Warsaw Medical Physics Meeting 2015
Monitoring of Indoor radon concentrations in Samawa oil refinery Premises and city dwellings , Iraq
Abdulameer Kazem Farhood
Co - Authors : Lect. Laith M. Rasheed
Contribution of radon and it's radioactive progenies have been found to pose severe health hazards in the indoor environments. It is an established fact that besides air, water, soil, and rocks, naturally occurring radio nuclides are also associated with the petroleum extracted from the sedimentary deposits.
Therefore radon measurements around oil refineries is desirable. In this regard, radon and it's progeny concentrations were measured in several dwellings at an oil refinery premises and these concentrations were compared with those found in dwellings in Samawa city in Iraq.
Proton and carbon beam in hadrontherapy. Beam energy and theoretical modulator parameters in the planning of neoplastic lesion treatment
Co - Authors : Magdalena Garbacz
The hadrontherapy is a dynamically developing part of radiotherapy that uses heavy ions. Its main advantage is low, in comparison with other radiotherapy methods, harmfulness for tissues surrounding the lesion. Hydrogen and carbon ions are the most commonly used in hadrontherapy. SRIM software (based on Bethe-Bloch function) has been used to show how they interact with matter. Heavy ions, accelerated to the order of hundreds of MeV/u, lose their energy in a characteristic way (Bragg peak). The adjustment of the beam energy to the location of the lesion has been achieved by defining a suitable beam energy and a size of the moderator. The results of the theoretical calculations has been compared with available experimental data.
Measurements of Photon doses outside the target for 3DCRT and IMRT radiotherapy
Co - Authors : W. Jackowiak, J. Malicki, M. Skórska, M. Adamczyk, E. Konstanty, T. Piotrowski, K. Polaczek-Grelik
Rapid development of technology in radiotherapy introduced tools that allow for more homogenous dose in the target but may cause dose increase outside the target. It is necessary to know how it can influences to organs at risk and the organs which are more far from the target. Dosimetric measurements of doses outside the target for 3DCRT and IMRT radiotherapy of prostate cancers. The dose was measured by means thermoluminescence detectors (TLD) in the anthropomorphic phantom. Dose distributions were determined for an Alderson phantom in the following organs at risk: thyroid gland, lung, testes and bladder for the alternative treatments using static fields and IMRT. There were three techniques compared: 3DCRT, IMRT and Tomotherpy. The dose measured during 3DCRT treatment was: thyroid gland - 0,42Gy; lung - 0,75Gy; bladder - 77,65Gy; testes - 4,15 Gy. The dose measured during IMRT treatment was: thyroid gland - 0,42Gy; lung - 0,75Gy; bladder - 77,65Gy; testes - 4,15 Gy.
The idea of superconducting gantry in medicine
Co - Authors : Henryk Malinowski
Proton and heavy ions therapy are promising method of radiotherapy. Further development this method and application in clinical practice are necessary, because in many cases it is more beneficial for patients than conventional radiotherapy. Gantry which are used in therapy are large and heavy, currently. Superconducting gantry is the new approach to beam deliver to therapeutic area. SuperGantry is the idea to reduce the weight and size of therapeutic apparatus. The application superconducting magnets in gantry creates the possibility to construct a smaller devices, but also brings additional problems which do not exist, when the conventional gantry is used. One of the most mportant aspect of using superconducting magnets, is their cooling. For this aim cryocoolers systems are used.
On a poster will be presented knowledge acquired during the Summer Student Practice at the Cryogenics Department in Veksler and Baldin Laboratory of High Energy Physics in Joint Institute for Nuclear Research in Dubna and considerations after this practice.
Design and optimization of High-Dose Rate (HDR) Applicator for Skin Irradiation, based on Monte Carlo simulation
Co - Authors : Krzysztof Wincel, Mieczysław Słapa, Piotr Mazarewicz, Anna Wysocka Rabin
HDR brachytherapy is a very effective treatment of skin cancer. Surface applicators, used in this therapy, have ability to become the standard treatment for skin can in the near future. In Polish National Centre for Nuclear Research a prototype of such applicator, equipped with corrective filters, has been built. Developers of it are working now on optimization of its treatment parameters, to assure surface isotropy of the X radiation from the X-ray source.The upgraded model of applicator was developed using Monte Carlo code MCNP. The simulations were performed for the of Ua=50 kV, and for filters of different shapes made from PMMA. The best homogenous of dose distribution was obtained with a filter of 5mm thickness, with an average dose of 1 Gy/min. and standard variation <4%. Measurements to verify results of that calculation are now being performed. An applicator with upgraded corrective filters may thus be regarded as compact, low-cost, device in skin cancer treatment.
Production of 99Mo/99mTc by means of linear medical accelerators
Co - Authors : Adam Konefał, Magdalena Grzemska, Dorota Wiśniewska, Andrzej Orlef
A quite new approach to the production of radionuclides is the application of linear medical accelerators used in the typical radiotherapy in oncological centers. The presented investigations were performed with the use of two medical linacs Clinac 2300 EX and Clinac TrueBeam by Varian installed in the Center of Oncology in Gliwice (Poland). The higher-energy 20 MV X-ray beam was applied for the production of 99Mo/99mTc. A slab made of the natural molybdenum was located on the surface of the plastic window in the bottom of the accelerator head inside the therapeutic X-ray beam. The radioisotope 99Mo is produced in this slab as a result of the photonuclear reactions. The influence of a radiation field size and the irradiated material location on the obtained activities was tested. Additionally, attempts of the neutron field strengthening by means of a lead block and a moderator made of PMMA, located directly behind the target were undertaken.
Receptor mediated imaging for sentinel lymph node (radio)detection
Filip Daniel Puicea
Co - Authors : Dana Niculae, Cosmin Mustaciosu, Catalin Tuta, Filip Puicea, Gabriela Voicu
A lymphoscintigraphy agent requires high density of receptor substrate sites to achieve a receptor affinity required for proper sentinel node detection. The solution could be given by receptor-binding radiopharmaceuticals. The radiolabelling of the mannosyl-cysteine-dextran with 99mTc resulting in a high purity and stability radiolabelled conjugate, suitable for sentinel node detection with low distal lymph accumulation and their in vivo biological evaluation are proposed. Different radiolabelling strategies were evaluated. The RCPs were ranged between 93-99%. The biological evaluation, performed in Wistar rats, shows a rapid and highly specific sentinel node accumulation, up to 11% ID and a very good sentinel node extraction in respect with the second node in the chain, up to 94% at 1h p.i. The 99mTc labelled dextran-mannose derivatives show specific accumulation in the sentinel lymph node and could be further evaluated as potential agents for targeted lymphoscintigraphy.
Multiparameter assessment of atrial fibrillation ablation duration
Co - Authors : Piotr Podziemski, Lauren Wilson, Simon Stolcman, Prashanthan Sanders, Paweł Kuklik, Jan J. Żebrowski
Atrial fibrillation (AF) is the common and the most complex sustained arrhythmia. In this study we assess the reliability of the algorithmic complexity (AC) analysis of single intracardiac electrogram recorded at the beginning of the AF ablation procedure and compare the results with other commonly used methods: SD of Cycle Length, Complex Fractionated Electrogram Indices, Shannon and Sample Entropy among others.
ANOVA and ROC analysis showed that the AC correlates well with the number of ablation stages. Only AC and Shannon Entropy showed significant differences (p <0.01) between patients for whom more than one ablation stage was performed and for whom AF ceased after first ablation stage. At this point we can hypothesize, that there is a link between AC of intracardiac electrograms and the amount of the atrial tissue which has to be ablated in order to terminate AF. Nature of this relationship requires further study.
Shape modification of the γ ray spectral lines emitted during proton therapy
Co - Authors : Aleksandra Wrońska
In the Cyclotron Centre Bronowice in Cracow a series of measurements were performed, aiming to register γ spectra in the system modelling the course of proton therapy, using phantoms made of graphite and PMMA. Gamma quanta were detected with the use of a HPGe detector with antiCompton shielding located at 90° and at 60° polar laboratory angle, and beam energy of 70 MeV. The obtained spectra were analysed with regards to the position and shape of line stemming from deexcitation of the carbon excited state 4.44 MeV. In order to reproduce the shape of the carbon lines, a number of simulations were performed, each with different assumptions regarding the angular distributions for the two stages of the reaction occurring in the material: excitation of carbon nuclei by the incident protons and deexcitation of the exctited states.
The poster presents both the experimental data and the simulation results as well as conclusions, resulting from the comprinson of those.
18F-FMISO synthesis for small animals PET imaging
Co - Authors : Agnieszka Orlińska, Marina Gerszewska, Michał Cudny, Zbigniew Rogulski
Small animal positron emission tomography (PET) is a dynamically developing imaging method, widely applied in preclinical research. Although 18F[FDG], the glucose derivative labeled with 18F, is the basic radiopharmaceutical for diagnostic procedures, some drawbacks caused the need to seek other compounds dedicated for specfic applications. 18F-FMISO increased its clinical significance when the misonidasole uptake was identified as a standard method for visualization of hypoxia areas in tumor. In the Biological and Chemical Research Centre (CNBCh-UW) with universal 18F synthesis unit Synthra RNplus, 18F-FMISO was obtained from reaction of 18F with 1-(2'-nitro-1'-imidazolyl)-3-fluoro-2-propanol (NITTP).
In this paper there are shown results of synthesis and quality control of 18F-FMISO and specific modifications of synthesis path for increasing the specific activity, which is critical factor for small animals PET imaging.
Macrocyclic complexes as precursors for diagnostic radiopharmaceuticals
Co - Authors : Maria Pęgier, Magdalena Rodak
Porphyrins and its derivatives exhibit affinity for tumor cells. Hence, porphyrin labeled with suitable diagnostic radionuclide could be envisaged as potential agents for tumor imaging.
The main goal of this project was to obtain porphyrins complexes with copper or gallium with reasonable synthesis path, acceptable kinetics and purity. 64Cu and 68Ga are described in the literature as a potentially effective diagnostic radioisotopes, used in positron emission tomography (PET). The quality of imaging is in some applications, comparable to the quality of imaging with 18F isotope, which is one of the most frequently used in PET.
The reaction of porphyrins with Cu(II) and Ga(III) was studied spectrophotometrically and kinetics of the process was optimized. Using “cold” compounds, all required characteristics of the complexes were determined and full synthesis and purification path was defined.
Metallic and radionuclidic impurities in 18F-FDG production
Co - Authors : Mateusz Pęgier, Krystyna Pyrzyńska
The study presents identification, determination and distribution of metallic and radionuclidic contaminants in the synthesis of 18F-fluorodeoxyglucose. Samples of irradiated 18O-enriched water, purification columns (anionic, C18, Al2O3), final product and wastes were examined. Metallic contaminants were determined by ICP-MS and the radionuclide impurities by high resolution germanium gamma-spectrometer. In the samples 15 radionuclides were identified. The enriched water contained cationic contaminants (55Co, 56Co, 57Co, 58Co, 57Ni, 52Mn, 7Be) and the anionic (95Tc, 95mTc, 96Tc, 183Re) were mostly retained on the QMA column. The sources of contamination with metals and radionuclides were determined. Results obtained by ICP-MS generally confirmed the radionuclide distribution obtained by gamma spectrometry.
Quantum dots as an application in dosimetry
Co - Authors : Jerzy Szuniewicz, Agnieszka Korgul
The precise measurement of the dose is very important in the nuclear medicine. A new and innovative method for dosimetry application based on principles of nanotechnology is proposed here. It has been proven that gamma rays irradiating quantum dots (QD) change their optical properties.In this work, CdSe/ZnS QDs (590 nm) dispersed in chloroform and CdTe QDs (590nm) dispersed in water were investigated as possible candidates for dosimetry applications. QD samples were prepared for each QD type: two of them were unexposed controls, whereas the others were irradiated by a Cs-137, 662 keV gamma rays source – each sample with different dose. Fluorescence, absorption, time-resolved were collected after each irradiation. For both types of Quantum Dots we observed a decrease in intensity and red-shift of the main peak with increased irradiation dose. The three control samples exhibited consistent unchanged spectra during our experimental time scale. The fluorescent response of QDs to radiation provides the proof of principle for using QDs in dosimetry applications.
Heart rate variability during sleep: stochastic model
Co - Authors : Jan Gierałtowski, Jan Żebrowski
Normal sleep consists of four characteristic stages: light, deep, REM sleep and almost-awake state with additional arousal episodes. Neural activity is different for each sleep stage and it affects all physiological systems through autonomic nervous system including heart rate variability (HRV). We present the model of HRV considering statistic properties of sleep architecture. As a starting point, we used stochastic model by Kantelhardt et al. generating RR interval time series for different sleep stages. We create synthetic hipnograms by analyzing polysomnographic recordings from 30 healthy adults. We considered probabilities of transitions between all pairs of stages and probability distribution of stage durations. The comparison between synthetic RR time series and 34 RR time series from healthy adults showed that our model generates signals which are indistinguishable from real data using linear (mean, STD, RMSSD, pNN50) and nonlinear (Poincare Plot, MMA) HRV assessment methods.
Permanent Magnet Geometry, Size and Orientation Suitable for Magnetic Drug Targeting
Co - Authors : Krzysztof Turek
Permanent Magnet Geometry, Size, and Orientation Suitable for Magnetic Drug Targeting One of the promising area of magnetic nanoparticles applications is magnetic drug targeting. The idea of attaching therapeutics to magnetizable nanoparticles and then focusing them in the area of a tumor by a magnetic field has been explored since many years. However, results of clinical investigations on application of this method for cancer treatment are not impressive. One of the reasons seems to be using ad hoc selected magnets without detail knowledge of the magnetic field topology necessary for effective transportation of the magnetic particles – drug complexes throughout tumor blood vessels. The magnetic field used for the drug targeting should be strongly inhomogeneous since the force exerted on the particle is proportional to the field gradient. The force depends also in more complicated way on the magnetic field strength. As a consequence, to keep control over magnetic drug targeting both parameters should be known in the whole tumor volume. However, it is hard to find such characteristics in literature of the subject. In the paper gradients of the magnet fields generated by permanent Nd-Fe-B magnets of various geometries are measured or calculated. It is shown that a sufficiently large block or cylindrical magnet when properly oriented may generate the very large field gradient having the peak value of ~200T/m in a relatively large volume.
Electrochemical impedance investigation of cholesterol enriched supported films of lipids
Co - Authors : L. Vladimirova-Mihaleva, K. Bachev, V. Kochev
Electrochemical methods of analysis has received a great attention in the enormously large field of Life Sciences at least because of two reasons – first of all, owing to the exclusive role of bioelectrochemical processes at fundamental levels of living matter organization, and second due to specific features of these methods. Some of their advantages as noninvasiveness, sensitivity and inexpensiveness enlarged the reputation of analytical electrochemistry and established its techniques as indispensable tools for research of broad spectrum of problems in Biosciences. Electrochemical Impedance Spectroscopy (EIS), on its own, has long been recognized as an extremely informative tool, especially in areas of investigation where contacts between different phases are involved. Biomembranes and their artificial analogs are just such kind of interfaces where the EIS accuracy and sensitivity have already said their heavy word.
Preliminary design of the magnetic coils for J-PET-MRI system
Co - Authors :
The aim of this study was to find an optimum design, simulation and test a static and gradients coils for MRI which will give in the future a unique possibility for designing a J-PET [1-3] device combined with MRI system , where a simultaneous PET and MRI is providing great advantages and important diagnostic information about soft tissues and physiological functions throughout the body .The coils are extremely important components of MRI equipment. In this study, all simulations were conducted by using finite element method with consideration that our simulation results should be possible to be translated into real patterns in the nearest future with considering all technical limitations of the manufacturing process. As well as the comparison of theoretical results with simulations, flux maps and animations for the coils.
Hit time and hit position reconstruction in the J-PET detector based on the library of averaged model signals
Co - Authors : J-PET collaboration
The J- PET detector is a Positron Emission Tomograph with large field of view ( FOV) based on the long strips of polymer scintillators [1, 2]. A new detection technique requires elaboration of new gamma quanta hit time and hit position reconstruction methods which would allow to make use of the potential it offers. We will present a novel reconstruction method based on Mahalanobis distance  approach by comparing the random signal with library of averaged model signals. The method takes advantage of the fact that the amplitude and shape of the registered signal significantly change with the hit position in long scintillator detectors. The application of the method and results will be also presented and discussed.
The effect of light wavelenght on optical anisotropy of granular phosphor- based indirect x-ray detectors
Co - Authors : Stratos David, Ioannis Kandarakis
Image quality for medical purposes is related to the useful diagnostic information that can be extracted from an image. The performance of indirect X-ray detectors and thus the quality of the medical image can be significantly affected by the characteristics of the phosphor, employed to convert incident radiation into emitted light. In recent years, with the development of science and technology in the field of materials, several physical or chemical synthesis methods have been developed and successfully used for the preparation of various types of phosphors with different optical and structural phosphors. Therefore, new phosphor materials provide challenges to both fundamental research and breakthrough development of technologies in research areas of medical imaging.
The present paper provides an analysis of optical anisotropy of powder phosphor materials investigating the effect of light wavelength. The optical anisotropy was evaluated through the anisotropy factor which denotes the travel direction of light rays interacting with the phosphor grains. The overall examination was carried out using Mie scattering theory. The powder phosphors were considered with properties which correspond to the widely used Gd2O2S:Tb (GOS) conventional granular phosphor, summarzed in table 1: (a) light wavelength, 545 nm, (b) refractive index 2.3 (real part) and 10-6 (imaginary part) and (c) grain size 7 μm. However, for comparison reasons, two additonal grain sizes were considered: 1 μm and 700 nm, examining also the effect of light wavelength in the submicron scale.
The variation of light wavelength as a function of light wavelength is illustrated in figure 1. In the conventional GOS phosphor (grain size 7 μm), no variations were occurred. For grain size 1 μm, the anisotropy factor remains almost stable at light wavelengths in the region 500-600 nm. In the submicron scale (grain size 700 nm), the anisotropy factor was found to decrease with light wavelength presenting a minimum at 575 nm. Above this light wavelength, the anisotropy factor was found to slightly increase.
Determination of energy spectra in water during emission of the 6 MV X-rays from a medical LINAC for the wide open radiation field
Co - Authors : Adam Konefał
The purpose of the presented work is the determination of energy spectra in water for the 6 MV X-ray beam generated by the linear medical accelerators – Clinac 2300. The precise correlation between the dose distribution in water and the energy spectrum of a beam exists for radiation applied in radiotherapy. This fact is a base of the method used for the determination of energy spectra of therapeutic beams. Any direct measurement of these spectra is impossible to perform because of the strong photon flux. The method used in the presented investigations consists of two stages. At the first stage the dose distribution in water is calculated by means of Monte Carlo computer simulations and it is compared with the measured one. The good agreement between the calculated and measured dose distributions is a fundamental requirement to optimize the simulation program and to obtain the real spectra. At the second stage the spectra of the therapeutic beams are calculated.
Luminescent and scintillation properties of gagg:ce single crystals under x-ray excitation
S. L. David
Co - Authors : C. M. Michail, I. G. Valais, N. I. Kalivas, A. Bakas, P. Liaparinos, I. S. Kandarakis, K. Kourkoutas
Many of the contemporary photonic technologies, dealing with detection of radiation, owe their existence to diverse scintillation materials. The scintillators play a decisive role in the registration of X-rays necessary in many fields of application in industry, medicine, fundamental research, and security where they are used to convert high-energy photons into visible light . The purpose of the present study was to evaluate six (6) different scintillator crystal samples with 3x3 mm2 cross section of various thicknesses (from 4 mm up to 20 mm) of the new mixed Gd3Al2Ga3O12:Ce (GAGG:Ce) scintillator material under X-ray excitation for possible applications in combined medical imaging detectors i.e., integrated SPECT/CT or PET/CT detectors. Experimental measurements, such as emission specta of the samples and the Absolute Luminescence Efficiency-AE (light energy flux over exposure rate), were investigated under X-ray excitation .
The emission spectra of GAGG:Ce scintillators, examined in our study, are well matched with the spectral sensitivities of the optical photon detectors employed in radiation detectors. GAGG:Ce scintillators emit a light-yellowish color light (from 450 to 710 nm), with peak emission light at 520 nm. Experimental AE values of GAGG:Ce scintillator crystals, shown in figure 1, increased with X-ray tube voltage. The scintillator sample with dimensions equal to 3x3x10 mm3 presented best AE values in the whole energy range examined. Maximum AE value equal to 46.1 µWs/mRm2 was recorded for this crystal at 130 kVp X-ray tube voltage.
Best energy resolution value of 7.3% was measured under 662keV for a 3x3x20mm3 GAGG:Ce crystal sample. The energy resolution of 3x3x10mm3 GAGG:Ce crystal was measured equal to 9%. Taking into account its high efficiency under X-ray excitation, the very good energy resolution under 137Cs gamma ray irradiation and its spectral compatibility with the photodectors, GAGG:Ce could be potentially considered for use in combined medical imaging detectors i.e. integrated SPECT/CT or PET/CT detectors. In conclusion the sample with 10mm height is proposed to the aforementioned applications.
Influence of heart valve replacement surgery on the duration of myocardial depolarization
Co - Authors :
Valvular disease is the third in terms of incidence of heart disease in developed countries after hypertension and ischemic heart disease. A group of 63 patients qualified for aortic or mitral valve replacement surgery were studied. Some of the patients also had a coronary artery bypass grafting made at the same time. Due to generation of an alternating electric field in the heart patients underwent electrocardiography (ECG). Changes in ECG before and after the surgery together with a detailed analysis of the waves duration showed certain risk factors associated with the duration of depolarization in the myocardium. Additionally examined whether concomitant diseases such as diabetes and hypertension have an influence on the course of the patient's recovery. The study shows that the standard ECG provides a wide response on the prognostic risk conditions and allows to evaluate the state of the myocardium immediately after the surgery.
The out-of-field dose measurement of photon therapy.
Co - Authors : A. Kowalik, M. Kruszyna, S. Adamczyk
The purpose of the work was to determine the out-of-field doses for photon and neutron radiation during radiotherapy with 6 and 20MV beam. The measurement was performed in special made-up water phantom and photon dose was verified with thermoluminescent dosimeters (TLD 100, 600 and 700, Harshaw) and Gafchromic EBT films (ISP). There were 6 measurement points, which were placed in distance from isocentre: (P2)10cm, (P3)15cm, (P4)20cm, (P5)25cm, (P6)30cm, (P7)35cm. Our results show that in close-to-field area the dose level could achieve even 1.5Gy for total dose 75Gy given at isocentre. The total out-of-field doses for 75Gy for target were estimated (respectively in P2 and P7) to be about: for 6MV - TLD 100...
1 hour 30 minutes