CABT Imaging Systems 4

Question 1

A patient with a pacemaker is referred for imaging. Which modality poses the greatest safety risk?

Accepted Answer

MRI

Answer

The strong static and time-varying magnetic fields in MRI can cause pacemaker malfunction, lead displacement, or device heating, making it the highest-risk modality for most pacemaker patients.

Question 2

In digital subtraction angiography (DSA), the 'mask' image is:

Accepted Answer

A pre-contrast image used to subtract background structures

Answer

In DSA, the mask is a pre-contrast fluoroscopic image; subtracting it from post-contrast images eliminates overlying bone and soft tissue, revealing only the contrast-filled vessels.

Question 3

The modulation transfer function (MTF) of an imaging system describes:

Accepted Answer

How spatial frequencies (detail) are preserved from object to image

Answer

The MTF quantifies what fraction of the true contrast is preserved for each spatial frequency, characterizing the system's spatial resolution performance.

Question 4

Which parameter most directly controls image noise in a CT acquisition?

Accepted Answer

Tube current-time product (mAs)

Answer

mAs (milliampere-seconds) determines the number of X-ray photons reaching the detector; higher mAs reduces quantum noise while increasing patient dose.

Question 5

In echocardiography, the Doppler technique used to measure high-velocity blood flow across a stenotic valve is:

Accepted Answer

Continuous-wave (CW) Doppler

Answer

Continuous-wave Doppler has no aliasing limit and can accurately measure the high velocities (>2 m/s) encountered across stenotic cardiac valves, unlike pulsed-wave Doppler.

(CABT) Certified Associate in Biomedical Technology Practice Test

(CABT) Certified Associate in Biomedical Technology Practice Test

CABT Imaging Systems 4