Abstract:
:The measurand relevant for the dosimetry for radiation therapy is the absorbed dose to water, DW. The Physikalisch-Technische Bundesanstalt (PTB) is establishing a secondary standard for DW for high-energy photon and electron radiation based on electron spin resonance (ESR) of the amino acid alanine. For practical applications, like, for example, intercomparison measurements using the ESR/alanine dosimetry system, the temporal evolution of the ESR signal of irradiated probes is an important issue. This postirradiation behaviour is investigated for alanine pellets of two different suppliers for different storage conditions. The influence of the storage conditions on the temporal evolution may be dependent on the type of probes used. The measurement and analysis method developed at the PTB is able to circumvent the apparent difficulties in the case of alanine/paraffin probes. Care has to be taken in case this method cannot be applied.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Anton Mdoi
10.1088/0031-9155/53/5/006subject
Has Abstractpub_date
2008-03-07 00:00:00pages
1241-58issue
5eissn
0031-9155issn
1361-6560pii
S0031-9155(08)63403-Xjournal_volume
53pub_type
杂志文章abstract::For quality assurance of hyperthermia treatment planning systems, quantitative validation of the electromagnetic model of an applicator is essential. The objective of this study was to validate a finite-difference time-domain (FDTD) model implementation of the Lucite cone applicator (LCA) for superficial hyperthermia....
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/52/11/010
更新日期:2007-06-07 00:00:00
abstract::Uncemented prosthetic joint implants used in orthopaedic surgery are usually coated with a porous surface to encourage bone ingrowth. Better contact between the endosteal bone and the porous surface improves ingrowth, and such contact may be increased if the joint further subsides into position in the first weeks foll...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/38/2/009
更新日期:1993-02-01 00:00:00
abstract::The convergence rates of the fast Padé transform (FPT) and the fast Fourier transform (FFT) are compared. These two estimators are used to process a time-signal encoded at 4 T by means of one-dimensional magnetic resonance spectroscopy (MRS) for healthy human brain. It is found systematically that at any level of trun...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/50/18/010
更新日期:2005-09-21 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::We assume that the data bits of a pixel in digital images can be divided into signal and noise bits. The signal bits occupy the most significant part of the pixel and the noise bits the least significant part. The signal part of each pixel are correlated while the noise parts are uncorrelated. Two statistical methods,...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/37/2/004
更新日期:1992-02-01 00:00:00
abstract::A simple and fast, but sensitive TLD method for the measurement of energy and homogeneity of therapeutically used electron beams has been developed and tested. This method is based on the fact that when small thicknesses of high-Z absorbers such as lead are interposed in the high-energy electron beams, the transmitted...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/39/9/005
更新日期:1994-09-01 00:00:00
abstract::Speed of sound (SOS) measurements, typically made using 1 MHz broadband pulses, are increasingly used in the clinical diagnosis of bone disorders. Previous in vitro studies indicate that broadband ultrasound pulses are susceptible to distortion in cancellous bone, leading to imprecise arrival time and SOS measurements...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/45/7/317
更新日期:2000-07-01 00:00:00
abstract::Dose reconstruction is a process that re-creates the treatment-time dose deposited in a patient provided there is knowledge of the delivered energy fluence and the patient's anatomy at the time of treatment. A method for reconstructing dose is presented. The process starts with delivery verification, in which the inci...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/46/4/303
更新日期:2001-04-01 00:00:00
abstract::The intra- and inter-batch accuracy and precision of MRI (polyacrylamide gelatin gel fabricated at atmospheric conditions) polymer gel dosimeters are assessed in full 3D. In the intra-batch study, eight spherical flasks were filled with the same polymer gel along with a set of test tubes that served as calibration pha...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/1/19
更新日期:2013-01-07 00:00:00
abstract::This study presents a combined small animal holding fixture system, termed a 'bridge capsule', which provides for small animal re-fixation with positional reproducibility. This system comprises separate holding fixtures for the head and lower body and a connecting part to a gas anesthesia system. A mouse is fixed in p...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/55/14/011
更新日期:2010-07-21 00:00:00
abstract::In proton therapy, the relative biological effectiveness (RBE) depends on various types of parameters such as linear energy transfer (LET). An analytical model for LET calculation exists (Wilkens' model), but secondary particles are not included in this model. In the present study, we propose a correction factor, L se...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/2/740
更新日期:2016-01-21 00:00:00
abstract::In recent codes of practice for reference dosimetry in clinical proton beams using ionization chambers, it is recommended to perform the measurement in a water phantom. However, in situations where the positioning accuracy is very critical, it could be more convenient to perform the measurement in a plastic phantom. I...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/47/17/302
更新日期:2002-09-07 00:00:00
abstract::Single monochromator charge-coupled device (CCD) array spectroradiometers have the advantage of ease of use and speed compared with double grating instruments. Their inherently inferior stray-light rejection, however, can critically affect their accuracy in phototherapy and research-related dosimetry applications. Thi...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/53/18/026
更新日期:2008-09-21 00:00:00
abstract::Previous treatment of cerebrospinal fluid (CSF) malignancies by intrathecal administration of (131)I-radiolabelled monoclonal antibodies has led to the assumption that more healthy tissue will be spared when a pure beta-emitter such as (90)Y replaces (131)I. The purpose of this study is to compare and quantitatively e...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/51/1/014
更新日期:2006-01-07 00:00:00
abstract::Radiochromic films are useful as dosimeters in high-precision radiotherapy owing to their high spatial resolution. However, when a particle beam is measured using a radiochromic film, the dose cannot be estimated accurately because the film darkness varies with variations in linear energy transfer (LET). This paper pr...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab8bf3
更新日期:2020-06-15 00:00:00
abstract::Instead of performing a numerical deconvolution, we propose to use a linear piecewise-continuous model of the renal impulse response function for parametric fitting of renal scintigraphy data, to obtain clinically useful renal parameters. The strengths of the present model are its simplicity and speed of computation, ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/48/12/402
更新日期:2003-06-21 00:00:00
abstract::Inverse treatment planning in intensity modulated particle therapy (IMPT) with scanned carbon-ion beams is currently based on the optimization of RBE-weighted dose to satisfy requirements of target coverage and limited toxicity to organs-at-risk (OARs) and healthy tissues. There are many feasible IMPT plans that meet ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aaf400
更新日期:2019-01-04 00:00:00
abstract::Beam tracking with scanned carbon ion radiotherapy achieves highly conformal target dose by steering carbon pencil beams to follow moving tumors using real-time magnetic deflection and range modulation. The purpose of this study was to evaluate the robustness of target dose coverage from beam tracking in light of posi...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/4/1717
更新日期:2015-02-21 00:00:00
abstract::Noise equivalent count rate (NECR) and image noise are two different but related metrics that have been used to predict and assess image quality, respectively. The aim of this study is to investigate, using patient studies, the relationships between injected dose (ID), body mass index (BMI) and scanner type on NECR an...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/56/16/013
更新日期:2011-08-21 00:00:00
abstract::The external radiation exposure from an overhead plume containing gamma emitting radionuclides can contribute substantial dose to the ground receptor during normal operations as well as accidental release conditions of nuclear facilities. In order to estimate the effective dose conversion coefficients (DCCs) directly,...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab2c92
更新日期:2019-08-01 00:00:00
abstract::An algorithm for dynamic multileaf-collimator (dMLC) tracking of a target performing a known a priori, rigid-body motion during volumetric modulated arc therapy (VMAT), has been experimentally validated and applied to investigate the potential of the Agility (Elekta AB, Stockholm, Sweden) multileaf-collimator (MLC) fo...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/13/4643
更新日期:2013-07-07 00:00:00
abstract::Ultrasoft x-rays of 0.3-5 keV have provided a unique tool for the investigation of intracellular mechanisms of radiation action in biological organisms, including mammalian cells. However, their use presents unique practical problems in dosimetry and experimental design. Detailed interpretation of the biological resul...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/30/10/002
更新日期:1985-10-01 00:00:00
abstract::In this paper, we use a more realistic head model with ovoid geometry for approximation of a human head. By inverting the Geselowitz equation, some analytic results on the inverse MEG problem are presented in homogenous ovoid geometry. On one hand, some information about the components of primary current is shown by t...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/51/21/012
更新日期:2006-11-07 00:00:00
abstract::Measuring spin-spin relaxation times (T2) by quantitative MR imaging represents a potentially efficient tool to evaluate the physicochemical properties of various media. However, noise in MR images is responsible for uncertainties in the determination of T2 relaxation times, which limits the accuracy of parametric tis...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/51/11/011
更新日期:2006-06-07 00:00:00
abstract::A Gaussian convolution kernel K is deduced as a Green's function of a Lie operator series. The deconvolution of a Gaussian kernel is developed by the inverse Green's function K(-1). A practical application is the deconvolution of measured profiles Dm(x) of photons and protons with finite detector size to determine the...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/48/6/302
更新日期:2003-03-21 00:00:00
abstract::Monte Carlo methods have been applied to the study of the performance of antiscatter grids in radiography. Photon histories for imaging with a 20 cm thick water phantom irradiated with an 80 kV x-ray spectrum were generated by Monte Carlo simulation. The scattering and absorption of the photons transmitted from the ph...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/27/6/002
更新日期:1982-06-01 00:00:00
abstract::We investigate an optimization-based reconstruction, with an emphasis on image-artifact reduction, from data collected in C-arm cone-beam computed tomography (CBCT) employed in image-guided interventional procedures. In the study, an image to be reconstructed is formulated as a solution to a convex optimization progra...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/20/7300
更新日期:2016-10-21 00:00:00
abstract::Brain stereotactic radiosurgery (SRS) treatments require multiple quality assurance (QA) procedures to ensure accurate and precise treatment delivery. As single-isocenter multitarget SRS treatments become more popular, the quantification of off-axis accuracy of the linear accelerator is crucial. In this study, a novel...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab8534
更新日期:2020-06-10 00:00:00
abstract::Large volume tissue-equivalent proportional counters are of interest in radiation protection metrology, as the sensitivity in terms of counts per unit absorbed dose in these devices increases as the square of the counter diameter. Conventional solutions to the problem of maintaining a uniform electric field within a c...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/37/10/002
更新日期:1992-10-01 00:00:00
abstract::Dose calculation for radiotherapy with protons and heavier ions deals with a large volume of path integrals involving a scattering power of body tissue. This work provides a simple model for such demanding applications. There is an approximate linearity between RMS end-point displacement and range of incident particle...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/54/5/N01
更新日期:2009-03-07 00:00:00