Abstract：
:Intensity modulated radiation therapy (IMRT) is used to deliver highly conformal radiation doses to tumors while sparing nearby sensitive tissues. Discrepancies between calculated and measured dose distributions have been reported for regions of high dose gradients corresponding to complex radiation fluence patterns. For the single pencil beam convolution dose calculation algorithm, the ability to resolve areas of high dose structure is partly related to the shape of the pencil beam dose kernel (similar to how a photon detector's point spread function relates to imaging resolution). Improvements in dose calculation accuracy have been reported when the treatment planning system (TPS) is recommissioned using high-resolution measurement data as input. This study proposes to improve the dose calculation accuracy for IMRT planning by modifying clinical dose kernel shapes already present in the TPS, thus avoiding the need to reacquire higher resolution commissioning data. The in-house optimization program minimizes a cost-function based on a two-dimensional composite dose subtraction/distance-to-agreement (gamma) analysis. The final modified kernel shapes are reintroduced into the treatment planning system and improvements to the dose calcula tion accuracy for complex IMRT dose distributions evaluated. The central kernel value (radius =0 cm) has the largest effect on the dose calculation resolution and is the focus of this study.
journal_name
Med Physjournal_title
Medical physicsauthors
Bergman AM,Otto K,Duzenli Cdoi
10.1118/1.1812851subject
Has Abstractpub_date
2004-12-01 00:00:00pages
3279-87issue
12eissn
0094-2405issn
2473-4209journal_volume
31pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：PURPOSE:To develop a method of using two-dimensional (2D) magnetic resonance thermometry, and three-dimensional (3D) Gaussian modeling to predict the volume, shape, and location of 1 day postoperative T1w high-intensity focused ultrasound lesions in medication refractory tremor patients; thereby facilitating a better c...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13868
更新日期：2019-12-01 00:00:00
abstract：:This study proposes an algorithm for selecting beam weight, wedge angle, and wedge orientation for three-dimensional radiation therapy treatment planning. According to dose gradient analysis, the necessary and sufficient condition for achieving a homogeneous dose over the target volume is that the total vector sum of ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1286591
更新日期：2000-08-01 00:00:00
abstract：:In a recent paper of Miller et al. (Med. Phys. 43(5), 2141-2152 (2016), the voltage dependence polarity effect of microionization chambers was studied. It was identified that polarity effect arises from the difference in electric potential between the collecting electrode and the guard electrode, which in turn deforms...
journal_title：Medical physics
pub_type： 信件
doi：10.1002/mp.12019
更新日期：2017-03-01 00:00:00
abstract：PURPOSE:Digital breast tomosynthesis (DBT) is becoming an important part of breast cancer screening and diagnosis. Compared to two-dimensional mammography, tomosynthesis introduces limited three-dimensional (3D) resolution, but maintains high in-plane resolution, low dose, and allows for similar clinical protocols. The...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13116
更新日期：2018-10-01 00:00:00
abstract：:Statistical image reconstruction (SIR) methods have shown potential to substantially improve the image quality of low-dose x-ray computed tomography (CT) as compared to the conventional filtered back-projection (FBP) method. According to the maximum a posteriori (MAP) estimation, the SIR methods are typically formulat...
journal_title：Medical physics
pub_type： 杂志文章,评审
doi：10.1002/mp.13123
更新日期：2018-10-01 00:00:00
abstract：PURPOSE:The use of 4D computed tomography (4D-CT) of the lung is important in lung cancer radiotherapy for tumor localization and treatment planning. Sometimes, dense sampling is not acquired along the superior-inferior direction. This disadvantage results in an interslice thickness that is much greater than in-plane v...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4899185
更新日期：2014-11-01 00:00:00
abstract：PURPOSE:To develop a deformable mapping technique to match corresponding lesions between digital breast tomosynthesis (DBT) and automated breast ultrasound (ABUS) images. METHODS:External fiducial markers were attached to the surface of two CIRS multi-modality compressible breast phantoms (A and B) containing multiple...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13113
更新日期：2018-10-01 00:00:00
abstract：:We designed a novel force/torque moment transducer with six degrees of freedom. This new sensor is used for measuring the forces and torque moments exerted by static magnetic resonance imaging (MRI) fields on various medical implants, instruments, and ballistic shell fragments. To determine the location of strongest e...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597853
更新日期：1996-06-01 00:00:00
abstract：:Projected light fields are used on treatment simulators and teletherapy treatment units to delineate the size and position of the radiation beam. Any discrepancy between these fields will lead to a systematic field placement error, with possibly serious implications with regard to the accuracy of the delivered dose di...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597867
更新日期：1996-07-01 00:00:00
abstract：PURPOSE:Photon counting arrays (PCAs), capable of measuring the spectral information of individual x-ray photons and recording that information digitally, provide a number of advantages compared to conventional, energy-integrating active matrix flat-panel imagers - such as reducing the undesirable effects of electronic...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13128
更新日期：2018-10-01 00:00:00
abstract：PURPOSE:To develop a fluoroscopy imaging based approach that can determine the magnitude and phase variation in respiratory motion against the treatment planning images in order to quantify the online patient setup deviation in thoracic cancer IGRT for the real time adaptive patient positionadjustment. METHODS:A numer...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734876
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:To Validate Brainlab-ExacTrac IGRT with Dot-Decimal electron compensator(BolusECT) for accurate patient positioning. METHODS:Dot-Decimal electron compensators(BolusECT) are used to achieve conformal dose distributions and greater sparing to normal structures for cases with varying patient contours and treated ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734881
更新日期：2012-06-01 00:00:00
abstract：:An electronic scanning-slit technology is under development which involves replacing paired fore and aft slits for scatter rejection with only one fore slit. As the slit scans across the portion of the patient to be imaged, pulsed x-ray exposures produce images of the slit in successive positions, which are digitized ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595940
更新日期：1986-03-01 00:00:00
abstract：PURPOSE:The purpose of this study was to investigate the potential of MR-guided pulsed focused ultrasound (pFUS) for the enhancement of drug uptake in prostate tumors in vivo using doxorubicin (Dox). METHODS:An antitumor drug Dox, an orthotopic animal prostate tumor model using human prostate cancer, LNCaP cell line, ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4705346
更新日期：2012-05-01 00:00:00
abstract：PURPOSE:The ability to monitor intrafractional tumor motion is essential for radiation therapy of thoracic and abdominal tumors. This study aims to develop a method to track lung tumor motion using intrafractional continuous ultrasound (US) and periodic cone-beam projection images (CBPI). METHODS:Time-sequenced b-mode...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13104
更新日期：2018-10-01 00:00:00
abstract：PURPOSE:To evaluate the image quality of virtual monochromatic images synthesized from dual-source dual-energy computed tomography (CT) in comparison with conventional polychromatic single-energy CT for the same radiation dose. METHODS:In dual-energy CT, besides the material-specific information, one may also synthesi...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3658568
更新日期：2011-12-01 00:00:00
abstract：:For diagnostic ultrasound imaging, as in computed tomography, a feature of prime importance is the detection of focal lesions of varying size and contrast (echo amplitude) from surrounding tissue. This study describes a new tissue-stimulating phantom which has been used to measure the threshold detection of varying co...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595218
更新日期：1982-01-01 00:00:00
abstract：PURPOSE:The most common material for shielding is concrete, which can be made using various materials of different densities as aggregates. New techniques in radiotherapy, as IMRT and VMAT, require more monitor units and it is important to develop specifically designed shielding materials. METHODS:Arraela S.L. has dev...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735331
更新日期：2012-06-01 00:00:00
abstract：:The optimum x-ray spectra for acquisition of digital mammographic images using an amorphous selenium (a-Se) photoconductor are investigated. The recorded images consist of latent charge distributions on the surface of an a-Se plate, which are then read out using two methods, laser discharge, or flat panel recharge. Th...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597688
更新日期：1996-04-01 00:00:00
abstract：PURPOSE:Cone-beam CT (CBCT) images contain severe shading artifacts mostly due to scatter. Many algorithms have been proposed to alleviate this problem by data correction on projections. Sophisticated methods have also been designed to further improve the image quality when prior patient information is available. In th...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4736218
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:In this study the Octavius detector 729 ionization chamber (IC) array with the Octavius 4D phantom was characterized for flattening filter (FF) and flattening filter free (FFF) static and rotational beams. The device was assessed for verification with FF and FFF RapidArc treatment plans. METHODS:The response o...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4817482
更新日期：2013-09-01 00:00:00
abstract：PURPOSE:To compare and evaluate intensity-based registration methods for computation of serial x-ray mammogram correspondence. METHODS:X-ray mammograms were simulated from MRIs of 20 women using finite element methods for modeling breast compressions and employing a MRI/x-ray appearance change model. The parameter con...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3457470
更新日期：2010-09-01 00:00:00
abstract：:The measurement of output factors for small fields is challenging and can lead to large dose errors in patient treatments if corrections for detector size and scatter from high-Z material are not applied. Due to its high spatial resolution and near tissue equivalence, GAFCHROMIC® film potentially provides a correction...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4740095
更新日期：2012-07-01 00:00:00
abstract：PURPOSE:In breast radiotherapy with intensity modulation, it is a well established practice to extend the dose fluence outside the limit of the body contour to account for small changes in size and position of the target and the rest of the tissues due to respiration or to possible oedema. A simple approach is not appl...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3598442
更新日期：2011-07-01 00:00:00
abstract：PURPOSE:Accurate detection of pulmonary nodules remains a technical challenge in computer-aided diagnosis systems because some nodules may adhere to the blood vessels or the lung wall, which have low contrast compared to the surrounding tissues. In this paper, the analysis of typical shape features of candidate nodules...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4907961
更新日期：2015-03-01 00:00:00
abstract：PURPOSE:To establish accurate experimental dosimetry techniques for reference dose measurements in nonstandard composite fields. METHODS:A cylindrical PMMA phantom filled with water was constructed, at the center of which reference absorbed dose to water for a head and neck IMRT delivery was measured. Based on the pro...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3392247
更新日期：2010-06-01 00:00:00
abstract：PURPOSE:The lateral edge of a proton therapy beam is commonly used to achieve conformality to the treatment volume where critical structures reside close to the target. However, when treating shallow depths, the lateral edge of a pencil beam scanning (PBS) system may be broader than that of a double scattered (DS) syst...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4941957
更新日期：2016-03-01 00:00:00
abstract：PURPOSE:Texture analysis (TA) has proved to be useful to distinguish different tissues and disease states using magnetic resonance imaging (MRI). TA has been successfully applied clinically to improve identification of abnormalities in the brain, liver, and bone and, more recently, has been used to enhance the specific...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3622605
更新日期：2011-09-01 00:00:00
abstract：:The use of dedicated magnetic resonance simulation (MR-SIM) platforms in Radiation Oncology has expanded rapidly, introducing new equipment and functionality with the overall goal of improving the accuracy of radiation treatment planning. However, this emerging technology presents a new set of challenges that need to ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14695
更新日期：2021-01-01 00:00:00
abstract：:Positron emission tomography (PET) is increasingly considered as an effective imaging method to support several stages of radiation therapy. The combined usage of functional and morphological imaging in state-of-the-art PET/CT scanners is rapidly emerging to support the treatment planning process in terms of improved ...
journal_title：Medical physics
pub_type： 杂志文章,评审
doi：10.1118/1.4935869
更新日期：2015-12-01 00:00:00
