MO-F-213AB-01: Improving Dose Uniformity in Patch-Field Proton Therapy Using Beam Current Modulation.

abstract：PURPOSE:Computed tomography (CT) and, in particular, cone beam CT (CBCT) have been increasingly used as a diagnostic tool in recent years. Patient motion during acquisition is common in CBCT due to long scan times. This results in degraded image quality and may potentially increase the number of retakes. Our aim was to...

journal_title：Medical physics

authors： Niebler S,Schömer E,Tjaden H,Schwanecke U,Schulze R

更新日期：2019-10-01 00:00:00

abstract：:The purpose of this study was to investigate if interfraction and intrafraction motion in free-breathing and gated lung IMRT can lead to systematic dose differences between 3DCT and 4DCT. Dosimetric effects were studied considering the breathing pattern of three patients monitored during the course of their treatment ...

journal_title：Medical physics

authors： Seco J,Sharp GC,Wu Z,Gierga D,Buettner F,Paganetti H

更新日期：2008-01-01 00:00:00

abstract：PURPOSE:The cardiovascular system (CVS) regulation can be studied from a central viewpoint, through heart rate variability (HRV) data, and from a peripheral viewpoint, through laser Doppler flowmetry (LDF) signals. Both the central and peripheral CVSs are regulated by several interacting mechanisms, each having its own...

journal_title：Medical physics

authors： Humeau A,Buard B,Mahé G,Rousseau D,Chapeau-Blondeau F,Abraham P

更新日期：2010-12-01 00:00:00

abstract：:Current methods for imaging joint motion are limited to either two-dimensional (2D) video fluoroscopy, or to animated motions from a series of static three-dimensional (3D) images. 3D movement patterns can be detected from biplane fluoroscopy images matched with computed tomography images. This involves several x-ray ...

journal_title：Medical physics

authors： Carelsen B,Bakker NH,Strackee SD,Boon SN,Maas M,Sabczynski J,Grimbergen CA,Streekstra GJ

更新日期：2005-09-01 00:00:00

abstract：PURPOSE:Imaging the knee under realistic load-bearing conditions can be carried out in a horizontal plane using a C-arm CT scanner. Human subjects can be scanned in a standing position and acquired data successfully reconstructed. However, reconstructing this data is a challenge due to significant artifacts that are in...

journal_title：Medical physics

authors： Choi JH,Keil A,Maier A,Pal S,McWalter EJ,Fahrig R

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:Currently applied calibration approaches lead to satisfying 3D roadmapping overlay and 3D reconstruction accuracies; however, the required calibration times are extensive. The aim of this paper is the introduction of a novel model-based approach for geometric system calibrations, leading to a significant reduct...

journal_title：Medical physics

authors： van der Maas R,de Jager B,Steinbuch M,Dries J

更新日期：2015-11-01 00:00:00

abstract：PURPOSE:To validate a delivery quality assurance (DQA) protocol for tomotherapy based on the measurement of the leaf open times (LOTs). In addition, to show the correlation between the mean relative LOT discrepancy and the dose deviation in the planning target volume (PTV). MATERIALS AND METHODS:We used a LOT measurem...

journal_title：Medical physics

authors： Schopfer M,Bochud FO,Bourhis J,Moeckli R

更新日期：2020-09-01 00:00:00

abstract：PURPOSE:A 3-year project called LABSYNC has been recently funded by the European Commission, with the aim of designing a radiation facility based on a compact light source, i.e., a laboratory-sized commercial synchrotron, capable of accelerating electrons up to 6 or 20 MeV. An accurate spectral description of hard x ra...

journal_title：Medical physics

authors： Marziani M,Taibi A,Di Domenico G,Gambaccini M

更新日期：2009-10-01 00:00:00

abstract：:Recent work has shown that there is significant uncertainty in measuring build-up doses in mega-voltage photon beams especially at high energies. In this present investigation we used a phantom-embedded extrapolation chamber (PEEC) made of Solid Water to validate Monte Carlo (MC)-calculated doses in the dose build-up ...

journal_title：Medical physics

authors： Abdel-Rahman W,Seuntjens JP,Verhaegen F,Deblois F,Podgorsak EB

更新日期：2005-01-01 00:00:00

abstract：:The relative sensitivity of the half-value layer (HVL) method as a quality index for megavoltage x-ray beams is examined by theoretical calculation and experimental measurements for 4-, 6-, 10-, and 25-MV x-ray beams. It is shown that lower atomic number materials are more sensitive to beam quality changes than higher...

journal_title：Medical physics

authors： Meli JA,Nath R

更新日期：1985-01-01 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：:Over the past decade, computed tomography (CT) theory, techniques and applications have undergone a rapid development. Since CT is so practical and useful, undoubtedly CT technology will continue advancing biomedical and non-biomedical applications. In this outlook article, we share our opinions on the research and de...

journal_title：Medical physics

authors： Wang G,Yu H,De Man B

更新日期：2008-03-01 00:00:00

abstract：:Performance characteristics sufficient to provide physical data base specific to the Siemen's Stabilipan 2 orthovoltage x-ray therapy machine are presented. Operating conditions covering the working range of the unit from 100 to 300 kVp are selected. Beam quality, output, the central axis depth dose, relative output f...

journal_title：Medical physics

authors： Niroomand-Rad A,Gillin MT,Lopez F,Grimm DF

更新日期：1987-09-01 00:00:00

abstract：PURPOSE:To automatically and efficiently segment the lesion area of the colonoscopy polyp image, a polyp segmentation method has been presented. METHODS:An ensemble model of pretrained convolutional neural networks was proposed, using Unet-VGG, SegNet-VGG, and PSPNet. Firstly, the Unet-VGG is obtained by the first 10 ...

journal_title：Medical physics

authors： Guo X,Zhang N,Guo J,Zhang H,Hao Y,Hang J

更新日期：2019-12-01 00:00:00

abstract：:Direct comparisons of the National Institute of Standards and Technology's (NIST) Ritz 20 kV to 100 kV standard free-air ionization chamber and a portable variable-length free-air ionization chamber designed by the University of Wisconsin-Madison Accredited Dosimetry Calibration Laboratory (UW-ADCL) were made on NISTs...

journal_title：Medical physics

authors： Coletti JG,Pearson DW,DeWerd LA,O'Brien CM,Lamperti PJ

更新日期：1997-08-01 00:00:00

abstract：:Nuclear magnetic resonance (NMR) imaging of perfluorocarbon (PFC) emulsions and neat liquids has shown potential for in vivo oxygen imaging in blood and organ tissue. PFC compounds exhibit complicated NMR spectra caused by chemical shifts and spin-spin couplings which can lead to artifacts and degraded spatial resolut...

journal_title：Medical physics

authors： Busse LJ,Thomas SR,Pratt RG,Clark LC Jr,Ackerman JL,Samaratunga RC,Hoffmann RE

更新日期：1986-07-01 00:00:00

abstract：:A comparison of two methods of scatter compensation in single photon emission computed tomography (SPECT) imaging is made on the basis of improvements in quantification. The methods, scatter-window subtraction and constrained deconvolution of an average point source response function (PSRF), are described; the theoret...

journal_title：Medical physics

authors： Yanch JC,Flower MA,Webb S

更新日期：1990-11-01 00:00:00

abstract：:Machine outputs, peak scatter factors, and central axis percentage depth dose distributions were measured for various phantom sizes in large radiation fields produced at extended distances by cobalt, 6-MV, and 10-MV photon beams. The results can be applied to practical total body irradiation procedures which usually i...

journal_title：Medical physics

authors： Podgorsak EB,Pla C,Evans MD,Pla M

更新日期：1985-09-01 00:00:00

abstract：:Amorphous selenium (a-Se) based real-time flat-panel imagers (FPIs) are finding their way into the digital radiology department because they offer the practical advantages of digital x-ray imaging combined with an image quality that equals or outperforms that of conventional systems. The temporal imaging characteristi...

journal_title：Medical physics

authors： Rau AW,Bakueva L,Rowlands JA

更新日期：2005-10-01 00:00:00

abstract：:Current MRI nonuniformity correction techniques are reviewed and investigated. Many approaches are used to remedy this artifact, but it is not clear which method is the most appropriate in a given situation, as the applications have been with different MRI coils and different clinical applications. In this work four w...

journal_title：Medical physics

authors： Velthuizen RP,Heine JJ,Cantor AB,Lin H,Fletcher LM,Clarke LP

更新日期：1998-09-01 00:00:00

abstract：PURPOSE:The need for four-dimensional (4D) treatment planning becomes indispensable when it comes to radiation therapy for moving tumors in the thoracic and abdominal regions. The primary purpose of this study is to combine the actual breathing trace during each individual treatment fraction with the Linac's log file i...

journal_title：Medical physics

authors： Freislederer P,von Münchow A,Kamp F,Heinz C,Gerum S,Corradini S,Söhn M,Reiner M,Roeder F,Floca R,Alber M,Belka C,Parodi K

更新日期：2019-07-01 00:00:00

abstract：:The objective is to understand the differences in the lesion formation processes between microwave and high-intensity focused ultrasound (HIFU) ablation. The lesions formed by microwaves and HIFU were real-time monitored and compared using transparent tissue-mimicking phantoms at 60 and 70 W of driving electrical powe...

journal_title：Medical physics

authors： Chen WS,Wu CC,Fang HY,Liu HL

更新日期：2006-05-01 00:00:00

abstract：:Three Monte Carlo photon/electron transport codes (GEPTS, EGSnrc, and MCNP) are bench-marked against dose measurements in homogeneous (both low- and high-Z) media as well as at interfaces. A brief overview on physical models used by each code for photon and electron (positron) transport is given. Absolute calorimetric...

journal_title：Medical physics

authors： Chibani O,Li XA

更新日期：2002-05-01 00:00:00

abstract：:The trend toward conformal techniques in stereotactic radiosurgery necessitates an accurate and practical method for verification of irregular three-dimensional dose distributions. This work presents the design and evaluation of a phantom system facilitating the measurement of conformal dose distributions using one or...

journal_title：Medical physics

authors： Robar JL,Clark BG

更新日期：2000-05-01 00:00:00

abstract：:An in vitro radiographic technique which uses saline/iodine displacement has been developed to study the thickness of bone-equivalent and soft-tissue-equivalent materials within atherosclerotic plaques in arterial specimens which have been cut open longitudinally and laid flat. Results concerning the optimization of t...

journal_title：Medical physics

authors： Moreau M,Holdsworth DW,Fenster A

更新日期：1997-01-01 00:00:00

abstract：:Accurate targeting is important in intensity-modulated radiation therapy (IMRT). The positional uncertainties of structures with respect to the external beams arise in part from random organ motion and patient setup errors. While it is important to improve immobilization and reduce the influence of organ motion, the r...

journal_title：Medical physics

authors： Li JG,Xing L

更新日期：2000-07-01 00:00:00

abstract：PURPOSE:To add mathematical rigor to the merging phase of the recently published two-stage VMAT optimization method called VMERGE. Using an exact merging method, we are able to better characterize the tradeoff between delivery efficiency and dose quality. METHODS:VMERGE begins with an IMRT plan that uses 180 equi-spac...

journal_title：Medical physics

authors： Salari E,Craft D

更新日期：2012-06-01 00:00:00

abstract：:The purpose of this study was to implement the Monte Carlo method for clinical radiotherapy dose calculations. We used the EGS4/BEAM code to obtain the phase-space data for 6-20 MeV electron beams and 4, 6, and 15 MV photon beams for Varian Clinac 1800, 2100C, and 2300CD accelerators. A multiple-source model was used ...

journal_title：Medical physics

authors： Ma CM,Mok E,Kapur A,Pawlicki T,Findley D,Brain S,Forster K,Boyer AL

更新日期：1999-10-01 00:00:00

abstract：PURPOSE:Different approaches have been used in dynamic elastography to assess mechanical properties of biological tissues. Most techniques are based on a simple inversion based on the measurement of the shear wave speed to assess elasticity, whereas some recent strategies use more elaborated analytical or finite elemen...

journal_title：Medical physics

authors： Ouared A,Kazemirad S,Montagnon E,Cloutier G

更新日期：2016-04-01 00:00:00

abstract：PURPOSE:X-ray microbeam radiation therapy is a preclinical concept for tumor treatment promising tissue sparing and enhanced tumor control. With its spatially separated, periodic micrometer-sized pattern, this method requires a high dose rate and a collimated beam typically available at large synchrotron radiation faci...

journal_title：Medical physics

authors： Burger K,Urban T,Dombrowsky AC,Dierolf M,Günther B,Bartzsch S,Achterhold K,Combs SE,Schmid TE,Wilkens JJ,Pfeiffer F

更新日期：2020-10-01 00:00:00