. Non-equilibrium phase
  3. Equilibrium phase
59
Q

The amount of time that each phase take is directly related to?

A

The injection rate

The volume of injection

The velocity of the blood flow

60
Q

What happens following the injection?

A

The contrast bolus:
1. Travels through the veins, to the right side of heart.

  1. Passes through lungs
  2. Into the left side of heart
  3. Into the arterial system, starting with the aorta.
  4. Ultimately returns to the heart, via the veins. At this point the contrast bolus is moderately dispersed.
61
Q

The bolus phase of enhancement begins

A

Just after the contrast is injected.

62
Q

The bolus phase is defined by

A

A significant density difference between the abdominal aorta and the inferior vena cava.

63
Q

During the bolus phase, the bolus moves

A

Through the arteries and away from the heart. It is at this time that CTA images are optimal in quality.

64
Q

The non-equilibrium phase is characterized by

A

A 10-30 HU density difference between the abdominal aorta and the inferior vena cava.

65
Q

During the non-equilibrium phase, the bolus starts to

A

Disperse into the capillaries, then into the veins.

As a result, the density difference between the abdominal aorta and the IVC decreases.

66
Q

It is typically during the non-equilibrium phase that we obtain the best

A

Differentiation of structures in the soft tissues.

67
Q

The equilibrium phase is characterized by

A

A density difference of less than 10 HU between the abdominal aorta and the IVC.

68
Q

During the equilibrium phases, the contrast agent’s concentration in the veins

A

Becomes similar to the concentration in the arteries.

69
Q

During the equilibrium phase, soft tissue structures’ differentiation

A

Becomes diminished .

70
Q

The liver is the only organ with a dual blood supply

A

80% from the portal vein

20% from the hepatic artery

71
Q

When the contrast perfuses the liver, the enhancement occurs from

A

Each of the 2 sources at different times.

72
Q

The hepatic arterial phase occurs around

A

20 to 40 seconds are the start of injection.

73
Q

The portal venous phase occurs approximately

A

60 to 90 seconds after the start of the injection

74
Q

Most tumors in the liver are ___ vascular than the liver and will most obvious during?

A

Less vascular

Portal venous phase

75
Q

A smaller set of hepatic tumors are more vascular than the liver, and can be seen when?

A

During the hepatic arterial phase.

76
Q

CTA examinations require precise timing to ensure

A

That the contrast media passes though the desired vessels during the exact time that the scan is done.

77
Q

Brain scan for what diseases, require delayed scans?

A

MS
Metastatic lesions
AIDS-related abnormalities

78
Q

Abdomen scan for what diseases, require delayed scans?

A

Cholangiosarcoma
Fibrolamellar carcinoma
Adrenal tumors

79
Q

Pelvic scan for what diseases, require delayed scans?

A

Cancer of the probate, ovaries, or uterus

80
Q

Why do you need to factor in a delay after the start of injection, prior to using a helical scan?

A

If a helical scan was started immediately after the injection, many of the images would be acquired during the bolus phase.

With a delay, the helical scan can be completed during the non-equilibrium phase.

81
Q

Why do you need to factor in a delay after the start of injection, for Multi-row detector scanners, versus a single-row detector scanner?

A

This is so the scan does not finish before the contras media has passed through the tissue of interest.

82
Q

If a patient what 2 conditions,using the standard delay times would not work.

A

Poor cardiac output
Or
Patient is in shock

83
Q

How is a test bolus used?

A

A test bolus is given before the actual scan is done.

With this morbid, several slices are collected at the same slice position over a short period of time to monitor the arrival of the contrast.

On all of the images a ROI is drawn over the enhancing vessel.

Scanner software can then calculate he arrival time of the contrast.

After the test is completed, the actual injection and scan are performed, using the delay time that was determined.

84
Q

Many scanners are equipped with _____ that senses how long it takes for a boys of contrast to reach the region of interest

A

Automated software

85
Q

The pacification caused by oral contrast is needed in order to

A
  1. Reduce the risk of misdiagnosing fluid-filled bowel, as an abscess or tumor.
  2. Helps to visualize if a lesion is exterior to the bowel or if it is infiltrating the bowel.
86
Q

2 categories of oral contrast media

A
  1. Barium sulfate

2. Iodinated

87
Q

In an effort to visualize the gastric wall thickness and detect gastric tumors, some physicians elect to

A
  1. Distend the stomach with air or gas.

In such cases, glucagon can be given to inhibit gastric peristalsis.

  1. After consuming oral contrast, a pt swallows a final dose of water. This keeps he gastric contents from being opacified.
88
Q

In cases of genera abdominal pain, ____ may be used as an oral contrast agent.

A

Water

89
Q

Since the barium solution’s high density causes sever streak artifacts in CT, what is used?

A

Barium sulfate solutions containing a 1 to 3% barium suspension

90
Q

Characteristics of barium sulfate

A

Inert
Insoluble substance
Passes through GI unchanged

91
Q

The most frequent adverse reactions to BaSO4 is

A

Diarrhea

Abdominal cramping

92
Q

Rare adverse reactions to BaSO4 are

A 
Colon impact ion
Barium granuloma
Barium appendicitis
Intestinal perforation
Peritonitis
93
Q

Allergic reactions to barium sulfate are more likely in patients

A

Who are atopic and those with previous history of allergic symptoms.

94
Q

Atopic

A

denoting a form of allergy in which a hypersensitivity reaction such as dermatitis or asthma may occur in a part of the body not in contact with the allergen.

95
Q

Contraindications to using barium sulfate solutions include

A
  1. Colon obstruction or perforation
  2. Tracheosophageal fistula
  3. Obstructing lesions of the small intestine
  4. Pyloric stenosis
  5. Hypersensitive to barium sulfate
96
Q

For an abdominal study most patient drink ___ of barium sulfate ____ prior to exam

A

750ml

1 hour

97
Q

For an abdominal and pelvic study most patient drink ___ of barium sulfate ____ prior to exam

A

1,500 ml

2 hours

98
Q

How to prepare the patient that is getting barium via rectum

A

1 warmed to body temperature

2. Patient should be rolled 360 degrees, to coat al surfaces

99
Q

To evaluate Crohn’s disease and for CT enterography

A

There is a very low concentration of barium sulfate

2,000ml consumed 90 minutes prior to exam

100
Q

Concentration of iodinated oral contrast is

A

6 to 9 mg of iodine per ml

101
Q

Iodinated oral contrast agents are used when

A

Barium sulfate agents are contraindicated

102
Q

Iodinated agents are absorbed by the GI tract, by what percent?

A

0.1 to 0.5% absorption occurs

103
Q

Disadvantage of iodinated oral agents

A

Significant dilution of the agent occurs due to the movement of water into the bowel.

Opacification of the distal bowel may be difficult.

104
Q

Water soluble iodinated contrast pass through the GI tract in ____ hours.

A

2

105
Q

Having the patient NPO for _____ prior to the exam will help to improve opacification in the distal bowel.

A

Minimum of 4 hours.

106
Q

Contraindications to iodinated oral contrast is similar to the IV, except for

A

If there is a risk of aspiration. Do not use

107
Q

Aspiration of iodinated agents can result in

A

Severe pulmonary edema

108
Q

Common reactions to iodinated oral agents are similar to those of barium sulfate agents:

A

Mild diarrhea
Abdominal pain
Flatulence

109
Q

Procedures for Post-Myelographic CT

A
  1. Elevate head: reduces risk of headache and seizures.
  2. Confirm density of contrast media: if scan is more than 4 hours after injection, the density will be reduced too much.
  3. Ensure that the contrast has not separated from the CSF: Either roll the patient before the scan of by scanning the patient in a prone position.

CT (9 decks)

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