Introduction: The ability to localize and differentiate between hypoxic and well-oxygenated tumors in vivo may aid in the staging of treatment and affect the choice of therapeutic agent. This potentially can be achieved through the use of magnetic resonance spectroscopy (MRS) to measure the relative concentrations of two molecules 1)lactate - a marker for non-oxidative glycolysis, and 2) choline - when enhanced, a marker for active tumor. To assess metastatic neck nodes resulting from primary occurances of squamous cell carcinoma, we have implemented a new J-difference editing scheme using band selective inversion with gradient dephasing (BASING) which was developed for water suppression and lactate rephasing. BASING applied to lactate editing is unique in that the four benefits are provided: 1) singlet suppression with resilience to B1-scaling errors, 2) easy incorporation into localization sequences such as point resolved spectroscopy (PRESS) 3) arbitrary echo times for TE >= 1/J, and 4) RF pulses with steep transition bands that are required to maintain visibility of the choline resonance. Methods: Data were collected from 8 patients and volunteers with the following scan parameters: TR = 2s, TE = 144 ms, number of acquisitions = 256. A 4-element head, neck and cervical phased-array coil (MRI Devices Corp., Waukesha, WI.) operating in receive-only mode was used to maximize coverage and the SNR. To achieve robust separation of lactate from the singlets, a novel phase regularization algorithm, which compensated for phase and frequency variations between successive excitations, was developed. Results: Data from the neck muscle of a normal volunteer showed that a lipid suppression factor of over 1000 was achievable with use of the phase regularization algorithm. The spectra from the neck tumor nodes demonstrated variable amounts of choline and lactate detected. However, the two spectra with the most lactate and choline had median pO2 values of approximately 0.7 mm Hg which is highly suggestive of hypoxia Conclusions: We have demonstrated the use of a new MRS technique capable of detecting both choline and lactate resonances in vivo in head and neck tumors. This has not previously been accomplished and may offer a noninvasive means of differentiating between necrosis, hypoxic and well-oxygenated tumors.
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