Monte Carlo study of MLC fields for cobalt therapy machine

Ayyangar, Komanduri M.; Rani, Roopa A; Kumar, Anil; Reddy, A.R.

doi:10.4103/0971-6203.131279

Cited by 7 publications

(6 citation statements)

References 4 publications

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“…The design and radiation characteristic study of prototype MLCs were presented in conferences[ 2 3 4 ] and reported. [ 32 ] It has been previously[ 33 ] demonstrated that the designed MLCs can be successfully used for conformal therapy. Due to intensive use of multi-leaf collimators (MLCs) in clinics, it is important to find an optimum design for the leaves.…”

Section: Aterials and M Ethodsmentioning

confidence: 99%

Estimation of skin doses for retrofit prototype multileaf collimators designed for telecobalt therapy machine

Rani¹,

Ayyangar

Reddy

et al. 2020

J Med Phys

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Aim: The objective of this study was to evaluate skin dose based on retrofit prototype multileaf collimators (MLCs), designed for cobalt-60 teletherapy machine. Since patient's skin is sensitive to radiation, evaluation of skin dose is of utmost importance for investigating the risk of late effects. Materials and Methods: Measurements were performed with a Phoenix cobalt-60 teletherapy machine and the detector used was EBT3 radiochromic film. The experiments were performed in a solid water phantom with two prototype MLCs mounted to the machine. Dose readings were taken by placing the films at source-to-surface distance (SSD) of 60 cm, 65 cm, 70 cm, 75 cm, 80 cm, 85 cm, and 90 cm for various MLC-generated field sizes starting from 2 cm × 2 cm to 14 cm × 14 cm. The films were analyzed using custom made programs. The measured doses were normalized to the dose at dmax for that particular measurement of SSD. Results: The skin dose is expressed as a percentage of dose at dose maximum. In general, the skin dose increases with field size and decreases with SSD. The measurements indicate surface doses within 20%–60% for the investigated SSD range. Furthermore, there is no significant difference between the surface doses of two prototype MLCs studied. Conclusions: From the measurements, it can be concluded that there is good skin sparing even at close distance to the MLCs. The skin dose is <50% for SSDs >65 cm. A minimum gap of 5 cm is required to produce acceptable skin dose.

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Section: Aterials and M Ethodsmentioning

confidence: 99%

Estimation of skin doses for retrofit prototype multileaf collimators designed for telecobalt therapy machine

Rani¹,

Ayyangar

Reddy

et al. 2020

J Med Phys

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“…The design and radiation characteristic study of prototype-1 MLCs were presented in conferences [ 8 - 10 ] and reported [ 5 , 11 ]. For both the prototypes 1 and 2, the material used was tungsten alloy with density of 18 g/cm 3 (W 95% + Ni 3.5% + Cu 1.5%).…”

Section: Methodsmentioning

confidence: 99%

“…The Monte Carlo (MC) simulations were carried out using the same machine specifications which were explained in detail in our previous simulations as well [ 11 ]. The MLC leaves were opened to 6 × 6 cm 2 square field with the collimator jaws wide open.…”

Section: Methodsmentioning

confidence: 99%

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Validation of Leaf Design Characteristics of an Add-on Automated Multi Leaf Collimator for Telecobalt Therapy Machine

et al. 2021

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Background: In developing countries like India, cobalt-60 machines still find their applicability, considering the cost and maintenance issues. With a view to deliver conformal treatment plans using teletherapy machines, an automated Multi-Leaf Collimator (MLC) was developed for the existing machines as a retrofit attachment to the collimator assembly without any modifications to the unit.Objective: This study aims to investigate the radiation characteristics of leaf designs incorporated in two add-on prototype MLC systems with respect to the shape of leaf projected at the isocenter plane and the isodose distribution around the target. Besides, the dosimetric characteristics of prototype MLC with divergent leaf design are validated through simulation and experimental measurements. Material and Methods:In this experimental study, two add-on prototype MLC systems were designed and fabricated. The characteristic measurements of leaf designs incorporated in both the prototypes were carried out using Gafchromic films (GAF) and compared with Monte Carlo (MC) simulations. For divergent leaf design, beam profiles were obtained using Monte Carlo simulations which are complemented with the results obtained from measurements of radiochromic films and ionization chamber (IC) profiler. Dosimetric characteristics like radiation field width and beam penumbra were evaluated. Results:The Monte Carlo simulated data are in agreement with experimental data from IC profiler as well as from Radiochromic films. The results of this study are well within acceptable tolerance limits. Conclusion:The prototype MLC system designed for existing telecobalt machines supports its clinical applicability for conformal therapy to better manage treatment in rural areas, which can provide superior cost effective treatments.

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“…The comprehensive tests were performed to verify the correction and accuracy of data collection and machine modeling according to the AAPM report TG‐53. In addition, ROPS has been tested using certain measurements and Monte Carlo calculations for cobalt‐60 fields (15) . The details of ROPS specifications can be found from the website at https://sites.google.com/site/tjcsrops.…”

Section: Methodsmentioning

confidence: 99%

In‐house quality check of external beam plans using 3D treatment planning systems — a DVH comparison

Kumar

Akula²,

Ayyangar³

et al. 2016

J Applied Clin Med Phys

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This paper presents a new approach towards the quality assurance of external beam plans using in‐house‐developed DICOM import and export software in a clinical setup. The new approach is different from what is currently used in most clinics, viz., only MU and point dose are verified. The DICOM‐RT software generates ASCII files to import/export structure sets, treatment beam data, and dose‐volume histograms (DVH) from one treatment planning system (TPS) to the other. An efficient and reliable 3D planning system, ROPS, was used for verifying the accuracy of treatment plans and treatment plan parameters. With the use of this new approach, treatment plans planned using Varian Eclipse planning system were exported to ROPS planning system. Important treatment and dosimetrical data, such as the beam setup accuracy, target dose coverage, and dose to critical structures, were also quantitatively verified using DVH comparisons. Two external beam plans with diverse photon energies were selected to test the new approach. The satisfactory results show that the new approach is feasible, easy to use, and can be used as an adjunct test for patient treatment quality check.PACS number(s): 87.55.dk, 87.55.D‐, 87.55.Qr

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Monte Carlo study of MLC fields for cobalt therapy machine

Cited by 7 publications

References 4 publications

Estimation of skin doses for retrofit prototype multileaf collimators designed for telecobalt therapy machine

Estimation of skin doses for retrofit prototype multileaf collimators designed for telecobalt therapy machine

Validation of Leaf Design Characteristics of an Add-on Automated Multi Leaf Collimator for Telecobalt Therapy Machine

In‐house quality check of external beam plans using 3D treatment planning systems — a DVH comparison

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