Fast transit portal dosimetry using density‐scaled layer modeling of aSi‐based electronic portal imaging device and Monte Carlo method

Jung, Jae Won; Kim, Jong Oh; Yeo, I; Cho, Young‐Bin; Kim, Sun Mo; DiBiase, Steven J.

doi:10.1118/1.4764563

Cited by 10 publications

(24 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…On another front, a number of groups have modeled the response of the EPID for dosimetric purposes using Monte Carlo techniques 16 , 17 . One group, in particular, was able to calculate accurate 2D dose maps inside a phantom by means of sophisticated EPID modeling 18 , 19 .…”

Section: Introductionmentioning

confidence: 99%

Two‐dimensional in vivo dose verification using portal imaging and correlation ratios

Peca

Brown

2014

J Applied Clin Med Phys

View full text Add to dashboard Cite

The electronic portal imaging device (EPID) has the potential to be used for in vivo dosimetry during radiation therapy as an additional dose delivery check. In this study we have extended a method developed by A. Piermattei and colleagues in 2006 that made use of EPID transit images (acquired during treatment) to calculate dose in the isocenter point. The extension allows calculation of two‐dimensional dose maps of the entire radiation field at the depth of isocenter. We quantified the variability of the ratio of EPID signal to dose in the isocenter plane in Solid Water phantoms of various thicknesses and with various field sizes, and designed a field edge dose calculation correction. To validate the method, we designed three realistic conventional radiation therapy treatment plans on a thorax and head anthropomorphic phantom (whole brain, brain primary, lung tumor). Using CT data, EPID transit images, EPID signal‐to‐dose correlation, and our edge correction, we calculated dose in the isocenter plane and compared it with the treatment planning system's prediction. Gamma evaluation (3%, 3 mm) showed good agreement (Pγ<1 ≥ 96.5%) for all fields of the whole brain and brain primary plans. In the presence of lung, however, our algorithm overestimated dose by 7%–9%. This 2D EPID‐based in vivo dosimetry method can be used for posttreatment dose verification, thereby improving the safety and quality of patient treatments. With future work, it may be extended to measure dose in real time and to prevent harmful delivery errors.PACS numbers: 87.55.km, 87.55.Qr, 87.55.T‐

show abstract

Section: Introductionmentioning

confidence: 99%

Two‐dimensional in vivo dose verification using portal imaging and correlation ratios

Peca

Brown

2014

J Applied Clin Med Phys

View full text Add to dashboard Cite

show abstract

“…Our calculational EPID model was determined to be accurate within 2% from EPID measurement. 28 This difference affected dose reconstruction accuracy because our algorithm utilizes calculated EPID response. The dose reconstruction algorithm itself is as accurate as forward MC calculation at beam axis (i.e., flat dose region), as it utilizes MC calculated responses.…”

Section: Iiia Reconstruction Methods Validationmentioning

confidence: 99%

“…27 After the image calibration, the dose calibration of EPID images was performed, creating a dose calibration matrix between the measured image of the flat flood field to the corresponding calculated dose image using the EPID model described in our other study. 28 After the calibration, the test beam was irradiated on the 10-cm thick homogeneous phantom [ Fig. 2(a)] and EPID that was placed at 150 cm.…”

Section: Iic2 Measurementsmentioning

confidence: 99%

Feasibility study on inverse four‐dimensional dose reconstruction using the continuous dose‐image of EPID

Yeo

Jung

et al. 2013

Medical Physics

Self Cite

View full text Add to dashboard Cite

Purpose: When an intensity-modulated radiation beam is delivered to a moving target, the interplay effect between dynamic beam delivery and the target motion due to miss-synchronization can cause unpredictable dose delivery. The portal dose image in electronic portal imaging device (EPID) represents radiation attenuated and scattered through target media. Thus, it may possess information about delivered radiation to the target. Using a continuous scan (cine) mode of EPID, which provides temporal dose images related to target and beam movements, the authors' goal is to perform four-dimensional (4D) dose reconstruction. Methods: To evaluate this hypothesis, first, the authors have derived and subsequently validated a fast method of dose reconstruction based on virtual beamlet calculations of dose responses using a test intensity-modulated beam. This method was necessary for processing a large number of EPID images pertinent for four-dimensional reconstruction. Second, cine mode acquisition after summation over all images was validated through comparison with integration mode acquisition on EPID (IAS3 and aS1000) for the test beam. This was to confirm the agreement of the cine mode with the integrated mode, specifically for the test beam, which is an accepted mode of image acquisition for dosimetry with EPID. Third, in-phantom film and exit EPID dosimetry was performed on a moving platform using the same beam. Heterogeneous as well as homogeneous phantoms were used. The cine images were temporally sorted at 10% interval. The authors have performed dose reconstruction to the inphantom plane from the sorted cine images using the above validated method of dose reconstruction. The reconstructed dose from each cine image was summed to compose a total reconstructed dose from the test beam delivery, and was compared with film measurements. Results:The new method of dose reconstruction was validated showing greater than 95.3% pass rates of the gamma test with the criteria of dose difference of 3% and distance to agreement of 3 mm. The dose comparison of the reconstructed dose with the measured dose for the two phantoms showed pass rates higher than 96.4% given the same criteria. Conclusions: Feasibility of 4D dose reconstruction was successfully demonstrated in this study. The 4D dose reconstruction demonstrated in this study can be a promising dose validation method for radiation delivery on moving organs.

show abstract

“…In our prior study, we have developed and successfully demonstrated a method of dose reconstruction. [2][3][4] In this study, our objectives are (1) to develop a system of clinical application of reconstructed dose (above mentioned) that includes dose registration between fractions of treatment and dose-volume-histogram generation and (2) to demonstrate it on a deformable prostate phantom.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7] It assumes that the anatomical information (i.e. computer tomography or CT) of a patient under treatment is available and reconstructs "delivered" dose to such information from "transit" dose recorded in EPID.…”

Section: Introductionmentioning

confidence: 99%

Clinical Application of Dose Reconstruction Based on Full-Scope Monte Carlo Calculations: Composite Dose Reconstruction on a Deformed Phantom

Yeo

Chen

et al. 2014

Prog Med Phys

Self Cite

View full text Add to dashboard Cite

The purpose of this study was to develop a system of clinical application of reconstructed dose that includes dose reconstruction, reconstructed dose registration between fractions of treatment, and dose-volume-histogram generation and to demonstrate the system on a deformable prostate phantom. To achieve this purpose, a deformable prostate phantom was embedded into a 20 cm-deep and 40 cm-wide water phantom. The phantom was CT scanned and the anatomical models of prostate, seminal vesicles, and rectum were contoured. A coplanar 4-field intensity modulated radiation therapy (IMRT) plan was used for this study. Organ deformation was simulated by inserting a "transrectal" balloon containing 20 ml of water. A new CT scan was obtained and the deformed structures were contoured. Dose responses in phantoms and electronic portal imaging device (EPID) were calculated by using the XVMC Monte Carlo code. The IMRT plan was delivered to the two phantoms and integrated EPID images were respectively acquired. Dose reconstruction was performed on these images using the calculated responses. The deformed phantom was registered to the original phantom using an in-house developed software based on the Demons algorithm. The transfer matrix for each voxel was obtained and used to correlate the two sets of the reconstructed dose to generate a cumulative reconstructed dose on the original phantom. Forwardly calculated planning dose in the original phantom was compared to the cumulative reconstructed dose from EPID in the original phantom. The prescribed 200 cGy isodose lines showed little difference with respect to the "prostate" and "seminal vesicles", but appreciable difference (3%) was observed at the dose level greater than 210 cGy. In the rectum, the reconstructed dose showed lower volume coverage by a few percent than the plan dose in the dose range of 150 to 200 cGy. Through this study, the system of clinical application of reconstructed dose was successfully developed and demonstrated. The organ deformation simulated in this study resulted in small but observable dose changes in the target and critical structure.

show abstract

Fast transit portal dosimetry using density‐scaled layer modeling of aSi‐based electronic portal imaging device and Monte Carlo method

Abstract: The layer model of EPID built for Monte Carlo calculations offered fast (less than 1 min) and accurate calculation for transit dosimety and dose reconstruction.

Cited by 10 publications

References 37 publications

Two‐dimensional in vivo dose verification using portal imaging and correlation ratios

Two‐dimensional in vivo dose verification using portal imaging and correlation ratios

Feasibility study on inverse four‐dimensional dose reconstruction using the continuous dose‐image of EPID

Clinical Application of Dose Reconstruction Based on Full-Scope Monte Carlo Calculations: Composite Dose Reconstruction on a Deformed Phantom

Contact Info

Product

Resources

About