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Xuelin Cui, Lamine Mili, Ge Wang, Hengyong Yu
Since their inceptions, the multimodal imaging techniques have received a great deal of attention for achieving enhanced imaging performance. In this work, a novel joint reconstruction framework using sparse computed tomography (CT) and magnetic resonance imaging (MRI) data is developed and evaluated. CT and MRI images are synchronously acquired and registered from a hybrid CT-MRI platform. Because image data are highly undersampled, analytic methods are unable to generate decent image quality. To overcome this drawback, we resort to the compressed sensing (CS) techniques, which employ sparse priors that result from an application of a wavelet transform...
March 15, 2018: Journal of X-ray Science and Technology
Cui Feng, Di Zhu, Xianlun Zou, Anqin Li, Xuemei Hu, Zhen Li, Daoyu Hu
To investigate the subjective and quantitative image quality and radiation exposure of CT enterography (CTE) examination performed at low tube voltage and low concentration of contrast agent with adaptive statistical iterative reconstruction (ASIR) algorithm, compared with conventional CTE.One hundred thirty-seven patients with suspected or proved gastrointestinal diseases underwent contrast enhanced CTE in a multidetector computed tomography (MDCT) scanner. All cases were assigned to 2 groups. Group A (n = 79) underwent CT with low tube voltage based on patient body mass index (BMI) (BMI < 23 kg/m, 80 kVp; BMI ≥ 23 kg/m, 100 kVp) and low concentration of contrast agent (270 mg I/mL), the images were reconstructed with standard filtered back projection (FBP) algorithm and 50% ASIR algorithm...
March 2018: Medicine (Baltimore)
Sadreddin Mahmoodkalayeh, Hossein Z Jooya, Ali Hariri, Yang Zhou, Qiuyun Xu, Mohammad A Ansari, Mohammad R N Avanaki
We study the temperature dependence of the underlying mechanisms related to the signal strength and imaging depth in photoacoustic imaging. The presented theoretical and experimental results indicate that imaging depth can be improved by lowering the temperature of the intermediate medium that the laser passes through to reach the imaging target. We discuss the temperature dependency of optical and acoustic properties of the intermediate medium and their changes due to cooling. We demonstrate that the SNR improvement of the photoacoustic signal is mainly due to the reduction of Grüneisen parameter of the intermediate medium which leads to a lower level of background noise...
March 20, 2018: Scientific Reports
Ethan Phillip M LaRochelle, Jennifer R Shell, Jason R Gunn, Scott C Davis, Brian W Pogue
During external beam radiotherapy (EBRT), in vivo Cherenkov optical emissions can be used as a dosimetry tool or to excite luminescence, termed Cherenkov-excited luminescence (CEL) with microsecond-level time-gated cameras. The goal of this work was to develop a complete theoretical foundation for the detectable signal strength, in order to provide guidance on optimization of the limits of detection and how to optimize near real time imaging. The key parameters affecting photon production, propagation and detection were considered and experimental validation with both tissue phantoms and a murine model are shown...
March 20, 2018: Physics in Medicine and Biology
Sam Denys, Michael Hofmann, Heleen Luts, Cécile Guérin, Ann Keymeulen, Katelijne Van Hoeck, Astrid van Wieringen, Karel Hoppenbrouwers, Jan Wouters
OBJECTIVES: This study aims to investigate the large-scale applicability of the Digit Triplet test (DTT) for school-age hearing screening in fifth grade elementary (5E) (9 to 12 years old) and third grade secondary (3S) (13 to 16 years old) school children. The reliability of the test is investigated as well as whether pass/fail criteria need to be corrected for training and/or age, and whether these criteria have to be refined with respect to referral rates and pure-tone audiometry results...
March 19, 2018: Ear and Hearing
Benjamin Dieudonné, Tom Francart
Many hearing-impaired listeners struggle to localize sounds due to poor availability of binaural cues. Listeners with a cochlear implant and a contralateral hearing aid - so-called bimodal listeners - are amongst the worst performers, as both interaural time and level differences are poorly transmitted. We present a new method to enhance head shadow in the low frequencies. Head shadow enhancement is achieved with a fixed beamformer with contralateral attenuation in each ear. The method results in interaural level differences which vary monotonically with angle...
March 12, 2018: Hearing Research
Muriel T N Panouillères, Rowan Boyles, Jennifer Chesters, Kate E Watkins, Riikka Möttönen
Comprehending speech can be particularly challenging in a noisy environment and in the absence of semantic context. It has been proposed that the articulatory motor system would be recruited especially in difficult listening conditions. However, it remains unknown how signal-to-noise ratio (SNR) and semantic context affect the recruitment of the articulatory motor system when listening to continuous speech. The aim of the present study was to address the hypothesis that involvement of the articulatory motor cortex increases when the intelligibility and clarity of the spoken sentences decreases, because of noise and the lack of semantic context...
February 22, 2018: Cortex; a Journal Devoted to the Study of the Nervous System and Behavior
Kaiyi Zhu, Yueyue Lu, Shulian Zhang, Haowen Ruan, Shin Usuki, Yidong Tan
Ultrasound modulated laser confocal feedback technology is proposed in the imaging inside turbid media. By selecting the detectable signal photons and rejecting the background noise photons in the frequency domain based on the ultrasound modulation, the signal-to-noise ratio (SNR) can be much improved, especially in the turbid media, compared with the traditional imaging without ultrasound modulation. This is a promising method to reach both a larger penetration depth and a better SNR than other optical methods...
March 15, 2018: Optics Letters
Yubin Hou, Qian Zhang, Shuxian Qi, Xian Feng, Pu Wang
We demonstrate a polarization-maintaining (PM) dual-wavelength (DW) single-frequency Er-doped distributed Bragg reflection (DBR) fiber laser with 28 GHz stable frequency difference. A homemade PM low-reflectivity superimposed fiber Bragg grating (SFBG) is employed as the output port of the DBR fiber laser. The SFBG has two reflection wavelengths located in the same grating region. The reflectivity of both DWs is around 85%. The achieved linear polarization extinction ratio is more than 20 dB. The DWs of the laser output are located at 1552...
March 15, 2018: Optics Letters
Mazin Jouda, Robert Kamberger, Jochen Leupold, Nils Spengler, Jürgen Hennig, Oliver Gruschke, Jan G Korvink
High signal-to-noise ratio (SNR) of the NMR signal has always been a key target that drives massive research effort in many fields. Among several parameters, a high filling factor of the MR coil has proven to boost the SNR. In case of small-volume samples, a high filling factor and thus a high SNR can be achieved through miniaturizing the MR coil. However, under certain circumstances, this can be impractical. In this paper, we present an extensive theoretical and experimental investigation of the inductively coupled LC resonator and the magnetic Lenz lens as two candidate approaches that can enhance the SNR in such circumstances...
July 2017: Concepts in Magnetic Resonance. Part B, Magnetic Resonance Engineering
Kiaran P McGee, Robert S Stormont, Scott A Lindsay, Victor Taracila, Dennis Savitskij, Fraser Robb, Robert Witte, Timothy Kaufmann, John Huston Iii, Stephen J Riederer, Eric Borisch, Phillip J Rossman
The growth in the use of magnetic resonance imaging (MRI) data for radiation therapy (RT) treatment planning has been facilitated by scanner hardware and software advances that have enabled RT patients to be imaged in treatment position while providing morphologic and functional assessment of tumor volumes and surrounding normal tissues. Despite these advances, manufacturers have been slow to develop radiofrequency (RF) coils that closely follow the contour of a RT patient undergoing MR imaging. Instead, relatively large form surface coil arrays have been adapted from diagnostic imaging...
March 14, 2018: Physics in Medicine and Biology
L Alejo, E Corredoira, F Sánchez-Muñoz, C Huerga, Z Aza, R Plaza-Núñez, A Serrada, M Bret-Zurita, M Parrón, C Prieto-Areyano, G Garzón-Moll, R Madero, E Guibelalde
Objective: The new 2013/59 EURATOM Directive (ED) demands dosimetric optimisation procedures without undue delay. The aim of this study was to optimise paediatric conventional radiology exams applying the ED without compromising the clinical diagnosis. METHODS: Automatic dose management software (ADMS) was used to analyse 2678 studies of children from birth to 5 years of age, obtaining local diagnostic reference levels (DRLs) in terms of entrance surface air kerma. Given local DRL for infants and chest exams exceeded the European Commission (EC) DRL, an optimisation was performed decreasing the kVp and applying the automatic control exposure...
March 14, 2018: British Journal of Radiology
Andreas Pfrommer, Anke Henning
PURPOSE: The ultimate intrinsic signal-to-noise ratio (UISNR) represents an upper bound for the achievable SNR of any receive coil. To reach this threshold a complete basis set of equivalent surface currents is required. This study systematically investigated to what extent either loop- or dipole-like current patterns are able to reach the UISNR threshold in a realistic human head model between 1.5 T and 11.7 T. Based on this analysis, we derived guidelines for coil designers to choose the best array element at a given field strength...
March 13, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Peiying Liu, Ying Qi, Zixuan Lin, Qiyong Guo, Xiaoming Wang, Hanzhang Lu
Abnormal cerebral blood flow (CBF) is implicated in several neonatal and infant diseases. However, measurement of CBF in this population remains difficult and has not been used in routine clinical MRI. Arterial spin labeling (ASL) methods suffer from both low SNR and poor quantification when applied to very young children. Furthermore, rapid change in brain physiology in this age range makes it difficult to choose sequence parameters such as labeling pulse flip angle and post labeling delay. Phase-contrast (PC) MRI is another approach to measure flow...
March 10, 2018: NeuroImage
Thomas Wesarg, Bettina Voss, Frederike Hassepass, Rainer Beck, Antje Aschendorff, Roland Laszig, Susan Arndt
OBJECTIVE: To investigate the impact of the wearing position of an off-the-ear-processor (OTE) on speech perception in quiet and noise. PATIENTS: The study group consisted of 16 adult subjects with bilateral severe-to-profound sensorineural hearing loss, 2 of them unilaterally, and 14 bilaterally provided with cochlear implants. MAIN OUTCOME MEASURES: Speech perception in quiet and noise was measured for frontal presentation with the recipients behind-the-ear processor CP810 or CP910 and the OTE processor Kanso (Cochlear Limited, Sydney, Australia)...
April 2018: Otology & Neurotology
Robert J Yawn, Brendan P O'Connell, Robert T Dwyer, Linsey W Sunderhaus, Susan Reynolds, David S Haynes, René H Gifford
OBJECTIVE: Evaluate performance and quality of life changes after sequential bilateral cochlear implantation in patients with preoperative residual hearing functioning in a bimodal hearing configuration. STUDY DESIGN: Retrospective analysis using within-subjects repeated measures design. SETTING: Tertiary otologic center. PATIENTS: Twenty-two adult patients with bilateral sensorineural hearing loss who used bimodal hearing before second cochlear implant (CI) meeting the following criteria: 1) preoperative residual hearing (≤80 dB HL at 250 Hz) in the ear to be implanted, 2) implantation with current CI technology (2013-2016), 3) consonant-nucleus-consonant (CNC) speech recognition testing in the bimodal condition preoperatively and bilateral CI condition postoperatively...
April 2018: Otology & Neurotology
Tarek Zghaib, Ashkan A Malayeri, Esra G Ipek, Mohammadali Habibi, Dong Huang, Muhammad A Balouch, David A Bluemke, Hugh Calkins, Saman Nazarian, Stefan L Zimmerman
BACKGROUND: Ablation-induced left atrial (LA) edema may result in procedural failure due to reversible pulmonary vein (PV) isolation. Conventional T2-weighted magnetic resonance edema imaging is limited by low spatial resolution. OBJECTIVE: In this pilot study, our goal was to 1) optimize and validate a 3D-SPACE sequence for quantification of T2-signal in the LA and 2) apply in recently ablated patients, comparing myocardial edema on T2-SPACE to tissue damage on late gadolinium-enhancement (LGE) imaging...
March 9, 2018: Heart Rhythm: the Official Journal of the Heart Rhythm Society
Miguel V Drummond, Vanessa C Duarte, André Albuquerque, Rogério N Nogueira, Leontios Stampoulidis, Georg Winzer, Lars Zimmermann, Stephen Clements, Javad Anzalchi
The design and dimensioning of a photonic-aided payload for a multi-beam high-throughput communications satellite is a complex problem in which the antenna, RF and photonic subsystems must be considered as a whole for achieving best performance with lowest mass and power consumption. In this paper, we propose and dimension the receiving stage of a communications satellite comprising a phased array antenna (PAA) feeding a multibeam photonic beamforming system (PBS). The PBS uses a single wavelength and resorts to heterodyne detection such that the retrieved beams are frequency downconverted...
March 5, 2018: Optics Express
Huan Wu, Liang Wang, Zhiyong Zhao, Nan Guo, Chester Shu, Chao Lu
We have experimentally analyzed and compared the performance of Brillouin optical time-domain analyzer (BOTDA) sensors assisted by non-local means (NLM) and wavelet denoising (WD) techniques in terms of measurement accuracy and experimental spatial resolution, respectively. Degradation of the measurement accuracy and experimental spatial resolution after denoising by NLM and WD are observed, which originate from the fact that higher signal-to-noise ratio (SNR) improvement is achieved at the expense of sacrificing the details of BOTDA data, and smaller data sampling point number (SPN) gives rise to insufficient redundant information for denoising...
March 5, 2018: Optics Express
Britta U Westner, Sarang S Dalal, Simon Hanslmayr, Tobias Staudigl
Single-trial analyses have the potential to uncover meaningful brain dynamics that are obscured when averaging across trials. However, low signal-to-noise ratio (SNR) can impede the use of single-trial analyses and decoding methods. In this study, we investigate the applicability of a single-trial approach to decode stimulus modality from magnetoencephalographic (MEG) high frequency activity. In order to classify the auditory versus visual presentation of words, we combine beamformer source reconstruction with the random forest classification method...
March 12, 2018: PLoS Computational Biology
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