Resolution of pinhole collimators used with gamma cameras.

abstract：PURPOSE:Osteoporosis is a common bone disease associated with increased risk of low-trauma fractures leading to substantial morbidity, mortality, and financial costs. Clinically, osteoporosis is defined by low bone mineral density (BMD); however, increasing evidence suggests that trabecular bone (TB) microarchitectural...

journal_title：Medical physics

authors： Saha PK,Liu Y,Chen C,Jin D,Letuchy EM,Xu Z,Amelon RE,Burns TL,Torner JC,Levy SM,Calarge CA

更新日期：2015-09-01 00:00:00

abstract：:Optimal visualization of moving structures such as the heart and coronary arteries using digital radiographic imaging systems is a difficult problem that can involve tradeoffs between temporal, spatial, and density resolution. The motion dependence of four angiographic measures of vessel dimensions is given and demons...

journal_title：Medical physics

authors： Parker DL,Clayton PD,Gustafson DE

更新日期：1985-11-01 00:00:00

abstract：PURPOSE:The purpose of this work was to investigate the use of an experimental complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) for tracking of moving fiducial markers during radiotherapy. METHODS:The APS has an active area of 5.4 × 5.4 cm and maximum full frame read-out rate of 20 frame s(-1),...

journal_title：Medical physics

authors： Osmond JP,Zin HM,Harris EJ,Lupica G,Allinson NM,Evans PM

更新日期：2011-11-01 00:00:00

abstract：PURPOSE:This study aims to investigate carotid plaque calcification (CPC) using two-dimensional (2D) and 3D ultrashort echo time (UTE) magnetic resonance imaging (MRI) sequences and compare T1, T2*, water concentration, and bone mineral density (BMD) of CPC with those of cortical bone. METHODS:Twelve carotid plaque sp...

journal_title：Medical physics

authors： Du J,Peterson M,Kansal N,Bydder GM,Kahn A

更新日期：2013-10-01 00:00:00

abstract：:Backscatter factors for kVps and half-value layers typical of mammographic beams have been determined as a function of beam diameter and half-value layer. The method utilized thin TLD-100 chips with the scattering medium alternately present and absent. Results indicate that the field-size dependence of the backscatter...

journal_title：Medical physics

authors： Dubuque GL,Cacak RK,Hendee WR

更新日期：1977-09-01 00:00:00

abstract：PURPOSE:New preclinical image-guided irradiators and treatment planning systems represent a huge progress in radiobiology. Nevertheless, quality control of preclinical treatments is not as advanced as in clinical radiotherapy and in vivo dosimetry is less developed. In this study, we evaluate the use of a scintillating...

journal_title：Medical physics

authors： Le Deroff C,Pérès EA,Ledoux X,Toutain J,Frelin-Labalme AM

更新日期：2020-01-01 00:00:00

abstract：:Determination of the relaxation times T1 and T2 which are important for tissue characterization generally requires the use of different pulse sequences in magnetic resonance imaging. In this study, a new pulse sequence which facilitates simultaneous determination of the T1 and T2 times is presented. Determination take...

journal_title：Medical physics

authors： Graumann R,Fischer H,Oppelt A

更新日期：1986-09-01 00:00:00

abstract：:Depending on the clinical application, it is frequently necessary to tilt the gantry of an x-ray CT system with respect to the patient and couch. For single-slice fan-beam systems, tilting the gantry introduces no errors or artifacts. Most current systems, however, are helical multislice systems with up to 16 slices. ...

journal_title：Medical physics

authors： Hein I,Taguchi K,Silver MD,Kazama M,Mori I

更新日期：2003-12-01 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

authors： Chung E,Bouchard H,Seuntjens J

更新日期：2010-06-01 00:00:00

abstract：:Electron beam dosimetry at low monitor unit (MU) settings is important for dosimetric applications. Dose linearity, beam flatness, and beam energies were studied at low MU settings with various dose rates for different types of linear accelerators. It is observed that for the scattering foil units, the dose/MU is a sm...

journal_title：Medical physics

authors： Das IJ,Harrington JC,Akber SF,Tomer AF,Murray JC,Cheng CW

更新日期：1994-06-01 00:00:00

abstract：:Complementary metal-oxide-semiconductors (CMOS) active pixel sensors can be optically coupled to CsI:Tl phosphors forming a indirect active pixel flat panel imager (APFPI) for high performance medical imaging. The aim of this work is to determine the x-ray imaging capabilities of CMOS-based APFPI and study the signal ...

journal_title：Medical physics

authors： Arvanitis CD,Bohndiek SE,Blakesley J,Olivo A,Speller RD

更新日期：2009-01-01 00:00:00

abstract：:Available deformable registration methods are often inaccurate over large organ variation encountered, for example, in the rectum and bladder. The authors developed a novel approach to accurately and effectively register large deformations in the prostate region for adaptive radiation therapy. A software tool combinin...

journal_title：Medical physics

authors： Godley A,Ahunbay E,Peng C,Li XA

更新日期：2009-04-01 00:00:00

abstract：PURPOSE:Hypoxia is one of the most important factors influencing clinical outcome after radiotherapy. Improved knowledge of factors affecting the levels and distribution of oxygen within a tumor is needed. The authors constructed a theoretical 3D model based on histological images to analyze the influence of vessel den...

journal_title：Medical physics

authors： Lagerlöf JH,Kindblom J,Cortez E,Pietras K,Bernhardt P

更新日期：2013-02-01 00:00:00

abstract：:The proper evaluation of the accuracy of a new computer program for radiation-therapy dosimetry requires consideration of both the mathematical algorithm used in the program and the performance required in clinical applications. As an example, our evaluation of the irregular-fields dosimetry program currently marketed...

journal_title：Medical physics

authors： Hallberg JR,Ibbott GS,Carson PL,Hendee WR

更新日期：1977-11-01 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

authors： Chen X,Cvetkovic D,Ma CM,Chen L

更新日期：2012-05-01 00:00:00

abstract：PURPOSE:MR thermometry based on the proton resonance frequency shift (PRFS) is the most commonly used method for the monitoring of thermal therapies. As the chemical shift of water protons is temperature dependent, the local temperature variation (relative to an initial baseline) may be calculated from time-dependent p...

journal_title：Medical physics

authors： Viallon M,Terraz S,Roland J,Dumont E,Becker CD,Salomir R

更新日期：2010-04-01 00:00:00

abstract：:Techniques have been developed for reducing motion blurring artifacts by using respiratory gated computed tomography (CT) in sinogram space and quantitatively evaluating the artifact reduction. A synthetic sinogram was built from multiple scans intercepting a respiratory gating window. A gated CT image was then recons...

journal_title：Medical physics

authors： Lu W,Parikh PJ,Hubenschmidt JP,Politte DG,Whiting BR,Bradley JD,Mutic S,Low DA

更新日期：2005-11-01 00:00:00

abstract：PURPOSE:The accuracy of a six degree of freedom (6DoF) couch was evaluated using a novel method. METHODS:Cone beam CT (CBCT) images of a 3D phantom (IsoCal) were acquired with different, known combinations of couch pitch and roll angles. Pitch and roll angles between the maximum allowable values of 357 and 3 degrees w...

journal_title：Medical physics

authors： Zhang Q,Driewer J,Wang S,Li S,Zhu X,Zheng D,Cao Y,Zhang J,Jamshidi A,Cox BW,Knisely JPS,Potters L,Klein EE

更新日期：2017-08-01 00:00:00

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：:Heat therapies such as hyperthermia and thermoablation are very promising approaches in the treatment of cancer. Compared with available hyperthermia modalities, magnetic fluid hyperthermia (MFH) yields better results in uniform heating of the deeply situated tumors. In this approach, fluid consisting of superparamagn...

journal_title：Medical physics

authors： Tasci TO,Vargel I,Arat A,Guzel E,Korkusuz P,Atalar E

更新日期：2009-05-01 00:00:00

abstract：PURPOSE:In a recent paper by Bouchard et al. [Med. Phys. 36(10), 4654-4663 (2009)], a theoretical model of quality correction factors for idealistic so-called plan-class specific reference (PCSR) fields was proposed. The reasoning was founded on the definition of PCSR fields made earlier by Alfonso et al. [Med. Phys. 3...

journal_title：Medical physics

authors： Bouchard H,Seuntjens J,Palmans H

更新日期：2012-03-01 00:00:00

abstract：:Currently, patients with brain neoplasms must undergo both computed tomography (CT) and magnetic resonance (MR) imaging to take advantage of CT's density information and MR's soft tissue imaging capabilities. A method has been developed that allows virtual simulation, digitally reconstructed radiographs (DRRs), and 3-...

journal_title：Medical physics

authors： Ramsey CR,Oliver AL

更新日期：1998-10-01 00:00:00

abstract：PURPOSE:The aim of this study is to understand the characteristics of secondary electrons generated from the interaction of gold nanoparticles (GNPs) with x-rays as a function of nanoparticle size and beam energy and thereby further the understanding of GNP-enhanced radiotherapy. METHODS:The effective range, deflectio...

journal_title：Medical physics

authors： Leung MK,Chow JC,Chithrani BD,Lee MJ,Oms B,Jaffray DA

更新日期：2011-02-01 00:00:00

abstract：:A computer dose model for a low energy gamma-emitting stent in a heterogeneous medium is described. The method is based on the Sievert model which is adapted to the dose-point-kernel (DPK) model to compute the dose distribution about filtered gamma sources (Sievert-DPK model). The new gamma stent model can take into a...

journal_title：Medical physics

authors： Janicki C,Duggan DM,Rahdert DA

更新日期：2001-07-01 00:00:00

abstract：PURPOSE:Currently, no 3D or 4D volumetric x-ray imaging techniques are available for intrafraction verification of target position during actual treatment delivery or in-between treatment beams, which is critical for stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) treatments. This study a...

journal_title：Medical physics

authors： Ren L,Zhang Y,Yin FF

更新日期：2014-02-01 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：PURPOSE:Small animal immobilization devices facilitate positioning of animals for reproducible imaging and accurate focal radiation therapy. In this study, the authors demonstrate the use of three-dimensional (3D) printing technology to fabricate a custom-designed mouse head restraint. The authors evaluate the accuracy...

journal_title：Medical physics

authors： Zarghami N,Jensen MD,Talluri S,Foster PJ,Chambers AF,Dick FA,Wong E

更新日期：2015-11-01 00:00:00

abstract：:Absorbed doses from main charged-particle beams and charged-particle fragments have been measured with high accuracy for particle therapy, but there are few reports for doses from neutron components produced as fragments. This study describes the measurements on neutron doses produced by carbon beams; microdosimetric ...

journal_title：Medical physics

authors： Endo S,Tanaka K,Takada M,Onizuka Y,Miyahara N,Sato T,Ishikawa M,Maeda N,Hayabuchi N,Shizuma K,Hoshi M

更新日期：2007-09-01 00:00:00

abstract：PURPOSE:A modular phantom for dosimetry and imaging performance evaluation in cone-beam computed tomography (CBCT) is reported, providing a tool for quantitative technical assessment that can be adapted to a broad variety of CBCT imaging configurations and clinical applications. METHODS:The phantom presents a set of m...

journal_title：Medical physics

authors： Siewerdsen JH,Uneri A,Hernandez AM,Burkett GW,Boone JM

更新日期：2020-02-01 00:00:00

abstract：PURPOSE:It is important for many quantitative brain studies to label meaningful anatomical regions in MR brain images. However, due to high complexity of brain structures and ambiguous boundaries between different anatomical regions, the anatomical labeling of MR brain images is still quite a challenging task. In many ...

journal_title：Medical physics

authors： Ma G,Gao Y,Wu G,Wu L,Shen D

更新日期：2016-02-01 00:00:00