Abstract:
:Methods based on magnetic resonance imaging for the measurement of three-dimensional distributions of radiation dose are highly developed. However, relatively little work has been done on optical computed tomography (OCT). This paper describes a new OCT scanner based on a broad beam light source and a two-dimensional charge-coupled device (CCD) detector. A number of key design features are discussed including the light source; the scanning tank, turntable and stepper motor control; the diffuser screen onto which images are projected and the detector. It is shown that the non-uniform pixel sensitivity of the low-cost CCD detector used and the granularity of the diffuser screen lead to a serious ring artefact in the reconstructed images. Methods are described for eliminating this. The problems arising from reflection and refraction at the walls of the gel container are explained. Optical ray-tracing simulations are presented for cylindrical containers with a variety of radii and verified experimentally. Small changes in the model parameters lead to large variations in the signal intensity observed in the projection data. The effect of imperfect containers on data quality is discussed and a method based on a 'correction scan' is shown to be successful in correcting many of the related image artefacts. The results of two tomography experiments are presented. In the first experiment, a radiochromic Fricke gel sample was exposed four times in different positions to a 100 kVp x-ray beam perpendicular to the plane of imaging. Images of absorbed dose with slice thickness of 140 microm were acquired. with 'true' in-plane resolution of 560 x 560 microm2 at the edge of the 72 mm field of view and correspondingly higher resolution at the centre. The nominal doses measured correlated well with the known exposure times. The second experiment demonstrated the well known phenomenon of diffusion in the dosemeter gels and yielded a value of (0.12 +/- 0.02) mm2 s(-1) for the diffusion coefficient of the xylenol orange/iron complex. Finally, the overall implications of the above findings for dosimetry using OCT are discussed.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Doran SJ,Koerkamp KK,Bero MA,Jenneson P,Morton EJ,Gilboy WBdoi
10.1088/0031-9155/46/12/309subject
Has Abstractpub_date
2001-12-01 00:00:00pages
3191-213issue
12eissn
0031-9155issn
1361-6560journal_volume
46pub_type
杂志文章abstract::Gold nanoparticle (GNP) radio-enhancement is a promising technique to increase the dose deposition in a tumor while sparing neighboring healthy tissue. Previous experimental studies showed effects on cell survival and tumor control for keV x-rays but surprisingly also for MV-photons, proton and carbon-ion beams. In a ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab314c
更新日期:2019-08-28 00:00:00
abstract::Diffraction-enhanced imaging (DEI) is a new x-ray imaging modality that has been shown to enhance contrast between normal and cancerous breast tissues. In this study, diffraction-enhanced imaging in computed tomography (DEI-CT) mode was used to quantitatively characterize the refraction contrasts of the organized stru...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/54/10/019
更新日期:2009-05-21 00:00:00
abstract::This study evaluates the performance of the Bruker positron emission tomograph (PET) insert combined with a BioSpec 70/30 USR magnetic resonance imaging (MRI) scanner using the manufacturer acceptance protocol and the NEMA NU 4-2008 for small animal PET. The PET insert is made of 3 rings of 8 monolithic LYSO crystals ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aba08c
更新日期:2020-06-26 00:00:00
abstract::A technique is described by which the regional distribution of bone mineral can be determined in bone samples from small animals. The technique employs an Anger camera interfaced to a medical computer. High resolution (less than 1 mm) imaging is possible by producing magnified images of the bone samples. Regional dens...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/29/1/003
更新日期:1984-01-01 00:00:00
abstract::An extensive study on specific absorption rate (SAR) covering 720 simulations and 15 voxel models (18-105 kg) has been performed by applying the parallel finite-difference time-domain method. High-resolution whole-body models have been irradiated with plane waves from 300 MHz to 5 GHz by applying various incoming dire...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/55/4/017
更新日期:2010-02-21 00:00:00
abstract::The purpose of this work is to provide an evaluation of the mean glandular dose (MGD) for breast computed tomography (CT) with synchrotron radiation in an axial scanning configuration with a partial or total organ volume irradiation, for the in vivo program of breast CT ongoing at the ELETTRA facility (Trieste, Italy)...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/2/569
更新日期:2016-01-21 00:00:00
abstract::Electromagnetic tracking technology is primarily used for continuous prostate localization during radiotherapy, but offers potential value for evaluation of dosimetric coverage and adequacy of treatment for dynamic targets. We developed a highly automated method for daily computation of cumulative dosimetric effects o...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/55/1/005
更新日期:2010-01-07 00:00:00
abstract::Computational phantoms are commonly used in internal radiation dosimetry to assess the amount and distribution pattern of energy deposited in various parts of the human body from different internal radiation sources. Radiation dose assessments are commonly performed on predetermined reference computational phantoms wh...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aa75b4
更新日期:2017-07-13 00:00:00
abstract::Time-of-flight (TOF) positron emission tomography (PET) technology has recently regained popularity in clinical PET studies for improving image quality and lesion detectability. Using TOF information, the spatial location of annihilation events is confined to a number of image voxels along each line of response, there...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/3/1309
更新日期:2016-02-07 00:00:00
abstract::Modern Monte Carlo codes allow for the calculation of ion chamber specific beam quality correction factors k(Q), which are needed for dosimetry in radiotherapy. While statistical (type A) uncertainties of the calculated data can be minimized sufficiently, the influence of systematic (type B) uncertainties is mostly un...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/55/16/S04
更新日期:2010-08-21 00:00:00
abstract::The dosimetrical characteristics of a new miniature multileaf collimator (ModuLeaf MLC, MRC Systems GmbH, Heidelberg, Germany) attached to the accessory holder of a Siemens accelerator with 6 MV x-rays (PRIMUS, Siemens OCS, Concord, California, USA) have been investigated. In particular, those parameters which are imp...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/47/12/402
更新日期:2002-06-21 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::Positron range impairs resolution in PET imaging, especially for high-energy emitters and for small-animal PET. De-blurring in image reconstruction is possible if the blurring distribution is known. Furthermore, the percentage of annihilation events within a given distance from the point of positron emission is releva...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/57/12/3931
更新日期:2012-06-21 00:00:00
abstract::The classical Sievert integral method is a valuable tool for dose rate calculations around brachytherapy sources, combining simplicity with reasonable computational times. However, its accuracy in predicting dose rate anisotropy around 192Ir brachytherapy sources has been repeatedly put into question. In this work, we...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/45/2/309
更新日期:2000-02-01 00:00:00
abstract::Electrical properties (EP), namely conductivity and permittivity, can provide endogenous contrast for tissue characterization. Using electrical property tomography (EPT), maps of EP can be generated from conventional MRI data. This report investigates the feasibility and accuracy of EPT at 21.1 T for multiple RF coils...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab3259
更新日期:2020-02-28 00:00:00
abstract::Sparse-view CT reconstruction algorithms via total variation (TV) optimize the data iteratively on the basis of a noise- and artifact-reducing model, resulting in significant radiation dose reduction while maintaining image quality. However, the piecewise constant assumption of TV minimization often leads to the appea...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/12/2997
更新日期:2014-06-21 00:00:00
abstract::The exponential edge-gradient effect must arise in any x-ray transmission CT scanner whenever long sharp edges of high contrast are encountered. The effect is non-linear and is due to the interaction of the exponential law of x-ray attenuation and the finite width of the scanning beam in the x-y plane. The error induc...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/26/3/010
更新日期:1981-05-01 00:00:00
abstract::In stereotactic radiosurgery, a seven-irradiation film was used to define any discrepancy between the beam and target centres. A mathematical model based on the linac alignment and target set-up was developed to diagnose the discrepancies of the seven-irradiation film between the beam and simulation target centres. Fr...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/41/9/003
更新日期:1996-09-01 00:00:00
abstract::Silicon photomultipliers (SiPMs) are widely used in positron emission tomography (PET), however, SiPMs from different vendors vary in their performance characteristics. In addition, the specifications provided by the manufacturers are measured under different operating conditions and using different test setups, makin...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab1c37
更新日期:2019-08-07 00:00:00
abstract::The peak CT number (CT) and full width at half maximum (FWHM) were obtained from the image profiles of aluminium of thickness ranging from 0.1-9.5 mm. The scans were performed at different fields of view (FOVs) and with different reconstruction algorithms ('bone' and 'standard'). Above 3 mm, CT and FWHM provide measur...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/43/3/013
更新日期:1998-03-01 00:00:00
abstract::Coronary flow rate remains complex to assess in clinical practice using non-invasive, non-ionizing imaging tools. In this study, we introduce 3D ultrafast Doppler coronary angiography (3D UDCA), an ultrasound-based method to assess coronary blood flows in three-dimensions at high volume-rate and in one single heartbea...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab8d78
更新日期:2020-06-05 00:00:00
abstract::In this study, the quantitative accuracy of different attenuation correction strategies presently available for the High Resolution Research Tomograph (HRRT) was investigated. These attenuation correction methods differ in reconstruction and processing (segmentation) algorithms used for generating a micro-image from m...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/53/1/007
更新日期:2008-01-07 00:00:00
abstract::A CT scanner has been constructed specifically to determine the three-dimensional distribution of bone mineral in the medullary cavities of the radius, ulna and femur. A source of x-rays (153Gd) and a multiwire proportional counter (MWPC) are mounted at opposite ends of a diameter of an annular mounting. The limb is p...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/32/10/002
更新日期:1987-10-01 00:00:00
abstract::A Monte Carlo computational model of a fluoroscopic imaging chain was used for deriving optimal technique factors for paediatric fluoroscopy. The optimal technique was defined as the one that minimizes the absorbed dose (or dose rate) in the patient with a constraint of constant image quality. Image quality was assess...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/44/2/018
更新日期:1999-02-01 00:00:00
abstract::In this work, a methodology for using a smartphone camera, in conjunction with a light-tight box operating in reflective transmission mode, is investigated as a proof of concept for use as a film dosimetry system. An imaging system was designed to allow the camera of a smartphone to be used as a pseudo densitometer. T...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aa8b36
更新日期:2017-10-03 00:00:00
abstract::Monte Carlo simulation of radiation transport is considered to be one of the most accurate methods of radiation therapy dose calculation. With the rapid development of computer technology, Monte Carlo based treatment planning for radiation therapy is becoming practical. A basic requirement for Monte Carlo treatment pl...
journal_title:Physics in medicine and biology
pub_type: 杂志文章,评审
doi:10.1088/0031-9155/44/12/201
更新日期:1999-12-01 00:00:00
abstract::Uncertainties in determining clinically used relative biological effectiveness (RBE) values for ion beam therapy carry the risk of absolute and relative misestimations of RBE-weighted doses for clinical scenarios. This study assesses the consequences of hypothetical misestimations of input parameters to the RBE modell...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/57/23/7983
更新日期:2012-12-07 00:00:00
abstract::Magnetoencephalography (MEG) source analysis has largely relied on spherical conductor models of the head to simplify forward calculations of the brain's magnetic field. Multiple- (or overlapping, local) sphere models, where an optimal sphere is selected for each sensor, are considered an improvement over single-spher...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/56/17/010
更新日期:2011-09-07 00:00:00
abstract::Micro-CT is widely used in preclinical studies, generating substantial interest in extending its capabilities in functional imaging applications such as blood perfusion and cardiac function. However, imaging cardiac structure and function in mice is challenging due to their small size and rapid heart rate. To overcome...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aa9b45
更新日期:2018-01-09 00:00:00
abstract::In order to optimize external-beam conformal radiotherapy, patient movement during treatment must be minimized. For treatment on the upper torso, the target organs are known to move substantially due to patient respiration. This paper deals with the technical aspects of gating the radiotherapy beam synchronously with ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/41/1/007
更新日期:1996-01-01 00:00:00