In applications of NMR in inhomogeneous fields, sequences based on the Carr-Purcell-Meiboom-Gill (CPMG) sequence play a central role. The standard CPMG sequence consists of an initial 90° excitation pulse, followed by a long string of 180° refocusing pulses. This creates a series of echoes that decay with characteristic relaxation time T2eff. Here we present a modified sequence, the Split-180° sequence that specifically takes advantage of grossly inhomogeneous fields. In its simplest implementation, the 180° refocusing
pulse of the CPMG sequence is split into two separate pulses. This sequence, which can be viewed as a modification of the CPMG sequence, simultaneously generates two types of signal that can be separately detected. One is a CPMG-like signal that decays with the expected relaxation time T2eff. In addition, a second type of signal builds up and approaches a steady-state. The amplitude of this dynamic equilibrium depends on the ratio of the longitudinal to the transverse relaxation times, T1/T2. We present experimental results and summarize the new theory that describes both signals in a unified manner.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:14110 |
| Date | January 2009 |
| Creators | Freed, Denise E., Scheven, Ulrich M., Hürlimann, Martin D. |
| Contributors | Schlumberger-Doll Research, FCT Universidade Nova de Lisboa, Universität Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:article, info:eu-repo/semantics/article, doc-type:Text |
| Source | Diffusion fundamentals 10 (2009) 19, S. 1-3 |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | urn:nbn:de:bsz:15-qucosa-179075, qucosa:13505 |
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