The Essential Guide to the New FRCR

Part 1

Tony Jeswani, John Morlese

• Publisher: CRC Press
• Year: 2018
• eBook ISBN:
  9781315343280
• Topic: Medicine
• Subtopic: Medical Theory, Practice & Reference

The focus of the new Fellowship of the Royal College of Radiologists (FRCR) Part 1 exam has shifted to examining the fundamental physics, and radiation protection required to work safely within a radiology department. This book presents the new syllabus in a multiple-choice format that parallels the new exam. In addition, short answer questions reinforce fundamental teaching points. This essential guide will not only enable candidates to sit the exam with confidence, but will help them achieve a better and long lasting understanding of the subject for their future careers.

Section 1
Basic physics

Radiation

Q1 The following travel at the speed of light in a vacuum. True or false?

• (a) X-rays.
• (b) Gamma rays.
• (c) Sound waves.
• (d) Radio waves.
• (e) Infra-red light.

A1

• (a) True – they travel at approximately 3 × 10⁸ m/s. They do not travel much slower in air.
• (b) True.
• (c) False.
• (d) True.
• (e) True.

Q2 With respect to x-rays describe what is meant by:

• (a) photon fluence.
• (b) energy fluence.
• (c) intensity.

A2

• (a) Photon fluence is the number of x-ray photons passing through a unit area in a particular time (T).
• (b) Each x-ray photon has an individual energy. The sum of all the energies of the photons passing through a unit area in time (T) gives the total energy passing through the unit area in a particular time (T). This is called the energy fluence.
• (c) The total energy passing through a unit area in unit time is the intensity, which is also known as the energy fluence rate.

Q3 What is the relation between x-ray intensity and distance from a point source, and why is this important?

A3 X-rays travel in straight lines. As the distance from the source increases, the intensity of radiation decreases in proportion to the square of the distance:

$\frac{\text{New intensity}}{\text{Old intensity}}=\frac{{\left(\text{Old distance}\right)}^{\text{2}}}{{\text{(New distance)}}^{\text{2}}}$

This is important as moving further away from a source of x-rays reduces the dose received by the radiologist.

Q4 Are the following statements regarding the x-ray tube true or false?

• (a) X-rays are produced when accelerated electrons hit a metal target.
• (b) The energy of the accelerated electrons is converted to heat and x-rays in the proportion of 9:1.
• (c) The positive cathode has a fine tungsten filament which emits electrons by thermionic emission when heated to incandescence.
• (d) The anode usually has a rough and curved tungsten target.
• (e) As the tube contains air, the electrons are only accelerated to half the speed of light.

A4

• (a) True.
• (b) False – 99% is converted to heat and 1% to x-rays.
• (c) False – the cathode is negative. The negative cathode has a fine tungsten filament which emits electrons by thermionic emission when heated to incandescence.
• (d) False – it usually has a smooth and flat tungsten target.
• (e) False – within the tube is a vacuum. This allows the electrons to be accelerated and thus strike the target at approximately half the speed of light.

Q5 How is the x-ray tube current affected by the filament temperature?

A5 As the filament temperature increases, there is a large increase in tube current.

Q6 How do electrons lose their energy in an x-ray tube?

A6 Each electron has kinetic energy (keV) equivalent to the kilovoltage applied between the anode and the cathode. The electrons penetrate a few millimetres into the target and then lose their energy by:

• interaction with the outer-shell electrons. This gives off heat by a large number of very small energy losses.
• interaction with either the inner-shell electron or the field of the nucleus. This results in large energy losses with the production of characteristic x-rays and bremsstrahlung, respectively.

Q7 Explain how characteristic x-rays are produced.

A7 When an electron collides with an inner-shell electron of the target atom, the inner-shell electron can be completely ejected provided the incident electron has more kinetic energy than t...

Table of contents

• Cover
• Title Page
• Copyright Page
• Table of Contents
• Foreword
• Preface
• About the authors
• Section 1: Basic physics
• Section 2: X-rays
• Section 3: Fluoroscopy
• Section 4: Nuclear medicine
• Section 5: Radiation protection
• Section 6: Specialised plain radiography
• Bibliography
• Index