Peripheral dose distributions for a linear accelerator equipped with a secondary multileaf collimator and universal wedge.

Abstract:

:The American Association of Physicists in Medicine Task Group 36 (AAPM TG-36) data can be used to estimate peripheral dose (PD) distributions outside the primary radiation field. However, the report data does not apply to linear accelerators equipped with a multileaf collimator (MLC) and universal wedge (UW). Tertiary multileaf collimators have been shown to significantly affect PD distributions and TG-36 reported data. Measurements were performed to evaluate PD distributions for a linear accelerator equipped with a secondary MLC, backup diaphragms, and UW. This data can be used to compliment the TG-36 report for estimation of doses to critical structures outside primary radiation fields. For the evaluated linear accelerator, an MLC is incorporated in the upper secondary collimator jaws. Backup shielding diaphragms are located underneath the MLC. At the nominal collimator position, the MLC and the backup diaphragm provide collimation primarily in the transverse direction. Conventional, solid tungsten-alloy jaws, located underneath the backup diaphragms, provide secondary collimation in the longitudinal direction. The universal wedge provides dose modulation in the direction of the conventional jaws. Measurements were made with an ionization chamber inserted into a 20x40x120 cm(3) water-equivalent plastic phantom with the secondary collimator and MLC settings of 5x5, 10x10, 15x15, and 25x25 cm(2) with and without UW. Data was acquired along the machine's longitudinal axis for 6, 10, and 18 MV photons. Peripheral dose distributions were measured with the collimator rotated to 0 degrees and 270 degrees for open field measurements and to 0 degrees, 180 degrees, and 270 degrees for wedged fields (IEC 1217). This allowed evaluation of peripheral dose distributions as a function of collimator rotation. Wedged fields were normalized to deliver the same dose at the depth of maximum dose on the central axis as open fields. The measured PD distributions were generally comparable to data reported by TG-36. At distances close to the field edge (less than 30 or 40 cm), the measured PD distributions were lower when the measurement point was shielded by solid jaws than with MLC and backup diaphragm. At longer distances, this trend reversed for all energies and evaluated field sizes. However, the difference in PD distribution with collimator rotation was not large enough to warrant strategic positioning of the collimator to reduce dose to critical structures outside the primary radiation field. Because internal scatter dominates close to the field edge, wedged PD distributions were comparable to open field doses at distances closer than 30 cm. However, at distances larger than 30 cm from the field edge, wedged PD distributions were significantly grater than those for open fields due to increased contribution of leakage radiation. Increased leakage radiation is due to the increase in wedged field monitor units, which is related to a small wedge factor (0.27 to 0.29).

journal_name

J Appl Clin Med Phys

authors

Mutic S,Esthappan J,Klein EE

doi

10.1120/jacmp.v3i4.2554

keywords:

subject

Has Abstract

pub_date

2002-10-01 00:00:00

pages

302-9

issue

4

issn

1526-9914

journal_volume

3

pub_type

杂志文章
  • Statistical process control and verifying positional accuracy of a cobra motion couch using step-wedge quality assurance tool.

    abstract::This study utilizes process control techniques to identify action limits for TomoTherapy couch positioning quality assurance tests. A test was introduced to monitor accuracy of the applied couch offset detection in the TomoTherapy Hi-Art treatment system using the TQA "Step-Wedge Helical" module and MVCT detector. Ind...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1002/acm2.12136

    authors: Binny D,Lancaster CM,Trapp JV,Crowe SB

    更新日期:2017-09-01 00:00:00

  • Impact of magnetic field regulation in conjunction with the volumetric repainting technique on the spot positions and beam range in pencil beam scanning proton therapy.

    abstract:PURPOSE:The objective of this study was to evaluate the impact of the magnetic field regulation in conjunction with the volumetric repainting technique on the spot positions and range in pencil beam scanning proton therapy. METHODS:"Field regulation" - a feature to reduce the switching time between layers by applying ...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1002/acm2.13045

    authors: Rana S,Bennouna J,Gutierrez AN,Rosenfeld AB

    更新日期:2020-10-15 00:00:00

  • A new homogeneity index based on statistical analysis of the dose-volume histogram.

    abstract::The goal of the present study was to develop a new dose-volume histogram (DVH)- based homogeneity index for effectively evaluating the dose homogeneity of intensity-modulated radiotherapy plans. The new index, called the sigma-index ("S-index") is defined as the standard deviation of the normalized differential DVH cu...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v8i2.2390

    authors: Yoon M,Park SY,Shin D,Lee SB,Pyo HR,Kim DY,Cho KH

    更新日期:2007-03-20 00:00:00

  • Technical Note: Comparison of the internal target volume (ITV) contours and dose calculations on 4DCT, average CBCT, and 4DCBCT imaging for lung stereotactic body radiation therapy (SBRT).

    abstract:PURPOSE:To investigate the differences between internal target volumes (ITVs) contoured on the simulation 4DCT and daily 4DCBCT images for lung cancer patients treated with stereotactic body radiotherapy (SBRT) and determine the dose delivered on 4D planning technique. METHODS:For nine patients, 4DCBCTs were acquired ...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1002/acm2.13041

    authors: Dumas M,Laugeman E,Sevak P,Snyder KC,Mao W,Chetty IJ,Ajlouni M,Wen N

    更新日期:2020-10-12 00:00:00

  • Accurate method for evaluating the duration of the entire radiotherapy process.

    abstract:BACKGROUND AND PURPOSE:Along with the increasing demand for high-quality radiotherapy and the growing number of high-precision radiotherapy devices, precise radiotherapy workflow management and accurate time evaluation of the entire radiotherapy process are crucial to providing appropriate, timely treatment for cancer ...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1002/acm2.12959

    authors: Guo C,Huang P,Li Y,Dai J

    更新日期:2020-09-01 00:00:00

  • Small field electron beam dosimetry using MOSFET detector.

    abstract::The dosimetry of very small electron fields can be challenging due to relative shifts in percent depth-dose curves, including the location of dmax, and lack of lateral electronic equilibrium in an ion chamber when placed in the beam. Conventionally a small parallel plate chamber or film is utilized to perform small fi...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v12i1.3267

    authors: Amin MN,Heaton R,Norrlinger B,Islam MK

    更新日期:2010-10-04 00:00:00

  • Combination effects of tissue heterogeneity and geometric targeting error in stereotactic body radiotherapy for lung cancer using CyberKnife.

    abstract::We have investigated the combined effect of tissue heterogeneity and its variation associated with geometric error in stereotactic body radiotherapy (SBRT) for lung cancer. The treatment plans for eight lung cancer patients were calculated using effective path length (EPL) correction and Monte Carlo (MC) algorithms, w...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v16i5.5397

    authors: Kang KM,Jeong BK,Choi HS,Yoo SH,Hwang UJ,Lim YK,Jeong H

    更新日期:2015-09-08 00:00:00

  • Deriving detector-specific correction factors for rectangular small fields using a scintillator detector.

    abstract::The goal of this study was to investigate small field output factors (OFs) for flat-tening filter-free (FFF) beams on a dedicated stereotactic linear accelerator-based system. From this data, the collimator exchange effect was quantified, and detector-specific correction factors were generated. Output factors for 16 j...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v17i6.6433

    authors: Qin Y,Zhong H,Wen N,Snyder K,Huang Y,Chetty IJ

    更新日期:2016-11-08 00:00:00

  • Comparing gamma knife and cyberknife in patients with brain metastases.

    abstract::The authors compared the relative dosimetric merits of Gamma Knife (GK) and CyberKnife (CK) in 15 patients with 26 brain metastases. All patients were initially treated with the Leksell GK 4C. The same patients were used to generate comparative CK treatment plans. The tissue volume receiving more than 12 Gy (V12), the...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v15i1.4095

    authors: Sio TT,Jang S,Lee SW,Curran B,Pyakuryal AP,Sternick ES

    更新日期:2014-01-06 00:00:00

  • Electron energy constancy verification using a double-wedge phantom.

    abstract::Routine constancy checks of electron energy are often time consuming because of the necessity to measure a dose at two depths. A technique is described that uses a double-wedge shaped phantom positioned on a Profiler diode array for measuring an electron energy constancy metric similar to R(50). The double-wedge elect...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v4i3.2516

    authors: Wells DM,Picco PJ,Ansbacher W

    更新日期:2003-07-01 00:00:00

  • Effect of electron contamination on in vivo dosimetry for lung block shielding during TBI.

    abstract::Our institution performs in vivo verification measurement for each of our total body irradiation (TBI) patients with optically stimulated luminescent dosimeters (OSLD). The lung block verification measurements were commonly higher than expected. The aim of this work is to understand this discrepancy and improve the ac...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v17i3.6128

    authors: Narayanasamy G,Cruz W,Saenz DL,Stathakis S,Papanikolaou N,Kirby N

    更新日期:2016-05-08 00:00:00

  • Assessment of error in the MV radiation isocenter position calculated with the Elekta XVI software.

    abstract::The assessment of the coincidence of imaging and radiation isocenters is an important task of regular quality assurance of medical linear accelerators (linacs) as recommended in national and international quality assurance guidelines. A previously reported investigation of the accuracy of the Elekta XVI software to lo...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1002/acm2.12861

    authors: Chojnowski JM,Warr GB,Sykes JR,Thwaites DI

    更新日期:2020-05-01 00:00:00

  • Dosimetric comparison of preoperative single-fraction partial breast radiotherapy techniques: 3D CRT, noncoplanar IMRT, coplanar IMRT, and VMAT.

    abstract::The purpose of this study was to compare dosimetric parameters of treatment plans among four techniques for preoperative single-fraction partial breast radiotherapy in order to select an optimal treatment technique. The techniques evaluated were noncoplanar 3D conformal radiation therapy (3D CRT), noncoplanar intensit...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v16i1.5126

    authors: Yoo S,Blitzblau R,Yin FF,Horton JK

    更新日期:2015-01-08 00:00:00

  • Evaluation of three APBI techniques under NSABP B-39 guidelines.

    abstract::This work compares two accelerated partial breast irradiation modalities, MammoSite brachytherapy and three dimensional conformal radiotherapy (3D-CRT), to a new method, SAVI brachytherapy, following NSABP B-39 guidelines. A total of 21 patients treated at UC San Diego with the SAVI device were evaluated in this compa...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v11i1.3021

    authors: Scanderbeg D,Yashar C,White G,Rice R,Pawlicki T

    更新日期:2009-12-03 00:00:00

  • AAPM Medical Physics Practice Guideline 5.a.: Commissioning and QA of Treatment Planning Dose Calculations - Megavoltage Photon and Electron Beams.

    abstract::The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education and professional practice of medical physics. The AAPM has more than 8,000 members and is the principal organization of medical physicists in the United States. The...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v16i5.5768

    authors: Smilowitz JB,Das IJ,Feygelman V,Fraass BA,Kry SF,Marshall IR,Mihailidis DN,Ouhib Z,Ritter T,Snyder MG,Fairobent L,AAPM Medical Physics Practice Guideline Task Group.

    更新日期:2015-09-08 00:00:00

  • Clinical and imaging characteristics of breast ductal carcinoma in situ with microinvasion.

    abstract:BACKGROUND:We analyzed the clinical and imaging characteristics of patients with breast ductal carcinoma in situ with microinvasion (DCISM) and breast ductal carcinoma in situ (DCIS). METHODS:We analyzed the records of 40 patients diagnosed with DCISM and 61 patients with DCIS who were hospitalized at Shengjing Hospit...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1002/acm2.13122

    authors: Han S,Qiu F,Han Y,Xu Y,Yin J,Xing F,Bian X,He G

    更新日期:2020-12-17 00:00:00

  • Frameless stereotactic body radiation therapy for multiple lung metastases.

    abstract::Two patients with multiple lung metastases (≥ 5) were treated using frameless stereotactic body radiation therapy (SBRT) on an Elekta Axesse linear accelerator equipped with an interdigitation-capable multileaf collimator and four-dimensional cone-beam CT (4D CBCT). The technique and the early clinical outcomes were e...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v15i4.4737

    authors: Li Q,Mu J,Gu W,Chen Y,Ning Z,Jin J,Pei H

    更新日期:2014-07-08 00:00:00

  • Translucent poly(vinyl alcohol) cryogel dosimeters for simultaneous dose buildup and monitoring during chest wall radiation therapy.

    abstract::Chest wall radiation therapy treatment delivery was monitored using a 5 mm thick radiochromic poly(vinyl alcohol) cryogel that also provided buildup material. The cryogels were used to detect positioning errors and measure the impact of shifts for a chest wall treatment that was delivered to a RANDO phantom. The phant...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v17i5.6148

    authors: Eyadeh MM,Weston MA,Juhasz J,Diamond KR

    更新日期:2016-09-08 00:00:00

  • Future trends in the supply and demand for radiation oncology physicists.

    abstract::Significant controversy surrounds the 2012 / 2014 decision announced by the Trustees of the American Board of Radiology (ABR) in October of 2007. According to the ABR, only medical physicists who are graduates of a Commission on Accreditation of Medical Physics Education Programs, Inc. (CAMPEP) accredited academic or ...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v11i2.3005

    authors: Mills MD,Thornewill J,Esterhay RJ

    更新日期:2010-04-12 00:00:00

  • Gantry angle determination during arc IMRT: evaluation of a simple EPID-based technique and two commercial inclinometers.

    abstract::The increasing popularity of intensity-modulated arc therapy (IMAT) treatments requires specifically designed linac quality assurance (QA) programs. Gantry angle is one of the parameters that has a major effect on the outcome of IMAT treatments since dose reconstruction for patient-specific QA relies on the gantry ang...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v13i6.3981

    authors: Rowshanfarzad P,Sabet M,O'Connor DJ,McCowan PM,McCurdy BM,Greer PB

    更新日期:2012-11-08 00:00:00

  • Role of adaptive radiation therapy for pediatric patients with diffuse pontine glioma.

    abstract::We investigate the role of adaptive radiation therapy in pediatric patients with diffuse pontine glioma and the impact of steroid-related weight gain on treatment parameters utilizing cone-beam CT. Fifteen patients with diffuse pontine glioma were treated with three-dimensional conformal radiation therapy and enrolled...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:

    authors: Beltran C,Sharma S,Merchant TE

    更新日期:2011-01-30 00:00:00

  • Patient-specific 17-segment myocardial modeling on a bull's eye map.

    abstract::The purpose of this study was to develop and validate cardiac computed tomog-raphy (CT) quantitative analysis software with a patient-specific, 17-segment myocardial model that uses electrocardiogram (ECG)-gated cardiac CT images to differentiate between normal controls and severe aortic stenosis (AS) patients. ECG-ga...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v17i5.6237

    authors: Jung J,Kim YH,Kim N,Yang DH

    更新日期:2016-09-08 00:00:00

  • Dosimetric characterization and use of GAFCHROMIC EBT3 film for IMRT dose verification.

    abstract::Radiochromic film has become an important tool to verify dose distributions in highly conformal radiation therapy such as IMRT. Recently, a new generation of these films, EBT3, has become available. EBT3 has the same composition and thickness of the sensitive layer of the previous EBT2 films, but its symmetric layer c...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v14i2.4111

    authors: Casanova Borca V,Pasquino M,Russo G,Grosso P,Cante D,Sciacero P,Girelli G,La Porta MR,Tofani S

    更新日期:2013-03-04 00:00:00

  • Optimization of motion management parameters in a synchrotron-based spot scanning system.

    abstract:PURPOSE:To quantify the effects of combining layer-based repainting and respiratory gating as a strategy to mitigate the dosimetric degradation caused by the interplay effect between a moving target and dynamic spot-scanning proton delivery. METHODS:An analytic routine modeled three-dimensional dose distributions of p...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1002/acm2.12702

    authors: Johnson JE,Herman MG,Kruse JJ

    更新日期:2019-09-01 00:00:00

  • Evaluation of the influence of tumor location and size on the difference of dose calculation between Ray Tracing algorithm and Fast Monte Carlo algorithm in stereotactic body radiotherapy of non-small cell lung cancer using CyberKnife.

    abstract::This study evaluated the extent of improvement in dose predication accuracy achieved by the Fast Monte Carlo algorithm (MC) compared to the Ray Tracing algorithm (RAT) in stereotactic body radiotherapy (SBRT) of non-small cell lung cancer (NSCLC), and how their differences were influenced by the tumor site and size. T...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v14i5.4280

    authors: Wu VW,Tam KW,Tong SM

    更新日期:2013-09-06 00:00:00

  • Measurement of gantry rotation time in modern ct.

    abstract::The purpose of this study was to develop and evaluate a noninvasive method to assess rotation time in modern commercial computed tomography (CT) systems. The rotation time was measured at a selected nominal rotation time (400 ms) utilizing two types of solid-state detectors: the RTI's CT Dose Profiler (CTDP) and Unfor...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v15i1.4517

    authors: Fukuda A,Lin PJ,Matsubara K,Miyati T

    更新日期:2014-01-06 00:00:00

  • Independent calculation of dose from a helical TomoTherapy unit.

    abstract::A new calculation algorithm has been developed for independently verifying doses calculated by the TomoTherapy Hi.Art treatment planning system (TPS). The algorithm is designed to confirm the dose to a point in a high dose, low dose-gradient region. Patient data used by the algorithm include the radiological depth to ...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v10i1.2772

    authors: Gibbons JP,Smith K,Cheek D,Rosen I

    更新日期:2009-02-05 00:00:00

  • Improving a scissor-action couch for conformal arc radiotherapy and radiosurgery.

    abstract::We have developed a method to improve the setup accuracy of a Varian Clinac 6/100 couch for delivering conformal arc therapy using a tertiary micro multileaf collimator (MLC) system. Several immobilization devices have been developed to improve the mechanical stability and isocenter alignment of the couch: turn-knob h...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v5i3.2026

    authors: Li K,Yu CX,Ma L

    更新日期:2004-07-01 00:00:00

  • Impact of incorporating visual biofeedback in 4D MRI.

    abstract::Precise radiation therapy (RT) for abdominal lesions is complicated by respiratory motion and suboptimal soft tissue contrast in 4D CT. 4D MRI offers improved con-trast although long scan times and irregular breathing patterns can be limiting. To address this, visual biofeedback (VBF) was introduced into 4D MRI. Ten v...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v17i3.6017

    authors: To DT,Kim JP,Price RG,Chetty IJ,Glide-Hurst CK

    更新日期:2016-05-08 00:00:00

  • Shielding assessment of a mobile electron accelerator for intra-operative radiotherapy.

    abstract::The purpose of this investigation is to measure, characterize and report stray photon leakage and scatter radiation measurements from the Mobetron, an intraoperative electron linear accelerator designed for use in an operating room environment. The study is needed due to recent changes to the shielding design of the M...

    journal_title:Journal of applied clinical medical physics

    pub_type: 杂志文章

    doi:10.1120/jacmp.v11i4.3151

    authors: Krechetov AS,Goer D,Dikeman K,Daves JL,Mills MD

    更新日期:2010-09-07 00:00:00