Mersey Exam Tutorial

Question 2

Distribution of Qs

MCQs can be divided into 4 types of question:
1) Data accuracy
➢ is this quantitative data correct?

2) Comparison
➢ Which of the 2 examples is larger/smaller etc

Answer 2

3) Reflective
➢ Is the definition of a parameter correct?
➢ Identifying specific features of a process

4) Consequential
➢ What are the consequences of changing a parameter?
MCQs will often be a mixture of these types

Question 3

Types of questions

Answer 3

Question 4

“Data Accuracy” MCQ

• Tend to occur on questions relating to (ie you must learn these!)
  ➢ Typical patient doses in clinical studies (CT TAP, PA chest radiography etc)
  ➢ Dose limits in IRR17 or triggers for incident reporting in IRMER17
  ➢ Spatial resolution of different imaging modalities
  ➢ Operating parameters in clinical studies (eg typical focal spot size or kVp in
  mammography, CT etc)
  ➢ Composition & properties of radiation detectors (eg the input screen in an
  image intensifier – what is it made of? How much radiation does it detect?)

Answer 4

• Note that if the data given to you is intentionally “False” it will
  usually be a factor of x1.5 (or more) from the “True” value

Example:
a) The average annual dose in the UK from natural background radiation is
typically 4mSv (False)

b) The average annual dose in the UK from natural background radiation is
typically 2mSv (True – actual value is 2.3mSv)

Question 5

Answer 5

Question 6

“Comparison” MCQ
* Not very frequent for ionising radiation questions
* Tend to occur on questions relating to
➢ Comparing types of x-ray interaction (in patients or detectors)
with changes in x-ray energy

Answer 6

➢ Comparing patient doses in clinical studies

➢ Comparing spatial resolution from different modalities
* You don’t need to know exact values here, just which is
larger/smaller, faster/slower etc

Question 7

Answer 7

Question 8

“Reflective” MCQ
* Probably the commonest type of question

• Need to be able to reflect on what you know about the topic and decide if the assertion is True or False

Answer 8

• Common topics for reflective MCQs are:

➢ Identifying the definition of physical quantities (eg linear attenuation coefficient, absorbed dose, effective dose etc)
➢ Identifying which parameters affect patient dose

➢ Identifying which parameters affect image quality (ie spatial resolution, contrast and noise)

➢ Recognising the causes of image artefacts

Question 9

Answer 9

Question 10

“Consequential” MCQ

• Fairly common and tend to be stand alone questions
• Need to be able to predict what changes will occur – so will require some interpretation of your knowledge
• Common topics are:
  ➢ Effect of changing tube voltage (kVp)
  ➢ Effect of changing tube current (mA)
  ➢ Effect of changing the amount of added filtration
  ➢ Effect of changing geometric factors (focal spot size, SSD etc) on
  image quality
• Need to understand how these changes affect the x-ray beam spectrum, types of x-ray interaction, patient dose and image quality (spatial resolution, contrast & noise)

Answer 10

Question 11

Answer 11

Question 12

Consequential MCQs - READ THE STEM REALLY CAREFULLY

NEVER ASSUME EXTRA INFORMATION

Answer 12

Consequential MCQs - some conditions must be considered

Question 13

“Consequential” MCQ

• It is important to read the main stem of the question thoroughly
• Unless there are additional conditions mentioned, only one parameter
  is being altered

Answer 13

Example 1:
Increasing the voltage applied to an x-ray tube increases the
a) x-ray output

b) attenuation of x-rays by the patient…… etc

• In this example only the kVp is being altered, nothing else.
• So x-ray beam intensity will increase dramatically (Intensity α kVp2)
• Patient dose will also increase (because the intensity is a lot higher)

Question 14

“Consequential” MCQ
* However, sometimes conditions are stated which must be considered
Example 2:

Increasing the voltage applied to an x-ray tube whilst maintaining a constant image receptor dose will increase:

a) x-ray output
b) attenuation of x-rays by the patient…… etc

Answer 14

• In this example the kVp is being increased but at the same time the mAs
  is being reduced to maintain a constant dose to the image receptor
  (even though the question doesn’t explicitly state this)
• At higher kVp the beam is more penetrating, therefore less radiation is
  needed at the surface of the patient
• Hence, the x-ray output (the beam intensity) will decrease
• Patient dose decreases

Question 15

Effect of kVP in isolation

Answer 15

Question 16

Effect of Current in isolation

Answer 16

Question 17

“Data Accuracy” MCQ
* Tend to occur on questions relating to:
– Patient doses or administered activities in nuclear med/PET studies
– Spatial resolution in SPECT & PET (ie FWHM in mm)
– Lateral and axial spatial resolution in US
– Wavelength, frequency & velocity of US radiation in clinical studies
– Safe operating values for TI and MI in US
– Magnetic field strength of the fringe field in MR
– eGFR values for safe administration of MR contrast agents
* Note that if the data given to you is intentionally False it will
usually be a factor of x1.5 (or more) from the True value

Answer 18

Question 19

“Comparison” MCQ
* Tend to occur on questions relating to:
➢ Comparing patient doses between SPECT & PET
➢ Comparing spatial resolution from SPECT & PET
➢ Comparing resolution at different distances from a collimator OR across the
FoV of a PET scanner
➢ Comparing T1 vs T2 vs T2* for any tissue
➢ Comparing T1 & T2 relaxation times from different tissues
➢ Comparing relaxation times with & without contrast agents
➢ Comparing energy deposition (tissue heating) from B-mode, colour Doppler
and spectral Doppler
➢ Comparing acoustic impedance or speed of propagation in different tissues
➢ Comparing energy deposition (SAR) for different MR pulse sequences
➢ Comparing SE & GRE pulse sequence parameters
* You don’t need to know exact values here, just which is larger/smaller,
faster/slower etc

Question 20

Answer 20

Question 21

“Reflective” MCQ

• Need to be able to reflect on what you know about the topic and decide if the assertion is True or False
• Common areas are:
  – Definition of T1 & T2 relaxation & relaxation times in MR
  – Parameters affecting patient dose in nuclear medicine/PET studies
  – Parameters affecting image quality (spatial resolution, contrast
  and noise) in NM/PET, US & MR
  – Parameters affecting Doppler frequency shift
  – Recognising the causes of image artefacts in NM/PET, US & MR

What affects spatial resolution, contrast or noise IN ANY MODALITIES

Question 22

Answer 22

Question 23

“Consequential” MCQ
* Need to be able predict what changes will occur – so will require some
interpretation of your knowledge
* Common areas to consider are – “What is the effect of…. “
➢ Changing operating frequency in B-mode on depth of scan and spatial
resolution
➢ Changing operating frequency in pulsed Doppler on frequency shift
and aliasing
➢ Changing flip angle, TR, TE or TI on image contrast in MR pulse
sequences
➢ Changing pixel size, matrix size or slice thickness on spatial resolution
and/or SNR in MR
➢ Changing magnetic field strength, Bo, on image quality, image acquisition times and possible artifacts

• In your revision, try to work through scenarios of what will happen when
  a parameter changes

Question 24

Answer 24

Question 25

• It is important to read the main stem of the question thoroughly
• Unless there are additional conditions mentioned, only one parameter is being altered in the question
• Never assume information that isn’t given in the question
• The questions are carefully planned to be as unambiguous as possible

Answer 25

• Only ~30sec thinking time per question
• Don’t “over think” your answers
• If in doubt, go with your gut instinct
• No negative marking, so answer all 200 questions (guess, if needed)
• There’s a lot to revise, so start now (if you haven’t already)
• Ask your local physicists for help