Relationship between spatial ability, visuospatial working memory and self-assessed spatial orientation ability: a study in older adults

This paper describes some novel spatial tasks and questionnaires designed to assess spatial and orientation abilities. The new tasks and questionnaires were administered to a sample of 90 older adults (41 males, age range 57–90), along with some other tests of spatial ability (Minnesota Paper Form Board, Mental Rotations Test, and Embedded Figures Test) and tests of visuospatial working memory (Corsi’s Block Test and Visual Pattern Test). The internal reliability of the new tasks and questionnaires was analyzed, as well as their relationship with the spatial and working memory tests. The results showed that the new spatial tasks are reliable, correlate with working memory and spatial ability tests and, compared with the latters, show stronger correlations with the self-report questionnaires referring to orientation abilities. A model was also tested (with reference to Allen et al. in Intelligence 22:327–355, 1996) in which the new tasks were assumed to relate to spatial ability and predict orientation abilities as assessed by the self-report measures

Direction dependent B-splines decomposition for the registration of sliding objects

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Registration of sliding objects using direction dependent B-splines decomposition

International audienceSliding motion is a challenge for deformable image registration because it leads to discontinuities in the sought deformation. In this paper, we present a method to handle sliding motion using multiple B-spline transforms. The proposed method decomposes the sought deformation into sliding regions to allow discontinuities at their interfaces, but prevents unrealistic solutions by forcing those interfaces to match. The method was evaluated on 16 lung cancer patients against a single B-spline transform approach and a multi B-spline transforms approach without the sliding constraint at the interface. The target registration error (TRE) was significantly lower with the proposed method (TRE = 1.5 mm) than with the single B-spline approach (TRE = 3.7 mm) and was comparable to the multi B-spline approach without the sliding constraint (TRE = 1.4 mm). The proposed method was also more accurate along region interfaces, with 37% less gaps and overlaps when compared to the multi B-spline transforms without the sliding constraint

2D/4D marker-free tumor tracking using 4D CBCT as the reference image

International audienceTumor motion caused by respiration is an important issue in image-guided radiotherapy. A 2D/4D matching method between 4D volumes derived from cone beam computed tomography (CBCT) and 2D fluoroscopic images was implemented to track the tumor motion without the use of implanted markers. In this method, firstly, 3DCBCT and phase-rebinned 4DCBCT are reconstructed from cone beam acquisition. Secondly, 4DCBCT volumes and a streak-free 3DCBCT volume are combined to improve the image quality of the digitally reconstructed radiographs (DRRs). Finally, the 2D/4D matching problem is converted into a 2D/2D matching between incoming projections and DRR images from each phase of the 4DCBCT. The diaphragm is used as a target surrogate for matching instead of using the tumor position directly. This relies on the assumption that if a patient has the same breathing phase and diaphragm position as the reference 4DCBCT, then the tumor position is the same. From the matching results, the phase information, diaphragm position and tumor position at the time of each incoming projection acquisition can be derived. The accuracy of this method was verified using 16 candidate datasets, representing lung and liver applications and one-minute and two-minute acquisitions. The criteria for the eligibility of datasets were described: 11 eligible datasets were selected to verify the accuracy of diaphragm tracking, and one eligible dataset was chosen to verify the accuracy of tumor tracking. The diaphragm matching accuracy was 1.88 ± 1.35 mm in the isocenter plane and the 2D tumor tracking accuracy was 2.13 ± 1.26 mm in the isocenter plane. These features make this method feasible for real-time marker-free tumor motion tracking purposes

Keuhkot: a method for lung segmentation

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Open source tools for validation of deformable registration

International audienceDeformable image registration is of considerable interest to the radiation therapy community. It is considered a key enabling technology for applications such as adaptive radiotherapy, contour propagation in 4D CT images, atlas-based segmentation, breathing motion modeling, dose accumulation and many more. Deformable registration is slowly finding its way to commercial software packages. However, validation of the estimated deformation fields remains challenging because no ground truth is available. In general, validation of deformable registration relies on manually generated data, often in the form of hand-clicked landmarks or handdrawn contours. Obtaining such data is a laborious and time-consuming task. Strictly speaking, the resulting validation should be considered as partial, due to the high number of degrees of freedom of the system. In addition, the ill-posed nature of the problem implies the procedure needs to be repeated when dealing with images of different quality, nature or modality. Open-source and open-data concepts constitute an approach where source code and data are provided for free usage, within the limits of a defined agreement, and with a strong concern on users' feedback and participation. It has proved to be an efficient strategy to accelerate scientific advances in a difficult field, based on distributed and collaborative effort, in particular by enabling evaluation and comparison. Many initiatives exist for the application of validating deformable registration, several of which have had a considerable impact in the field. In this presentation, we will describe some open-source and open-data tools that have been proposed and used for validation of deformable image registration. We will review some freely available image processing toolkits (e.g. ITK, elastix), publicly accessible databases of annotated images (e.g. Dir-Lab, POPI), visualization freeware (e.g. VTK, Osirix, VV) and implementation contests or challenges (EMPIRE10). Advantages and limitations of each will also be discussed