A Noninvasive Body Setup Method for Radiotherapy by Using a Multimodal Image Fusion Technique

Abstract

Purpose:To minimize the mismatch error between patient surface and immobilization system for tumor location by a noninvasive patient setup method.Materials and Methods:The method, based on a point set registration, proposes a shift for patient positioning by integrating information of the computed tomography scans and that of optical surface landmarks. An evaluation of the method included 3 areas: (1) a validation on a phantom by estimating 100 known mismatch errors between patient surface and immobilization system. (2) Five patients with pelvic tumors were considered. The tumor location errors of the method were measured using the difference between the proposal shift of cone-beam computed tomography and that of our method. (3) The collected setup data from the evaluation of patients were compared with the published performance data of other 2 similar systems.Results:The phantom verification results showed that the method was capable of estimating mismatch error between patient surface and immobilization system in a precision of <0.22 mm. For the pelvic tumor, the method had an average tumor location error of 1.303, 2.602, and 1.684 mm in left–right, anterior–posterior, and superior–inferior directions, respectively. The performance comparison with other 2 similar systems suggested that the method had a better positioning accuracy for pelvic tumor location.Conclusion:By effectively decreasing an interfraction uncertainty source (mismatch error between patient surface and immobilization system) in radiotherapy, the method can improve patient positioning precision for pelvic tumor.

A Noninvasive Method to Reduce Radiotherapy Positioning Error Caused by Respiration for Patients With Abdominal or Pelvic Cancers

“…As a result, surface deformation caused by respiration will lead to registration error that mainly consists of displacement in y and z directions as shown in Figure 4. Zhang’s previous study 10 showed an average final setup error of 1.30, 2.60, and 1.68 mm in x , y , and z directions, respectively. In comparison, our method exhibited a preferable accuracy in y and z directions, further indicating its effectiveness in reducing registration error caused by respiratory surface deformation.…”

“…17 The MBSI will cause error between tumor center and LINAC isocenter after initial setup. 10 As a result, another transformation matrix M 1 should be applied to further adjust the position of vacuum cushion. M 1 is represented as…”

“…7 -9 However, in clinical positioning practice, mismatch between patient surface and immobilization system (MBSI) is found to cause obvious interfraction setup error. 10…”

“…[7][8][9] However, in clinical positioning practice, mismatch between patient surface and immobilization system (MBSI) is found to cause obvious interfraction setup error. 10 On-board imaging devices such as cone-beam computed tomography (CBCT) and electronic portal imaging device (EPID) have been introduced as image-guided radiation therapy (IGRT) to improve radiotherapy setup precision. [11][12][13] X-ray images of patient internal anatomy are registered to the planning computed tomography (CT) scans to determine current positioning error.…”

Image Stitching in Smog Weather based on MSR and SURF

“…For example, the multi-resolution spline method is used to decompose images into a series of sub-band images with different resolutions, frequency features, and direction features, and then the weighted mean is calculated around the images overlapping boundary at each decomposed frequency domain. Finally, the composite images are stitched at all frequencies to form a complete image [14]. This method features higher computational complexity and higher fusion quality.…”