Reconstruction of electron spectra from depth doses with adaptive regularization.

Abstract:

:Electron spectral reconstruction of medical accelerators from measured depth doses is a practical method for providing the input initial phase space distribution at the patient surface that is required by Monte Carlo treatment planning systems. The posed inverse problem of spectral reconstruction is ill conditioned and this may lead to nonphysical oscillations in the reconstructed spectra. Use of a variational method of solution with a regularization technique removes the oscillations but tends to smooth the sharp (deltalike) energy peak that is a common feature in electron spectra generated by medical accelerators. Because the sharp peak contains a large percentage of the electrons in the spectrum, an accurate estimate of the peak width, height and position is critical to the success of the technique for spectrum reconstruction with regularization. We propose use of an adaptive regularization term as a special form of the general Tichonov regularization function. The variational method with the adaptive regularization term is applied to reconstruct electron spectra for the 6, 9, and 18 MeV electron beams of a Varian Clinac 2100C accelerator and proves to be a very simple, effective and accurate approach. Results using this variational method with adaptive regularization almost perfectly reconstruct electron spectra from depth dose distributions.

journal_name

Med Phys

journal_title

Medical physics

authors

Wei J,Sandison GA,Chvetsov AV

doi

10.1118/1.2161404

subject

Has Abstract

pub_date

2006-02-01 00:00:00

pages

354-9

issue

2

eissn

0094-2405

issn

2473-4209

journal_volume

33

pub_type

杂志文章
  • SU-E-I-69: Magnetic Resonance Metal Artifact Evaluation with Routine Clinical Cardiac Sequences.

    abstract:PURPOSE:To examine schemes to grade the severity of metal susceptibility artifacts on image quality using cardiac MRI pulse sequences. METHODS:A post-thoracotomy patient was simulated with a stainless steel sternal wire (Syneture,MA; size=6, diameter=48mm), placed securely on an ACR MRI phantom. Phantom was scanned on...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.4734785

    authors: Joyner D,Rivard A,Craft D,Liu T,Callaway S,James J

    更新日期:2012-06-01 00:00:00

  • Quasi real time in vivo dosimetry for VMAT.

    abstract:PURPOSE:Results about the feasibility of a method for quasi real time in vivo dosimetry (IVD) at the isocenter point for volumetric modulated arc therapy (VMAT) are here reported. The method is based on correlations between the EPID signal and the dose on the beam central axis. Moreover, the γ-analysis of EPID images w...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.4875685

    authors: Fidanzio A,Porcelli A,Azario L,Greco F,Cilla S,Grusio M,Balducci M,Valentini V,Piermattei A

    更新日期:2014-06-01 00:00:00

  • A real-time prostate cancer detection technique using needle insertion force and patient-specific criteria during percutaneous intervention.

    abstract::In this article, the authors present a novel real-time cancer detection technique by using needle insertion forces in conjunction with patient-specific criteria during percutaneous interventions. Needle insertion experiments and pathological analysis were performed for developing a computer-aided detection (CAD) model...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.3148834

    authors: Yan K,Li L,Joseph J,Rubens DR,Messing EM,Liao L,Yu Y

    更新日期:2009-07-01 00:00:00

  • Uncertainties in IMRT dosimetry.

    abstract:PURPOSE:The purpose of this study is to investigate some characteristics of the beam delivery system and their effects on the dose distribution of intensity-modulated radiation therapy (IMRT) and the results of patient-specific IMRT quality assurance (QA). These characteristics include the accelerator source distributi...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.3413997

    authors: Li JS,Lin T,Chen L,Price RA Jr,Ma CM

    更新日期:2010-06-01 00:00:00

  • Monitoring radiation use in cardiac fluoroscopy imaging procedures.

    abstract:PURPOSE:Timely identification of systematic changes in radiation delivery of an imaging system can lead to a reduction in risk for the patients involved. However, existing quality assurance programs involving the routine testing of equipment performance using phantoms are limited in their ability to effectively carry o...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.3524224

    authors: Stevens NT,Steiner SH,Smith IR,MacKay RJ

    更新日期:2011-01-01 00:00:00

  • SU-E-T-485: Validation of Acuros XB Dose Calculations in SBRT Lung Planning with Monte Carlo Methods.

    abstract:PURPOSE:The Acuros XB (AXB) Advanced Dose algorithm (Varian Medical Systems) represents a dramatic shift in clinical photon dose calculation methodology from pencil-beam superposition/convolution methods. Early studies evaluating the accuracy of the algorithm in lung have found good agreement with both measurement and ...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.4735574

    authors: Bush K,Wang L,Mok E

    更新日期:2012-06-01 00:00:00

  • The role of humidity and other correction factors in the AAPM TG-21 dosimetry protocol.

    abstract::A detailed derivation is presented of the formulas required to determine Ngas and Dmed in the AAPM TG-21 dosimetry protocol. This protocol specifies how to determine the absorbed dose in an electron or photon beam when using exposure or absorbed dose calibrated ion chambers. It is shown that the expression given in TG...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.596292

    authors: Rogers DW,Ross CK

    更新日期:1988-01-01 00:00:00

  • Unexpectedly large dose rate dependent output from a linear accelerator.

    abstract::During our routine calibration of a Varian Clinac-20 linear accelerator, the absorbed dose for a fixed monitor unit (mu) was found to decrease with increasing dose rate. Between dose rates of 100 and 500 mu/min, there was up to 20% difference in absorbed dose for a 20-MeV electron beam. The cause of this problem was a...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.596192

    authors: Cheng PC,Kubo H

    更新日期:1988-09-01 00:00:00

  • SU-E-T-300: Monte Carlo Simulation of Single-Plane Magnetically Focused Narrow Proton Beams.

    abstract::Purpose To investigate narrow, elongated magnetically focused proton beams and compare their properties with passively collimated beams using Monte Carlo simulation. METHODS:We performed Geant4 Monte Carlo simulations involving a single quadrapole focusing magnet, thereby creating a flattened beam with an elongated e...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.4735386

    authors: McAuley G,Barnes S,Wroe A,Slater J

    更新日期:2012-06-01 00:00:00

  • SU-E-I-57: CT Dose Metrics: What Are We Tracking.

    abstract:PURPOSE:Recent guidance by The Joint Commission and CRCPD recommendations require establishing CT reference dose levels (RDLs) for clinical protocols and recording CT dose metrics in the patient's medical record. This presentation addresses which dose values in the CT report should be recorded for the purposes of monit...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.4734773

    authors: Guild J,Arbique G,Blackburn T,Gallet J,Anderson J

    更新日期:2012-06-01 00:00:00

  • Radiofrequency penetration and absorption in the human body: limitations to high-field whole-body nuclear magnetic resonance imaging.

    abstract::This study presents experimental results about the effective depth of penetration and about the radiofrequency (rf) power absorption in humans as a function of frequency. The frequency range investigated covers 10 up to 220 MHz. For the main part, the results were derived from bench measurements of the quality factor ...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.595995

    authors: Röschmann P

    更新日期:1987-11-01 00:00:00

  • Dynamic field-of-view imaging to increase temporal resolution in the early phase of contrast media uptake in breast DCE-MRI: A feasibility study.

    abstract:PURPOSE:To increase diagnostic accuracy of breast MRI by increasing temporal resolution and more accurately sampling the early kinetics of contrast media uptake. We tested the feasibility of accelerating bilateral breast DCE-MRI by reducing the FOV, allowing aliasing, and unfolding the resulting images. METHODS:Previo...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1002/mp.12747

    authors: Pineda FD,Easley TO,Karczmar GS

    更新日期:2018-03-01 00:00:00

  • Design and evaluation of a HDR skin applicator with flattening filter.

    abstract::The purposes of this study are: (i) to design field flattening filters for the Leipzig applicators of 2 and 3 cm of inner diameter with the source traveling parallel to the applicator contact surface, which are accessories of the microSelectron-HDR afterloader (Nucletron, Veenendaal, The Netherlands). These filters, m...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.2825622

    authors: Granero D,Pérez-Calatayud J,Gimeno J,Ballester F,Casal E,Crispín V,van der Laarse R

    更新日期:2008-02-01 00:00:00

  • Rigid 2D/3D slice-to-volume registration and its application on fluoroscopic CT images.

    abstract::Registration of single slices from FluoroCT, CineMR, or interventional magnetic resonance imaging to three dimensional (3D) volumes is a special aspect of the two-dimensional (2D)/3D registration problem. Rather than digitally rendered radiographs (DRR), single 2D slice images obtained during interventional procedures...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.2401661

    authors: Birkfellner W,Figl M,Kettenbach J,Hummel J,Homolka P,Schernthaner R,Nau T,Bergmann H

    更新日期:2007-01-01 00:00:00

  • Diamond detector versus silicon diode and ion chamber in photon beams of different energy and field size.

    abstract::The aim of this work was to test the suitability of a PTW diamond detector for nonreference condition dosimetry in photon beams of different energy (6 and 25 MV) and field size (from 2.6 cm x 2.6 cm to 10 cm x 10 cm). Diamond behavior was compared to that of a Scanditronix p-type silicon diode and a Scanditronix RK io...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.1591431

    authors: Bucciolini M,Buonamici FB,Mazzocchi S,De Angelis C,Onori S,Cirrone GA

    更新日期:2003-08-01 00:00:00

  • Optimized radial and angular positions in Monte Carlo modeling.

    abstract::In Monte Carlo simulations of light transport in tissues, a grid system is set up to score physical quantities. This study of cylindrically symmetrical problems found that the optimized radial and angular positions for the averaged physical quantities in each grid element are off-center. The error of the extrapolated ...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.597351

    authors: Wang L,Jacques SL

    更新日期:1994-07-01 00:00:00

  • Evaluation of the accuracy of fetal dose estimates using TG-36 data.

    abstract::The American Association of Physicists in Medicine Radiation Therapy Committee Task Group 36 report (TG-36) provides guidelines for managing radiation therapy of pregnant patients. Included in the report are data that can be used to estimate the dose to the fetus. The purpose of this study is to evaluate the accuracy ...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.2710332

    authors: Kry SF,Starkschall G,Antolak JA,Salehpour M

    更新日期:2007-04-01 00:00:00

  • Assessment of image quality and scatter and leakage radiation of an integrated MR-LINAC system.

    abstract:PURPOSE:To assess the image quality, scatter, and leakage radiation of an integrated magnetic resonance linear accelerator (MR-LINAC or MRL) system. METHODS:A large American College of Radiology (ACR) magnetic resonance imaging (MRI) accreditation phantom was used to evaluate the MRI capabilities of the integrated MRL...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1002/mp.12767

    authors: Wang J,Yung J,Kadbi M,Hwang K,Ding Y,Ibbott GS

    更新日期:2018-03-01 00:00:00

  • Stereotactic mammography imaging combined with 3D US imaging for image guided breast biopsy.

    abstract::Stereotactic X-ray mammography (SM) and ultrasound (US) guidance are both commonly used for breast biopsy. While SM provides three-dimensional (3D) targeting information and US provides real-time guidance, both have limitations. SM is a long and uncomfortable procedure and the US guided procedure is inherently two dim...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.2794175

    authors: Surry KJ,Mills GR,Bevan K,Downey DB,Fenster A

    更新日期:2007-11-01 00:00:00

  • Accurate assessment and prediction of noise in clinical CT images.

    abstract:PURPOSE:The objectives of this study were (a) to devise a technique for measuring quantum noise in clinical body computed tomography (CT) images and (b) to develop a model for predicting that noise with high accuracy. METHODS:The study included 83 clinical image sets at two dose levels (clinical and 50% reduced dose l...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.4938588

    authors: Tian X,Samei E

    更新日期:2016-01-01 00:00:00

  • A fast double template convolution isocenter evaluation algorithm with subpixel accuracy.

    abstract:PURPOSE:To design a fast Winston Lutz (fWL) algorithm for accurate analysis of radiation isocenter from images without edge detection or center of mass calculations. METHODS:An algorithm has been developed to implement the Winston Lutz test for mechanical/ radiation isocenter agreement using an electronic portal imagi...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.3524227

    authors: Winey B,Sharp G,Bussière M

    更新日期:2011-01-01 00:00:00

  • Sinusoidal modulation analysis for optical system MTF measurements.

    abstract::The modulation transfer function (MTF) is a commonly used metric for defining the spatial resolution characteristics of imaging systems. While the MTF is defined in terms of how an imaging system demodulates the amplitude of a sinusoidal input, this approach has not been in general use to measure MTFs in the medical i...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.597840

    authors: Boone JM,Yu T,Seibert JA

    更新日期:1996-12-01 00:00:00

  • Dosimetry for 252Cf neutron emitting brachytherapy sources: protocol, measurements, and calculations.

    abstract::The mixed-field dosimetry for 252Cf Applicator Tube (AT) type medical sources available from Oak Ridge National Laboratory (ORNL) has been characterized using ionization chambers, a GM counter, and Monte Carlo methods. Unlike the AAPM Task Group No. 43 (TG-43), specification of dose to muscle instead of water is recom...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.598646

    authors: Rivard MJ

    更新日期:1999-08-01 00:00:00

  • Factors influencing the performance of patient specific quality assurance for pencil beam scanning IMPT fields.

    abstract:PURPOSE:A detailed analysis of 2728 intensity modulated proton therapy (IMPT) fields that were clinically delivered to patients between 2007 and 2013 at Paul Scherrer Institute (PSI) was performed. The aim of this study was to analyze the results of patient specific dosimetric verifications and to assess possible corre...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.4964449

    authors: Trnková P,Bolsi A,Albertini F,Weber DC,Lomax AJ

    更新日期:2016-11-01 00:00:00

  • Technical Note: Transconvolution based equalization of positron energy effects for the use of 68 Ge/68 Ga phantoms in determining 18 F PET recovery.

    abstract:PURPOSE:Avoiding measurement variability from 18 F phantom preparation by using 68 Ge/68 Ga phantoms for the determination of 18 F recovery curves (RC) in clinical quality assurance measurements and for PET/CT site qualification in multicentre clinical trials. METHODS:RCs were obtained from PET/CT measurements of seve...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1002/mp.12330

    authors: Prenosil GA,Hentschel M,Fürstner M,Krause T,Weitzel T,Klaeser B

    更新日期:2017-07-01 00:00:00

  • Partial volume segmentation of brain magnetic resonance images based on maximum a posteriori probability.

    abstract::Noise, partial volume (PV) effect, and image-intensity inhomogeneity render a challenging task for segmentation of brain magnetic resonance (MR) images. Most of the current MR image segmentation methods focus on only one or two of the above-mentioned effects. The objective of this paper is to propose a unified framewo...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.1944912

    authors: Li X,Li L,Lu H,Liang Z

    更新日期:2005-07-01 00:00:00

  • Unequal weighting of given doses in opposed fields in treatment of cancer of the tonsillar region using 60Co, 4-, 8-, 15-, 24-MVp photons.

    abstract::Weighting of given doses from parallel opposed fields is a widespread practice in radiation therapy of cancer in the tonsillar region. In order to determine when weighting is useful, dose distributions on the central axis were calculated for various energies (60Co, 4-, 8-, 15-, and MVp photons), weighting factors, and...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.594276

    authors: Wollin M,Gilbert HA,Kagan AR

    更新日期:1976-03-01 00:00:00

  • Some possible effects of a catheter on the arterial wall.

    abstract::When a catheter is inserted through an artery, the wall shear stress increases and the secondary flow exhibits an increased number of instantaneous vortices. These effects become more evident when the annular gap between the catheter and the artery becomes more narrow. Accordingly it is suggested that these factors ma...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.596448

    authors: Karahalios GT

    更新日期:1990-09-01 00:00:00

  • Practical cone-beam lambda tomography.

    abstract::As a potentially important technology for medical x-ray computed tomography (CT), lambda tomography (LT) is to reconstruct a gradient-like image only from local projection data. Based on our recently derived exact fan-beam LT formula, [H. Y. Gu and G. Wang, Int. J. Biomed. Imaging 2006(1), 1-9 (2006)] here we propose ...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.2348767

    authors: Yu H,Ye Y,Wang G

    更新日期:2006-10-01 00:00:00

  • Technical note: the calibration of 90Y-labeled SIR-Spheres using a nondestructive spectroscopic assay.

    abstract::90Y-labeled SIR-Spheres are currently used to treat patients with hepatic metastases secondary to colorectal adenocarcinoma. In general, the prescribed activity is based on empirical data collected during clinical trials. The activity of the source vial is labeled by the manufacturer as 3.0 GBq +/- 10% and is not inde...

    journal_title:Medical physics

    pub_type: 杂志文章

    doi:10.1118/1.2889621

    authors: Selwyn R,Micka J,DeWerd L,Nickles R,Thomadsen B

    更新日期:2008-04-01 00:00:00