Abstract：
:Silicon diodes have good spatial resolution, which makes them advantageous over ionization chambers for dosimetry in fields with high dose gradients. However, silicon diodes overrespond to low-energy photons, that are more abundant in scatter which increase with large fields and larger depths. We present a cavity-theory-based model for a general response function for silicon detectors at arbitrary positions within photon fields. The model uses photon and electron spectra calculated from fluence pencil kernels. The incident photons are treated according to their energy through a bipartition of the primary beam photon spectrum into low- and high-energy components. Primary electrons from the high-energy component are treated according to Spencer-Attix cavity theory. Low-energy primary photons together with all scattered photons are treated according to large cavity theory supplemented with an energy-dependent factor K(E) to compensate for energy variations in the electron equilibrium. The depth variation of the response for an unshielded silicon detector has been calculated for 5 x 5 cm(2), 10 x 10 cm(2) and 20 x 20 cm(2) fields in 6 and 15 MV beams and compared with measurements showing that our model calculates response factors with deviations less than 0.6%. An alternative method is also proposed, where we show that one can use a correlation with the scatter factor to determine the detector response of silicon diodes with an error of less than 3% in 6 MV and 15 MV photon beams.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Eklund K,Ahnesjö Adoi
10.1088/0031-9155/54/20/007subject
Has Abstractpub_date
2009-10-21 00:00:00pages
6135-50issue
20eissn
0031-9155issn
1361-6560pii
S0031-9155(09)21468-0journal_volume
54pub_type
杂志文章abstract：:To predict the temperature distribution during hyperthermia treatments a thermal model that accounts for the thermal effect of blood flow is mandatory. The DIscrete VAsculature (DIVA) thermal model developed at our department is able to do so; geometrically described vessels are handled individually and the remaining ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/45/3/314
更新日期：2000-03-01 00:00:00
abstract：:Breast cancer is one of the leading causes of female cancer deaths. Early diagnosis with prophylactic may improve the patients' prognosis. So far ultrasound (US) imaging is a popular method in breast cancer diagnosis. However, its accuracy is bounded to traditional handcrafted feature methods and expertise. A novel me...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/1361-6560/abc5c7
更新日期：2020-10-29 00:00:00
abstract：:In this study, we evaluate the feasibility of designing a beveled fiber-optic probe coupled with a ball lens for improving depth-resolved fluorescence measurements of epithelial tissue using Monte Carlo (MC) simulations. The results show that by using the probe configuration with a beveled tip collection fiber and a f...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/53/4/008
更新日期：2008-02-21 00:00:00
abstract：:This paper presents a method to experimentally validate the beam quality correction factors (kQ) tabulated in IAEA TRS-398 for proton beams and to determine the kQ of non-tabulated ionization chambers (based on the already tabulated values). The method is based exclusively on ionometry and it consists in comparing the...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/60/8/3207
更新日期：2015-04-21 00:00:00
abstract：:The measurement of output factors (OF) for the small photon beams generated by Leksell Gamma Knife® (LGK) radiotherapy units is a challenge for the physicist due to the under or over estimation of these factors by a vast majority of the detectors commercially available. Output correction factors, introduced in the int...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/60/10/3959
更新日期：2015-05-21 00:00:00
abstract：:A water calorimeter has been used for the direct measurement of absorbed dose to water in a d(15) + Be neutron beam. The absorbed dose measured with the calorimeter was compared with that measured with an Exradin ionisation chamber, constructed of A-150 plastic. The doses measured by the ionisation chamber were calcul...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/31/4/005
更新日期：1986-04-01 00:00:00
abstract：:A circular scanning trajectory is and will likely remain a popular choice of trajectory in computed tomography (CT) imaging because it is easy to implement and control. Filtered-backprojection (FBP)-based algorithms have been developed previously for approximate and exact reconstruction of the entire image or a region...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/49/18/011
更新日期：2004-09-21 00:00:00
abstract：:First experimental results with energy-resolved computed tomography (CT) are reported. The contrast-to-noise ratio (CNR) in CT has been improved with x-ray energy weighting for the first time. Further, x-ray energy weighting improved the CNR in material decomposition CT when applied to CT projections prior to dual-ene...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/53/20/002
更新日期：2008-10-21 00:00:00
abstract：:A post-processing noise suppression technique for biomedical MRI images is presented. The described procedure recovers both sharp edges and smooth surfaces from a given noisy MRI image; it does not blur the edges and does not introduce spikes or other artefacts. The fine details of the image are also preserved. The pr...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/48/13/310
更新日期：2003-07-07 00:00:00
abstract：:Computer aided detection (CADe) for breast lesion can provide an important reference for radiologists in breast cancer screening. Architectural distortion (AD) is a type of breast lesion that is difficult to detect. A majority of CADe methods focus on detecting the radial pattern, which is a main characteristic of typ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/1361-6560/ab98d0
更新日期：2020-06-02 00:00:00
abstract：:Average penetration depths and detour factors of 1-50 MeV electrons in water and plastic materials have been computed by means of analytical calculation, within the continuous-slowing-down approximation and including multiple scattering, and using the Monte Carlo codes ITS and PENELOPE. Results are compared to detour ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/41/7/004
更新日期：1996-07-01 00:00:00
abstract：:This is a review of the relatively recently developed field of intravascular brachytherapy of coronary arteries. It presents a brief overview of the discipline of coronary angioplasty describing the problem of restenosis and discusses the potential for ionizing radiation to overcome this problem. It examines the vario...
journal_title：Physics in medicine and biology
pub_type： 杂志文章,评审
doi：10.1088/0031-9155/47/4/201
更新日期：2002-02-21 00:00:00
abstract：:We present a comparison of simulated low-frequency electromagnetic fields in the human body, calculated by means of the electro-quasistatic formulation. The geometrical data in these simulations were provided by an anatomically realistic, high-resolution human body model, while the dielectric properties of the various...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/50/19/N02
更新日期：2005-10-07 00:00:00
abstract：:Monte Carlo (MC) simulations are often at the heart of the testing procedure in biomedical optics. One of the critical points in MC simulations is to define the new photon direction after each scattering event. One of the most popular solutions is to use the Henyey-Greenstein phase function or some linear combinations...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/51/17/N04
更新日期：2006-09-07 00:00:00
abstract：:Corrections for room scatter, [ksc(d, H)]RM, were derived using Monte Carlo methods for rooms of various sizes, including the brachytherapy treatment room, in which primary air kerma strength standardization of a remote afterloading microSelectron 192Ir HDR source was carried out, using a 60 cm3 spherical graphite ion...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/46/9/303
更新日期：2001-09-01 00:00:00
abstract：:In this paper, we present a new algorithm as an enhancement and preprocessing step for acquired optical coherence tomography (OCT) images of the retina. The proposed method is composed of two steps, first of which is a denoising algorithm with wavelet diffusion based on a circular symmetric Laplacian model, and the se...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/58/9/2925
更新日期：2013-05-07 00:00:00
abstract：:A method to measure the detector-to-object distance from the images obtained with stationary high-spatial-resolution gamma-ray cameras for in vivo studies has been developed. It exploits the shift of the imaged object in the image plane, obtained at a certain tilt of the parallel-hole collimator. A linear dependence o...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/51/9/N04
更新日期：2006-05-07 00:00:00
abstract：:The concepts of radiance and fluence are fundamental to the description of a radiation field. The International Commission on Radiological Units and Measurements (ICRU) has defined fluence in terms of the number of the radiation particles crossing a small sampling sphere. A second definition has been proposed in which...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/39/6/011
更新日期：1994-06-01 00:00:00
abstract：:Tumor motion is a particular concern for a complex treatment modality such as helical tomotherapy, where couch position, gantry rotation and MLC leaf opening all change with time. In the present study, we have investigated the impact of tumor motion for helical tomotherapy, which could result in three distinct motion-...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/54/19/004
更新日期：2009-10-07 00:00:00
abstract：:This study aims to develop a computer-aided diagnosis (CADx) scheme for classification between malignant and benign lung nodules, and also assess whether CADx performance changes in detecting nodules associated with early and advanced stage lung cancer. The study involves 243 biopsy-confirmed pulmonary nodules. Among ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/1361-6560/aaa610
更新日期：2018-02-05 00:00:00
abstract：:The dosimetric measurement and modeling of small radiation treatment fields (<2 × 2 cm2) are difficult to perform and prone to error. Measurements of small fields are often adversely influenced by the properties of the detectors used to make them. The dosimetric properties of small fields have been difficult to accura...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/56/12/015
更新日期：2011-06-21 00:00:00
abstract：:Segmentation of liver in abdominal computed tomography (CT) is an important step for radiation therapy planning of hepatocellular carcinoma. Practically, a fully automatic segmentation of liver remains challenging because of low soft tissue contrast between liver and its surrounding organs, and its highly deformable s...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/1361-6560/aabd19
更新日期：2018-05-04 00:00:00
abstract：:Focused ultrasound (FUS) phased arrays show promise for non-invasive brain therapy. However, the majority of them are limited to a single transmit/receive frequency and therefore lack the versatility to expose and monitor the treatment volume. Multi-frequency arrays could offer variable transmit focal sizes under a fi...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/61/24/8476
更新日期：2016-12-21 00:00:00
abstract：:A dedicated small-animal x-ray micro computed tomography (micro-CT) system has been developed to screen laboratory small animals such as mice and rats. The micro-CT system consists of an indirect-detection flat-panel x-ray detector with a field-of-view of 120 x 120 mm2, a microfocus x-ray source, a rotational subject ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/48/24/014
更新日期：2003-12-21 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：:An x-ray fluorescence system with a synchrotron radiation source was used to quantify the levels of iron, copper and zinc in breast tissue specimens. Healthy tissue and breast carcinomas were investigated as an aid to understanding the mechanisms of breast cancer and as a possible complementary diagnostic tool. Eighty...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/47/13/310
更新日期：2002-07-07 00:00:00
abstract：:An analytical approximation for the scatter to primary dose ratio (SPR) on the central axis was validated against Monte Carlo results and experimental measurements for homogeneous and inhomogeneous phantoms. The analytical approximation only included first-order Compton scatter. The contribution to the total SPR from ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/46/6/310
更新日期：2001-06-01 00:00:00
abstract：:EGSnrc Monte Carlo simulation was used to investigate dose perturbation effects in prostate seed implant brachytherapy using 125I radioactive seeds used in implant brachytherapy. Dose perturbation effects resulting from the seed mutual attenuation in a prostate seed implant consisting of 27 seeds were investigated. Th...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/49/14/011
更新日期：2004-07-21 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：:Temporal regularization plays a critical role in cardiac gated dynamic SPECT reconstruction, of which the goal is to obtain an image sequence from a single acquisition which simultaneously shows both cardiac motion and tracer distribution change over the course of imaging (termed 5D). In our recent work, we explored t...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/57/17/5523
更新日期：2012-09-07 00:00:00
