Medical Physics

Evaluation of an a-Si EPID in direct detection configuration as a water-equivalent dosimeter for transit dosimetry

Mahsheed Sabet, Frederick W. Menk, and Peter B. Greer
Purpose: A major problem associated with amorphous silicon (a-Si) electronic portal imaging devices (EPIDs) for transit dosimetry is the presence of a phosphor layer, which can introduce large deviations from water-equivalent behavior due to energy-dependent response and visible light scattering. I ... [Med. Phys. 37, 1459 (2010)] published Wed Mar 10, 2010.

A conceptual design of rotating board technique for delivering total skin electron therapy

Jia-Ming Wu, Shyh-An Yeh, Kuan-Yin Hsiao, Max Min Chao, and Ishiuan Hargrove
Purpose: This study presents a novel technique in which a uniform radiation dose to the whole body, soles, and scalp vertex can be achieved in one electron beam treatment fraction. Methods: The patient was treated at a machine with a home-made rotating board. The patients were treated in two group ... [Med. Phys. 37, 1449 (2010)] published Wed Mar 10, 2010.

Increasing computer-aided detection specificity by projection features for CT colonography

Hongbin Zhu, Zhengrong Liang, Perry J. Pickhardt, Matthew A. Barish, Jiangsheng You et al.
Purpose: A large number of false positives (FPs) generated by computer-aided detection (CAD) schemes is likely to distract radiologists' attention and decrease their interpretation efficiency. This study aims to develop projection-based features which characterize true and false positives to increa ... [Med. Phys. 37, 1468 (2010)] published Wed Mar 10, 2010.

Tissue-mimicking bladder wall phantoms for evaluating acoustic radiation forceoptical coherence elastography systems

O'tega A. Ejofodomi, Vesna Zderic, and Jason M. Zara
Purpose: Acoustic radiation forceoptical coherence elastography (ARF-OCE) systems are novel imaging systems that have the potential to simultaneously quantify and characterize the optical and mechanical properties of in vivo tissues. This article presents the construction of bladder wall phantoms f ... [Med. Phys. 37, 1440 (2010)] published Wed Mar 10, 2010.

Establishment of technical prerequisites for cell irradiation experiments with laser-accelerated electrons

E. Beyreuther, W. Enghardt, M. Kaluza, L. Karsch, L. Laschinsky et al.
Purpose: In recent years, laser-based acceleration of charged particles has rapidly progressed and medical applications, e.g., in radiotherapy, might become feasible in the coming decade. Requirements are monoenergetic particle beams with long-term stable and reproducible properties as well as suff ... [Med. Phys. 37, 1392 (2010)] published Tue Mar 9, 2010.

Design and performance of a respiratory amplitude gating device for PET/CT imaging

Guoping Chang, Tingting Chang, John W. Clark, Jr., and Osama R. Mawlawi
Purpose: Recently, the authors proposed a free-breathing amplitude gating (FBAG) technique for PET/CT scanners. The implementation of this technique required specialized hardware and software components that were specifically designed to interface with commercial respiratory gating devices to gener ... [Med. Phys. 37, 1408 (2010)] published Tue Mar 9, 2010.

Direct tumor in vivo dosimetry in highly-conformal radiotherapy: A feasibility study of implantable MOSFETs for hypofractionated extracranial treatments using the Cyberknife system

Paolo Scalchi, Roberto Righetto, Carlo Cavedon, Paolo Francescon, and Federico Colombo
Purpose: In highly-conformal radiotherapy, due to the complexity of both beam configurations and dose distributions, traditional in vivo dosimetry is unpractical or even impossible. The ideal dosimeter would be implanted inside the planning treatment volume so that it can directly measure the total ... [Med. Phys. 37, 1413 (2010)] published Tue Mar 9, 2010.

Texture analysis of carotid artery atherosclerosis from three-dimensional ultrasound images

Joseph Awad, Adam Krasinski, Grace Parraga, and Aaron Fenster
Purpose: To quantitatively evaluate local carotid arterial statin effects in 3D US images using multiclassifier image texture analysis tools. Methods: Texture analysis tools were used to evaluate the effect of 80 mg atorvastatin administered daily to patients with carotid stenosis compared to thos ... [Med. Phys. 37, 1382 (2010)] published Tue Mar 9, 2010.

Comparison of Bayesian network and support vector machine models for two-year survival prediction in lung cancer patients treated with radiotherapy

K. Jayasurya, G. Fung, S. Yu, C. Dehing-Oberije, D. De Ruysscher et al.
Purpose: Classic statistical and machine learning models such as support vector machines (SVMs) can be used to predict cancer outcome, but often only perform well if all the input variables are known, which is unlikely in the medical domain. Bayesian network (BN) models have a natural ability to re ... [Med. Phys. 37, 1401 (2010)] published Tue Mar 9, 2010.

Statistical shape model-based reconstruction of a scaled, patient-specific surface model of the pelvis from a single standard AP x-ray radiograph

Guoyan Zheng
Purpose: The aim of this article is to investigate the feasibility of using a statistical shape model (SSM)-based reconstruction technique to derive a scaled, patient-specific surface model of the pelvis from a single standard anteroposterior (AP) x-ray radiograph and the feasibility of estimating ... [Med. Phys. 37, 1424 (2010)] published Tue Mar 9, 2010.

Radiotherapy physicists have become glorified technicians rather than clinical scientists

Howard I. Amols, Frank Van den Heuvel, and Colin G. Orton
Abstract not available. [Med. Phys. 37, 1379 (2010)] published Tue Mar 9, 2010.

Comparison of Elekta VMAT with helical tomotherapy and fixed field IMRT: Plan quality, delivery efficiency and accuracy

Min Rao, Wensha Yang, Fan Chen, Ke Sheng, Jinsong Ye et al.
Purpose: Helical tomotherapy (HT) and volumetric modulated arc therapy (VMAT) are arc-based approaches to IMRT delivery. The objective of this study is to compare VMAT to both HT and fixed field IMRT in terms of plan quality, delivery efficiency, and accuracy. Methods: Eighteen cases including six ... [Med. Phys. 37, 1350 (2010)] published Mon Mar 1, 2010.

The Physics of Radiation Therapy

Faiz M. Khan and Sotirios Stathakis
Abstract not available. [Med. Phys. 37, 1374 (2010)] published Mon Mar 1, 2010.

Technical Note: EGSnrc-based dosimetric study of the BEBIG Co HDR brachytherapy sources

T. Palani Selvam and Subhalaxmi Bhola
Purpose: The purpose of this work is to calculate two-dimensional (2D) dose rate distributions around the BEBIG (Eckert & Ziegler, BEBIG GmbH, Germany) models GK60M21 (old) and Co0.A86 (new) Co high dose rate brachytherapy sources in an unbounded liquid water phantom. The study includes calculation ... [Med. Phys. 37, 1365 (2010)] published Mon Mar 1, 2010.

Mentoring future Medical Physics reviewers

William Hendee
Abstract not available. [Med. Phys. 37, 1371 (2010)] published Mon Mar 1, 2010.

Effect of repeated x-ray exposure on the resolution of amorphous selenium based x-ray imagers

M. Z. Kabir, L. Chowdhury, G. DeCrescenzo, O. Tousignant, S. O. Kasap et al.
Purpose: A numerical model and the experimental methods to study the x-ray exposure dependent change in the modulation transfer function (MTF) of amorphous selenium (a-Se) based active matrix flat panel imagers (AMFPIs) are described. The physical mechanisms responsible for the x-ray exposure depen ... [Med. Phys. 37, 1339 (2010)] published Mon Mar 1, 2010.

Application of the continuity equation to a breathing motion model

Daniel A. Low, Tianyu Zhao, Benjamin White, Deshan Yang, Sasa Mutic et al.
Purpose: To quantitatively test a breathing motion model using the continuity equation and clinical data. Methods: The continuity equation was applied to a lung tissue and lung tumor free breathing motion model to quantitatively test the model performance. The model used tidal volume and airflow a ... [Med. Phys. 37, 1360 (2010)] published Mon Mar 1, 2010.

Scholarly publishing: A tale of two worlds

John Haynes
Abstract not available. [Med. Phys. 37, 1372 (2010)] published Mon Mar 1, 2010.

Medical applications of shortwave FM radar: Remote monitoring of cardiac and respiratory motion

K. Mostov, E. Liptsen, and R. Boutchko
Purpose: This article introduces the use of low power continuous wave frequency modulated radar for medical applications, specifically for remote monitoring of vital signs in patients. Methods: Gigahertz frequency radar measures the electromagnetic wave signal reflected from the surface of a human ... [Med. Phys. 37, 1332 (2010)] published Mon Mar 1, 2010.

A 3D global-to-local deformable mesh model based registration and anatomy-constrained segmentation method for image guided prostate radiotherapy

Jinghao Zhou, Sung Kim, Salma Jabbour, Sharad Goyal, Bruce Haffty et al.
Purpose: In the external beam radiation treatment of prostate cancers, successful implementation of adaptive radiotherapy and conformal radiation dose delivery is highly dependent on precise and expeditious segmentation and registration of the prostate volume between the simulation and the treatmen ... [Med. Phys. 37, 1298 (2010)] published Thu Feb 25, 2010.

Verification of source and collimator configuration for Gamma Knife Perfexion using panoramic imaging

Young-Bin Cho, Monique van Prooijen, David A. Jaffray, and Mohammad K. Islam
Purpose: The new model of stereotactic radiosurgery system, Gamma Knife Perfexion, allows automatic selection of built-in collimation, eliminating the need for the time consuming manual collimator installation required with previous models. However, the configuration of sources and collimators insi ... [Med. Phys. 37, 1325 (2010)] published Thu Feb 25, 2010.

Effective learning strategies for real-time image-guided adaptive control of multiple-source hyperthermia applicators

Kung-Shan Cheng, Mark W. Dewhirst, Paul R. Stauffer, and Shiva Das
Purpose: This paper investigates overall theoretical requirements for reducing the times required for the iterative learning of a real-time image-guided adaptive control routine for multiple-source heat applicators, as used in hyperthermia and thermal ablative therapy for cancer. Methods: Methods ... [Med. Phys. 37, 1285 (2010)] published Thu Feb 25, 2010.

A novel fuzzy C-means algorithm for unsupervised heterogeneous tumor quantification in PET

Saoussen Belhassen and Habib Zaidi
Purpose: Accurate and robust image segmentation was identified as one of the most challenging issues facing PET quantification in oncological imaging. This difficulty is compounded by the low spatial resolution and high noise characteristics of PET images. The fuzzy C-means (FCM) clustering algorit ... [Med. Phys. 37, 1309 (2010)] published Thu Feb 25, 2010.

A volumetric model-based 2D to 3D registration method for measuring kinematics of natural knees with single-plane fluoroscopy

Tsung-Yuan Tsai, Tung-Wu Lu, Chung-Ming Chen, Mei-Ying Kuo, and Horng-Chaung Hsu
Purpose: Accurate measurement of the three-dimensional (3D) rigid body and surface kinematics of the natural human knee is essential for many clinical applications. Existing techniques are limited either in their accuracy or lack more realistic experimental evaluation of the measurement errors. The ... [Med. Phys. 37, 1273 (2010)] published Thu Feb 25, 2010.

4DCT-based measurement of changes in pulmonary function following a course of radiation therapy

Kai Ding, John E. Bayouth, John M. Buatti, Gary E. Christensen, and Joseph M. Reinhardt
Purpose: Radiation therapy (RT) for lung cancer is commonly limited to subtherapeutic doses due to unintended toxicity to normal lung tissue. Reducing the frequency of occurrence and magnitude of normal lung function loss may benefit from treatment plans that incorporate the regional lung and radia ... [Med. Phys. 37, 1261 (2010)] published Wed Feb 24, 2010.

Variations in tumor size and position due to irregular breathing in 4D-CT: A simulation study

Joyatee Sarker, Alan Chu, Kit Mui, John A. Wolfgang, Ariel E. Hirsch et al.
Purpose: To estimate the position and volume errors in 4D-CT caused by irregular breathing. Methods: A virtual 4D-CT scanner was designed to reproduce axial mode scans with retrospective resorting. This virtual scanner creates an artificial spherical tumor based on the specifications of the user, ... [Med. Phys. 37, 1254 (2010)] published Wed Feb 24, 2010.

A diamond target for megavoltage cone-beam CT

D. Sawkey, M. Lu, O. Morin, M. Aubin, S. S. Yom et al.
Purpose: To determine the properties of a megavoltage cone-beam CT system using the unflattened beam from a sintered diamond target at 4 and 6 MV. Methods: A sintered diamond target was used in place of a graphite target as part of an imaging beam line (an unflattened beam from a graphite target) ... [Med. Phys. 37, 1246 (2010)] published Wed Feb 24, 2010.

Evaluation of respiration-correlated digital tomosynthesis in lung

Joseph Santoro, Sergey Kriminski, D. Michael Lovelock, Kenneth Rosenzweig, Hassan Mostafavi et al.
Digital tomosynthesis (DTS) with a linear accelerator-mounted imaging system provides a means of reconstructing tomographic images from radiographic projections over a limited gantry arc, thus requiring only a few seconds to acquire. Its application in the thorax, however, often results in blurred ... [Med. Phys. 37, 1237 (2010)] published Tue Feb 23, 2010.

Radiation dose reduction using a CdZnTe-based computed tomography system: Comparison to flat-panel detectors

Huy Q. Le, Justin L. Ducote, and Sabee Molloi
Purpose: Although x-ray projection mammography has been very effective in early detection of breast cancer, its utility is reduced in the detection of small lesions that are occult or in dense breasts. One drawback is that the inherent superposition of parenchymal structures makes visualization of ... [Med. Phys. 37, 1225 (2010)] published Mon Feb 22, 2010.

Analysis of dose to patient, spouse/caretaker, and staff, from an implanted trackable radioactive fiducial for use in the radiation treatment of prostate cancer

David Neustadter, Gideon Barnea, Saul Stokar, and Ben Corn
Purpose: A fiducial tracking system based on a novel radioactive tracking technology is being developed for real-time target tracking in radiation therapy. In this study, the authors calculate the radiation dose to the patient, the spouse/caretaker, and the medical staff that would result from a 10 ... [Med. Phys. 37, 1220 (2010)] published Mon Feb 22, 2010.

Attenuation-emission alignment in cardiac PET/CT based on consistency conditions

Adam M. Alessio, Paul E. Kinahan, Kyle M. Champley, and James H. Caldwell
Purpose: In cardiac PET and PET/CT imaging, misaligned transmission and emission images are a common problem due to respiratory and cardiac motion. This misalignment leads to erroneous attenuation correction and can cause errors in perfusion mapping and quantification. This study develops and tests ... [Med. Phys. 37, 1191 (2010)] published Fri Feb 19, 2010.

Intensity modulated proton therapy treatment planning using single-field optimization: The impact of monitor unit constraints on plan quality

X. R. Zhu, N. Sahoo, X. Zhang, D. Robertson, H. Li et al.
Purpose: To investigate the effect of monitor unit (MU) constraints on the dose distribution created by intensity modulated proton therapy (IMPT) treatment planning using single-field optimization (SFO). Methods: Ninety-four energies between 72.5 and 221.8 MeV are available for scanning beam IMPT ... [Med. Phys. 37, 1210 (2010)] published Fri Feb 19, 2010.

Accurate brain volumetry with diffusion-weighted spin-echo single-shot echo-planar-imaging and dual-clustering segmentation: Comparison with volumetry-validated quantitative magnetic resonance imaging

Memi Watanabe, Osamu Sakai, Alexander M. Norbash, and Hernan Jara
Purpose: Although the diffusion-weighted spin-echo single-shot echo-planar-imaging (DW-SE-sshEPI) is an established quantitative MRI (qMRI) pulse sequence, it is known to be vulnerable to geometric distortions. The purpose of this work is to study is to study brain volumetry accuracy with DW-SE-ssh ... [Med. Phys. 37, 1183 (2010)] published Fri Feb 19, 2010.

Backprojection-filtration reconstruction without invoking a spatially varying weighting factor

Dan Xia, Seungryong Cho, and Xiaochuan Pan
Purpose: To develop a backprojection-filtration (BPF) algorithm with improved noise properties over the existing BPF algorithm through utilizing (approximate) redundant information in circular cone-beam or fan-beam scans. Methods: The backprojection steps in the existing filtered-backprojection (F ... [Med. Phys. 37, 1201 (2010)] published Fri Feb 19, 2010.

Evaluation of the spatial dependence of the point spread function in 2D PET image reconstruction using LOR-OSEM

D. Wiant, J. A. Gersh, M. Bennett, and J. D. Bourland
Purpose: The use of positron emission tomography (PET) imaging has proved beneficial in the staging and diagnosis of several cancer disease sites. Additional applications of PET imaging in treatment planning and the evaluation of treatment response are limited by the relatively low spatial resoluti ... [Med. Phys. 37, 1169 (2010)] published Fri Feb 19, 2010.

Monte Carlo characterization of a new Yb-169 high dose rate source for brachytherapy application

Mario J. Cazeca, David C. Medich, and John J. Munro, III
Purpose: The objective was to characterize a new Yb-169 high dose rate source for brachytherapy application. Methods: Monte Carlo simulations were performed using the MCNP5 F6 energy deposition tallies placed around the Yb-169 source at different radial distances in both air-vacuum and water envir ... [Med. Phys. 37, 1129 (2010)] published Thu Feb 18, 2010.

Prediction of stopping-power ratios in flattening-filter free beams

Crister Ceberg, Stefan Johnsson, Marten Lind, and Tommy Knoos
Purpose: In recent years, there has been an increasing interest in flattening-filter free (FFF) beams. However, since the removal of the flattening filter will affect both the mean and the variance of the energy spectrum, current beam-quality specifiers may not be adequate for reference dosimetry i ... [Med. Phys. 37, 1164 (2010)] published Thu Feb 18, 2010.

Evaluation of delivered monitor unit accuracy of gated step-and-shoot IMRT using a two-dimensional detector array

Kwang-Ho Cheong, Sei-Kwon Kang, MeYeon Lee, Su SSan Kim, SoAh Park et al.
Purpose: To overcome the problem of organ motion in intensity-modulated radiation therapy (IMRT), gated IMRT is often used for the treatment of lung cancer. In this study, the authors investigated the accuracy of the delivered monitor units (MUs) from each segment during gated IMRT using a two-dime ... [Med. Phys. 37, 1146 (2010)] published Thu Feb 18, 2010.

Individualized computer-aided education in mammography based on user modeling: Concept and preliminary experiments

Maciej A. Mazurowski, Jay A. Baker, Huiman X. Barnhart, and Georgia D. Tourassi
Purpose: The authors propose the framework for an individualized adaptive computer-aided educational system in mammography that is based on user modeling. The underlying hypothesis is that user models can be developed to capture the individual error making patterns of radiologists-in-training. In t ... [Med. Phys. 37, 1152 (2010)] published Thu Feb 18, 2010.

A pseudoinverse deformation vector field generator and its applications

C. Yan, H. Zhong, M. Murphy, E. Weiss, and J. V. Siebers
Purpose: To present, implement, and test a self-consistent pseudoinverse displacement vector field (PIDVF) generator, which preserves the location of information mapped back-and-forth between image sets. Methods: The algorithm is an iterative scheme based on nearest neighbor interpolation and a su ... [Med. Phys. 37, 1117 (2010)] published Thu Feb 18, 2010.

Three-dimensional quantitative evaluation method of nonrigid registration algorithms for adaptive radiotherapy

B. Rodriguez-Vila, F. Gaya, F. Garcia-Vicente, and E. J. Gomez
Purpose: Current radiotherapy is progressing to the concept of adaptive radiotherapy, which implies the adaptation of planning along the treatment course. Nonrigid registration is an essential image processing tool for adaptive radiotherapy and image guided radiotherapy, and the three-dimensional ( ... [Med. Phys. 37, 1137 (2010)] published Thu Feb 18, 2010.

Zero-shift thimble ionization chamber

Frederic Tessier, Brian D. Hooten, and Malcolm R. McEwen
Purpose: Verify experimentally the theoretical prediction of F. Tessier and I. Kawrakow [Med. Phys. 37, 96107 (2010)] that it is possible to design a thimble ionization chamber with no shift in its effective point of measurement (EPOM), i.e., a chamber that provides a measure of the dose to the med ... [Med. Phys. 37, 1161 (2010)] published Thu Feb 18, 2010.

Monte Carlo calculated absorbed-dose energy dependence of EBT and EBT2 film

J. G. H. Sutherland and D. W. O. Rogers
Purpose: The absorbed-dose energy dependence of GAFCHROMIC EBT and EBT2 film irradiated in photon beams is studied to understand the shape of the curves and the physics behind them. Methods: The absorbed-dose energy dependence is calculated using the EGSnrc-based EGS_chamber and DOSRZnrc codes by ... [Med. Phys. 37, 1110 (2010)] published Thu Feb 18, 2010.

Fully automatic nonrigid registration-based local motion estimation for motion-corrected iterative cardiac CT reconstruction

Alfonso A. Isola, Michael Grass, and Wiro J. Niessen
Purpose: Cardiac computed tomography is a rapidly emerging technique for noninvasive diagnosis of cardiovascular diseases. Nevertheless, the cardiac motion continues to be a limiting factor. Electrocardiogram-gated cardiac computed tomography reconstruction methods yield excellent results, but thes ... [Med. Phys. 37, 1093 (2010)] published Tue Feb 16, 2010.

Reference radiochromic film dosimetry in kilovoltage photon beams during CBCT image acquisition

Nada Tomic, Slobodan Devic, Francois DeBlois, and Jan Seuntjens
Purpose: A common approach for dose assessment during cone beam computed tomography (CBCT) acquisition is to use thermoluminescent detectors for skin dose measurements (on patients or phantoms) or ionization chamber (in phantoms) for body dose measurements. However, the benefits of a daily CBCT ima ... [Med. Phys. 37, 1083 (2010)] published Tue Feb 16, 2010.

Electrode displacement strain imaging of thermally-ablated liver tissue in an in vivo animal model

N. Rubert, S. Bharat, R. J. DeWall, A. Andreano, C. Brace et al.
Purpose: Percutaneous thermal ablation is increasingly being used to destroy hepatic tumors in situ. The success of ablative techniques is highly dependent on adequate ablation zone monitoring, and ultrasound-based strain imaging could become a convenient and cost-effective means to delineate ablat ... [Med. Phys. 37, 1075 (2010)] published Tue Feb 16, 2010.

Dose convolution filter: Incorporating spatial dose information into tissue response modeling

Yimei Huang, Michael Joiner, Bo Zhao, Yixiang Liao, and Jay Burmeister
Purpose: A model is introduced to integrate biological factors such as cell migration and bystander effects into physical dose distributions, and to incorporate spatial dose information in plan analysis and optimization. Methods: The model consists of a dose convolution filter (DCF) with single pa ... [Med. Phys. 37, 1068 (2010)] published Thu Feb 11, 2010.

CT energy weighting in the presence of scatter and limited energy resolution

Taly Gilat Schmidt
Purpose: Energy-resolved CT has the potential to improve the contrast-to-noise ratio (CNR) through optimal weighting of photons detected in energy bins. In general, optimal weighting gives higher weight to the lower energy photons that contain the most contrast information. However, low-energy phot ... [Med. Phys. 37, 1056 (2010)] published Tue Feb 9, 2010.

Advanced statistical techniques applied to comprehensive FTIR spectra on human colonic tissues

A. Zwielly, S. Mordechai, I. Sinielnikov, A. Salman, E. Bogomolny et al.
Purpose: Colon cancer is a major public health problem due to its high disease rate and death toll worldwide. The use of FTIR microscopy in the field of cancer diagnosis has become attractive over the past 20 years. In the present study, the authors investigated the potential of FTIR microscopy to ... [Med. Phys. 37, 1047 (2010)] published Tue Feb 9, 2010.

Ultrasound B-scan image simulation, segmentation, and analysis of the equine tendon

Ali Meghoufel, Guy Cloutier, Nathalie Crevier-Denoix, and Jacques A. de Guise
Purpose: The hypothesis is that an imaging technique based on decompression and segmentation of B-scan images with morphological operators can provide a measurement of the integrity of equine tendons. Methods: Two complementary approaches were used: (i) Simulation of B-scan images to better unders ... [Med. Phys. 37, 1038 (2010)] published Tue Feb 9, 2010.