Uncertainties in the measurement of relative doses in radiotherapy

Abstract Both the measurement of the dose and the measurement of its distribution, like any other measurements, are subject to measurement uncertainties. These uncertainties affect all dose calculations and dose distributions in a patient’s body during treatment planning in radiotherapy. Measurement uncertainty is not a medical physicist’s error, but an inevitable element of their work. Planning the dose distribution in a patient’s body, we often try to reduce it in the volume of critical organs (OaR - Organ at Risk) or increase the minimum dose in the PTV region by a few percent. It is believed that the measurement uncertainty should be taken into account in these calculations at the stage of treatment planning. The paper presents the method of calculating the measurement uncertainty for different physical quantities in radiotherapy as percentage depth dose, profile function and output factor, due to the fact that these quantities have a particular impact on the calculated dose distributions in a patient’s body. The uncertainties that must be taken into account in planning treatment the planned dose per fraction and real in PTV, maybe different up to 4%.

Download Full-text

The Commissioning and Validation of EclipseTM Treatment Planning System on a Varian VitalBeamTM Medical Linear Accelerator for Photon and Electron Beams

Frontiers in Biomedical Technologies ◽

10.18502/fbt.v8i2.6514 ◽

2021 ◽

Author(s):

Samira Yazdani ◽

Fateme Shirani Takabi ◽

Abolfazl Nickfarjam

Keyword(s):

Treatment Planning ◽

Linear Accelerator ◽

Electron Beams ◽

Planning System ◽

Treatment Planning System ◽

Patient Treatment ◽

Depth Dose ◽

Tps Commissioning ◽

Calculated Dose ◽

Output Factors

Purpose: Commissioning of a linear accelerator is a process of acquiring a set of data used for patient treatment. This article presents the beam data measurement results from the commissioning of a VitalBeamTM linac. Materials and Methods: Dosimetric properties for 6,10, and 15 MV photon beams and 6, 9, 12, and 16 MeV electron beams have been performed. Parameters, including Percentage Depth Dose (PDD), depth dose profile, symmetry, flatness, quality index, output factors, and the vital data for Treatment Planning System (TPS) commissioning were measured. The imported data were checked by CIRS phantom accordingly to IAEA TRS-430, TECDOC. Eight different positions of CIRS phantom CT were planned and treated. Finally, the calculated dose at a determined position was compared with measuring data to TPS validation. Results: After comparing 84 points in a different plan, the 83 points were in agreement with the criteria, and just for one point in 15 MV failed. Conclusion: Commissioning of dose and field flatness and symmetry are in tolerance intervals given by Varian. This proves that the studied lines meet the specification and can be used in clinical practice with all available electron and photon energies.

Download Full-text

Design and Analysis Effect of Gantry Angle Photon Beam 4 MV on Dose Distributions using Monte Carlo Method EGSnrc Code System

Indonesian Journal of Physics ◽

10.5614/itb.ijp.2016.27.1.3 ◽

2016 ◽

Vol 27 (1) ◽

pp. 18-20

Author(s):

Uum Yuliani ◽

Ridwan Ramdani ◽

Freddy Haryanto ◽

Yudha Satya Perkasa ◽

Mada Sanjaya

Keyword(s):

Monte Carlo ◽

Vertical Axis ◽

Photon Beam ◽

Field Size ◽

Dose Calculations ◽

Dose Distributions ◽

Percentage Depth Dose ◽

Depth Dose ◽

Surface Field ◽

Gantry Angle

Varian linac modeling has been carried out to obtain Percentage Depth Dose (PDD) and profiles using variations gantry angle 0o, 15o, 30o , 45o in the vertical axis of the surface, field size 10x10 cm2, photon beam 4 MV and Monte Carlo simulations. Percentage Depth Dose and profile illustrates dose distributions in a phantom water measuring 40x40x40 cm3, changes gantry is one of the factors that determine the distribution of the dose to the patient research shows changes in Dmax in the Percentage Depth Dose is affected by changes in the angle gantry resulted in the addition of the area build up so it can be used for therapy in the region and produce skin sparing effects that can be used to protect the skin from exposure to radiation. The graph result is profiles obtained show lack simetrisan in areas positive quadrant has a distribution of fewer doses than the quadrant of negative as well as the slope of the surface so that it can be used for some cases treatments that require a depth and a certain slope, dose calculations are more accurate and can minimize side effects.

Download Full-text

Sci-Thur PM Therapy-04: Comparison of treatment planning system and Monte Carlo calculated dose distributions in an extreme water-lung interface phantom

Medical Physics ◽

10.1118/1.2244618 ◽

2006 ◽

Vol 33 (7Part1) ◽

pp. 2657-2658

Author(s):

I Gagne ◽

S Zavgorodni

Keyword(s):

Monte Carlo ◽

Treatment Planning ◽

Planning System ◽

Treatment Planning System ◽

Dose Distributions ◽

Calculated Dose

Download Full-text

Clinical experience using Delta 4 phantom for pretreatment patient-specific quality assurance in modern radiotherapy

Journal of Radiotherapy in Practice ◽

10.1017/s1460396918000572 ◽

2018 ◽

Vol 18 (02) ◽

pp. 210-214

Author(s):

R. P. Srivastava ◽

C. De Wagter

Keyword(s):

Quality Assurance ◽

Treatment Planning ◽

Volumetric Modulated Arc Therapy ◽

Planning System ◽

Treatment Planning System ◽

Patient Specific ◽

Dose Distributions ◽

Gamma Index ◽

Calculated Dose ◽

Treatment Plans

AbstractPurposeIn advanced radiotherapy techniques such as intensity-modulated radiation therapy (IMRT), the quality assurance (QA) process is essential. The aim of the study was to assure the treatment planning dose delivered during delivery of complex treatment plans. The QA standard is to perform patient-specific comparisons between planned doses and doses measured in a phantom.Materials and methodThe Delta 4 phantom (Scandidos, Uppsala, Sweden) has been used in this study. This device consists of diode matrices in two orthogonal planes inserted in a cylindrical acrylic phantom. Each diode is sampled per beam pulse so that the dose distribution can be evaluated on segment-by-segment, beam-by-beam, or as a composite plan from a single set of measurements. Ninety-five simple and complex radiotherapy treatment plans for different pathologies, planned using a treatment planning system (TPS) were delivered to the QA device. The planned and measured dose distributions were then compared and analysed. The gamma index was determined for different pathologies.ResultsThe evaluation was performed in terms of dose deviation, distance to agreement and gamma index passing rate. The measurements were in excellent agreement between with the calculated dose of the TPS and the QA device. Overall, good agreement was observed between measured and calculated doses in most cases with gamma values above 1 in >95% of measured points. Plan results for each test met the recommended dose goals.ConclusionThe delivery of IMRT and volumetric-modulated arc therapy (VMAT) plans was verified to correspond well with calculated dose distributions for different pathologies. We found the Delta 4 device is accurate and reproducible. Although Delta4 appears to be a straightforward device for measuring dose and allows measure in real-time dosimetry QA, it is a complex device and careful quality control is required before its use.

Download Full-text

Dose distribution verification for GZP6 sources: A comparison of Monte Carlo, radiochromic film, and GZP6 treatment planning system

Archive of oncology ◽

10.2298/aoo1202003t ◽

2012 ◽

Vol 20 (1-2) ◽

pp. 3-7 ◽

Cited By ~ 1

Author(s):

Bahreyni Toossi ◽

Mahdi Ghorbani ◽

Asghar Mowlavi ◽

Abdolreza Hashemian ◽

Soleimani Meigooni

Keyword(s):

Monte Carlo ◽

Treatment Planning ◽

Radiochromic Film ◽

Planning System ◽

Treatment Planning System ◽

Quality Assurance Program ◽

Monte Carlo Code ◽

Dose Calculations ◽

Planning Systems ◽

Dose Distributions

Background: Treatment planning systems (TPSs) are used for dose calculations in dose delivery by after loading brachytherapy machines. Such planning systems usually use simplified algorithms in their dose calculations. Verification of dose distributions produced by TPS is of clinical importance and is part of a quality assurance program. In this study, the dose distributions generated by GZP6 TPS for two GZP6 sources were verified. Methods: The evaluation was based on the inter comparisons between the isodose curves obtained through Monte Carlo simulations, radiochromic film measurements, and GZP6 treatment planning system. MCNPX Monte Carlo code was used to simulate the sources. Dose measurements were performed in a perspex phantom using Gafchromic? EBT radiochromic films. Comparisons between the results obtained from MC, RCF, and TPS were performed by gamma function calculations with 5% dose/2 mm distance criterion. Results: Based on gamma calculations our results showed that there was good agreement between the dose distributions obtained by the three aforementioned methods in both transverse and longitudinal planes for the GZP6 source No.2. However, for source No. 5, the agreement was good in the transverse plane but it was low in the longitudinal plane. Conclusion: The results showed that dose distributions certified by the GZP6 TPS for the GZP6 source No. 2 were validated. However, for source No. 5 some discrepancies were observed. Accurate knowledge of the activity of each active pellet in the source No. 5 can clarify the cause of the discrepancies.

Download Full-text