Calculation of photon dose distributions in an inhomogeneous medium using convolutions.

abstract：:A computed tomography (CT) based system that compensates for patient surface contour and internal tissue inhomogeneity was implemented in our clinic. The compensators are fabricated with a mixture of tin granules and bee's wax. The tin/wax mixture was optimized for tin granule size and tin granule to wax ratio. The na...

journal_title：Medical physics

authors： Jursinic PA,Podgorsak MB,Paliwal BR

更新日期：1994-03-01 00:00:00

abstract：:Electron energy spectra and angular distributions, including angular spreads, were measured using magnetic spectrometer techniques, at isocenter, for two clinical linear accelerators: one scanning beam machine, which achieves field flatness by scanning a pencil beam over the desired field at the patient plane, and one...

journal_title：Medical physics

authors： Deasy JO,Almond PR,McEllistrem MT

更新日期：1996-05-01 00:00:00

abstract：PURPOSE:To investigate the use of local noise power spectrum (NPS) to characterize image noise and wavelet analysis to isolate defective pixels and inter-subpanel flat-fielding artifacts for quantitative quality assurance (QA) of electronic portal imaging devices (EPIDs). METHODS:A total of 93 image sets including cus...

journal_title：Medical physics

authors： Lee S,Yan G,Bassett P,Gopal A,Samant S

更新日期：2016-09-01 00:00:00

abstract：:Treatment of cervical cancer often involves intracavitary high dose rate (HDR) brachytherapy. Dose delivered to the bladder and rectum are typically estimated using the ICRU reference points. Dose to the sigmoid and small bowel are not estimated, yet these organs typically exhibit significant complication rates. The o...

journal_title：Medical physics

authors： Lekx-Toniolo KS,Hunter R,Patel M,Voruganti S,Johanson C,Dhamanaskar K,Farrell T

更新日期：2008-07-01 00:00:00

abstract：PURPOSE:Stereotactic ablative body radiotherapy (SABR) for lung patients can be performed with volumetric-modulated arc therapy (VMAT) plans using off-axis target geometry to allow treatment in their CBCT verified position. For patient-specific quality assurance measurements using the PTW Octavius 4D phantom (PTW, Frei...

journal_title：Medical physics

authors： Jeevanandam P,Agnew CE,Irvine DM,McGarry CK

更新日期：2018-04-01 00:00:00

abstract：:The scattered-photon part of pencil-beam dose kernels for high-energy x-ray beams can be derived experimentally by differentiating the broad-beam scatter-to-primary dose ratio as a function of radius. Formally, this requires a uniform and parallel beam, and the procedure is complicated by the nonideal, actual beam con...

journal_title：Medical physics

authors： Ceberg CP,Bjärngard BE

更新日期：1996-09-01 00:00:00

abstract：:Due to practical limitations such as inter- and intraleaf transmission, nondivergent leaf end design, and leaf scatter, multileaf collimators (MLCs) are unable to accurately produce the ideal fluence patterns generated by inverse planning systems. Consequently, low dose regions receive substantially more radiation tha...

journal_title：Medical physics

authors： Popple RA,Fiveash JB,Brezovich IA

更新日期：2007-10-01 00:00:00

abstract：:The Gafchromic EBT was recently introduced in film dosimetry for external beam therapy (EBT). The high spatial resolution, weak energy dependence, and near-tissue equivalence of EBT films make them suitable for measurement of dose distributions in radiotherapy, especially intensity-modulated radiation therapy (IMRT). ...

journal_title：Medical physics

authors： Fiandra C,Ricardi U,Ragona R,Anglesio S,Giglioli FR,Calamia E,Lucio F

更新日期：2006-11-01 00:00:00

abstract：PURPOSE:The purpose of this study was to quantitatively characterize the fundamental aspects of image quality (IQ) associated with different computed tomography (CT) reconstruction algorithms, the resolution, noise texture, noise magnitude per dose, and use those data to devise a methodology to match IQ between differe...

journal_title：Medical physics

authors： Winslow J,Zhang Y,Samei E

更新日期：2017-11-01 00:00:00

abstract：:A fast method of seed matching and reconstruction in prostate brachytherapy is proposed. Previous approaches have required all seeds to be matched with all other seeds in other projections. The fast cross-projection algorithm for the reconstruction of seeds (Fast-CARS) allows for matching of a given seed with a subset...

journal_title：Medical physics

authors： Narayanan S,Cho PS,Marks RJ 2nd

更新日期：2002-07-01 00:00:00

abstract：PURPOSE:A dynamic bowtie filter can modulate flux along both fan and view angles for reduced patient dose, scatter, and required photon flux, which is especially important for photon counting detectors (PCDs). Among the proposed dynamic bowtie designs, the piecewise-linear attenuator (Hsieh and Pelc, Med Phys. 2013;40:...

journal_title：Medical physics

authors： Shunhavanich P,Hsieh SS,Pelc NJ

更新日期：2019-01-01 00:00:00

abstract：:The widespread application of positron emission tomography (PET) in clinical oncology has driven this imaging technology into a number of new research and clinical arenas. Increasing numbers of patient scans have led to an urgent need for efficient data handling and the development of new image analysis techniques to ...

journal_title：Medical physics

authors： Montgomery DW,Amira A,Zaidi H

更新日期：2007-02-01 00:00:00

abstract：:Calibration of an imported strontium-90 ophthalmic applicator at the U.S. National Bureau of Standards (now the National Institute of Standards and Technology) has disclose a significant discrepancy in dose rate calibration (32%-35%) with that quoted by the manufacturer. The University of Wisconsin has investigated th...

journal_title：Medical physics

authors： Goetsch SJ,Sunderland KS

更新日期：1991-03-01 00:00:00

abstract：PURPOSE:In this study, the authors validated a novel respiratory tracking device, the multidimensional respiratory tracking (MDRT) system, that was designed to assist in correcting for respiratory motion in PET/CT images. The authors also investigated a novel PET acquisition technique, smart gating (SG), that enables t...

journal_title：Medical physics

authors： Nehmeh SA,Haj-Ali AA,Qing C,Stearns C,Kalaigian H,Kohlmyer S,Schoder H,Ho AY,Larson SM,Humm JL

更新日期：2011-01-01 00:00:00

abstract：:Many new models of 125I seeds are being introduced, mainly due to the increase in prostate seed implants. We have evaluated the SourceTech Medical (STM), model STM1251, 125I seed using thermoluminescent dosimeters (TLDs) in a solid water phantom. TLD cubes, LiF TLD-100, with dimension 1 mm on each edge, were irradiate...

journal_title：Medical physics

authors： Chiu-Tsao ST,Duckworth TL,Hsiung CY,Li Z,Williamson J,Patel NS,Harrison LB

更新日期：2003-07-01 00:00:00

abstract：PURPOSE:Automated detection of solitary pulmonary nodules using positron emission tomography (PET) and computed tomography (CT) images shows good sensitivity; however, it is difficult to detect nodules in contact with normal organs, and additional efforts are needed so that the number of false positives (FPs) can be fu...

journal_title：Medical physics

authors： Teramoto A,Fujita H,Yamamuro O,Tamaki T

更新日期：2016-06-01 00:00:00

abstract：:(Received 22 October 2001; accepted for publication 26 March 2002; published 22 May 2002) With advanced conformal radiotherapy using intensity modulated beams, it is important to have radiation dose verification measurements prior to treatment. Metal oxide semiconductor field effect transistors (MOSFET) have the advan...

journal_title：Medical physics

authors： Chuang CF,Verhey LJ,Xia P

更新日期：2002-06-01 00:00:00

abstract：:Consensus has been developing over the past few decades on a number of measurements required for the laboratory assessment of medical imaging modalities. Nevertheless, understanding of the connection between these measurements and human observer performance in a broad range of tasks remains far from complete. Focusing...

journal_title：Medical physics

authors： Metz CE,Wagner RF,Doi K,Brown DG,Nishikawa RM,Myers KJ

更新日期：1995-07-01 00:00:00

abstract：:A 4-W, laser-based system for the positional readout of thermoluminescent (TL) plates was utilized to obtain dose profiles for a 60Co radiotherapy beam. Experimentally obtained glow curves for LiF resulting from the rapid heating rates characteristic of laser heating agreed well with results predicted using a first-or...

journal_title：Medical physics

authors： Kearfott KJ,Grupen-Shemansky ME

更新日期：1990-05-01 00:00:00

abstract：PURPOSE:To design volume-specific breast phantoms from breast CT (bCT) data sets and estimate the associated normalized mean glandular dose coefficients for breast CT using Monte Carlo methods. METHODS:A large cohort of bCT data sets (N = 215) was used to evaluate breast volume into quintiles (plus the top 5%). The av...

journal_title：Medical physics

authors： Hernandez AM,Boone JM

更新日期：2017-10-01 00:00:00

abstract：PURPOSE:To determine the accuracy and test-retest repeatability of fast radiofrequency (RF) transmit measurement approaches used in Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCE-MRI). Spatial variation in the transmitted RF field introduces bias and increased variance in quantitative DCE-MRI metrics includi...

journal_title：Medical physics

authors： Bliesener Y,Zhong X,Guo Y,Boss M,Bosca R,Laue H,Chung C,Sung K,Nayak KS

更新日期：2019-06-01 00:00:00

abstract：PURPOSE:Elastography using computer tomography (CT) is a promising methodology that can provide patient-specific regional distributions of lung biomechanical properties. The purpose of this paper is to investigate the feasibility of performing elastography using simulated lower dose CT scans. METHODS:A cohort of eight...

journal_title：Medical physics

authors： Hasse K,Hsieh SS,O'Connell D,Stiehl B,Min Y,Neylon J,Low DA,Santhanam AP

更新日期：2020-08-01 00:00:00

abstract：PURPOSE:Positron emission tomography (PET) is considered the gold standard for measuring myocardial blood flow in vivo but it is known that respiratory motion can lead to misalignment of the PET and computed tomography (CT) data sets and introduce artifacts in the CT-based attenuation correction (AC) of images. In addi...

journal_title：Medical physics

authors： Pourmoghaddas A,Klein R,deKemp RA,Wells RG

更新日期：2013-02-01 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

authors： Fahrig R,Rowlands JA,Yaffe MJ

更新日期：1996-04-01 00:00:00

abstract：:Charge coupled devices (CCDs) are being increasingly used in radiation therapy for dosimetric purposes. However, CCDs are sensitive to stray radiation. This effect induces transient noise. Radiation-induced noise strongly alters the image and therefore limits its quantitative analysis. The purpose of this work is to c...

journal_title：Medical physics

authors： Archambault L,Briere TM,Beddar S

更新日期：2008-10-01 00:00:00

abstract：:Volumetric modulated arc therapy (VMAT) has recently been used to improve the dose distribution and efficiency of treatment delivery over the standard intensity-modulated radiotherapy (IMRT) technique. This study compares the dosimetry between RapidArc plan and standard IMRT plan for head and neck cancer. Three head a...

journal_title：Medical physics

authors： Jiang R,Fleck A,Schaly B,Charland P,Zhan L,Alliet K,Rachakonda R,Osei E

更新日期：2012-07-01 00:00:00

abstract：PURPOSE:High-quality radiation therapy using highly conformal dose distributions and image-guided techniques requires optimum machine delivery performance. In this work, a monitoring system for multileaf collimator (MLC) performance, integrating semiautomated MLC quality control (QC) tests and statistical process contr...

journal_title：Medical physics

authors： Létourneau D,Wang A,Amin MN,Pearce J,McNiven A,Keller H,Norrlinger B,Jaffray DA

更新日期：2014-12-01 00:00:00

abstract：PURPOSE:This study aimed to introduce heat map, a graphical data presentation method widely used in gene expression experiments, to the presentation and interpretation of image fidelity assessment data of compressed computed tomography (CT) images. METHODS:The authors used actual assessment data that consisted of five...

journal_title：Medical physics

authors： Lee H,Kim B,Kim KJ,Seo J,Park S,Shin YG,Lee KH

更新日期：2011-08-01 00:00:00

abstract：PURPOSE:The authors had previously published measurements of the detectability of disk-shaped contrast objects in images obtained from a C-arm CT system. A simple approach based on Rose's criterion was used to scale the date, assuming the threshold for the smallest diameter detected should be inversely proportional to ...

journal_title：Medical physics

authors： Ganguly A,Yoon S,Fahrig R

更新日期：2010-05-01 00:00:00

abstract：:A spread-out Bragg peak (SOBP) is used in proton beam therapy to create a longitudinal conformality of the required dose to the target. In order to create this effect in a passive beam scattering system, a variety of components must operate in conjunction to produce the desired beam parameters. We will describe how th...

journal_title：Medical physics

authors： Lu HM,Brett R,Engelsman M,Slopsema R,Kooy H,Flanz J

更新日期：2007-10-01 00:00:00