7,052 research outputs found
Application of CT in Diagnosing Carcinoma of the Maxillary Sinuses : PART 2: An Experimental Study of Pitfalls Encountered when Diagnosing Carcinoma of the Maxillary Sinuses with CT
No full text1982-03A phantom simulating the transverse section of the maxillary sinuses was constructed for experimentation with various CT scanners to study the following: (1) the occasional inability to image the very thin posterior-lateral walls which have no real bone defects, and (2) to verify whether or not the bony walls surrounding the maxillary sinuses are actually as thick as they appear on CT. The phantom was made of an acrylic cylinder containing three cavities simulating the maxillary sinuses and the nasal cavity and filled with water. The walls, made of thin aluminum and acrylic plates and placed between water and air, disappeared in some CT images. The thickness of the walls calculated from CT values was greater than the true thickness imaged by each CT scanner. The author stresses that in CT images, either experimentally or clinically, thin bony walls placed between water and air or fat tend to disappear, and that bony walls tend to appear thicker than their true thickenss.departmental bulletin pape
CT kod politraumatiziranih bolesnika
No full textKompjuterizirana tomografija je složena dijagnostička metoda koja omogućuje izvanredan prikaz anatomskih detalja organa u unutrašnjosti ljudskog tijela koristeći se poprečnim presjecima. Prigodna je za pacijente svih kliničkih kategorija i uzrasta jer je neinvazivna i bezbolna. Kao pretraga je bitna kod politraumatiziranih bolesnika jer je CT metoda izbora za nepokretne i teško ozlijeđene pacijente te pacijente poremećene svijesti; one koji ne surađuju pa se pregledavaju uz anesteziološku potporu. Pacijent u tijeku pretrage najčešće leži na leđima,a posebna suradnja potrebna je samo u nekim vrstama pregleda (prestanak disanja). Rezultat pregleda visokorezolutivna je digitalna slika koju se može kompjutorski obrađivati,što uključuje mjerenje dimenzija i koeficijenta atenuacije (CT broj- vrijednost u Hounsfieldovim jedinicama),multiplanarnu i 3D rekonstrukciju,dinamični prikaz krvotoka itd. Kompjutorski programi omogućuju razvoj potpuno novog prikaza unutrašnjosti ljudskog tijela, no uz sve te nove tehnologije i prednosti kompjuteriziranu tomografiju prate i nedostatci. Jedan od najvažnijih nedostataka je ionizirajuće zračenje. S obzirom da ionizirajuće zračenje može štetno djelovati na ljudsko tijelo velika je uloga radiološkog tehnologa da svoj posao obavlja svjesno i odgovorno kako bi rezultat pretrage opravdao taj nedostatak
An approach to increasing the resolution of industrial CT images based on an aperture collimator
No full textThe spatial resolution of CT images is dominated by the focal spot size when it is large relative to the detector cells. We propose an approach to increase the spatial resolution by utilizing an aperture collimator. The aperture collimator is specially designed and placed in front of the X-ray source so that the rays penetrating the collimator form a set of narrow fan beams. Then an iterative algorithm is introduced to reconstruct CT images from the data obtained by scanning the narrow fan beams. Numerical experiments show that the proposed approach could significantly increase the resolution of the CT images. Furthermore, this approach is also robust against some challenging cases, such as the examination of low contrast object, reconstruction based on multi-energy data and perturbation of geometric errors in CT systems. (C) 2013 Optical Society of AmericaOpticsSCI(E)EI1ARTICLE2327946-279632
3D segmentation of kidney stone CT images
No full textOvaj diplomski rad usmjeren je na implementaciju i usporedbu različitih metoda 3D segmentacije s primjenom na problem segmentacije CT snimaka bubrežnog kamenca.
Budući da se sve metode 3D segmentacije provode nad diskretnom trodimenzionalnom rešetkom, ulazni podaci (skup datoteka u DICOM formatu) obrađeni su i oblikovani tako da je omogućen odabir područja interesa i iz njega stvaranje diskretne rešetke.
U sklopu rada, implementirane su metode amplitudne segmentacije, segmentacije izrastanjem područja te segmentacije temeljene na lokalnoj faznoj koherenciji. Kao ocjena uspješnosti segmentacije korištena je mjera sličnosti između napravljenog modela i referentnog modela izvađenog kamenca. Mjera sličnosti dobivena je provođenjem postupka registracije modela korištenjem ICP algoritma. Također, napravljena je usporedba s rezultatima segmentacija provedenih korištenjem dostupnih programskih alata za 3D medicinsku segmentaciju. Napravljena je i usporedba brzine izvođenja implementiranih segmentacija te ocjena uspješnosti segmentacija u ovisnosti o subjektivnim odabirima područja interesa.This thesis focuses on the implementation and comparison of different 3D segmentation methods along with their application to the medical problem of kidney stone CT image segmentation.
Considering the fact that the all segmentation methods require a discrete three-dimensional grid, the input data in DICOM format had to be processed and shaped in the form suitable for the process of region of interest (ROI) selection and the creation of the three-dimensional grid.
Three 3D segmentation methods were presented and implemented in this thesis -- an amplitude segmentation method, a region growing segmentation and a segmentation method based on the local phase coherence. For the evaluation of implemented segmentation methods, created models were compared with surgically removed kidney stone and also with the models created using few of the available software tools for 3D medical segmentation. Models were compared based on the similarity measure obtained via ICP algorithm. Also, an execution time analysis for different segmentation methods was made as well as the comparison of the segmentation performance depending on the subjective choices of ROI
Correlation between bone density of the lumbar spine and fatty infiltration of psoas muscle in abdominal CT
No full textOsteoporoza je bolest smanjene koštane gustoće i predstavlja veliki javnozdravstveni problem, koji najčešće zahvaća osobe starije životne dobi, više žene nego muškarce. Osim promjena na kostima, koje nastaju s dobi, prisutne su i promjene na mišićima, a manifestiraju se kao atrofija i masna infiltracija mišića. Zlatni standard u dijagnostici osteoporoze je denzitometrija, metoda koja koristi rendgenske zrake dviju energija, a dobiveni rezultati se uspoređuju s rezultatima mlade, zdrave populacije u standardnim devijacijama. U zadnjih nekoliko godine sveprisutna je ideja oportunističkog CT probira smanjene gustoće kostiju, koja je pokazala izvrsnu korelaciju s denzitometrijom. Uz to, CT se pokazao kao izvrsna metoda u dijagnostici masne infiltracije mišića, koja se prikazuje kao niže vrijednosti u Hounsfieldovim jedinicama (H.J.), a može prikazati promjene koje nastaju infiltracijom masti od samo 3%. Cilj ovog istraživanja je bio odrediti možebitnu povezanost koštane gustoće slabinske kralježnice i masne infiltracije m. psoasa majora na CT abdomena u osoba mlađe i srednje životne dobi u kojih ne očekujemo izražene degenerativne promjene. Također, istražili smo utječe li primjena jodnog kontrastnog sredstva na mjerenja denziteta kosti i mišića na postkontrastnim fazama CT snimanja. Retrospektivno su analizirani slikovni materijali 113 ispitanika u dobi od 18 do 49 godina, koji su podvrgnuti višefaznom protokolu CT abdomena i zdjelice od srpnja do prosinca 2021. godine u KBC Split. Na aksijalnim presjecima su kružnim ROI-em mjerene H.J. trabekularnog dijela trupa L4 kralješka, a konture oba m. psoasa su iscrtavane ručno i u nativnoj, arterijskoj i venskoj fazi te također izražene u H.J. Rezultati su pokazali značajnu povezanost smanjene gustoće kostiju i masne infiltracije m. psoas majora s dobi ispitanika, a utvrđena je međusobna pozitivna korelacija smanjene koštane gustoće i masne infiltracije mišića. Nisu pronađene značajne razlike između spola ispitanika, izuzev nativno viših vrijednosti denziteta trupa L4 kralješka u ženskih ispitanica. Primjena jodnog kontrastnog sredstva značajno je utjecala na mjerene vrijednosti oba parametra. Razlika između nativnih i postkontrastnih mjerenja koštane gustoće L4 kralješka je u prosjeku iznosila 20 H.J., a denziteta m. psoasa majora oko 6-8 H.J., s tim da su postkontrastne razlike u denzitetima m. psoasa bile neznačajno više kod žena nego kod muškaraca. Dobivenim rezultatima smo potvrdili početnu hipotezu i smatramo da oportunistički dobiveni podatci s CT snimanja za druge indikacije uistinu mogu dati vrijedne podatke, koji se mogu iskoristiti u svrhu dijagnosticiranja smanjene gustoće kostiju i masne infiltracije mišića.Osteoporosis is a disease of reduced bone density, and it represents a major public health problem that most commonly affects the elderly, more often women than men. In addition to the age-related bone changes, age-related changes in the muscles are also recognized, and they manifest as atrophy and fatty infiltration of the muscles. The gold standard for the osteoporosis diagnosis is a densitometry, method that uses X-rays of two energies, and compares the results with those of a young, healthy population in standard deviations. In recent years, the idea of opportunistic CT screening of reduced bone density has been broadly introduced, showing an excellent correlation with densitometry. In addition, CT has proven to be an excellent method for the diagnosis of muscle infiltration, which is presented as lower values of Hounsfield units (H.U.), confirming that CT can show changes resulting from fat infiltration of only 3%. The aim of this study was to determine the possible association between bone density of the lumbar spine and fatty infiltration of the psoas major muscle on the abdominal CT in young and middle-aged people in whom the obvious degenerative changes are not to expect. We also investigated whether the use of iodine contrast agent affected bone and muscle density measurements in the postcontrast phases of CT imaging. The imaging materials of 113 subjects aged 18 to 49, who underwent a multiphase CT protocol of the abdomen and pelvis from July to December 2021 at the Clinical Hospital Center Split, were retrospectively analyzed. On axial CT slices, H.J. was measured by drawing a circular ROI in the trabecular part of L4 vertebra, and the contours of both psoas muscles were drawn manually and were expressed in anaverage H.U. The results showed a significant age correlation of a decreased bone density and fatty infiltration of psoas muscle with age, and a positive correlation between reduced bone density and fatty infiltration of a muscle. No significant differences were found between the sexes of the subjects, except for higher values of L4 vertebral body density in female subjects on native scans. The application of iodine contrast agent significantly affected the measured values of both parameters. The difference between native and postcontrast measurements of L4 vertebral bone density averaged 20 H.U., and the density of m. psoas major was 6-8 H.U., with postcontrast differences in density of m. psoas being slightly higher in women than in men. The results confirmed the initial hypothesis and we believe that opportunistic CT imaging for other indications can indeed provide valuable data, which can be used to diagnose reduced bone density and fatty muscle infiltration
Author Co-Citation Analysis (ACA): a powerful tool for representing implicit knowledge of scholar knowledge workers
No full textIn the last decade, knowledge has emerged as one of the most important and valuable organizational assets. Gradually this importance caused to emergence of new discipline entitled ―knowledge management‖. However one of the major challenges of knowledge management is conversion implicit or tacit knowledge to explicit knowledge. Thus Making knowledge visible so that it can be better accessed, discussed, valued or generally managed is a long-standing objective in knowledge management. Accordingly in this paper author co- citation analysis (ACA) will be proposed as an efficient technique of knowledge visualization in academia (Scholar knowledge workers)
Verbeterde beeldreconstructie bij CT-scanners
No full textDe CT-scanner heeft een belangrijke rol in de medische wereld. Helaas gebruikt de CT-scanner voor het opstellen van een scan schadelijke straling. In dit onderzoek is nagegaan of er een betere beeldreconstructietechniek te vinden is voor het opstellen van een CT-afbeelding met gebruik van minder straling.De standaard voor het opstellen van een CT-afbeelding is het gebruik van de 2-norm. Vergelijken we de CT-afbeeldingen geconstrueerd met de 2-norm met CT-afbeeldingen geconstrueerd met de 1-norm en 0.5-norm dan zien we dat de 1-norm visueel het beste resultaat oplevert.Naast het vergelijken van de verschillende normen hebben we ook verschillende epsilon-regularisatiemethodes bekeken. De numerieke experimenten met de verschillende epsilon-regularisatiemethodes hebben we uitgevoerd op een systeem met 0%, 3% en 10% ruis, om te onderzoeken welke methode het beste toepasbaar is in de praktijk. Van de door ons geteste epsilon-regularisatiemethodes bleek de epsilon-regularisatie met epsilon := epsilon/2 met startwaarde epsilon = 10^(-8) en gebruik van de 1-norm de meest geschikte methode om een onderbepaald CT-probleem op te lossen
MRI-based synthetic CT in the detection of knee osteoarthritis: Comparison with CT
No full textMagnetic resonance Imaging is the gold standard for assessment of soft tissues; however, X-ray-based techniques are required for evaluating bone-related pathologies. This study evaluated the performance of synthetic computed tomography (sCT), a novel MRI-based bone visualization technique, compared with CT, for the scoring of knee osteoarthritis. sCT images were generated from the 3T T1-weighted gradient-echo MR images using a trained machine learning algorithm. Two readers scored the severity of osteoarthritis in tibiofemoral and patellofemoral joints according to OACT, which enables the evaluation of osteoarthritis, from its characteristics of joint space narrowing, osteophytes, cysts and sclerosis in CT (and sCT) images. Cohen's κ was used to assess the interreader agreement for each modality, and intermodality agreement of CT- and sCT-based scores for each reader. We also compared the confidence level of readers for grading CT and sCT images using confidence scores collected during grading. Inter-reader agreement for tibiofemoral and patellofemoral joints were almost-perfect for both modalities (κ = 0.83–0.88). The intermodality agreement of osteoarthritis scores between CT and sCT was substantial to almost-perfect for tibiofemoral (κ = 0.63 and 0.84 for the two readers) and patellofemoral joints (κ = 0.78 and 0.81 for the two readers). The analysis of diagnosis confidence scores showed comparable visual quality of the two modalities, where both are showing acceptable confidence levels for scoring OA. In conclusion, in this single-center study, sCT and CT were comparable for the scoring of knee OA.</p
Automatic Atlas Based Analysis of Radiotracer Uptake in Bones from Fused Nuclear Imaging/CT Data Sets of Mice
No full textPreclinical in vivo imaging is a powerful tool used for a wide variety of biomedical research applications including oncology, cardiac disease, and neurological disease. Disease physiology can be imaged in vivo with molecular imaging such as PET and SPECT. Quality analysis of molecular in vivo images currently requires an expert technician. The feasibility of large preclinical molecular imaging studies is limited by the man hours required to process the overwhelming amount of data created from preclinical scans. Our proposed solution to the bottle neck of manual image analysis is to implement automation of preclinical molecular image analysis. The method described in this study automatically registers different bone regions of interest in fused molecular imaging/CT scans. Automated analysis can run without supervision from a user, allowing for an increase in image processing throughput compared to manual analysis. The results of this novel image analysis show that atlas based registration of CT data is possible with a moderate degree of accuracy. Using this registration method to generate radiotracer uptake values for different bone groups resulted in mixed success. Bones that are registered first; skull, spine, pelvis, had automated radiotracer uptake measurements that correlated highly with the manual radiotracer uptake measurements. Bones that were last to be registered; tibia, hindpaws, were susceptible to large amounts of variation from the manual radiotracer uptake measurements. Large improvements to the accuracy of the results could be made by ensuring the accuracy of the joint registration of the atlas to the CT dataset
Towards a computer-assisted Computational Thinking (CT) assessment system in higher education
No full textWith the vision to promote CT to a wider group of audiences, this PhD project explores the formative assessment of CT skills in Programming Education to support students to learn CT skills in Higher Education. In this project, we plan to investigate the importance of CT in the context of Higher Education, explore the relationship between CT skills and programming skills, build a model to assess learners' CT skills and develop a computer-assisted assessment system with automated components to enhance students' CT competences in Higher Education. Mixed-method research methodologies will be employed in distinct phases of the project accordingly. A system which allows formative assessment of CT skills will be iteratively designed and constructed throughout the project. The outcome of the project should support the CT learning process, make CT more visible for people from diverse backgrounds and empower them with a CT mindset to embrace the digitalization of society.Web Information System
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