Millimeter wave depolarization and attenuation in storm layers containing ellipsoidal and spheroidal particles

118-125Theoretical investigation has been carried out to evaluate the depolarization of millimeter wave from the layers of three main constituents (sand, silt and clay) of storm. Both ellipsoidal and spheroidal (prolate and oblate) shape of dust particles are considered. The concept of differential phase and differential attenuation has been utilized to quantify the depolarization. It has been found that, in general, differential attenuation, depolarization angle depolarization and loss due to depolarization produced by ellipsoidal dust particles are higher than those produced by the spheroidal dust particles. The prolate spheroidal dust particles are found to cause more depolarization and attenuation as compared to those by oblate spheroidal dust particles. It has also been observed that the depolarization and loss due to depolarization caused by ellipsoidal and spheroidal dust particles depend directly on frequency and particle density

Brain tumor acidification using drugs simultaneously targeting multiple pH regulatory mechanisms

© 2019, Springer Science+Business Media, LLC, part of Springer Nature. Introduction: Non-invasively distinguishing aggressive from non-aggressive brain tumors is an important clinical challenge. Intracellular pH (pHi) regulation is essential for normal cell function and is normally maintained within a narrow range. Cancer cells are characterized by a reversed intracellular to extracellular pH gradient, compared to healthy cells, that is maintained by several distinct mechanisms. Previous studies have demonstrated acute pH modulation in glioblastoma detectable by chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) after blocking individual pH regulatory mechanisms. The purpose of the current study was to simultaneously block five pH regulatory mechanisms while also providing glucose as an energy substrate. We hypothesized that this approach would increase the acute pH modulation effect allowing the identification of aggressive cancer. Methods: Using a 9.4 T MRI scanner, CEST spectra were acquired sensitive to pHi using amine/amide concentration independent detection (AACID). Twelve mice were scanned approximately 11 ± 1 days after implanting 105 U87 human glioblastoma multiforme cells in the brain, before and after intraperitoneal injection of a combination of five drugs (quercetin, cariporide, dichloroacetate, acetazolamide, and pantoprazole) with and without glucose. Results: Two hours after combination drug injection there was a significant 0.1 ± 0.03 increase in tumor AACID value corresponding to a 0.4 decrease in pHi. After injecting the drug combination with glucose the AACID value increased by 0.18 ± 0.03 corresponding to a 0.72 decrease in pHi. AACID values were also slightly increased in contralateral tissue. Conclusions: The combined drug treatment with glucose produced a large acute CEST MRI contrast indicating tumor acidification, which could be used to help localize brain cancer and monitor tumor response to chemotherapy