Rolf Sauter

Proton chemical shift imaging, metabolic maps, and single voxel spectroscopy of glial brain tumors

Seventeen patients with presumed glial brain tumors were examined with proton chemical shift imaging and single voxel spectroscopy that used different echo times. Metabolite resonances were evaluated by metabolic ratios and absolutely by correcting for coil load and comparison to phantom measurements. Metabolic images were created to visualize the metabolic changes. All patients showed spectra that were different from those measured in healthy control subjects. Spectral changes were also present in normal-appearing matter (NAM) that was distant from lesions. The resonance at 3.55 ppm which is usually assigned to bothmyo-inositol and glycine, was the only one to allow a discrimination between healthy volunteers, astrocytoma grade II, and glioblastoma multiforme (GBM) (p<0.02). From the different echo times used we conclude that an increase inhis resonance has to be assigned to glycine rather thanmyo-inositol. This resonance might be used to grade human gliomas more reliably. Total creatine (Cr) decreased more drastically with malignancy than N-acetylated metabolites (NA). This led to a higher NA/Cr ratio in GBM compared to astrocytoma grade II. NA/Cr was thus pseudonormal in GBM due to a change in both nominator and denominator. This study reveals the importance of comparing magnetic resonance spectroscopy data of lesions to spectra measured in identical localizations in healthy control subjects instead of NAM and the importance of quantifying single metabolic peaks instead of creating metabolic ratios in clinical magnetic resonance spectroscopy.

31P-spectroscopy of head and neck tumors—Surface coil technique

Comparative phosphorus-31 magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) of 15 patients with superficial masses such as sarcoma, carcinoma, lymphoma, adenoma, and tuberculosis revealed significant increased concentrations of phosphomonoester, phosphodiester, and inorganic phosphorus in the lesion, whereas the concentration of the phosphocreatine was lower in comparison to muscle tissue. In nearly all masses, pH showed a slight alkaline shift. Existence of necrotic regions detected by MRI was marked by an increase of inorganic phosphorous in the spectra. Tumor growth was characterized by raised concentrations of phosphomonoester. Follow-up studies in a case of lymphoma showed a six-fold decrease of the tumor, while the spectra indicated a gradual transition of tumor values to muscle values. A follow-up study during irradiation of a squamous cell carcinoma revealed a considerable decrease of inorganic phosphate and a subsequent increase of phosphodiester.

Nuclear magnetic resonance apparatus having at least two transmission frequencies

For improving the spectral resolution and/or the signal-to-noise ratio of a nuclear magnetic resonance apparatus for examining first types of atomic nuclei that are nuclear-magnetically coupled to second types of atomic nuclei, signals are additionally emitted on the resonant frequency of the second type of atomic nucleus during the examination of the first type of atomic nucleus. To this end, the nuclear magnetic resonance apparatus includes a reception channel and only one transmission channel for both resonant frequencies. The transmission channel contains a respective synthesizer for each resonant frequency, which define the transmission frequency and contains a modulator unit shared in common by both resonant frequencies.

Chemical shift imaging

The basic task of making separate images of the two largest peaks of the MR proton spectrum (water and fat) has been approached as a problem of pixel by pixel spectroscopy and as a phase correction problem wherein one encodes information about frequency into the phase angle of a complex MR image. Images of induced magnRtic field (susceptibility) can also be made as part of the fat/water image calculations.

Proton-Phosphor-Doppelresonanz-MR-Spektroskopie am Kernspin-Tomographen

Zusammenfassung In 31 P- 1 H-Doppelresonanz-Experimenten an einem 1,5-Tesla Ganzkorper-MR-System wurden betrachtliche 31 P-MR-Signalintensitatszunahmen von in vivo 31 P-Resonanzen beobachtet (bis ca. 70 % fur die Phosphokreatin-Resonanz in Spektren vom Wadenmuskel). Die theoretische und experimentelle Analyse weist auf einen nuklearen Overhauser-Effekt (NOE) hin, der durch die magnetische Dipol-Dipol-Wechselwirkung zwischen Phosphorkernen und benachbarten Protonen in zellularen Metaboliten und in Wassermolekulen bewirkt wird. Breitbandige Protonen-Entkopplung fuhrt zusatzlich zu einer Reduktion der Linienbreite des in vivo gemessenen Phosphodiester-Resonanzhandes in 31 P-Muskelspektren.