This paper presents a comprehensive metrological analysis of the Microsoft Kinect motion sensor performed using a proprietary flat marker. The designed marker was used to estimate its position in the external coordinate system associated with the sensor. The study includes calibration of the RGB and IR cameras, parameter identification and image registration. The metrological analysis is based on the data corrected for sensor optical distortions. From the metrological point of view, localization errors are related to the distance of an object from the sensor. Therefore, the rotation angles were determined and an accuracy assessment of the depth maps was performed. The analysis was carried out for the distances from the marker in the range of 0.8−1.65 m. The maximum average error was equal to 23 mm for the distance of 1.6 m.
Cardiovascular system diseases are the major causes of mortality in the world. The most important and widely used tool for assessing the heart state is echocardiography (also abbreviated as ECHO). ECHO images are used e.g. for location of any damage of heart tissues, in calculation of cardiac tissue displacement at any arbitrary point and to derive useful heart parameters like size and shape, cardiac output, ejection fraction, pumping capacity. In this paper, a robust algorithm for heart shape estimation (segmentation) in ECHO images is proposed. It is based on the recently introduced variant of the level set method called level set without edges. This variant takes advantage of the intensity value of area information instead of module of gradient which is typically used. Such approach guarantees stability and correctness of algorithm working on the border between object and background with small absolute value of image gradient. To reassure meaningful results, the image segmentation is proceeded with automatic Region of Interest (ROI) calculation. The main idea of ROI calculations is to receive a triangle-like part of the acquired ECHO image, using linear Hough transform, thresholding and simple mathematics. Additionally, in order to improve the images quality, an anisotropic diffusion filter, before ROI calculation, was used. The proposed method has been tested on real echocardiographic image sequences. Derived results confirm the effectiveness of the presented method.
With development of medical diagnostic and imaging techniques the sparing surgeries are facilitated. Renal cancer is one of examples. In order to minimize the amount of healthy kidney removed during the treatment procedure, it is essential to design a system that provides three-dimensional visualization prior to the surgery. The information about location of crucial structures (e.g. kidney, renal ureter and arteries) and their mutual spatial arrangement should be delivered to the operator. The introduction of such a system meets both the requirements and expectations of oncological surgeons. In this paper, we present one of the most important steps towards building such a system: a new approach to kidney segmentation from Computed Tomography data. The segmentation is based on the Active Contour Method using the Level Set (LS) framework. During the segmentation process the energy functional describing an image is the subject to minimize. The functional proposed in this paper consists of four terms. In contrast to the original approach containing solely the region and boundary terms, the ellipsoidal shape constraint was also introduced. This additional limitation imposed on evolution of the function prevents from leakage to undesired regions. The proposed methodology was tested on 10 Computed Tomography scans from patients diagnosed with renal cancer. The database contained the results of studies performed in several medical centers and on different devices. The average effectiveness of the proposed solution regarding the Dice Coefficient and average Hausdorff distance was equal to 0.862 and 2.37 mm, respectively. Both the qualitative and quantitative evaluations confirm effectiveness of the proposed solution.
Minimally invasive procedures for the kidney tumour removal require a 3D visualization of topological relations between kidney, cancer, the pelvicalyceal system and the renal vascular tree. In this paper, a novel methodology of the pelvicalyceal system segmentation is presented. It consists of four following steps: ROI designation, automatic threshold calculation for binarization (approximation of the histogram image data with three exponential functions), automatic extraction of the pelvicalyceal system parts and segmentation by the Locally Adaptive Region Growing algorithm. The proposed method was applied successfully on the Computed Tomography database consisting of 48 kidneys both healthy and cancer affected. The quantitative evaluation (comparison to manual segmentation) and visual assessment proved its effectiveness. The Dice Coefficient of Similarity is equal to 0.871 ± 0.060 and the average Hausdorff distance 0.46 ± 0.36 mm. Additionally, to provide a reliable assessment of the proposed method, it was compared with three other methods. The proposed method is robust regardless of the image acquisition mode, spatial resolution and range of image values. The same framework may be applied to further medical applications beyond preoperative planning for partial nephrectomy enabling to visually assess and to measure the pelvicalyceal system by medical doctors.
The paper presents an analysis of factors influencing the accuracy of reproduction of geometry of the vertebrae and the intervertebral disc of the lumbar motion segment for the purpose of designing of an intervertebral disc endoprosthesis. In order to increase the functionality of the new type of endoprostheses by a better adjustment of their structure to the patient’s anatomical features, specialist software was used allowing the processing of the projections of the diagnosed structures. Recommended minimum values of projection features were determined in order to ensure an effective processing of the scanned structures as well as other factors affecting the quality of the reproduction of 3D model geometries. Also, there were generated 3D models of the L4-L5 section. For the final development of geometric models for disc and vertebrae L4 and L5 there has been used smoothing procedure by cubic free curves with the NURBS technique. This allows accurate reproduction of the geometry for the purposes of identification of a spatial shape of the surface of the vertebrae and the vertebral disc and use of the model for designing of a new endoprosthesis, as well as conducting strength tests with the use of finite elements method.
I n t r o d u c t i o n: Co-occurrence of physical and cognitive dysfunctions contribute to functional decline and a gradual loss of independence. O b j e c t i v e s: The purpose of this study was to evaluate the association between global cognitive impairment and physical mobility in older adults with and without mild cognitive impairment (MCI). Ma t e r i a l a n d Me t h o d s: A total of 800 older adults were recruited (653 with normal cognitive functioning and 147 participants with MCI). Motor performance was measured with the Timed Up and Go test (TUG) and the 6 Minute Walk Test (6MWT). Cognitive functions were evaluated using Mini- Mental State Examination (MMSE) and Addenbrooke’s Cognitive Examination (ACE-III). R e s u l t s: ACE-III scores were associated with the TUG test performance in older adults (with and without MCI), but not with 6MWT results. The overall score in ACE-III and its subscales, i.e. a) memory and fluency in the MCI group and in the total group, and b) fluency in the control group, were associated with TUG aft er adjusting for age, sex, body mass index, medication use, depressive symptoms, hypertension, coronary artery disease and diabetes. In the case of the 6MWT test results, only the ACE-III fluency subscale scores and not the overall ACE-III score were associated with them. C o n c l u s i o n s: Global cognitive function, verbal fluency and memory were independently associated with the TUG. ACE-III, being a more extensive testing tool than MMSE, made it possible to show the relationship between global cognition and motor skills.