Francisco Ortiz-Nieto

Assessment of lipids in skeletal muscle by LCModel and AMARES.

To process single voxel spectra of the human skeletal muscle by using an advanced method for accurate, robust, and efficient spectral fitting (AMARES) and by linear combination of model spectra (LCModel). To determine absolute concentrations of extra‐ (EMCL) and intramyocellular lipids (IMCL).

Assessment of lipids in skeletal muscle by high‐resolution spectroscopic imaging using fat as the internal standard: Comparison with water referenced spectroscopy

The main purpose of the study was to compare proton (1H) single‐voxel MR spectroscopy (MRS) with high‐spatial‐resolution spectroscopic imaging (MRSI) to determine the lipid content in human skeletal muscle. Unsuppressed water line was used as a concentration reference in the processing of single‐voxel spectra. The spectrum from yellow bone marrow with a 100% fat content and probe with the vegetable oil served as internal and external reference for high‐spatial‐resolution MRSI, respectively. Very good correlation was found between lipid concentrations measured by water referenced single‐voxel MRS and high‐spatial‐resolution MRSI with yellow bone marrow as the internal standard. Excellent correlation was found between total lipid concentrations estimated by high‐spatial‐resolution MRSI with vegetable oil as the external fat standard and yellow bone marrow as the internal reference. From comparison of single‐voxel MRS and MRSI approaches, it follows that relaxation correction of the reference water and methylene fat line is inevitable in processing the standard single‐voxel spectra. The high‐resolution MRSI approach is recommended to avoid the problem of relaxation corrections and enables using vegetable oil as the external fat standard. Magn Reson Med 59:1259–1265, 2008.

Two-dimensional spectroscopic imaging for pretreatment evaluation of prostate cancer: comparison with the step-section histology after radical prostatectomy

PURPOSE To minimize user and vendor dependence of the spectrum processing of prostate spectra, to measure the ratio of choline (Cho) plus creatine (Cr) to citrate (Cit) in the prostate tissue of normal volunteers and cancer patients, and to compare the results with pathologic findings after radical prostatectomy. MATERIALS AND METHODS Four healthy volunteers and 13 patients with prostate cancer were measured. Measurements were performed using two-dimensional magnetic resonance spectroscopic imaging (MRSI) and endorectal coil. A standard vendors spectrum processing approach has been modified. An original feature of this methodology was the combination of vendor-optimized and user-independent spectrum preprocessing in the scanner and user-independent quantitation in the environment of an MRUI software package. (Cho+Cr)/Cit ratio was used for the classification of prostate tissue. Results were compared with histopathology after radical prostatectomy. RESULTS Eight of 13 cancer patients were classified as suspicious or very suspicious for cancer at spectroscopy, three were ambiguous for cancer and two patients were evaluated as false negative. A considerable overlap of metabolite ratios at various Gleason score was found. CONCLUSION The proposed spectrum processing has the potential to improve the accuracy and user independency of the (Cho+Cr)/Cit quantitation. This study confirmed the previous results that a considerable overlap of (Cho+Cr)/Cit ratios exists at various Gleason score levels.

Human brain MR spectroscopy thermometry using metabolite aqueous-solution calibrations.

To estimate absolute brain temperature using proton MR spectroscopy (1H‐MRS) and mean brain–body temperature difference of healthy human volunteers.

MR spectroscopy of the human prostate using surface coil at 3 T: Metabolite ratios, age‐dependent effects, and diagnostic possibilities

To measure prostate spectra of healthy volunteers using a surface coil, to demonstrate age‐dependent effects, and to investigate diagnostic possibilities for prostate cancer detection.

Quantification of lipids in human lower limbs using yellow bone marrow as the internal reference: gender related effects

The main purpose of this study was to determine and compare extra- and intramyocellular (IMCL) lipids content in the calf and thigh muscles of normal male and female volunteers using high-spatial-resolution magnetic resonance spectroscopic imaging (MRSI). The study groups consisted of 10 females and 10 males. The subjects were healthy and normal-weight. Fat (yellow bone marrow) was used as the internal concentration reference. Total fat and IMCL content were computed for all muscles in the slice and for three muscle compartments in the thigh, whereas three muscles and three muscle compartments were evaluated in the calf. To avoid the confounding effects of physical activity and diet, measurements were performed in the same session. A common feature for both genders was that thigh muscles had approximately 2.5 times greater total fat content as compared to muscles of the calf. The mean IMCL level was, however, more than 3 times higher in the calf muscles compared with the thigh. No significant differences in lipid concentrations of correspondent regions of interest were found between genders. The high-spatial-resolution MRSI technique enables a more detailed study of muscle lipid distribution and can therefore improve understanding of muscle lipid metabolism in healthy volunteers and in studies of patients with metabolic disorders.

Short echo time MR spectroscopy of brain tumors: grading of cerebral gliomas by correlation analysis of normalized spectral amplitudes.

To process single voxel spectra of low‐ and high‐grade gliomas. To propose correlation analysis of the scatter plots of normalized spectral amplitudes as a pattern recognition tool for the classification (grading) of brain tumors. To propose a spectrum processing approach that improves the differentiation of proton spectra with dominating macromolecule and lipid peaks.

High-Resolution Echo-Planar Spectroscopic Imaging of the Human Calf

Background This study exploits the speed benefits of echo-planar spectroscopic imaging (EPSI) to acquire lipid spectra of skeletal muscle. The main purpose was to develop a high-resolution EPSI technique for clinical MR scanner, to visualise the bulk magnetic susceptibility (BMS) shifts of extra-myocellular lipid (EMCL) spectral lines, and to investigate the feasibility of this method for the assessment of intra-myocellular (IMCL) lipids. Methods The study group consisted of six healthy volunteers. A two dimensional EPSI sequence with point-resolved spectroscopy (PRESS) spatial localization was implemented on a 3T clinical MR scanner. Measurements were performed by means of 64×64 spatial matrix and nominal voxel size 3×3×15 mm3. The total net measurement time was 3 min 12 sec for non-water-suppressed (1 acquisition) and 12 min 48 sec for water-suppressed scans (4 acquisitions). Results Spectra of the human calf had a very good signal-to-noise ratio and linewidths sufficient to differentiate IMCL resonances from EMCL. The use of a large spatial matrix reduces inter-voxel signal contamination of the strong EMCL signals. Small voxels enabled visualisation of the methylene EMCL spectral line splitting and their BMS shifts up to 0.5 ppm relative to the correspondent IMCL line. The mean soleus muscle IMCL content of our six volunteers was 0.30±0.10 vol% (range 0.18–0.46) or 3.6±1.2 mmol/kg wet weight (range: 2.1–5.4). Conclusion This study demonstrates that high-spatial resolution PRESS EPSI of the muscle lipids is feasible on standard clinical scanners.

Phase-difference and spectroscopic imaging for monitoring of human brain temperature during cooling

Decrease of the human brain temperature was induced by intranasal cooling. The main purpose of this study was to compare the two magnetic resonance methods for monitoring brain temperature changes during cooling: phase-difference and magnetic resonance spectroscopic imaging (MRSI) with high spatial resolution. Ten healthy volunteers were measured. Selective brain cooling was performed through nasal cavities using saline-cooled balloon catheters. MRSI was based on a radiofrequency spoiled gradient echo sequence. The spectral information was encoded by incrementing the echo time of the subsequent eight image records. Reconstructed voxel size was 1×1×5 mm(3). Relative brain temperature was computed from the positions of water spectral lines. Phase maps were obtained from the first image record of the MRSI sequence. Mild hypothermia was achieved in 15-20 min. Mean brain temperature reduction varied in the interval <-3.0; -0.6>°C and <-2.7; -0.7>°C as measured by the MRSI and phase-difference methods, respectively. Very good correlation was found in all locations between the temperatures measured by both techniques except in the frontal lobe. Measurements in the transversal slices were more robust to the movement artifacts than those in the sagittal planes. Good agreement was found between the MRSI and phase-difference techniques.

Quantification of metabolite concentrations in benign and malignant prostate tissues using 3D proton MR spectroscopic imaging

To estimate concentrations of choline (Cho), spermine (Spm), and citrate (Cit) in prostate tissue using 3D proton magnetic resonance spectroscopic imaging (MRSI) with water as an internal concentration reference as well as to assess the relationships between the measured metabolites and also between the metabolites and apparent diffusion coefficient (ADC).