Point detectors
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PURPOSE: Point detectors are frequently used to measure patient's maximum skin dose (MSD) in fluoroscopically-guided interventional procedures (IP). However, their performance and ability to detect the actual MSD are rarely evaluated. The present study investigates the sampling uncertainty associated with the use of grids of point detectors to measure MSD in IP. METHOD: Chemoembolisation of the liver (CE), percutaneous coronary intervention (PCI) and neuroembolisation (NE) procedures were studied. Spatial dose distributions were measured with XR-RV3 Gafchromic(®) films for 176 procedures. These distributions were used to simulate measurements performed using grids of detectors such as thermoluminescence detectors, with detector spacing from 1.4 up to 10 cm. RESULTS: The sampling uncertainty was the highest in PCI and NE procedures. With 40 detectors covering the film area (36 cm × 44 cm), the maximum dose would be on average 86% and 63% of the MSD measured with Gafchromic(®) films in CE and PCI procedures, respectively. In NE procedures, with 27 detectors covering the film area (14 cm × 35 cm), the maximum dose measured would be on average 82% of the MSD obtained with the Gafchromic(®) films. CONCLUSION: Thermoluminescence detectors show good energy and dose response in clinical beam qualities. However the poor spatial resolution of such point-like dosimeters may far outweigh their good dosimetric properties. The uncertainty from the sampling procedure should be estimated when point detectors are used in IP because it may lead to strong underestimation of the MSD.
Exhaled breath condensate (EBC) is an attractive, non-invasive sample for clinical diagnostics. During EBC collection, its composition is influenced by the collection temperature, a factor that is often not thoroughly monitored and controlled. In this study, we assembled a novel, simple, portable, and inexpensive device for EBC collection, able to maintain a stable temperature at any value between -7 °C and +12 °C. The temperature was controlled using a microcontroller and a thermoelectric cooler that was employed to cool the aluminum block holding the glass tube or the polypropylene syringe. The performance of the novel sampler was compared with the passively cooled RTube™ and a simple EBC sampler, in which the temperature was steadily increasing during sampling. The developed sampler was able to maintain a stable temperature within ±1 °C. To investigate the influence of different sampling temperatures (i.e., +12, -7, -80 °C) on the analyte content in EBC, inorganic ions and organic acids were analyzed by capillary electrophoresis with a capacitively coupled contactless conductivity detector. It was shown that the concentration of metabolites decreased significantly with decreasing temperature. The portability and the ability to keep a stable temperature during EBC sampling makes the developed sampler suitable for point-of-care diagnostics.
The review focuses on the design of detection cells, the use of microcontrollers for processing and evaluation of the detection signal, and the development of multi-detection systems for electromigration, liquid chromatography, flow-through and microfluidic techniques. A separate section is the introduction of modern 3D printing techniques and the use of new printing materials for the design of multidetection systems. In addition to traditional utilisation in separation techniques, new versions of contactless conductivity detectors are finding applications in FIA, SIA, portable and paper based analytical systems or as independent sensors. Applicationwise, C4Ds find new use in gas detection, segmented flow monitoring, as part of point of care devices, and in many other biomedical, environmental, agricultural and industrial applications.
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
A precise model of a 40% relative efficiency p-type HPGe detector was created for photon detection efficiency calculation using the MCNP code. All detector parameters were determined by different experiments. No experimental calibration points were used for the modification of detector parameters. The model was validated by comparing calculated and experimental full energy peak efficiencies in the 40-2754 keV energy range, for point-source geometry with the source-to-detector distance of 25 cm.
- MeSH
- algoritmy MeSH
- analýza selhání vybavení MeSH
- chemické modely MeSH
- dávka záření MeSH
- design s pomocí počítače MeSH
- design vybavení MeSH
- metoda Monte Carlo MeSH
- molekulární modely MeSH
- počítačová simulace MeSH
- radiometrie metody přístrojové vybavení MeSH
- radionuklidy analýza MeSH
- reprodukovatelnost výsledků MeSH
- senzitivita a specificita MeSH
- spektrometrie gama metody přístrojové vybavení MeSH
- statistické modely MeSH
- vztah dávky záření a odpovědi MeSH
- záření gama MeSH
- Publikační typ
- hodnotící studie MeSH
Článek se věnuje návrhu automatického detektoru vybraných arytmií. Navržený algoritmus využívá spojitou vlnkovou transformaci (CWT) v kombinaci s analýzou její konturové obálky. Vlnková transformace byla využita v detektoru R vln, k rozlišení normálních a abnormálních stahů a pro detekci předčasných atriálních kontrakcí (APC) a předčasných komorových kontrakcí (PVC). Algoritmus byl ověřen rozsáhlým testováním na MIT/BIH databázi. Hledáním lokálních maxim ve vlnkové konturové obálce jsou účinně detekovány R vlny. Celková úspěšnost detekce testovaná na 48 půlhodinových signálech je 99,5 %. Byly otestovány dva typy klasifikace: 1. klasifikace založená na konturové obálce a detekci význačných bodů s celkovou úspěšností 94,6 %, 96,1 % pro sinusový rytmus (SR), 30,4 % pro APC, 71,2 % pro PVC a 2. lokalizace maxima umocněných koeficientů spojité vlnkové transformace v oblasti QRS komplexu k určení PVC mezi SR, blokádou pravého Tawarova raménka (RBBB), APC a dalšími arytmiemi s úzkým QRS komplexem s přesností 96,8 %.
This paper deals with design of an automatic detector for classification of selected cardiac arrhythmias. The proposed algorithms employ the continuous wavelet transform (CWT) combined with an analysis of its contour envelopes. The CWT was used in a detector of R-waves, to distinguish between normal and abnormal beats, and for detection of atrial premature contractions (APCs) and premature ventricular contractions (PVCs). The algorithm was validated by extensive testing on the MIT/BIH database. Searching for a local maximum in wavelet contour envelopes efficiently detects R-peaks. The overall accuracy of its detection tested on 48 half-hour signals is 99.5%. Two types of classifications were tested: 1. classification based on the contour envelope and the detection of significant points with overall accuracy 94.6%, 96.1% for the sinus rhythm (SR), 30.4% APCs, 71.2% PVCs and 2. the localization of maximum of square modulus of CWT coefficients in the area of QRS complex for the determination of PVCs between SR, right bundle branch block (RBBB), APC and other narrow complex arrhythmias with the accuracy 96.8%.
- Klíčová slova
- EKG signál, vlnková transformace, kontury,
- MeSH
- algoritmy MeSH
- automatizované zpracování dat metody přístrojové vybavení MeSH
- diagnóza počítačová metody přístrojové vybavení MeSH
- elektrokardiografie klasifikace přístrojové vybavení MeSH
- financování organizované MeSH
- komorové extrasystoly diagnóza MeSH
- lidé MeSH
- počítačové zpracování signálu přístrojové vybavení MeSH
- reprodukovatelnost výsledků MeSH
- síňové extrasystoly diagnóza MeSH
- srdeční arytmie diagnóza klasifikace MeSH
- Check Tag
- lidé MeSH
OBJECTIVES: to assess the feasibility of CT with an integrated photon-counting-detector system (PC-CT) in the body imaging of clinical patients. METHODS: 120 examinations using photon counting detector CT were evaluated in six groups: 1/ a standard-dose lung, 2/ low-dose lung, 3/ ultra-high resolution (UHR) lung, 4/ standard-dose abdominal, 5/ lower-dose abdominal, 6/ UHR abdominal CTA. All CT examinations were performed on a single-source prototype device equipped with a photon counting detector covering a 50 cm scan field of view. Standard dose examinations were performed with the use of detector element size of 0.4 mm, ultra-high-resolution examinations with the detector element size of 0.2 mm, respectively. The stability of the system during imaging was tested. The diagnostic quality of the acquired images was assessed based on the imaging of key structures and the noise level in five-point scale, the effective dose equivalent, dose length product and noise level, and also relation to body mass index and body surface area were compared with three similar groups of CT images made with energy integrating high end scanner. The parameters were evaluated using Wilcoxon test for independent samples, the independence was tested using Kruskal-Wallis test. RESULTS: When PC-CT images radiation dose is compared with the similar imaging using energy integrating CT, the PC-CT shows lower dose in ultra-high resolution mode, the dose is significantly lower (p < 0.0001), the standard dose examinations were performed with the comparable radiation doses. PC-CT exhibited the significantly higher ratio between parenchyma signal and background noise both in lung and in abdominal imaging (p < 0.0001). CONCLUSIONS: PC-CT showed imaging stability and excellent diagnostic quality at dose values that are comparable or better to the quality of energy integrating CT, the better signal and improved resolution is most important advantage of photon counting detector CT over energy integrating detector CT.
- MeSH
- fantomy radiodiagnostické MeSH
- fotony * MeSH
- lidé MeSH
- plíce MeSH
- počítačová rentgenová tomografie * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
... OBJECTS 495 -- 9.6.1 Ideal thin lens 495 -- 9.6.2 Imaging a monochromatic point source 498 -- 9.6.3 ... ... PROCESSES 649 -- 11.3.1 Temporal point processes 649 -- 11.3.2 Spatial point processes 651 -- 11.3.3 ... ... Mean and autocorrelation of point processes 653 -- 11.3.4 Relation between Poisson random vectors and ... ... of filtered point processes 665 -- 11.3.11 Spectral properties of point processes 669 -- 11.4 RANDOM ... ... Semiconductor detector arrays 764 -- 12.3.4 Position and energy estimation with semiconductor detectors ...
Wiley series in pure and applied optics
[1st ed.] xli, 1540 s. : il.
BACKGROUND: Electronic brachytherapy (eBT) is considered a safe treatment with good outcomes. However, eBT lacks standardized and independent dose verification, which could impede future use. PURPOSE: To validate the 3D dose-to-water distribution of an electronic brachytherapy (eBT) source using a small-volume plastic scintillation detector (PSD). METHODS: The relative dose distribution of a Papillon 50 (P50) (Ariane Medical Systems, UK) eBT source was measured in water with a PSD consisting of a cylindrical scintillating BCF-12 fiber (length: 0.5 mm, Ø: 1 mm) coupled to a photodetector via an optical fiber. The measurements were performed with the PSD mounted on a motorized stage in a water phantom (MP3) (PTW, Germany). This allowed the sensitive volume of the PSD to be moved to predetermined positions relative to the P50 applicator, which pointed vertically downward while just breaching the water surface. The percentage depth-dose (PDD) was measured from 0 to 50 mm source-to-detector distance (SDD) in 1-3 mm steps. Dose profiles were measured along two perpendicular axes at five different SDDs with step sizes down to 0.5 mm. Characterization of the PSD consisted of determining the energy correction through Monte Carlo (MC) simulation and by measuring the stability and dose rate linearity using a well-type ionization chamber as a reference. The measured PDD and profiles were validated with corresponding MC simulations. RESULTS: The measured and simulated PDD curves agreed within 2% (except at 0 mm and 43 mm depth) after the PSD measurements were corrected for energy dependency. The absorbed dose decreased by a factor of 2 at 7 mm depth and by a factor of 10 at 26 mm depth. The measured dose profiles showed dose gradients at the profile edges of more than 50%/mm at 5 mm depth and 15%/mm at 50 mm depth. The measured profile widths increased 0.66 mm per 1 mm depth, while the simulated profile widths increased 0.74 mm per 1 mm depth. An azimuthal dependency of > 10% was observed in the dose at 10 mm distance from the beam center. The total uncertainty of the measured relative dose is < 2.5% with a positional uncertainty of 0.4 mm. The measurements for a full 3D dose characterization (PDD and profiles) can be carried out within 8 h, the limiting factor being cooling of the P50. CONCLUSION: The PSD and MP3 water phantoms provided a method to independently verify the relative 3D dose distribution in water of an eBT source.
- MeSH
- brachyterapie * MeSH
- elektronika MeSH
- metoda Monte Carlo MeSH
- plastické hmoty MeSH
- radiometrie MeSH
- voda MeSH
- Publikační typ
- časopisecké články MeSH
OBJECTIVE: High-frequency oscillations are considered among the most promising interictal biomarkers of the epileptogenic zone in patients suffering from pharmacoresistant focal epilepsy. However, there is no clear definition of pathological high-frequency oscillations, and the existing detectors vary in methodology, performance, and computational costs. This study proposes relative entropy as an easy-to-use novel interictal biomarker of the epileptic tissue. METHODS: We evaluated relative entropy and high-frequency oscillation biomarkers on intracranial electroencephalographic data from 39 patients with seizure-free postoperative outcome (Engel Ia) from three institutions. We tested their capability to localize the epileptogenic zone, defined as resected contacts located in the seizure onset zone. The performance was compared using areas under the receiver operating curves (AUROCs) and precision-recall curves. Then we tested whether a universal threshold can be used to delineate the epileptogenic zone across patients from different institutions. RESULTS: Relative entropy in the ripple band (80-250 Hz) achieved an average AUROC of .85. The normalized high-frequency oscillation rate in the ripple band showed an identical AUROC of .85. In contrast to high-frequency oscillations, relative entropy did not require any patient-level normalization and was easy and fast to calculate due to its clear and straightforward definition. One threshold could be set across different patients and institutions, because relative entropy is independent of signal amplitude and sampling frequency. SIGNIFICANCE: Although both relative entropy and high-frequency oscillations have a similar performance, relative entropy has significant advantages such as straightforward definition, computational speed, and universal interpatient threshold, making it an easy-to-use promising biomarker of the epileptogenic zone.
The main advantage of confocal microscopes over their conventional counterparts arises from their ability to optically 'section' nearly transparent materials; the thin image slices thus obtained can be used to reconstruct three-dimensional images, a capability which is particularly useful for the study of biological specimens. Confocal microscopes have previously used either a single laser-illuminated point-source and single point-detector (which are scanned in tandem across the object) or white-light illumination with multiple point-sources and detectors. Single-point-source systems, however, do not usually form images in real time and are restricted to using available laser wavelengths. Multiple-point-source systems, on the other hand, produce images in real time but use light very inefficiently--typically 1% or less is used for imaging. Here we demonstrate a white-light, multiple-point-source method which can in principle produce images in real time with light efficiencies as high as 50%. This system is likely to find broad practical application, particularly in the imaging of weakly reflecting or weakly fluorescent specimens.
- MeSH
- konfokální mikroskopie * přístrojové vybavení MeSH
- myši MeSH
- osteoklasty cytologie MeSH
- světlo MeSH
- thalamus anatomie a histologie MeSH
- velryby MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- práce podpořená grantem MeSH
