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Medical Physics

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https://www.readbyqxmd.com/read/28437565/relaxed-ordered-subset-preconditioned-alternating-projection-algorithm-for-pet-reconstruction-with-automated-penalty-weight-selection
#1
C Ross Schmidtlein, Yizun Lin, Si Li, Andrzej Krol, Bradley J Beattie, John L Humm, Yuesheng Xu
PURPOSE: Performance of the preconditioned alternating projection algorithm (PAPA) using relaxed ordered subsets (ROS) with a non-smooth penalty function was investigated in positron emission tomography (PET). A higher order total variation (HOTV) regularizer was applied and a method for unsupervised selection of penalty weights based on the measured data is introduced. METHODS: A ROS version of PAPA with HOTV penalty (ROS-HOTV-PAPA) for PET image reconstruction was developed and implemented...
April 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28437011/noise-reduction-and-functional-maps-image-quality-improvement-in-dynamic-ct-perfusion-using-a-new-k-means-clustering-guided-bilateral-filter-kmgb
#2
Francesco Pisana, Thomas Henzler, Stefan Schönberg, Ernst Klotz, Bernhard Schmidt, Marc Kachelrieß
PURPOSE: Dynamic CT perfusion (CTP) consists in repeated acquisitions of the same volume in different time steps, slightly before, during and slightly afterwards the injection of contrast media. Important functional information can be derived for each voxel, which reflect the local hemodynamic properties and hence the metabolism of the tissue. Different approaches are being investigated to exploit data redundancy and prior knowledge for noise reduction of such datasets, ranging from iterative reconstruction schemes to high dimensional filters...
April 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28437010/technical-note-comparison-of-peripheral-patient-dose-from-mr-guided-60-co-therapy-and-6mv-linear-accelerator-igrt
#3
Pascal Hauri, Roger A Hälg, Uwe Schneider
PURPOSE: The use of X-ray imaging in radiation therapy can give a substantial dose to the patient. A Cobalt machine combined with an magnetic resonance imaging (MRI) was recently introduced to clinical work. One positive aspect of using non-ionizing imaging devices is the reduction of the patient exposure. The purpose of this study was to quantify the difference in out-of-field dose to the patient between the image guided radiation therapy (IGRT) treatment applied with a linear accelerator with cone beam CT (CBCT) equipment and a Cobalt machine combined with an MRI...
April 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28437000/magnetically-guided-capsule-endoscopy
#4
REVIEW
Naveen Shamsudhin, Vladimir I Zverev, Henrik Keller, Salvador Pane, Peter W Egolf, Bradley J Nelson, Alexander M Tishin
Wireless capsule endoscopy (WCE) is a powerful tool for medical screening and diagnosis, where a small capsule is swallowed and moved by means of natural peristalsis and gravity through the human gastrointestinal (GI) tract. The camera-integrated capsule allows for visualization of the small intestine, a region which was previously inaccessible to classical flexible endoscopy. As a diagnostic tool, it allows to localize the sources of bleedings in the middle-part of the gastrointestinal tract and to identify diseases such as inflammatory bowel disease (Crohn's disease), Polyposis-Syndrome and tumors...
April 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28432828/quantitative-contrast-enhanced-spectral-mammography-based-on-photon-counting-detectors-a-feasibility-study
#5
Huanjun Ding, Sabee Molloi
PURPOSE: To investigate the feasibility of accurate quantification of iodine mass thickness in contrast-enhanced spectral mammography. MATERIALS AND METHODS: A computer simulation model was developed to evaluate the performance of a photon-counting spectral mammography system in the application of contrast-enhanced spectral mammography. A figure-of-merit (FOM), which was defined as the decomposed iodine signal-to-noise ratio (SNR) with respect to the square root of the mean glandular dose (MGD), was chosen to optimize the imaging parameters, in terms of beam energy, splitting energy, and pre-filtrations for breasts of various thicknesses and densities...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28432822/focal-liver-lesions-segmentation-and-classification-in-nonenhanced-t2-weighted-mri
#6
Ilias Gatos, Stavros Tsantis, Maria Karamesini, Stavros Spiliopoulos, Dimitris Karnabatidis, John D Hazle, George C Kagadis
PURPOSE: To automatically segment and classify focal liver lesions (FLLs) on nonenhanced T2-weighted magnetic resonance imaging (MRI) scans using a computer-aided diagnosis (CAD) algorithm. METHODS: 71 FLLs (30 benign lesions, 19 hepatocellular carcinomas, and 22 metastases) on T2-weighted MRI scans were delineated by the proposed CAD scheme. The FLL segmentation procedure involved wavelet multiscale analysis to extract accurate edge information and mean intensity values for consecutive edges computed using horizontal and vertical analysis that were fed into the subsequent fuzzy C-means algorithm for final FLL border extraction...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28432820/the-impact-of-small-motion-on-the-visualization-of-coronary-vessels-and-lesions-in-cardiac-ct-a-simulation-study
#7
Francisco Contijoch, J Webster Stayman, Elliot R McVeigh
PURPOSE: Coronary x-ray computed tomography angiography (CCTA) is used to non-invasively assess coronary artery geometry and has, combined with computational modeling, demonstrated the potential to identify physiologically significant lesions. These measurements require robust and accurate coronary imaging and delineation of vessels in the presence of small motion. This simulation study characterizes the impact of small, uncorrected vessel drifts during data acquisition on the assessment of vessel intensity, diameter, and shape...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28432806/rapid-acceptance-testing-of-modern-linac-using-on-board-mv-and-kv-imaging-systems
#8
Sridhar Yaddanapudi, Bin Cai, Taylor Harry, Steven Dolly, Baozhou Sun, Hua Li, Keith Stinson, Camille Noel, Lakshmi Santanam, Todd Pawlicki, Sasa Mutic, S Murty Goddu
PURPOSE: The purpose of this study was to develop a novel process for using on-board MV and kV Electronic Portal Imaging Devices (EPIDs) to perform linac acceptance testing (AT) for two reasons: 1) to standardize the assessment of new equipment performance, and 2) to reduce the time to clinical use while reducing physicist workload. METHODS AND MATERIALS: In this study, Varian TrueBeam linacs equipped with amorphous silicon based EPID (aS1000) were used. The conventional set of AT tests and tolerances were used as a baseline guide...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28432792/monte-carlo-study-of-the-chamber-phantom-air-gap-effect-in-a-magnetic-field
#9
Daniel J O'Brien, Gabriel O Sawakuchi
PURPOSE: The aim of this study was to examine the effect of sub-millimeter air gaps that may exist between an ionization chamber and solid phantoms when measurements are performed in a magnetic field. METHODS: Geant4 Monte Carlo simulations were performed using a model of a PTW 30013 Farmer chamber in a water phantom. Symmetrical and asymmetrical air gaps of various thicknesses were modeled surrounding the chamber, and the dose to the air cavity of the chamber was scored in each case...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28429827/a-descriptive-and-broadly-applicable-model-of-therapeutic-and-stray-absorbed-dose-from-6-mv-to-25-mv-photon-beams
#10
Christopher W Schneider, Wayne D Newhauser, Lydia J Wilson, Uwe Schneider, Robert Kaderka, Saveta Miljanić, Željka Knežević, Liliana Stolarcyzk, Marco Durante, Roger M Harrison
PURPOSE: To develop a simple model of therapeutic and stray absorbed dose for a variety of treatment machines and techniques without relying on proprietary machine-specific parameters. METHODS: Dosimetry measurements conducted in this study and from the literature were used to develop an analytical model of absorbed dose from a variety of treatment machines and techniques in the 6 MV to 25 MV interval. A modified one-dimensional gamma-index analysis was performed to evaluate dosimetric accuracy of the model on an independent dataset consisting of measured dose profiles from seven treatment units spanning four manufacturers...
April 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28429391/technical-note-direct-measurement-of-continuous-tmr-data-with-a-1d-tank-and-automated-couch-movements
#11
Nels C Knutson, Matthew C Schmidt, Matthew D Belley, Ngoc Nguyen, H Harold Li, Erno Sajo, Michael Price
PURPOSE: Real-time dynamic control of the linear accelerator, couch, and imaging parameters during radiation delivery was investigated as a novel technique for acquiring tissue maximum ratio (TMR) data. METHODS: TrueBeam Developer Mode (Varian Medical Systems, Palo Alto, CA) was used to control the linear accelerator using the Extensible Markup Language (XML). A single XML file was used to dynamically manipulate the machine, couch, and imaging parameters during radiation delivery...
April 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28429382/technical-note-direct-measurement-of-clinical-mammographic-x-ray-spectra-using-a-cdte-spectrometer
#12
Josilene C Santos, Alessandra Tomal, Tânia A Furquim, Agnes M F Fausto, Maria S Nogueira, Paulo R Costa
PURPOSE: To introduce and evaluate a method developed for the direct measurement of mammographic x-ray spectra using a CdTe spectrometer. The assembly of a positioning system and the design of a simple and customized alignment device for this application is described. METHODS: A positioning system was developed to easily and accurately locate the CdTe detector in the x-ray beam. Additionally, an alignment device to line up the detector with the central axis of the radiation beam was designed...
April 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28429371/design-of-a-short-non-uniform-acquisition-protocol-for-quantitative-analysis-in-dynamic-cardiac-spect-imaging-a-retrospective-123-i-mibg-animal-study
#13
Yunlong Zan, Yong Long, Kewei Chen, Biao Li, Qiu Huang, Grant T Gullberg
PURPOSE: Our previous works have found that quantitative analysis of (123) I-MIBG kinetics in the heart with dynamic single-photon emission computed tomography (SPECT) offers the potential to quantify the innervation integrity at an early stage of left ventricular hypertrophy. However, conventional protocols involving a long acquisition time for dynamic imaging reduce the animal survival rate and thus make longitudinal analysis difficult. The goal of this work was to develop a procedure to reduce the total acquisition time by selecting non-uniform acquisition times for projection views while maintaining the accuracy and precision of estimated physiologic parameters...
April 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28426148/three-dimensional-finite-element-based-deformable-image-registration-for-evaluation-of-pleural-cavity-irradiation-during-photodynamic-therapy
#14
Rozhin Penjweini, Michele M Kim, Timothy C Zhu
PURPOSE: Photodynamic therapy (PDT) is used after surgical resection to treat the microscopic disease for malignant pleural mesothelioma and to increase survival rates. As accurate light delivery is imperative to PDT efficacy, the deformation of the pleural volume during the surgery is studied on its impact on the delivered light fluence. In this study, a three-dimensional finite element-based (3D FEM) deformable image registration is proposed to directly match the volume of lung to the volume of pleural cavity obtained during PDT to have accurate representation of the light fluence accumulated in the lung, heart and liver (organs-at-risk) during treatment...
April 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28425122/mean-intercept-anisotropy-analysis-of-porous-media-ii-conceptual-shortcomings-of-the-mil-tensor-definition-and-minkowski-tensors-as-an-alternative
#15
Michael A Klatt, Gerd E Schröder-Turk, Klaus Mecke
PURPOSE: Structure-property relations, which relate the shape of the microstructure to physical properties such as transport or mechanical properties, need sensitive measures of structure. What are suitable fabric tensors to quantify the shape of anisotropic heterogeneous materials? The mean intercept length is among the most commonly used characteristics of anisotropy in porous media, e. g., of trabecular bone in medical physics. Yet, in this series of two papers we demonstrate that it has conceptual shortcomings that limit the validity of its results...
April 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28425119/mean-intercept-anisotropy-analysis-of-porous-media-i-analytic-formulae-for-anisotropic-boolean-models
#16
Michael A Klatt, Gerd E Schröder-Turk, Klaus Mecke
PURPOSE: Structure-property relations, which relate the shape of the microstructure to physical properties such as transport or mechanical properties, need sensitive measures of structure. What are suitable fabric tensors to quantify the shape of anisotropic heterogeneous materials? The mean intercept length is among the most commonly used characteristics of anisotropy in porous media, for example, of trabecular bone in medical physics. METHODS: We analyze the orientation-biased Boolean model, a versatile stochastic model that represents microstructures as overlapping grains with an orientation bias towards a preferred direction...
April 20, 2017: Medical Physics
https://www.readbyqxmd.com/read/28422299/incorporation-of-pre-therapy-18-f-fdg-uptake-data-with-ct-texture-features-into-a-radiomics-model-for-radiation-pneumonitis-diagnosis
#17
Gregory J Anthony, Alexandra Cunliffe, Richard Castillo, Ngoc Pham, Thomas Guerrero, Samuel G Armato, Hania Al-Hallaq
PURPOSE: To determine whether the addition of standardized uptake value (SUV) from PET scans to CT lung texture features could improve a radiomics-based model of radiation pneumonitis (RP) diagnosis in patients undergoing radiotherapy. METHODS AND MATERIALS: Anonymized data from 96 esophageal cancer patients (18 RP-positive cases of Grade ≥ 2) were collected including pre-therapy PET/CT scans, pre-/post-therapy diagnostic CT scans and RP status. Twenty texture features (first-order, fractal, Laws' filter and gray-level co-occurrence matrix) were calculated from diagnostic CT scans and compared in anatomically matched regions of the lung...
April 19, 2017: Medical Physics
https://www.readbyqxmd.com/read/28421611/breast-density-measurement-using-photon-counting-spectral-mammography
#18
Henrik Johansson, Miriam von Tiedemann, Klaus Erhard, Harald Heese, Huanjun Ding, Sabee Molloi, Erik Fredenberg
PURPOSE: To evaluate a method for measuring breast density using photon-counting spectral mammography. Breast density is an indicator of breast cancer risk and diagnostic accuracy in mammography, and can be used as input to personalized screening, treatment monitoring and dose estimation. METHODS: The measurement method employs the spectral difference in x-ray attenuation between adipose and fibro-glandular tissue, and does not rely on any a-priori information. The method was evaluated using phantom measurements on tissue-equivalent material (slabs and breast-shaped phantoms) and using clinical data from a screening population (n=1329)...
April 19, 2017: Medical Physics
https://www.readbyqxmd.com/read/28423189/computed-tomography-quantification-of-tracheal-abnormalities-in-copd-and-their-influence-on-airflow-limitation
#19
Leticia Gallardo Estrella, Esther Pompe, Jan-Martin Kuhnigk, David A Lynch, Surya P Bhatt, Bram van Ginneken, Eva Marjolein van Rikxoort
PURPOSE: To present a method to automatically quantify tracheal morphology changes during breathing and investigate its contribution to airflow impairment when adding CT measures of emphysema, airway wall thickness, air trapping and ventilation. METHODS: Because tracheal abnormalities often occur localized, a method is presented that automatically determines the most abnormal trachea section based on automatically computed sagittal and coronal lengths. In this most abnormal section, trachea morphology is encoded using four equiangular rays from the center of the trachea and the normalized lengths of these rays are used as features in a classification scheme...
April 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28419533/a-new-approach-for-radiosynoviorthesis-a-dose-optimized-planning-method-based-on-monte-carlo-simulation-and-synovial-measurement-using-3d-slicer-and-mri
#20
Mirta Bárbara Torres Berdeguez, Sylvia Thomas, Patricia Rafful, Tiago Arruda Sanchez, Susie Medeiros Oliveira Ramos, Marta Souza Albernaz, Lidia Vasconcellos de Sá, Sergio Augusto Lopes de Souza, Felix Mas Milian, Ademir Xavier da Silva
PURPOSE: Recently, there has been a growing interest in a methodology for dose planning in radiosynoviorthesis to substitute fixed activity. Clinical practice based on fixed activity frequently does not embrace radiopharmaceutical dose optimization in patients. The aim of this paper is to propose and discuss a dose planning methodology considering the radiological findings of interest obtained by three-dimensional magnetic resonance imaging combined with Monte Carlo simulation in radiosynoviorthesis treatment applied to hemophilic arthropathy...
April 17, 2017: Medical Physics
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