Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Diagnostic M.'s Sara Peer mentor > CT Imaging for the PA > Flashcards

CT Imaging for the PA Flashcards

(64 cards)

Start Studying
1
Q

What is a CT?

A

Computed Tomography

Used gantry with rotating xray beam and multiple detectors in various arrays along with sophisticated computer algorithms to process the data

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What does a CT scan produce?

A

large number of 2D, slicelike images each of which are millimeters in diameter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the two major types of CT?

A

Helical

Conventional, Axial, Step and Shoot CT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a conventional, axial, Step and shoot CT used for?

A

high-resolution scanning of lungs, coronary artery calcium scoring, and prospective ECG-triggered coronary CT angiography

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the principal components of a CT machine?

A

xray tube

diametrically opposed array of detectors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What does collimation determine?

A

thickness of a section

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the standard chest collimation for mediastinum?

A

2.5 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the standard chest collimation for lung parenchyma?

A

1.25 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is narrow collimation?

A

1 to 1.25 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is narrow collimation used for?

A

CT pulmonary angiography
high resolution CT scanning of the lung parenchyma
imaging of small pulmonary nodules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is wide collimation?

A

2.5 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is wide collimation used for?

A

heavy patients to decrease the quantum noise at the cost of decreased spatial resolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a CT image composed of?

A

matrix of thousands of tiny squares called pixels which are computer assigned a Hounsfield Number

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the Hounsfield number?

A

a measure of how much of the xray beam is absorbed by the tissues at each point in the scan

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the Hounsfield number of air?

A

-1000HU

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the Hounsfield number of fat?

A

-40 to -100 HU

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the Hounsfield number of water?

A

0 HU

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the Hounsfield number of soft tissue?

A

20 to 100 HU

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the Hounsfield number of bone?

A

400-600 HU

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the Hounsfield number of metal?

A

> 1000 HU

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the characteristics of Denser substances on a CT?

A

absorb more xrays
have high CT numbers
demonstrate increased attenuation
displayed as whiter densities on CT scans

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are the characteristics of less dense substances?

A

absorb fewer xrays
have low CT numbers
said to demonstrate decreased attenuation
displayed as blacker densities on CT scans

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is attenuation?

A

the chemical make up of the material; determined by how many xrays make it through the patient to hit the detector and what the image looks like

stopping of xrays

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What can a CT image do after it has been taken?

A

the image can be post processed to optimize visibility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What type of imaging is a CT image?
structural; represents a moment in time
26
What is a CT used to rule out?
Tumors Trauma Infections bleeding
27
What are the limitations of a CT?
``` Size of patient - 500 lb max Girth Claustrophobia Hold still for extended period of time hold breath for extended period of time Contrast usually needed ```
28
What is girth?
camera cannot touch patients arms or sides
29
What are the risks of using contrast?
acute adverse reaction | contrast-induced nephropathy (CIN)
30
What are the methods for contrast administration?
IV Enteric = PO or rectal Intraarticular
31
What is the base for all modern CT contrast?
iodine
32
What are the types of CT contrast?
Low osmolality contrast media (LOCM) Iso-osmolarity contrast media (IOCM) High osmolarity contrast media (HOCM)
33
What is positive enteric contrast?
High attenuation on CT Consists of dilute suspension of Barium sulfate or dilute solution of an iodinated agent Used for most indications
34
What is negative enteric contrast?
water attenuation on CT used to delineate the bowel mucosa used to improve detection of active inflammation or active GI bleeding
35
What can be used a negative contrast?
plain water
36
What resource is available to determine what type of contrast administration to use?
The American College of Radiology's Appropriateness Criteria
37
When would you use IV contrast for Head CT?
``` neoplasm meningitis encephalitis focal neurologic deficit orbital/vision disorders pituitary imaging complicated sinonasal disease seizures Ct angiography ```
38
When would you NOT used IV contrast for Head CT?
head trauma acute stroke Intracranial hemorrhage
39
When would you use IV contrast for Cervical Spine CT?
cervical mass/lymphadenopathy suspected tumor or infection abnormalities of cranial nn. X, XI, and XII brachial plexopathy
40
When would you NOT use IV contrast for Cervical Spine CT?
Trauma; unless possible arterial injury or mechanism of injury is penetrating
41
When would you use IV contrast for Cardiothoracic CT?
evaluating heart and thoracic vessels trauma for staging primary thoracic neoplasms
42
When would you NOT use IV contrast for Cardiothoracic CT?
coronary calcium scoring pulmonary parenchymal evaluation Lymph node evaluation
43
When would you use IV contrast for Abdominopelvic CT?
Gi Hepatopancreaticobiliary GU GYN
44
When would you NOT use IV contrast for Abdominopelvic CT
CT colonography renal stone evaluation extraparenchymal lymphoma
45
When would you use IV contrast for musculoskeletal CT?
evaluation of soft tissue masses evaluation of suspected septic arthritis evaluation of infected prostheses
46
When would you NOT use IV contrast for musculoskeletal CT?
for most CT exams: extremities spine
47
When would you use IV contrast for angiography CT?
evaluating lumen of an artery, vein, or a pseudoaneurysm assess for end-organ ischemia outside brain or lung to eval for PE to detect active bleeding
48
When would you NOT use contrast for angiography CT?
monitoring a known aneurysm for growth | for detection of a hematoma
49
When would you use Oral contrast for CT?
Eval gastric/small bowel perforation following trauma or surgery Helps separate bowel loops in thin patients with minimal visceral fat Improve delineation of bowel from mesentery and other peritoneal content
50
When would you NOT use oral contrast for CT?
``` accurate diagnosis of appendicitis and diverticulitis Eval of: liver kidneys collecting systems bladder spleen adrenal glands retroperitoneum bones vasculature ```
51
When is negative enteric contrast helpful?
detecting occult GI bleeding when paired with multiphasic CT angiography
52
When would you use rectal contrast for CT?
detection of rectal or distal colonic leak
53
When would you NOT use rectal contrast for CT?
basically never
54
What are the contraindications for enteric contrast?
in patients at risk of aspiration eval patients with suspected high grade bowel obstruction avoid barium based in patients who have/at risk for bowel perforations or leak from surgical anastomosis
55
What are not cross reactive?
Gadolinium for MRI and CT contrast
56
When will Adverse reactions to CT contrast occur?
after enteric, intracavitary or intravascular administration
57
When is the incidence of acute adverse reaction greatest?
when IV administration of HOCM
58
What is a mild reaction to CT contrast?
self limited does not progress rarely requires treatment
59
What is a moderate reaction to CT contrast?
requires treatment | may progress to a severe reaction if untreated
60
What is a severe reaction to CT contrast?
life threatening | can cause significant morbidity
61
What are allergic like reactions to CT contrast?
idiosyncratic- not related to dose may occur in patient w/o history of prior exposure do not predictably recur after each antigen exposure
62
What are the signs and symptoms of an allergic like reaction to CT contrast?
``` itching urticaria Erythema Stridor Hoarseness Bronchospasm Anaphylactoid shock ```
63
What are physiologic reactions to CT contrast?
dose dependent | not mitigated by corticosteroid prophylaxis
64
What are the signs and symptoms of physiologic reaction to CT contrast?
``` transient warmth or chills nausea vomiting metallic taste arrhythmia hypertension vasovagal reaction ```

Diagnostic M.'s Sara Peer mentor (27 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions