Abstract:
:A significant timer error has been found on a linear accelerator used for intraoperative radiation therapy. Since typical treatment doses range up to 20 Gy, calibrations that do not account for this effect can incur a large dosimetry error. The effect is dose rate dependent, but energy independent. For a dose rate of 900 cGy min(-1), the error in dose calibration varies between 2 and 3% for an average of 2.5%. At dose rates of 600 and 300 cGy min(-1), the error was 1.7% and 0.8% respectively. The average timer error at 900 cGy min(-1) was found to be 1.2 +/- 0.1 monitor units. It is argued that even a small timer error has serious dosimetry consequences for the implementation of intensity modulated radiation therapy.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Biggs PJdoi
10.1088/0031-9155/43/10/031subject
Has Abstractpub_date
1998-10-01 00:00:00pages
3139-43issue
10eissn
0031-9155issn
1361-6560journal_volume
43pub_type
杂志文章abstract::The artificial urinary sphincter should be long enough to prevent strangulation effects of the urethral tissue and short enough to avoid the improper dissection of the surrounding tissue. To optimize the sphincter length, the empirical three-parameter urethra compression model is proposed based on the mechanical prope...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/51/5/023
更新日期:2006-03-07 00:00:00
abstract::Absorbed dose values were determined under the reference conditions in a phantom irradiated by high-energy photon beams with quality varying between 60Co gamma rays and 25 MV X-rays, using four commonly employed types of ionisation chamber. The ionisation chamber readings were converted to absorbed dose values applyin...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/31/4/006
更新日期:1986-04-01 00:00:00
abstract::Spectral x-ray imaging using novel photon counting x-ray detectors (PCDs) with energy resolving abilities is capable of providing energy-selective images. PCDs have energy thresholds, enabling the classification of photons into multiple energy bins. The extra energy information provided may allow materials such as iod...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/56/18/012
更新日期:2011-09-21 00:00:00
abstract::Clinical studies have established a strong benefit from adjuvant mild hyperthermia (HT) to radio- and chemotherapy for many tumor sites, including the head and neck (H&N). The recently developed HYPERcollar allows the application of local radiofrequency HT to tumors in the entire H&N. Treatment quality is optimized us...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/9/2139
更新日期:2014-05-07 00:00:00
abstract::Radiotherapy calculations often involve complex geometries such as interfaces between materials of vastly differing atomic number, such as lung, bone and/or air interfaces. Monte Carlo methods have been used to calculate accurately the perturbation effects of the interfaces. However, these methods can be computational...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/51/9/010
更新日期:2006-05-07 00:00:00
abstract::For PET online data acquisition, a centralized coincidence processor (CCP) with a single-thread data processing has been used to select coincidence events for many PET scanners. CCP has the advantage of highly integrated circuit, compact connection between detector front-end and system electronics, and centralized con...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/abde85
更新日期:2021-01-21 00:00:00
abstract::Two experimental investigations of the electromagnetic method to measure body composition are presented. In the first experiment, the impedance of a single-loop transmitting antenna, located at the centre of a 150 m helical receiving coil, was observed to have a sharp minimum at 2.40 MHz. The impedance of the antenna ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/40/4/011
更新日期:1995-04-01 00:00:00
abstract::The performance of a light sharing and recirculation mechanism that allows the extraction of depth of interaction (DOI) are investigated in this paper, with a particular focus on timing. In parallel, a method to optimize the coincidence time resolution (CTR) of PET detectors by use of the DOI information is proposed a...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab2cb0
更新日期:2019-08-07 00:00:00
abstract::In response to the recognized fragility of reactor-produced (99)Mo supply, direct production of (99m)Tc via (100)Mo(p,2n)(99m)Tc reaction using medical cyclotrons has been investigated. However, due to the existence of other Molybdenum (Mo) isotopes in the target, in parallel with (99m)Tc, other technetium (Tc) radioa...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/2/542
更新日期:2016-01-21 00:00:00
abstract::All radiation therapy treatment planning relies on accurate dose calculation. Uncertainties in dosimetric prediction can significantly degrade an otherwise optimal plan. In this work, we introduce a robust optimization method which handles dosimetric errors and warrants for high-quality IMRT plans. Unlike other dose e...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/54/11/010
更新日期:2009-06-07 00:00:00
abstract::In digital breast tomosynthesis (DBT), image characteristics of projection views and reconstructed volume are different and both have the advantage of detecting breast masses, e.g. reconstructed volume mitigates a tissue overlap, while projection views have less reconstruction blur artifacts. In this paper, an improve...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/22/8809
更新日期:2015-11-21 00:00:00
abstract::Delivering accurate radiation dose to blood specimens during biological irradiations is essential in quantifying damage of ionizing radiation. To estimate dose to blood samples as accurately as possible, pieces of EBT2 model GAFCHROMIC™ film were placed within an approximately 10 mm finely ground rice layer that was u...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/10/3177
更新日期:2013-05-21 00:00:00
abstract::Respiratory motion in emission tomography leads to reduced image quality. Developed correction methodology has been concentrating on the use of respiratory synchronized acquisitions leading to gated frames. Such frames, however, are of low signal-to-noise ratio as a result of containing reduced statistics. In this wor...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/52/17/006
更新日期:2007-09-07 00:00:00
abstract::Blood and blood products are irradiated with gamma rays to reduce the risk of graft versus host disease (GVHD). A simple technique using electron beams produced by a medical linear accelerator has been studied to evaluate irradiation of blood and blood products. Variations in applied doses for a single field 20 MeV el...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/45/11/401
更新日期:2000-11-01 00:00:00
abstract::Measurements of standardized uptake values (SUV) can vary due to many causes, including respiratory motion. Various methodologies have been introduced to correct for motion in PET, with quiescent-period-gated (QPG) PET being the most popular approach. QPG has been shown to improve PET image quantification compared to ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab1cdd
更新日期:2019-05-16 00:00:00
abstract::A single experimental apparatus has been designed to allow measurements of stopping cross-sections of materials in liquid and vapour phase, for alpha particles, using an indirect method. The method, in which residual energies for increasing absorber thicknesses are obtained and differentiated, has been used in a numbe...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/25/5/004
更新日期:1980-09-01 00:00:00
abstract::This paper reports an inverse arc-modulated radiation therapy planning technique based on linear models. It is implemented with a two-step procedure. First, fluence maps for 36 fixed-gantry beams are generated using a linear model-based intensity-modulated radiation therapy (IMRT) optimization algorithm. The 2D fluenc...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/55/13/020
更新日期:2010-07-07 00:00:00
abstract::For patients with partial epilepsy, automatic spike detection techniques applied to interictal MEG data often discover several potentially epileptogenic brain regions. An important determination in treatment planning is which of these detected regions are most likely to be the primary sources of epileptogenic activity...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/50/14/017
更新日期:2005-07-21 00:00:00
abstract::With the addition of variable bed speed capabilities, continuous bed motion (CBM) becomes an acquisition generalization for axial sensitivity modeling and therefore a flexible tool in axial local image quality adjustment. In this paper, we describe the principles behind CBM mode planning and its influence on image rec...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/20/6153
更新日期:2014-10-21 00:00:00
abstract::Remission spectroscopy in living tissues can only be performed because scattering processes induce a pronounced amount of backscattered light. New types of scattering chambers were constructed in order to investigate the angular distribution of light intensities caused by scattering events typical for living tissues. ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/34/12/012
更新日期:1989-12-01 00:00:00
abstract::The energy dependence of alanine/EPR dosimetry, in terms of absorbed dose-to-water for clinical 6, 10, 25 MV x-rays and 60Co gamma-rays was investigated by measurements and Monte Carlo (MC) calculations. The dose rates were traceable to the NRC primary standard for absorbed dose, a sealed water calorimetry. The electr...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/49/2/006
更新日期:2004-01-21 00:00:00
abstract::The delivery of volumetric modulated arc therapy (VMAT) requires the simultaneous movement of the linear accelerator gantry, multi-leaf collimators and jaws while the dose rate is varied. In this study, a VMAT delivery emulator was developed to accurately predict the characteristics of a given treatment plan, incorpor...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/56/13/024
更新日期:2011-07-07 00:00:00
abstract::There is a need to verify the accuracy of general purpose Monte Carlo codes like EGSnrc, which are commonly employed for investigations of dosimetric problems in radiation therapy. A number of experimental benchmarks have been published to compare calculated values of absorbed dose to experimentally determined values....
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/19/7637
更新日期:2015-10-07 00:00:00
abstract::Treatment planning for proton tumor therapy requires a fast and accurate dose-calculation method. We have implemented a simplified Monte Carlo (SMC) method in the treatment planning system of the National Cancer Center Hospital East for the double-scattering beam delivery scheme. The SMC method takes into account the ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/55/12/018
更新日期:2010-06-21 00:00:00
abstract::Gel dosimetry based on magnetic resonance imaging (MRI) has previously been shown to provide verification of calculated dose distributions in soft tissue equivalent homogeneous phantoms. This study demonstrates how measurements of dose distribution can also be achieved in a phantom containing porous, lung-equivalent, ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/45/10/303
更新日期:2000-10-01 00:00:00
abstract::This paper presents a description of tests carried out to compare the behaviour of five algorithms in inverse radiation therapy planning: (1) The Dynamically Penalized Likelihood (DPL), an algorithm based on statistical estimation theory; (2) an accelerated version of the same algorithm: (3) a new fast adaptive simula...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/46/10/309
更新日期:2001-10-01 00:00:00
abstract::The purpose of this study was to determine the performance of a single lutetium oxy-orthosilicate (LSO) crystal layer High Resolution Research Tomograph (HRRT) positron emission tomography (PET) scanner. The HRRT is a high resolution PET scanner designed for human brain and small animal imaging. The scanner consists o...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/48/4/302
更新日期:2003-02-21 00:00:00
abstract::This work compared the impact of x-ray tube performance and automatic dose rate control (ADRC) parameter selection on system imaging efficiency of two Siemens angiography systems: a Siemens Megalix x-ray tube installed on an Artis Zee system (denoted 'MEGALIX') and a newer generation Gigalix x-ray tube installed on an...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/abbb7a
更新日期:2020-11-24 00:00:00
abstract::Segmented attenuation correction is now a widely accepted technique to reduce noise propagation from transmission scanning in positron emission tomography (PET). In this paper, we present a new method for segmenting transmission images in whole-body scanning. This reduces the noise in the correction maps while still c...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/47/7/310
更新日期:2002-04-07 00:00:00
abstract::Results from dielectric studies on the freshwater fish Cyprinus carpio exposed to a sublethal concentration of sodium alkyl benzene sulphonate were compared with those from untreated control fish; recovery from the test solution was also checked. The influence of the anionic detergent on the intracellular matter of fi...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/29/5/005
更新日期:1984-05-01 00:00:00