Multiscale registration of planning CT and daily cone beam CT images for adaptive radiation therapy

Abstract

Adaptive radiation therapy ͑ART͒ is the incorporation of daily images in the radiotherapy treatment process so that the treatment plan can be evaluated and modified to maximize the amount of radiation dose to the tumor while minimizing the amount of radiation delivered to healthy tissue. Registration of planning images with daily images is thus an important component of ART. In this article, the authors report their research on multiscale registration of planning computed tomography ͑CT͒ images with daily cone beam CT ͑CBCT͒ images. The multiscale algorithm is based on the hierarchical multiscale image decomposition of E. Tadmor, S. Nezzar, and L. Vese ͓Multiscale Model. Simul. 2͑4͒, pp. 554-579 ͑2004͔͒. Registration is achieved by decomposing the images to be registered into a series of scales using the ͑BV, L 2 ͒ decomposition and initially registering the coarsest scales of the image using a landmark-based registration algorithm. The resulting transformation is then used as a starting point to deformably register the next coarse scales with one another. This procedure is iterated at each stage using the transformation computed by the previous scale registration as the starting point for the current registration. The authors present the results of studies of rectum, head-neck, and prostate CT-CBCT registration, and validate their registration method quantitatively using synthetic results in which the exact transformations our known, and qualitatively using clinical deformations in which the exact results are not known.

Multiresolution Reconstruction for Cone-Beam Tomography from Raw Data Projections Using 3D Ridgelets

“…This can be directly applied to improve the acquisition in noisy conditions, case in which artifacts from any origin may be detected and removed at a low resolution so that the full reconstruction step can be avoided [24][25][26]. This is of particular interest in the group of pathologies associated with organs in constant movement, for example the lung or the heart.…”

Quantitative assessment of anatomical change using a virtual proton depth radiograph for adaptive head and neck proton therapy

“…Deformable image registration provides a means to register the simulation planning CT (pCT) to treatment fraction CBCT 5 , 6 , 7 . The deformed planning CT, which we refer to as the intensity‐corrected CBCT (cCBCT), is geometrically similar to the CBCT but with HUs that are well calibrated for WET calculations.…”

Deformable registration using edge‐preserving scale space for adaptive image‐guided radiation therapy

“…B‐spline–based registration algorithms are used for estimating the deformation fields as shown in Paquin et al, ( 5 ) where multiscale technique is used for efficiency. In Brock et al, ( 7 ) finite element model (FEM) is used for getting more accurate assessment of tumor response.…”

“…( 10 ) Radial basis functions and piecewise polynomials (splines) based methods are widely used for medical image registration in recent years. ( 5 , 10 , 12 ) Despite the significant progress which has been made in recent years, deformable registration algorithm for PCT and CBCT is still a hot research topic for clinical application and remains a challenging task. ( 5 , 13 ) …”

“…( 14 – 15 ) However, in addition to the high computational complexity of MI for 3D image, optimization process can always be trapped into local extremes when searching for the global optimum and, hence, result in misalignment. Although multiscale registration methods can improve the registration efficiency including speed, accuracy, and robustness, ( 5 , 16 ) Pluim et al ( 17 ) believed that one reason for misregistration in MI‐based registration is the absence of spatial information in MI measurement.…”