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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Asian Pacific Journal of Cancer Prevention
- نوع مقاله: Journal Article
- کلمات کلیدی: Mean Energy,Skin Dose,Leakage Radiation,Spatial Resolution and Contrast,Radiation Field Analyzer
- چکیده:
- چکیده انگلیسی: Purpose: The aim of this work is to study the dosimetric parameters of newly introduced 2.5 MV imaging x-ray beam used as inline imaging to do setup verification of the patient undergoing radiation therapy. As this x-ray beam is in megavoltage range but comprises of a lower energy spectrum. It is essential to study the pros and cons of 2.5 MV imaging x-ray beam for clinical use.Methods: The mean energy was calculated using the NIST XCOM table through MAC. Profile analysis was done using RFA to understand the percentage depth dose, degree of unflatteness, symmetry, penumbra and out of field dose. Dose to skin for the 2.5 MV x-ray beam was analysed for field sizes 10x10 cm2, 20x20 cm2, 30x30 cm2. Leakage measurements for treatment head and at the patient plane were done using IEC 819/98 protocol. Finally, the spatial resolution and contrast were analyzed with and without patient scatter medium. Results: The MAC at 15 cm off-axis was found to be lower than that at the CAX. Similarly, there was a decrease in mean energy from 0.47 MV to 0.37 MV at 15 cm off-axis. The reduction of mean energy towards off-axis is lower than the other high energy MV x-ray beams. The tuned absolute dose of 1 cGy/MU is consistent and within < ±1 %. The relative output factors were found to be in correlation with Co-60. The beam quality of 2.5 MV x-ray beam was found to be 0.4771. The profile parameters like the degree of unflatness of the 2.5 x-ray beam were studied at 85 %, 90 %, 95 % lateral distances, and the penumbra at different depth and field sizes are higher than the 6 MV treatment beam. In addition, out of field dose also drastically increases to a maximum of up to 30 % laterally at 5cm at deeper depths. The skin dose increases from 48.51 % to 88.15 % from 6 MV to 2.5 MV x-ray beam for the field size 10x10 cm2. Also, the skin dose increases from 88.15 % to 91.78 % from the field size 10x10 cm2 to 30x30 cm2. Although the measured leakage radiation for 2.5 MV x-ray beam at the patient plane and other than patient planes are with the tolerance limit, an increase in exposure towards gantry side compared to other areas around treatment head and the patient plane may lead to more skin dose to head and chest while imaging pelvis region. The MLC transmission of 2.5 MV x-ray beam such as inter, intra and edge effect are 0.40 %, 0.37 % and 11% respectively. The spatial resolution of 2.0, 1.25 and 0.9 LP/mm was observed for KV, 2.5MV, and 6 MV x-ray beams. The spatial resolution and contrast of 2.5 MV x-ray beam are superior to 6 MV x-ray beam and inferior to KV x-rays. Conclusions: The 2.5 MV x-ray imaging beam is analysed in view of beam characteristics and radiation safety to understand the above-studied concepts while using this imaging beam in a clinical situation. In future, if 2.5MV x-ray beam is used for treatment purpose with increased dose rate, the above-studied notions can be incorporated prior to implementation.
- انتشار مقاله: 14-03-1398
- نویسندگان: Tamilarasan Rajamanickam,Sivakumar Muthu,Perumal Murugan,Chinnaiah Dinesan,Chandrasekaran Mekala,Krishnamoorthy Senthilnathan,Narayanasamy Arunai Nambi Raj,Padmanabhan Ramesh Babu
- مشاهده
- جایگاه : پژوهشی
- مجله: Asian Pacific Journal of Cancer Prevention
- نوع مقاله: Journal Article
- کلمات کلیدی: effective atomic number,Mass attenuation coefficient,Total atomic and electronic cross-section,Electron density,Mean free path
- چکیده:
- چکیده انگلیسی: Purpose: This work presents the measure of fundamental interaction parameters like mass attenuation coefficient
(μ/ρ), mean energy, total atomic (σa) and electronic (σe) cross section, effective atomic number (Zeff), electron density
(Nel) and mean free path (mfp) using FF and UF megavoltage x-ray beam for high Z implants. Methods: Narrow beam
geometry is used to find out mass attenuation coefficient (μ/ρ) (MAC) which is then used to calculate mean energy (using
NIST data), total atomic (σa) and electronic cross section (σe) for different energies. The effective atomic number (Zeff),
Electron density (Nel), mean free path (mfp) for both flattened and unflattened x-ray beams for high Z material stainless
steel (SS316) and titanium alloy (Grade 5) are studied. Results: The mean energies calculated from NIST data against
mass attenuation coefficient were in good agreement with Monte Carlo value. It shows that spectral weighted effective
atomic number is independent of megavoltage energies in the Compton region. Effective electron density calculated
using Zeff and MAC method is lesser compared to direct method for both high Z materials. The mean free path (mfp)
is higher along the central axis than off-axis for flattened beam in comparison to unflattened beam for both of the high
Z materials studied because of the variation in energy spectrum for both FF and UF x-ray beams. Conclusion: This
study elaborated the fundamental interaction parameters of different energies of flattened and unflattened x-ray beam
interactions with high Z materials such as Stainless Steel (SS316) and Titanium (Grade5) relevant in a clinical scenario.- انتشار مقاله: 14-03-1398
- نویسندگان: Tamilarasan Rajamanickam,Sivakumar Muthu,Perumal Murugan,Muddappa Pathikonda,Krishnamoorthy Senthilnathan,Narayanasamy Arunai Nambi Raj,Padmanabhan Ramesh Babu
- مشاهده