Primerjava vrednosti atenuacijskih koeficientov na enospektralnih nativnih in dvospektralnih virtualnih nativnih CT slikah abdomna : magistrsko delo

Jerman, Anja (author), Škrk, Damijan (mentor), Mekiš, Nejc (comentor), Žontar, Dejan (reviewer)

Uporaba ionizirajočega sevanja za diagnostične namene in zdravljenje bolezni je nenadomestljivo. Število preiskav z računalniško tomografijo (CT) se povsod po svetu hitro povečuje. Doze pri CT so v primerjavi s klasično rentgensko preiskavo veliko večje, posledično se tudi izpostavljenost pacientovsevanju pri povečuje. Epidemiološke študije so pokazale povezavo med izpostavljenostjo sevanju in povečanim tveganjem za razvoj določenih vrst raka. Pacient, ki je napoten na trifazno CT slikanje abdomna v povprečju prejme efektivno dozo 10,3 mSv. V Sloveniji znaša povprečna letna doza sevanja iz naravnega ozadja približno 2,64 mSv, to pomeni, da pacient po opravljenem trifaznem CT slikanju abdomna prejme skoraj štirikratno letno dozo sevanja. Namen: Namen magistrskega dela je primerjava atenuacijskih vrednosti (Hounsfieldove enote, HU) med nativnimi in virtualnimi nativnimi CT slikami abdomna in oceniti, za koliko bi lahko zmanjšali dozo, če bi opustili nativno fazo slikanja. Metode dela: Raziskava je potekala na Univerzitetni kliniki za pljučne bolezni in alergijo Golnik, kjer so pacienti opravili trifazno CT slikanje abdomna. Raziskavo smo opravili na CT aparatu Somatom Drive (Siemens Healthineers, Erlangen, Nemčija) po prilagojenem protokolu in sicer: nativno in arterijsko fazo smo pridobili s klasičnim enospektralnim slikanjem. Vensko fazo pa smo pridobili z dvospektralnim načinom slikanja (dual energy), pri kateri nam naknadna obdelava podatkov omogoča subtrakcijo joda iz serije venskih slik s čimer pridobimo virtualne nativne slike. Slike smo analizirali tako, da smo področje merjenja (ROI) enake velikosti postavili na enako mesto tako na nativni sliki (NS) kot na virtualni nativni sliki (VNC). Vrednosti HU smo izmerili v jetrih, vranici, desni ledvici, levi ledvici, desni nadledvičnici, levi nadledvičnici, aorti, podkožnem maščevju in mišici. Rezultati: Pomembno merilo za klinično uporabo VNC slik je, da so primerljiva z nativnimi slikami. Analiziranih je bilo 918 ROI-jev. Visoka primerljivost HU med NS in VNC rekonstrukcijo je bila dokazana za vsa analizirana tkiva razen za podkožno maščevje. Povprečna razlika v HU med NS in VNC sliko je bila manj kot ±10 HU za vsa analizirana tkiva razen maščobe. Razprava in zaključek: Dozo sevanja bi lahko zmanjšali za 25 % (v kolikor slikamo področje zgornjega abdomna), če bi se izognili nativnem slikanju in bi nativne slike pridobili s subtrakcijo joda iz venske faze. VNC slike bi lahko bile v prihodnosti alternativa NS, vendar so za to potrebne še nekatere nadaljnje raziskave. Potrebno je oceniti kakovost rekonstruiranih VNC slik na večjem vzorcu pacientov (v naši raziskavi se je kvalitativno ocenilo le 10 VNC rekonstrukcij) ter primerljivost HU med NS in VNC sliko pri karakterizaciji lezij malignega in benignega izvora (adenomi, ciste, metastaze) ter krvavitvah.

• Language: Slovenian
• Keywords: magistrska dela, radiološka tehnologija, računalniška tomografija, dvospektralna računalniška tomografija, virtualne nekontrastne slike, CT števila, CT trebušnih organov
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: ZF - Faculty of Health Sciences
• Place of publishing: Ljubljana
• Publisher: [A. Jerman]
• Year: 2023
• Number of pages: 73 str., [5] str. pril.
• PID: 20.500.12556/RUL-151065
• UDC: 616-07
• COBISS.SI-ID: 167285507
• Publication date in RUL: 28.09.2023

JERMAN, Anja, 2023, Primerjava vrednosti atenuacijskih koeficientov na enospektralnih nativnih in dvospektralnih virtualnih nativnih CT slikah abdomna : magistrsko delo [online]. Master’s thesis. Ljubljana : A. Jerman. [Accessed 23 April 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=151065

Secondary language

• Language: English
• Title: Comparison of attenuation values in single energy true non-contrast and dual energy virtual non-contrast CT images of abdomen : master thesis

Abstract

Introduction: Ionizing radiation is extensively used in medicine and its contribution to both diagnosis and therapy is undisputable. The number of computed tomographic (CT) studies performed is rapidly increasing. Because CT scans involve much higher doses of radiation than plain films, there is a marked increase of radiation exposure in the general population. Epidemiologic studies shown an association between radiation exposure and increased risk of developing cancers. A patient who underwent a triphasic CT scan of the abdomen receives an average effective dose of 10. 3 mSv. In Slovenia, the average annual background radiation dose is about 2. 64 mSv, which means that a patient receives almost four times the annual radiation dose after a three-phase CT scan of the abdomen.Purpose: The purpose of this study is to compare attenuation measurements (Hounsfield units, HU) of virtual unenhanced images (VNC) with those of conventional non contrast images (NC) of abdominal tissues and to assess potential reduction in radiation dose. Methods: The study involved patients who underwent three-phase abdominal imaging at the University Clinic Golnik. Study was performed on a Somatom Drive CT scanner (Siemens Healthineers, Erlangen, Germany) using a modified protocol: the native phase and the arterial phase were acquired using conventional single-spectral imaging (helical imaging). The venous phase was acquired using dual energy imaging, where post-processing allows us to subtract iodine from a series of venous images. The images were analysed by placing a region of interest (ROI) of the same size in the same position in both the NS and VNC images. HU values were measured on liver, spleen, right kidney, left kidney, right adrenal, left adrenal, aorta, subcutaneous adipose tissue and muscle. Results: An important criterion for clinical use of VNC images is that they are comparable to non contrast images. 918 ROIs were analysed. The high accuracy of HU between NC images and VNC images was demonstrated for all tissues except subcutaneous adipose tissue. The average difference between NC and VNC image was less than 10 HU for all tissues except subcutaneous adipose tissue. Discussion and conclusion: The radiation dose could be reduced by 25.1 % by avoiding native phase and using the VNC algorithm to acquire the native images. VNC images could be alternative to NS in the future, but further research is needed. It is necessary to assess the quality of reconstructed VNC images and their diagnostic value in characterising lesions of malignant and benign origin (adenomas, cysts, metastases, bleeding).

• Keywords: master's theses, radiologic technology, computed tomography, dual energy CT, virtual unenhanced images, Hounsfield units, abdominal CT