Task 1:

Q1

a) Explain the two processes involved in the production of X Rays within a hospital setting ensuring you describe both continuous and characteristic spectrums created. (You may use a diagram to aid you in this)

b) Draw a sketched graph of the X Ray spectrum generated by a 100kV tube Voltage using a Tungsten target.

Using your sketch describe what changes you would expect to see with regards to the produced spectrum if the tube Voltage is; i) Decreased ii) Increased

c) What is the purpose of an Aluminium filter and describe how this affects the X Ray spectrum.

d) Define the term ‘attenuation' and state the mathematical equation related to it's calculation. Explain how the attenuation of the beam produces the classic X Ray image of a chest as shown below.

e) Barium and Iodine are routinely used for X Ray procedures.

Which areas of the body is Barium used to image?

Which areas of the body is Iodine used to image?

Explain how the Barium or Iodine contrast medium allows imaging of the areas previously identified.

Task 2:

Q1

a) For each of the three imaging methods below, explain their uses within the modern healthcare setting and give two examples of what they can ‘see' or help diagnose.

i) X Ray
ii) Ultrasound
iii) Nuclear medicine

b) i) Evaluate each of the following imaging methods for their advantages and disadvantages, you should expand the table to ensure you cover all relevant information and all techniques of imaging for each imaging mode.

                                  Advantages        Disadvantages
X Ray Imaging
Ultrasound Imaging

ii) For X Ray imaging an intensifying screen can be used. Explain the benefits of it's use.

c) Directly below the skin is a layer of fat called ‘subcutaneous fat'. An ultrasound probe sends a signal through this layer and some of the signal is reflected back after meeting a fat to muscle boundary (see figure).

Using the values of Z provided and the equation calculate the fraction of the reflected signal at this boundary.
Equation: I_r/I_0 =((Z_2-Z_1)/(Z_2+Z_1 ))
Z(fat) = 1.4 x 106
Z(muscle) = 1.6 x 106

d) The following equation can be applied to waves in order to ascertain the speed at which an object moves towards or away from a fixed position.

f^'= c/((c-2v) ) ×f

Where;

f = the original frequency f' = the new frequency
c = speed of the wave in the medium v = speed of the object

If an ultrasound probe is set to use 6 MHz waves, the speed of the waves in the blood is 1600 ms-1 and the speed the blood is moving towards the transducer is 0.12ms-1.

Calculate to 2 s.f.the change in frequency of the detected wave.

Q2

a) The formula used to calculate the intensity of an X-ray beam is; I=I0 e^(-μx)

The typical value of µ for fleshia 100 m-1.

Use the formula to calculate the thickness of flesh required to reduce the intensity to half. This is termed the ‘half value thickness' of a material.

Without completing any calculations, would the half value thickness of bone be more or less than this?

b) Below is the equation for calculating the effective half life of a radiopharmaceutical that may be administered for gamma imaging. Briefly explain what each of the terms in the equation relate to.

T_e=(Tp×Tb)/(Tp+Tb )

Where;
Te = Effective Half Life Tp= Physical Half life Tb = Biological half life

A commonly used radionuclide in medical physics is Technetium 99m. It has a half-life of 6 hours.

How many half lives are required to pass by in order to reduce the sample by a factor of 16.

Complete and expand the following table, to show this for a radioactive sample of Technetium 99m with initial Activity of 2000.

Time (hr) Activity (Bq)
0                2000

What does the unit Bq stand for?

One of the reasons Technetium 99m is utilised in a hospital setting is that it can be produced safely within a hospital setting using Mo 99 which decays by beta decay and has a T1/2 of 67 hours.

Sketch a graph of Technetium 99m production in a hospital that is regularly eluted every 24 hours.

Explain briefly the key points to it's shape

c) Using a block diagram, explain how a gamma camera works to produce an image ensuring you define any key words.

The first block is completed for you but without keywords defined.