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 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 of slice thickness measurements in computed tomography images of AAPM CT performance phantom using a non-rotational method<abstract> <title style='display:none'>Abstract</title> <p><italic>Purpose:</italic> The current study proposes a method for automatically measuring slice thickness using a non-rotational method on the middle stair object of the AAPM CT performance phantom image.</p> <p><italic>Method:</italic> The AAPM CT performance phantom was scanned by a GE Healthcare 128-slice CT scanner with nominal slice thicknesses of 0.625, 1.25, 2.5, 3.75, 5, 7.5 and 10 mm. The automated slice thickness was measured as the full width at half maximum (FWHM) of the profile of the middle stair object using a non-rotational method. The non-rotational method avoided rotating the image of the phantom. Instead, the lines to make the profiles were automatically rotated to confirm the stair’s location and rotation. The results of this non-rotational method were compared with those from a previous rotational method.</p> <p><italic>Results:</italic> The slice thicknesses from the non-rotational method were 1.55, 1.86, 3.27, 4.86, 6.58, 7.57, and 9.66 mm for nominal slice thicknesses of 0.625, 1.25, 2.4, 3.75, 5, 7.5, and 10 mm, respectively. By comparison, the slice thicknesses from the rotational method were 1.53, 1.87, 3.32, 4.98, 6.77, 7.75, and 9.80 mm, respectively. The results of the nonrotational method were slightly lower (i.e. 0.25%) than the results of the rotational method for each nominal slice thickness, except for the smallest slice thickness.</p> <p><italic>Conclusions:</italic> An alternative algorithm using a non-rotational method to measure the slice thickness of the middle stair object in the AAPM CT performance phantom was successfully implemented. The slice thicknesses from the nonrotational method results were slightly lower than the rotational method results for each nominal slice thickness, except at the smallest nominal slice thickness (0.625 mm).</p> </abstract>ARTICLEtrue diagnosis of severity of COVID-19 patients using an ensemble of transfer learning models with convolutional neural networks in CT images<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> Quantification of lung involvement in COVID-19 using chest Computed tomography (CT) scan can help physicians to evaluate the progression of the disease or treatment response. This paper presents an automatic deep transfer learning ensemble based on pre-trained convolutional neural networks (CNNs) to determine the severity of COVID -19 as normal, mild, moderate, and severe based on the images of the lungs CT.</p> <p><italic>Material and methods:</italic> In this study, two different deep transfer learning strategies were used. In the first procedure, features were extracted from fifteen pre-trained CNNs architectures and then fed into a support vector machine (SVM) classifier. In the second procedure, the pre-trained CNNs were fine-tuned using the chest CT images, and then features were extracted for the purpose of classification by the softmax layer. Finally, an ensemble method was developed based on majority voting of the deep learning outputs to increase the performance of the recognition on each of the two strategies. A dataset of CT scans was collected and then labeled as normal (314), mild (262), moderate (72), and severe (35) for COVID-19 by the consensus of two highly qualified radiologists.</p> <p><italic>Results:</italic> The ensemble of five deep transfer learning outputs named EfficientNetB3, EfficientNetB4, InceptionV3, NasNetMobile, and ResNext50 in the second strategy has better results than the first strategy and also the individual deep transfer learning models in diagnosing the severity of COVID-19 with 85% accuracy.</p> <p><italic>Conclusions:</italic> Our proposed study is well suited for quantifying lung involvement of COVID-19 and can help physicians to monitor the progression of the disease.</p> </abstract>ARTICLEtrue of therapeutic linear accelerators for the production of radioisotopes used in nuclear medicine<abstract> <title style='display:none'>Abstract</title> <p>This review paper summarizes the possibilities of the use of therapeutic linear electron accelerators for the production of radioisotopes for nuclear medicine. This work is based on our published results and the thematically similar papers by other authors, directly related to five medical radioisotopes as <sup>99</sup>Mo/<sup>99m</sup>Tc, <sup>198</sup>Au, <sup>186</sup>Re, <sup>188</sup>Re, <sup>117m</sup>Sn, produced using therapeutic linacs. Our unpublished data relating to the issues discussed have also been used here. In the experiments, two types of radiation were included in the analysis of the radioisotope production process, i.e. the therapeutic twenty-megavolt (20 MV) X-rays generated by Varian linacs and neutron radiation contaminating the therapeutic beam. Thus, the debated radioisotopes are produced in the photonuclear reactions and in the neutron ones. Linear therapeutic accelerators do not allow the production of radioisotopes with high specific activities, but the massive targets can be used instead. Thus, the amount of the produced radioisotopes may be increased. Apart from linear accelerators, more and more often, the production of radioisotopes is carried out in small medical cyclotrons. More such cyclotrons are developed, built, and sold commercially than for scientific research. The radioisotopes produced with the use of therapeutic linacs or cyclotrons can be successfully applied in various laboratory tests and in research.</p> </abstract>ARTICLEtrue tissue objective (NTO) tool in Eclipse treatment planning system for dose distribution optimization<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> The purpose of this study was to determine the best normal tissue objective (NTO) values based on the dose distribution from brain tumor radiation therapy.</p> <p><italic>Material and methods:</italic> The NTO is a constraint provided by Eclipse to limit the dose to normal tissues by steepening the dose gradient. The multitude of NTO setting combinations necessitates optimal NTO settings. The Eclipse supports manual and automatic NTOs. Fifteen patients were re-planned using NTO priorities of 1, 50, 100, 150, 200, and 500 in combination with dose fall-offs of 0.05, 0.1, 0.2, 0.3, 0.5, 1 and 5 mm<sup>-1</sup>. NTO distance to planning target volume (PTV), start dose, and end dose were 1 mm, 105%, and 60%, respectively, for all plans. In addition, planning without the NTO was arranged to find out its effect on planning. The prescription dose covered 95% of the PTV. Planning was evaluated using several indices: conformity index (CI), homogeneity index (HI), gradient index (GI), modified gradient index (mGI), comprehensive quality index (CQI), and monitor unit (MU). Differences among automatic NTO, manual NTO, and without NTO were evaluated using the Wilcoxon signed-rank test.</p> <p><italic>Results:</italic> Comparisons obtained without and with manual NTO were: CI of 0.77 vs. 0.96 (p = 0.002), GI of 4.52 vs. 4.69 (p = 0.233), mGI of 4.93 vs. 3.95 (p = 0.001), HI of 1.10 vs. 1.10 (p = 0.330), and MU/cGy of 3.44 vs. 3.42 (p = 0.460). Planning without NTO produced a poor conformity index. Comparisons of automatic and manual NTOs were: CI of 0.92 vs. 0.96 (p = 0.035), GI of 5.25 vs. 4.69 (p = 0.253), mGI of 4.46 vs. 3.95 (p = 0.001), HI of 1.09 vs. 1.10 (p = 0.004), MU/cGy of 3.31 vs. 3.42 (p = 0.041).</p> <p><italic>Conclusions:</italic> Based on these results, manual NTO with a priority of 100 and dose fall-off 0.5 mm<sup>-1</sup> was optimal, as indicated by the high dose reduction in normal tissue.</p> </abstract>ARTICLEtrue diagnostic reference levels and effective doses: single institution levels for interventional cardiology procedures for adult patients<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> The current regulations in Poland in the field of interventional radiology only include diagnostic reference levels (DRL) for five procedures, containing only two for cardiological (hemodynamic) procedures, and only for adults. Given the insufficient number of DRLs, the need to introduce local levels based on the intervention procedures performed was identified. The purpose of this research was the evaluation of radiation doses (DRL, effective dose) received by patients in cardiological interventional procedures.</p> <p><italic>Material and methods:</italic> The DRL level was defined as the 75th percentile of the distribution of dosimetric parameters KAP and K<sub>air,ref</sub> for each type of cardiological procedure. Data include three different X-ray units and 27 interventional cardiologists, derived from February 2019 to June 2019 and from August 2021 to December 2021. In order to estimate the effective dose, the appropriate conversion factors for cardiological procedures were used. The total number of analyzed procedures was 3818.</p> <p><italic>Results:</italic> The proposed local DRL levels were found to be mostly lower than data found in literature and in the current Polish national requirements (60%-70% lower for coronary angiography (CA) and percutaneous coronary angioplasty (PCI) procedures). Median equivalent doses for cardiological procedures were estimated at 2.66 mSv, 6.11 mSv and 7.22 mSv for CA, PCI and combined PCI with CA procedure, respectively.</p> <p><italic>Conclusions:</italic> The proposed local/institutional DRLs seem to be suitable for use and could be utilized by other centers for comparison purposes.</p> </abstract>ARTICLEtrue of SRS MapCHECK with StereoPHAN phantom as a new pre-treatment system verification for SBRT plans<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> The aim of this study was to evaluate the new 2-Dimensional diode array SRS MapCHECK (SunNuclear, Melbourne, USA) with dedicated phantom StereoPHAN (SunNuclear, Melbourne, USA) for the pre-treatment verification of the stereotactic body radiotherapy (SBRT).</p> <p><italic>Material and methods:</italic> For the system, the short and mid-long stability, dose linearity with MU, angular dependence, and field size dependence (ratio of relative output factor) were measured. The results of verification for 15 pre-treatment cancer patients (5 brains, 5 lungs, and 5 livers) performed with SRS MapCHECK and EBT3 Gafchromic films were compared. All the SBRT plans were optimized with the Eclipse (v. 15.6, Varian, Palo Alto, USA) treatment planning system (TPS) using the Acuros XB (Varian, Palo Alto, USA) dose calculation algorithm and were delivered to the Varian EDGE® (Varian, Palo Alto, USA) accelerator equipped with a high-definition multileaf collimator. The 6MV flattening-filter-free beam (FFF) was used.</p> <p><italic>Results:</italic> Short and mid-long stability of SRS MapCHECK was very good (0.1%-0.2%), dose linearity with MU and dependence of the response of the detector on field size results were also acceptable (for dose linearity R<sup>2</sup> = 1 and 6% difference between microDiamond and SRS MapCHECK response for the smallest field of 1 × 1 cm<sup>2</sup>). The angular dependence was very good except for the angles close to 90° and 270°. For pre-treatment plan verification, the gamma method was used with the criteria of 3% dose difference and 3 mm distance to agreement (3%/3 mm), and 2%/2 mm, 1%/1 mm, 3%/1 mm, and 2%/1 mm. The highest passing rate for all criteria was observed on the SRS MapCHECK system.</p> <p><italic>Conclusions:</italic> It is concluded that SRS MapCHECK with StereoPHAN has sufficient potential for pre-treatment verification of the SBRT plans, so that verification of stereotactic plans can be significantly accelerated.</p> </abstract>ARTICLEtrue of the Sievert integral for the calculation of dose distribution around the BEBIG Co-60 high dose rate brachytherapy source<abstract> <title style='display:none'>Abstract</title> <p><italic>Introduction:</italic> In radiotherapy, a computerized treatment planning system (TPS) is used for performing treatment planning to estimate the dose distribution within a patient. To simplify the dose calculation, mathematical algorithms are employed. TG43 formalism is widely used for brachytherapy. Before the implementation of a particular dose calculation algorithm in clinical practice, it is imperative to acknowledge the limitations and uncertainties associated with the algorithm. Regarding this, outputs of the algorithm are compared to measurements or dose calculation approaches using simple source placement geometries. The manual dose calculation method has to be robust, straightforward, and devoid of complexities to reduce the likelihood of committing errors in the dose calculation process. A lot of manual dose calculation approaches have been proposed for Brachytherapy sources, but one needs to ascertain their reliability.</p> <p><italic>Material and methods:</italic> Considering this, the output of an HDRplus treatment planning system dedicated to brachytherapy treatment planning and using the TG43 formalism to calculate the dose distribution around a BEBIG Co-60 source was validated with Sievert integral dose calculation approach. Simple source placement geometries were created with the TPS using the universal applicator, LLA1200-20, selected from the applicator library, and doses at various equidistant points from the applicator calculated with the TPS and the Sievert integral. Various steps to enhance the efficacy of the Sievert integral approach have been outlined.</p> <p><italic>Results:</italic> The doses compared favourably well with deviations ranging from 0.03 – 10.51% (mean of 3.13%), and 0.03 – 5.63% (mean of 2.55%) for angles along the perpendicular bisector of the source, ranging from 0° &lt; θ &lt; 70° and 0° &lt; θ &lt; 48°, respectively.</p> <p><italic>Conclusions:</italic> The Sievert integral breaks down at angles: θ ≥ 60°, and therefore, neglecting large angles, the Sievert integral would be an efficient, effective, and valid tool for quality control of the HDRplus TPS for the Co-60 source.</p> </abstract>ARTICLEtrue