scholarly journals The Influence of Volume Effect in 2D-array Ion Chamber on the Measurement of IMRT Dose Distribution

2013 ◽  
Vol 24 (1) ◽  
pp. 41 ◽  
Author(s):  
Sung Joon Kim ◽  
Seoung Jun Lee ◽  
In Kyu Park ◽  
Jeong Eun Lee ◽  
Shin Hyung Park ◽  
...  
Keyword(s):  
Dose Distribution ◽  
Volume Effect ◽  
Ion Chamber ◽  
2D Array

A study of enhanced dynamic wedge dosimetry using a 2D ion chamber array detector

2015 ◽  
Vol 14 (4) ◽  
pp. 394-402
Author(s):  
S. A. Syam Kumar ◽  
P. Aparna ◽  
P. T. Anjana ◽  
C. P. Aswathi ◽  
G. P. Sitha
Keyword(s):  
Array Detector ◽  
Good Tool ◽  
Dose Distributions ◽  
Ion Chamber ◽  
Dynamic Wedge ◽  
Shoulder Region ◽  
Different Depths ◽  
Solid Water ◽  
Scanned Images ◽  
2D Array

AbstractThe purpose of this work was to study the dosimetric properties of the enhanced dynamic wedge using a Seven29 ion chamber array. The PTW Seven29 ion chamber array and solid water phantoms were used for the study. Primarily, the solid water phantoms with the two-dimensional (2D) array were scanned using a computed tomography scanner at different depths. Using these scanned images, planning was performed for different wedge angles at 6 and 15 MV. A dose of 100 CGy was delivered in each case. For each delivery, the required monitoring units (MUs) were calculated. Using the same setup with a Varian Clinac iX, the calculated MU was delivered for different wedge angles. Subsequently, the different wedged dose distributions that had been obtained were analysed using Verisoft software. A shoulder-like region was observed in the profile; this region reduced as depth increased. The percentage deviation between the planned and measured doses at the shoulder region fell within the range of 0·9–4·3%. The standard deviation between planned and measured doses at shoulder region in the profile fell within 0·08±0·02 at different depths. The standard deviations between planned and measured wedge factors for different depths (2·5, 5, 10 and 15 cm) were 0·0021, 0·0007, 0·0050 and 0·0001 for 6 MV and 0·0024, 0·0191, 0·0013 and 0·0005 for 15 MV, respectively. On the basis of the studies that we performed, it can be concluded that the 2D ion chamber array is a good tool for enhanced dynamic wedge dosimetry.

scholarly journals Potential Defects and Improvements of Equivalent Uniform Dose Prediction Model Based on the Analysis of Radiation-Induced Brain Injury

2022 ◽  
Vol 11 ◽  
Author(s):  
Qing-Hua Du ◽  
Jian Li ◽  
Yi-Xiu Gan ◽  
Hui-Jun Zhu ◽  
Hai-Ying Yue ◽  
...  
Keyword(s):  
Brain Injury ◽  
Dose Distribution ◽  
Predictive Ability ◽  
Volume Effect ◽  
Equivalent Uniform Dose ◽  
Critical Dose ◽  
Dose Volume ◽  
Radiation Induced ◽  
Effect Parameter ◽  
The Impact

PurposeTo study the impact of dose distribution on volume-effect parameter and predictive ability of equivalent uniform dose (EUD) model, and to explore the improvements.Methods and MaterialsThe brains of 103 nasopharyngeal carcinoma patients treated with IMRT were segmented according to dose distribution (brain and left/right half-brain for similar distributions but different sizes; VD with different D for different distributions). Predictive ability of EUDVD (EUD of VD) for radiation-induced brain injury was assessed by receiver operating characteristics curve (ROC) and area under the curve (AUC). The optimal volume-effect parameter a of EUD was selected when AUC was maximal (mAUC). Correlations between mAUC, a and D were analyzed by Pearson correlation analysis. Both mAUC and a in brain and half-brain were compared by using paired samples t-tests. The optimal DV and VD points were selected for a simple comparison.ResultsThe mAUC of brain/half-brain EUD was 0.819/0.821 and the optimal a value was 21.5/22. When D increased, mAUC of EUDVD increased, while a decreased. The mAUC reached the maximum value when D was 50–55 Gy, and a was always 1 when D ≥55 Gy. The difference of mAUC/a between brain and half-brain was not significant. If a was in range of 1 to 22, AUC of brain/half-brain EUDV55 Gy (0.857–0.830/0.845–0.830) was always larger than that of brain/half-brain EUD (0.681–0.819/0.691–0.821). The AUCs of optimal dose/volume points were 0.801 (brain D2.5 cc), 0.823 (brain V70 Gy), 0.818 (half-brain D1 cc), and 0.827 (half-brain V69 Gy), respectively. Mean dose (equal to EUDVD with a = 1) of high-dose volume (V50 Gy–V60 Gy) was superior to traditional EUD and dose/volume points.ConclusionVolume-effect parameter of EUD is variable and related to dose distribution. EUD with large low-dose volume may not be better than simple dose/volume points. Critical-dose-volume EUD could improve the predictive ability and has an invariant volume-effect parameter. Mean dose may be the case in which critical-dose-volume EUD has the best predictive ability.

scholarly journals Leaf Open Time Sinogram (LOTS):  A novel approach for Patient specific quality assurance of Total marrow irradiation

2020 ◽  
Author(s):  
Rajesh Thiyagarajan ◽  
Dayananda Shamurailatpam Sharma ◽  
Suryakant Kaushik ◽  
Mayur Sawant ◽  
Ganapathy Krishnan ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Dose Distribution ◽  
Upper Body ◽  
Patient Specific ◽  
Reconstruction Method ◽  
Ion Chamber ◽  
Modulation Factor ◽  
Novel Approach ◽  
Open Time ◽  
Total Marrow Irradiation

Abstract There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for total marrow (TMI) and Lymphoid (TMLI) irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured leaf open time sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98%(D98%) and 2%(D2%) of PTVs. Same comparison was extended for ten treatment plans from five TMI/TMLI patients. In all non-TMI/TMLI patients, reconstructed absolute dose was within ±1.8% of planned and IC measurement. The planned dose distribution agrees with reconstructed and ArcCheck measured dose with mean(SD) 3Dγ of 98.7%(1.57%) and 2Dγ of 99.48%(0.81%). The deviation in D98% and D2% were within 1.71% and 4.1% respectively. In all 25 measurement locations from TMI/TMLI patients, planned and IC measured absolute dose agrees within ±1.2%. Although sectorial fluence verification using ArcCHECK measurement for PTVs chest from five upper body TMI/TMLI plans showed mean±SD 2Dγ of 97.82%±1.27%, the reconstruction method resulted poor mean(SD) 3Dγ of 92.00%(±5.83%), 64.80%(±28.28%), 69.20%(±30.46%), 60.80%(±19.37%) and 73.2% (±20.36%) for PTVs brain, chest, torso, limb and upper body respectively. The corresponding deviation in median D98% and D2% of all PTVs were <3.8% and 9.5%. Re-optimization of all upper body TMI/TMLI plans with new pitch and modulation factor of 0.3 and 3 leads significant improvement with 3Dγ of 100% for all PTVs and median D98% and D2% <1.6%. LOTS based PSQA for TMI/TMLI is accurate, robust and efficient. A field width, pitch and modulation factor of 5cm, 0.3 and 3 for upper body TMI/TMLI plan is suggested for better dosimetric outcome and PSQA results.

scholarly journals Leaf Open Time Sinogram (LOTS):  A novel approach for Patient specific quality assurance of Total marrow irradiation

2020 ◽  
Author(s):  
Rajesh Thiyagarajan ◽  
Dayananda Shamurailatpam Sharma ◽  
Suryakant Kaushik ◽  
Mayur Sawant ◽  
Ganapathy Krishnan ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Dose Distribution ◽  
Upper Body ◽  
Patient Specific ◽  
Reconstruction Method ◽  
Ion Chamber ◽  
Modulation Factor ◽  
Novel Approach ◽  
Open Time ◽  
Total Marrow Irradiation

Abstract There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for total marrow (TMI) and Lymphoid (TMLI) irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured leaf open time sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98%(D98%) and 2%(D2%) of PTVs. Same comparison was extended for ten treatment plans from five TMI/TMLI patients. In all non-TMI/TMLI patients, reconstructed absolute dose was within ±1.8% of planned and IC measurement. The planned dose distribution agrees with reconstructed and ArcCheck measured dose with mean(SD) 3Dγ of 98.7%(1.57%) and 2Dγ of 99.48%(0.81%). The deviation in D98% and D2% were within 1.71% and 4.1% respectively. In all 25 measurement locations from TMI/TMLI patients, planned and IC measured absolute dose agrees within ±1.2%. Although sectorial fluence verification using ArcCHECK measurement for PTVs chest from five upper body TMI/TMLI plans showed mean±SD 2Dγ of 97.82%±1.27%, the reconstruction method resulted poor mean(SD) 3Dγ of 92.00%(±5.83%), 64.80%(±28.28%), 69.20%(±30.46%), 60.80%(±19.37%) and 73.2% (±20.36%) for PTVs brain, chest, torso, limb and upper body respectively. The corresponding deviation in median D98% and D2% of all PTVs were <3.8% and 9.5%. Re-optimization of all upper body TMI/TMLI plans with new pitch and modulation factor of 0.3 and 3 leads significant improvement with 3Dγ of 100% for all PTVs and median D98% and D2% <1.6%. LOTS based PSQA for TMI/TMLI is accurate, robust and efficient. A field width, pitch and modulation factor of 5cm, 0.3 and 3 for upper body TMI/TMLI plan is suggested for better dosimetric outcome and PSQA results.

scholarly journals Evaluation of low energy X-ray depth dose distribution by gafchromic film for dosimetry in food irradiation

2020 ◽  
Vol 23 (2) ◽  
pp. First
Author(s):  
Ngoc Hoang Van ◽  
Huy Viet Le ◽  
Son An Nguyen ◽  
Kume Tamikazu
Keyword(s):  
Dose Distribution ◽  
Low Energy ◽  
Food Irradiation ◽  
Radiation Processing ◽  
X Ray ◽  
Gafchromic Film ◽  
Ion Chamber ◽  
Dose Profile ◽  
Depth Dose ◽  
Depth Dose Distribution

Introduction: Dosimetry is of crucial importance in radiation processing of food. Among others, plastic film has been widely used for dosimetry in radiation therapy since its density is quite similar to the equivalent biological materials. In this study, the depth dose distribution was estimated by using gafchromic film for the purpose of dosimetry in food irradiation. Experimental: The HD-V2 gafchromic dosimetry film was employed to measure the interested dose instead of ion chamber. A stack of 19 PMMA (polymethyl methacrylate) sheets interleaved with 20 pieces of gafchromic film was made. The phantom was applied in the low energy X-ray beams (maximum 100 keV) to obtain the depth dose profile. Results: A significant correlation between absorbed doses (D) and color level or optical density (O.D.) of irradiated dosimetry films was observed. The fitting function has the form of , where a, b, c are the parameters to be fitted. The depth dose distribution in the 30 mm thickness phantom was inferred from the calibration. Conclusion: The present method and the depth dose profile to be obtained are very meaningful in the processing of foodstuffs by radiation.

scholarly journals Leaf open time sinogram (LOTS): a novel approach for patient specific quality assurance of total marrow irradiation

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Rajesh Thiyagarajan ◽  
Dayananda Shamurailatpam Sharma ◽  
Suryakant Kaushik ◽  
Mayur Sawant ◽  
K. Ganapathy ◽  
...  
Keyword(s):  
Quality Assurance ◽  
Dose Distribution ◽  
Upper Body ◽  
Patient Specific ◽  
Reconstruction Method ◽  
Ion Chamber ◽  
Modulation Factor ◽  
Novel Approach ◽  
Open Time ◽  
Total Marrow Irradiation

Abstract There is no ideal detector-phantom combination to perform patient specific quality assurance (PSQA) for Total Marrow (TMI) and Lymphoid (TMLI) Irradiation plan. In this study, 3D dose reconstruction using mega voltage computed tomography detectors measured Leaf Open Time Sinogram (LOTS) was investigated for PSQA of TMI/TMLI patients in helical tomotherapy. The feasibility of this method was first validated for ten non-TMI/TMLI patients, by comparing reconstructed dose with (a) ion-chamber (IC) and helical detector array (ArcCheck) measurement and (b) planned dose distribution using 3Dγ analysis for 3%@3mm and dose to 98% (D98%) and 2% (D2%) of PTVs. Same comparison was extended for ten treatment plans from five TMI/TMLI patients. In all non-TMI/TMLI patients, reconstructed absolute dose was within ± 1.80% of planned and IC measurement. The planned dose distribution agreed with reconstructed and ArcCheck measured dose with mean (SD) 3Dγ of 98.70% (1.57%) and 2Dγ of 99.48% (0.81%). The deviation in D98% and D2% were within 1.71% and 4.10% respectively. In all 25 measurement locations from TMI/TMLI patients, planned and IC measured absolute dose agreed within ± 1.20%. Although sectorial fluence verification using ArcCHECK measurement for PTVs chest from the five upper body TMI/TMLI plans showed mean ± SD 2Dγ of 97.82% ± 1.27%, the reconstruction method resulted poor mean (SD) 3Dγ of 92.00% (± 5.83%), 64.80% (± 28.28%), 69.20% (± 30.46%), 60.80% (± 19.37%) and 73.2% (± 20.36%) for PTVs brain, chest, torso, limb and upper body respectively. The corresponding deviation in median D98% and D2% of all PTVs were < 3.80% and 9.50%. Re-optimization of all upper body TMI/TMLI plans with new pitch and modulation factor of 0.3 and 3 leads significant improvement with 3Dγ of 100% for all PTVs and median D98% and D2% < 1.6%. LOTS based PSQA for TMI/TMLI is accurate, robust and efficient. A field width, pitch and modulation factor of 5 cm, 0.3 and 3 for upper body TMI/TMLI plan is suggested for better dosimetric outcome and PSQA results.

Statistical analysis on 2D array of ion chamber performance

2015 ◽  
Vol 14 (2) ◽  
pp. 194-201
Author(s):  
Akbar Anvari ◽  
Seyed Mahmoud Reza Aghamiri ◽  
Seyed Rabie Mahdavi ◽  
Parham Alaei
Keyword(s):  
Statistical Analysis ◽  
Field Size ◽  
Coefficient Of Determination ◽  
Detector Response ◽  
Maximum Deviation ◽  
High Dose ◽  
Ion Chamber ◽  
Ionisation Chamber ◽  
2D Array

AbstractPurposeIn this work, dosimetric properties of the PTW Octavius detector in and out of the irradiation field have been evaluated. The 2D array of ion chambers has the potential to simplify the linear accelerator QA and pre-treatment verification.Materials and methodsThe evaluation was performed using customised written codes in Matlab and SPSS software for statistical analysis.ResultsExperiments indicate that the reproducibility and stability of the measurements were excellent; the detector showed the same signal with a maximum deviation of <0·5% in the short and long term. Comparisons of the ion chamber with the detector showed the same results with a maximum deviation of ~0·1%. As the detector response is linear with the dose, it can be used for the measurement at regions of high-dose gradient effectively. Logarithmic regression y=0·127 ln(x)+0·729 for detector signal and field size changes yielded a coefficient of determination of 0·997. The dose value decreases with increase in source-to-surface distance, which was modelled using a binomial regression with a coefficient of determination of 0·998 that agrees with the ionisation chamber measurement within 1%.ConclusionOn the basis of the measurements and comparisons performed, this system is a reliable and accurate dosimeter for quality assurance in radiotherapy.

To determine the source dwell positions of HDR brachytherapy using 2D 729 ion chamber array

2015 ◽  
Vol 14 (4) ◽  
pp. 403-409
Author(s):  
S. A. Syam Kumar ◽  
Sitha P. Gangadharan ◽  
Aswathi P. Cheruparambil ◽  
Anjana T. Parakat ◽  
Aparna Perumangat
Keyword(s):  
High Dose Rate ◽  
Radiochromic Film ◽  
High Dose ◽  
Hdr Brachytherapy ◽  
Positional Accuracy ◽  
Ion Chamber ◽  
Ionisation Chamber ◽  
Standard Deviations ◽  
Dwell Position ◽  
2D Array

AbstractThe purpose of this study was to determine the dwell position of a high-dose-rate (HDR) brachytherapy Ir-192 source using a PTW Seven29 2D detector array. A Nucletron Microselectron HDR device and 2D array ionisation chamber, equipped with 729 ionisation chambers uniformly arranged in a 27×27 matrix with an active array area of 27×27 cm2, were used for this study. Different dwell positions were assigned in the HDR machine. Rigid interstitial needles and a vaginal applicator were positioned on the 2D array, which was then exposed according to the programmed dwell positions. Subsequently, the positional accuracy of the source position was analysed. This process was repeated for different dwell positions. The results were analysed using an in-house-developed Excel programme. Different random dwell position checks as well as dwell position measurements were performed using a radiochromic film. The dwell positions measured by the 2D array were found to be in good agreement with those measured by the film. The standard deviations between the doses obtained from the different dwell positions were 0·191828, 0·329973, 0·370632 and 0·779939, whereas the corresponding standard deviations of the doses at the vaginal cylinder were 0·60303, 0·242808, 0·242808 and 0·065309. When the planned and measured dwell positions were plotted, a linear relationship was obtained.

scholarly journals Method for calculation the absolute dose in the Monte Carlo simulation

2019 ◽  
Vol 2 (5) ◽  
pp. 90-96
Author(s):  
Oanh Thi Luong ◽  
Luong Thanh Dang ◽  
Tai Thanh Duong
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
General Hospital ◽  
Dose Distribution ◽  
Linear Accelerator ◽  
Photon Beams ◽  
Ion Chamber ◽  
Measured Dose ◽  
The Absolute ◽  
Good Agreement

In this study, we presented the method for calculation the absolute dose in the Monte Carlo simulation following the prescription of Popescu et al for the 6 MV photon energy. The BEAMnrc was used to simulate 6 MV photon beams from a Siemens Primus M5497 linear accelerator at DongNai general hospital. The DOSXYZnrc was then used to calculate the dose distribution in a homogeneous phantom (in form of CT images). The absolute dose obtained from the MC and TPS were compared with measured ones using an ion chamber (Farmer Type Chamber FC65-P, IBA). The average doses discrepancy between the simulated and measured dose was 0.53±0.37% and between the simulated and TPS was 1.00±0.51%. Results showed good agreement between simulated, measured and calculated dosed on a homogeneous phantom.

Sign in / Sign up

Export Citation Format

Share Document