Volume 27 (2021): Issue 2 (June 2021)

Spatially fractionated radiation therapy (SFRT) refers to the delivery of a single large dose of radiation within the target volume in a heterogeneous pattern using either a custom GRID block, multileaf collimators, and virtual methods such as helical tomotherapy or synchrotron-based microbeams. The potential impact of this technique on the regression of bulky deep-seated tumors that do not respond well to conventional radiotherapy has been remarkable. To date, a large number of patients have been treated using the SFRT techniques. However, there are yet many technical and medical challenges that have limited their routine use to a handful of clinics, most commonly for palliative intent. There is also a poor understanding of the biological mechanisms underlying the clinical efficacy of this approach. In this article, the methods of SFRT delivery together with its potential biological mechanisms are presented. Furthermore, technical challenges and clinical achievements along with the radiobiological models used to evaluate the efficacy and safety of SFRT are highlighted.

Introduction: The aim of the study was to evaluate the influence of flattening filter (FF) and flattening filter-free (FFF) beams on small-field and large-field dose distribution using the VMAT treatment plan.

Material and methods: Dose distribution calculations were performed for the VMAT technique in two locations: the larynx (small irradiation field; average 30.1 cm²) and gynecology (large irradiation field; average 173.1 cm²) using X-6MV flattening filter (FF) and flattening filter-free (FFF) beams. The following values were compared: the number of monitor units, minimum doses, average doses in PTV and maximum average doses in OaR (spinal cord – in larynx radiotherapy, bladder and rectum - in gynecological radiotherapy) and RPI (Radiation Planning Index) coefficient.

Results and Discussion: The performed statistical tests indicate that there is a significant difference (p <0.05) between the number of monitor units in the irradiation of large (gynecological) fields between the FF and FFF beams. The dose distributions show no statistically significant differences between the flattening filter and flattening-free filter beams (regardless of the field size).

Conclusions: Due to the smaller number of monitor units, it is recommended to use flattening filter beams (FF) for large-field radiotherapy.

Purpose: The aim of this study is to compare the dosimetric results of Helical Tomotherapy (HT) and Multi-field IMRT treatment plans using a Simultaneous Integrated Boost (SIB) technique in the treatment of High-Risk Prostate Cancer (HRPCa) with pelvic nodal radiation.

Methods: Seventeen patients planned with HT and 7,8 and 9 fields IMRT were investigated. All plans were designed with the prescribed dose of 54.0 Gy to the PTVln while simultaneously delivering 74.0 Gy to the PTVPS in 30 fractions. Dosimetric data of PTV and OARs were compared.

Results: HT gives a better CI and HI of PTV_PS compared to multi-field IMRT plans. HT plans significantly improved target coverage (HT:0.95 vs multi-field IMRT: 0.52, 0.49 and 0.49 respectively, p < 0.001). Bladder mean dose(Gy) (HT: 45.6 vs multi-field IMRT: 53.6, 53.3 and 52.7 respectively, p = 0.004) and D_66%(Gy) dose (HT: 35.3 vs multi-field IMRT: 46.7, 47.0 and 44.9 respectively, p = 0.006) were lower in HT. But multi-field IMRT plans significantly reduced the rectum volume receiving more than 75 Gy; (HT V_75% (%) 2.7 vs multi-field IMRT 0.8, 1.4 and 0.9 respectively, p = 0.008). HT provided better sparing of the right and left femoral head receiving a mean dose. The penile bulb and small bowel doses were the highest in HT compared with multi-field IMRT.

Conclusions: HT achieved better dose distribution to target compared to multi-field IMRT. This study suggests HT as a reasonable option for the treatment of HRPCa patients.

External photon beam radiotherapy is often used in tumor treatment. The photons are generated from the target which had stricken by the primary electron beam (incident particles). The photon beam contains the primary photons coming directly from the target and secondary photons coming from the photon interactions with head component materials (scattered photons). Altogether is thereafter used in radiotherapy treatment. This Monte Carlo study aims to investigate and evaluate the secondary radiations (photons) in terms of fluence, energy fluence, spectral distribution, mean energy and angular spread distribution.

The secondary photons, which contributed in radiotherapy treatment, are examined and evaluated in number (fluence) and energy. At the phantom surface, the secondary photons originated in the whole linac head are mainly coming from the primary collimator. In 0.45% of secondary photons coming from the whole linac head, the primary collimator contributes by 86% and they are more energetic. However, the flattening filter and the secondary collimator contribute together by less than 14% and their photons are less energetic and then can deteriorate the beam dosimetry quality. To improve the radiotherapy treatment quality, the number of photons of low energy should be as low as possible in the clinical beam. Our work can be a basic investigation to use in the improvement of linac head configuration and specially the beam modifiers.

Sedentary lifestyle and physiological menopause are among the risk factors of osteopenia, especially in elderly people. However, bone mineral density decrease can also be observed in young individuals, for instance, due to deficiency of female sex hormones after surgical interventions, particularly ovariectomy. Our research enabled us to assess the efficacy of whole-body vibration in preventing the loss of bone mineral density in the ovariectomy rat osteopenia model. Thus, whole-body vibration with acceleration level 0.3 g and frequency 50 Hz was used on young female rats, which had been subjected to ovariectomy (n = 18). It had been conducted for 24 weeks, exposure time – 30 minutes per day, 5 times a week. Assessment of mineral component loss of the tibia was performed by means of X-ray diffraction. Bone remodeling was assessed by determining hormones: parathyroid hormone and calcitonin, Ca and P in the blood. X-ray diffraction is an effective method, which enables the evaluation a nanocomposites structure of the bone tissue in the experiment. In the article, we applied this method to determine the loss of bone mineral mass after ovariectomy and the impact of whole-body vibration under such conditions. In the ovariectomy group, the volume of a mineral component significantly decreased starting already from the 16th week (р<0.05) versus control. However, in the group with ovariectomy + whole-body vibration, the loss of a mineral component was insignificant during 8-16 weeks of the investigation, compared with the control group. On the 24th day, the spectrums almost did not differ from ovariectomized rats group. Meanwhile, hormone levels changed in ovariectomized rats group. It should be emphasized that the aforementioned whole-body vibration parameters do not cause severe bone damage or further negative consequences.

Introduction: The purpose of the study was the calibration of Gafchromic films in clinical interventional radiology conditions and the assessment of the influence of dose range, the shape of the fitting curve, and its practical application. The aim of the work was to show how practically perform calibration in a wide range of doses.

Material and methods: Gafchromic XR–RV3 films were included in the study. The calibration was performed for A and B film series separately. Doses from the range of 0 – 8 Gy were used. Film dosimeters were read out in reflective mode with a commercial flatbed scanner.

Results: Among various degrees of a polynomial function, the best fit, which fulfilled the chosen criterion of 95% agreement between measured and reconstructed doses and simple equation criterion, was observed for third-degree polynomial. The fitting curve where the dose is the function of optical density (logMPV) was demonstrated to be more precise than the fitting curve based on MPV only. To minimize the difference between dose absorbed by the film and dose reconstructed from the fitting curve below 5% it is necessary to divide the calibration range of 0 – 8 Gy into two subranges for use in interventional radiology. This difference was set at a maximum level of 3.8% and 1.9% for the lowand high-dose range, respectively. Each series of films may have a slightly different calibration curve, especially for the low dose range. A deviation of up to 36% between two batches of Gafchromic film was observed.

Conclusions: For the third-degree polynomial fitting function (one of the recommended in the literature) calibration should be done into low and high dose ranges and for each batch separately. A systematic error higher than 20% could be introduced when the fitting curve from one film batch is applied to the other film batch.

The analysis involved thermograms of the lower limbs of a patient suffering from symptomatic L-S segment discopathy with spinal root compression syndrome (symptomatic lumbar discopathy) qualified for surgical treatment. The thermograms were obtained using the Flir Ebx 50 camera. They were developed with the use of the software included with the Flir Ebx 50 camera, as well as the Origin Pro 2020 data analysis and graphing software. ROIs (Regions of Interest) were specified and analyzed in terms of temperature (average, maximum or minimum) temperature distributions, isotherms, and specified surface areas limited by selected isotherms. According to the analysis of the thermograms, the images obtained with Origin Pro 2020 enable a more advanced presentation of the temperature distribution, by taking into account the isotherms with selected temperatures and by calculating the area limited by a given isotherm (or between two isotherms) they allow to introduce an additional surface parameter related to specific isotherms. It provides additional information (parameter) in comparison with analogous ROIs on healthy and pathologic limbs in the same patient.