Sirvi Autor "Kepler, Kalle" järgi

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Optimisation of patient doses and image quality in diagnostic radiology
(2009-08-17T06:05:28Z) Kepler, Kalle
Medical diagnostic radiation procedures make up the majority of the human exposure from artificial sources of ionising radiation. New digital technologies in medical radiology have the potential to reduce patient doses, but they also have the potential to significantly increase them without loss in image quality as shown by clinical surveys. In Estonia systematic data collection of patient doses for establishment and application of diagnostic reference levels (DRL) is not nationally regulated yet. This thesis was aimed to introduce new methods in dose and image quality optimisation, quality control of radiographic and fluoroscopic equipment and patient dosimetry in X-ray diagnostic radiology with emphasis on needs in Estonian hospitals, and to participate in the European clinical dosimetry surveys for estimating reference levels in typical interventional procedures. The work was carried out as a pilot study of physical approach for the dose and image quality optimisation, evaluating the performance of an automatic exposure control at different sensitivity settings when used with a computed radiography system. The tests were designed to investigate image quality, using threshold contrast-detail detectability (TCDD) and signal-to-noise ratio squared related to dose at different sensitivities and X-ray tube potential values. The optimum speed modes and optimal settings to be used in the radiography examination programmes were proposed. In cooperation with other European partners under the SENTINEL consortium the performance characteristics of digital fluoroscopic and cardiac angiography systems were investigated and compared in seven European countries, also reference levels for some typical interventional radiology procedures were estimated. The survey performed on interventional cardiology in a sample of European centres demonstrated the presence of a large variability in the entrance surface air kerma rates for both fluoroscopy (more than 7 times) and image acquisition (more than 5 times) modes. For the first time, reference levels for these quantities are proposed to be used in the process of optimisation of patient exposure. Suurima osa kõigi kasutuselolevate tehisallikate ioniseeriva kiirguse doosidest annavad meditsiinidiagnostilised kiiritusprotseduurid. Uued digitaaltehnoloogiad meditsiiniradioloogias võimaldavad patsiendidoosi vähendada, kuid piisavate ohjemeetmete puudumisel võib doos hoopis kasvada. Eestis puudub senini süstemaatiline patsiendidoosi registreerimise ja diagnostiliste referentsväärtuste (DRL) määramise riiklikult reguleeritud süsteem, kuigi see on nõutav Euroopa direktiividega. Käesoleva doktoriväitekirja eesmärgiks oli kasutusele võtta ja arendada uusi meetodeid patsiendidoosi ja pildi kvaliteedi optimeerimisel, röntgenülesvõtte- ja läbivalgustusaparatuuri kvaliteedikontrollil ja patsiendidosimeetrias, lähtudes Eesti haiglate vajadustest, ning ühtlasi võtta osa Euroopa kliinilise dosimeetria uuringutest menetlusradioloogia referentsväärtuste hindamisel. Uurimistöö teostati füüsikalise lähenemisviisi pilootuuringuna doosi ja pildi kvaliteedi optimeerimisel, hinnates röntgenseadme automaatekspositsioonisüsteemi toimivust erinevates tundlikkusrežiimides koos kasutatava kompuuterradiograafia süsteemiga. Katsetes mõõdeti pildi kvaliteedi parameetritena lävikontrastsus-teravust (TCDD) ja signaal-müra-suhte ruudu ning doosi suhet röntgenseadme erinevate tundlikkuste ja röntgentoru pingete korral. Pildi evalveerimistulemuste põhjal soovitati kasutada optimaalseid tundlikkusrežiime ja talitlusparameetreid. Koostöös SENTINEL konsortsiumi teiste Euroopa partneritega uuriti ja võrreldi digitaalfluoroskoopia ja kardioangiograafia süsteemide toimimisnäitajaid seitsme riigi haiglates, samuti hinnati referentsväärtusi mõnedes tüüpilistes menetlusradioogia protseduurides. Menetluskardioloogias läbi viidud uuringud näitasid suuri erinevusi uuringus osalenud keskuste vahel sisendõhukerma kiiruses nii läbivalgustusrežiimi (üle 7 korra) kui ka pildihõiverežiimi (üle 5 korra) korral. Esmakordselt on patsiendidoosi optimeerimisel soovitatud eelnimetatud suuruste väärtusi kasutada referentsväärtustena.
Testing of buffy coat platelet concentrate pathogen inactivation by Intercept double-dose system in North Estonia Medical Centre´s Blood Centre
(Tartu Ülikool, 2017) Loot, Mari; Kepler, Kalle; Tartu Ülikool. Loodus- ja täppisteaduste valdkond
The aim of this thesis was to develop a method for production of buffy coat platelet concentrates suitable for use with Intercept platelet processing set with dual-storage containers and to assess the conformity of pathogen inactivated platelet products with the required and recommended quality parameters. The validation of platelet concentrate production using six buffy coats proved the conformity to requirements for platelet content, volume, plasma content, and red blood cell concentration set for platelet concentrates suitable to be processed with Intercept system. After processing with Intercept system, the platelet and white blood cell content were assessed to be appropriate. A little concern was the lower than recommended amount of volume per platelet content in about half of the products, but as those were the units containing about average or higher platelet content and storage analysis showed good platelet recovery and normal pH values at the end of shelf-life, the overall results for volume were also considered to be acceptable. Both the platelet concentrate production and Intercept treatment process were evaluated to be efficient in terms of platelet recovery.