Accurate grading of brain gliomas by soft independent modeling of class analogy based on non‐negative matrix factorization of proton magnetic resonance spectra

Hydrogen magnetic resonance spectroscopy (¹H‐MRS) is a non‐invasive technique which provides a ‘frequency‐signal intensity’ spectrum of biochemical compounds of tissues in the body. Although this method is currently used in human brain studies, accurate classification of in‐vivo ¹H‐MRS is a challenging task in the diagnosis of brain tumors. Problems such as overlapping metabolite peaks, incomplete information on background component and low signal‐to‐noise ratio disturb classification results of this spectroscopic method. This study presents an alternative approach to the soft independent modeling of class analogy (SIMCA) technique, using non‐negative matrix factorization (NMF) for dimensionality reduction. In the adopted strategy, the performance of SIMCA was improved by application of a robust algorithm for classification in the presence of noisy measurements. Total of 219 spectra from two databases were taken by water‐suppressed short echo‐time ¹H‐MRS, acquired from different subjects with different stages of glial brain tumors (Grade II (26 cases), grade III (24 cases), grade IV (41 cases), as well as 25 healthy cases). The SIMCA was performed using two approaches: (i) principal component analysis (PCA) and (ii) non‐negative matrix factorization (NMF), as a modified approach. Square prediction error was considered to assess the class membership of the external validation set. Finally, several figures of merit such as the correct classification rate (CCR), sensitivity and specificity were calculated. Results of SIMCA based on NMF showed significant improvement in percentage of correctly classified samples, 91.4% versus 83.5% for PCA‐based model in an independent test set. Copyright © 2015 John Wiley & Sons, Ltd.     

经前颅窝底硬膜外入路显微外科手术切除颅底邻近部肿瘤

目的:研究位于颅、面、眶等结构之间侵犯前颅窝底的肿瘤手术入路和手术方法方法:与相关科室合作采用前颅窝底硬膜外入路显微外科手术的方法,成功地为9例病人作肿瘤切除术.其中斜坡脊索瘤2例,筛窦恶性肿瘤4例,筛窦良性肿瘤1例,眶内球后胶质瘤1例,眶尖脑膜瘤1例.结果:肿瘤全切除4例,肿瘤大部切除5例,切口均一期愈合,近期疗效良好.结论:对邻近前颅窝或侵犯前颅窝底的各类肿瘤,经前颅窝底硬膜外入路是一种较为理想的外科手术入路.     

Increase of lifespan for glioma‐bearing rats by using minibeam radiation therapy

This feasibility work assesses the therapeutic effectiveness of minibeam radiation therapy, a new synchrotron radiotherapy technique. In this new approach the irradiation is performed on 9L gliosarcoma‐bearing rats with arrays of parallel beams of width 500–700 µm. Two irradiation configurations were compared: a lateral unidirectional irradiation and two orthogonal arrays interlacing at the target. A dose escalation study was performed. A factor of three gain in the mean survival time obtained for some animals paves the way for further exploration of the different possibilities of this technique and its further optimization.     

Activation Energies for the Longitudinal Relaxation Rates of the Water in Normal and Neoplastic Lung

Variable temperature water T₁ relaxation times have been measured on some normal and neoplastic human lung tissues. The corresponding activation energies have been derived and a short discussion of the experimental results is given.     

Magnetic resonance imaging follow-up of liver growth of neuroendocrine tumors in an experimental mouse model

Liver metastases in patients with gastroenteropancreatic (GEP) endocrine tumors represent the main factor of adverse prognosis in this tumor type and thus have a strong effect on the therapeutic strategies. Currently, magnetic resonance imaging (MRI) is considered the modality of choice for the noninvasive, in vivo detection of liver metastases. Dedicated MRI protocols suitable for following liver lesion evolution on an experimental model of endocrine tumors could be valuable. An experimental animal model mimicking the clinical situation of intrahepatic dissemination has been designed. The goal of this study was to characterize liver lesions in this athymic nude mouse model and assess the detection sensitivity of MRI using a physiological gating strategy optimized for high magnetic fields.     

A novel content-based active contour model for brain tumor segmentation

Brain tumor segmentation is a crucial step in surgical and treatment planning. Intensity-based active contour models such as gradient vector flow (GVF), magneto static active contour (MAC) and fluid vector flow (FVF) have been proposed to segment homogeneous objects/tumors in medical images. In this study, extensive experiments are done to analyze the performance of intensity-based techniques for homogeneous tumors on brain magnetic resonance (MR) images. The analysis shows that the state-of-art methods fail to segment homogeneous tumors against similar background or when these tumors show partial diversity toward the background. They also have preconvergence problem in case of false edges/saddle points. However, the presence of weak edges and diffused edges (due to edema around the tumor) leads to oversegmentation by intensity-based techniques. Therefore, the proposed method content-based active contour (CBAC) uses both intensity and texture information present within the active contour to overcome above-stated problems capturing large range in an image. It also proposes a novel use of Gray-Level Co-occurrence Matrix to define texture space for tumor segmentation. The effectiveness of this method is tested on two different real data sets (55 patients - more than 600 images) containing five different types of homogeneous, heterogeneous, diffused tumors and synthetic images (non-MR benchmark images). Remarkable results are obtained in segmenting homogeneous tumors of uniform intensity, complex content heterogeneous, diffused tumors on MR images (T1-weighted, postcontrast T1-weighted and T2-weighted) and synthetic images (non-MR benchmark images of varying intensity, texture, noise content and false edges). Further, tumor volume is efficiently extracted from 2-dimensional slices and is named as 2.5-dimensional segmentation.     

Chalcone JAI‐51 improves efficacy of synchrotron microbeam radiation therapy of brain tumors

Microbeam radiation therapy (MRT), a preclinical form of radiosurgery, uses spatially fractionated micrometre‐wide synchrotron‐generated X‐ray beams. As MRT alone is predominantly palliative for animal tumors, the effects of the combination of MRT and a newly synthesized chemotherapeutic agent JAI‐51 on 9L gliosarcomas have been evaluated. Fourteen days (D14) after implantation (D0), intracerebral 9LGS‐bearing rats received either MRT, JAI‐51 or both treatments. JAI‐51, alone or immediately after MRT, was administered three times per week. Animals were kept up to ～20 weeks after irradiation or sacrificed at D16 or D28 after treatment for cell cycle analysis. MRT plus JAI‐51 increased significantly the lifespan compared with MRT alone (p = 0.0367). JAI‐51 treatment alone had no effect on rat survival. MRT alone or associated with JAI‐51 induced a cell cycle blockade in G2/M (p < 0.01) while the combined treatment also reduced the proportion of G0/G1 cells. At D28 after irradiation, MRT and MRT/JAI‐51 had a smaller cell blockade effect in the G2/M phase owing to a significant increase in tumor cell death rate (<2c) and a proportional increase of endoreplicative cells (>8c). The combination of MRT and JAI‐51 increases the survival of 9LGS‐bearing rats by inducing endoreduplication of DNA and tumor cell death; further, it slowed the onset of tumor growth resumption two weeks after treatment.     

First trial of spatial and temporal fractionations of the delivered dose using synchrotron microbeam radiation therapy

The technical feasibility of temporal and spatial fractionations of the radiation dose has been evaluated using synchrotron microbeam radiation therapy for brain tumors in rats. A significant increase in lifespan (216%, p < 0.0001) resulted when three fractions of microbeam irradiation were applied to the tumor through three different ports, orthogonal to each other, at 24 h intervals. However, there were no long‐term survivors, and immunohistological studies revealed that 9 L tumors were not entirely ablated.