Now showing items 26-45 of 90

      For this purpose,measurements in vitro were carried out using plastic flow phantom with the possibility to change the rate of constant flow. Spatial resolution was also altered. To simulate non-laminar flow,an artificial valve was inserted into the phantom tube. The error of eddy currents effect as well as its dependence on slice orientation was subsequently measured using a static gel phantom. Examination of two pacients,one with a healthy aortal valve and the other with a valve stenosis,were performed. These data were used to assess the error resulting from an under- and oversized ROI and from a temporal resolution.It was found out that the noise error (0.05%) of constant flow stroke volume is neglectable compared to flow fluctuations (0.25%). The partial volume effect resulted in more severe error (+0.45%) in the in vivo measurement. The error of eddy currents effect was not evaluated with certainty,we estimate a value of 3 %. An undersized ROI may result in fatal underestimation of stroke volume,whereas an oversized boundary leads to an error up to 6%. The non-laminar flow stroke volume error was of +8% in our case.The over-all error of all investigated effects combined remains below 10% for laminar flow. It is important to note,however,that not all possible sources of errors were examined and also that some of the erros were assessed in vitro only. Additionally,some of the measured data suggest a possibly not negligible stroke volume changes dependent on pacient's heart rate [1]
      gama spektrometrie [1]
      gamma spectrometry [1]
      HAVAR,atmosférické disperzní modelování,radiační ochrana,lokalizace,obyvatelstvo [1]
      HAVAR,atmospheric dispersion modeling,radiation protection,localization,population [1]
      In situ,gamma-ray spectrometry,GT-40,calibration [1]
      In situ,spektrometrie záření gama,GT-40,kalibrace [1]
      in-vivo dosimetry, off-line, proton therapy, PET/CT, activation analysis [1]
      in-vivo dozimetrie, off-line, protonová terapie, PET/CT, aktivační analýza [1]
      jaderná elektrárna,havárie,scintilační detektor,inventář radionuklidů,radiační monitorování [1]
      kalibrace,napětí na rentgence,neinvazivní měřič napětí,kVp metr,PPV,generátor vysokého napětí,rentgenový přístroj,radiodiagnostika [1]
      karcinom prostaty [1]
      Källman model [1]
      Källmanův model [1]
      klonogenní test [1]
      kovové artefakty [1]
      křivka přežití [1]
      Leksell gamma knife [1]
      Leksell gamma knife,dose rate,DAOY medulloblastoma cell line,clonogenic assay,ionizing radiation [1]
      Leksellův gama nůž [1]