Basic radiotherapy physics and biology

Estimation and evaluation of Students’ behaviors in E- learning Environment using adaptive computing

Purpose: The advent of the COVID-19 pandemic brought various and radical changes at the worldwide level. Globally, severe preventive measures were imposed to respond to the crisis such as lockdowns which forced the people to quarantine themselves inside their houses for longer periods. This issue stressed the crucial role of healthy houses in providing the various needs of residents during crises. Design/methodology/approach: This study methodology adopted both inductive approach and a Study Application Model to define the Healthy House Criteria and fulfill the study objectives. Under the inductive approach a holistic literature review was undertaken while the Study Application Model implied defining the conception of the overall Criteria of the Healthy House's interior design under the COVID-19. Findings: The finding of the study showed some areas needed to improve current healthy house's criteria in terms of its interior design that may be used to cope with potential crises such as the COVID-19. Based on the revealed findings, the researcher suggested a conceptual framework for healthy house's criteria and further research areas. Originality/value: The current research may provide applicable framework for both interior designers and households in terms of how to design and implement a healthy house, which is valid to accommodate residents during potential crises such as the COVID-19. © 2021, Emerald Publishing Limited.

Reconsidering the criteria of the healthy house's interior design during crises: COVID-19 pandemic as an example

Purpose To investigate the accuracy of field junctioning planning techniques (monoisocentric and rotating couch technique) for 3D-conformal radiotherapy (3D-CRT). Methods In vivo dosimetry has been performed using thermo- luminescence dosimeters (TLDs) in 10 head and neck cancer patients (treated with monoisocentric technique) and 10 breast cancer patients (treated with rotating couch technique) irradiated with a 6 MV photon beam. Entrance dose measurements were performed in selected regions including the field junction area. Results The mean deviation between measured and expected dose in the region of junction was significantly higher in breast cases compared to head and neck irradiation (-2.8±15.4% and 0.2±8.2% respectively; Mann-Whitney U test: p=0.002). A comparison between lateral head and neck fields and tangential breast fields revealed that the latter was associated with larger dose discrepancies (-2.2 ± 4.6% vs -3.5 ± 5.7% respectively; Mann-Whitney U test: p=0.029). Conclusions The results indicate the superiority of monoisocentric technique compared to the rotating couch technique in terms of dose delivery accuracy for treatments with field junctioning planning techniques.

In vivo dosimetry in the field junction area for 3D-conformal radiation therapy in breast and head & neck cancer cases: A quality assurance study

Introduction: This study aimed to report the measurement of photon and electron beams to configure the Analytical Anisotropic Algorithm and Electron Monte Carlo used in clinical treatment. Material and Methods: All measurements were performed in a large water phantom using a 3-dimensional scanning system (PTW, Germany). For photon beams, the data were measured with a 0.125cc cylindrical chamber. For electron, the data were performed with a Roos chamber. Results: In photon beams, flatness and symmetry for reference field size 10×10cm2 were within the tolerance intervals. Flatness were 0.79% and 1.55% for X6MV and X18MV, respectively. Symmetry were 0.57 and 0.25 for X6MV and X18MV, respectively. The output factor vary between 0.83 and 1.11 for X6MV. Moreover, it varies between 0.74 and 1.09 for X18MV. The leaf transmission factors were 0.97% for X6MV and1.14% for X18MV. The DLG were 1.31 and 1.34 for X6MV and X18MV, respectively. For electron beams, the quality index R50 for applicator 15×15cm2 were in the tolerance. Maximum depth dose for 6, 9, 12, 16 and 20MeV were 1.2, 1.9, 2.7, 2.99 and 2.4cm, respectively. Bremsstrahlung tail were 6MeV–2.86cm, 9MeV–4.32cm, 12MeV–5.96cm, 16MeV–7.93cm, and 20MeV–10.08cm per energy levels. Conclusion: The obtained results and international recommendations were in a good agrement

http://ijmp.mums.ac.ir/article_11715_97606f715bb6b54b7c853065c872cd67.pdf

Measurements of Photon Beam Flattening Filter Using an Anisotropic Analytical Algorithm and Electron Beam Employing Electron Monte Carlo

The goal of this research was to study the widely used criteria in Iraq and the suggested criteria from the American association of physics in medicine (AAPM). The breast cancer patients treated at Al-Andalus private hospital underwent a CT simulation. The data were exported to Monaco 5.1 treatment planning system for planning purposes using the intensity-modulated radiation therapy technique with X-ray energies of 6 or 10 MV. The planning was transferred to Agility linear accelerator for irradiation to Octavius-4D phantom detector for pre-treatment verification. The results show that there is no significant difference between the prescribed and measured point dose. In addition, the dose difference is acceptable and there was no significant correlation between the dose error and the result of gamma passing rates for all criteria. A high significant difference appeared between the 3%/2 mm and 3%/3 mm criteria for both local and global gamma passing rates at the two studied thresholds 5% and 10%. All the values of 10% thresholds were highly significant than 5% in local %GP but not significant for the global %GP. The number of segments and the total number of monitor units show an inverse relationship with gamma passing rates. The results clearly show that criteria and thresholds depend on the situation and health of the patient. This means the criteria are to be set at 3%/2 mm for plans which use high doses to organs at risk, while 3%/3 mm may be used for simpler plans with lower doses to organs at risk.

Dosimetric assessment of IMRT treatment planning for unilateral breast cancer patient using Octavius phantom detector

Introduction: According to the American Society of Radiation Oncology, all patients receive radiation therapy during their illness, where radiation is delivered by the medical linear accelerator (Linac). The aim of this study was to evaluate the quality assurance (QA) of the Linac in analyzing the used dose profile in the treatment of cancer tumors. Material and Methods: This experimental study was performed using Linac (synergy device type) at Baghdad Radiotherapy and Nuclear Medicine laboratories, Baghdad, Iraq. The Star Track device was used for the routine quality assurance of the Linac, using photon beam for the reference Dmax and source to surface distance of 100 cm. The Star Track consists of 453 vented parallel plate ionization chambers. Results: The flatness and symmetry of beams for the reference field size did not exceed from ±2%, as they were within the allowed range. Moreover, the penumbra region showed a change in value that did not exceed from ±0.2 cm. using the Star Track method; maximum differences in beam symmetry and beam flatness were measured at 0.76%±2% and 1.17%±2%, respectively. Moreover, the maximum difference in the penumbra region was estimated at 0.12±0.2 cm. Conclusion: The results indicated, the Star Track could successfully calculate the characteristics of dose profile during a time period of 2,500 ms, showing the superiority of this instrument over other verification devices.

http://ijmp.mums.ac.ir/article_13460_040a4e03762f70aa4632e2017fe44867.pdf

Quality Assurance of LINAC by Analyzing the Profile of 6-MV and 10-MV Photon Beams Using Star Track Device

Electron beam therapy using linear accelerator done for patients with superficial cancerous tumors. Daily quality assurance is preferable to assess a good treatment for the patients. This study focuses on penumbra, flatness, and symmetry determination for four types of an electron beam using StarTrack 2D array for quality assurance. Eelectron beam with energies: 6MeV, 9MeV, 12 MeV, and 15MeV for both in-plane (x-axis) and cross-plane (y-axis) using Elekta synergy linac exposed to StarTrack 2D array readings during 16 weeks for testing the performance and stability of StarTrack. The testing protocol used is IEC.The beam profile estimation of variation, when compared with standard values of penumbra, flatness, and symmetry of electron beam energy at the time of commissioning, reveals that all had a variation but these variations are within the limits. It is concluded that StarTrack 2D array detector is favourable in the QA process. Their implementation is not only easy, but gives information about the beam’s temporal stability and is particularly suitable for beam steering mounting.

Electron Beam Profile Assessment of Linear Accelerator Using Startrack Quality Assurance Device

Intensity modulated radiation therapy (IMRT) is an effective treatment planning technique for various types of tumors such as head and neck (H&N) or pelvis. A complexity algorithm was invented to predict the deliverability and the accuracy for IMRT plans called the Modulation Complexity Score ranging from 0 to 1. The %GP is a metric depends on %DD /DTA to find the variation between the calculated dose from TPS and the measured dose from the phantom during the QA. This study is trying to assess the correlation between the MCS and planning verification outcome. Thirty-four patients treated with step and shoot IMRT technique for anatomical sites: H&N and pelvis. The planning process performed using Monaco 5.1 TPS then exported to Elekta Synergy linear accelerator. The phantom is used for the QA procedure is Octavius 4D-1500 with Verisoft 7.1 software analysis to evaluate the gamma passing rate for commonly used criteria 3%/3 mm at a 5% threshold. The MCS calculated using MATLAB 2019a. It results that the H&N plans are significantly more complex than the pelvis once with p-value 0.0192. The analysis shows a weak correlation between the MCS and MU for both treated sites. The complex H&N plans give a good value for %GP. Also, simpler pelvis plans obtain better global %GP results. Thus, modulation Complexity score can give a simple indication for pretreatment verifications of the IMRT plans for H&N and pelvis sites.

https://iopscience.iop.org/article/10.1088/1742-6596/1829/1/012017/pdf

The Effect of Modulation Complexity Score (MCS) on the IMRT Treatment Planning Delivery Accuracy

Objective : Most contemporary treatment planning systems (TPS) exclude the couch during treatment planning. The present investigation aimed to evaluate the impact of couches and accessories on radiation therapy planning by quantifying the degree of attenuation for two-photon beam energies, 6 MV and 10 MV, at two different field sizes, 5 cm x 5 cm and 10 cm x 10 cm.   
Methods: An x-ray radiation beam at two energies (6 MV and 10 MV) generated by a linear accelerator (Elekta Synergy). The output dose was measured using a digital parallel plate ionization chamber of the IBA cc13 type (IBA Dosimetry, Germany), and the readings were recorded with a 2944 Farmer Type chamber. Different commercially available couch tops and accessories evaluated in this study. 
Results: The results show that the highest attenuation values were observed at 1300 gantry angles for both energies and field sizes. The lowest attenuation values were recorded at 1000 gantry angles with 6 MV energy for 5cm x 5cm and 10cm x 10cm field sizes. The breast board with D level demonstrated the highest attenuation of 6.27% and 5.51% for 6 MV and 10 MV energies, respectively. 
Conclusion: the findings indicate that the degree of attenuation is not uniform across all angles and may exceed tolerable limits, indicating the need for careful consideration during treatment planning to ensure optimal treatment outcomes.

Haydar H. Alabedi

Papers

Dosimetric assessment of IMRT treatment planning for unilateral breast cancer patient using Octavius phantom detector

Quality Assurance of LINAC by Analyzing the Profile of 6-MV and 10-MV Photon Beams Using Star Track Device

Electron Beam Profile Assessment of Linear Accelerator Using Startrack Quality Assurance Device

The Effect of Modulation Complexity Score (MCS) on the IMRT Treatment Planning Delivery Accuracy

Dosimetric effects and impacts caused by a carbon fiber table and its accessories in a linear accelerator