Ultrasound

Question 1

What can eFAST be used to diagnose?

Answer 1

Pneumothorax
Pericardial effusion
Abdominal free fluid

Question 2

Sensitivity and specificity of abdominal free fluid on eFAST?

Answer 2

Sensitivity ~85% (need 200 cc of free fluid)

Specificity 99% (false positives 2/2 ascites, urine, diasylate)

Somewhat dependent on operator and body habitus
Cannot see retroperitoneal space

Question 3

Sensitivity and specificity of pneumothorax on eFAST?

Answer 3

98%; 99%

Question 4

eFAST algorithm?

Answer 4

If stable:
+eFAST - CT
-eFAST - CT or Obs

If unstable:
+eFAST - OR
-eFAST - ?? (think of other causes)

Question 5

Which probe is low frequency? Which probe is high frequency?

Answer 5

Low: curvilinear

High: linear

Question 6

Which probe is used in the abdominal vs. cardiac vs. thoracic cavity windows?

Answer 6

Curvilinear: abdominal and cardiac

Linear: thoracic cavity

Question 7

Compare the resolution and penetration of the curvilinear vs. linear probes.

Answer 7

Curvilinear has improved penetration (30 cm), but less resolution

Linear has less penetration (6 cm) but higher resolution

Question 8

How should a trauma patient be positioned?

Answer 8

Backboard/supine, with C-spine immobilization

Question 9

Why is supine position helpful for eFAST? Why is Trendelenberg helpful?

Answer 9

Supine: creates dependent areas, detect pooled blood

Trendelenberg: improves sensitivity of exam

Question 10

Describe probe positioning for thoracic windows.

Answer 10

2nd ICS at MCL, march probe down
~5 respiratory cycles
Indicator up, sagittal view
M-mode (motion mode)

Question 11

Normal thoracic view in M-mode?

Answer 11

Seashore sign (like waves on a normal beach) = normal movement of the chest wall

Question 12

Pneumothorax in M-mode?

Answer 12

Bar code sign (not wavy at all)

Question 13

Describe probe positioning for the RUQ window.

Answer 13

Hepatorenal space/Morison pouch
Midaxillary line of R flank
Indicator up, oblique and coronal views
Diaphragm to lower pole kidney

Question 14

Describe probe positioning for the cardiac windows.

Answer 14

Sub-xiphoid AND parasternal long axis (back-up, best done with a different probe)

Indicator to patient’s right
Point probe to patient’s left shoulder
Just to the right of midline

Question 15

Describe probe positioning for the LUQ window.

Answer 15

Splenorenal space
Indicator up
Coronal view
More posterior than you think

Question 16

Why is it important to be appropriately posterior in the LUQ window?

Answer 16

Liquid in the stomach can be mistaken for free fluid

Question 17

Describe probe positioning for the suprapubic window.

Answer 17

Rectovesicular space
Rectouterine space (Pouch of Douglas)
Sagittal and transverse views

Question 18

Define velocity.

Answer 18

Speed of US wave, assumed to be constant (translates to depth -> the faster the waves return, the closer the tissue is located)

Question 19

Define frequency.

Answer 19

Lower frequency -> achieve better images of deeper structures

Higher frequency -> achieve better images over shorter images

Question 20

Define amplitude.

Answer 20

Intensity of US wave; constant, independent of frequency.

Question 21

Hyperechoic = ___ amplitude

Answer 21

High

Question 22

Hypoechoic = ___ amplitude

Answer 22

Low

Question 23

2 primary factors contributing to attenuation in US?

Answer 23

Absorption (soft tissue, variable depending on tissue)

Reflection (bone and air -> acoustic shadowing)

Question 24

Tissues with high attenuation coefficient

Answer 24

Gas
Bone

Decrease amplitude

Question 25

Tissues with low attenuation coefficient

Answer 25

Fluid

Minimal effect on amplitude

Question 26

What are lateral and axial resolution?

Answer 26

Lateral - ability to distinguish objects side by side

Axial - ability to distinguish objects above and below each other

Question 27

3 types of probes with most machines?

Answer 27

1. High frequency linear (aka vascular probe)
2. Phased array
3. Low frequency curvilinear (aka abdominal probe)

Question 28

3 planes of US scans?

Answer 28

1. Transverse (axial) - horizontal, L to R scans, indicator to R side
2. Longitudinal (sagittal) - vertical, top to bottom scans, indicator to head
3. Coronal - probe on patient’s side, vertical cuts, indicator to head