Dose Recalculation and the Dose-Guided Radiation Therapy (DGRT) Process Using Megavoltage Cone-Beam CT

Cheung, J; Aubry, Jean‐François; Yom, Sue S.; Gottschalk, Alexander; Celi, Juan Carlos; Pouliot, Jean

doi:10.1016/j.ijrobp.2008.12.034

Cited by 43 publications

(28 citation statements)

References 27 publications

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“…Thomas et al (13) utilized three densities — air, bone, and tissue. This study, and that of Langen et al (18) and Cheung et al, (16) used up to 16 densities. It is noted that although the measured CT–ED calibration curve for MV CBCT was shown in this and other studies to be a linear relationship, as expected theoretically, there are uncertainties which should be understood and may not be detected with a limited number of material densities.…”

Section: Discussionmentioning

confidence: 82%

“…However, a change in reconstruction kernel, size of the reconstruction matrix, and presence or absence of scattering material does alter the MV CBCT calibration. Recent publications utilizing MV CBCT for dose calculations assume a linear relationship (17) or present a linear relationship 13 , 16 that is utilized, but do not present the consistency of the linear relationship between different parameters.…”

Section: Discussionmentioning

confidence: 99%

“…Similarly, our study illustrates a correlation between the 5 and 60 MU calibrations of 0.999. Recent publications utilizing MV CBCT for dose calculations do not discuss differences in MU between the calibration curve and clinical or phantom images on which dose calculations are considered 13 , 16 , 17 . Morin et al, (19) however, have demonstrated a change in contrast to noise ratio, due to change in CT number, with changing MU.…”

Section: Discussionmentioning

confidence: 99%

“…To utilize MV CBCT images for optimization or adaption of treatment plans over the course of treatment, or in place of kV CT scans in the initial treatment planning process, 13 , 16 , 17 a reliable calibration between the pixel values (reconstructed gray‐scale values) within the reconstructed image and ED of the material being imaged is necessary. This is known as a MV CBCT ED calibration curve and is required, as it provides the treatment planning dose calculation algorithms with the required density information.…”

Section: Introductionmentioning

confidence: 99%

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An investigation into factors affecting electron density calibration for a megavoltage cone‐beam CT system

Hughes

Holloway

Quinn

et al. 2012

J Applied Clin Med Phys

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There is a growing interest in the use of megavoltage cone‐beam computed tomography (MV CBCT) data for radiotherapy treatment planning. To calculate accurate dose distributions, knowledge of the electron density (ED) of the tissues being irradiated is required. In the case of MV CBCT, it is necessary to determine a calibration‐relating CT number to ED, utilizing the photon beam produced for MV CBCT. A number of different parameters can affect this calibration. This study was undertaken on the Siemens MV CBCT system, MVision, to evaluate the effect of the following parameters on the reconstructed CT pixel value to ED calibration: the number of monitor units (MUs) used (5, 8, 15 and 60 MUs), the image reconstruction filter (head and neck, and pelvis), reconstruction matrix size (256 by 256 and 512 by 512), and the addition of extra solid water surrounding the ED phantom. A Gammex electron density CT phantom containing EDs from 0.292 to 1.707 was imaged under each of these conditions. The linear relationship between MV CBCT pixel value and ED was demonstrated for all MU settings and over the range of EDs. Changes in MU number did not dramatically alter the MV CBCT ED calibration. The use of different reconstruction filters was found to affect the MV CBCT ED calibration, as was the addition of solid water surrounding the phantom. Dose distributions from treatment plans calculated with simulated image data from a 15 MU head and neck reconstruction filter MV CBCT image and a MV CBCT ED calibration curve from the image data parameters and a 15 MU pelvis reconstruction filter showed small and clinically insignificant differences. Thus, the use of a single MV CBCT ED calibration curve is unlikely to result in any clinical differences. However, to ensure minimal uncertainties in dose reporting, MV CBCT ED calibration measurements could be carried out using parameter‐specific calibration measurements.PACS number: 87.59.bd

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An investigation into factors affecting electron density calibration for a megavoltage cone‐beam CT system

Hughes

Holloway

Quinn

et al. 2012

J Applied Clin Med Phys

View full text Add to dashboard Cite

show abstract

“…Ces modifications sont essentiellement attribuables à l'étalement du traitement sur sept semaines ainsi qu'à l'administration d'une chimiothérapie concomitante [4]. La précision de l'irradiation peut ainsi être affectée et des divergences entre la distribution de dose planifiée et celle délivrée peuvent conduire à des conséquences significatives pour les organes à risque et les volumes cibles [2,3,[5][6][7][8]. Pour corriger des incertitudes de positionnement avant l'irradiation, des techniques avancées de radiothérapie guidée par l'image (imageguided radiotherapy [IGRT]) ont été développées : tomographie conique de basse énergie (cone beam computed tomography [kV-CBCT]), tomographie conique de haute énergie (megavoltage cone beam computed tomography [MV-CBCT]), scanographie de basse énergie (low voltage computed tomography [kVCT]), scanographie de haute énergie (megavoltage computed tomography [MVCT]).…”

Section: Introductionunclassified

Radiothérapie adaptative des cancers ORL : un outil permettant d’identifier les patients nécessitant une adaptation de leur traitement

Huger¹,

Gräff²,

Marchesi³

et al. 2015

Cancer/Radiothérapie

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Effect of metal implants and metal artifacts on back‐projected two‐dimensional entrance fluence determined by EPID dosimetry

Cao

Gao

Liu

et al. 2023

J Applied Clin Med Phys

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PurposeTo evaluate the errors caused by metal implants and metal artifacts in the two‐dimensional entrance fluences reconstructed using the back‐projection algorithm based on electronic portal imaging device (EPID) images.MethodsThe EPID in the Varian VitalBeam accelerator was used to acquire portal dose images (PDIs), and then commercial EPID dosimetry software was employed to reconstruct the two‐dimensional entrance fluences based on computed tomography (CT) images of the head phantoms containing interchangeable metal‐free/titanium/aluminum round bars. The metal‐induced errors in the two‐dimensional entrance fluences were evaluated by comparing the γ results and the pixel value errors in the metal‐affected regions. We obtained metal‐artifact‐free CT images by replacing the voxel values of non‐metal inserts with those of metal inserts in metal‐free CT images to evaluate the metal‐artifact‐induced errors.ResultsThe γ passing rates (versus PDIs obtained without a phantom in the beam field (PDIair), 2%/2 mm) for the back‐projected two‐dimensional entrance fluences of phantoms containing titanium or aluminum (BPTi/BPAl) were reduced from 92.4% to 90.5% and 90.6%, respectively, relative to the metal‐free phantom (BPmetal‐free). Titanium causes more severe metal artifacts in CT images than aluminum, and its removal resulted in a 0.0022 CU (median) reduction in the pixel value of BPTi artifact‐free relative to BPTi in the metal‐affected region. Moreover, the mean absolute error (MAE) and root mean square error (RMSE) decreased from 0.0050 CU and 0.0063 CU to 0.0034 CU and 0.0040 CU, respectively (vs. BPmetal‐free).ConclusionMetal implants increase the errors in back‐projected two‐dimensional entrance fluences, and metals with higher electron densities cause more errors. For high‐electron‐density metal implants that produce severe metal artifacts (e.g., titanium), removing metal artifacts from the CT images can improve the accuracy of the two‐dimensional entrance fluences reconstructed by back‐projection algorithms.

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Dose Recalculation and the Dose-Guided Radiation Therapy (DGRT) Process Using Megavoltage Cone-Beam CT

Cited by 43 publications

References 27 publications

An investigation into factors affecting electron density calibration for a megavoltage cone‐beam CT system

An investigation into factors affecting electron density calibration for a megavoltage cone‐beam CT system

Radiothérapie adaptative des cancers ORL : un outil permettant d’identifier les patients nécessitant une adaptation de leur traitement

Effect of metal implants and metal artifacts on back‐projected two‐dimensional entrance fluence determined by EPID dosimetry

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