Diffusion MR Imaging with T2-based Water Suppression (T2wsup-dMRI).

PURPOSE: This study proposes and assesses a new diffusion MRI (dMRI) technique to solve problems related to the quantification of parameter maps (apparent diffusion coefficient [ADC] or mean diffusivity [MD], fractional anisotropy [FA]) and misdrawing of fiber tractography (FT) due to cerebrospinal fluid (CSF)-partial volume effects (PVEs) for brain tissues by combining with the T2-based water suppression (T2wsup) technique. METHODS: T2wsup-diffusion-weighted imaging (DWI) images were obtained by subtracting those images from the acquired multi-b value (b) DWI images after correcting the signal intensities of multiecho time (TE) images using long TE water signal-dominant images. Quantitative parameter maps and FT were obtained from minimum data points and were compared with those using the standard (without wsup) DWI method, and partly compared with those obtained using other alternative DWI methods of applying fluid attenuation inversion recovery (FLAIR), non-b-zero (NBZ) by theoretical or noise-added simulation and MR images. RESULTS: In the T2wsup-dMRI method, the hyperintense artifacts due to CSF-PVEs in MRI data were dramatically suppressed even at lower b (≲ 500 s/mm2) while keeping the tissue SNR. The quantitative parameter map values became precisely close to the pure tissue values precisely even in water (CSF) PVE voxels in healthy brain tissues (T2 ≲ 100 ms). Furthermore, the fiber tracts were correctly connected, particularly at the fornix in closest contact to the CSF. CONCLUSION: Solving the problem of CSF-PVE in the current dMRI technique using our proposed T2wsup-dMRI technique is easy, with higher SNR than those obtained with FLAIR or NBZ methods when applying to healthy brain tissues. The proposed T2wsup-dMRI could be useful in clinical settings, although further optimization of the pulse sequence and processing techniques and clinical assessments are required, particularly for long T2 lesions.

Synthetic MRI with T2-based Water Suppression to Reduce Hyperintense Artifacts due to CSF-Partial Volume Effects in the Brain.

PURPOSE: Our purpose was to assess our proposed new synthetic MRI (synMRI) technique, combined with T2-based water suppression (T2wsup), to reduce cerebral spinal fluid (CSF)-partial volume effects (PVEs). These PVEs are problematic in the T2-weighted fluid-attenuation inversion recovery (FLAIR) images obtained by conventional synMRI techniques. METHODS: Our T2wsup was achieved by subtracting additionally acquired long TE spin echo (SE) images of water signals dominant from the originally acquired images after T2 decay correction and a masking on the long TE image using the water volume (Vw) map to preserve tissue SNR, followed by quantitative mapping and then calculation of the synthetic images. A simulation study based on a two-compartment model including tissue and water in a voxel and a volunteer MR study were performed to assess our proposed method. Parameters of long TE and a threshold value in the masking were assessed and optimized experimentally. Quantitative parameter maps of standard and with T2wsup were generated, then wsup-synthetic FLAIR and SE images were calculated using those suitable combinations and compared. RESULTS: Our simulation clarified that the CSF-PVE artifacts in the standard synthetic FLAIR increase T2 as the water volume increases in a voxel, and the volunteer MR brain study demonstrated that the hyperintense artifacts on synthetic images were reduced to <10% of Vw in those with the standard synMRI while keeping the tissue SNR by selecting optimal masking parameters on additional long TE images of TE = 300 ms. In addition, the wsup-synthetic SE provided better gray-white matter contrasts compared with the wsup-synthetic FLAIR while keeping CSF suppression. CONCLUSION: Our proposed T2wsup-synMRI technique makes it easy to reduce the CSF-PVE artifacts problematic in the synthetic FLAIR images using the current synMRI technique by adding long TE images and simple processing. Although further optimizations in data acquisition and processing techniques are required before actual clinical use, we expect our technique to become clinically useful.

5-year survival rates for primary cancer sites at cancer-treatment-oriented hospitals in Japan.

In Japan, The Japanese Association of Clinical Cancer Centers (JACCCs) was established in 1965 by systematizing cancer-treatment-oriented hospitals. The core center of JACCCs is the National Cancer Center in Tokyo. In 1984, JACCCs created The "Improvement for Clinical Cancer Centers in Japan" Study Group (The Study Group) which has subsequently routinely evaluated the effectiveness of the therapy that is provided. In general, the 5-year (relative) survival rate is employed as an indicator of the treatment efficacy. The present survey used the PC software program KAP developed by Chiba Cancer Center in Japan, to calculate 5-year observed survival rates and the 5-year relative survival rates using Ederer II methods. The overall 5-year relative survival rates in patients with stomach (15,353 patients), colon (5,054), rectum (3,695), lung (10,153), breast (11,302) and cervix of the uterus (6,336) were 68.7%, 72.2%, 69.4%, 28.1%, 86.1% and 81.1%, respectively. The survival rates discussed so far are principally observed survival rates. The 5-year relative survival rate for those institutions that specialize in cancer treatment should become an index for Japanese cancer treatment.