The crossover surface coil: an efficient in vivo nmr detector

A modified crossover surface coil with minimal B1 field penetration was used for collection of skin phosphorus NMR spectra. Projection imaging experiments show that the coil-sensitive volume is uniform at the phosphorus frequency, but strikingly nonuniform at the proton frequency. Experiments with an in vitro phosphorus phantom, designed to simulate skin and underlying tissue, demonstrated that 45.1% (+/- 1.2%) of total signal was derived from Sprague-Dawley rat skin and 19.3% (+/- 1.4%) of total signal was derived from Fischer-344 rat skin. 31P MR spectra of rat skin in vivo permitted resolution of four phosphorus compounds: nucleoside triphosphates, phosphocreatine (PCr), inorganic phosphate (Pi), and phosphomonoester. Spectra collected after skin flap surgery in Fischer-344 rats showed a 50.1% (+/- 7.6%) reduction in the ratio of PCr/Pi within 30 min of surgery, compared to presurgical PCr/Pi levels (P less than 0.01). Skin phosphorus spectra are potentially useful for assessment of skin flap and skin graft viability.

Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

“…The inner braid of the triaxial cable formed the connection between the coil and the preamplifier (2).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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In vivo phosphorus NMR spectroscopy of skin using a crossover surface coil

Chen

Izenberg

et al. 1992

“…Improved coil sensitivity is achieved by the slotted design via an increased tissue surface area presented to the probe for excitation and an increased percentage of ROI coverage with the highly sensitive copper conductor. The slotted concept is feasible because larger dielectric losses normally associated with foil probes and increased copper surface areas ( 19,20) are minimized via the crossover design ( 17).…”

mentioning

confidence: 99%

The slotted crossover surface coil: A detector for in vivo NMR of skin

Nagel

Alderman

Schoenborn

et al. 1990

Self Cite

An elongated, narrow, slotted crossover surface coil provides surface localization capable of resolving in vivo 31P NMR spectra from skin tissues. The shallow B1 field penetration achieves localization objectives while the probe length maintains signal-to-noise requirements. Dielectric and inductive losses are minimized via the crossover design (see T. L. Nagel et al., Magn. Reson. Med. 13, xxx (1990). In vivo spectra with millimeter depth resolution were acquired in 5 min at 2 T without pulse localization sequences. Preliminary 31P NMR spectra of normal and thermally injured rat skin were completed using a 25 X 3-mm slotted probe with a 3 X 2-cm surface region of excitation. Normal rat skin tissue PCr/Pi ratios ranged from 3.8 to 4.7 for 5-, 10-, and 30-mus pulse widths, while partial- and full-thickness scald injured tissues ranged from 0 to 2.8. Evaluation of a single minor partial thickness injury 1 to 5 h postburn shows evidence of a localized hypermetabolic response associated with hyperemia. Determination of burn depth and tissue viability appears feasible using: (1) PCr/Pi ratios and (2) observation of localized hypermetabolism.

In vivo ³¹P NMR studies of orientation effects upon rat brain metabolism during mild hypoxia

Chen

Stolk

Olsen

et al. 1994

Self Cite

Energy metabolites in rat brain under the same level of hypoxia were monitored by 31P NMR in both horizontal and vertical magnets. The changes in PCr, Pi, and pHi in the vertical setting toward the end of hypoxia were significantly larger and the recovery in the horizontally held animals was more complete. The results demonstrated quantitatively that the stress of the alignment is superimposed on the stress of hypoxia in the vertical magnet.