Detection of in vivo enzyme activity with CatalyCEST MRI. Issue 3 (2nd May 2013)

• Record Type: Journal Article
• Authors: Yoo, Byunghee; Sheth, Vipul R.; Howison, Christine M.; Douglas, Matthew J. K.; Pineda, Carlos T.; Maine, Erin A.; Baker, Amanda F.; Pagel, Mark D.
• Is Part Of: Magnetic resonance in medicine. Volume 71:Issue 3(2014:Mar.)
• Page Start: 1221
• Page End: 1230
• Publication Date: 2013-05-02
• Subjects: Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.24763
• Languages: English
• ISSNs: 0740-3194

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="mrm24763-sec-0001" sec-type="section"> <title>Purpose</title> <p>CatalyCEST MRI compares the detection of an enzyme‐responsive chemical exchange saturation transfer (CEST) agent with the detection of an unresponsive "control" CEST agent that accounts for other conditions that influence CEST. The purpose of this study was to investigate the feasibility of in vivo catalyCEST MRI.</p> </sec> <sec id="mrm24763-sec-0002" sec-type="section"> <title>Methods</title> <p>CEST agents that were responsive and unresponsive to the activity of urokinase plasminogen activator were shown to have negligible interaction with each other. A CEST‐fast imaging with steady state precession (FISP) MRI protocol was used to acquire MR CEST spectroscopic images with a Capan‐2 pancreatic tumor model after intravenous injection of the CEST agents. A function of (super)‐Lorentzian line shapes was fit to CEST spectra of a region‐of‐interest that represented the tumor.</p> </sec> <sec id="mrm24763-sec-0003" sec-type="section"> <title>Results</title> <p>The CEST effects from each agent showed the same initial uptake into tumor tissues, indicating that both agents had the same pharmacokinetic transport rates. Starting 5 min after injection, CEST from the enzyme‐responsive agent disappeared more quickly than CEST from the unresponsive agent, indicating that the enzyme responsive agent was being catalyzed by urokinase plasminogen activator, while both agents also experienced net pharmacokinetic washout from the tumor.</p> </sec> <sec id="mrm24763-sec-0004" sec-type="section"> <title>Conclusion</title> <p>CatalyCEST MRI demonstrates that dynamic tracking of enzyme‐responsive and unresponsive CEST agents during the same in vivo MRI study is feasible. <bold>Magn Reson Med 71:1221–1230, 2014. © 2013 Wiley Periodicals, Inc.</bold></p> </sec> </abstract>