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Purpose: Results of the low-dose radiation therapy (LDRT) in patients with pneumonia due to COVID-19 has been presented. Methods: Fifteen patients received a single-fraction radiation dose of 1 Gy to the bilateral lungs due to pre-ARDS pneumonia in the course of COVID-19. Follow-up was performed on days 1, 3, 5, 7, 14 after LDRT. Results: Eleven patients (73%) were released up until day 28. Median hospitalization was 20 days; 28-day mortality was 13%. Median O2 saturation improved within 24 h after LDRT in 14/15, with median SpO2 values of 84.5% vs. 87.5% p = 0.016, respectively. At day 14 of hospitalization, 46% did not require oxygen supplementation. Significant decline in CRP and IL-6 was observed within 24 h post LDRT. No organ toxicities were noted. Conclusion: LDRT is feasible, well tolerated and may translate to early clinical recovery in patients with severe pneumonia. Further studies are needed to determine optimal candidate, time and dose of LDRT for COVID-19 patients with pneumonia. [ABSTRACT FROM AUTHOR]

Introduction. COVID radiotherapy requires performance of all radiotherapy (RT) procedures during one site visit due to the infectious nature of the disease. The aim of the study was to develop methods of estimating the delivered dose based on electronic portal image device (EPID) signal during treatment. Material and methods. Electronic portal image device signal was measured as a function of the phantom dose. The dose in 14 COVID patients was estimated for two X6MV beams. Results. The method allows to estimate dose in phantom with uncertainty of 12%. In this case, a systematic error was reported. Therefore, coefficients for clinical data were calculated and used to determine the dose in patients. The mean difference between the dose calculated and the dose measured for the 14 patients was 1%, but the uncertainty of this method was estimated as ±6% Conclusions. The proposed method may be useful in clinical practice as in vivo method. However, due to high uncer- tainty, it should be dedicated to the detection of “big” errors. [ABSTRACT FROM AUTHOR]

Introduction. The paper presents an original, used in our Institute, method of lung volume irradiation in patients with pneumonia during COVID-19 infection. Material and methods. Procedures such as the simulation of treatment and radiotherapy are performed in a treatment room. Real time radiation treatment planning is realized as 2D planning (Irreg Planning VMS) in a separate room, and the 3D (eclipse VMS) dose distribution is calculated after the treatment. During radiation exposure, a fluence map is measured. Results. A method of irradiating the lungs of patients with COVID-19 was developed, which allows to shorten the time the patient is on the treatment table and minimize contacts between the patient and staff. Conclusions. The presented procedure made it possible to minimize the time of patient’s stay in the radiotherapy department and at the same time, it retains all the required quality assurance procedures in radiotherapy treatment. [ABSTRACT FROM AUTHOR]

Introduction. Medical physicists planning radiation treatment are increasingly confronted with situations that require special attention. Undoubtedly, one such situation is the postoperative irradiation of a patient with breast cancer in which there is a prosthesis or an expander. In recent years, expanders have appeared in this location, which, due to the density of the device’s valve makes it difficult to prepare an acceptable treatment plan. The study aims to present treatment planning in these situation in various Polish cancer centres and to compare overall patient preparation for the treatment. Material and methods. A questionnaire was prepared and sent to more than 20 radiotherapy departments, which included basic questions regarding the preparation of an irradiation plan for patients treated for breast cancer after a subcutaneous mastectomy with immediate reconstruction with a prosthesis or expander. The survey encompassed eight radiotherapy departments. Results. Not all radiotherapy departments require a manufacturer’s certificate, which shows that the manufacturer does not prohibit the use of a prosthesis/expander during treatment with ionizing radiation. The X 6MV photons and the supine position, total and fraction doses: from 40 to 60 Gy and from 2 to 2.67 Gy, respectively, are the most commonly used. The way of defining them also depends on the oncological centre. The most commonly used irradiation technique is VMAT. Conclusion. The conclusion from the questionnaire – no standardisation of treatment planning – should encourage the community, at least medical physicists, to develop rules of conduct in this case. Irradiation techniques are mainly dynamic ones. The expander or prosthesis does not significantly affect the dose distributions. [ABSTRACT FROM AUTHOR]

The accuracy of radiotherapy is the subject of continuous discussion, and dosimetry methods, particularly in dynamic techniques, are being developed. At the same time, many oncology centers develop quality procedures, including pretreatment and online dose verification and proper patient tracking methods. This work aims to present the possibility of using portal dosimetry in the assessment of radiotherapy repeatability. The analysis was conducted on 74 cases treated with dynamic techniques. Transit dosimetry was made for each collision‐free radiation beam. It allowed the comparison of summary fluence maps, obtained for fractions with the corresponding summary maps from all other treatment fractions. For evaluation of the compatibility in the fluence map pairs (6798), the gamma coefficient was calculated. The results were considered in four groups, depending on the used radiotherapy technique: stereotactic fractionated radiotherapy, breath‐hold, free‐breathing, and conventionally fractionated other cases. The chi2 or Fisher's exact test was made depending on the size of the analyzed set and also Mann–Whitney U‐test was used to compare treatment repeatability of different techniques. The aim was to test whether the null hypothesis of error‐free therapy was met. The patient is treated repeatedly if the P‐value in all the fluence maps sets is higher than the level of 0.01. The best compatibility between treatment fractions was obtained for the stereotactic technique. The technique with breath‐holding gave the lowest percentage of compliance of the analyzed fluence pairs. The results indicate that the repeatability of the treatment is associated with the radiotherapy technique. Treated volume location is also an essential factor found in the evaluation of treatment accuracy. The EPID device is a useful tool in assessing the repeatability of radiotherapy. The proposed method of fluence maps comparison also allows us to assess in which therapeutic session the patient was treated differently from the other fractions. [ABSTRACT FROM AUTHOR]

The response of normal tissues/organs to SHRS is more complex than to conventional radiotherapy. Tolerance doses TD5/5 and TD50/5, proposed by Rubin and Casarett, cannot be simply used for SHRS. Instead of LQED2, the BED is advised. The term risk dose (RD) corresponds better than TD to the risk of late morphological and functional disorders (OAR). BED doses show a rapid gradient with increasing distance of the OAR from the tumour GTV. Other risk factors include the dose-volume relationship, OAR organization (serial or parallel) and the ratio of the FSU to the target call. Vasculoendothelial cell damage initiates series of processes resulting in clinical and functional late effect. Using available data and studies, RDmin and RDmax for doses are listed as physical and BED doses for various OAR and dose- -volume constraints. The RD values and constraints are rough estimates, since the available SHRS data are sparse and fragmentary, which should be interpreted cautiously and need further clinical validation. [ABSTRACT FROM AUTHOR]

In conventional radiotherapy, 5R's mechanisms influence tumour cell kill, but in SHRS they do not sufficiently explain the biology of large doses. Indirect cell death is also induced by endothelial damage, stem cell death and antitumour immunity are also activated by a single dose ≥ 12-15 Gy. These three processes defined as extra 3R's are characterizers in details. Despite some controversies, LQED formalism seems not quite adequate for SHRS. Experimental and a few clinical studies suggest BED formalism as much more useful. Both formalisms are compared and discussed. Clinical reports show a monotonical increase in Tumour Cure Probability (TCP) with higher BED doses. The advantage of SHRS results in significant shortening overall treatment time and in delivery of the BED doses higher than 100 Gy, producing an increase in the TCP, likely unachievable by conventional dose fractionation. [ABSTRACT FROM AUTHOR]

Recent technological development in radiotherapy allows to introduce new irradiation techniques implemented on the conventional accelerators and on the machines such as CyberKnife (CK). These significantly changes the philosophy of planning and execution of radiotherapy. One of the fundamental concepts in radiotherapy is to define the therapeutic dose. It can be defined in the point, at the selected isodose, as an average value, or combined with the volume. We present the case of prostate cancer patient irradiated using CK machine and classic accelerator (VMAT). The differences in dose distribution and its value are shown. The analysis indicates that the average dose in Planning Treatment Volume (PTV) is a useful parameter during comparison of the dose distributions realized on machines of different type. [ABSTRACT FROM AUTHOR]

Abstract: Aim: To examine the impact of beam rate on dose distribution in IMRT plans and then to evaluate agreement of calculated and measured dose distributions for various beam rate values. Background: Accelerators used in radiotherapy utilize some beam rate modes which can shorten irradiation time and thus reduce ability of patient movement during a treatment session. This aspect should be considered in high conformal dynamic techniques. Materials and methods: Dose calculation was done for two different beam rates (100MU/min and 600MU/min) in an IMRT plan. For both, a comparison of Radiation Planning Index (RPI) and MU was conducted. Secondly, the comparison of optimal fluence maps and corresponding actual fluence maps was done. Next, actual fluence maps were measured and compared with the calculated ones. Gamma index was used for that assessment. Additionally, positions of each leaf of the MLC were controlled by home made software. Results: Dose distribution obtained for lower beam rates was slightly better than for higher beam rates in terms of target coverage and risk structure protection. Lower numbers of MUs were achieved in 100MU/min plans than in 600MU/min plans. Actual fluence maps converted from optimal ones demonstrated more similarity in 100MU/min plans. Better conformity of the measured maps to the calculated ones was obtained when a lower beam rate was applied. However, these differences were small. No correlation was found between quality of fluence map conversion and leaf motion accuracy. Conclusion: Execution of dynamic techniques is dependent on beam rate. However, these differences are minor. Analysis shows a slight superiority of a lower beam rate. It does not significantly affect treatment accuracy. [Copyright &y& Elsevier]

Abstract: Background: During a proper execution of dMLC plans, there occurs an undesired but frequent effect of the dose locally accumulated by tissue being significantly different than expected. The conventional dosimetric QA procedures give only a partial picture of the quality of IMRT treatment, because their solely quantitative outcomes usually correspond more to the total area of the detector than the actually irradiated volume. Aim: The aim of this investigation was to develop a procedure of dynamic plans verification which would be able to visualize the potential anomalies of dose distribution and specify which tissue they exactly refer to. Materials & methods: The paper presents a method discovered and clinically examined in our department. It is based on a Gamma Evaluation concept and allows accurate localization of deviations between predicted and acquired dose distributions, which were registered by portal as well as film dosimetry. All the calculations were performed on the self-made software GammaEval, the γ-images (2-dimensional distribution of γ-values) and γ-histograms were created as quantitative outcomes of verification. Results: Over 150 maps of dose distribution have been analyzed and the cross-examination of the gamma images with DRRs was performed. Conclusions: It seems, that the complex monitoring of treatment would be possible owing to the images obtained as a cross-examination of γ-images and corresponding DRRs. [Copyright &y& Elsevier]

The aim of the study was to evaluate the temperature parameter of the breast area in patients undergoing radiotherapy at various intervals. The relationship between temperature changes on the patient's skin and the time after the end of radiotherapy was studied. Measurements with a thermal imaging camera were performed in a group of twelve volunteers. Six of them were healthy women who did not have thermal asymmetry between the breasts, whereas six were diagnosed with breast cancer and underwent mastectomy due to the advanced stage of the disease. The patients were qualified for radiation therapy. Thermographic examinations were performed before treatment, two months later and then six months after the end of the treatment. Temperature differences between the healthy breasts and the treated areas were assessed. Additionally, the correlation between a patient's skin temperature changes and the time after the end of radiotherapy was analyzed. The highest skin temperature increase (1.47 °C) was observed 6 months after the end of RT compared to the measurement before treatment. It seems that thermovision may bring a new tool for quantitative analyses of the temperature effects of radiotherapy. [ABSTRACT FROM AUTHOR]

Abstract: Purpose: Delineation of target volume could be performed on all respiratory phases and radiation is delivered during free breathing cycle, or on the basis of one respiratory phase and deliver gated treatment choosing a specific phase for irradiation. We performed the comparison of both techniques in terms of target and normal tissue dose distributions. Materials and methods: We analysed 26 metastatic liver tumours using 4DCT to characterize tumour motion and to create treatment volumes: GITV4D was based on all 8 respiratory phases and GTVGAT was based on one specific phase. A 5mm automatic expansion was added to the GTVs to create PTVs. Two treatment plans were prepared to the total dose of 36Gy in 3 fractions and dose–volume distributions were analysed for the target and organs at risk. Target motion along the superior–inferior direction was greatest with the mean of 1.1cm±0.3, and in the lateral the mean was 0.7cm±0.3. Results: GTV and PTV volumes were larger in the 4D than in the GAT, mean 30.7 vs. 19.3cm3, and 66.7 vs. 45.1cm3. We achieved similar dose coverage in PTV4D, for the 4D plan, and PTVGAT for the GAT plan, but a decrease in the average minimum dose to 17.8Gy and the average mean dose to 35.3Gy was found in PTV4D in the GAT plan. Radiotherapy delivered using GAT resulted in lower liver doses than using 4D with reduction of mean volume receiving 5Gy by 6.5%±5, V 15Gy by 4.5%±3.4, V 21Gy by 3.4%±2.8 and reduction of mean kidney volume receiving 5Gy by 9.1%±7.9, V 15Gy by 4.1%±6.4, V 21Gy by 3.2%±5.6. We also found correlations between PTV volume reduction with GAT, GTV motion and doses to normal tissues. Conclusions: Gated radiotherapy could potentially allow a reduction in PTV volumes from those delineated on all respiratory phases, maintaining acceptable target coverage. Smaller target volumes improve doses distribution in normal tissue especially in the liver and kidney, but also spinal cord and intestine. A significant correlation has been found between dose and volume reduction in the OARs and both GTV motion and PTV volume reduction. [Copyright &y& Elsevier]