Abstract：
:Orthovoltage x-ray beams exhibit the characteristic of depth dose buildup which is not well described in the literature. The principal reason for this phenomenon is the increase in dose deposited due to electrons set in motion by secondary (Compton) scattered photons within the phantom, as depth is increased until longitudinal equilibrium is reached. This happens within a few millimetres of the surface and has been demonstrated both experimentally and by Monte Carlo methods. The Monte Carlo technique also enabled description of a second order primary dose buildup effect (due to longitudinal electronic disequilibrium) that would be impossible to detect with conventional detectors due to the short range of the electrons. The magnitude of buildup was observed to alter with various combinations of beam parameters. Variations will also occur with detectors used to measure buildup. It is recommended that radiation oncology departments assess this effect in the context of their clinical data in current use to ensure that there are not doses higher than prescribed being applied a few millimetres below the skin surface, especially if data was collected with a thin windowed, parallel plate ionisation chamber and/or that coarse steps for depth dose data collection were used along the beam central axis.
journal_name
Australas Phys Eng Sci Medjournal_title
Australasian physical & engineering sciences in medicineauthors
Hill RF,Keall PJ,Beckham WA,Perez MDsubject
Has Abstractpub_date
1998-06-01 00:00:00pages
51-6issue
2eissn
0158-9938issn
1879-5447journal_volume
21pub_type
杂志文章abstract：:Three different air channels were constructed in solid water. These resemble upper respiratory and larynx geometry. Central-axis depth-dose distributions were measured on and beyond the distal surface of the air cavities. The measurements were made with a parallel-plate Markus ionisation chamber and TLDs for 6 and 25 ...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：
更新日期：1996-12-01 00:00:00
abstract：:Gating is a relatively new and potentially useful therapeutic addition to external beam radiotherapy applied to regions affected by intra-fraction motion. The impact was of gating on treatment margins, image artifacts, and volume and positional accuracy was investigated by CT imaging of sinusoidally moving spheres. Th...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/BF03178368
更新日期：2002-03-01 00:00:00
abstract：:Numerical simulation is performed to demonstrate that hemodynamic factors are significant determinants for the development of a vascular pathology. Experimental measurements by particle image velocimetry are carried out to validate the credibility of the computational approach. We present a study for determining compl...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/s13246-010-0050-4
更新日期：2010-12-01 00:00:00
abstract：:It has long been recognized that the assessment of Automatic Exposure Control (AEC) function is an important criterion in the assessment of any general radiographic x-ray installation. Of the tests commonly performed on an AEC, only Beam Quality Dependence relates intimately with the optical density produced on the re...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：
更新日期：1997-09-01 00:00:00
abstract：:AFOMP recognizes that clinical medical physicists should demonstrate that they are competent to practice their profession by obtaining appropriate education, training and supervised experience in the specialties of medical physics in which they practice, as well as having a basic knowledge of other specialties. To hel...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章,评审
doi：10.1007/s13246-011-0091-3
更新日期：2011-09-01 00:00:00
abstract：:This study was aimed to improve the surgical accuracy of plating and screwing for complicated tibial plateau fracture assisted by 3D implants library and 3D-printed navigational template. Clinical cases were performed whereby complicated tibial plateau fractures were imaged using computed tomography and reconstructed ...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/s13246-015-0330-0
更新日期：2015-03-01 00:00:00
abstract：:Calculations have been performed of the kerma to radiographic film and to silicon from a number of x-ray spectra generated at 30 to 140 kV with tungsten and molybdenum targets. These results have been compared with the air-kerma values due to the same beams. It is concluded that both film and silicon can be used as pr...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：
更新日期：1992-12-01 00:00:00
abstract：:Ischaemic stroke is a major public health issue in both developed and developing nations. Hypothermia is believed to be neuroprotective in cerebral ischaemia. Conversely, elevated brain temperature is associated with poor outcome after ischaemic stroke. Mechanisms of heat exchange in normally-perfused brain are relati...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/s13246-017-0595-6
更新日期：2017-12-01 00:00:00
abstract：:Rats are often used in the electromagnetic field (EMF) exposure experiments. In the study for the effect of 900 MHz EMF exposure on learning and memory in SD rats, the specific absorption rate (SAR) and the temperature rise in the rat head are numerically evaluated. The digital anatomical model of a SD rat is reconstr...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/s13246-013-0202-4
更新日期：2013-06-01 00:00:00
abstract：:A set of four 4 MV photon beam compensators were produced, one for each field of a Hodgkins Disease treatment plan. The resultant dose profiles at various depths were measured by an ion chamber in water and by Kodak X-Omat V film in a Solid Water phantom, and compared to the doses calculated by a GE RT/Plan treatment ...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：
更新日期：1992-03-01 00:00:00
abstract：:Given that there is increasing recognition of the effect that sub-millimetre changes in collimator position can have on radiotherapy beam dosimetry, this study aimed to evaluate the potential variability in small field collimation that may exist between otherwise matched linacs. Field sizes and field output factors we...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/s13246-015-0349-2
更新日期：2015-06-01 00:00:00
abstract：:X-ray transmission tests were performed on a Green-Lite (Infab Corporation) apron/vest combination, and compared to a number of other apron/vest combinations routinely used at Christchurch Hospital as well as a sheet of 0.5 mm lead. The materials were X-rayed using the primary beam of a Philips Optimus 50 X-ray machin...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/BF03178704
更新日期：2005-06-01 00:00:00
abstract：:This paper describes a software tool developed for research into the use of an electronic portal imaging device (EPID) to verify dose for intensity modulated radiation therapy (IMRT) beams. A portal dose image prediction (PDIP) model that predicts the EPID response to IMRT beams has been implemented into a commerciall...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/BF03179347
更新日期：2008-09-01 00:00:00
abstract：:A electrocardiogram (ECG) central station has been developed for the Intensive Care Unit at Christchurch Hospital. The system allows the selection and display of four ECGs selected from seven bedside monitors in the Unit. It also provides for automatic display, hard copy and audio alarm of ECG from any monitor which h...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：
更新日期：1990-03-01 00:00:00
abstract：:The effects of internal and external scatter on surface, build-up and depth dose characteristics simulated by Monte Carlo code EGSnrc for varying field size and SSD for a 10 MeV monoenergetic electron beam with and without an accelerator model are extensively studied in this paper. In particular, sub-millimetre surfac...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/BF03178710
更新日期：2005-09-01 00:00:00
abstract：:Properties of a new polymer gel with cross-linked polyvinyl alcohol as a gelatinous matrix were investigated. The new polymer gel dosimeter was named PVABAT. The irradiation was performed using a calibrated 60Co beam. The dose responses of the PVABAT formulations were quantified with MRI transverse relaxation rate (R2...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/s13246-017-0573-z
更新日期：2017-09-01 00:00:00
abstract：:Helical tomotherapy (HT) is a novel radiotherapy treatment modality that allows the delivery of intensity modulated radiation in a rotational fashion. Due to the complexity of the treatment approach, it is desirable to have a simple tool for treatment delivery verification. Radiographic film placed under the patient i...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/BF03178723
更新日期：2005-12-01 00:00:00
abstract：:Accuracy of dwell position and reproducibility of dwell time are critical in high dose rate (HDR) brachytherapy. A phantom was designed to verify dwell position and dwell time reproducibility for an Ir-192 HDR stepping source using Computed Radiography (CR). The central part of the phantom, incorporating thin alternat...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/s13246-012-0138-0
更新日期：2012-09-01 00:00:00
abstract：:There are many examples of technology transfer from astronomy to medicine, for example algorithms for reconstructing X-ray CT images were first developed for processing radio astronomy images. In more recent times, X-ray detectors developed for the Hubble Space Telescope have been used in a fine-needle breast biopsy s...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/BF03178440
更新日期：2007-12-01 00:00:00
abstract：:A solid water breast phantom with a lung equivalent material was constructed to investigate interface effects of 6 MV tangential photon fields. The phantom was built so that Thermo-luminescence Dosimeters (TLD) could be used for comparison to a pencil beam and Equivalent Tissue-Air-Ratio (ETAR) algorithms. The investi...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：
更新日期：1998-03-01 00:00:00
abstract：:Super-pixel feature extraction is a key problem to get an acceptable performance in color super-pixel classification. Given a color feature extraction problem, it is necessary to know which is the best approach to solve this problem. In the current work, we're interested in the challenge of nucleus and cytoplasm autom...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/s13246-019-00735-8
更新日期：2019-06-01 00:00:00
abstract：:This article outlines the enormous technological advances that have taken place in the practice of radiology in Australasia in the 30 years since approximately 1977. These developments have led to significant improvements in image quality across all modalities, including even general radiography, which had as its gene...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章,评审
doi：10.1007/BF03178423
更新日期：2007-09-01 00:00:00
abstract：:The effective energy of diagnostic X-rays is important for quality assurance (QA) and quality control (QC). However, the half-value layer (HVL), which is necessary to evaluate the effective energy, is not ubiquitously monitored because ionization-chamber dosimetry is time-consuming and complicated. To verify the appli...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/BF03178625
更新日期：2009-03-01 00:00:00
abstract：:Diamond detectors are particularly well suited for dosimetry applications in radiotherapy for reasons including near-tissue equivalence and high-spatial resolution resulting from small sensitive volumes. However, these detectors have not become commonplace due to high cost and poor availability arising from the need f...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/s13246-010-0040-6
更新日期：2010-12-01 00:00:00
abstract：:The reliability of the traditional Cobb angle index, which at present exhibits a wide range of reported values, was determined in this study and amounted to a within subject error of +/-4.3 degrees and a between subject error of +/-4.9 degrees. An attempt to pinpoint the source of this variability by investigating the...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：
更新日期：1989-03-01 00:00:00
abstract：:Shear wave elasticity imaging (SWEI) has been used to measure the local tissue elasticity. The local tissue shear modulus can be reconstructed from the displacement field of shear waves using an algebraic Helmholtz inversion (AHI) equation or a time-of-flight (TOF)-based algorithm. The shear waves, which are generated...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/s13246-019-00748-3
更新日期：2019-09-01 00:00:00
abstract：:Large differences in monitor units have been observed when RadCalc, a pencil-beam-algorithm based software, is used to verify clinical electron plans from Raystation, a Monte-Carlo-algorithm based planning system. To investigate the problem, a number of clinical plans as well as test plans were created and calculated ...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/s13246-016-0470-x
更新日期：2016-09-01 00:00:00
abstract：:X-ray imaging of the chest is challenging because of the large differences in x-ray attenuation between the mediastinal and lung regions of the chest. This large dynamic range of chest exit exposure, along with associated large changes in the scatter component of the beam, makes film based chest imaging difficult to o...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：
更新日期：1993-12-01 00:00:00
abstract：:Most of the human head models used in dipole localisation research, which have been reported in the literature to date, assume a simplified cranial structure wherein the head is modelled as a set of distinct homogenous tissue compartments. The inherent inhomogeneity of the tissues has so far been ignored in these mode...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/BF03178283
更新日期：2001-03-01 00:00:00
abstract：:Regular checks on the performance of radiotherapy treatment units are essential and a variety of protocols has been published. These protocols identify that the determination of isocentre must be accurate and unambiguous since both the localization of a radiation field on a patient and positioning aids are referenced ...
journal_title：Australasian physical & engineering sciences in medicine
pub_type： 杂志文章
doi：10.1007/BF03178670
更新日期：2004-09-01 00:00:00
