An Alternative Scheme for13C Chemical-Shift Imaging via Inverse Detection of Protons through an MILS (or Inverse SLIM) Technique

✍ Scribed by Shu-Ming Lee; Der-Lii Tzou; George J.Y Chiou; Hong N Yeung

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 552 KB
• Volume: 130
• Category: Article
• ISSN: 1090-7807
• DOI: 10.1006/jmre.1997.1264

✦ Synopsis

An alternative scheme in acquiring 13 C spectroscopic images ventional means using coplanar concentric surface coils ( 7). using inverse detection via polarization transfer through protons In other studies, proton-enhanced schemes by polarization was proposed and experimentally verified by a phantom using a transfer were often used to boost signal sensitivity (9-11). heteronuclear multiple-quantum coherence technique. This The main difficulty of 13 C imaging and spectroscopy, particscheme has some features that, in special circumstances, can be ularly under in vivo conditions, is the low sensitivity caused exploited to one's advantages. These features are: (1) signal enby the low gyromagnetic ratio and low natural abundance hancement, a feat realizable under favorable conditions; (2) specof the nuclide. However, these drawbacks are not entirely troscopic encoding via constant time; and (3) improvement of the detrimental. For example, being low in natural abundance time efficiency of the constant-time method via optimization by can sometimes be turned into an advantage since it allows the singular-value decomposition analysis. Features (1) and (2) can, option of monitoring events occurring in specific metabolic in some cases, yield better sensitivity than the conventional 3DFT pathways via the administration of a precursor, e.g., glucose, technique without sacrificing the most important attribute of 13 C, with a 13 C label strategically placed in a particular position.

the enormity of the chemical shifts. Such is the case because spectroscopic images acquired by the technique proposed are based on The increasing availability of high-field imaging spectromethe chemical shifts of carbon, in contrast to the other more prevaters and the use of proton-enhanced schemes also alleviate lent inverse-detection schemes. Feature (2) can also offer higher significantly the problem of poor sensitivity. Nevertheless, spatial resolution by shifting the emphasis of signal encoding from despite some of these positive exploitable attributes and techa spectral-resolution-first viewpoint to one that favors spatial resonical improvements, the problem remains formidable for in lution. Feature (3) was adopted from a method previously known vivo applications because of the constraint in scan time. as MILS (metabolite imaging of lines in a spectrum), or the inverse In this article, an alternative method of acquiring chemiof SLIM, an economical scheme originally proposed by Hu et al. cal-shift images of 13 C based on inversion detection via het-(1988, Magn. Reson. Med. 8, 314) for obtaining a compartmentaleronuclear multiple-quantum coherence (HMQC) (12) is ized NMR spectrum.