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Medical Physics

Daniel Gourdeau, Luc Gingras, Frédéric Beaulieu, Ghyslain Leclerc, Louis Archambault
PURPOSE: Medical linear accelerators (linac) are delivering increasingly complex treatments using modern techniques in radiation therapy. Complete and precise mechanical QA of the linac is therefore necessary to ensure that there is no unexpected deviation from the gantry's planned course. However, state-of-the-art EPID-based mechanical QA procedures often neglect some degrees of freedom (DOF) like the in-plane rotations of the gantry and imager or the source movements inside the gantry head...
September 22, 2018: Medical Physics
Fekadu L Bayis, Xijia Liu, Anders Garpebring, Jun Yu
PURPOSE: There is in creasing interest in computed tomography (CT) image estimations from magnetic resonance (MR) images. The estimated CT images can be utilised for attenuation correction, patient positioning, and dose planning in diagnostic and radiotherapy workflows. This study aims to introduce a novel statistical learning approach for improving CT estimation from MR images and to compare the performance of our method with the existing model based CT image estimation methods. METHODS: The statistical learning approach proposed here consists of two stages...
September 22, 2018: Medical Physics
Hyoung Suk Park, Sung Min Lee, Hwa Pyung Kim, Jin Keun Seo, Yong Eun Chung
PURPOSE: This paper proposes a sinogram-consistency learning method to deal with beam-hardening related artifacts in polychromatic computerized tomography (CT). The presence of highly attenuating materials in the scan field causes an inconsistent sinogram, that does not match the range space of the Radon transform. When the mismatched data are entered into the range space during CT reconstruction, streaking and shading artifacts are generated owing to the inherent nature of the inverse Radon transform METHODS: The proposed learning method aims to repair inconsistent sinogram by removing the primary metal-induced beam-hardening factors along the metal trace in the sinogram...
September 20, 2018: Medical Physics
Rani Al-Senan
PURPOSE: The purpose of this paper is to present a method of determining the dose profile of the beam bow-tie filter (BTF) without the need for fixing the x-ray tube in a position or using special instruments or dosimeters other than the ordinary types of ion chambers used for CT dosimetry (e.g. Farmer chamber). METHODS: The idea behind this method is to try to invert the integral of exposures from axial measurements by decomposing it into fractions per degree of tube rotation...
September 20, 2018: Medical Physics
Marthony Robins, Justin Solomon, Taylor Richards, Ehsan Samei
PURPOSE: The purpose of this study was to investigate how accurately the task-transfer function (TTF) models the signal transfer properties of low-contrast features in a non-linear commercial CT system. METHODS: A cylindrical phantom containing 24 anthropomorphic "physical" lesions was 3D printed. Lesions had two sizes (523, 2145 mm3), and two nominal radio-densities (80 and 100 HU at 120 kV). CT images were acquired on a commercial CT system (Siemens Flash scanner) at four dose levels (CTDIvol, 32 cm phantom:1...
September 19, 2018: Medical Physics
Mazen Soufi, Hidetaka Arimura, Noriyuki Nagami
PURPOSE: To identify the optimal mother wavelets in survival prediction of lung cancer patients using wavelet-decomposition-based (WDB) radiomic features in CT images. MATERIALS AND METHODS: CT images of patients with histologically confirmed non-small cell lung carcinomas (NSCLCs) in Training (Dataset T; n = 162) and validation (Dataset V; n = 143) datasets were analyzed for this study. The optimal mother wavelets were identified based on the impacts of the WDB radiomic features on the patient survival times...
September 19, 2018: Medical Physics
Jing Cai, Dharanipathy Rangaraj, Sridhar Yaddanapudi
Real-time radiation dose monitoring during treatment delivery is highly desired for quality assurance purposes but has been hampered in its clinical implementation due to various technical challenges. Recent advances in transmission detector technology offer a potential solution for real-time dosimetric measurements of treatment delivery. While some are optimistic about the clinical adoption of transmission detector technology for enhancing the safety of radiation therapy, others have some significant concerns about using transmission detectors for dosimetric measurements...
September 19, 2018: Medical Physics
Mark J Gooding, Annamarie J Smith, Maira Tariq, Paul Aljabar, Devis Peressutti, Judith van der Stoep, Bart Reymen, Daisy Emans, Djoya Hattu, Judith van Loon, Maud de Rooy, Rinus Wanders, Stephanie Peeters, Tim Lustberg, Johan van Soest, Andre Dekker, Wouter van Elmpt
PURPOSE: Automated techniques for estimating the contours of organs and structures in medical images have become more widespread and a variety of measures are available for assessing their quality. Quantitative measures of geometric agreement, e.g. overlap with a gold-standard delineation, are popular but may not predict the level of clinical acceptance for the contouring method. Therefore, surrogate measures that relate more directly to the clinical judgment of contours, and to the way they are used in routine workflows, need to be developed...
September 19, 2018: Medical Physics
Martha M Matuszak, Clifton D Fuller, Torunn I Yock, Clayton B Hess, Todd McNutt, Shruti Jolly, Peter Gabriel, Charles S Mayo, Maria Thor, Amanda Caissie, Arvind Rao, Dawn Owen, Wade Smith, Jatinder Palta, Rishabh Kapoor, James Hayman, Mark Waddle, Barry Rosenstein, Robert Miller, Seungtaek Choi, Amy Moreno, Joseph Herman, Mary Feng
It is an exciting time for big data efforts in radiation oncology. The use of big data to help aid both outcomes and decision-making research is becoming a reality. However, there are true challenges that exist in the space of gathering and utilizing performance and outcomes data. Here, we summarize the current state of big data in radiation oncology with respect to outcomes and discuss some of the efforts and challenges in radiation oncology big data.
September 19, 2018: Medical Physics
Andrew Jeung, Liangjia Zhu, Marcelo Cassese, Roberto Luevano, Josh Star-Lack
PURPOSE: The shape, size, and location of the x-ray beam spot (where the electron beam strikes the target) in a linac-based radiation therapy machine is of potential clinical significance. Established techniques to measure the beam spot parameters involve specialized hardware and typically assess size and shape of the beam spot or its position, but not both. A simple apparatus and algorithm for measuring all beam spot parameters simultaneously is proposed here. METHODS: The apparatus is composed of two partially transmitting edge plates mounted at different vertical positions...
September 19, 2018: Medical Physics
John B Ludlow
PURPOSE: Radiation dose is a general concern in diagnostic imaging and a special concern for children who are at greater risk from radiation effects. This study evaluates effective doses (E) produced during 2D and volume imaging with a novel cone beam computed tomography (CBCT) based extremity imaging device. The device's compact size and protocol options offer image choices that enhance the potential for reduced dose and improved diagnostics when evaluating sports injuries. METHODS: Hand-wrist, foot-ankle, and knee phantoms were developed for use with optically stimulated luminescent dosimeters (OSL)...
September 19, 2018: Medical Physics
Guillaume Zahnd, Kozue Saito, Kazuyuki Nagatsuka, Yoshito Otake, Yoshinobu Sato
PURPOSE: The motion of the common carotid artery tissue layers along the vessel axis during the cardiac cycle, observed in ultrasound imaging, is associated with the presence of established cardiovascular risk factors. However, the vast majority of the (semi-)automatic methods devised to measure this so-called "longitudinal kinetics" phenomenon are based on the tracking of a single point, thus failing to capture the overall-and potentially inhomogeneous-motion of the entire arterial wall...
September 19, 2018: Medical Physics
Tiantian Li, Greta S P Mok
PURPOSE: Previously we have shown that using sequential CT images is superior to sequential SPECT for non-rigid registration in 3D targeted radionuclide therapy (TRT) dosimetry. However, sequential CTs are often not available due to radiation concerns. In this paper, we propose a virtual CT (vCT) method for attenuation and scatter correction, image registration and segmentation for improved dosimetric accuracy with single CT acquisition. METHODS: We used a population of 9 XCAT phantoms with different In-111 Zevalin biokinetics and anatomical variations for the simulations...
September 19, 2018: Medical Physics
Lydia A den Otter, Evangelia Kaza, Roel G J Kierkels, Arturs Meijers, Fred J F Ubbels, Martin O Leach, David J Collins, Johannes A Langendijk, Antje-Christin Knopf
PURPOSE: The treatment of moving targets with scanned proton beams is challenging. For motion mitigation, an Active Breathing Coordinator (ABC) can be used to assist breath-holding. The delivery of pencil beam scanning fields often exceeds feasible breath-hold durations, requiring high breath-hold reproducibility. We evaluated the robustness of scanned proton therapy against anatomical uncertainties when treating non-small-cell lung cancer (NSCLC) patients during ABC controlled breath-hold...
September 19, 2018: Medical Physics
Barry S Rosenstein, Arvind Rao, Jean M Moran, Daniel E Spratt, Marc S Mendonca, Bissan Al-Lazikani, Charles S Mayo, Corey Speers
No abstract text is available yet for this article.
September 18, 2018: Medical Physics
C S Mayo, M Phillips, T R McNutt, J Palta, A Dekker, R C Miller, Y Xiao, J M Moran, M M Matuszak, P Gabriel, A S Ayan, J Prisciandaro, M Thor, N Dixit, R Popple, J Killoran, E Kaleba, M Kantor, D Ruan, R Kapoor, M L Kessler, T S Lawrence
The term Big Data has come to encompass a number of concepts and uses within medicine. This paper lays out the relevance and application of large collections of data in the radiation oncology community. We describe the potential importance and uses in clinical practice. The important concepts are then described and how they have been or could be implemented are discussed. Impediments to progress in the collection and use of sufficient quantities of data are also described. Finally, recommendations for how the community can move forward to achieve the potential of big data in radiation oncology are provided...
September 18, 2018: Medical Physics
YingLiang Ma, Mazen Alhrishy, Srinivas Ananth Narayan, Peter Mountney, Kawal S Rhode
PURPOSE: Catheters and guidewires are used extensively in cardiac catheterization procedures such as heart arrhythmia treatment (ablation), angioplasty and congenital heart disease treatment. Detecting their positions in fluoroscopic X-ray images is important for several clinical applications, for example, motion compensation, co-registration between 2D and 3D imaging modalities and 3D object reconstruction. METHODS: For the generalized framework, a multiscale vessel enhancement filter is first used to enhance the visibility of wire-like structures in the X-ray images...
September 16, 2018: Medical Physics
Huiqiao Xie, Tianye Niu, Shaojie Tang, Xiaofeng Yang, Nadja Kadom, Xiangyang Tang
PURPOSE: Denoising has been a challenging research subject in medical imaging, since the suppression of noise conflicts with the preservation of texture and edges. To address this challenge, we develop a content-oriented sparse representation (COSR) method for denoising in CT. METHODS: An image is segmented into a number of content-areas and each of them consists of similar material. Having been ex-painted, each content-area is sparsely coded using the dictionary learnt from patches extracted from the corresponding content-area...
September 16, 2018: Medical Physics
Andrew J Shepard, Charles K Matrosic, Jeffrey L Radtke, Sydney A Jupitz, Wesley S Culberson, Bryan P Bednarz
PURPOSE: Latencies for motion management systems have previously been presented as guidelines for system development and implementation. These guidelines consider the overall system latency, including data acquisition, algorithm processing, and linac triggering time. However, during system development, the triggering latency of the clinical linear accelerator is often considered fixed. This paper presents a method to decouple the linac-only triggering latency from the total system latency such that latency can be considered in terms of only the linac-independent aspects of the system...
September 16, 2018: Medical Physics
Yiyuan Zhao, Benoit M Dawant, Robert F Labadie, Jack H Noble
PURPOSE: Cochlear Implants (CIs) are neural prosthetic devices that provide a sense of sound to people who experience profound hearing loss. Recent research has indicated that there is a significant correlation between hearing outcomes and the intra-cochlear locations of the electrodes. We have developed an image-guided cochlear implant programming (IGCIP) system based on this correlation to assist audiologists with programming CI devices. One crucial step in our IGCIP system is the localization of CI electrodes in post-implantation CTs...
September 14, 2018: Medical Physics
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