Question 23M.3.HL.TZ1.14
| Date | May 2023 | Marks available | [Maximum mark: 10] | Reference code | 23M.3.HL.TZ1.14 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Demonstrate, Describe, Draw, Explain | Question number | 14 | Adapted from | N/A |
Describe, in the context of medical diagnosis, how an ultrasound A scan is produced.
[2]
«pulses of» ultrasound are reflected « from organ boundaries» ✓
«depth information is obtained from elapsed» times between transmission and reception of reflected waves ✓
A scan and MRI. The concept of A scan in medical imaging was well understood only by the best students.
The diagram shows a simplified view of the front of a human eye.
A transducer is placed at the cornea and an ultrasound pulse is emitted.
Draw, on the axes, the expected A scan for just the part of the eye shown.
[2]
4 reflected pulses ✓
separated in time and shorter than incident pulse ✓
Allow 3 reflected pulses because there may be little reflection from the front of the cornea due to the gel.
Demonstrate how the A scan in (b)(i) can be used to obtain a value for the thickness of the eye lens.
[2]
by measuring «the half» time «between the 2 pulses to the right» ✓
and multiplying by the speed of sound «in eye lens» ✓
In magnetic resonance imaging (MRI), a patient is exposed to a strong external magnetic field and a radio frequency signal (RF) is emitted towards the patient.
Explain the reason for using the RF signal.
[2]
the RF signal is at the resonant frequency or Larmor frequency of the «precessing» protons ✓
the protons will «absorb the energy and» make a transition to the higher energy / spin down» state ✓
In c), students proved to have some basic ideas about MRI but were not able to explain it in detail.
Describe the subsequent measurements that can be used to distinguish between different types of tissues.
[2]
ALTERNATIVE 1
the time taken for the nuclei to return to their original states/intensity of signal is measured ✓
these are different for different tissues✓
ALTERNATIVE 2
use of the gradient field «allows location of emitted signal» ✓
measured intensity is dependent on different tissues ✓