Kudrevičius, Linas

Only 10-40% of patients with cancer in low-income and middle-income countries were able to access curative or palliative radiotherapy in 2015. We aimed to assess the current status of diagnostic imaging and radiotherapy services in the Baltic countries, eastern Europe, central Asia, and the Caucasus by collecting and analysing local data.

Stereotaksinės radiochirurgijos gama peiliu pradininkas - neurochirurgas Larsas Lekselis. Gama peilis skirtas neinvaziniam neurochirurginės patologijos gydymui gama spinduliais. Konceptualiai gama peilis savo technine konstrukcija žymiai skiriasi nuo kitų stereotaksinei radiochirurgijai skirtų sistemų. Sferoje tolygiai išdėstyti 192 kobalto 60 šaltiniai, skleisdami jonizuojančios radiacijos spindulius, susikertančius konkrečiame apskaičiuotame trimatės erdvės taške, leidžia tiksliai ir saugiai planuoti bei realizuoti labai dideles spinduliuotės dozes. Lietuvoje tai nauja technologija. Pirmasis gama peilis pradėjo veikti Lietuvos sveikatos mokslų universiteto Kauno klinikų Neurochirurgijos klinikoje 2019 metais. Gama peiliu atliekamose operacijoje dalyvauja daugiaprofilinė komanda, kurią sudaro gydytojas neurochirurgas, gydytojas radioterapeutas, medicinos fizikas ir radiotechnologas. Ruošiant pacientą gydymui, planuojant gydymą ir jį realizuojant, atliekamas nuolatinis veiksmų stebėjimas, kas leidžia išvengti klaidų ir pasiekti gerų rezultatų. Radiochirurgijoje komandinis darbas ypač svarbus, nes į intrakranijinius taikinius skiriama neurodestrukcinė spinduliuotės dozė, todėl net menka gydymo paklaida gali lemti ligonio sveikų smegenų apšvitą ir neurologinės būklės blogėjimą. Siekiant saugaus ir kokybiško gydymo pacientų atrankoje ir kituose gydymo etapuose priimant sprendimus dalyvauja ne vienas asmuo, o visa specialistų komanda. Ši mokomoji knyga skirta gydytojams rezidentams ir gydytojams specialistams. Siekiama supažindinti su dažniausia patologija, kurią galima gydyti su gama peiliu, gydymo indikacijomis, planavimu ir dozėmis, taip pat aptariami metodo galimybes ribojantys veiksniai. Knygoje aprašomi LSMUL Neurochirurgijos klinikoje gydytų pacientų atvejai.

Ionizing radiation covers a broad spectrum of applications. Since radioactive/radiation pollution is directly related to radiation risk, radiation levels should be strictly controlled. Different detection methods can be applied for radiation registration and monitoring. In this paper, radiation-induced variations in the optical properties of silver-enriched PVA-based hydrogel films with and without azo dye (Toluidine blue O, TBO, and Methyl red, MR) additives were investigated, and the feasibility of these free-standing films to serve as radiation detectors/exposure indicators was assessed. AgNO admixed with PVA gel was used as a source for the radiation-induced synthesis of silver nanoparticles (AgNPs) in irradiated gel films. Three types of sensors were prepared: silver-enriched PVA films containing a small amount of glycerol (AgPVAGly); silver-enriched PVA films with toluidine blue adducts (AgPVAGlyTBO); and silver-enriched PVA films with methyl red additives (AgPVAGlyMR). The selection of TBO and MR was based on their sensitivity to irradiation. The irradiation of the samples was performed in TrueBeam2.1 (VARIAN) using 6 MeV photons. Different doses up to 10 Gy were delivered to the films. The sensitivity of the films was assessed by analyzing the characteristic UV-Vis absorbance peaks on the same day as irradiation and 7, 30, 45, 90, and 180 days after irradiation. It was found that the addition of azo dyes led to an enhanced radiation sensitivity of the AgNPs containing films (0.6 Gy for AgPVAGlyTBO and 0.4 Gy for AgPVAGlyMR) irradiated with <2 Gy doses, indicating their applicability as low-dose exposure indicators. The irradiated films were less sensitive to higher doses. Almost no dose fading was detected between the 7th and 45th day after irradiation. Based on the obtained results, competing AgNP formation and color-bleaching effects in the AgPVAGly films with dye additives are discussed.

Abstract: Leksell Gamma Knife® (GK) stereotactic radiosurgery (SRS) system allows treatment of various targets in the brain: from the smallest 0.01 cc volume brain metastases (BM), up to 10 cc targets in one single session and even treatment of larger volumes applying hypofractionated treatment regime and high dose (< 150 Gy) functional targets [1-4]. This SRS system with 3 collimator sizes, sector blocking and wide range of isodose settings allow to prioritise selectivity, gradient index or time. In this study the application of various collimator settings was investigated for patients with multiple small BM in order to find out the best treatment planning approach and set the guidelines.

Background: Large intracranial meningiomas especially involving cranial base represent a significant treatment challenge and lead to increased morbidity and mortality. In some cases, large meningioma volume and proximity to critical structures reduce access to surgery and even hypofractionated radiosurgery. In this study, we evaluate safety and efficacy of the multistaged hypofractionated Gamma knife radiosurgery (MHGK) method for the treatment of very large meningiomas at our center. Methods: 6 female patients with progressing large-volume, an average of 36.32cm3, intracranial meningiomas after multiple craniotomies, and no previous intracranial radiotherapy were treated using this MHGK technique. 4 meningiomas were WHO grade I (3 meningothelial, 1 transitional), and histology of the other 2 meningiomas was unknown. Tumors were divided into two or three segments (average volume 17.76cm3) and treated prescribing 25Gy in 5 daily fractions with two-month gaps between each meningioma part. Treatment volumes were placed with 1-2 mm gap and areas of dose accumulation between treatment plans were directed away from critical structures. Results: Due to proximity to critical structures dose of 99% tumor volume was decreased to 21.49Gy on average (18.3 – 24.5Gy). During follow-up from 6 to 36 months (19 months’ average) all tumors showed volume shrinkage tendency. On average 8% of tumor volume decrease was observed after 6 months of follow-up. Two patients with a follow-up of 36 months showed a tumor volume decrease of 31%. During follow up no patient acquired acute or late treatment-related toxicities. Half a year after the treatment symptoms of 3 patients improved due to the decreased compression to the brain stem and other critical areas. Conclusions: Proposed treatment method for large-volume meningiomas shows promising results as an effective and safe treatment option for otherwise untreatable meningiomas. More patients and a longer follow-up are needed to verify the efficacy and safety of this treatment approach.

Highly precise dose delivery to the target (tumor or cancerous tissue) is a key point whenbrain diseases are treated applying recent stereotactic techniques: intensity-modulated, image-guidedradiotherapy, volumetric modulated arc therapy, Gamma knife radiosurgery. The doses in onesingle shot may vary between tens and hundreds of Gy and cause significant cell/tissue/organdamages. This indicates the need for implementation of quality assurance (QA) measures whichare realized performing treatment dose verification with more than one calibrated quality assurancemethod or tool, especially when functional radiosurgery with a high dose (up to 40 Gy in ourcase) shall be delivered to the target using small 4 mm collimator. Application of two dosimetrymethods: radiochromic film dosimetry using RTQA2 and EBT3 films and dose gel dosimetry usingmodified nPAG polymer gels for quality assurance purposes in stereotactic radiosurgery treatmentsusing Leksell Gamma Knife© Icon™ facility is discussed in this paper. It is shown that due to theirpolymerization ability upon irradiation nPAG gels might be potentially used as a quality assurancetool in Gamma knife radiosurgery: they indicate well pronounced linear dose response in hypofractionated(up to 10 Gy) dose range and are sensitive enough to irradiation dose changes with ahigh (at least 0.2 mm) spatial resolution. Dose assessment sensitivity of gels depends on parametersof a dose evaluation method (optical or magnetic resonance imaging), however, is similar to thisestimated using film dosimetry, which is set as a standard dosimetry method for dose verificationin radiotherapy.

The treatment of patients with relatively rare cerebral arteriovenous malformations (AVMs) requires specific knowledge and high precision of multidisciplinary team. Treatment management consists of microsurgery, endovascular embolization, dosimetry method application and radiosurgery using Gamma knife facility or stereotactic radiotherapy (SRS) with linear accelerator. The overview of AVMs treatments in LUHS Kaunas clinics, Neurosurgery department during the period from 2019-06-11 to 2021-09-01 is presented in results part. Introduction Cerebral arteriovenous malformation (AVMs) is aberrant blood vessels tangle connecting arteries and veins in the head. This tangle disturbs normal oxygen circulation and blood flow. Any single treatment strategy success for large AVMs (volume >10ml,conventionally nidus diameter >3cm) is limited and related to higher complications after treatment [1].Individual treatment modality selection often includes microsurgery, endovascular embolization and radiosurgery combinations. Microsurgery can exclude AVMs from blood circulation immediately [2],radiosurgery is very useful when surgical procedures are at high risk related to close critical anatomic structures. If AVMs are formed near functionally important areas, the tactic of endovascular embolization before Gamma knife (GK) radiosurgery [3] is the mostly used alternative to open surgery and is especially preferred for high-flow AVM [4]. Aggregation of two methods derivation can improve treatment efficacy from 30-62%to 68-90%, but an occlusion occurs after 1-3 years [5]. Itshould be noted that the dose delivered to the targetduring Gamma knife treatment should e verifie[..d and

Tikslas. Tyrimo tikslas įvertinti gama peilio talamotomijos efektyvumą, stabdant tremorą sergantiesiems Parkinsono liga (PL) ir esencialiniu tremoru, kai kiti invaziniai gydymo metodai nerekomenduotini. Tiriamieji ir tyrimo metodai. Nuo 2019 m. birželio iki 2021 m. sausio dėl esencialinio tremoro ir PL sąlygoto tremoro atitinkamai atlikta 27 ir 20 vienpusių gama peilio talamotomijų. Naudojant Leksell G stereotaksinį rėmą, pagal standartizuotą metodiką, naudojant 4 mm diametro kolimatoriaus šūvį, į n.ventralis intermedius (VIM) zoną paskirta 130-140 Gy dozė. Tyrime pooperacinis vertinimas planuotas atlikti praėjus 6 ir 12 mėnesių po taikyto gydymo. Tačiau dėl besikartojančio karantino dėl COVID-19 buvo apsunkintas ligonių kontaktinis vertinimas, todėl rezultatai vertinti telefoninės apklausos metu. Iš 20 ligonių, sergančių PL, pavyko susisiekti tik su 12, iš kurių aštuoniems gydymas buvo taikytas mažiau nei prieš 6 mėnesius. Nuspręsta PL grupės ligonių gydymo rezultatų analizę atlikti po 6 mėnesių. Rezultatai. Iš 27 sergančiųjų esencialiniu tremoru telefonu pakalbinti pavyko 23 ligonius. Viena ligonė per stebėjimo laikotarpį mirė nuo COVID-19 infekcijos. Iš apklaustų 22 ligonių 16 (72 %) teigė, kad jaučia žymų tremoro rankoje sumažėjimą ar visišką jo išnykimą priešingoje, nei atlikta VIM talamotomija, pusėje. Likę 6 ligoniai (28 %) taikyto gydymo efekto iki šiol ne-jaučia. Iš 22 ligonių 4 (18 %) teigė, kad kurį laiką buvo sutrikusi koordinacija ir vargino laikinas rankos nevikrumas, kuris praėjo per kelis mėnesius. Išvados. Gama peilio talamotomija yra saugi ir efektyvi esencialinio rankų tremoro mažinimo priemonė. Pagrindiniai šio gydymo trūkumai yra kelis ar keliolika mėnesių trunkantis latencinis periodas iki pastebimo klinikinio efekto ir laikina ataksija.

The Gamma Knife (GK) technology is developed for stereotactic radiosurgery (SRS). In 1951 Swedish physician Lars Leksell invented stereotactic fixation frame to target beam of radiation into human brain using polar coordinates. Later this system was used to develop the Gamma Knife in 1967 by L. Leksell and B. Larsson in Stockholm, Sweden. For GammaKnife photon radiation Cobalt-60 source was selected. Half-life of Cobalt-60 is 5.26 years and emitted gamma photons are 1.17 MeV and 1.33 MeV energy. First GK prototype was used for neurological surgery for treatment of patients with pain and movement disorders. In 1972 L. Leksell established “Elekta” and continued to improve this technology. Today without prototypes are established Leksell Gamma Knife models: U (A), B, C, 4C, Perfexion and Icon. Introduction Original Gamma Knife had 201 Cobalt-60 sources arranged in a hemispheric configuration and was installed in Sophiahemmet Hospital, Sweden [1]. It was designed for precise and efficient stereotactic radiosurgery for intracranial radiosurgery to treatpituitary tumours, vestibular schwannomas, vascular malformations and functional disorders. The collimation system in GK focuses individual beams of gamma radiation to precise focus point, thus minimizing biological radiation effect for healthy cells. During radiosurgery, stereotactic frame is attached to patient’s head and external collimator helmet (GK U and helmetis in Fig. 1). Typically, one single fraction of radiation in one treatment day. Later new version of Leksell Gamma Knife Model U (A) was developed with computer dose planning system and so decreased dose to patient’s body. Because of hemispheric sources configuration there was challenging issues with load and reload in this early GK models.. […].