Tutorial / Revision - Bone Imaging and Renal

Question 1

What protocol is used for bone imaging? (6 marks)

Answer 1

• 600 MBq of Tc-99m MDP intravenous
• Image 2-3 hrs later for 30 mins with patient supine
• Use LEHR collimators as resolution more important clinically
• Energy window 140 keV +/- 10%
• Drink plenty of water to flush through activity

Question 2

How is the optimal pixel size determined? (3 marks)

Answer 2

• From the Nyquist criterion pixel size no larger than half the size of the FWHM of the object
• Ideally 5-10 pixels across the object
• Increase the number of pixels increases the resolution but decreases the counts per pixel so increases the noise

Question 3

How many counts should be acquired during bone imaging? (4 marks)

Answer 3

• BNMS guidelines recommend 300-500k counts
• This is ~ 21 mins for a child
• Newcastle acquire 100k, which takes 2mins
• Need to consider who is being image, guidance, cost, staff time etc

Question 4

Given a 1 cm^2 lesion has 10,000 counts acquired, what contrast is required to class this as detectable? (3 marks)

Answer 4

• Use the Rose criterion CNR > 4
• Sig = 10,000, so noise = 100, => noise fraction is 0.01
• Contrast = 4 * 0.01 = 0.04

Question 5

What is the purpose of renal imaging and what indications are there? (4 marks)

Answer 5

• See clearance as a function of time and compare relative function
• Used for UTO and assessment of donor suitability

Question 6

Give an outline of a renal imaging procedure for an adult. (7 marks)

Answer 6

• 80 MBq of Tc-99m DMSA intravenous
• Use LEHR collimator with FOV over kidneys and image as close as possible
• 256 matrix with 300k counts for 30mins

Question 7

For renal kidney imaging, what processing is carried out? (3 marks)

Answer 7

• Background correct the counts using ROI outside of kidneys
• Place ROI around kidneys and plot counts as a function of time
• Assess relative function