Lecture 9: Renal Imaging

Question 1

What are the indications for a renogram? (2 marks)

Answer 1

Urinary tract obstruction and assessment of potential kidney donors (relative renal function)

Question 2

What two radiopharmacuticals are used and what are the differences? (10 marks)

Answer 2

• Tc-99m DTPA:
  
  • > higher ED, 200 MBq and 1.3 mSv
  • > cleared by GFR
  • > generally used for adults with reasonable renal function
  • > cheap ~ £10
• Tc-99m MAG3:
  
  • > lower ED, 100 MBq and 0.7 mSv
  • > cleared via tubular excretion
  • > used for children and adults with suspected poor renal function
  • > High cost ~ £100

Question 3

Outline the protocol for renal imaging. (6 marks)

Answer 3

• IV injection, image 1min @ 60 FPS and then 30mins @ 2 FPS.
• drink water and void bladder
• dieuretic used to flush activity through system
• image supine and as close to the camera as possible

Question 4

What are the imaging requirements in respect to collimator choice, frame rate and pixel size? (6 marks)

Answer 4

• collimator choice -> want variation in counts with time in ROI, not concerned with image quality therefore sensitivity is key, use LEAP
• frame rate, high during initial uptake 60 FPS for 1 min, then 2 FPS for 30mins
• Pixel size should be ideally 1/3 of FWHM of collimator res (9 mm / 3 = 3 mm). FOV ~ 400 mm so 128 matrix size

Question 5

What processing is carried out on the results? (4 marks)

Answer 5

• motion correct as relatively long imaging
• background correct
• ROI plotting as a function of time to obtain relative function (43-57% is normal)