SWIFT-CEST: A new MRI method to overcome T2 shortening caused by PARACEST contrast agents

Todd C. Soesbe, Osamu Togao, Masaya Takahashi, A. Dean Sherry

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


The exchange of water molecules between the inner sphere of a paramagnetic chemical exchange saturation transfer (PARACEST) contrast agent and bulk water can shorten the bulk water T2 through the T2-exchange (T2ex) mechanism. The line-broadening T2ex effect is proportional to the agent concentration, the chemical shift of the exchanging water molecule, and is highly dependent on the water molecule exchange rate. A significant T2ex contribution to the bulk water linewidth can make the regions of agent uptake appear dark when imaging with conventional sequences like gradient-echo and fast spin-echo. The minimum echo times for these sequences (1-10 ms) are not fast enough to capture signal from the regions of shortened T2. This makes "Off" (saturation at -ΔIω) minus "On" (saturation at +ΔIω) imaging of PARACEST agents difficult, because the regions of uptake are dark in both images. It is shown here that the loss of bulk water signal due to T 2ex can be reclaimed using the ultrashort echo times (<10 μs) achieved with the sweep imaging with Fourier transform pulse sequence. Modification of the sweep imaging with Fourier transform sequence for PARACEST imaging is first discussed, followed by parameter optimization using in vitro experiments. In vivo PARACEST studies comparing fast spin-echo to sweep imaging with Fourier transform were performed using EuDOTA-(gly) 4- uptake in healthy mouse kidneys. The results show that the negative contrast caused by T 2ex can be overcome using the ultrashort echo time achieved with sweep imaging with Fourier transform, thereby enabling fast and sensitive in vivo PARACEST imaging.

Original languageEnglish
Pages (from-to)816-821
Number of pages6
JournalMagnetic Resonance in Medicine
Issue number3
Publication statusPublished - Sept 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Radiology Nuclear Medicine and imaging


Dive into the research topics of 'SWIFT-CEST: A new MRI method to overcome T2 shortening caused by PARACEST contrast agents'. Together they form a unique fingerprint.

Cite this