Laurikaitis, Marius

This research is aimed at creating and validating a magnetic resonance imaging (MRI) quality control (QC) protocol which can be used in Lithuanian clinical environments. The investigation relies on the phantom based QC measurements performed evaluating three MRI scanners: Siemens Magnetom Skyra (3T), Siemens Magnetom Altea (1.5T), and Philips Ingenia Prodiva (1.5T). Following phantom based QC tests have been performed: measurements of signal-to-noise ratio (SNR), image uniformity (PIU), geometric distortion, low-contrast detectability and high-contrast spatial resolution. The obtained results matched with American QC standards showing just minor variations among devices and sequences. This allowed prepare the unified recommendations for the creation of national MRI QC protocol. The implementation of such protocol would lead to the uniform requirements for image quality, diagnostic dependability and better patient protection throughout the country.

Introduction: Patient dose monitoring is essential for optimizing radiation exposure to acceptable levels, improving patient safety, and maximizing protection during medical imaging. This study aimed to implement an automated patient dose monitoring system for various image-guided radiotherapy examinations using the software OpenREM. Materials & Methods: Depersonalized patient data acquired by kilovoltage cone beam computed tomography (kV-CBCT) imageguided modality of linear accelerator Halcyon V3.1 (Varian Medical Systems), was selected for the analysis. Free open-source OpenREM software (v. 0.10.0) was implemented and utilized in clinical practice to monitor patient doses acquired by applying different CBCT protocols, offering flexible data input and customization. Analysis of the data was aimed at the optimization of working practice and the development of the corresponding recommendations for clinical practitioners. Results: Performed analysis of the data collected within 2.5 years indicated that the dose length product (DLP) obtained by applying the same protocol depending on a scanning volume may differ twice. For example, irradiation doses for the same pelvis scanning protocol differed from 277.7 mGy to 551.0 mGy. Analysis of the protocols revealed, that MV image-guided radiation imaging modality had a significantly higher CTDIvol for a small cohort (n = 20) compared to standard pelvis examinations performed for a much larger participants cohort (n = 8000). Summary: The open-source software OpenREM was successfully implemented in clinical practice to monitor and analyze irradiation doses obtained by patients in kV-CBCT procedures. After evaluating the collected patient data, some recommendations for the personnel regarding protocol selection and optimization of scanning volume were provided.

Abstract: Precise positioning during the radiotherapy procedure of the head and neck patients is extremely important due to the highly sensitive organs at risk surrounding the irradiated target. Set-up errors can occur due to various reasons, such as body contour changes of the patient, which may happen on behalf of weight loss or shrinkage of the tumour, or due to the inappropriate use of immobilisation tools, etc. Image-guided radiotherapy enables corrections and monitoring of these positioning deviations. However, along with known benefits, performing kV-CBCT verifications before each treatment inevitably leads to additional exposure doses. It is known that daily imaging of kV-CBCT for the patient could increase the daily exposure dose by ~1.4 mGy. Investigation was done using linear accelerator Halcyon V3.1 (Varian Medical Systems, Palo Alto, CA, USA), which ensures 100 % Image-guided radiotherapy. All the daily data were collected from medical treatment planning system EclipseTM (Offline Review tool) and were processed with statistical computing software “R”. Analysis of the results showed that despite the additional irradiation doses for the patient, the benefits of daily verifications are undeniable, because patient positioning deviations do not have a clear variation tendency and change randomly during each fraction.

Image-guided radiotherapy (IGRT) is the one of the ways, ensuring radiation treatment accuracy, due to verification of a patient position and determining an accurate tumour localisation. Analysis of the newly installed linear accelerator Halcyon images was performed using treatment planning system Eclipse. It was found that image quality control tests used for the daily practice usually are based on the evaluation of constancy measurements, analysing the main parameters of the images quality and calibrating it, if it is needed.

During radiology procedures, when it is used ionising radiation, the staff should wear the protective cloths, protecting them from scattered radiation. Today the most popular material used for protection is lead, which has a lot of advantages, but also disadvantages, like lead is known as a toxic material, all wearable protection is heavy, aprons can cause back pains or even traumas, and etc. In the last decade it is offered many various types of materials, which could be used instead of lead (tungsten, bismuth, tin, antimony, copper, and etc.). Replacing lead with these materials it is possible to make protections lighter and more comfortable. However, the basic problem of lead-free protections is that it is not always fulfil manufacturer’s requirements.

Results of investigation of the absorbed doses on a phantom surface under the “sticking” and ordinary non-sticking silicone boluses simulating post-operative breast cancer irradiation are presented in this paper. It is shown that the treatment effectiveness in post-operative breast cancer irradiation may be improved when a “sticking” bolus attached to the patient surface is applied instead of an ordinary non-sticking bolus. Application of “sticking” bolus adapted treatment configuration is of advantage because it is independent on air gaps between bolus and the surface. Introduction High energy photon beams, especially megavoltage photon beams, generate a build-up region: absorbed dose maximum (dmax) is at a certain depth in the patient’s body [1-2]. This leads to creation of e a “skin sparing” effect (lower dose on the skin), which depends on energy of the beam, field size, etc. [3-4]. Treating near surface tumours (e.g. post-operative breast cancer treatment) the surface dose (dsurf) is usually increased using boluses. This contributes to the better treatment outcome and allows avoiding the risk of recurrences. Even if the boluses are flexible in the most cases it is difficult or even not possible to avoid air gaps between bolus and the patient’s body without reducing of the treatment quality when covering irregular or rounded body surfaces [2-5]. Air gaps between the bolus and the patient’s body can result in the dose and dose distribution changes [4]. Therefore the accurate measurements of the surface dose, Dsurf, is always an intriguing issue since it provides a valuableclinical information regarding the risk avoidance for the near surfaces recurrences and reducing of the unwanted skin toxicity [6-7].. […].

The medical physics expert (MPE) should be involved in radiotherapy, should be available in nuclear medicine practices and should be involved, as appropriate, in other radiological practices. European Union Member States should ensure that MPEs have adequate theoretical and practical training for the purpose of radiological practices, as well as relevant competencein radiation protection. Due to this reason Member States shall ensure that appropriate curricula was established and shall recognise the corresponding diploms, certificates or formalqualifications. The main objective of the EUTEMPLE-RX project is to provide training courses that allows the medical physicist in radiology and interventional radiology to reach the expert level.The EUTEMPE-RX project courses successfully started this year, and it is planed that all the modules will be repeated in the future.

Radiation doses from diagnostic radiology are the largest contribution to the collective dose from all man-made sources of radiation. Therefore, the main of this paper is to analyse the conditions of patient's overexposure during X-ray chest front projection (PA) and chest lateral projection (LAT) procedures and to apply methods of dose reduction suitable for X-ray department. Two hundred and seventy seven radiographic images of PA and LAT chest projections were analysed and three novel dose reduction methods were applied. The results of dose-area product (DAP) measurements showed that dose-area product values decreased almost two times for PA projection and 20% for a lateral projection after the application of he dose reduction methods. Measurements of the patient's entrance skin dose (ESD) for LAT projection shows that ESD was reduced by 34%. Introduction. Chest radiography is the frequent radiographic procedure performed in the X-ray department. Digital X-ray images are valuable for solving a variety of clinical problems. It serves as diagnostic technique for determining further steps in the establishment of a diagnosis and treatment procedure. Although individual patient dose in chest radiography is relatively low, its contribution to the collective dose is significant due to the frequent use of this examination. About 30%-40% of all diagnostic -ray examinations are reported to be a chest X-ray. The estimated contribution to the collective dose is about 18%. [...].

The protective aprons are worn in examination rooms during radiological examinations and their function is to provide shielding against X-ray radiation. However the improvements manufacturing new light lead aprons need attention to verification of lead equivalent at appropriate tube potential. Lead equivalent thickness calculations for different X-raygenerator types and tube potentials varying from 60 aprons is presented in this paper.

Patient doses in mammography screening examinations in Lithuania have been investigated within a period between 2003 and 2009. In vivo dose measurements were performed using thermoluminescence dosimetry (TLD) technique. Interactive database MAMOLIT was created, which allowed calculating of patient’s doses, documenting of measured and calculated doses and other parameters of the mammography screening examination, following up of the frequency of patient related X-ray examinations, and analysing of the collected data from different points of view. Reference level of 2.4 mGy of the average glandular dose was set for mammography screening in Lithuania on the base of the obtained results. Present paper summarises gathered experience and outlines some problems which may occur when performing dose measurements during mammography screening examinations of patients.