Usefulness of fat-containing agents: an initial study on estimating fat content for magnetic resonance imaging.

This initial study aimed at testing whether fat-containing agents can be used for the fat mass estimation methods using magnetic resonance imaging (MRI). As an example for clinical application, fat-containing agents (based on soybean oil, 10% and 20%), 100% soybean oil, and saline as reference substances were placed outside the proximal femurs obtained from 14 participants and analyzed by 0.3 T MRI. Fat content was the estimated fat fraction (FF) based on signal intensity (SIeFF, %). The SIeFF values of the femoral bone marrow, including the femoral head, neck, shaft, and trochanter area, were measured. MRI data were compared in terms of bone mineral content (BMC) and bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) in the proximal femur. Twelve pig femurs were also used to confirm the correlation between FF by the DIXON method and SIeFF. According to Pearson's correlation coefficient, the SIeFF and total BMC and BMD data revealed strong and moderate negative correlations in the femoral head (r < - 0.74) and other sites (r = - 0.66 to - 0.45). FF and SIeFF showed a strong correlation (r = 0.96). This study was an initial investigation of a method for estimating fat mass with fat-containing agents and showed the potential for use in MRI. SIeFF and FF showed a strong correlation, and SIeFF and BMD and BMC showed correlation; however, further studies are needed to use SIeFF as a substitute for DXA.

Identification of syllables best recognized in acoustic-stimulated functional magnetic resonance imaging.

In acoustic-stimulated functional magnetic resonance imaging (fMRI), tasks are performed by subjects either during imaging in the presence of scanning noise or during non-imaging periods without scanning noise. Suitable syllables for voice tasks performed with MRI-compatible headphones are limited during the imaging period with scanning noise. However, suitable syllables for voice tasks during the non-imaging period, without scanning noise, are not yet known. This study aimed to identify suitable syllables for voice tasks during both imaging and non-imaging periods. The subjects were 12 healthy volunteers who were native Japanese speakers. On an answer sheet attached to a wooden board, they were asked to write down the syllables they perceived through MRI-compatible headphones during imaging and non-imaging periods. The rate of accuracy for the perception of syllables was calculated; optimally perceived syllables were defined by a rate of accuracy exceeding the 95% upper confidence limit (UCL). The accuracy of syllable perception was significantly higher (P < 0.01) during the non-imaging period (77.2 ± 5.6%) than during the imaging period (66.3 ± 5.0%). The 95% UCLs obtained from the rates of accuracy were 83.5% during imaging and 88.9% during the non-imaging period. The number of syllables for which the accuracy rate exceeded the 95% UCL was 28 during imaging and 33 during the non-imaging period. These syllables could be used for voice tasks in acoustic-stimulated fMRI during imaging or non-imaging periods.

[Quantification and improvement of speech transmission performance using headphones in acoustic stimulated functional magnetic resonance imaging].

Functional magnetic resonance imaging (fMRI) has made a major contribution to the understanding of higher brain function, but fMRI with auditory stimulation, used in the planning of brain tumor surgery, is often inaccurate because there is a risk that the sounds used in the trial may not be correctly transmitted to the subjects due to acoustic noise. This prompted us to devise a method of digitizing sound transmission ability from the accuracy rate of 67 syllables, classified into three types. We evaluated this with and without acoustic noise during imaging. We also improved the structure of the headphones and compared their sound transmission ability with that of conventional headphones attached to an MRI device (a GE Signa HDxt 3.0 T). We calculated and compared the sound transmission ability of the conventional headphones with that of the improved model. The 95 percent upper confidence limit (UCL) was used as the threshold for accuracy rate of hearing for both headphone models. There was a statistically significant difference between the conventional model and the improved model during imaging (p < 0.01). The rate of accuracy of the improved model was 16 percent higher. 29 and 22 syllables were accurate at a 95% UCL in the improved model and the conventional model, respectively. This study revealed the evaluation system used in this study to be useful for correctly identifying syllables during fMRI.