This is achieved by using amplifiers with the highest possible frequency response which, in other words, means the use of the shortest integration and differentiation time-constants. Whether this system is used or not it is always important to obtain the best possible signal to noise ratio. To facilitate this discrimination, it is often advantageous to use two phototubes operating in a fast coincidence circuit. Hence in general it is not possible to measure with any accuracy the amount of light from a single particle and it is necessary to observe a large number of events of the same type and to obtain a pulse height distribution to indicate the size of the light pulses.Īs has already been stated, Čerenkov light signals are in general considerably smaller than those from scintillation crystals, so that it is particularly important to be able to discriminate against the background of dark current pulses from the phototube, which may themselves have a very broad pulse-height distribution. In a photomultiplier the statistical spread in the pulse size at the output depends, for a given incident flux of photons at the cathode, on the number of electrons emitted there, and also on the gain per stage, for there are fluctuations in the secondary emission ratio which in turn produce some broadening of the pulse-size distribution. This arises because the light, by suitable arrangements, may be more easily gathered into one general direction towards the phototube in the Čerenkov case, and most scintillation media strongly absorb their own radiations, thus setting a limit to the useful size of the radiator. To some extent, however, some compensation is often possible if the path length of the particle in the radiator can be lengthened by increasing the size of the latter. The conditions to be met here are in general rather more stringent than for scintillation counters, for the light output from a Čerenkov counter may be only ∼1% of that from a scintillator of the same dimensions. A small spread in transit-time, which follows in general from short-transit-time, is also desirable. The shortest possible transit-times should be aimed at if accurate time-measurements are required. (v)Ī tube should be selected which has a low thermionic noise, to minimize noise “pile-up”. The overall gain should be high on account of the relatively small amount of light in general available at the cathode, to avoid the necessity of large amplification after the phototube. The photocathode should be of the translucent type, evaporated on to the envelope of the tube so that optical contact may be achieved between the tube and the radiator, for maximum optical efficiency. it should respond to the blue end of the spectrum and preferably extend as far as possible into the ultra-violet. The spectral response curve should fit as closely as possible that of the light-spectrum of the Čerenkov radiation, i.e. Colli & Casazza, Internal Medicine Department, Ospedale A Manzoni, Lecco, Italy Department of Biomedical and Clinical Sciences “L.A phototube should possess the following properties if one is to obtain the best performance from the detector: (i)Ī photocathode of high photon efficiency so that the maximum number of electrons may be produced by the available light-signal. Panoulas & Nihoyannopoulos, Hammersmith Hospital, Imperial College Healthcare NHS Trust and Imperial College London, London, UK Pocket-Size Hand-Held Cardiac Ultrasound as an Adjunct to Clinical Examination in the Hands of Medical Students and Junior Doctors European Heart Journal of Cardiovascular Imaging, 2013 PubMed ID (PMID) 22833550ģ. Razi & Spencer, University of Chicago, Chicago, Illinois – USA Bedside Hand-Carried Ultrasound by Internal Medicine Residents Versus Traditional Clinical Assessment for the Identification of Systolic Dysfunction in Patients Admitted with Decompensated Heart Failure Journal of the American Society of Echocardiography, 2011 PubMed ID (PMID) 21885245Ģ. IP67 waterproof, compatible with high-level disinfection techniques.ġ. ***Vscan Air probe withstand drops: tested to Military drop standards (MIL-810G). Use is restricted to environmental properties described in the user manual. ** The device has been verified for limited use outside of professional healthcare facilities. Filopei & Kory 2014 – Impact of Pocket Ultrasound Use by Internal Medicine House Staff in the Diagnosis of Dyspnea Maw & Soni 2018 – Inpatient Notes: Why Should Hospitalists Use Point-of-Care Ultrasound? – Annals for Hospitals *Andersen & Dalen – Diagnostic Influence of Routine Point-of-Care Pocket-size Ultrasound Examinations Performed by Medical Residents – J Ultrasound Med.
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