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Query: "author" (Luka Ležaič) .

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1.
Post-radiation xerostomia therapy with allogeneic mesenchymal stromal stem cells in patients with head and neck cancer : study protocol for phase I clinical trial
Primož Strojan, Gaber Plavc, Marko Kokalj, Goran Mitrović, Olga Blatnik, Luka Ležaič, Aljaž Sočan, Aljoša Bavec, Nataša Tešić, Katrina Pretnar-Hartman, Urban Švajger, 2023, original scientific article

Abstract: Background: Xerostomia is a common side effect of radiotherapy in patients with head and neck tumors that negatively affects quality of life. There is no known effective standard treatment for xerostomia. Here, we present the study protocol used to evaluate the safety and preliminary efficacy of allogeneic mesenchymal stromal stem cells (MSCs) derived from umbilical cord tissue. Methods: Ten oropharyngeal cancer patients with post-radiation xerostomia and no evidence of disease recurrence 2 or more years after (chemo)irradiation (intervention group) and 10 healthy volunteers (control group) will be enrolled in this nonrandomized, open-label, phase I exploratory study. MSCs from umbilical cord tissue will be inserted under ultrasound guidance into both parotid glands and both submandibular glands of the patients. Toxicity of the procedure will be assessed according to CTCAE v5.0 criteria at days 0, 1, 5, 28, and 120. Efficacy will be assessed by measuring salivary flow and analyzing its composition, scintigraphic evaluation of MSC grafting, retention, and migration, and questionnaires measuring subjective xerostomia and quality of life. In addition, the radiological, functional, and morphological characteristics of the salivary tissue will be assessed before, at 4 weeks, and at 4 months after the procedure. In the control group subjects, only salivary flow rate and salivary composition will be determined. Discussion: The use of allogeneic MSCs from umbilical cord tissue represents an innovative approach for the treatment of xerostomia after radiation. Due to the noninvasive collection procedure, flexibility of cryobanking, and biological advantages, xerostomia therapy using allogeneic MSCs from umbilical cord tissue may have an advantage over other similar therapies.
Keywords: oropharyngeal cancer, xerostomia, mesenchymal stromal stem cells
Published in DiRROS: 26.07.2024; Views: 389; Downloads: 180
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2.
Detection and localization of hyperfunctioning parathyroid glands on [18F]fluorocholine PET/CT using deep learning – model performance and comparison to human experts
Leon Jarabek, Jan Jamšek, Anka Cuderman, Sebastijan Rep, Marko Hočevar, Tomaž Kocjan, Mojca Jensterle Sever, Žiga Špiclin, Žiga Maček Ležaić, Filip Cvetko, Luka Ležaič, 2022, original scientific article

Abstract: In the setting of primary hyperparathyroidism (PHPT), [18F]fluorocholine PET/CT (FCH-PET) has excellent diagnostic performance, with experienced practitioners achieving 97.7% accuracy in localising hyperfunctioning parathyroid tissue (HPTT). Due to the relative triviality of the task for human readers, we explored the performance of deep learning (DL) methods for HPTT detection and localisation on FCH-PET images in the setting of PHPT. Patients and methods. We used a dataset of 93 subjects with PHPT imaged using FCH-PET, of which 74 subjects had visible HPTT while 19 controls had no visible HPTT on FCH-PET. A conventional Resnet10 as well as a novel mPETResnet10 DL model were trained and tested to detect (present, not present) and localise (upper left, lower left, upper right or lower right) HPTT. Our mPETResnet10 architecture also contained a region-of-interest masking algorithm that we evaluated qualitatively in order to try to explain the model’s decision process. Results. The models detected the presence of HPTT with an accuracy of 83% and determined the quadrant of HPTT with an accuracy of 74%. The DL methods performed statistically worse (p < 0.001) in both tasks compared to human readers, who localise HPTT with the accuracy of 97.7%. The produced region-of-interest mask, while not showing a consistent added value in the qualitative evaluation of model’s decision process, had correctly identified the foreground PET signal. Conclusions. Our experiment is the first reported use of DL analysis of FCH-PET in PHPT. We have shown that it is possible to utilize DL methods with FCH-PET to detect and localize HPTT. Given our small dataset of 93 subjects, results are nevertheless promising for further research
Keywords: primary hyperparathyroidism, deep learning, nuclear medicine
Published in DiRROS: 25.07.2024; Views: 318; Downloads: 105
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Image reconstruction using small-voxel size improves small lesion detection for positron emission tomography
Sebastijan Rep, Petra Tomše, Luka Jensterle, Leon Jarabek, Katja Zaletel, Luka Ležaič, 2022, original scientific article

Abstract: Background. PET/CT imaging is widely used in oncology and provides both metabolic and anatomic information. Because of the relatively poor spatial resolution of PET, the detection of small lesions is limited. The low spatial resolution introduces the partial-volume effect (PVE) which negatively affects images both qualitatively and quantitatively. The aim of the study was to investigate the effect of small-voxel (2 mm in-line pixel size) vs. standard-voxel (4 mm in-line pixel size) reconstruction on lesion detection and image quality in a range of activity ratios. Materials and methods. The National Electrical Manufacturers Association (NEMA) body phantom and the Micro Hollow-Sphere phantom spheres were filled with a solution of [18F]fluorodeoxyglucose ([18F]FDG) in sphere-to-background ratios of 2:1, 3:1, 4:1 and 8:1. In all images reconstructed with 2 mm and 4 mm in-line pixel size the visual lesion delineation, contrast recovery coefficient (CRC) and contrast-to-noise ratio (CNR) were evaluated. Results. For smaller (≤ 13 mm) phantom spheres, significantly higher CRC and CNR using small-voxel reconstructions were found, also improving visual lesion delineation. CRC did not differ significantly for larger (≥ 17 mm) spheres using 2 mm and 4 mm in-line pixel size, but CNR was significantly lower; however, lower CNR did not affect visual lesion delineation. Conclusions. Small-voxel reconstruction consistently improves precise small lesion delineation, lesion contrast and image quality.
Keywords: PET/CT, voxel size, contrast recovery coefficient, contrast-to-noise ratio
Published in DiRROS: 24.07.2024; Views: 221; Downloads: 136
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Priporočila za obravnavo bolnikov s pljučnim rakom
Martina Vrankar, Nina Boc, Izidor Kern, Aleš Rozman, Karmen Stanič, Tomaž Štupnik, Mojca Unk, Maja Ebert Moltara, Vesna Zadnik, Katja Adamič, Jernej Benedik, Marko Bitenc, Jasna But-Hadžić, Anton Crnjac, Marina Čakš, Dominik Časar, Eva Ćirić, Tanja Čufer, Ana Demšar, Rok Devjak, Goran Gačevski, Marta Globočnik Kukovica, Kristina Gornik-Kramberger, Maja Ivanetič Pantar, Marija Ivanović, Urška Janžič, Staša Jelerčič, Veronika Kloboves-Prevodnik, Mile Kovačević, Luka Ležaič, Mateja Marc-Malovrh, Katja Mohorčič, Loredana Mrak, Igor Požek, Nina Turnšek, Bogdan Vidmar, Dušanka Vidovič, Gregor Vlačić, Ana Lina Vodušek, Rok Zbačnik, Ivana Žagar, 2023, professional article

Abstract: Leta 2019 so bila objavljena Priporočila za obravnavo bolnikov s pljučnim rakom, ki so v slovenski prostor vnesla prepotrebno poenotenje diagnostike in zdravljenja z namenom izboljšanja preživetja bolnikov s pljučnim rakom. Posodobitev Priporočil tri leta po izidu izvirnika prinaša največ novosti v poglavju o sistemskem zdravljenju bolnikov s pljučnim rakom. To kaže na izjemen napredek na področju razumevanja onkogeneze in biologije pljučnega raka ter s tem razvoja novih zdravil. Breme pljučnega raka ostaja veliko, saj je pljučni rak pri nas in v svetu še vedno najpogostejši vzrok smrti zaradi raka. Za vsako peto smrt zaradi raka je odgovoren pljučni rak. Skoraj tretjina bolnikov s pljučnim rakom ne prejme specifičnega onkološkega zdravljenja, bodisi zaradi slabega stanja zmogljivosti, spremljajočih bolezni ali obsega bolezni. Polovica bolnikov ima ob diagnozi razsejano bolezen, zaradi česar izboljšanje preživetja z malimi koraki sledi napredku v zdravljenju bolnikov s pljučnim rakom. Ti podatki nas opominjajo, da se bomo morali za velike premike v obravnavi bolnikov s pljučnim rakom lotiti drugačnih pristopov. Kot najbolj obetavno se ponuja zgodnje odkrivanje bolezni, ko so možnosti ozdravitve pljučnega raka najboljše. Zapisana Priporočila so usmeritev za obravnavo bolnikov s pljučnim rakom. Le s sodobnim multidisciplinarnim pristopom obravnave lahko bolniku ponudimo zdravljenje, ki mu omogoča najboljši izhod prognostično neugodne bolezni.
Keywords: pljučni rak, priporočila
Published in DiRROS: 27.07.2023; Views: 759; Downloads: 298
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Nuklearna medicina : diagnostika in teranostika
Luka Ležaič, 2016, published professional conference contribution

Keywords: nuklearna medicina, radiofarmaki, diagnostika, teranostika
Published in DiRROS: 17.09.2019; Views: 2362; Downloads: 687
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10.
PET/CT z 18F-Fgd pri uroloških malignomih
Luka Ležaič, 2013, published professional conference contribution

Keywords: slikovna diagnostika, tomografija, urološki malignomi
Published in DiRROS: 17.09.2019; Views: 2154; Downloads: 620
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