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Medical Physics

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https://www.readbyqxmd.com/read/28222217/multi-component-diffusion-characterization-of-radiation-induced-white-matter-damage
#1
Roshan A Karunamuni, Nathan S White, Carrie R McDonald, Michael Connor, Niclas Pettersson, Tyler M Seibert, Joshua Kuperman, Nikdokht Farid, Vitali Moiseenko, Anders M Dale, Jona A Hattangadi-Gluth
PURPOSE: We used multi-b-value diffusion models to characterize microstructural white matter changes after brain radiation into fast and slow components, in order to better understand the pathophysiology of radiation-induced tissue damage. METHODS: Fourteen patients were included in this retrospective analysis with imaging prior to, and at 1, 4-5, and 9-10 months after radiotherapy (RT). Diffusion signal decay within brain white matter was fit to a bi-exponential model to separate changes within the slow and fast components...
February 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28214368/evaluation-of-deformable-image-registration-between-external-beam-radiotherapy-and-hdr-brachytherapy-for-cervical-cancer-with-a-3d-printed-deformable-pelvis-phantom
#2
Noriyuki Kadoya, Yuya Miyasaka, Yujiro Nakajima, Yoshihiro Kuroda, Kengo Ito, Mizuki Chiba, Kiyokazu Sato, Suguru Dobashi, Takaya Yamamoto, Noriyoshi Takahashi, Masaki Kubozono, Ken Takeda, Keiichi Jingu
PURPOSE: In this study, we developed a 3D-printed deformable pelvis phantom for evaluating spatial DIR accuracy. We then evaluated the spatial DIR accuracies of various DIR settings for cervical cancer. METHODS: A deformable female pelvis phantom was created based on patient CT data using 3D printing. To create the deformable uterus phantom, we first 3D printed both a model of uterus and a model of the internal cavities of the vagina and uterus. We then made a mold using the 3D printed uterus phantom...
February 18, 2017: Medical Physics
https://www.readbyqxmd.com/read/28211070/use-of-proximal-operator-graph-solver-for-radiation-therapy-inverse-treatment-planning
#3
Xinmin Liu, Charles Pelizzari, Andrew H Belcher, Zachary Grelewicz, Rodney D Wiersma
PURPOSE: Most radiation therapy optimization problems can be formulated as an unconstrained problem and solved efficiently by quasi-Newton methods such as the Limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm. However, several next generation planning techniques such as total variation regularization based optimization and MV+kV optimization, involve constrained or mixed-norm optimization, and cannot be solved by quasi-Newton methods. Using standard optimization algorithms on such problems often leads to prohibitively long optimization times and large memory requirements...
February 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28211105/joint-reconstruction-of-ictal-inter-ictal-spect-data-for-improved-epileptic-foci-localization
#4
Yothin Rakvongthai, Frederic Fahey, Korn Borvorntanajanya, Supatporn Tepmongkol, Usanee Vutrapongwatana, Katherine Zukotynski, Georges El Fakhri, Jinsong Ouyang
PURPOSE: To improve the performance for localizing epileptic foci, we have developed a joint ictal/inter-ictal SPECT reconstruction method in which ictal and inter-ictal SPECT projections are simultaneously reconstructed to obtain the differential image. METHODS: We have developed a SPECT reconstruction method that jointly reconstructs ictal and inter-ictal SPECT projection data. We performed both phantom and patient studies to evaluate the performance of our joint method for epileptic foci localization as compared with the conventional subtraction method in which the differential image is obtained by subtracting the inter-ictal image from the co-registered ictal image...
February 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28211058/a-feasibility-study-of-a-hybrid-breast-immobilization-system-for-early-breast-cancer-in-proton-beam-therapy
#5
Takeshi Arimura, Takashi Ogino, Takashi Yoshiura, Mitsugi Matsuyama, Naoaki Kondo, Hideki Miyazaki, Akari Sakuragi, Takayuki Ohara, Etsuyo Ogo, Yoshio Hishikawa
PURPOSE: We aimed to develop a new breast-immobilizing system for proton beam therapy (PBT) of early breast cancer (EBC) that would provide the optimum breast shape during the treatment as well as increased fixation reliability by reducing the influence of respiratory movement. METHODS: The breast-immobilizing system (HyBIS; Hybrid Breast-Immobilizing System) consists of a whole body immobilization system (WBIS), position converting device (to change patient position), photo scanning system, breast cup (made using a three-dimensional printer), breast cup fitting apparatus, breast cup holding device (to ensure the breast remains lifted in the supine position), and dedicated stretcher fixed to the WBIS (to carry the patient)...
February 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28207950/simplifying-volumes-of-interest-vois-definition-in-quantitative-spect-beyond-manual-definition-of-3d-whole-organ-vois
#6
Esther M Vicente, Martin A Lodge, Steven P Rowe, Richard L Wahl, Eric C Frey
PURPOSE: We investigated the feasibility of using simpler methods than manual whole-organ volume-of-interest (VOI) definition to estimate the organ activity concentration in single photon emission computed tomography (SPECT) in cases where the activity in the organ can be assumed to be uniformly distributed on the scale of the voxel size. In particular, we investigated an anatomic region-of-interest (ROI) defined in a single transaxial slice, and a single sphere placed inside the organ boundaries...
February 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28206679/technical-note-determination-of-individual-thyroid-clearance-effective-half-life-with-a-common-handheld-electronic-dosimeter
#7
Markus Fürstner, Michael Hentschel, Petar-Marko Spanjol, George A Prenosil, Sabine Weidner, Thomas Krause, Bernd Klaeser
PURPOSE: To determine the thyroid clearance effective half-life (Ʈ) with a common handheld electronic dosimeter (ED) in patients undergoing radioiodine treatment for hyperthyroidism. METHODS: Dose rates from twelve inpatients were measured daily with an ED and with a clinical uptake counter. The ED was attached to the patient with two different setups, one using a cervical collar and another employing a neck strap. Estimation of Ʈ was performed by linear regression analysis of the log of both the ED and the uptake counter measurements versus time...
February 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28206676/thoracic-ct-mri-co-registration-for-regional-pulmonary-structure-function-measurements-of-obstructive-lung-disease
#8
Fumin Guo, Sarah Svenningsen, Miranda Kirby, Dante P I Capaldi, Khadija Sheikh, Aaron Fenster, Grace Parraga
PURPOSE: Recent pulmonary imaging research has revealed that in patients with chronic obstructive pulmonary disease (COPD) and asthma, structural and functional abnormalities are spatially heterogeneous. This novel information may help optimize treatment in individual patients, monitor interventional efficacy and develop new treatments. Moreover, by automating the measurement of regional biomarkers for the 19 different anatomical lung segments, there is an opportunity to embed imaging biomarkers into clinically-acceptable clinical workflows and improve lung disease clinical care...
February 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28206667/geometry-calibration-method-for-a-cone-beam-ct-system
#9
Hongkai Yang, Kejun Kang, Yuxiang Xing
PURPOSE: The positioning accuracy of each component is important to ensure the image quality of cone-beam CT. However, accurate positioning is not easy and requires experience and time. The option is to calibrate the geometric parameters and then plug them into a reconstruction algorithm which is the preferred solution in practice. In this case, the image quality is determined by the accuracy and precision of the calibration method. This work describes a method to independently calibrate an imaging system in each pose (projection angle) for a cone-beam CT with a non-ideal-circular trajectory...
February 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28196288/clinical-adequacy-assessment-of-auto-contours-for-prostate-imrt-with-meaningful-endpoints
#10
Hamidreza Nourzadeh, William T Watkins, Mahmoud Ahmad, Cheukkai Hui, David Schlesinger, Jeffrey V Siebers
PURPOSE: To determine if radiation treatment plans created based on auto-segmented (AS) regions-of-interest (ROI)s are clinically equivalent to plans created based on manually segmented ROIs, where equivalence is evaluated using probabilistic dosimetric metrics and probabilistic biological endpoints for prostate IMRT. METHOD AND MATERIALS: Manually drawn contours and auto-segmented ROIs were created for 167 CT image sets acquired from 19 prostate patients. Auto-segmentation was performed utilizing Pinnacle's Smart Probabilistic Image Contouring Engine...
February 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/28196280/cuda-based-acceleration-and-bpn-assisted-automation-of-bilateral-filtering-for-brain-mr-image-restoration
#11
Herng-Hua Chang, Yu-Ning Chang
PURPOSE: Bilateral filters have been substantially exploited in numerous magnetic resonance (MR) image restoration applications for decades. Due to the deficiency of theoretical basis on the filter parameter setting, empirical manipulation with fixed values and noise variance related adjustments has generally been employed. The outcome of these strategies is usually sensitive to the variation of the brain structures and not all the three parameter values are optimal. This article is in an attempt to investigate the optimal setting of the bilateral filter, from which an accelerated and automated restoration framework is developed...
February 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/28196271/dose-distribution-at-the-bragg-peak-dose-measurements-using-ebt-and-rtqa-gafchromic-film-set-at-two-positions-to-the-central-beam-axis
#12
Borowicz Dorota Maria, Malicki Julian, Mytsin Gennady, Shipulin Konstantin
AIM: To evaluate the impact of radiochromic film positioning relative to the central beam axis (CAX) in proton beam therapy. Secondarily, to compare the dosimetric measurements obtained by RTQA and EBT film and to compare these to the doses calculated by the treatment planning system (TPS). METHODS: EBT and RTQA dosimetric radiochromic films were immersed in a water phantom and irradiated with a proton beam. The films were placed parallel to the CAX and at a 5º angle on the horizontal plane to assess the effect of film inclination on Bragg peak profiles...
February 14, 2017: Medical Physics
https://www.readbyqxmd.com/read/28195345/in-vivo-measurements-of-human-neck-skin-elasticity-using-mri-and-finite-element-modeling
#13
Yunqiang An, Changjin Ji, Yong Li, Jianxia Wang, Xinyue Zhang, Yaqi Huang
PURPOSE: The assessment of mechanical properties of the human skin is very important in investigating the mechanism of obstructive sleep apnea, a common disorder characterized by repetitive collapse and obstruction of the upper airway during sleep. In this study, a unique method, combining magnetic resonance imaging (MRI) and finite element modeling (FEM), was developed to obtain the value of the in vivo elastic modulus of the neck skin. MEHTHOD: A total of 22 subjects, 16 males and 6 females, were recruited to participate in the MRI studies...
February 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/28192624/mr-based-synthetic-ct-generation-using-a-deep-convolutional-neural-network-method
#14
Xiao Han
PURPOSE: Interests have been rapidly growing in the field of radiotherapy to replace CT with magnetic resonance imaging (MRI), due to superior soft tissue contrast offered by MRI and the desire to reduce unnecessary radiation dose. MR-only radiotherapy also simplifies clinical workflow and avoids uncertainties in aligning MR with CT. Methods, however, are needed to derive CT-equivalent representations, often known as synthetic CT (sCT), from patient MR images for the purpose of dose calculation and DRR-based patient positioning...
February 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/28192614/cone-beam-ct-based-adaptive-planning-improves-permanent-prostate-brachytherapy-dosimetry-an-analysis-of-1266-patients
#15
Hendrik Westendorp, Carel J Hoekstra, Jos J Immerzeel, Sandrine M G van de Pol, Charles G H J Niël, Robert A J Kattevilder, Tonnis T Nuver, André W Minken, Marinus A Moerland
PURPOSE: To evaluate adaptive planning for permanent prostate brachytherapy and to identify the prostate regions that needed adaptation. METHODS AND MATERIALS: After the implantation of stranded seeds, using real-time intraoperative planning, a transrectal ultrasound (TRUS)-scan was obtained and contoured. The positions of seeds were determined on a C-arm cone-beam Computed Tomography (CBCT)-scan. The CBCT-scan was registered to the TRUS-scan using fiducial gold markers...
February 13, 2017: Medical Physics
https://www.readbyqxmd.com/read/28186647/technical-note-fully-automated-analysis-of-jaszczak-phantom-measurements-as-part-of-routine-spect-quality-control
#16
Albert Hirtl, Helmar Bergmann, Barbara Knäusl, Thomas Beyer, Michael Figl, Johann Hummel
PURPOSE: Inspection and quantitative validation of tomographic imaging properties of SPECT systems, i.e. spatial resolution, contrast and inhomogeneity must be performed in regular intervals. Typically, the modular Jaszczak phantom is used for that purpose, since it offers the possibility to investigate all three system properties with a single measurement. The interpretation of the measurement is performed visually, thus, being insensitive to subtle changes in system performance. To overcome this limitation, a fully-automated software for the objective analysis of Jaszczak phantom measurements is proposed here...
February 10, 2017: Medical Physics
https://www.readbyqxmd.com/read/28186630/cascade-convolutional-neural-networks-for-automatic-detection-of-thyroid-nodules-in-ultrasound-images
#17
Jinlian Ma, Fa Wu, Tian'an Jiang, Jiang Zhu, Dexing Kong
PURPOSE: It is very important for calculation of clinical indices and diagnosis to detect thyroid nodules from ultrasound images. However, this task is a challenge mainly due to heterogeneous thyroid nodules with distinct components are similar to background in ultrasound images. In this study, we employ cascade deep convolutional neural networks (CNNs) to develop and evaluate a fully automatic detection of thyroid nodules from 2D ultrasound images. METHODS: Our cascade CNNs are a type of hybrid model, consisting of two different CNNs and a new splitting method...
February 10, 2017: Medical Physics
https://www.readbyqxmd.com/read/28185281/technical-note-analysis-of-motion-blurring-artifact-in-fast-helical-free-breathing-thoracic-ct-scans
#18
Daniel A Low, Lisa Yang, Jingjia Chen, Dylan O'Connel, John H Lewis, David H Thomas, Percy Lee
PURPOSE: To measure and characterize breathing-induced motion artifacts in fast helical free-breathing CT scans. METHODS: 10 lung cancer patients were scanned using fast-helical CT during free breathing. In each case, 25 low-dose CT scans were acquired in alternating craniocaudal and caudocranial directions. A bellows-based breathing surrogate was simultaneously acquired. A published breathing motion model was used to estimate the diaphragm craniodaudal velocity at each CT scan...
February 10, 2017: Medical Physics
https://www.readbyqxmd.com/read/28182277/improving-computer-aided-detection-assistance-in-breast-cancer-screening-by-removal-of-obviously-false-positive-findings
#19
Jan-Jurre Mordang, Albert Gubern-Mérida, Alessandro Bria, Francesco Tortorella, Gerard den Heeten, Nico Karssemeijer
PURPOSE: Computer-Aided Detection (CADe) systems for mammography screening still mark many false positives. This can cause that radiologists lose confidence in CADe, especially when many false positive are obviously not suspicious to them. In this study we focus on obvious false positives generated by microcalcification detection algorithms. METHODS: We aim at reducing the number of obvious false positive findings by adding an additional step in the detection method...
February 9, 2017: Medical Physics
https://www.readbyqxmd.com/read/28177548/7t-guided-super-resolution-of-3t-mri
#20
Khosro Bahrami, Feng Shi, Islem Rekik, Yaozong Gao, Dinggang Shen
PURPOSE: High-resolution MR images can depict rich details of brain anatomical structures and show subtle changes in longitudinal data. 7T MRI scanners can acquire MR images with higher resolution and better tissue contrast than the routine 3T MRI scanners. However, 7T MRI scanners are currently more expensive and less available in clinical and research centers. To this end, we propose a method to generate super-resolution 3T MRI that resembles 7T MRI, which is called as 7T-like MR image in this paper...
February 8, 2017: Medical Physics
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