Ultrafast treatment plan optimization for volumetric modulated arc therapy (VMAT).

abstract：PURPOSE:In Stereotactic body radiation therapy (SBRT) higher dose per fraction is delivered to patients and thus the need for an accurate dose computation is further elevated. However under such conditions of small field geometries, the electronic equilibrium can be lost, making it challenging for the dose-calculation ...

journal_title：Medical physics

authors： Shosha M,Deiab N,Eldib A,Tohamy K

更新日期：2012-06-01 00:00:00

abstract：:An important aspect of the intensity modulated radiotherapy (IMRT) process is that of optimizing the beam intensity profiles. Most such methods use a comparison between the defined dose distribution (including prescription dose and dose limits for critical structures) and the current distribution. The comparison may i...

journal_title：Medical physics

authors： Jones L,Hoban P

更新日期：2002-01-01 00:00:00

abstract：:This paper deals with methods of reducing the total time required to acquire the projection data for a set of contiguous computed tomography (CT) images. Normally during the acquisition of a set of slices, the patient is held stationary during data collection and translated to the next axial location during an intersc...

journal_title：Medical physics

authors： Crawford CR,King KF

更新日期：1990-11-01 00:00:00

abstract：PURPOSE:The quantification of vessel wall morphology and plaque burden requires vessel segmentation, which is generally performed by manual delineations. The purpose of our work is to develop and evaluate a new 3D model-based approach for carotid artery wall segmentation from dual-sequence MRI. METHODS:The proposed me...

journal_title：Medical physics

authors： Gao S,van 't Klooster R,Kitslaar PH,Coolen BF,van den Berg AM,Smits LP,Shahzad R,Shamonin DP,de Koning PJH,Nederveen AJ,van der Geest RJ

更新日期：2017-10-01 00:00:00

abstract：PURPOSE:Respiratory gating in PET is an approach used to minimize the negative effects of respiratory motion on spatial resolution. It is based on an initial determination of a patient's respiratory movements during a scan, typically using hardware based systems. In recent years, several fully automated databased algor...

journal_title：Medical physics

authors： Kesner AL,Kuntner C

更新日期：2010-10-01 00:00:00

abstract：PURPOSE:To introduce video surface imaging guidance in synchronization with 4D cone-beam CT (CBCT) scans, and in combination with respiration- gated or target-tracked dose delivery to treat mobile tumors, without collaterally damaging nearby critical structures. METHODS:The approach uses the concept that the integral ...

journal_title：Medical physics

authors： Li S,Haiti B,Serratore D,Neicu T,Chan P,Valakh V,Bizhan M,Miyamoto C,Geng J

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:Cortical thickness and density are critical components in determining the strength of bony structures. Computed tomography (CT) is one possible modality for analyzing the cortex in 3D. In this paper, a model-based approach for measuring the cortical bone thickness and density from clinical CT images is proposed...

journal_title：Medical physics

authors： Humbert L,Hazrati Marangalou J,Del Río Barquero LM,van Lenthe GH,van Rietbergen B

更新日期：2016-04-01 00:00:00

abstract：PURPOSE:Monte Carlo (MC) simulation can be used for accurate electron beam treatment planning and modeling. Measurement of large electron fields, with the applicator removed and secondary collimator wide open, has been shown to provide accurate simulation parameters, including asymmetry in the measured dose, for the fu...

journal_title：Medical physics

authors： O'Shea TP,Foley MJ,Faddegon BA

更新日期：2011-06-01 00:00:00

abstract：:Intensity Modulated Arc Therapy (IMAT) is a rotational variant of Intensity Modulated Radiation Therapy (IMRT) that can be implemented with or without angular dose rate optimization. The purpose of this study is to determine the inter-relationship among arc range, Multi-Leaf Collimator (MLC) leaf positions and angular...

journal_title：Medical physics

authors： Oliver M,Chen J,Wong E

更新日期：2008-07-01 00:00:00

abstract：:Transmission data for 4-MV bremsstrahlung beams have been measured with a combination of lead and aluminum attenuators. From these data, the original energy spectra have been reconstructed using an iterative least-squares technique, previously evaluated by simulation studies. The spectra on the central axis for three ...

journal_title：Medical physics

authors： Huang PH,Kase KR,Bjärngard BE

更新日期：1983-11-01 00:00:00

abstract：PURPOSE:Since the introduction of clinical x-ray phase-contrast mammography (PCM), a technique that exploits refractive-index variations to create edge enhancement at tissue boundaries, a number of optimization studies employing physical image-quality metrics have been performed. Ideally, task-based assessment of PCM w...

journal_title：Medical physics

authors： Zysk AM,Brankov JG,Wernick MN,Anastasio MA

更新日期：2012-02-01 00:00:00

abstract：:In this article, we report on the development of a simple and accurate method for quality assurance of electron beam output and energy. Aluminum disks of thicknesses d(max) or d50 of the particular electron energy are positioned sequentially over a parallel-plate ion chamber and the ratio of the two signals is compare...

journal_title：Medical physics

authors： Woo MK,Videla NG

更新日期：2004-05-01 00:00:00

abstract：PURPOSE:Megavoltage grid therapy is currently delivered with step-and-shoot multisegment techniques or using a high attenuation block with divergent holes. However, the commercial availability of grid blocks is limited, their construction is difficult, and step-and-shoot techniques require longer treatment times and ar...

journal_title：Medical physics

authors： Almendral P,Mancha PJ,Roberto D

更新日期：2013-05-01 00:00:00

abstract：:The focal spot of a linear accelerator is often considered to have a fully stable position. In practice, however, the beam control loop of a linear accelerator needs to stabilize after the beam is turned on. As a result, some motion of the focal spot might occur during the start-up phase of irradiation. When acquiring...

journal_title：Medical physics

authors： Sonke JJ,Brand B,van Herk M

更新日期：2003-06-01 00:00:00

abstract：PURPOSE:Compton camera imaging (CCI) systems are currently under investigation for radiotherapy dose reconstruction and verification. The ability of such a system to provide real-time images during dose delivery will be limited by the computational speed of the image reconstruction algorithm. In this work, the authors ...

journal_title：Medical physics

authors： Mundy DW,Herman MG

更新日期：2011-01-01 00:00:00

abstract：PURPOSE:Optically stimulated luminescence (OSL) dosimetry has been recently introduced in radiation therapy as a potential alternative to the thermoluminescent dosimeter (TLD) system. The aim of this study was to investigate the feasibility of using OSL point dosimeters in the energy range used in diagnostic imaging. ...

journal_title：Medical physics

authors： Al-Senan RM,Hatab MR

更新日期：2011-07-01 00:00:00

abstract：PURPOSE:To design and quantify the shielding efficacy of an inner Borated Polyethylene (BPE)wall for a 15 MV linac in a low energy vault. METHODS:A Varian TrueBeam linac with a maximum photon energy of 15 MV was installed in asmaller, preexisting vault. This vault originally housed a low-energy machine and did not hav...

journal_title：Medical physics

authors： Speiser M,Hager F,Foster R,Solberg T

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:A nanodosimeter is a type of detector which measures single ionizations in a small gaseous volume in order to obtain ionization cluster size probability distributions for characterization of radiation types. Working nanodosimeter detectors are usually bulky machines which require a lot of space. In this work, t...

journal_title：Medical physics

authors： Vasi F,Schneider U

更新日期：2021-01-28 00:00:00

abstract：PURPOSE:An electrically floating radio frequency (RF) shielded PET insert with individual PET detectors shielded by separate Faraday cages enables the MRI built-in body RF coil to be used at least as an RF transmitter, in which the RF field penetrates the imaging region inside the PET ring through the narrow gaps betwe...

journal_title：Medical physics

authors： Akram MSH,Levin CS,Obata T,Hirumi G,Yamaya T

更新日期：2018-10-01 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：:We investigated the utility of three manual planimetric methods to quantify carotid plaque volume. A single observer measured 15 individual plaques from 15 three-dimensional (3D) ultrasound (3D US) images of patients ten times each using three different planimetric approaches. Individual plaque volumes were measured (...

journal_title：Medical physics

authors： Landry A,Ainsworth C,Blake C,Spence JD,Fenster A

更新日期：2007-04-01 00:00:00

abstract：PURPOSE:The authors discuss measurement methods and instrumentation useful for the characterization of the gray tracking performance of medical color monitors for diagnostic applications. The authors define gray tracking as the variability in the chromaticity of the gray levels in a color monitor. METHODS:The authors ...

journal_title：Medical physics

authors： Badano A,Wang J,Boynton P,Le Callet P,Cheng WC,Deroo D,Flynn MJ,Matsui T,Penczek J,Revie C,Samei E,Steven PM,Swiderski S,Van Hoey G,Yamaguchi M,Hasegawa M,Nagy BV

更新日期：2016-07-01 00:00:00

abstract：PURPOSE:The aim of in vivo skin dosimetry was to measure the absorbed dose to the skin during radiotherapy, when treatment planning calculations cannot be relied on. It is of particularly importance in hypo-fractionated stereotactic modalities, where excessive dose can lead to severe skin toxicity. Currently, commercia...

journal_title：Medical physics

authors： Vicoroski N,Espinoza A,Duncan M,Oborn BM,Carolan M,Metcalfe P,Menichelli D,Perevertaylo VL,Lerch MLF,Rosenfeld AB,Petasecca M

更新日期：2017-10-01 00:00:00

abstract：PURPOSE:Modern CT systems adjust X-ray flux accommodating for patient size to achieve certain image noise values. The effectiveness of this adaptation is an important aspect of CT performance and should ideally be characterized in the context of real patient cases. The objective of this study was to characterize CT per...

journal_title：Medical physics

authors： Ria F,Wilson JM,Zhang Y,Samei E

更新日期：2017-06-01 00:00:00

abstract：:We have performed a comprehensive dosimetric characterization of the Oncura model 6711 125I seed using both experimental [LiF thermoluminscent dosimetry (TLD)] and theoretical (Monte Carlo photon transport) methods. In addition to determining the dosimetric parameters of the 6711, this report quantified: (1) the angul...

journal_title：Medical physics

authors： Dolan J,Lia Z,Williamson JF

更新日期：2006-12-01 00:00:00

abstract：PURPOSE:Repeated brain MRI scans are performed in many clinical scenarios, such as follow up of patients with tumors and therapy response assessment. In this paper, the authors show an approach to utilize former scans of the patient for the acceleration of repeated MRI scans. METHODS:The proposed approach utilizes the...

journal_title：Medical physics

authors： Weizman L,Eldar YC,Ben Bashat D

更新日期：2015-09-01 00:00:00

abstract：PURPOSE:Color images are visualized on medical monitors that are adjusted by a grayscale standard display function (GSDF) or γ2.2. Although the GSDF is visually displayed as a linear graded grayscale, it does not specify how color medical images should be presented. On the other hand, the usual gamma setting for color ...

journal_title：Medical physics

authors： Shibutani T,Onoguchi M,Yoneyama H,Nakajima K,Matsuo S,Bamba Y,Saito S

更新日期：2019-06-01 00:00:00

abstract：PURPOSE:The purpose of this study was to investigate the impact of transverse magnetic fields on the dose response of a radiophotoluminescent glass dosimeter (RGD) in megavoltage photon beams. METHODS:The RGD relative response (i.e., RGD dose per absorbed dose to water at the midpoint of the detector in the absence of...

journal_title：Medical physics

authors： Ito S,Araki F,Ohno T

更新日期：2020-04-01 00:00:00

abstract：PURPOSE:The objective of this study is to develop a computational model for simulating 915 MHz microwave ablation (MWA), and verify the simulation predictions of transient temperature profiles against experimental measurements. Due to the limited experimental data characterizing temperature-dependent changes of tissue ...

journal_title：Medical physics

authors： Deshazer G,Hagmann M,Merck D,Sebek J,Moore KB,Prakash P

更新日期：2017-09-01 00:00:00

abstract：:Fluoroscopy is a low dose imaging technique. As such, a very sensitive detector is required to create images of good quality. Present day flat panel active matrix read out systems introduce an amount of noise that inhibits present direct and indirect methods from producing optimal quality images at fluoroscopic exposu...

journal_title：Medical physics

authors： Hunt DC,Kirby SS,Rowlands JA

更新日期：2002-11-01 00:00:00