Comparison of exposure conditions for DR and CR imaging (electronic exposure control)

Uvod: Slikovne sprejemnike delimo na analogne in digitalne. K analognim slikovnim sprejemnikom prištevamo rentgenski film, ki so jih danes skoraj v popolnosti nadomestili digitalni sprejemniki. Ti se delijo na CR detektorje (fluorescenčne plošče) in DR detektorje (CCD, CMOS, flat panel detektor). Za odčitavanje CR slike potrebujemo CR čitalec, ki omogoča da latentna slika postane vidna. Digitalno radiografijo delimo na direktno ali neposredno in indirektno ali posredno. Namen: Namen diplomske naloge je ugotoviti razlike v ekspozicijskih pogojih in kakovosti slike pri uporabi obeh sistemov z elektronskim nadzorom ekspozicije. Metode dela: V diplomskem delu sva v prvem delu uporabila opisno ali deskriptivno metodo, s pregledom domače in tuje strokovne literature. V drugem delu sva uporabila eksperimentalno metodo dela, kjer sva izvajala meritve v laboratoriju Zdravstvene fakultete v Ljubljani. Ob uporabi CR in DR detektorja sva primerjala ekspozicijske pogoje pri osnovnih projekcijah slikanja roke PA, stopala stransko in gležnja AP. Za vsako projekcijo sva nastavila anodno napetost (45 kV, 50 kV in 55 kV), produkt toka in časa pa sva izbrala glede na EI. Odčitavala in beležila sva DAP in EI, nato sva podatke računalniško obdelala in jih prikazala v tabelah. Rezultati: Rezultati meritev kažejo, da smo morali produkt toka in časa pri DR povečati v primerjavi z CR, za dosego EI 250, pri enakih objektih slikanja. Najvišji dvig mAs smo zabeležili pri slikanju roke PA z 55 kV za 42,9%, pri slikanju stopala stransko z 50 kV za 40% in pri slikanju gležnja AP z 45 kV za 77%. Najvišjo dozo bi pacient v našem primeru prejel pri slikanju gležnja AP, najnižjo pa pri slikanju roke PA. Po primerjavi kakovosti obeh rentgenogramov, narejenih na CR in DR detektorjih lahko razberemo, da je kakovost rentgenogramov narejenih na DR boljša. Razprava in zaključek: Po pregledu do sedaj obstoječe literature na to temo, smo ugotovili, da EI najbrž ni pravilno nastavljen na enem od sistemov na fakulteti, saj bi morala biti doza na DR nižja kot na CR za enako kakovost slike. Odstopanja v nastavitvi produkta toka in časa bi bila manjša, če bi rentgenski aparat omogočal nastavitve točno določene vrednosti le- tega, za približanje ekspozicijskemu indeksu 250. Boljšo kakovost DR rentgenogramov pripisujemo uporabi višjemu produktu toka in časa ter boljši programski opremi za obdelavo slik pri DR sistemu.ntroduction: Image receptors are divided into analog and digital. Analog image receptors include X-ray film, which has been almost completely replaced by digital receptors today. These are divided into CR detectors (fluorescent plates) and DR detectors (CCD, CMOS, flat panel detector). To read a CR image we need a CR reader which allows the latent image to become visible. Digital radiography is divided into direct and indirect radiography. Purpose: The purpose of the diploma thesis is to determine the differences in exposure conditions and image quality when using both systems with electronic exposure control. Methods: In the first part of the diploma work we used a descriptive method, with a review of domestic and foreign academic literature. In the experimental part, we performed measurements in the laboratory of the Faculty of Health Sciences in Ljubljana. Using a CR and DR detector, we compared the exposure conditions for the basic imaging projections of the hand in PA, the foot in LAT, and the ankle in AP projection. For each projection we set the anode voltage (45 kV, 50 kV and 55 kV), and the tube current time product was selected according to EI. We read and recorded DAP and EI, then computer-processed the data and displayed it in tables. Results: The results of the measurements show that we had to increase the tube current time product at DR compared to CR, to achieve EI 250, at the same imaging objects. The highest increase in mAs was recorded in the imaging of the hand PA arm with 55 kV by 42.9%, in the imaging of the foot lateral with 50 kV by 40% and in the imaging of the ankle AP with 45 kV by 77%. The highest dose in our case would be received by the patient when imaging the ankle AP and the lowest when imaging the hand PA. After comparing the quality of both radiographs made on CR and DR detectors, we can see that the quality of radiographs made on DR is better. Discussion and conclusion: After reviewing the existing literature on this topic, we found that the EI is presumably not set correctly on one of the systems at the faculty, as the dose on DR should be lower than on CR for the same image quality. Deviations in the setting of the tube current time product would be smaller if the X-ray machine could adjust the exact value of it, to approach the exposure index of 250. Better quality of radiographs made on DR are attributed to the use of higher tube current time product and better DR image processing software system