The Dependence of Build-Up Ratio on the Field Size and the Source-Surface Distance

Abstract Introduction: Bolus material is frequently used on patient’s skin during radiation therapy to reduce or remove build-up effect for high-energy beams. However, the air-gaps formed between the bolus and the skin’s irregular surface reduce the accuracy of treatment planning. To achieve a good treatment outcome using bolus, experimental investigations are required to choose its thickness and to quantify the air-gap effect. Material and methods: Measurements for a 6 MV photon beam with a fixed source surface distance were carried out using the 31021 Semiflex 3D chamber into the water phantom. Firstly, the depth of maximum dose (R100) and the dose value at surface (Ds) were evaluated as a function of bolus thickness for some square fields. Secondly, to test the effect of the air-gaps ranged from 5 to 30 mm with a step of 5 mm between the bolus and the phantom surface, a water-equivalent RW3 (Goettingen White Water) slab form of 10 mm thickness was considered as a bolus. Results: We observed that the linear behaviour of R100 in terms of the bolus thickness makes the choice of this parameter more convenient depending on field size. In addition, increasing the air-gaps widens the penumbra and created electrons that have a greater probability to quit the radiation field borders before reaching the surface. The dose spread of the off-field area could have a significant influence on the patient treatment. Conclusion: Based on dose distribution comparisons between the measurements with and without air-gaps for the field size of 100 mm × 100 mm, it has been demonstrated that a maximum air-gap value lower than 5 mm would be desirable for an efficient use of the bolus technique.

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ANALISIS NILAI PERCENTAGE DEPTH DOSE(PDD) TERHADAP VARIASI KEDALAMAN TARGET DAN LUAS LAPANGAN PENYINARAN MENGGUNAKAN PESAWAT LINAC-CX

Komunikasi Fisika Indonesia ◽

10.31258/jkfi.15.2.93-97 ◽

2018 ◽

Vol 15 (2) ◽

pp. 93

Author(s):

Dian Milvita ◽

Alimin Mahyudin ◽

Vinny Alvionita

Keyword(s):

Radiation Dose ◽

Maximum Depth ◽

Field Size ◽

Source Surface ◽

Radiation Doses ◽

Energy Beam ◽

Percentage Depth Dose ◽

Depth Dose ◽

Value Measurement ◽

Target Depth

Percentage Depth Dose (PDD) value measurement is done by varying the target depth and field size. The study was carried out with variations in target depth of 0 cm to 30 cm with 1 cm intervals and fields size ranging from (5x5) cm2 to (39x39) cm2 with intervals (2x2) cm2. PDD is a comparison of the radiation dose at a depth to the radiation dose at the maximum depth normalized by percentage. This study was also conducted to determine the value of radiation doses received by phantoms from the PDD measurement value. This research used 2 photon energy beam that is 6 MV and 10 MV. This study uses water phantom as a substitute for patients with radiation source technique Source Surface Distance (SSD). PDD measurements were performed using a chamber ionization detector. The results obtained showed that the number of radiation doses received by fantom increased to the maximum depth (zmax). After passing zmaks, the radiation dose received by the phantom has decreased. Likewise along with the increase in the amount of radiation field, the value of radiation doses received by phantoms will also increase.

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COMPARISON OF ENERGY DOSES 10 MV DISTRIBUTION USING PERCENTAGE DEPTH DOSE (PDD) METHOD ON LINAC: ELECTA AND SIEMENS

Jurnal Natural ◽

10.24815/jn.v18i2.11133 ◽

2018 ◽

Vol 18 (2) ◽

pp. 85-88

Author(s):

Martha Rianna ◽

Herty Afrina Sianturi ◽

Hariyati Lubis ◽

Awan Pelawi ◽

Timbangen Sembiring ◽

...

Keyword(s):

Photon Energy ◽

Dose Distribution ◽

Source Surface ◽

Surface Distance ◽

Percentage Depth Dose ◽

Depth Dose

The patient dosing on Linac (Electa and Siemens) can be determined by Source Surface Distance (SSD) technique using Precentage Depth Doses (PDD) method. The study was conducted by measuring PDD to compare the dosage distribution calculations on Linac Electa and Siemens device of photon energy at 10 MV. PDD is done with a 100 cm SSD technique at a depth of 0 to 25 cm. The dose distribution results between the Electrical and the Siemens PDD are almost the same in that the Dmax at 10 MV Siemens photon energy occurs at a depth of 20 mm while the 10 MV Electa photon energy occurs at a depth of 21 mm. Both Linac Electa and Siemens device this at the same energy of 10 MV there is a difference of 95.23%.Keywords: Distrubusi dose, PDD, Photon Energy, Quality File Index

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Analysis of Tissue Phantom Ratio of the Megavoltage Photon Beams

Malaysian Journal of Medical and Biological Research ◽

10.18034/mjmbr.v5i2.452 ◽

2018 ◽

Vol 5 (2) ◽

pp. 61-68

Author(s):

M. A. Rahman ◽

M. Jahangir Alam

Keyword(s):

General Hospital ◽

Source Surface ◽

Photon Beams ◽

Surface Distance ◽

Mean Error ◽

Percentage Depth Dose ◽

Depth Dose ◽

Tissue Phantom ◽

Phantom Tissue ◽

Good Agreement

Iso-centric beam data, phantom tissue ratios (TPR) are a dosimetric quantity commonly used to describe the change in dose with depth in tissue. Measurement of this is time-consuming and has the possibility of lose the consistency. The value of this quantity of any filed size in any depth is possible to calculate conveniently by the newly developed formula using only percentage depth dose (PDD) data of two fields. PDD for square fields ranging from 2 to 30 cm and various depths in increment of 0.4 cm up to maximum 30 cm have been measured in water at a fixed source surface distance (SSD) of 90 cm for 4, 6 and 15 MV photon beams in Ahsania Mission Cancer & General Hospital (AMCGH), Dhaka, Bangladesh. TPR values calculating for these energies of the same field sizes, depths and SSD by using the developed formula compared with those determined from the measured PDD data using a standard formula and had the good agreement. Mean error less than 1% observed between these TPR values.

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Analysis of Effect of Change Source to Surface Distance (SSD) and the Field Size to Distribution Dose Using Monte Carlo Method-EGSnrc

Indonesian Journal of Physics ◽

10.5614/itb.ijp.2019.30.1.3 ◽

2019 ◽

Vol 30 (1) ◽

pp. 14-17

Author(s):

Intan Dillia Nurhadi ◽

Ridwan Ramdani ◽

Freddy Haryanto ◽

Yudha Satya Perkasa ◽

Mada Sanjaya

Keyword(s):

Monte Carlo ◽

Modeling And Simulation ◽

Radiation Source ◽

Maximum Dose ◽

Size Variation ◽

Field Size ◽

Virtual Model ◽

Surface Distance ◽

Percentage Depth Dose ◽

Depth Dose

Research was conducted to analyze the effect of changes in the distance radiation source to the surface it is called the medium Source to Surface Distance (SSD) and wide exposure field (Field Size) on the distribution of the dose in linear air Accelerator (LINAC) using Monte Carlo - EGSnrc. Monte Carlo simulation is used for modeling and simulation head linac at BEAMnrc. Virtual model of the linac is made based on the data characteristics of the aircraft Linac Varian Clinac iX then its output obtained information characteristic photon beam using BEAMDP, while modeling and simulation phantom done on DOSXYZnrc with the size of the phantom is (40x40x40) cm3 , with the material in the form of water, using a beam of photons 6 MV, testing variation SSD at 80 cm, 90 cm, 100.1 cm, 110 cm, 120 cm and variation field size is (6x6) cm2, (10x10) cm2, (20x20) cm2 to obtain disribution of dosage form of curves Percentage Depth dose (PDD) and Profile dose. The results showed that the smaller distance radiation source to the surface of the medium (SSD) and the greater the broad field (field size), then increasing the dose distribution is obtained. In the SSD and Field Size variation, the radiation dose will continue to rise significantly from the surface of the medium 0 cm to a depth of maximum dose (Dmax), then the dose began to decline after passing the depth Dmax.

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Determination of effective source to surface distance and cutout factor in small fields in electron beam radiotherapy: A comparison of different dosimeters

Polish Journal of Medical Physics and Engineering ◽

10.2478/pjmpe-2020-0028 ◽

2020 ◽

Vol 26 (4) ◽

pp. 235-242

Author(s):

Mohamad Reza Bayatiani ◽

Fatemeh Fallahi ◽

Akbar Aliasgharzadeh ◽

Mahdi Ghorbani ◽

Benyamin Khajetash ◽

...

Keyword(s):

Electron Beam ◽

Linear Accelerator ◽

Beam Energy ◽

Field Size ◽

Surface Distance ◽

Small Fields ◽

Dosimetry System ◽

Electron Beam Radiotherapy ◽

Effective Source

AbstractObjective: The main purpose of this study is to calculate the effective source to surface distance (SSDeff) of small and large electron fields in 10, 15, and 18 MeV energies, and to investigate the effect of SSD on the cutout factor for electron beams a linear accelerator. The accuracy of different dosimeters is also evaluated.Materials and methods: In the current study, Elekta Precise linear accelerator was used in electron beam energies of 10, 15, and 18 MeV. The measurements were performed in a PTW water phantom (model MP3-M). A Semiflex and Advanced Markus ionization chambers and a Diode E detector were used for dosimetry. SSDeff in 100, 105, 110, 115, and 120 cm SSDs for 1.5 × 1.5 cm2 to 5 × 5 cm2 (small fields) and 6 × 6 cm2 to 20 × 20 cm2 (large fields) field sizes were obtained. The cutout factor was measured for the small fields.Results: SSDeff in small fields is highly dependent on energy and field size and increases with increasing electron beam energy and field size. For large electron fields, with some exceptions for the 20 × 20 cm2 field, this quantity also increases with energy. The SSDeff was increased with increasing beam energy and field size for all three detectors.Conclusion: The SSDeff varies significantly for different field sizes or cutouts. It is recommended that SSDeff be determined for each electron beam size or cutout. Selecting an appropriate dosimetry system can have an effect in determining cutout factor.

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Analisis Hasil Pengukuran Tissue Maximum Ratio (TMR) terhadap Variasi Kedalaman Target dan Luas Lapangan Penyinaran Menggunakan Pesawat LINAC Tipe Clinac-CX

Jurnal Fisika Unand ◽

10.25077/jfu.7.2.97-101.2018 ◽

2018 ◽

Vol 7 (2) ◽

pp. 97-101

Author(s):

Vinny Alvionita ◽

Dian Milvita

Keyword(s):

Linear Accelerator ◽

Atomic Energy ◽

Source Surface ◽

Energy Agency ◽

Surface Distance

Telah dilakukan penelitian untuk mengetahui pengaruh variasi kedalaman target dan luas lapangan penyinaran terhadap penerimaan dosis radiasi pada fantom menggunakan pesawat terapi Linear Accelerator (LINAC) tipe Clinac CX. Penelitian dilakukan dengan variasi kedalaman (0-30) cm dengan interval 1 cm dan 18 variasi luas lapangan penyinaran dimulai dari (5x5) cm2 hingga (39x39) cm2 dengan interval 2 cm. Variasi kedalaman dan luas lapangan dilakukan untuk mendapatkan nilai Tissue Maximum Ratio (TMR). TMR merupakan rasio dosis radiasi di kedalaman tertentu terhadap dosis radiasi di kedalaman maksimum. Pada penelitian ini digunakan berkas energi foton sebesar 6 MV dan 10 MV, dengan teknik penyinaran Source Surface Distance (SSD). Penelitian ini dilakukan di dalam fantom air sebagai pengganti pasien menggunakan detektor ionisasi chamber. Hasil penelitian yang didapatkan menunjukkan bahwa semakin besar kedalaman target maka semakin besar pula nilai TMR yang diterima fantom hingga mencapai kedalaman maksimum (zmaks). Setelah melewati kedalaman maksimum (zmaks) nilai TMR yang didapatkan cenderung menurun. Selanjutnya semakin bertambah luas lapangan penyinaran maka semakin bertambah nilai TMR yang didapatkan. Nilai zmaks yang didapatkan untuk berkas foton berenergi 6 MV berkisar (1,35 – 1,75) cm, dan untuk berkas foton berenergi 10 MV berkisar (2,25-2,55) cm. Nilai zmaks ini berada dalam batas yang ditetapkan oleh Internasional Atomic Energy Agency (IAEA) yaitu 1,5 cm untuk energi 6 MV dan 2,5 cm untuk energi 10 MV. Kata kunci: fantom air, LINAC, Source Surface Distance (SSD), Tissue Maximum Ratio (TMR).

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