RANZCR – 2014 AIT

April 2014

Section 1 – Radiation Biology and Safety 

Question 1 

1. Define the following dose terms and indicate their units: absorbed dose, equivalent dose and effective dose. (4 marks) 
2. Briefly discuss why the effective dose may be a useful dose metric but also indicate its limitations. (3 marks) 
3. Briefly explain the following term in the context of the biological effects of ionizing radiation on human tissue: The linear-quadratic dose response model (2 marks) 
4. Briefly explain the following term in the context of the biological effects of ionizing radiation on human tissue: Somatic versus hereditary effects (1 mark) 

Question 2 

1. The ICRP has developed a system of dose limits for the protection of individuals and populations. In 2011 the ICRP reduced the equivalent dose limit for occupational exposure that applies to the lens of the eye. What is the new dose limit and why did the ICRP consider it necessary to reduce it? (1.5 marks) 
2. What precautions might you take to minimise your eye exposure during prolonged interventional procedure? (1.5 marks) 
3. A patient undergoes a particularly long and difficult abdominal interventional angiography procedure and in spite of your best efforts to minimise the patient’s skin dose the angiography system post procedure dose readout indicates that the maximum skin dose received by the patient may be as high as 10 to 15 Gy. What possible tissue reactions might you anticipate in this dose range? (5 marks) 
4. What advice might you give the patient’s referring doctor in terms of on-going patient management? (2 marks) 

Question 3 

1. What is the magnitude of the effective dose that an average sized patient might expect from: a non-contrast CT abdo-pelvis examination, a CT brain examination, and a nuclear medicine bone scan? How do these dose values compare with the natural background radiation? (3 marks) 
2. A 60 year old female patient with inflammatory bowel disease is scheduled to have a CT scan of the abdomen – pelvis with and without contrast. She has concerns about her radiation exposure as she has had similar scans twice in the last year and she has heard that CT scans are dangerous. What might you say to her to alleviate her concerns? (7 marks) 

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

Question 1 

1. X-rays are produced at the anode of the X-ray tube by two processes, Bremsstrahlung and characteristic radiation. Write concise notes describing these processes. (7 marks) 
2. Briefly describe the process by which filtration removes lower energy Bremsstrahlung from a diagnostic X-ray beam (3 marks) 

Question 2 

1. You are performing a fluoroscopic examination on the abdominal region of a large patient using the “normal” dose mode of the automatic brightness control (ABC). The fluoroscopic images obtained are found to be unacceptably “grainy” or “noisy”. What simple actions taken by you or the radiographer, involving changes in the x-ray imaging technique factors might remedy this situation? (4 marks) 
2. Explain associated negative consequences from actions detailed in question 1 above, and any reasons that may make those actions fail to provide the expected result. (4 marks) 
3. Briefly describe any change in image appearance and radiation dose implications associated with selection of a higher fluoroscopic pulse rate (e.g. 7.5 to 15 pulses per second) (2 marks) 

Question 3 

1. Describe the key components and principles of operation of an X-ray unit used for mammography with computed radiography. Your answer should specifically address the unique features of the X-ray tube, filtration, compression device and the Bucky with AEC. Discussion of the CR unit is not required. (10 marks) 

Section 3 – CT, MRI, US & Nuclear Medicine 

Question 1 

Multi detector helical CT is associated with the following four parameters: Tube current, kVp, Pitch, Reconstruction algorithms (image processing). Describe how changing each of these factors affects the image quality and the patient dose assuming that all other factors remain unchanged. (10 marks) 

Question 2 

1. Describe the various fields (magnetic & RF) and their timing that must be applied to the patient to produce a spin echo image in magnetic resonance imaging, including those necessary to produce spatial encoding of the final image in three dimensions. (6 marks) 
2. Describe how the spin-echo sequence may be adjusted to enhance differences in the values of T1 in the patient tissues and also how it may be modified to enhance differences in T2. (4 marks) 

Question 3 

1. With reference to ultrasound imaging, briefly explain the principles of: Time-gain compensation (include reasons for this) (3 marks) 
2. With reference to ultrasound imaging, briefly explain the principles of: Dynamic range compression (include reasons for this) (3 marks) 
3. With reference to ultrasound imaging, briefly explain the principles of: Pulsed Doppler measurement of blood flow, for example, in an artery. (Not colour imaging) (4 marks) 

Question 4 

1. Conventional nuclear medicine and PET imaging use different principles. Summarise the differences in relation to the radionuclides used, detection of the radiation, the imaging process, and spatial resolution. (8 marks) 
2. Why is CT often used in conjunction with nuclear medicine imaging? (2 marks) 

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September 2014

Section 1 – Radiation Biology and Safety 

Question 1 

A 60 year old female patient with inflammatory bowel disease is scheduled to have a CT scan of the abdomen – pelvis with and without contrast. She has concerns about her radiation exposure as she has had similar scans twice in the last year and she has heard that CT scans are dangerous .

1. Indicate the magnitude of absorbed doses for organs irradiated in the scanned volume and the effective dose from the exams (4 marks)
2. Discuss the various radiation related risks that may apply (3 marks)
3. What might you say to her to alleviate her concerns? (3 marks)

Question 2 

1. Define the terms absorbed dose, equivalent dose and effective dose and indicate the SI units used to quantify them. (4 marks)
2. Dose limits do not apply to patient expsures but increasingly Siagnostic Refernce Levels (DRLs) do. What are DRLs, how are they derived, and how can they be used to optimize imagine procedures in diagnostic radiology? (6 marks) 

Question 3 

A C-arm X-ray system is used for X-ray guided interventional fluoroscopy on adult patients. The X-ray unit has automatic brightness control (ABC) with a range of dose rate options, including pulsed fluoroscopy and an image intensifier with variable field size. Discuss practical procedural measures that you might implement to ensure that the patient dose is minimised without compromising the diagnostic information obtained. Supplement your answer with reasons for your actions. (10 marks)

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

Question 1 

1. Indicate the expected changes to the shape of the X-ray spectrum when (a) the mAs and (b) the kVp applied to the X- ray tube is increased. (3 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. 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. Describe how the magnification technique differs from the contact technique. (3 marks)
3. Discuss the advantages & disadvantages of the magnification mammogrpahy when compared with contact mammography. (4 marks)

Question 3 

1. Flat panel detectors in Digital Radiography (DR) are generally based on two distinct types, the s-called direct and in-direct detectors. Describe the basic features of the detection process with each type and indicate any possible advantages one type might have over the other. (5 marks)
2. Multi field size image intensification has been the traditional method of undertaking fluoroscopy. Explain the benefits of using a small field size (magnification mode) and indicate, with reasons, what the patient dose implications might be when choosing a small versus a large field size when the image intensifier is operated under automatic brightness control. Specifically, if you were to change from a field size of 30 cm diameter to one of 20 cm what would be the approximate change in dose to the patient if the kV was kept unchanged? (3 marks)
3. Briefly explain nthe difference between continuous fluoroscopy and digital image acquisition (pulsed fluorography) such as might be used in digital subtraction angiography. (2 marks)

Section 3 – CT, MRI, US & Nuclear Medicine 

Question 1 

Describe four (4) operator adjustable factors that have a significant effect on the effective dose to the patient in multi-detector CT imaging. For each factor describe what changes are required to cause a reducation in patient dose when scanning and describe the specific effects that these changes will have on image quality (i.e. noise, spatial resolution, contrast etc). (10 marks)

Question 2 

Briefly explain what is meant by the following terms and how they are relevant in Magnetic Resonance Imaging (10 marks)

1. Fixed magnetic field
2. rf coils
3. Spin echo pulse sequence
4. Magnetic field gradients
5. Chemical shift

Question 3 

1. Lateral resolution in real time ultrasound imaging using a phased array transducer can be improved by focusing the ultrasound beam in the scan plane
   1. Briefly describe the construction of a phased array transducer and how focusing is achieved (3 marks)
   2. Describe how the depth of the focal zone can be adjusted (2 marks)
2. Lateral resolution can be improved over a range of depths by using multiple focal zones. If 2 focal zones are set and the line density and maximum depth of imaging are unchanged, explain what will happen to the fram rate and why. (2 marks)
3. The image (Ultrasound Artifact. jpg) shows tissue brightening posterior to a fluid filled cyst which is artifactual.
   1. (i) name the artifact. (1 mark) (ii) explain the physical processes that cause this artifact. (2 marks)

Question 4 

1. SPECT imaging is most often performed with a dual head gamma camera fitted with parallel hole collimators.
   1. Briefly describe the principles of SPECT imaging acquisition and reconstruction (5 marks)
   2. During SPECT acquisition it is desireable to keep the detectors as close to the patient as possible. Explain why this is done. (1 mark)
2. A parallel hole collimator is essentially a lead sheet with thousands of holes. If the hole diameter is increased, while maintaining the hole length (thickness of collimator), state the effect on the;
   1. Spatial resolution (2 marks)
   2. Sensitivity (2 marks) of the camera, and briefly explain why this occurs.