Portal dosimetry for pretreatment verification of IMRT plan: a comparison with 2D ion chamber array

Sharma, Dayananda Shamurailatpam; Mhatre, V.; Heigrujam, Malhotra; Talapatra, Kaustav; Mallik, Suman

doi:10.1120/jacmp.v11i4.3268

Cited by 38 publications

(29 citation statements)

References 27 publications

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“…Although the primary purpose of EPID is to verify patient positioning, but with the introduction of on board imagers for image guidance the EPID has been more utilised for machine QA and pre-treatment patient specific QA [11][12][13][14]. Dosimetry using EPIDs or portal dosimetry has received considerable attention recently due to its relatively high-resolution of 0.392mm amorphous silicon (a-Si) flat-panel detector [15][16][17][18]. Several authors have extensively studied the dosimetric properties of a-Si 500 and a-Si 1000 EPID and its application in IMRT [19][20][21][22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Dosimetric Comparison of a-Si 1200 and a-Si 1000 Electronic Portal Imager for Intensity Modulated Radiation Therapy (IMRT)

Mhatre¹,

Pilakkal²,

Chadha³

et al. 2018

J Nucl Med Radiat Ther

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Section: Introductionmentioning

confidence: 99%

Dosimetric Comparison of a-Si 1200 and a-Si 1000 Electronic Portal Imager for Intensity Modulated Radiation Therapy (IMRT)

Mhatre¹,

Pilakkal²,

Chadha³

et al. 2018

J Nucl Med Radiat Ther

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“…Bakhiari et al 1) used a 38% isointensity line of cine EPID images to verify multileaf collimator (MLC) leaf positions during VMAT delivery. Sharma et al 2) tested the EPID portal dosimetry for IMRT QA using 181 intensity modulated fields that was compared to a two-dimensional (2D) ion chamber array (MatriXX, IBA, Louvain-la-Neuve, Belgium), and concluded that both fluence verification methods produced comparable QA results. Clemente et al 3) reported that the portal dosimetry was a useful QA tool for dynamic and static IMRT delivery.…”

Section: Introductionmentioning

confidence: 99%

A Comparison Study of Volumetric Modulated Arc Therapy Quality Assurances Using Portal Dosimetry and MapCHECK 2

2014

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A Varian Portal Dosimetry system was compared to an isocentrically mounted MapCHECK 2 diode array for volumetric modulated arc therapy (VMAT) QA. A Varian TrueBeam STx with an aS-1000 digital imaging panel was used to acquire VMAT QA images for 13 plans using four photon energies (6,8, 10 and 15 MV). The EPID-based QA images were compared to the Portal Dose Image Prediction calculated in the Varian Eclipse treatment planning system (TPS). An isocentrically mounted Sun Nuclear MapCHECK 2 diode array with 5 cm water-equivalent buildup was also used for the VMAT QAs and the measurements were compared to a composite dose plane from the Eclipse TPS. A γtest was implemented in the Sun Nuclear Patient software with 10% threshold and absolute comparison at 1%/1 mm (dose difference/distance-to-agreement), 2%/2 mm, and 3%/3 mm criteria for both QA methods. The two-tailed paired Student's t-test was employed to analyze the statistical significance at 95% confidence level. The average γpassing rates were greater than 95% at 3%/3 mm using both methods for all four energies. The differences in the average passing rates between the two methods were within 1.7% and 1.6% of each other when analyzed at 2%/2 mm and 3%/3 mm, respectively. The EPID passing rates were somewhat better than the MapCHECK 2 when analyzed at 1%/1 mm; the difference was lower for 8 MV and 10 MV. However, the differences were not statistically significant for all criteria and energies (p-values ＞0.05). The EPID-based QA showed large off-axis over-response and dependence of γpassing rate on energy, while the MapCHECK 2 was susceptible to the MLC tongue-and-groove effect. The two fluence-based QA techniques can be an alternative tool of VMAT QA to each other, if the limitations of each QA method (mechanical sag, detector response, and detector alignment) are carefully considered.

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“…Several researchers have investigated the use of electronic portal imaging devices for quality assurance purposes such as MLC position verification (16)(17)(18) and IMRT patient specific dose verification (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29). Renner et al (24) reported on four different methods that have been introduced for the purpose of using the EPID for treatment verification: 1) Compute the dose from each beam to the EPID and compare to the actual EPID image of each beam (4-15); 2) Use the EPID to verify the leaf positions for intensity modulated fields (16)(17)(18); 3) Reconstruct the dose to the patient using the exit image acquired during treatment (20)(21)(22)(23); and 4) Convert the EPID images to an incident fluence distribution and use it for dose calculation employing the patient CT anatomy (24,25).…”

Section: Introductionmentioning

confidence: 99%

Patient Specific Pre-Treatment QA Verification Using an EPID Approach

Quino

Chen

Fitzpatrick

et al. 2014

Technol Cancer Res Treat

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A software program [MU-EPID], has been developed to perform patient specific pre-treatment quality assurance (QA) verification for intensity modulated radiation therapy (IMRT) using fluence maps measured with an electronic portal imaging device (EPID). The software converts the EPID acquired images of each IMRT beam, to fluence maps that are equivalent to those calculated by the treatment planning system (TPS). The software has the capability to process Varian, Elekta and Siemens EPID DICOM images. In the present investigation, several IMRT plans for different treatment sites were used to validate the software using the and gamma analysis comparisons were performed to evaluate the accuracy of our method. A gamma index analysis of the isocenter coronal plane was done for each plan and showed an average of 97.44% of gamma passing rate using a 3% and 3 mm gamma criterion. Isodose, DVH and dose profile comparisons were conducted between the original calculated plan and the measured reconstructed plan from the EPID images processed through the MU-EPID software. The results suggest that MU-EPID can be used clinically for patient specific IMRT QA, providing a comprehensive 3D dosimetric evaluation through DVH comparison as well as an option for a 2D gamma analysis.

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Portal dosimetry for pretreatment verification of IMRT plan: a comparison with 2D ion chamber array

Cited by 38 publications

References 27 publications

Dosimetric Comparison of a-Si 1200 and a-Si 1000 Electronic Portal Imager for Intensity Modulated Radiation Therapy (IMRT)

Dosimetric Comparison of a-Si 1200 and a-Si 1000 Electronic Portal Imager for Intensity Modulated Radiation Therapy (IMRT)

A Comparison Study of Volumetric Modulated Arc Therapy Quality Assurances Using Portal Dosimetry and MapCHECK 2

Patient Specific Pre-Treatment QA Verification Using an EPID Approach

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