Distance‐preserving rigidity penalty on deformable image registration of multiple skeletal components in the neck

Biomed. Phys. Eng. Express

Janssens

Baudier

et al. 2017

A comprehensive evaluation of the accuracy of CBCT and deformable registration based dose calculation 4 in lung proton therapy 5 The uncertainties in water equivalent thickness (WET) and accuracy of dose estimation using a virtual CT 30 (vCT), generated from deforming the planning CT (pCT) onto the daily cone-beam CT (CBCT), were 31 comprehensively evaluated in the context of lung malignancies and passive scattering proton therapy. The 32 validation methodology utilized multiple CBCT datasets to generate the vCTs of twenty lung cancer 33 patients. A correction step was applied to the vCTs to account for anatomical modifications that could not 34 be modeled by deformation alone. The CBCT datasets included a regular CBCT (rCBCT) and synthetic 35CBCTs created from the rCBCT and rescan CT (rCT), which minimized the variation in setup between the 36 vCT and the gold-standard image (i.e., rCT). The uncertainty in WET was defined as the voxelwise 37 2 difference in WET between vCT and rCT, and calculated in 3D (planning target volume, PTV) and 2D 1 (distal and proximal surfaces). The uncertainty in WET based dose warping was defined as the difference 2 between the warped dose and a forward dose recalculation on the rCT. The overall root mean square (RMS) 3 uncertainty in WET was 3.6±1.8, 2.2±1.4 and 3.3±1.8 mm for the distal surface, proximal surface and PTV, 4 respectively. For the warped dose, the RMS uncertainty of the voxelwise dose difference was 6±2% of the 5 maximum dose (%mD), using a 20% cut-off. The rCBCT resulted in higher uncertainties due to setup 6 variability with the rCT; the uncertainties reported with the two synthetic CBCTs were similar. The vCT 7 followed by a correction step was found to be an accurate alternative to rCT.

Section: Discussionmentioning

confidence: 99%

A comprehensive evaluation of the accuracy of CBCT and deformable registration based dose calculation in lung proton therapy

Biomed. Phys. Eng. Express

Janssens

Baudier

et al. 2017

“…Even though we used the state-of-art registration algorithm available in NiftyReg, that is a general-purpose algorithm designed to be applicable to a wide range of medical images from different modalities and on different parts of the anatomy. General-purpose algorithms can be made more realistic by incorporating additional constraints (eg, to avoid bone deformation [31]). Alternatively, algorithms specifically designed for the treatment site could be used, such as biomechanical-based algorithms that model the physical properties of the tissues being registered [32,33].…”

Section: Discussionmentioning

confidence: 99%

Cone-Beam Computed Tomography and Deformable Registration-Based “Dose of the Day” Calculations for Adaptive Proton Therapy

International Journal of Particle Therapy

Alshaikhi

Amos

et al. 2015

Purpose: The aim of this work was to evaluate the feasibility of cone-beam computed tomography (CBCT) and deformable image registration (DIR)-based ''dose of the day'' calculations for adaptive proton therapy. Methods: Intensity-modulated radiation therapy (IMRT) and proton therapy plans were designed for 3 head and neck patients that required replanning, and hence had a replan computed tomography (CT). Proton plans were generated for different beam arrangements and optimizations: intensity modulated proton therapy and single-field uniform dose. We used an in-house DIR software implemented at our institution to generate a deformed CT, by warping the planning CT onto the daily CBCT. This CBCT had a similar patient geometry to the replanned CT. Dose distributions on the replanned CT were considered the gold standard for ''dose of the day'' calculations, and were compared with doses on deformed CT (our method) and directly on the calibrated CBCT and rigidly aligned planning CT (alternative methods) in terms of dose difference (DD), by calculating the percentage of voxels whose DD was smaller than 2% of the prescribed dose (DD 2%-pp) and the root mean square of the DD distribution (DD RMS). Results: Using a deformed CT, the DD 2%-pp within the CBCT imaging volume was 93.2% 6 0.7% for IMRT, and 87% 6 3% for proton plans. In a region of higher dose gradient, we found that although DD 2%-pp was 94.3% 6 0.2% for IMRT, in proton plans, it dropped to 74% 6 4%. A larger number of treatment beams and single-field uniform dose optimization appear to make the proton plans less sensitive to DIR errors. For example, within the treated volume, the DD RMS was reduced from 2.6% 6 0.6% of the prescribed dose to 1.0% 6 1.3% of the prescribed dose when using single-field uniform dose optimization. Conclusions: Promising results were found for DIR-and CBCT-based proton dose calculations. Proton dose calculations were, however, more sensitive to registration errors than IMRT doses were, particularly in high dose gradient regions.

“…Examples include incorporating missing tissue in image registration by modifying existent DIR algorithms 43 and further regularizing the transformation to avoid deformation of bony anatomy. 44 However, there is still a very long way to go to achieve truly realistic DIR, and indeed, this will not just involve developing new algorithms and computational techniques but will also require a better understanding of the actual physical and biological processes that occur during a course of radiotherapy.…”

Section: Oarmentioning

confidence: 99%

Toward adaptive radiotherapy for head and neck patients: Uncertainties in dose warping due to the choice of deformable registration algorithm

Lourenço²,

Mouinuddin

et al. 2015

Medical Physics