Medical Physics

Development and evaluation of an ultrasound-guided tracking and gating system for hepatic radiotherapy

Ferenc Jacso, Alexei Kouznetsov, and Wendy L. Smith
Purpose: Respiratory motion must be accounted for daily in order to permit optimum radiotherapy of hepatic malignancies. However, existing tracking systems are often invasive or poorly tolerated by patients. The authors describe the development and validation of an ultrasound-guided tracking and ga ... [Med. Phys. 36, 5633 (2009)] published Wed Nov 18, 2009.

Simulation of large x-ray fields using independently measured source and geometry details

D. Sawkey and B. A. Faddegon
Purpose: Obtain an accurate simulation of the dose from the 6 and 18 MV x-ray beams from a Siemens Oncor linear accelerator by comparing simulation to measurement. Constrain the simulation by independently determining parameters of the treatment head and incident beam, in particular, the energy and ... [Med. Phys. 36, 5622 (2009)] published Tue Nov 17, 2009.

Computer-assisted extraction of intracranial aneurysms on 3D rotational angiograms for computational fluid dynamics modeling

Herng-Hua Chang, Gary R. Duckwiler, Daniel J. Valentino, and Woei Chyn Chu
Purpose: Three-dimensional rotational angiography (3DRA) is an evolving imaging procedure from traditional digital subtraction angiography and is gaining much interest for detecting intracranial aneurysms. Computational fluid dynamics (CFD) modeling plays an important role in understanding the biom ... [Med. Phys. 36, 5612 (2009)] published Fri Nov 13, 2009.

Influence of volumes of prostate, rectum, and bladder on treatment planning CT on interfraction prostate shifts during ultrasound image-guided IMRT

Nandanuri M. S. Reddy, Dattatreyudu Nori, William Sartin, Samuel Maiorano, Jennifer Modena et al.
Purpose: The purpose of this study was to analyze the relationship between prostate, bladder, and rectum volumes on treatment planning CT day and prostate shifts in the XYZ directions on treatment days. Methods: Prostate, seminal vesicles, bladder, and rectum were contoured on CT images obtained i ... [Med. Phys. 36, 5604 (2009)] published Wed Nov 11, 2009.

Registration of prone and supine CT colonography scans using correlation optimized warping and canonical correlation analysis

Shijun Wang, Jianhua Yao, Jiamin Liu, Nicholas Petrick, Robert L. Van Uitert et al.
Purpose: In computed tomographic colonography (CTC), a patient will be scanned twiceOnce supine and once proneto improve the sensitivity for polyp detection. To assist radiologists in CTC reading, in this paper we propose an automated method for colon registration from supine and prone CTC scans. ... [Med. Phys. 36, 5595 (2009)] published Wed Nov 11, 2009.

Optimizing non-Pb radiation shielding materials using bilayers

J. P. McCaffrey, E. Mainegra-Hing, and H. Shen
Purpose: The objective of this study was to demonstrate that the weight of non-Pb radiation shielding materials can be minimized by structuring the material as a bilayer composed of different metal-powder-embedded elastomer layers. Methods: Measurements and Monte Carlo (MC) calculations were perfo ... [Med. Phys. 36, 5586 (2009)] published Tue Nov 10, 2009.

Correcting magnetic resonance k-space data for in-plane motion using an optical position tracking system

M. Marxen, J. Marmurek, N. Baker, and S. J. Graham
Purpose: Motion is a major confound of image quality in MRI. A method of retrospectively correcting the effects of rotations and translations on the acquired k-space data is presented. Methods: In two phantom experiments of well-controlled translation and rotation, two MRI-compatible infrared came ... [Med. Phys. 36, 5580 (2009)] published Mon Nov 9, 2009.

Coronary centerline extraction from CT coronary angiography images using a minimum cost path approach

C. T. Metz, M. Schaap, A. C. Weustink, N. R. Mollet, T. van Walsum et al.
Purpose: The application and large-scale evaluation of minimum cost path approaches for coronary centerline extraction from computed tomography coronary angiography (CTCA) data and the development and evaluation of a novel method to reduce the user-interaction time. Methods: A semiautomatic method ... [Med. Phys. 36, 5568 (2009)] published Mon Nov 9, 2009.

Energy dependence of EBT-1 radiochromic film response for photon (10 kVp15 MVp) and electron beams (618 MeV) readout by a flatbed scanner

Christian Richter, Jorg Pawelke, Leonhard Karsch, and Julia Woithe
Purpose: The aim of this article is to investigate the energy dependence of the radiochromic film type, Gafchromic EBT-1, when scanned with a flatbed scanner for film readout. Methods: Dose response curves were determined for 12 different beam qualities ranging from a 10 kVp x-ray beam to a 15 M ... [Med. Phys. 36, 5506 (2009)] published Fri Nov 6, 2009.

Number of partitions (gates) needed to obtain motion-free images in a respiratory gated 4D-PET/CT study as a function of the lesion size and motion displacement

V. Bettinardi, E. Rapisarda, and M. C. Gilardi
Purpose: In this study we evaluate the number of data partitions (gates) needed to sort 4D-PET and 4D-CT data to obtain motion-free images as a function of lesion size and motion displacement. Methods: Plexiglas spheres of various diameters (8, 10, 15, 20, and 25 mm) were filled with a radioactive ... [Med. Phys. 36, 5547 (2009)] published Fri Nov 6, 2009.

Patient geometry-driven information retrieval for IMRT treatment plan quality control

Binbin Wu, Francesco Ricchetti, Giuseppe Sanguineti, Misha Kazhdan, Patricio Simari et al.
Purpose: Intensity modulated radiation therapy (IMRT) treatment plan quality depends on the planner's level of experience and the amount of time the planner invests in developing the plan. Planners often unwittingly accept plans when further sparing of the organs at risk (OARs) is possible. The aut ... [Med. Phys. 36, 5497 (2009)] published Fri Nov 6, 2009.

Development of prototype shielded cervical intracavitary brachytherapy applicators compatible with CT and MR imaging

Michael J. Price, Edward F. Jackson, Kent A. Gifford, Patricia J. Eifel, and Firas Mourtada
Purpose: Intracavitary brachytherapy (ICBT) is an integral part of the treatment regimen for cervical cancer and, generally, outcome in terms of local disease control and complications is a function of dose to the disease bed and critical structures, respectively. Therefore, it is paramount to accu ... [Med. Phys. 36, 5515 (2009)] published Fri Nov 6, 2009.

Single x-ray absorptiometry method for the quantitative mammographic measure of fibroglandular tissue volume

Serghei Malkov, Jeff Wang, Karla Kerlikowske, Steven R. Cummings, and John A. Shepherd
Purpose: This study describes the design and characteristics of a highly accurate, precise, and automated single-energy method to quantify percent fibroglandular tissue volume (%FGV) and fibroglandular tissue volume (FGV) using digital screening mammography. Methods: The method uses a breast tissu ... [Med. Phys. 36, 5525 (2009)] published Fri Nov 6, 2009.

An EPID based method for efficient and precise asymmetric jaw alignment quality assurance

Luke Clews and Peter B. Greer
Purpose: The aim of this work was to investigate the use of amorphous silicon electronic portal imaging devices (EPIDs) for regular quality assurance of linear accelerator asymmetric jaw junctioning. Methods: The method uses the beam central axis position on the EPID measured to subpixel accuracy ... [Med. Phys. 36, 5488 (2009)] published Fri Nov 6, 2009.

Singular value decomposition based computationally efficient algorithm for rapid dynamic near-infrared diffuse optical tomography

Saurabh Gupta, Phaneendra K. Yalavarthy, Debasish Roy, Daqing Piao, and Ram M. Vasu
Purpose: A computationally efficient algorithm (linear iterative type) based on singular value decomposition (SVD) of the Jacobian has been developed that can be used in rapid dynamic near-infrared (NIR) diffuse optical tomography. Methods: Numerical and experimental studies have been conducted to ... [Med. Phys. 36, 5559 (2009)] published Fri Nov 6, 2009.

Trial of a proposed protocol for constancy control of digital mammography systems

Kristin Pedersen and Ingrid Dypvik Landmark
Purpose: Evaluate the utility of tests in a proposed protocol for constancy control of digital mammography systems. Methods: The protocol contained tests for image acquisition, mechanical function and safety, monitors and printers, and viewing conditions. Nine sites with digital systems from four ... [Med. Phys. 36, 5537 (2009)] published Fri Nov 6, 2009.

A Monte Carlo estimation of effective dose in chest tomosynthesis

John M. Sabol
Purpose: The recent introduction of digital tomosynthesis imaging into routine clinical use has enabled the acquisition of volumetric patient data within a standard radiographic examination. Tomosynthesis requires the acquisition of multiple projection views, requiring additional dose compared to a ... [Med. Phys. 36, 5480 (2009)] published Fri Nov 6, 2009.

The myth of the 50-50 breast

M. J. Yaffe, J. M. Boone, N. Packard, O. Alonzo-Proulx, S.-Y. Huang et al.
Purpose: For dosimetry and for work in optimization of x-ray imaging of the breast, it is commonly assumed that the breast is composed of 50% fibroglandular tissue and 50% fat. The purpose of this study was to assess whether this assumption was realistic. Methods: First, data obtained from an expe ... [Med. Phys. 36, 5437 (2009)] published Thu Nov 5, 2009.

Evaluation of similarity measures for use in the intensity-based rigid 2D-3D registration for patient positioning in radiotherapy

Jian Wu, Minho Kim, Jorg Peters, Heeteak Chung, and Sanjiv S. Samant
Purpose: Rigid 2D-3D registration is an alternative to 3D-3D registration for cases where largely bony anatomy can be used for patient positioning in external beam radiation therapy. In this article, the authors evaluated seven similarity measures for use in the intensity-based rigid 2D-3D registra ... [Med. Phys. 36, 5391 (2009)] published Thu Nov 5, 2009.

Tissue equivalency of phantom materials for neutron dosimetry in proton therapy

Stephen Dowdell, Ben Clasie, Andrew Wroe, Susanna Guatelli, Peter Metcalfe et al.
Purpose: Previous Monte Carlo and experimental studies involving secondary neutrons in proton therapy have employed a number of phantom materials that are designed to represent human tissue. In this study, the authors determined the suitability of common phantom materials for dosimetry of secondary ... [Med. Phys. 36, 5412 (2009)] published Thu Nov 5, 2009.

Geometric feature-based multimodal image registration of contrast-enhanced cardiac CT with gated myocardial perfusion SPECT

Jonghye Woo, Piotr J. Slomka, Damini Dey, Victor Y. Cheng, Byung-Woo Hong et al.
Purpose: Cardiac computed tomography (CT) and single photon emission computed tomography (SPECT) provide clinically complementary information in the diagnosis of coronary artery disease (CAD). Fused anatomical and physiological data acquired sequentially on separate scanners can be coregistered to ... [Med. Phys. 36, 5467 (2009)] published Thu Nov 5, 2009.

An integral quality monitoring system for real-time verification of intensity modulated radiation therapy

Mohammad K. Islam, Bernhard D. Norrlinger, Jason R. Smale, Robert K. Heaton, Duncan Galbraith et al.
Purpose: To develop an independent and on-line beam monitoring system, which can validate the accuracy of segment-by-segment energy fluence delivery for each treatment field. The system is also intended to be utilized for pretreatment dosimetric quality assurance of intensity modulated radiation th ... [Med. Phys. 36, 5420 (2009)] published Thu Nov 5, 2009.

Cumulative sum quality control for calibrated breast density measurements

John J. Heine, Ke Cao, and Craig Beam
Purpose: Breast density is a significant breast cancer risk factor. Although various methods are used to estimate breast density, there is no standard measurement for this important factor. The authors are developing a breast density standardization method for use in full field digital mammography ... [Med. Phys. 36, 5380 (2009)] published Thu Nov 5, 2009.

Design and construction of a quality control phantom for SPECT and PET imaging

Dylan Christopher Hunt, Harry Easton, and Curtis B. Caldwell
In this article, the authors present a method for quickly and easily constructing test phantoms for PET and SPECT quality assurance. As a demonstration, they constructed a complex prototype test phantom, showing the strengths of the construction method. Images taken using a PET/CT and a SPECT scann ... [Med. Phys. 36, 5404 (2009)] published Thu Nov 5, 2009.

Fast, accurate photon beam accelerator modeling using BEAMnrc: A systematic investigation of efficiency enhancing methods and cross-section data

Margarida Fragoso, Iwan Kawrakow, Bruce A. Faddegon, Timothy D. Solberg, and Indrin J. Chetty
In this work, an investigation of efficiency enhancing methods and cross-section data in the BEAMnrc Monte Carlo (MC) code system is presented. Additionally, BEAMnrc was compared with VMC++, another special-purpose MC code system that has recently been enhanced for the simulation of the entire trea ... [Med. Phys. 36, 5451 (2009)] published Thu Nov 5, 2009.

Functional representation of tissue phantom ratios for photon fields

Otto A. Sauer and J. Wilbert
Purpose: The tissue phantom ratio (TPR) is a common dosimetric quantity used in photon dose calculations. For small photon fields with side lengths less than 4 cm, TPR data hardly exist in literature. In this work, a self-contained functional representation of TPR is proposed, valid for the whole ... [Med. Phys. 36, 5444 (2009)] published Thu Nov 5, 2009.

Identification of breast calcification using magnetic resonance imaging

Ali Fatemi-Ardekani, Colm Boylan, and Michael D. Noseworthy
MRI phase and magnitude images provide information about local magnetic field variation (DeltaB), which can consequently be used to understand tissue properties. Often, phase information is discarded. However, corrected phase images are able to produce contrast as a result of magnetic susceptibilit ... [Med. Phys. 36, 5429 (2009)] published Thu Nov 5, 2009.

Radiation departments should be certified to provide certain new technologies such as IGRT

Christopher F. Njeh, Abdul Rashid, and Colin G. Orton
Abstract not available. [Med. Phys. 36, 5377 (2009)] published Thu Nov 5, 2009.

Medical Imaging Principles, Detectors, and Electronics

Krysztof Iniewski and William Davros
Abstract not available. [Med. Phys. 36, 5374 (2009)] published Tue Oct 27, 2009.

IMRT commissioning: Multiple institution planning and dosimetry comparisons, a report from AAPM Task Group 119

Gary A. Ezzell, Jay W. Burmeister, Nesrin Dogan, Thomas J. LoSasso, James G. Mechalakos et al.
AAPM Task Group 119 has produced quantitative confidence limits as baseline expectation values for IMRT commissioning. A set of test cases was developed to assess the overall accuracy of planning and delivery of IMRT treatments. Each test uses contours of targets and avoidance structures drawn with ... [Med. Phys. 36, 5359 (2009)] published Tue Oct 27, 2009.

Ionizing Radiation Exposure of the Population of the United States

Dean Broga
Abstract not available. [Med. Phys. 36, 5375 (2009)] published Tue Oct 27, 2009.

Quantitative blood flow measurements in the small animal cardiopulmonary system using digital subtraction angiography

MingDe Lin, Craig T. Marshall, Yi Qi, Samuel M. Johnston, Cristian T. Badea et al.
Purpose: The use of preclinical rodent models of disease continues to grow because these models help elucidate pathogenic mechanisms and provide robust test beds for drug development. Among the major anatomic and physiologic indicators of disease progression and genetic or drug modification of resp ... [Med. Phys. 36, 5347 (2009)] published Tue Oct 27, 2009.

Initial investigation on the use of MR spectroscopy and micro-MRI of GAFCHROMIC EBT radiotherapy film

Rick Holly, Brian M. Keller, Jean-Philippe Pignol, Claude Lemaire, and Hartwig Peemoeller
Purpose: This article presents an initial investigation of the efficacy of using H MRS and micro-MRI as analysis techniques for irradiated GAFCHROMIC EBT radiotherapy films. Methods: GAFCHROMIC EBT radiotherapy film was irradiated with 6 MV x rays to known doses ranging from 5 to 1000 cGy. 24 h fo ... [Med. Phys. 36, 5341 (2009)] published Mon Oct 26, 2009.

More than 10 years experience of beam monitoring with the Gantry 1 spot scanning proton therapy facility at PSI

Shixiong Lin, Terence Boehringer, Adolf Coray, Martin Grossmann, and Eros Pedroni
Purpose: The beam monitoring equipments developed for the first PSI spot scanning proton therapy facility, Gantry 1, have been successfully used for more than 10 years. The purpose of this article is to summarize the author's experience in the beam monitoring technique for dynamic proton scanning. ... [Med. Phys. 36, 5331 (2009)] published Fri Oct 23, 2009.

Image-based iterative compensation of motion artifacts in computed tomography

Colas Schretter, Georg Rose, and Matthias Bertram
Purpose: This article presents an iterative method for compensation of motion artifacts for slowly rotating computed tomography (CT) systems. Patient's motion introduces inconsistencies among projections and yields severe reconstruction artifacts for free-breathing acquisitions. Streaks and doublin ... [Med. Phys. 36, 5323 (2009)] published Thu Oct 22, 2009.