Multi-angle ratiometric approach to measure chemical exchange in amide proton transfer imaging

Amide proton transfer imaging, a specific form of chemical exchange saturation transfer imaging, has previously been applied to studies of acute ischemic acidosis, stroke, and cancer. However, interpreting the resulting contrast is complicated by its dependence on the exchange rate between amides and water, the amide concentration, amide and water relaxation, and macromolecular magnetization transfer. Hence, conventional chemical exchange saturation transfer contrast is not specific to changes such as reductions in pH due to tissue acidosis. In this article, a multi-angle ratiometric approach based on several pulsed-chemical exchange saturation transfer scans at different irradiation flip angles is proposed to specifically reflect exchange rates only. This separation of exchange effects in pulsed-chemical exchange saturation transfer experiments is based on isolating rotation vs. saturation contributions, and such methods form a new subclass of chemical exchange rotation transfer (CERT) experiments. Simulations and measurements of creatine/agar phantoms indicate that a newly proposed imaging metric isolates the effects of exchange rate changes, independent of other sample parameters.     

Exchange-mediated contrast agents for spin-lock imaging

Measurements of relaxation rates in the rotating frame with spin-locking techniques are sensitive to substances with exchanging protons with appropriate chemical shifts. The authors develop a novel approach to exchange-rate selective imaging based on measured T(1ρ) dispersion with applied locking field strength, and demonstrate the method on samples containing the X-ray contrast agent Iohexol with and without cross-linked bovine serum albumin. T(1ρ) dispersion of water in the phantoms was measured with a Varian 9.4-T magnet by an on-resonance spin-locking pulse with fast spin-echo readout, and the results used to estimate exchange rates. The Iohexol phantom alone gave a fitted exchange rate of ~1 kHz, bovine serum albumin alone was ~11 kHz, and in combination gave rates in between. By using these estimated rates, we demonstrate how a novel spin-locking imaging method may be used to enhance contrast due to the presence of a contrast agent whose protons have specific exchange rates.     

Diffusion tensor imaging of normal white matter maturation from late childhood to young adulthood: voxel-wise evaluation of mean diffusivity, fractional anisotropy, radial and axial diffusivities, and correlation with reading development

Using diffusion tensor MR imaging (DTI) and advanced voxel-wise analysis tools, we study diffusivity and anisotropy changes of white matter from late childhood to young adulthood, and correlate quantitative diffusion indices with Chinese and English reading performance scores. Seventy-five normal healthy school going ethnic Chinese students and young adults of three age groups were recruited (group 1, n=24, mean+/-SD=7.4+/-0.3 years; group 2, n=27, mean+/-SD=10.3+/-0.5 years; group 3, n=24, mean+/-SD=22.8+/-2.3 years). DTI was performed with 3 mm isotropic resolution to cover the entire brain. Voxel-wise analysis was performed using Tract-Based Spatial Statistics (TBSS) to localize regions of white matter showing significant changes of fractional anisotropy (FA), mean diffusivity (MD), and axial and radial diffusivities between groups. We found increased FA and decreased MD with increasing age in regions of cerebellar white matter, right temporal white matter, and a large portion of the superior frontal and parietal white matter driven by both the reduction of radial diffusivity and axial diffusivity with the former to a greater extent. Changes were continual from late childhood to young adulthood. Findings were confirmed by region-of-interest analysis in specific white matter tracts. After controlling for the effect of age, significant correlation was found between diffusion indices of the anterior limb of the left internal capsule and Chinese reading score (p=0.05), and of the corona radiata and English reading score (p=0.026 and p=0.029 for left and right, respectively).These DTI indices likely reflect the multiple biological processes that occur during brain development which provide the neural substrate for ongoing functional connectivity including for reading development.     

In vitro activity and fecal concentration of rifaximin after oral administration

Rifaximin showed moderately high MICs (the MIC at which 90% of the isolates tested were inhibited = 50 microg/ml) for 145 bacterial enteropathogens from patients with traveler's diarrhea acquired in Mexico during the summers of 1997 and 1998. Rifaximin concentrations in stool the day after oral administration (800 mg daily for 3 days) were high (average, 7,961 microg/g), proving the value of the drug.     

中枢神经系统黑色素细胞肿瘤的影像学诊断

目的:探讨中枢神经系统黑色素细胞肿瘤的影像学表现,以期提高认识。方法:收集经手术病理证实的中枢神经系统黑色素细胞肿瘤28例,分析其CT和MRI表现,并结合手术病理进行分析。结果:中枢神经系统黑色素瘤好发于中、青年,男性常见,临床上以颅内压增高症状最多见,其次是视力障碍和意识丧失。肿瘤体积较大,多见于脑外或髓外、脑内或髓内邻近表面。肿瘤为实质性肿块,大小不一,瘤内成分复杂,常见出血、坏死、囊变等。CT和MRI表现根据肿瘤的成分不同而异,典型者为CT高密度类似出血,MRI呈现T₁WI高信号、T₂WI低信号,FLAIR和DWI亦呈低信号。实质部分常有均匀或不均匀的增强。囊变/坏死或出血无强化。有轻度至中度瘤周水肿,有时伴有脑组织浸润。MRS呈现肿瘤波谱,但并不典型。结论:颅内黑色素瘤有特殊的影像学表现,CT和MRI结合可以明确诊断。     

FRZB up-regulation is correlated with hepatic metastasis and poor prognosis in colon carcinoma patients with hepatic metastasis

Frizzled-related protein (FRZB) was up-regulated in hepatic metastasis samples compared with primary colon cancer samples in our previous work. However, the clinical relevance of FRZB in colon cancer hepatic metastasis remains uncertain. The aim of this study was to assess the prognostic value of FRZB in patients with colon carcinoma hepatic metastasis after hepatic resection. FRZB expression was evaluated by immunohistochemistry in formalin-fixed paraffin embedded (FFPE) primary colon carcinoma and paired hepatic metastasis tissues from 136 patients with liver metastasis from colon carcinoma that underwent hepatic resection. The relation between FRZB expression and clinicopathologic factors and long-term prognosis in these 136 patients was retrospectively examined. The prognostic significance of negative or positive FRZB exspression in colon carcinoma hepatic metastasis was assessed using Kaplan-Meier survival analysis and log-rank tests. Positive expression of FRZB was correlated with liver metastasis of colon cancer. Univariate analysis indicated significantly worse overall survival (OS) for patients with a positive FRZB expression in colon carcinoma hepatic metastasis than for patients with a negative FRZB expression. Multivariate analysis showed positive-FRZB in colon carcinoma hepatic metastasis to be an independent prognostic factor for OS after hepatic resection (P = 0.001). Positive expression of FRZB was statistically significantly associated with poor prognosis of patients with colon carcinoma hepatic metastasis. FRZB could be a novel predictor for poor prognosis of patients with colon carcinoma hepatic metastasis after hepatic resection.     

Prognostic significance of microRNA-203 in cholangiocarcinoma

MircroRNA functions as a tumor suppressor or a promoter in cholangiocarcinoma (CCA). Researchers have found that miR-203 functioned as tumor suppressor in many types of cancer. However, the role of miR-203 that plays in CCA remains to be clarified. We aimed to detect the expression level and the prognostic significance of miR-203 in CCA tissues. qRT-RCR was performed to examine the miR-203 expression levels in CCA tissue specimens and corresponding normal tissues. Our findings suggest that miR-203 expression was an independent poor prognostic factor for CCA patient overall survival. Therefore, miR-203 may serve as a valuable prognostic marker and promising treatment target for CCA.     

Inhibition of SALL4 suppresses carcinogenesis of colorectal cancer via regulating Gli1 expression

Background: SALL4 is a novel oncogene mediating tumorigenesis in multiple carcinomas. However, its actual role and mechanisms participating in the development of colorectal cancer remains unclear. Methods: Immunohistochemical staining and Western blot were conducted to detect the expression of SALL4 and other molecules. siRNA of SALL4 was transfected to silence SALL4 expression in Caco-2 cell line. Flow cytometry was used for cell cycle and apoptosis analysis. Wound healing and transwell assay were used for invasion test. CCK-8 test was employed for cell proliferation and drug sensitivity assessment. Results: By inhibition of SALL4 expression, the proliferation, invasiveness and drug resistance were dramatically reduced while apoptosis rate was up-regulated. Gli1 was found to decrease its expression in SALL4 silencing cells. Moreover, the inhibition on tumorigenesis of Caco-2 by SALL4 silencing was antagonized by Gli1 up-regulation, suggesting Gli1 as a downstream target of SALL4 in cancer development. Conclusion: SALL4 inhibition limited oncogenesis on colorectal cancer by reducing Gli1 expression.     

MRI和高频超声对踝关节外侧副韧带损伤的诊断价值比较

目的:探讨MPd和高频超声对踝关节外侧副韧带损伤的诊断价值。材料与方法:采用1.5T磁共振及高频超声对95例临床怀疑踝关节侧副韧带损伤患者进行检查,对54例经手术治疗患者的检查结果与手术结果进行比较。结果:以手术结果为标准MPd诊断韧带损伤的敏感性、特异性、准确率分别为92%,100%,95%;超声诊断韧带损伤的敏感性、特异性、准确率分别为84%,93%,88%;54例侧副韧带损伤中,Ⅱ级损伤20例,Ⅲ级损伤34例,以手术结果为标准,高频超声诊断韧带Ⅱ、Ⅲ级损伤的符合率为70%,85%,MRI诊断韧带Ⅱ、Ⅲ级损伤的符合率为75%,94%。结论:MRI和高频超声对于踝关节外侧副韧带损伤的诊断均具有有较高的诊断效能,有助于准确分期,为临床早期治疗及康复提供客观依据。