RANZCR – 2018 AIT

March 2018

Section 1 – Radiation Biology and Safety 

Question 1 

Dose indicators are used when comparing the results of a dose audit (typically involving >20 patients) for a particular examination to an appropriate diagnostic reference level (DRL). 

1. Name two commonly used dose indicators for a CT examination and define each quantity. (4 marks) 
2. Name two commonly used dosimetric quantities for interventional angiography and define each quantity. (3 marks) 
3. State what statistic from the dose indicator data collected for a dose audit is used to compare to the DRL and explain why this particular statistic is employed. (2 marks) 
4. A dose audit for an AP abdominal x-ray examination was conducted at a radiology practice and the audit results indicated an entrance surface dose below the published DRL of 4 mGy for this procedure. However, it was found that one patient had a recorded entrance surface dose of 7.3 mGy. Discuss a possible reason for this higher dose given the audit result was judged to be below the DRL. (1 mark) 

Question 2 

1. An average sized pregnant female patient who is 7 weeks pregnant requires a clinically justified AP abdominal X-ray. What advice should be given to the referring doctor who wants to know what he can tell his patient about any possible radiation concerns for the fetus given that:
   1. an entrance skin dose of 4 mGy is posted as the diagnostic reference level for an abdominal X-ray for your hospital; 
   2. automatic exposure control is routinely used. 
   3. Outline your response to this situation beginning with an approximate estimate of the fetal dose. (6 marks) 
2. At the time of the abdominal X-ray examination, a colleague suggests that before exposing the patient, a lead apron be placed on the patient’s abdomen claiming that this will significantly reduce the dose to the fetus while still generating a diagnostically useful image. Discuss the appropriateness of such a dose reduction strategy. (4 marks)

Question 3 

1. CT fluoroscopy is a convenient imaging modality for needle biopsy including drainage procedures. It is accompanied by increased radiation risks to the radiologist or registrar performing the procedure. What are these risks and what precautions might you take to minimise them? (5 marks) 
2. A female nurse who works part-time 2 days per week in the interventional suite has just found out she is pregnant and is concerned about her radiation exposure and what dose limits might apply. How would you advise her and detail what steps, if any, you would take to demonstrate compliance with regulatory or hospital requirements. (3 marks) 
3. She is also concerned about the eye dose she receives and would like an indication of her exposure. How could this be achieved and what is the dose limit for such an exposure. (2 marks) 

Section 2 – Basic Physics & Technology including Mammography, Fluoroscopy & DSA

Question 1 

1. Briefly explain the expected changes to the shape of the X-ray spectrum (see diagram) when: 
   1. the mAs in increased; (1 mark) 
   2. the kVp applied to the X-ray tube is increased. (2 marks) 
2. Explain the intent behind the operation of an Automatic Exposure Control (AEC) system used with a Digital Radiography system. A description of the technology is not required. (3 marks) 
3. Discuss, with reasons, the impact of increasing the kVp on image quality and patient dose when a Digital Radiography unit is used in conjunction with an AEC system. (4 marks) 

Question 2 

1. Explain why ‘noise’ is a stochastic process that is a persistent component of every x-ray beam as well as its potential effect on image quality. (2 marks) 
2.  
   1. With regard to image noise, what is ‘quantum mottle’? (1 mark) 
   2. What determines the amount present in an image? (1 mark) 
3.  
   1. Will quantum mottle increase or decrease if the dose that reaches the imaging plate doubles? (1 mark) 
   2. By how much will the quantum mottle change if the dose is doubled? (2 marks) 
4. A referrer mentions that the x-ray images from your facility are diagnostically adequate but noisier than those from other service providers. In responding to the referrer, list three factors that you believe justify the quality of images from your facility. (3 marks) 

Question 3

1. K-edge filtration is frequently used in mammography. Explain what is meant by this concept and why it is particularly useful in mammography. (3 marks) 
2. When undertaking assessment of women with suspected breast disease, magnification mammography views are undertaken as an adjunct to the usual contact mammography views. Briefly describe three differences between the magnification technique and the contact technique. (3 marks) 
3. Discuss the advantages and disadvantages of magnification mammography when compared with contact mammography. (4 marks) 

Section 3 – CT, MRI, US & Nuclear Medicine

Question 1 

For images taken with a multislice CT scanner, describe the effects of increasing the following parameters (Pitch, kV and mAs per rotation) on each of the following features of the image: 

• Signal to noise in the image 
• Patient effective dose 

You should assume that the parameters modified are the only ones changed. That is, ignore machine adjustments that might be made with a modern scanner. 

You should also give brief reasons to justify your answers since half the marks for the questions will be given for correct reasons. 

1. Pitch (3 marks) 
2. kV (4 marks) 
3. mAs per rotation (3 marks) 

Question 2 

The attached diagram is a simplified version of an MRI pulse sequence. With respect to this pulse sequence answer the following questions: 

1. What type of sequence does this represent? (1 mark) 
2. The slices will be perpendicular to which axis? (give reasons for your answer) (1 mark) 
3. Which is the frequency encoding axis? (give reasons for your answer) (1 mark) 
4. What changes would you make to the RF pulses to convert this to a gradient recalled echo sequence? (1 mark) 
5. In terms of the times t1, t2, t3, and t4 define the echo time TE and the repetition time TR. (2 marks) 
6. What would be required to make T1 relaxation time dominate contrast in the image? (2 marks) 
7. What would be required to make T2 relaxation time dominate contrast in the image? (2 marks)

Question 3 

1. In gamma camera imaging, a collimator is fitted to the face of the camera. 
   1. Briefly describe the physical structure of a gamma camera collimator. (1 mark) 
   2. Explain why it is necessary for image formation. (2 marks) 
2. For gamma camera imaging, an “energy window” is utilised. 
   1. Define “energy window”. (1 mark) 
   2. Using an energy window results in rejection of many unwanted photons. Given that Tc99m emits a single photon energy, what are the main type of unwanted photons that are rejected. (1 mark) 
   3. Describe the processes that cause these photons to be outside the “energy window”. (1 mark) 
3. For PET imaging, briefly describe: 
   1. The processes that occur between radioactive decay and photon detection. (2 marks) 
   2. How the signals from detected photons are used to spatially localise activity distribution. (2 marks) 

Question 4 

1. For the following transducer types, describe how the individual crystal elements are fired in order to sweep the beam through the tissue being imaged: 
   1. phased array (2 marks) 
   2. linear array (2 marks) 
2. One of the criteria for identifying a structure as being filled with fluid (such as a cyst) is the presence of an artefact in the image. 
   1. Describe this artefact. (1 mark) 
   2. Explain what causes it. (3 marks) 
3. Most ultrasound real-time imaging devices display an MI value. This represents the likelihood of a particular phenomenon occurring. 
   1. State what “MI” stands for. (1 mark) 
   2. State the phenomenon it refers to. (1 mark)

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September 2018

Section 1 – Radiation Biology and Safety 

Question 1 

1. Ionising radiation exposure may be expressed as absorbed dose, equivalent dose or effective dose. Define each of these quantities and give the units in which they are measured. (3 marks) 
2. Ionising radiation can cause harmful effects to persons irradiated. Describe 2 possible effects for medical irradiation with low doses (<100 mSv) and 2 possible effects with high doses and dose rates (>2 Sv). (4 marks) 
3. A patient has received a considerable dose of ionising radiation over the course of many years as a result of multiple CT scans. Their GP believes that they should receive another CT scan, but is concerned about the previous dose received. What would your advice be concerning the advisability of further CT scans? How would this advice differ if the patient had no previous ionising radiation exposure? (3 marks) 

Question 2 

1. All people are subject to background radiation, which can be thought to consist of natural background radiation and artificial or man-made radiation components. What are the approximate radiation levels for natural and man-made radiation in Australia or any other country you wish to identify? Name the source of a major component for each type of background radiation. (4 marks) 
2. Radiation has been described as a mild carcinogen. Further, the effect of radiation on different organs of the body does not show a uniform response. Identify the major study which has contributed most to our knowledge of the effects of radiation on cancer. Name four of the most sensitive organs to radiation. (3 marks) 
3. In the context of biological effects of radiation discuss:
   1. Somatic versus hereditary effect (1 mark) 
   2. Latency period (1 mark) 
   3. Linear energy transfer. (1 mark) 

Question 3 

1. Name and define with units two commonly used dose indicators for a CT examination that are also used as the basis for optimization of CT protocols. (4 marks) 
2. Explain the principle of optimisation in radiation safety for medical exposure and define how national DRLs can be used to achieve optimisation for CT examinations. (4 marks) 
3. Kerma area product (KAP also known as DAP) is a commonly used dose indicator for both x-ray examinations and fluoroscopy procedures. Define this quantity and discuss why it can be an appropriate dose indicator for optimisation purposes. (2 marks) 

Section 2 – Basic Physics & Technology including Mammography, Fluoroscopy & DSA

Question 1 

1. Identify and describe the two most common atomic interactions that occur when diagnostic x-rays (assume 50 to 120kV range) pass through human tissue (4 marks) 
2. Identify the key factors that will influence the probability of each of these interaction processes. (2 marks) 
3. Briefly explain the rationale for choosing low kilovoltage (e.g. 50kV) for a hand X-ray. Your answer should consider image quality and patient radiation dose implications. (2 marks) 
4. Identify and briefly describe two (2) applications of the photoelectric k-edge in optimising the x-ray image production process. (2 marks) 

Question 2 

1. Define the terms spatial resolution and image contrast and explain how they apply to clinical radiographic images. (4 marks) 
2. Explain why contrast-to-noise ratio is a more relevant metric than contrast alone in the context of adjusting the appearance of digital images on a PACS monitor. (2 marks) 
3. Identify and briefly describe the impact of 3 factors having a substantial effect on spatial resolution in projection radiographic imaging. (4 marks) 

Question 3 

A patient is undergoing an interventional Posterior Anterior (PA) investigation using a fluoroscopic system with a flat panel detector. The exam is undertaken utilising automatic brightness control, and (initially) a square image receptor field-of-view of 30 cm x 30 cm. 

1. Explain with reasons, any changes to the patient skin entrance dose rate and image quality if the image is magnified by selecting an image receptor square field-of-view of 15 cm x 15 cm. Note that accurate quantification of the changes are not required. (4 marks) 
2. What is the impact on skin dose and image quality if collimators are manually adjusted to reduce the irradiated area while maintaining a detector field-of-view of 30 cm x 30 cm? (2 marks) 
3. Explain with reasons, any changes to the patient skin entrance dose rate and image quality if the gantry orientation is adjusted to an angle of 45 degrees. (4 marks) 

Section 3 – CT, MRI, US & Nuclear Medicine 

Question 1 

1. For a modern CT scanner, describe the impact of the following actions on the signal to noise ratio in the images and the effective dose to the patient. You should also give brief reasons to justify your answers since half the marks for the questions will be given for correct reasons.  (Assume that the parameters modified are the only ones changed and assume any form of automatic current modulation is NOT employed.) 
   1. Increasing the mAs per tube rotation. (3 marks) 
   2. Increasing the slice width. (3 marks) 
   3. Using iterative reconstruction instead of filtered back projection to reconstruct the collected data. (3 marks) 
2. What is the effect of decreased signal to noise ratio on contrast detectability? (1 mark) 

Question 2 

The attached diagram is a simplified version of an MRI spin-echo pulse sequence. Questions (a) to (e) refer to this diagram. 

1. What occurs at t3 as a direct result of the 180° RF pulse? (1 mark) 
2. What is the purpose of the gradient field acting along the y-axis, and how does it achieve this purpose? (3 marks) 
3. Describe how the RF pulse at time 0 could differ for a fast sequence incorporating reduced repetition times (i.e. a reduced TR). (1 mark) 
4. In terms of the echo time TE and the repetition time TR, what would be required to make T1 relaxation time dominate contrast in the resultant image? (2 marks) 
5. In terms of the echo time TE and the repetition time TR, what would be required to make T2 relaxation time dominate contrast in the resultant image? (2 marks) 
6. List two biohazards associated with an MRI machine (just the machine itself; do not include contrast-related effects) (1 mark)

Question 3 

1. Diagnostic ultrasound images are all created using a pulse-echo mode. Describe the key principles of pulse-echo mode, covering the means by which a line in an ultrasound image is formed. Your answer should include how depth and brightness are determined. (3 marks) 
2. To form a real-time ultrasound image a number of assumptions about how sound travels though and interacts with tissues are required. Name FOUR of these assumptions. (2 marks) 
3. What can occur in the image if one or more of the assumptions made about how the sound travels and interacts in tissue are not true. (1 mark) 
4. Ultrasound has the potential to cause damaging biological effects via 2 primary mechanisms.
   1. Name the 2 mechanisms (1 mark) 
   2. For each briefly describe how damage can could potentially occur (2 marks) 
   3. Modern diagnostic ultrasound equipment provides on screen feedback to the operator in the form of a numerical parameter to quantify each mechanism. Name each of these parameters. (1 mark) 

Question 4 

Suppose Nuclear Medicine perfusion lung scans at your practice are routinely acquired using SPECT imaging on a dual detector gamma camera using 99mTc-MAA as the radiopharmaceutical with an activity for an average size patient in keeping with published DRLs for this procedure. 

1. Describe how SPECT images are produced for such a study using this type of camera. The description should include any important technical aspects of the acquisition phase. Note: DO NOT describe the operation or image formation processes of a gamma camera detector, e.g. the function of the collimator or PMT tubes in the camera head. (5 marks) 
2. A colleague suggests doubling the activity administered to patients undergoing this scan. 
   1. If the image acquisition parameters are unchanged, state how the image quality of the study would be affected and give reasons justifying your answer. (2 marks) 
   2. Quantify any changes, from a radiation dose perspective, in the risk to the patient. (1 mark) 
3. The 99mTc radioisotope used in this procedure is widely used in nuclear medicine radiopharmaceuticals. List 4 physical or chemical properties of this radioisotope that make it so useful in nuclear medicine imaging. (2 Marks)