Read by QxMD icon Read

ionization chamber

Yoshiaki Morishima, Koichi Chida, Yoshikazu Muroya, Yoshiya Utsumi
Interventional radiology procedures often involve lengthy exposure to fluoroscopy-derived radiation. We therefore devised a videofluoroscopic swallowing study (VFSS) procedure using a human phantom that proved to protect the patient and physician by reducing the radiation dose. We evaluated a new lead-shielding device and separately attached additional filters (1.0-, 2.0-, and 3.0-mm Al filters and a 0.5-mm Cu filter) during VFSS to reduce the patient's entrance skin dose (ESD). A monitor attached to the human phantom's neck measured the ESD...
September 18, 2017: Dysphagia
Bryan R Muir, Malcolm R McEwen
PURPOSE: To investigate the use of cylindrical chambers for electron beam dosimetry independent of energy by studying the variability of relative ion chamber perturbation corrections, one of the main concerns for electron beam dosimetry with cylindrical chambers. METHODS: Measurements are made with sets of cylindrical and plane-parallel reference-class chambers as a function of depth in water in 8 MeV and 18 MeV electron beams. The ratio of chamber readings for similar chambers is normalized in a high-energy electron beam and can be thought of as relative perturbation corrections...
September 14, 2017: Medical Physics
Elizabeth Dhummakupt, Phillip M Mach, Daniel Carmany, Paul Demond, Theodore Moran, Theresa Connell, Harold Wylie, Nicholas E Manicke, J Michael Nilles, Trevor Glaros
Paper spray ionization mass spectrometry (PS-MS) offers a rapid alternative platform requiring no sample preparation. Aerosolized CWA simulants, trimethyl phosphate, dimethyl methylphosphonate, and diisopropyl methylphosphonate, were captured by passing air through a glass fiber filter disk and simultaneously capturing it directly onto a disposable paper spray cartridge. CWA simulants were aerosolized at varying concentrations using an in-house built aerosol chamber. A custom 3D-printed holder was designed and built to facilitate the aerosol capture onto the paper spray cartridges...
September 12, 2017: Analytical Chemistry
Bin Cai, Harold Li, Deshan Yang, Vivian Rodriguez, Austen Curcuru, Yuhe Wang, Jie Wen, Rojano Kashani, Sasa Mutic, Olga Green
PURPOSE: To investigate and characterize the performance of a Multi Leaf Collimator (MLC) designed for Cobalt-60 based MR-guided radiation therapy system in a 0.35T magnetic field. METHODS: The MLC design and unique assembly features in the ViewRay MRIdian system were first reviewed. The RF cage shielding of MLC motor and cables were evaluated using ACR phantoms with real time imaging and quantified by signal-to-noise ratio. The dosimetric characterizations, including the leaf transmission, leaf penumbra, tongue and groove effect, were investigated using radiosensitive films...
September 9, 2017: Medical Physics
Guofeng Weng, Zheyi Liu, Jin Chen, Fangjun Wang, Yuanjiang Pan, Yukui Zhang
There are two challenges in oligonucleotide detection by liquid chromatography coupled with mass spectrometry (LC-MS), the serious ion suppression effects caused by ion-pair reagents and the low detection sensitivity in positive mode MS. In this study, highly concentrated alcohol vapors were introduced into an enclosed electrospray ionization chamber, and oligonucleotides could be well detected in negative mode MS even with 100 mM triethylammonium acetate (TEAA) as an ion-pair reagent. The MS signal intensity was improved 600-fold (for standard oligonucleotide dT15) by the isopropanol vapor assisted electrospray, and effective ion-pair LC separation was feasibly coupled with high-sensitive MS detection...
September 13, 2017: Analytical Chemistry
Martin Pitzer, Kilian Fehre, Maksim Kunitski, Till Jahnke, Lothar Schmidt, Horst Schmidt-Böcking, Reinhard Dörner, Markus Schöffler
This article shows how the COLTRIMS (Cold Target Recoil Ion Momentum Spectroscopy) or the "reaction microscope" technique can be used to distinguish between enantiomers (stereoisomers) of simple chiral species on the level of individual molecules. In this approach, a gaseous molecular jet of the sample expands into a vacuum chamber and intersects with femtosecond (fs) laser pulses. The high intensity of the pulses leads to fast multiple ionization, igniting a so-called Coulomb Explosion that produces several cationic (positively charged) fragments...
August 18, 2017: Journal of Visualized Experiments: JoVE
Daniela Poppinga, Björn Delfs, Jutta Meyners, Dietrich Harder, Björn Poppe, Hui Khee Looe
The first aim of this study has been to extend the systematic experimental study of the field size dependence of the output factor correction for three micro-ionization chambers (PTW 31014, PTW 31022 and IBA Razor chamber), two silicon diodes (PTW 60017 and IBA Razor Diode) and the synthetic diamond detector microDiamond (PTW 60019) in a 6 MV photon beam down to an effective field side length of 2.6mm, and to summarize the present knowledge of this factor by treating it as a function of the dosimetric field size...
August 28, 2017: Zeitschrift Für Medizinische Physik
Andrew W Stevenson, Francesca Di Lillo
It is shown that an extensive set of accurate ionization-chamber measurements with a primary polychromatic synchrotron X-ray beam transmitted through various filter combinations/thicknesses can be used to quite effectively estimate the absolute flux distribution. The basic technique is simple but the `inversion' of the raw data to extract the flux distribution is a fundamentally ill-posed problem. It is demonstrated, using data collected at the Imaging and Medical Beamline (IMBL) of the Australian Synchrotron, that the absolute flux can be quickly and reliably estimated if a suitable choice of filters is made...
September 1, 2017: Journal of Synchrotron Radiation
Malte Gotz, Leonhard Karsch, Jörg Pawelke
In order to describe the volume recombination in a pulsed radiation field of high dose-per-pulse this study presents a numerical solution of a 1-D transport model of the liberated charges in a plane-parallel ionization chamber. In addition, measurements were performed on an Advanced Markus ionization chamber in a pulsed electron beam to obtain suitable data to test the calculation. The experiment used radiation pulses of 4 μs duration and variable dose-per-pulse values up to about 1 Gy, as well as pulses of variable duration up to 308 μs at constant dose-per-pulse values between 85 mGy and 400 mGy...
August 31, 2017: Physics in Medicine and Biology
Jochen Hinkelbein, Stefanie Jansen, Ivan Iovino, Silvia Kruse, Moritz Meyer, Fabrizio Cirillo, Hendrik Drinhaus, Andreas Hohn, Corinna Klein, Edoardo De Robertis, Dirk Beutner
Hypobaric hypoxia (HH) during airline travel induces several (patho-) physiological reactions in the human body. Whereas severe hypoxia is investigated thoroughly, very little is known about effects of moderate or short-term hypoxia, e.g. during airline flights. The aim of the present study was to analyse changes in serum protein expression and activation of signalling cascades in human volunteers staying for 30 min in a simulated altitude equivalent to airline travel. After approval of the local ethics committee, 10 participants were exposed to moderate hypoxia (simulation of 2400 m or 8000 ft for 30 min) in a hypobaric pressure chamber...
August 31, 2017: International Journal of Molecular Sciences
Robert Popp, Huiyan Li, André LeBlanc, Yassene Mohammed, Adriana Aguilar-Mahecha, Andrew G Chambers, Cathy Lan, Oliver Poetz, Mark Basik, Gerald Batist, Christoph H Borchers
The PI3K/AKT/mTOR pathway is one of the most commonly dysregulated signaling pathways that is linked to cancer development and progression, and its quantitative protein analysis holds the promise to facilitate patient stratification for targeted therapies. Whereas immunohistochemistry (IHC) and immunoassays are routinely used for clinical analysis of signaling pathways, mass spectrometry-based approaches such as liquid chromatography electrospray ionization-multiple reaction monitoring (LC/ESI-MRM) are more commonly used in clinical research...
August 30, 2017: Analytical Chemistry
T Pfeiler, C Bäumer, E Engwall, D Geismar, B Spaan, B Timmermann
Respiratory induced organ motion poses a major challenge for high-precision radiotherapy such as pencil beam scanning proton therapy (PBS). In order to employ PBS for target regions affected by respiratory motion, the implementation of dedicated motion mitigation techniques should be considered and residual uncertainties need to be assessed. For the latter purpose, a routine simulating the delivery of a scanned proton beam to a moving target was developed and implemented in the commercial treatment planning system RayStation...
August 23, 2017: Zeitschrift Für Medizinische Physik
Jianqiang Zhu, Shuyan Wang, Narcisse T Tsona, Xiaotong Jiang, Yifeng Wang, Maofa Ge, Lin Du
Rate constants at room temperature (293 ± 2 K) and atmospheric pressure for the reaction of methyl n-propyl ether (MnPE), CH3OCH2CH2CH3, with OH and NO3 radicals and the Cl atom have been determined in a 100 L FEP-Teflon reaction chamber in conjunction with gas chromatography-flame ionization detector (GC-FID) as the detection technique. The obtained rate constants k (in units of cm(3) molecule(-1) s(-1)) are (9.91 ± 2.30) × 10(-12), (1.67 ± 0.32) × 10(-15), and (2.52 ± 0.14) × 10(-10) for reactions with OH, NO3, and Cl, respectively...
September 6, 2017: Journal of Physical Chemistry. A
Eduardo R DA Silva, Humberto R Bizzo, Patrícia D Fernandes, Valdir F DA Veiga, Suzana G Leitão, Danilo R DE Oliveira
The bioavailability, toxicity, and therapeutic efficacy of a drug is directly related to its administration route. The pulmonary route can be accessed by inhalation after fumigation, vaporization or nebulization. Thus, pharmacological and toxicological evaluation accessed by an apparatus specifically designed and validated for this type of administration is extremely important. Based on pre-existing models, an inhalation chamber was developed. This presents a central structure with five animal holders. The nebulized air passes directly and continuously through these holders and subsequently to an outlet...
August 17, 2017: Anais da Academia Brasileira de Ciências
Vida Čadež, Srečo D Škapin, Adrijana Leonardi, Igor Križaj, Saša Kazazić, Branka Salopek-Sondi, Ivan Sondi
This study describes and examines the structural and morphological properties of the hierarchically organized, aragonite cuttlebone forms for the common cuttlefish (Sepia officinalis, L.), including its main structural parts, the dorsal shield, and the chambers. Specifically, it complements the mechanism for the self-organized formation of aragonite, identifies the presence, and determines the role of soluble organic matrix (SOM) proteins in the morphogenesis of the cuttlebone's biomineral structures on the nanoscale...
August 10, 2017: Journal of Colloid and Interface Science
Cheng-Chia Wu, Kunal R Chaudhary, Yong Hum Na, David Welch, Paul J Black, Adam M Sonabend, Peter Canoll, Yvonne M Saenger, Tony J C Wang, Cheng-Shie Wuu, Tom K Hei, Simon K Cheng
PURPOSE: To establish a novel preclinical model for stereotactic radiosurgery (SRS) with combined mouselike phantom quality assurance in the setting of brain metastases. METHODS AND MATERIALS: C57B6 mice underwent intracranial injection of B16-F10 melanoma cells. T1-weighted postcontrast magnetic resonance imaging (MRI) was performed on day 11 after injection. The MRI images were fused with cone beam computed tomography (CBCT) images using the Small Animal Radiation Research Platform (SARRP)...
September 1, 2017: International Journal of Radiation Oncology, Biology, Physics
Pascal Hauri, Uwe Schneider
PURPOSE: Long-term survivors of cancer who were treated with radiotherapy are at risk of a radiation-induced tumor. Hence, it is important to model the out-of-field dose resulting from a cancer treatment. These models have to be verified with measurements, due to the small size, the high sensitivity to ionizing radiation and the tissue-equivalent composition, LiF thermoluminescence dosimeters (TLD) are well-suited for out-of-field dose measurements. However, the photon energy variation of the stray dose leads to systematic dose errors caused by the variation in response with radiation energy of the TLDs...
August 11, 2017: Zeitschrift Für Medizinische Physik
K Kristensen, L N Jensen, M Glasius, M Bilde
This study presents a newly constructed temperature controlled cold-room smog chamber at Aarhus University, Denmark. The chamber is herein utilized to study the effect of sub-zero temperature on the formation and chemical composition of secondary organic aerosol (SOA) from ozone initiated oxidation of α-pinene. The chemical composition of α-pinene SOA formed from dark ozonolysis of α-pinene at 293 K and 258 K was investigated using High-Resolution Time-of-Flight Aerosol Mass Spectrometry (HR-ToF-AMS) and Ultra-High Performance Liquid Chromatography/Electrospray Ionization Quadrupole Time-of-Flight Mass Spectrometry (UHPLC/ESI-qToF-MS)...
August 14, 2017: Environmental Science. Processes & Impacts
Jonas Andersson, Heikki Tölli
PURPOSE: The use of liquid ionization chambers can provide useful information to endeavors with radiation dosimetry for highly modulated beams. Liquid ionization chambers may be particularly suitable for computed tomography applications where conventional ionization chambers do not present a high enough sensitivity for the spatial resolution required to characterize common X-ray beams. Due to the sensitivity, which leads to high charge densities, liquid ionization chambers can suffer from large recombination losses leading to degradation in signal to dose rate linearity...
August 12, 2017: Medical Physics
Qingyang Shang, Andrew Godley, Long Huang, Peng Qi, Ping Xia
Using a MatriXX 2D ionization chamber array, we evaluated the detection sensitivity of systematically introduced MLC leaf positioning shifts to test whether the conventional IMRT QA method can be used for quality assurance of an MLC tracking algorithm. Because of finite special resolution, we first tested whether the detection sensitivity was dependent of the locations of leaf shifts and positions of ionization chambers. We then introduced the same systematic leaf shifts in two clinical intensity modulated radiotherapy plans (prostate and head and neck cancer)...
August 11, 2017: Journal of Applied Clinical Medical Physics
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"