Jane Wang MD, Presenter: Nothing to Disclose

Benjamin M. Yeh MD, Abstract Co-Author: Nothing to Disclose

Bonnie N. Joe MD, PhD, Abstract Co-Author: Nothing to Disclose

Fergus V. Coakley MD, Abstract Co-Author: Nothing to Disclose

Reed F. Busse PhD, Abstract Co-Author: Employee, General Electric Company

Greg Zaharchuk MD, PhD, Abstract Co-Author: Nothing to Disclose

To assess the feasibility of MR imaging measurement of urine oxygen tension (pO2) in vivo using T1 relaxivity, because renal medullary hypoxia is frequently implicated in renal dysfunction and urine oxygenation in the renal pelvis reflects the adjacent medullary oxygenation.

The longitudinal relaxation time (T1) of fluids is inversely proportional to oxygen content, allowing pO2 to be measured by MR imaging. MR images of urine phantoms with a known range of pO2 were acquired using a real time saturation recovery T2-prepped SSFSE sequence at 1.5T (TR1=10s, TR2=3s; T2-prep time=900ms; TE=60ms; slice thickness=5mm) to calibrate measured urine T1 values to pO2. Following IRB approval, the urinary bladders of 2 volunteers were imaged using the same MR sequence. The MR measurement of bladder urine pO2 in vivo was compared to the oxygen electrodes pO2 measurement of voided urine samples obtained immediately after MR imaging. MR images of the renal pelvis were also acquired in 7 other volunteers while breathing room air and again after breathing 100% O2 via facemask for 20 minutes. The renal pelvic urine pO2 was compared before and after 100%O2 breathing.

Our phantom study confirmed an inverse linear relationship between the urine T1 and pO2: 1/T1 (1/s)=0.2253+0.000261*pO2 (mmHg). The in vivo bladder urine pO2 measured by MR imaging (35±7mmHg) correlated well with the pO2 of voided urine samples measured by oxygen electrodes (45±3mmHg). Successful in vivo MR measurements of renal pelvic urine pO2 were obtained in 5 of 7 volunteers; pO2 measurements could not be obtained in 2 others due to poor visualization of the renal pelvis. The renal pelvic urine pO2 measured by MR imaging ranged from 30 to 57±10mmHg at room air breathing. Following 100%O2 breathing, the renal pelvic urine pO2 measurements showed a significant rise of 21 to 39 ±12mmHg in 4 of the 5 volunteers (p<0.05), and remained unchanged in the other.

We show for the first time that urine pO2 quantification is feasible by MR imaging.

MR imaging monitoring of renal pelvic urine oxygenation as a surrogate of renal medullary oxygenation may improve early detection of renal ischemia.

Wang, J, Yeh, B, Joe, B, Coakley, F, Busse, R, Zaharchuk, G, MR Imaging Measurement of Urine Oxygen Tension in Vivo Using T1 Relaxivity: A Feasibility Study.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5012200.html