3) Radiation Measurements and Units

1.

A patient has an abdominal CT scan. The scan range is 30 cm. If the scan is repeated with a scan range of 40 cm. The dose will:

A) Decrease

B) Remain the same

C) Increase

Answer:

B) Remain the same

dose is in units of energy/kg so presumably the extra 10 cm of exposed tissue had the same "dose"

2.

A patient has an abdominal CT scan. The scan range is 30 cm. If the scan is repeated with a scan range of 40 cm. The equivalent dose will:

A) Decrease

B) Remain the same

C) Increase

Answer:

B) Remain the same

3.

A patient has an abdominal CT scan. The scan range is 30 cm. If the scan is repeated with a scan range of 40 cm. The effective dose will:

A) Decrease

B) Remain the same

C) Increase

Answer:

C) Increase

4.

When a signal drops in intensity by a factor of 100 the loss in dB would be:

A) 1

B) 2

C) 10

D) 100

Answer:

B) 2

dB is a logarithmic scale, 2 dB or 102 is a factor of 100

5.

Which of the following is one of the fundamental units in the SI system?

A) sievert

B) rayl

C) joule

D) second

Answer:

D) second (the others are derived units)

6.

In Hounsfield units, the number zero denotes

A) Air

B) Fat

C) Water

D) Bone

Answer:

C) Water

7.

As an ultrasound beam penetrates into a patient the pressures created by the beam are reduced. These are measured in

A) joules

B) watts

C) grays

D) pascals

Answer:

D) pascals

8.

The ultrasound energy deposited in the patient is best measured in:

A) joules

B) watts

C) grays

D) pascals

Answer:

A) joules

9.

During an MR scan there is a concern about the amount of energy that is being delivered to the tissue. The rate the energy is being delivered is measured in:

A) watts

B) joules

C) grays

D) sieverts

Answer:

A) watts

10.

What is the appropriate unit for measuring the amount of visible light falling on a surface?

A) joule

B) watt

C) lux

D) candela

Answer:

C) lux

11.

The unit used to measure dose is the

A) joule

B) gray

C) sievert

D) Roentgen

Answer:B) gray

12.

The unit used to measure equivalent dose is the

A) joule

B) gray

C) sievert

D) roentgen

Answer:

C) sievert

13.

The unit used to measure effective dose is the

A) joule

B) gray

C) sievert

D) Roentgen

Answer:

C) sievert

14.

Pressure in ultrasound is measured in

A) pascals

B) watts

C) joules

D) rayls

Answer:

A) pascals

15.

Even though it is not a SI unit energy is frequently measured in

A) joules

B) gray

C) keV

D) Lamberts

Answer:

C) keV