rss_2.0Polish Journal of Medical Physics and Engineering FeedSciendo RSS Feed for Polish Journal of Medical Physics and Engineering Journal of Medical Physics and Engineering Feed evaluation method using multiple image analyses for panoramic radiography improvement<abstract> <title style='display:none'>Abstract</title> <sec> <title style='display:none'>Introduction</title> <p>In the standardization of panoramic radiography quality, the education and training of beginners on panoramic radiographic imaging are important. We evaluated the relationship between positioning error factors and multiple image analysis results for reproducible panoramic radiography.</p> </sec> <sec> <title style='display:none'>Material and methods</title> <p>Using a panoramic radiography system and a dental phantom, reference images were acquired on the Frankfurt plane along the horizontal direction, midsagittal plane along the left–right direction, and for the canine on the forward–backward plane. Images with positioning errors were acquired with 1–5 mm shifts along the forward– backward direction and 2–10° rotations along the horizontal (chin tipped high/low) and vertical (left–right side tilt) directions on the Frankfurt plane. The cross-correlation coefficient and angle difference of the occlusion congruent plane profile between the reference and positioning error images, peak signal-to-noise ratio (PSNR), and deformation vector value by deformable image registration were compared and evaluated.</p> </sec> <sec> <title style='display:none'>Results</title> <p>The cross-correlation coefficients of the occlusal plane profiles showed the greatest change in the chin tipped high images and became negatively correlated from 6° image rotation (r = −0.29). The angle difference tended to shift substantially with increasing positioning error, with an angle difference of 8.9° for the 10° chin tipped low image. The PSNR was above 30 dB only for images with a 1-mm backward shift. The positioning error owing to the vertical rotation was the largest for the deformation vector value.</p> </sec> <sec> <title style='display:none'>Conclusions</title> <p>Multiple image analyses allow to determine factors contributing to positioning errors in panoramic radiography and may enable error correction. This study based on phantom imaging can support the education of beginners regarding panoramic radiography.</p> </sec> </abstract>ARTICLEtrue of virtual rhinomanometry<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> This paper describes the results of research aimed at developing a method of otolaryngological diagnosis based on computational fluid dynamics, which has been called Virtual Rhinomanometry.</p> <p><italic>Material and methods:</italic> Laboratory studies of airflows through a 3D printed model of nasal cavities based on computed tomography image analysis have been performed. The CFD results have been compared with those of an examination of airflow through nasal cavities (rhinomanometry) of a group of 25 patients.</p> <p><italic>Results:</italic> The possibilities of simplifying model geometry for CFD calculations have been described, the impact of CT image segmentation on geometric model accuracy and CFD simulation errors have been analysed, and recommendations for future research have been described.</p> <p><italic>Conclusions:</italic> The measurement uncertainty of the nasal cavities’ walls has a significant impact on CFD simulations. The CFD simulations better approximate RMM results of patients after anemization, as the influence of the nasal mucosa on airflow is then reduced. A minor change in the geometry of the nasal cavities (within the range of reconstruction errors by CT image segmentation) has a major impact on the results of CFD simulations.</p> </abstract>ARTICLEtrue thermal imaging be useful in early diagnosis of lower extremities chronic venous disease?<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> World statistics confirmed that about 40-50% of men and 50-55% of women suffer from chronic venous disease. Currently, the Duplex ultrasound is the leading diagnostic method for chronic venous disease (CVD), but it has some limitations. Therefore, it is important to find a new diagnostic technique that will provide additional parameters, describing not only structural but also early metabolic and functional changes.</p> <p><italic>Materials and Methods:</italic> This study aimed to demonstrate the usefulness of the thermal imaging technique in the diagnosis of chronic venous disease. Results were obtained for two groups: 61 patients suffering from the primary chronic venous disease (CVD group) and 30 healthy people (control group). The obtained results compared the thermal imaging parameters to data obtained from the ultrasound examination. Parameters such as the reflux duration and extent of the CEAP classification were correlated with the mean temperature of the limb, the mean temperature of the lesion (determined using two methods), and the thermal range. Based on data obtained during the study, correlation coefficients were calculated for individual parameters.</p> <p><italic>Results:</italic> The results obtained show that the mean limb temperature, and especially the mean temperature of a proposed isothermal area, is significantly correlated with the range of reflux. The conducted tests showed the correlation between some thermal and ultrasonic parameters determined by Spearman's coefficient is 0.4 (p &lt; 0.05).</p> <p><italic>Conclusions:</italic> Thus, parameters such as the isothermal area and the thermal range may be used as a preliminary quantitative diagnosis, similarly to those derived from the Duplex ultrasound.</p> </abstract>ARTICLEtrue Software with a Graphical User Interface for GAMOS: Basic Training and an Educational Tool for Medical Physicists<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> It is necessary to have special experience to perform the Monte Carlo calculation, commonly used in medical physics and accepted as the gold standard. In this study, we developed software to teach basic steps to medical physicists who were inexperienced in the medical linear accelerator Monte Carlo simulation.</p> <p><italic>Material and methods:</italic> For the design interface, a software called GamosLinacGUI was developed using Gnome Builder, Python, and GTK. The user, who wants to learn the basics of GAMOS and simulate a linear accelerator, can enter the values in the software, select some options and quickly create geometry and physics files.</p> <p><italic>Results:</italic> For proof that the software generates the correct inputs for GAMOS simulation in the same conditions for the measurements and calculations. Required files for GAMOS have been created and tested and run the simulation accordingly. This software was tested with Centos Linux.</p> <p><italic>Conclusions:</italic> GamosLinacGUI has been successfully developed, which creates the geometry and physics files required for the simulation with GAMOS as a training and learning tool.</p> </abstract>ARTICLEtrue in-house step-wedge phantom for the calibration of pixel values in CT localizer radiographs for water-equivalent diameter measurement<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> To develop an in-house acrylic-based step-wedge phantom with several thickness configurations for calibrating computed tomography (CT) localizer radiographs in order to measure the water-equivalent diameter (D<sub>w</sub>) and the size-specific dose estimate (SSDE).</p> <p><italic>Method:</italic> We developed an in-house step-wedge phantom using 3 mm thick acrylic, filled with water. The phantom had five steps with thicknesses of 6, 12, 18, 24, and 30 cm. The phantom was scanned using a 64-slice Siemens Definition AS CT scanner with tube currents of 50, 100, 150, 200, and 250 mA. The relationship between pixel value (PV) and water-equivalent thickness (t<sub>w</sub>) was obtained for the different step thicknesses. This was used to calibrate the CT localizer radiographs in order to measure D<sub>w</sub> and SSDE. The results of D<sub>w</sub> and SSDE from the radiographs were compared with those calculated from axial CT images.</p> <p><italic>Results:</italic> The relationship between PV and t<sub>w</sub> from CT localizer radiographs of the phantom step-wedge produced a linear relationship with R<sup>2</sup> &gt; 0.990. The linear relationships of the D<sub>w</sub> and SSDE values obtained from CT localizer radiographs and axial CT images had R<sup>2</sup> values &gt; 0.94 with a statistical test of <italic>p</italic>-value &gt; 0.05. The D<sub>w</sub> difference between those from CT localizer radiographs and axial CT images was 3.7% and the SSDE difference between both was 4.3%.</p> <p><italic>Conclusion:</italic> We have successfully developed a step-wedge phantom to calibrate the relationship between PV and t<sub>w</sub>. Our phantom can be easily used to calibrate CT localizer radiographs in order to measure D<sub>w</sub> and SSDE.</p> </abstract>ARTICLEtrue Changes of Elongation Index of erythrocytes caused by storage of blood at low temperature<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> An important parameter characterizing the ability of erythrocytes to deform depending on the blood flow conditions is the Elongation Index (EI), and it is a parameter defined by the shape of the erythrocyte obtained as a diffraction pattern of erythrocytes at different values of shear stresses.</p> <p><italic>Material and methods:</italic> EI measurements at different shear stress were performed by Laser-assisted Optical Rotational Cell Analyzer (LORRCA) for erythrocytes derived from Tissue Bank in Katowice. Measurements were performed immediately after receiving them from Tissue Bank and after 2, 9, and 28 days of storage of samples at the temperature of 4°C in solution with the anticoagulant.</p> <p><italic>Results:</italic> An increase in the erythrocytes Elongation Index in the first 9 days of storing samples at low temperatures was observed in the entire range of applied shear stresses. This indicates an increase in the elasticity of erythrocytes during short-term storage at 4°C. In turn, on the 28th day of erythrocyte storage, a significant decrease in the Elongation Index for shear stresses greater than 1 Pa was observed, which indicates the stiffening of the erythrocyte membrane structure, reducing their elasticity. The relative decrease in the Elongation Index of erythrocytes stored for 28 days compared to erythrocytes measured at the beginning was similar and slightly greater than 30% for shear stresses greater than 3 Pa. For shear stresses lower than 3 Pa, the relative change in elongation index was smaller than for shear stresses greater than 3 Pa and increased with the increase in shear stress.</p> <p><italic>Conclusions:</italic> The elongation index of erythrocytes stored in the anticoagulant solution at 4°C, initially increases in the entire range of applied shear stresses in the first few days from the moment of blood collection and preparation at the Tissue Bank, and then decreases, but on the ninth day of storage the elongation index is still higher than for blood immediately after collection.</p> </abstract>ARTICLEtrue determination of virtual source position using convergent anti-trigonometric functions (arcCOS and arcSIN) method for scanning-passive scatter beam in carbon ion therapy<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> We developed a convergent trigonometric functions technique (arcCOS, arcSIN) capable of dealing with the virtual source position delivered by different carbon ion energies from the pattern of scanning-passive scatter beam in this study.</p> <p><italic>Materials and Methods:</italic> A home-made large-format CMOS sensor and Gaf Chromic EBT3 films were used for the virtual source position measurement. The Gaf films were embedded in a self-designed rectangular plastic frame to tighten the films and set up on a treatment couch for irradiation in the air with the film perpendicular to the carbon ion beam at the nominal source-axis-distance (SAD) as well as upstream and downstream from the SAD. The horizontal carbon ion beam with 5 energies at a machine opening field size was carried out in this study. The virtual source position was determined with a convergent arcCOS and arcSIN methods and compared with the linear regression by back-projecting the FWHM to zero at a distance upstream from the various source-film-distance.</p> <p><italic>Results:</italic> The film FWHM measurement error of 0.5 mm (the large-format CMOS detectors was in pixel, a pixel equals 0.5 mm) leads to 1×10<sup>-3</sup>% deviation of α(cACOS and cASIN) at every assumed virtual source position. The overall uncertainty for the reproducibility of the calculated virtual source position by the assumed t in the vertical and horizontal directions amounts to 0.1%. The errors of calculated virtual source position by assumed t with back projecting FWHM to zero methods were within 1.1 ± 0.001, <italic>p</italic> = 0.033. The distance of virtual source positions is decreased from SAD with high to low energy.</p> <p><italic>Conclusion:</italic> We have developed a technique capable of dealing with the virtual source position with a convergent arcCOS and arcSIN methods to avoid any manual measurement mistakes in scanning-passive scatter carbon ion beam. The method for investigating the virtual source position in the carbon ion beam in this study can also be used for external electrons and the proton.</p> </abstract>ARTICLEtrue of national diagnostic dose reference levels (DRLs) for routine computed tomography examinations in Jordan<abstract> <title style='display:none'>Abstract</title> <p><italic>Background:</italic> Dose reference levels (DRLs) are used as indicators as well as guidance for dose optimization and to ensure justification of appropriate dose for a given clinical indication. The main aims of this study were to establish local DRLs for each CT imaging protocol as a reference point to evaluate the radiation dose indices and to compare our DRLs with those established in other countries and against the internationally reported guidelines.</p> <p><italic>Materials and methods:</italic> 2000 CT dose reports of different adult imaging protocols from January 2021 until April 2022 were collected retrospectively at different hospitals in Jordan. Data were collected from CT scans that were performed using different types and models of CT scanners and included four adult non-enhanced, helical CT imaging protocols; Head, Chest, Abdomen-Pelvis, and Chest-Abdomen-Pelvis.</p> <p><italic>Results:</italic> The average doses of CTDI<sub>vol</sub>, DLP, and effective dose were (65.11 mGy, 1232.71 mGy·cm, 2.83 mSv) for the head scan, (16.6 mGy, 586.6 mGy·cm, 8.21 mSv) for the chest scan, (17.91 mGy, 929.9 mGy·cm, 13.9 mSv) for the abdomen-pelvis scan, and (19.3 mGy, 1152 mGy·cm, 17.25 mSv) for the chest-abdomen-pelvis scan. In comparison with results from different international studies, DLP values measured in the present study were lower for the chest-abdomen-pelvis and abdomen-pelvis CT scans, and higher for the head CT and chest CT scans.</p> <p><italic>Conclusions:</italic> It is very important that each country establishes its own DRLs and compares them with those reported by other countries, especially the developed ones. It is also important that these levels are regularly updated.</p> </abstract>ARTICLEtrue method for blood glucose monitoring using ECG signal<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> Tight glucose monitoring is crucial for diabetic patients by using a Continuous Glucose Monitor (CGM). The existing CGMs measure the Blood Glucose Concentration (BGC) from the interstitial fluid. These technologies are quite expensive, and most of them are invasive. Previous studies have demonstrated that hypoglycemia and hyperglycemia episodes affect the electrophysiology of the heart. However, they did not determine a cohort relationship between BGC and ECG parameters.</p> <p><italic>Material and method:</italic> In this work, we propose a new method for determining the BGC using surface ECG signals. Recurrent Convolutional Neural Networks (RCNN) were applied to segment the ECG signals. Then, the extracted features were employed to determine the BGC using two mathematical equations. This method has been tested on 04 patients over multiple days from the D1namo dataset, using surface ECG signals instead of intracardiac signal.</p> <p><italic>Results:</italic> We were able to segment the ECG signals with an accuracy of 94% using the RCNN algorithm. According to the results, the proposed method was able to estimate the BGC with a Mean Absolute Error (MAE) of 0.0539, and a Mean Squared Error (MSE) of 0.1604. In addition, the linear relationship between BGC and ECG features has been confirmed in this paper.</p> <p><italic>Conclusion:</italic> In this paper, we propose the potential use of ECG features to determine the BGC. Additionally, we confirmed the linear relationship between BGC and ECG features. That fact will open new perspectives for further research, namely physiological models. Furthermore, the findings point to the possible application of ECG wearable devices for non-invasive continuous blood glucose monitoring via machine learning.</p> </abstract>ARTICLEtrue of a commercial EPID-based in-vivo dosimetry and its feasibility and implementation for treatment verification in Malaysia<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> In vivo dosimetry verification is currently a necessity in radiotherapy centres in Europe countries as one of the tools for patient-specific QA, and now its demand is currently rising in developed countries, such as Malaysia. The aim of this study is to characterize commercial EPID-based dosimetry and its implementation for radiotherapy treatment verification in Malaysia.</p> <p><italic>Materials and Methods:</italic> In this work, the sensitivity and performance of a commercially available in vivo dosimetry system, EPIgray® (DOSIsoft, Cachan, France), were qualitatively evaluated prior to its use at our centre. EPIgray response to dose linearity, field size, off-axis, position, and angle dependency tests were performed against TPS calculated dose for 6 MV and 10 MV photon beams. Relative deviations of the total dose were evaluated at isocentre and different depths in the water. EPIgray measured dose was validated by using IMRT and VMAT prostate plan. All calculation points were at the beam isocentre and at points suggested by TG-119 with accepted tolerance of ±10% dose threshold.</p> <p><italic>Results:</italic> EPIgray reported good agreement for linearity, field size, off-axis, and position dependency with TPS dose, being within 5% tolerance for both energy ranges. The average deviation was less than ±2% and ±7% in 6 MV and 10 MV photon beams, respectively, for the angle dependency test. A clinical evaluation performed for the IMRT prostate plan gave average agreement within ±3% at the plan isocentre for both energies. While for the VMAT plan, 95% and 100% of all points created lie below ±5% for 6 MV and 10 MV photon beam energy, respectively.</p> <p><italic>Conclusion:</italic> In summary, based on the results of preliminary characterization, EPID-based dosimetry is believed as an important tool and beneficial to be implemented for IMRT/VMAT plans verification in Malaysia, especially for in vivo verification, alongside existing pre-treatment verification.</p> </abstract>ARTICLEtrue patient centering of computed tomography images and its implementation to evaluate clinical practices in three hospitals in Indonesia<abstract> <title style='display:none'>Abstract</title> <p><italic>Purpose:</italic> This study aims to develop a software tool for investigating patient centering profiles of axial CT images and to implement it to evaluate practices in three hospitals in Indonesia.</p> <p><italic>Methods:</italic> The evaluation of patient centering accuracy was conducted by comparing the center coordinate of the patient’s image to the center coordinates of the axial CT image. This process was iterated for all slices to yield an average patient mis-centering in both the x- and y-axis. We implemented the software to evaluate the profile of centering on 268 patient images from the head, thorax, and abdomen examinations taken from three hospitals.</p> <p><italic>Results:</italic> We found that 82% of patients were mis-centered in the y-axis (i.e., placed more than 5 mm from the iso-center), with 49% of patients placed 10–35 mm from the iso-center. Most of the patients had a tendency to be placed below the iso-centers. In head examinations, patients were more precisely positioned than in the other examinations. We did not find any significant difference in mis-centering between males and females. We found that there was a slight difference between mis-centering in adult and pediatric patients.</p> <p><italic>Conclusion:</italic> Software for automated patient centering was successfully developed. Patients in three hospitals in Indonesia had a tendency to be placed under the iso-center of the gantry.</p> </abstract>ARTICLEtrue impact of rotational set-up errors in high-risk prostate cancer<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> Cone-beam computed tomography (CBCT) provides an excellent solution to quantitative assessment and correction of patient set-up errors during radiotherapy. However, most linear accelerators are equipped with conventional therapy tables that can be moved in three translational directions and perform only yaw rotation. Uncorrected roll and pitch result in rotational set-up errors, particularly when the distance from the isocenter to the target border is large. The aim of this study was to investigate the impact of rotational errors on the dose delivered to the clinical target volume (CTV), the planning target volume (PTV) and organs at risk (OAR).</p> <p><italic>Material and methods:</italic> 30 patients with prostate cancer treated with VMAT technique had daily CBCT scans (840 CBCTs in total) prior to treatment delivery. The rotational errors remaining after on-line correction were retrospectively analysed. The sum plans simulating the dose distribution during the treatment course were calculated for selected patients with significant rotational errors.</p> <p><italic>Results:</italic> The dose delivered to the prostate bed CTV reported in the sum plan was not lower than in the original plan for all selected patients. For four patients from the selected group, the D98% for prostate bed PTV was less than 95%. The V47.88Gy for pelvic lymph nodes PTV was less than 98% for two of the selected patients.</p> <p><italic>Conclusions:</italic> The analysis of the dosimetric parameters showed that the impact of uncorrected rotations is not clinically significant in terms of the dose delivered to OAR and the dose coverage of CTV. However, the PTV dose coverage is correlated with distance away from the isocenter and is smaller than planned.</p> </abstract>ARTICLEtrue and pre-evaluation of an in-house cylindrical ionization chamber fabricated from locally available materials<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> The objectives of this study were to construct a very robust in-house cylindrical ionization chamber from locally available materials to minimize cost, and to assess its suitability for use in a clinical setting.</p> <p><italic>Materials and Methods:</italic> The entire body of the constructed IC was composed of Perspex (PMMA). Other components of the IC were made from locally available materials, such as paper and discarded items. The in-house IC was made waterproof by passing the triaxial cable connecting its various electrodes through a plastic tube which once served as a drainage tube of a urine bag. This connection was made such that the chamber was vented to the environment. The completed in-house IC was evaluated for: polarity effect, ion recombination, ion collection efficiency, stability, dose linearity, stem effect, leakage current, angular, dose rate and energy dependences.</p> <p><italic>Results:</italic> Although the pre-evaluation results confirmed that the in-house IC satisfied the stipulated international standards for ICs, there was a need to enhance the stem effect and leakage current characteristics of the IC. The in-house IC was found to have an absorbed dose to water calibration coefficient of 4.475 x 10<sup>7</sup> Gy/C (uncertainty of 1.6%) for cobalt 60 through a cross-calibration with a commercial 0.6 cc cylindrical IC with traceability to the Germany National Dosimetry Laboratory. Using a Jaffé diagram, the in-house IC was also found to have a recombination correction factor of 1.0078 when operated at the calibration voltage of + 400 V. In terms of beam quality correction factors for megavoltage beams, the in-house IC was found to exhibit characteristics similar to those of Scanditronix-Wellhofer IC 70 Farmer type IC.</p> <p><italic>Conclusion:</italic> The constructed in-house Farmer-type IC was able to meet all the recommended characteristics for an IC, and therefore, the in-house IC is suitable for beam output calibration in external beam radiotherapy.</p> </abstract>ARTICLEtrue of a standard phantom for diffusion-weighted magnetic resonance imaging quality control studies: A review<abstract> <title style='display:none'>Abstract</title> <p>Various materials and compounds have been used in the design of diffusion-weighted magnetic resonance imaging (DWMRI) phantoms to mimic biological tissue properties, including diffusion. This review thus provides an overview of the preparations of the various DW-MRI phantoms available in relation to the limitations and strengths of materials/solutions used to fill them. The narrative review conducted from relevant databases shows that synthesizing all relevant compounds from individual liquids, gels, and solutions based on their identified strengths could contribute to the development of a novel multifunctional DW-MRI phantom. The proposed multifunctional material at varied concentrations, when filled into a multi-compartment Perspex container of cylindrical or spherical geometry, could serve as a standard DW-MRI phantom. The standard multifunctional phantom could potentially provide DW-MRI quality control test parameters in one study session.</p> </abstract>ARTICLEtrue diagnostic reference levels in diagnostic and therapeutic pediatric cardiology at a specialist pediatric hospital in South Africa<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> Children may be at a higher risk of experiencing the detrimental effects of ionizing radiation arising from medical radiation imaging. Dose optimisation is therefore recommended to provide assurance that their exposure is as low as reasonably achievable. To this end, periodic assessment of dose levels and establishment of Local Diagnostic Reference Levels (LDRLs) in medical facilities is necessary. There is a general paucity in the literature of data pertaining to dose levels in pediatric interventional radiology. This study establishes LDRLs in diagnostic and therapeutic heart catheterization procedures at a specialist pediatric hospital in a resource constrained country.</p> <p><italic>Material and methods:</italic> Dose indicators from actual patient procedures were collected from the archive and analyzed retrospectively to determine the median, 25th, and 75th percentiles of the total Air Kerma Area Product (KAP), Cumulative Air Kerma (CAK), total Fluoroscopy Time (FT), and a total number of Cine Images (CI) of selected interventional procedures. The dose indicators were also age-stratified into five age groups defined by the International Commission on Radiation Protection publication 135. The results were compared to values available from similar studies in the literature to benchmark our dose levels. Local Dose Reference Levels were set as the 75th percentile values.</p> <p><italic>Results:</italic> For diagnostic procedures (n = 80), the 75th percentiles of KAP, CAK, FT, and CI were 4.0 Gy·cm<sup>2</sup>, 31.5 mGy, 14.3 min, and 315 frames, respectively and 3.2 Gy·cm<sup>2</sup>, 30.5 mGy, 17.5 min, and 606 frames, respectively for therapeutic procedures (n = 143).</p> <p><italic>Conclusions:</italic> The LDRLs from this study did not vary significantly from those published in the literature, suggesting that practices at our center were comparable to international norms. Regular reviews of the LDRLs must be conducted to check that the dose levels do not deviate considerably.</p> </abstract>ARTICLEtrue influence of the used applicators on organ and target doses for cervical cancer patients treated with HDR brachytherapy<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> The aim of this work was to study the influence of the applicators used for cervical cancer patients treated with high dose-rate brachytherapy (HDR-BT) in the Maria Sklodowska-Curie National Research Institute of Oncology in Warsaw, Poland on doses in the tumour volumes and organs at risk.</p> <p><italic>Material and methods:</italic> The treatment was carried out using Iridium-192 in 4 fractions (7.5 Gy each) given in weekly intervals. Two types of applicators were used for comparison: fletcher and ring. The standard dose distribution parameters, read from the system Oncentra Brachy (version 4.5, Elekta), for bladder, rectum, and sigmoid (D<sub>2 cc</sub>) and tumour (HRCTV D<sub>100</sub>, D<sub>98</sub>, D<sub>90</sub>) were studied. Patients were divided into two groups (240 treatment plans) depending on the type of applicator used and into four groups according to the tumour volumes (HR-CTV &lt; 25 cm<sup>3</sup> or HR-CTV ≥ 25 cm<sup>3</sup>). The collected data were analysed using the PQStatSoftware (version 1.8.2).</p> <p><italic>Results:</italic> The treatment plans prepared with all types of applicators fulfil the dose distribution requirements, however, the dose delivered to the tumour using the ring applicator was found to be the highest. For the bladder and sigmoid the optimal dose distribution was obtained when using the fletcher applicator, while for the rectum the ring applicator gave the smallest dose value. The D<sub>2 cc</sub> parameter for sigmoid obtained for fletcher treatment has smaller values in the case of patients with small tumour volume and for this type of applicator was observed a statistically significant difference when compared with the ring.</p> <p><italic>Conclusions:</italic> The ring applicator gives the optimal parameters of the dose distribution independently on the tumour volume with respect to the fletcher applicator, which is however more often used in clinical practice.</p> </abstract>ARTICLEtrue aspects of Bragg curve of therapeutic oxygen-ion beam: Monte Carlo simulation<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> Oxygen (<sup>16</sup>O) ion beams have been recommended for cancer treatment due to its physical Bragg curve feature and biological property. The goal of this research is to use Monte Carlo simulation to analyze the physical features of the <sup>16</sup>O Bragg curve in water and tissue.</p> <p><italic>Material and methods:</italic> In order to determine the benefits and drawbacks of ion beam therapy, Monte Carlo simulation (PHITS code) was used to investigate the interaction and dose deposition properties of oxygen ions beam in water and human tissue medium. A benchmark study for the depth–dose distribution of a <sup>16</sup>O ion beam in a water phantom was established using the PHITS code. Bragg’s peak location of <sup>16</sup>O ions in water was simulated using the effect of water’s mean ionization potential. The contribution of secondary particles produced by nuclear fragmentation to the total dose has been calculated. The depth and radial dose profiles of <sup>16</sup>O, <sup>12</sup>C, <sup>4</sup>He, and <sup>1</sup>H beams were compared.</p> <p><italic>Results:</italic> It was shown that PHITS accurately reproduces the measured Bragg curves. The mean ionization potential of water was estimated. It has been found that secondary particles contribute 10% behind the Bragg peak for <sup>16</sup>O energy of 300 MeV/u. The comparison of the depth and radial dose profiles of <sup>16</sup>O, <sup>12</sup>C, <sup>4</sup>He, and <sup>1</sup>H beams, shows clearly, that the oxygen beam has the greater deposited dose at Bragg peak and the minor lateral deflection.</p> <p><italic>Conclusions:</italic> The combination of these physical characteristics with radio-biological ones in the case of resistant organs located behind the tumor volume, leads to the conclusion that the <sup>16</sup>O ion beams can be used to treat deep-seated hypoxic tumors.</p> </abstract>ARTICLEtrue of fulfilling the criteria for critical organs in irradiation of patients with breast cancer using the deep inspiration breath-hold and free breathing techniques<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> The aim of the study was to evaluate organ-at-risk dose sparing in treatment plans for patients with left-sided breast cancer irradiated with Deep Inspiration Breath Hold (DIBH) and Free Breathing (FB) techniques.</p> <p><italic>Material and methods:</italic> Twenty patients with left-sided breast cancer were analyzed and divided into two groups. Group A included 10 patients with non-metastatic breast cancer, while group B involved 10 patients with metastatic breast cancer spreading to regional lymph nodes. All patients went through the DIBH coaching. For planning purposes, CT scans were obtained in both DIBH and FB. Mean heart dose (Dmean,heart), mean heart volume receiving 50% of the prescribed dose (V<sub>50</sub>), V20 (V20L.lung), V10 (V10L.lung) and V5 for left lung (V5L.lung), the volume of the PTV receiving a dose greater than or equal to 95% of the prescribed dose (V<sub>95</sub> [%]), the maximum point dose (D<sub>max</sub>), and the volume of PTV receiving 107% of the prescribed dose were reported.</p> <p><italic>Results:</italic> In all 20 analyzed pairs of plans, a reduction by more than half in the mean heart dose in DIBH technique plans was achieved, as well as a significant reduction was found in DIBH plans for the heart V<sub>50</sub>. In 19 patients, the use of the DIBH technique also reduced the volume of the left lung receiving doses of 20 Gy, 10 Gy, and 5 Gy compared to the FB technique.</p> <p><italic>Conclusions:</italic> Dosimetric analysis showed that the free breathing plans don’t fulfill the criteria for a mean heart dose (group B) and the left lung receiving a 20 Gy dose (group A) compared to the DIBH plans. Radiation therapy of left breast cancer with the use of the DIBH technique results in a significant dose reduction in the heart and also reduces the dose in the left lung in the majority of patients, compared to the FB procedure.</p> </abstract>ARTICLEtrue of the polarity effect of Roos parallel plate ionization chamber in build-up region<abstract> <title style='display:none'>Abstract</title> <p><italic>Purpose:</italic> Despite widespread studying of the polarity effect of Roos parallel plate ion chamber in electron beams as mentioned in several protocols, no investigations have up till now studied this effect in photon beams in the build-up region. It is important to examine its polarity effect in the build-up region for photon beams, so this is the first work that focuses in to evaluate the polarity effect of the Roos chamber in the surface and build-up region and comparing its effect with other chambers.</p> <p><italic>Methods:</italic> In this study, the Roos chamber was irradiated by a Theratron 780E <sup>60</sup>Co beam to a known polarity effect. The Polarity effects of 5×5 up to 35×35 cm<sup>2</sup> field sizes at positive and negative polarizing voltages were measured in the build-up region from surface to 0.7 cm in a solid water phantom.</p> <p><italic>Results:</italic> The polarity ratios (PRs) were obtained at 1.020 ± 0.00 and 1.015 ± 0.00 for field sizes 5 × 5 up to 35 × 35 cm<sup>2</sup>, respectively. For the same fields, the percentage of polarity effects (%PEs) was obtained at 1.99% ± 0.00% and 1.47% ± 0.02%, respectively. The results found that the %PEs decrease with increased field sizes and depths. Moreover, the %PEs exhibited a decrease with an increased percentage surface dose (%SD). The uncertainty of %PE was estimated as 0.01% for all measurements in this study.</p> <p><italic>Conclusions:</italic> As a result, the average %PE of the Roos chamber described here is equal to 0.756% ± 0.013% for all depths and field sizes for the <sup>60</sup>Co γ-ray beam. It has introduced a less percentage of polarity effect than other chambers.</p> </abstract>ARTICLEtrue