CT Fundamentals (8%)

Question 1

Typical Slice Thickness for Coronary Calcium Scoring.

Answer 1

3mm

Question 2

Can you minimize radiation exposure for Coronary Calcium Scoring by reducing kV?

Answer 2

No. That would change the score.

Question 3

This is the type of triggering used for coronary calcium.

Answer 3

Prospective triggering.

Question 4

Retrospective Helical Gating. Radiation level, Pro, Con.

Answer 4

1. High radiation
2. Pro: Redundant data (average, PVCs, function)
3. Con: Radiation

Question 5

Retrospective Dose modulated Gating.

Answer 5

1. Still high radiation, but save ~30% from full retrospective.
2. Pro; Redundant data
3. Con: Radiation still high

Question 6

4 types of Prospective Gating

Answer 6

1. Helical
2. Step and Shoot
3. Volume
4. Hi Pitch helical

Question 7

What is padding in prospective scan triggering?

Answer 7

scan at prespecified level, then +/- 10%.

Question 8

The prospective gating protocol with lowest radiation exposure.

Answer 8

Hi Pitch helical.

problem is no padding

Question 9

Two methods of scan timing

Answer 9

1. Test bolus (bolus timing)

2. Tracking bolus

Question 10

Typical Peak Tube voltage for normal weight patients.

Answer 10

100 kV

Question 11

Unique artifact with volume gating protocol.

Answer 11

Cone Angle Artifact

Question 12

2 methods to help images with CTA in patient with AF.

Answer 12

1. AF is no issue if single beat acquisition (hi-pitch helical or volume)
2. Retrospective Gating and reconstruct by milliseconds, rather than by percentage
   (also lower the HR as much as possible.)

Question 13

In patients with high heart rate, consider this kind of padding.

Answer 13

Systolic padding. (consider scan acquisition in cardiac systole)

Question 14

Example: 48yom for CACS, BMI 24 (lean patient), HR 65. Best scan protocol (prospective or retrospective) and 100 or 120 keV?

Answer 14

Prospective Gating, 120 keV
120 KeV   (TRICK QUESTION- cant lower the keV for CACS!  only CTA)