Dose calculation with a cone beam CT image in image-guided radiation therapy

Usui, Keisuke; Ichimaru, Yasunobu; Okumura, Yasuhiro; Murakami, K; Seo, Makoto; Kunieda, Etsuo; Ogawa, Kōichi

doi:10.1007/s12194-012-0176-z

Cited by 21 publications

(15 citation statements)

References 13 publications

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“…This calibration was led by a curve correlating the CT vs CBCT numbers within the same phantom tissues (similar to Refs. [5][6][7][8][9][10][11][12][13][14][15][16][17][18]. This curve, shown in Fig.…”

Section: C Geometric Evaluationmentioning

confidence: 85%

“…There is a rich literature on CBCT-based dose calculation using this method for phantoms and patient data for various treatment sites. [5][6][7][8][9][10][11][12][13][14][15][16][17][18] In this method, the relation between the average CBCT numbers for several regions of interest in a phantom with several material inserts, and the known electron density of the materials is examined. Using the obtained fit function, the CBCT numbers are replaced by the corresponding CT HU numbers in each voxel.…”

Section: Introductionmentioning

confidence: 99%

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Validation of a deformable image registration technique for cone beam CT‐based dose verification

et al. 2015

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Purpose: As radiation therapy evolves toward more adaptive techniques, image guidance plays an increasingly important role, not only in patient setup but also in monitoring the delivered dose and adapting the treatment to patient changes. This study aimed to validate a method for evaluation of delivered intensity modulated radiotherapy (IMRT) dose based on multimodal deformable image registration () for prostate treatments. Methods: A pelvic phantom was scanned with CT and cone-beam computed tomography (CBCT). Both images were digitally deformed using two realistic patient-based deformation fields. The original CT was then registered to the deformed CBCT resulting in a secondary deformed CT. The registration quality was assessed as the ability of the  method to recover the artificially induced deformations. The primary and secondary deformed CT images as well as vector fields were compared to evaluate the efficacy of the registration method and it's suitability to be used for dose calculation. , a free and open source software was used for deformable image registration. A B-spline algorithm with optimized parameters was used to achieve the best registration quality. Geometric image evaluation was performed through voxel-based Hounsfield unit (HU) and vector field comparison. For dosimetric evaluation, IMRT treatment plans were created and optimized on the original CT image and recomputed on the two warped images to be compared. The dose volume histograms were compared for the warped structures that were identical in both warped images. This procedure was repeated for the phantom with full, half full, and empty bladder. Results: The results indicated mean HU differences of up to 120 between registered and ground-truth deformed CT images. However, when the CBCT intensities were calibrated using a region of interest (ROI)-based calibration curve, these differences were reduced by up to 60%. Similarly, the mean differences in average vector field lengths decreased from 10.1 to 2.5 mm when CBCT was calibrated prior to registration. The results showed no dependence on the level of bladder filling. In comparison with the dose calculated on the primary deformed CT, differences in mean dose averaged over all organs were 0.2% and 3.9% for dose calculated on the secondary deformed CT with and without CBCT calibration, respectively, and 0.5% for dose calculated directly on the calibrated CBCT, for the full-bladder scenario. Gamma analysis for the distance to agreement of 2 mm and 2% of prescribed dose indicated a pass rate of 100% for both cases involving calibrated CBCT and on average 86% without CBCT calibration. Conclusions: Using deformable registration on the planning CT images to evaluate the IMRT dose based on daily CBCTs was found feasible. The proposed method will provide an accurate dose distribution using planning CT and pretreatment CBCT data, avoiding the additional uncertainties introduced by CBCT inhomogeneity and artifacts. This is a necessary initial step toward future imageguided adaptive ...

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Section: C Geometric Evaluationmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Validation of a deformable image registration technique for cone beam CT‐based dose verification

et al. 2015

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“…In this second test our method results were compared not only with those from a rigid-only registration of the vertebrae, which approximates our institution's current alignment protocol, but also with dose calculations directly on an calibrated and extended CBCT. 16,17…”

Section: C Evaluation Of the Dir Suitability For "Dose Of The Day"mentioning

confidence: 99%

“…We optimized a DIR algorithm implemented at our institution for CT-to-CBCT registrations in HN patients, and investigated its suitability to correctly estimate the "dose of the day" for an intensity modulated radiation therapy (IMRT) treatment. Two other common approaches suggested in the literature to calculate the "dose of the day" are based on image guidance with CT imaging, 15 and direct dose calculations on the CBCT, using pixel correction techniques 16,17 or relative electron density calibration. 18,19 The first increases the dose given to the patient in the image guidance protocols and requires an in-room CT scanner, which is not available in our practice.…”

Section: Introductionmentioning

confidence: 99%

Toward adaptive radiotherapy for head and neck patients: Feasibility study on using CT‐to‐CBCT deformable registration for “dose of the day” calculations

Veiga¹,

McClelland²,

Moinuddin³

et al. 2014

Medical Physics

197

220

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Deforming a planning CT to match a daily CBCT provides the tools needed for the calculation of the "dose of the day" without the need to acquire a new CT. The initial clinical application of our method will be weekly offline calculations of the "dose of the day," and use this information to inform adaptive radiotherapy (ART). The work here presented is a first step into a full implementation of a "dose-driven" online ART.

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“…Otsu's method initializes the cluster centers to ensure similar solution every time the function is run. Accurate hard segmentation of the final image is of interest for applications such as dose calculation [15], or estimating scatter convolution kernels in analytical reconstruction [16] etc. To achieve this, we propose a Bayesian framework [17] that may be used with prior spatial probabilistic maps for the final segmentation to be in consistent with expected craniofacial anatomy.…”

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confidence: 99%

A modified fuzzy C means algorithm for shading correction in craniofacial CBCT images

Ashfaq

Adler

2017

IFMBE Proceedings

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Abstract. CBCT images suffer from acute shading artifacts primarily due to scatter. Numerous image-domain correction algorithms have been proposed in the literature that use patient-specific planning CT images to estimate shading contributions in CBCT images. However, in the context of radiosurgery applications such as gamma knife, planning images are often acquired through MRI which impedes the use of polynomial fitting approaches for shading correction. We present a new shading correction approach that is independent of planning CT images. Our algorithm is based on the assumption that true CBCT images follow a uniform volumetric intensity distribution per material, and scatter perturbs this uniform texture by contributing cupping and shading artifacts in the image domain. The framework is a combination of fuzzy C-means coupled with a neighborhood regularization term and Otsu's method. Experimental results on artificially simulated craniofacial CBCT images are provided to demonstrate the effectiveness of our algorithm. Spatial non-uniformity is reduced from 16% to 7% in soft tissue and from 44% to 8% in bone regions. With shading-correction, thresholding based segmentation accuracy for bone pixels is improved from 85% to 91% when compared to thresholding without shading-correction. The proposed algorithm is thus practical and qualifies as a plug and play extension into any CBCT reconstruction software for shading correction.

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Dose calculation with a cone beam CT image in image-guided radiation therapy

Cited by 21 publications

References 13 publications

Validation of a deformable image registration technique for cone beam CT‐based dose verification

Validation of a deformable image registration technique for cone beam CT‐based dose verification

Toward adaptive radiotherapy for head and neck patients: Feasibility study on using CT‐to‐CBCT deformable registration for “dose of the day” calculations

A modified fuzzy C means algorithm for shading correction in craniofacial CBCT images

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