Linear array measurements of enhanced dynamic wedge and treatment planning system (TPS) calculation for 15 MV photon beam and comparison with electronic portal imaging device (EPID) measurements

AbstractPurpose:The main objective of this study is to assure the quality of cervical cancer treatment plans using an electronic portal imaging device (EPID) in RapidArc techniques.Materials and Methods:Fifteen cases of cervical cancer patients undergoing RapidArc technique were selected to evaluate the quality assurance (QA) of their treatment. The computed tomography (CT) of each patient was obtained with 3-mm-slice thickness and transferred to the Eclipse treatment planning system. The prescribed dose (PD) of 50·4 Gy with 1·8 Gy per fraction to planning target volume (PTV) was used for each patient. The aim of treatment planning was to achieve 95% of PD to cover 97%, and dose to the PTV should not receive 105% of the PD. All RapidArc plans were created using the AAA algorithm and treated on Varian DHX using 6 MV photon beam, with two full arcs. Gamma analysis was used to evaluate the quality of the treatment plans with accepting criteria of 95% at 3%/3 mm.Results:In this study, maximum and average gamma values were 2·53 ± 0·409 and 0·195 ± 0·059 showing very small deviation and indicating the smaller difference between both predicted and portal doses. Gamma Area changes from > 0·8 to > 1·2. SD increased to 5·4% and mean standard error increased to 4·67%.Conclusion:On the basis of these outcomes, we can summarise that the EPID is a useful tool for QA in standardising and evaluating RapidArc treatment plans of cervical cancer in routine clinical practice.

Download Full-text

Quality assurance of linear accelerator: a comprehensive system using electronic portal imaging device

Journal of Radiotherapy in Practice ◽

10.1017/s146039691800050x ◽

2018 ◽

Vol 18 (02) ◽

pp. 138-149

Author(s):

P. Niyas ◽

K. K. Abdullah ◽

M. P. Noufal ◽

R. Vysakh

Keyword(s):

Quality Assurance ◽

Linear Accelerator ◽

Planning System ◽

Treatment Planning System ◽

Patient Specific ◽

Array Detector ◽

Electronic Portal Imaging Device ◽

Imaging Device ◽

Portal Imaging ◽

Electronic Portal Imaging

AbstractAimThe Electronic Portal Imaging Device (EPID), primarily used for patient setup during radiotherapy sessions is also used for dosimetric measurements. In the present study, the feasibility of EPID in both machine and patient-specific quality assurance (QA) are investigated. We have developed a comprehensive software tool for effective utilisation of EPID in our institutional QA protocol.Materials and methodsPortal Vision aS1000, amorphous silicon portal detector attached to Clinac iX—Linear Accelerator (LINAC) was used to measure daily profile and output constancy, various Multi-Leaf Collimator (MLC) checks and patient plan verification. Different QA plans were generated with the help of Eclipse Treatment Planning System (TPS) and MLC shaper software. The indigenously developed MATLAB programs were used for image analysis. Flatness, symmetry, output constancy, Field Width at Half Maximum (FWHM) and fluence comparison were studied from images obtained from TPS and EPID dosimetry.ResultsThe 3 years institutional data of profile constancy and patient-specific QA measured using EPID were found within the acceptable limits. The daily output of photon beam correlated with the output obtained through solid phantom measurements. The Pearson correlation coefficients are 0.941 (p = 0.0001), 0.888 (p = 0.0188) and 0.917 (p = 0.0007) for the years of 2014, 2015 and 2016, respectively. The accuracy of MLC for shaping complex treatment fields was studied in terms of FWHM at different portions of various fields, showed good agreement between TPS-generated and EPID-measured MLC positions. The comparison of selected patient plans in EPID with an independent 2D array detector system showed statistically significant correlation between these two systems. Percentage difference between TPS computed and EPID measured fluence maps calculated for number of patients using MATLAB code also exhibited the validity of those plans for treatment.

Download Full-text

Radiotherapy Treatment Verification

Tumori Journal ◽

10.1177/030089169808400209 ◽

1998 ◽

Vol 84 (2) ◽

pp. 144-149 ◽

Cited By ~ 1

Author(s):

Raffaele Novario ◽

Paola Stucchi ◽

Lucia Perna ◽

Leopoldo Conte

Keyword(s):

Treatment Planning ◽

Ionization Chamber ◽

Planning System ◽

Treatment Planning System ◽

Imaging Device ◽

Portal Imaging ◽

Portal Images ◽

Dosimetric Verification ◽

Geometric Localization ◽

Radiotherapy Treatment

During a radiotherapy treatment, a dosimetric verification or a geometric localization can be done, in order to assess the quality of the treatment. The dosimetric verification is generally performed measuring the dose at some points inside (natural cavities) or outside the patient, and comparing it to the dose at the same points calculated and predicted by the treatment planning system. This can be done either with thermoluminescent or diodes dosimeters or with ionization chambers. The geometric localization can be done acquiring a portal image of the patient. Portal imaging can be performed either with films placed between metallic screens, or with an electronic portal imaging device such as fluoroscopic systems, solid state devices or matrix ionization chamber systems. In order to assess possible field placement errors, the portal images have to be compared with images obtained with the simulator in the same geometric conditions and/or with the digitally reconstructed radiograph (DRR) obtained with the treatment planning system. In particular, when using matrix ionization chamber systems, the portal images contain also information regarding the exit dose. This means that this kind of imaging device can be used both for geometric localization and for dosimetric verification. In this case, the exit dose measured by the portal image can be compared with the exit dose calculated and predicted by the treatment planning system. Some “in-vivo” applications of this methodology are presented.

Download Full-text

Quality Assurance of Dose Distribution of Photon Beam Planning by Anisotropic Analytical Algorithm (AAA)

Bangladesh Journal of Medical Physics ◽

10.3329/bjmp.v4i1.14686 ◽

2013 ◽

Vol 4 (1) ◽

pp. 43-49

Author(s):

M Jahangir Alam ◽

Syed Md Akram Hussain ◽

Kamila Afroj ◽

Shyam Kishore Shrivastava

Keyword(s):

Quality Assurance ◽

Treatment Planning ◽

Dose Distribution ◽

Maximum Dose ◽

Photon Beam ◽

Field Size ◽

Planning System ◽

Treatment Planning System ◽

Anisotropic Analytical Algorithm ◽

Analytical Algorithm

A three dimensional treatment planning system has been installed in the Oncology Center, Bangladesh. This system is based on the Anisotropic Analytical Algorithm (AAA). The aim of this study is to verify the validity of photon dose distribution which is calculated by this treatment planning system by comparing it with measured photon beam data in real water phantom. To do this verification, a quality assurance program, consisting of six tests, was performed. In this program, both the calculated output factors and dose at different conditions were compared with the measurement. As a result of that comparison, we found that the calculated output factor was in excellent agreement with the measured factors. Doses at depths beyond the depth of maximum dose calculated on-axis or off-axis in both the fields or penumbra region were found in good agreement with the measured dose under all conditions of energy, SSD and field size, for open and wedged fields. In the build up region, calculated and measured doses only agree (with a difference 2.0%) for field sizes > 5 × 5 cm2 up to 25 × 25 cm2. For smaller fields, the difference was higher than 2.0% because of the difficulty in dosimetry in that region. Dose calculation using treatment planning system based on the Anisotropic Analytical Algorithm (AAA) is accurate enough for clinical use except when calculating dose at depths above maximum dose for small field size.DOI: http://dx.doi.org/10.3329/bjmp.v4i1.14686 Bangladesh Journal of Medical Physics Vol.4 No.1 2011 43-49

Download Full-text