465,708 research outputs found
User-initialized active contour segmentation and golden-angle real-time cardiovascular magnetic resonance enable accurate assessment of LV function in patients with sinus rhythm and arrhythmias.
BackgroundData obtained during arrhythmia is retained in real-time cardiovascular magnetic resonance (rt-CMR), but there is limited and inconsistent evidence to show that rt-CMR can accurately assess beat-to-beat variation in left ventricular (LV) function or during an arrhythmia.MethodsMulti-slice, short axis cine and real-time golden-angle radial CMR data was collected in 22 clinical patients (18 in sinus rhythm and 4 patients with arrhythmia). A user-initialized active contour segmentation (ACS) software was validated via comparison to manual segmentation on clinically accepted software. For each image in the 2D acquisitions, slice volume was calculated and global LV volumes were estimated via summation across the LV using multiple slices. Real-time imaging data was reconstructed using different image exposure times and frame rates to evaluate the effect of temporal resolution on measured function in each slice via ACS. Finally, global volumetric function of ectopic and non-ectopic beats was measured using ACS in patients with arrhythmias.ResultsACS provides global LV volume measurements that are not significantly different from manual quantification of retrospectively gated cine images in sinus rhythm patients. With an exposure time of 95.2Â ms and a frame rate ofâ>â89 frames per second, golden-angle real-time imaging accurately captures hemodynamic function over a range of patient heart rates. In four patients with frequent ectopic contractions, initial quantification of the impact of ectopic beats on hemodynamic function was demonstrated.ConclusionUser-initialized active contours and golden-angle real-time radial CMR can be used to determine time-varying LV function in patients. These methods will be very useful for the assessment of LV function in patients with frequent arrhythmias
Arms down cone beam CT hepatic angiography: are we focusing on the wrong target?
We read with great interest the recent article by Dr. Gonzalez-Aguirre and colleagues entitled ââArms Down Cone Beam CT Hepatic Angiography Performance Assessment: Vascular Imaging Quality and Imaging Artefactsââ [1]. One of the most important advantages of cone beam CT (CBCT) is the possibility to evaluate the lesionâs feeders assisting their identification and catheterization [2]. In this set, the patientâs arms positioning is crucial in order not to impair CBCT imaging. Dr. Gonzalez-Aguirre et al. had elegantly demonstrated that vesselsâ visualization is independent from the patientâs arms position, allowing to perform the entire procedure without patientâs movements. This minimizes the risk of contamination and reduces procedural time. However, literature shows that the major pivotal strength of CBCT, either mono-phasic or possibly bi-phasic, is the ability to depict in intra-procedurally ââoccult lesionsââ, not visible at pre-procedural second-line non-invasive imaging (MRI, MDCT) [3]. This ability is not just for show, but yield to some major clinical implications: the visualization of an occult nodule identifies a subset of population experiencing fast tumour growth, having consequences on the number of adjunctive treatments controlling tumour growth (adjunctive RFA, or TACE procedures) and prioritization for transplantation [4]. Moreover, bi-phasic CBCT, with its unique ability to intra-procedural permit nodule characterization, could help in patientsâ reclassification and real-time TACE strategy modification [5]. In this light would be a crucial interest for the audience to know whether the CBCT acquisition with arms down does not alter the diagnostic performance of the modality and ability of lesionâs characterization, especially for those lesion localized peripherally, where the beam hardening artefacts have been shown to be significant. Finally, patientâs positioning is fundamental for CBCT imaging. By acquiring the scan with patientâs arm down, liver volume would not be located within the rotation isocentre. This could be a substantial limitation for lesion located within the left liver lobe, eventually hypertrophied, and for high BMI patients
Realfast: Real-Time, Commensal Fast Transient Surveys with the Very Large Array
Radio interferometers have the ability to precisely localize and better
characterize the properties of sources. This ability is having a powerful
impact on the study of fast radio transients, where a few milliseconds of data
is enough to pinpoint a source at cosmological distances. However, recording
interferometric data at millisecond cadence produces a terabyte-per-hour data
stream that strains networks, computing systems, and archives. This challenge
mirrors that of other domains of science, where the science scope is limited by
the computational architecture as much as the physical processes at play. Here,
we present a solution to this problem in the context of radio transients:
realfast, a commensal, fast transient search system at the Jansky Very Large
Array. Realfast uses a novel architecture to distribute fast-sampled
interferometric data to a 32-node, 64-GPU cluster for real-time imaging and
transient detection. By detecting transients in situ, we can trigger the
recording of data for those rare, brief instants when the event occurs and
reduce the recorded data volume by a factor of 1000. This makes it possible to
commensally search a data stream that would otherwise be impossible to record.
This system will search for millisecond transients in more than 1000 hours of
data per year, potentially localizing several Fast Radio Bursts, pulsars, and
other sources of impulsive radio emission. We describe the science scope for
realfast, the system design, expected outcomes, and ways real-time analysis can
help in other fields of astrophysics.Comment: Accepted to ApJS Special Issue on Data; 11 pages, 4 figure
Real-Time Automatic Segmentation of Optical Coherence Tomography Volume Data of the Macular Region.
Optical coherence tomography (OCT) is a high speed, high resolution and non-invasive imaging modality that enables the capturing of the 3D structure of the retina. The fast and automatic analysis of 3D volume OCT data is crucial taking into account the increased amount of patient-specific 3D imaging data. In this work, we have developed an automatic algorithm, OCTRIMA 3D (OCT Retinal IMage Analysis 3D), that could segment OCT volume data in the macular region fast and accurately. The proposed method is implemented using the shortest-path based graph search, which detects the retinal boundaries by searching the shortest-path between two end nodes using Dijkstra's algorithm. Additional techniques, such as inter-frame flattening, inter-frame search region refinement, masking and biasing were introduced to exploit the spatial dependency between adjacent frames for the reduction of the processing time. Our segmentation algorithm was evaluated by comparing with the manual labelings and three state of the art graph-based segmentation methods. The processing time for the whole OCT volume of 496x644x51 voxels (captured by Spectralis SD-OCT) was 26.15 seconds which is at least a 2-8-fold increase in speed compared to other, similar reference algorithms used in the comparisons. The average unsigned error was about 1 pixel ( approximately 4 microns), which was also lower compared to the reference algorithms. We believe that OCTRIMA 3D is a leap forward towards achieving reliable, real-time analysis of 3D OCT retinal data
Potentials and limitations of real-time elastography for prostate cancer detection: a whole-mount step section analysis.
OBJECTIVES: To evaluate prostate cancer (PCa) detection rates of real-time elastography (RTE) in dependence of tumor size, tumor volume, localization and histological type.
MATERIALS AND METHODS: Thirdy-nine patients with biopsy proven PCa underwent RTE before radical prostatectomy (RPE) to assess prostate tissue elasticity, and hard lesions were considered suspicious for PCa. After RPE, the prostates were prepared as whole-mount step sections and were compared with imaging findings for analyzing PCa detection rates.
RESULTS: RTE detected 6/62 cancer lesions with a maximum diameter of 0-5âmm (9.7%), 10/37 with a maximum diameter of 6-10âmm (27%), 24/34 with a maximum diameter of 11-20â20 mm (70.6%), 14/14 with a maximum diameter of \u3e20âmm (100%) and 40/48 with a volume â„0.2âcm(3) (83.3%). Regarding cancer lesions with a volume â„ 0.2âcmÂł there was a significant difference in PCa detection rates between Gleason scores with predominant Gleason pattern 3 compared to those with predominant Gleason pattern 4 or 5 (75% versus 100%; P = 0.028).
CONCLUSIONS: RTE is able to detect PCa of significant tumor volume and of predominant Gleason pattern 4 or 5 with high confidence, but is of limited value in the detection of small cancer lesions
The design and testing of a novel compact real-time hybrid Compton and neutron scattering instrument.
The requirement for multiple-purpose imaging system occurs regularly within the field of radioactive materials safeguard and security applications. Current instrumentation utilised within the field of dual gamma-ray and neutron imaging systems suffer with limited portability, long scan times, and cover limited energy ranges. Conversely, the imaging system designed, built and tested in this work is not only capable of locating both gamma rays and neutrons, but is also capable of operating in near real time, covers a large energy range and is portable to a desktop degree. The imaging concept applied simultaneously combines Compton and neutron scattering techniques within a threelayer design comprising of a unique combination of scintillators backed with pixelated arrays of photodetectors in the form of 8 x 8 Silicon Photomultipliers (SiPMs). The system features the organic scintillator EJ-204, neutron sensitive lithium glass and thallium doped caesium iodide utilised along with associated SiPMs and front-end electronics, all enclosed within a volume of 120 mm x 120 mm x 200 mm. Further backend electronics is situated within a separate unit where each of the data channels are simultaneously interrogated in order to determine the location of the incident gamma rays and neutrons. The validity of the instrument has been computationally verified using MCNP6 and Geant4 Monte Carlo simulation codes and experimentally tested using Cs-137 gamma sources of ~300 kBq and a Cf-252 neutron source featuring an emission rate of 106 neutrons per second. The developed instrument offers a real-time response with a scan time of 60 seconds and a further data analysis time of 60 seconds. The intrinsic efficiency of the instrument has been experimentally measured to be in the order of 10-4 for both gamma rays at 0.667 MeV and fast neutrons at average energy of 2.1 MeV, and 0.78 for thermal neutron
Anisotropy techniques in study of cytoplasm
CĂlem tĂ©to prĂĄce bylo provĂ©st srovnĂĄvacĂ experimenty pomocĂ ÄasovÄ rozliĆĄenĂ© anizotropie a ustĂĄlenĂ© anizotropie v bakteriĂch kmene Cupriavidus necator. FluorescenÄnĂ sondou pro skenovĂĄnĂ bunÄÄnĂ©ho vzorku byl vybrĂĄn fluorescein, respektive jeho derivĂĄt BCECF_AM. PomocĂ ovÄĆovacĂho experimentu v systĂ©mu glycerol/voda s pĆĂdavkem fluoresceinu, byla ovÄĆena anizotropie a vypoÄĂtĂĄn molĂĄrnĂ hydrodynamickĂœ objem jednĂ© molekuly fluoresceinu, kterĂœ pĆibliĆŸnÄ odpovĂdal jeho reĂĄlnĂ© hodnotÄ. PomocĂ fluorescenÄnĂ anizotropnĂ mikroskopie byly zĂskĂĄny obrĂĄzky bakteriĂ s pĆĂsluĆĄnĂœmi stĆednĂmi hodnotami anizotropiĂ. Skeny bakteriĂ CN H16 a mutantĆŻ CN PHB-4, ukĂĄzaly patrnĂ© rozdĂly mezi uniformitou vnitĆnĂho prostĆedĂ.The main goal of this thesis was to compare experiments using time-resolved anisotropy and steady-state anisotropy for measuring in bacteria strain Cupriavidus necator. Fluorescent probe for anisotropy imaging was chosen BCECF_AM, which is derivate of fluorescein. Using experiment in system glycerol/water with fluorescein, anisotropy has been verified and calculated molecular hydrodynamic volume of a single fluorescein molecule, which approximately corresponded with real value. By using fluorescence imaging anisotropy microscopy, images and values of average anisotropy in cells were taken. Images of living cells (bacteria) of CN H16 and mutant CN PHB-4 showed differences, mainly in the uniformity of the inside environment.
Rapid Prototyping of Three-dimensional (3-D) Daubechies with Transpose-based Method for Medical Image Compression
This paper presents an efficient architecture for three-dimensional (3-D) Daubechies with transpose-based method for medical image compression. Daubechies 4-tap (Daub4) and Daubechies 6-tap (Daub6) are selected with pipelined direct mapping design technique. Due to the separability property of the multi-dimensional Daubechies, the proposed architectures have been implemented using a cascade of three N-point one-dimensional (1-D) Daub4/Daub6 and two transpose memories for a 3-D volume of N*N*N suitable for real-time 3-D medical imaging applications. The architectures were synthesised using VHDL and implemented on Altera®Cyclone II (EP2C35F672C6) field programmable gate array (FPGA). An in depth evaluation in terms of area, power consumption, maximum frequency and latency are discussed in this paper
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