ABSTRACT
PURPOSE: The purpose of this study was twofold. First, to compare the contrast between spinal multiple myeloma (MM) focal lesions and surrounding bone marrow obtained on T2-weighted Dixon fat-only MR images to that obtained on T1-weighted spin-echo images. Second, to search for correlation between bone marrow fat fraction assessed by T2-weighted Dixon sequence and International Myeloma Working Group myeloma defining events. MATERIALS AND METHODS: A total of 39 patients with 112 focal MM lesions were included. There were 25 men and 14 women with a mean age of 68.8±9.8 [SD] years (range: 49-88 years). Contrast between focal MM lesions and surrounding bone marrow was calculated on T1-weighted spin-echo and T2-weighted Dixon (including water-only and fat-only) images. Contrast between focal MM lesions and bone marrow was compared using ANOVA and post-hoc Tukey tests. Correlation between bone marrow fat fraction and myeloma defining events was assessed using Spearman's correlation test. RESULTS: MM lesion contrast was greater on T2-weighted Dixon (F (2;93)=35.10) than on T1-weighted images (P<0.0001). Greatest MM lesion contrast was achieved with T2-weighted Dixon fat-only (0.63±0.21 [SD]; range: 0.06-0.91) compared to T2-weighted Dixon water-only (0.45±0.20 [SD]; range: 0.07-0.8) (P=0.0003) and T1-weighted (0.23±0.19 [SD]; range: 0.04-0.87) (P<0.0001) images. There were no significant correlations between myeloma defining events and fat fraction. CONCLUSION: T2-weighted Dixon fat-only images provide greater contrast between MM lesions and adjacent bone marrow than T1-weighted images. The usefulness of a T1-weighted sequence associated to a T2-weighted Dixon sequence has to be determined.
Subject(s)
Image Enhancement/methods , Magnetic Resonance Imaging/methods , Multiple Myeloma/diagnostic imaging , Spinal Neoplasms/diagnostic imaging , Aged , Aged, 80 and over , Bone Marrow/diagnostic imaging , Female , Humans , Image Interpretation, Computer-Assisted , Male , Middle Aged , Retrospective Studies , Signal-To-Noise RatioABSTRACT
We report highly efficient continuous-wave terahertz (THz) photoconductive antenna based photomixer employing nano-gap electrodes in the active region. The tip-to-tip nano-gap electrode structure provides strong THz field enhancement and acts as a nano-antenna to radiate the THz wave generated in the active region of the photomixer. In addition, it provides good impedance matching to the THz planar antenna and exhibits a lower RC time constant, allowing more efficient radiation especially at the higher part of the THz spectrum. As a result, the output intensity of the photomixer with the new nano-gap electrode structure in the active region is two orders of magnitude higher than that of a photomixer with typical interdigitated electrodes. Significant improvement in the THz emission bandwidth was also observed. An efficient continuous wave THz source will greatly benefit compact THz system development for high resolution THz spectroscopy and imaging applications.
ABSTRACT
Deletions of chromosomal arms 1p and 19q are frequent in oligodendroglial tumours and linked to radio- and chemotherapy response as well as longer survival. The molecular mechanisms underlying this clinically important association are as yet unknown. Here, we studied the peroxiredoxin 1 (PRDX1) gene at 1p34.1 for promoter methylation and expression in primary gliomas and investigated its role in radio- and chemosensitivity of glioma cells in vitro. In total, we screened primary glioma tissues from 93 patients for methylation of the 5'-CpG island of PRDX1 by sodium bisulfite sequencing. PRDX1 mRNA and protein expression levels were determined in subsets of the tumours by quantitative PCR and western blot analysis, respectively. PRDX1 hypermethylation and reduced expression were frequently detected in oligodendroglial tumours and secondary glioblastomas, but not in primary glioblastomas. In oligodendroglial tumours, both PRDX1 hypermethylation and reduced mRNA expression were significantly associated with 1p/19q-deletion. Stable knockdown of PRDX1 by lentiviral transduction of short-hairpin (sh)RNA constructs significantly increased apoptosis and reduced cell viability of Hs683 glioma cells exposed to ionizing irradiation or temozolomide in vitro. Taken together, our findings indicate that epigenetic silencing of PRDX1 is frequent in 1p/19q-deleted oligodendroglial tumours and likely contributes to radio- and chemosensitivity of these tumours.