The basal forebrain degenerates in Alzheimer's disease (AD) and this process is believed to contribute to the cognitive decline observed in AD patients. Impairment in spatial navigation is an early feature of the disease but whether basal forebrain dysfunction in AD is responsible for the impaired navigation skills of AD patients is not known. Our objective was to investigate the relationship between basal forebrain volume and performance in real space as well as computer-based navigation paradigms in an elderly cohort comprising cognitively normal controls, subjects with amnestic mild cognitive impairment and those with AD. We also tested whether basal forebrain volume could predict the participants' ability to perform allocentric- vs. egocentric-based navigation tasks. The basal forebrain volume was calculated from 1.5 T magnetic resonance imaging (MRI) scans, and navigation skills were assessed using the human analog of the Morris water maze employing allocentric, egocentric, and mixed allo/egocentric real space as well as computerized tests. When considering the entire sample, we found that basal forebrain volume correlated with spatial accuracy in allocentric (cued) and mixed allo/egocentric navigation tasks but not the egocentric (uncued) task, demonstrating an important role of the basal forebrain in mediating cue-based spatial navigation capacity. Regression analysis revealed that, although hippocampal volume reflected navigation performance across the entire sample, basal forebrain volume contributed to mixed allo/egocentric navigation performance in the AD group, whereas hippocampal volume did not. This suggests that atrophy of the basal forebrain contributes to aspects of navigation impairment in AD that are independent of hippocampal atrophy.

• Keywords
• Alzheimer’s disease, MRI, basal forebrain, cognitive impairment, navigation,
• Publication type
• Journal Article MeSH

Impairment in spatial navigation (SN) and structural network topology is not limited to patients with Alzheimer's disease (AD) dementia and can be detected earlier in patients with mild cognitive impairment (MCI). We recruited 32 MCI patients (65.91 ± 11.33 years old) and 28 normal cognition patients (NC; 69.68 ± 10.79 years old), all of whom underwent a computer-based battery of SN tests evaluating egocentric, allocentric, and mixed SN strategies and diffusion-weighted and T1-weighted Magnetic Resonance Imaging (MRI). To evaluate the topological features of the structural connectivity network, we calculated its measures such as the global efficiency, local efficiency, clustering coefficient, and shortest path length with GRETNA. We determined the correlation between SN accuracy and network topological properties. Compared to NC, MCI subjects demonstrated a lower egocentric navigation accuracy. Compared with NC, MCI subjects showed significantly decreased clustering coefficients in the left middle frontal gyrus, right rectus, right superior parietal gyrus, and right inferior parietal gyrus and decreased shortest path length in the left paracentral lobule. We observed significant positive correlations of the shortest path length in the left paracentral lobule with both the mixed allocentric-egocentric and the allocentric accuracy measured by the average total errors. A decreased clustering coefficient in the right inferior parietal gyrus was associated with a larger allocentric navigation error. White matter hyperintensities (WMH) did not affect the correlation between network properties and SN accuracy. This study demonstrated that structural connectivity network abnormalities, especially in the frontal and parietal gyri, are associated with a lower SN accuracy, independently of WMH, providing a new insight into the brain mechanisms associated with SN impairment in MCI.

• Keywords
• clustering coefficient, graph theory, mild cognitive impairment, network topology, spatial navigation,
• Publication type
• Journal Article MeSH

The performance of deep neural networks and the low costs of computational hardware has made computer vision a popular choice in many robotic systems. An attractive feature of deep-learned methods is their ability to cope with appearance changes caused by day-night cycles and seasonal variations. However, deep learning of neural networks typically relies on large numbers of hand-annotated images, which requires significant effort for data collection and annotation. We present a method that allows autonomous, self-supervised training of a neural network in visual teach-and-repeat (VT&R) tasks, where a mobile robot has to traverse a previously taught path repeatedly. Our method is based on a fusion of two image registration schemes: one based on a Siamese neural network and another on point-feature matching. As the robot traverses the taught paths, it uses the results of feature-based matching to train the neural network, which, in turn, provides coarse registration estimates to the feature matcher. We show that as the neural network gets trained, the accuracy and robustness of the navigation increases, making the robot capable of dealing with significant changes in the environment. This method can significantly reduce the data annotation efforts when designing new robotic systems or introducing robots into new environments. Moreover, the method provides annotated datasets that can be deployed in other navigation systems. To promote the reproducibility of the research presented herein, we provide our datasets, codes and trained models online.

• Keywords
• artificial neural network, computer vision, deep learning, long-term autonomy, mobile robot, self-supervised machine learning, visual teach and repeat navigation,
• MeSH
• Data Curation MeSH
• Neural Networks, Computer * MeSH
• Reproducibility of Results MeSH
• Hand * MeSH
• Research Design MeSH
• Publication type
• Journal Article MeSH

Cognitive deficits in older adults attributable to Alzheimer's disease (AD) pathology are featured early on by hippocampal impairment. Among these individuals, deterioration in spatial navigation, manifested by poor hippocampus-dependent allocentric navigation, may occur well before the clinical onset of dementia. Our aim was to determine whether allocentric spatial navigation impairment would be proportional to right hippocampal volume loss irrespective of general brain atrophy. We also contrasted the respective spatial navigation scores of the real-space human Morris water maze with its corresponding 2D computer version. We included 42 cognitively impaired patients with either amnestic mild cognitive impairment (n = 23) or mild and moderate AD (n = 19), and 14 cognitively intact older controls. All participants underwent 1.5T MRI brain scanning with subsequent automatic measurement of the total brain and hippocampal (right and left) volumes. Allocentric spatial navigation was tested in the real-space version of the human Morris water maze and in its corresponding computer version. Participants used two navigational cues to locate an invisible goal independent of the start position. We found that smaller right hippocampal volume was associated with poorer navigation performance in both the real-space (β = -0.62, P < 0.001) and virtual (β = -0.43, P = 0.026) versions, controlling for demographic variables, total brain and left hippocampal volumes. In subsequent analyses, the results were significant in cognitively impaired (P ≤ 0.05) but not in cognitively healthy (P > 0.59) subjects. The respective real-space and virtual scores strongly correlated with each other. Our findings indicate that the right hippocampus plays a critical role in allocentric navigation, particularly when cognitive impairment is present.

• MeSH
• Hippocampus anatomy & histology   pathology   MeSH
• Humans MeSH
• Magnetic Resonance Imaging MeSH
• Case-Control Studies MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Computer-assisted orthopedic surgery (CAOS) systems have become one of the most important and challenging types of system in clinical orthopedics, as they enable precise treatment of musculoskeletal diseases, employing modern clinical navigation systems and surgical tools. This paper brings a comprehensive review of recent trends and possibilities of CAOS systems. There are three types of the surgical planning systems, including: systems based on the volumetric images (computer tomography (CT), magnetic resonance imaging (MRI) or ultrasound images), further systems utilize either 2D or 3D fluoroscopic images, and the last one utilizes the kinetic information about the joints and morphological information about the target bones. This complex review is focused on three fundamental aspects of CAOS systems: their essential components, types of CAOS systems, and mechanical tools used in CAOS systems. In this review, we also outline the possibilities for using ultrasound computer-assisted orthopedic surgery (UCAOS) systems as an alternative to conventionally used CAOS systems.

• Keywords
• CAOS, fluoroscopic navigation, image-based navigation, imageless navigation, medical image processing,
• MeSH
• Surgery, Computer-Assisted trends   MeSH
• Humans MeSH
• Musculoskeletal Diseases physiopathology   surgery   MeSH
• Orthopedic Procedures trends   MeSH
• Tomography, X-Ray Computed trends   MeSH
• Robotics trends   MeSH
• Imaging, Three-Dimensional trends   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH

PURPOSE: Innovative intraoperative imaging modalities open new horizons to more precise image acquisition and possibly to better results of spinal navigation. Planning of screw entry points and trajectories in this prospective study had been based on intraoperative imaging obtained by a portable 32-slice CT scanner. The authors evaluated accuracy and safety of this novel approach in the initial series of 18 instrumented surgeries in anatomically complex segment of cervico-thoracic junction. METHODS: We report on the single-institution results of assessment of anatomical accuracy of C5-T3 pedicle screw insertion as well as its clinical safety. The evaluation of total radiation dose and of time demands was secondary endpoint of the study. RESULTS: Out of 129 pedicle screws inserted in the segment of C5-T3, only 5 screws (3.9 %) did not meet the criteria for correct implant positioning. These screw misplacements had not been complicated by neural, vascular or visceral injury and surgeon was not forced to change the position intraoperatively or during the postoperative period. Quality of intraoperative CT imaging sufficient for navigation was obtained at all spinal segments regardless of patient´s habitus, positioning or comorbidity. A higher radiation exposition of the patient and 27 min longer operative time are consequences of this technique. CONCLUSIONS: The intraoperative portable CT scanner-based spinal navigation is a reliable and safe method of pedicle screw insertion in cervico-thoracic junction.

• Keywords
• Cervical and thoracic vertebrae, Computer tomography, Intraoperative imaging, Pedicle screw, Spinal instrumentation,
• MeSH
• Surgery, Computer-Assisted methods   MeSH
• Thoracic Vertebrae * diagnostic imaging   surgery   MeSH
• Cervical Vertebrae * diagnostic imaging   surgery   MeSH
• Humans MeSH
• Orthopedic Procedures instrumentation   methods   MeSH
• Pedicle Screws * MeSH
• Tomography, X-Ray Computed methods   MeSH
• Prospective Studies MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH

Lacunar cerebral infarction (LI) is one of risk factors of vascular dementia and correlates with progression of cognitive impairment including the executive functions. However, little is known on spatial navigation impairment and its underlying microstructural alteration of white matter in patients with LI and with or without mild cognitive impairment (MCI). Our aim was to investigate whether the spatial navigation impairment correlated with the white matter integrity in LI patients with MCI (LI-MCI). Thirty patients with LI were included in the study and were divided into LI-MCI (n=17) and non MCI (LI-Non MCI) groups (n=13) according neuropsychological tests.The microstructural integrity of white matter was assessed by calculating a fractional anisotropy (FA) and mean diffusivity (MD) from diffusion tensor imaging (DTI) scans. The spatial navigation accuracy, separately evaluated as egocentric and allocentric, was assessed by a computerized human analogue of the Morris Water Maze tests Amunet. LI-MCI performed worse than the CN and LI-NonMCI groups on egocentric and delayed spatial navigation subtests. LI-MCI patients have spatial navigation deficits. The microstructural abnormalities in diffuse brain regions, including hippocampus, uncinate fasciculus and other brain regions may contribute to the spatial navigation impairment in LI-MCI patients at follow-up.

• Keywords
• Gerotarget, diffusion tensor imaging, lacunar infarction, mild cognitive impairment, spatial navigation,
• MeSH
• Anisotropy MeSH
• White Matter diagnostic imaging   physiopathology   MeSH
• Diffusion Magnetic Resonance Imaging * MeSH
• Cognition * MeSH
• Cognitive Dysfunction diagnostic imaging   physiopathology   psychology   MeSH
• Stroke, Lacunar diagnostic imaging   physiopathology   psychology   MeSH
• Middle Aged MeSH
• Humans MeSH
• Neuropsychological Tests MeSH
• Spatial Behavior * MeSH
• Aged MeSH
• Case-Control Studies MeSH
• Space Perception * MeSH
• Diffusion Tensor Imaging * MeSH
• Check Tag
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH

OBJECTIVES: The aim of this study was to investigate the long-term effects of computer-assisted Ci™ navigation on clinical, radiological, and functional results versus conventional total knee arthroplasty (TKA). PATIENTS AND METHODS: Between January 2005 and July 2011, a total of 85 patients (36 males, 49 females; mean age: 66.2±5.2 years; range, 59 to 84 years) who underwent P.F.C. Sigma™ knee system implantation using computer-assisted Ci™ navigation system (BrainLAB®, DePuy International, Leeds, UK) and completed a minimum follow-up of eight years were included in the study. In the control group, a total of 100 patients (40 males, 60 females; mean age: 68.3±3.9 years; range, 60 to 79 years) who completed a minimum follow-up of eight years were randomly selected from a dataset of implanted P.F.C. Sigma™ knee systems in the same period using Specialist® 2 instrumentation without navigation. An implant survival analysis was used to compare implant survivorship between the groups throughout 12 years. The Knee Society Score (KSS) and range of motion (ROM) were assessed. Based on long-format X-ray images, the implant position in the frontal and sagittal planes was evaluated. RESULTS: The ratio for navigation to control group survival is approximately 1.01 at 12 years. The clinical outcomes showed no significant difference between the groups (knee scores, p=0.707 and functional scores, p=0.485). In the measured angles analysis, we observed a consistent pattern in both groups. In the control group, there was a trend toward implanting the tibial component with slight varus alignment (p=0.038) and a higher posterior slope (p<0.001). On average, the operation was prolonged by 13 min in the navigated group (p<0.001). CONCLUSION: In conclusion, our study results demonstrate that while kinematic navigation in TKA improves the precision of implant alignment, it does not provide significant benefits in terms of long-term implant survival or functional outcomes compared to conventional TKA methods. The use of the computer-assisted Ci™ navigation system is associated with prolonged operation duration, although no technical complications related to the navigation device's software can be observed. Therefore, although navigation offers theoretical advantages in component positioning, its use may be more justifiable in cases with challenging alignment requirements rather than as a routine practice.

• MeSH
• Osteoarthritis, Knee * surgery   physiopathology   diagnostic imaging   MeSH
• Time Factors MeSH
• Surgery, Computer-Assisted * adverse effects   methods   instrumentation   MeSH
• Knee Joint * surgery   diagnostic imaging   physiopathology   MeSH
• Middle Aged MeSH
• Humans MeSH
• Follow-Up Studies MeSH
• Recovery of Function MeSH
• Knee Prosthesis MeSH
• Retrospective Studies MeSH
• Range of Motion, Articular MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Arthroplasty, Replacement, Knee * methods   instrumentation   adverse effects   MeSH
• Treatment Outcome MeSH
• Check Tag
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Comparative Study MeSH

BACKGROUND: Navigation based on an intraoperative CT scan is not a new approach to spinal instrumentation. Innovative intraoperative imaging technology, however, opens new horizons to more precise image acquisition as well as to further workflow. Planning of screw entry-points and trajectories in this study had been based on intraoperative imaging obtained by a portable 32-slice CT scanner. This prospective study evaluates feasibility, accuracy, and safety of this novel approach in an initial series of 85 surgeries. METHOD: Medical records and radiological materials of 82 patients who underwent the first 85 consecutive stabilisations were analysed. Incorrect screw position, medical and technical complications as well as availability of this procedure in particular spinal levels were the subject of evaluation. RESULTS: Out of 571 implants inserted in all spinal levels, only five screws (0.87 %) did not meet the criteria for correct implant position. These screw misplacements had not been complicated by neural, vascular or visceral injury and the surgeon was not forced to change the position intraoperatively or during the postoperative period. The quality of intraoperative CT imaging sufficient for navigation was obtained at all spinal segments regardless of a patient's habitus or positioning or comorbidity. CONCLUSION: Intraoperative portable CT scanner-based navigation seems to be an effective way of doing spinal instrumentation guidance. High precision of implant insertion confirms the preconditions of navigation usage during more complex surgeries at any level of the spine.

• MeSH
• Lumbar Vertebrae surgery   MeSH
• Equipment Design MeSH
• Adult MeSH
• Spinal Fusion instrumentation   MeSH
• Thoracic Vertebrae surgery   MeSH
• Cervical Vertebrae surgery   MeSH
• Sacrum surgery   MeSH
• Middle Aged MeSH
• Humans MeSH
• Neuronavigation instrumentation   MeSH
• Pedicle Screws * MeSH
• Tomography, X-Ray Computed instrumentation   MeSH
• Prospective Studies MeSH
• Aged MeSH
• Feasibility Studies MeSH
• Point-of-Care Systems * MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH

Thermal ablation is a well-known method used in interventional radiology to treat cancer. The treatment success is closely related to the exact catheter location in the treated area. Current navigation methods are based mostly on ultrasound or computed tomography. This work explores the possibility of tracking the catheter position during ablation treatment of hepatocellular carcinomas (HCC) using an ultra-wideband (UWB) antenna array and microwave radar imaging based on the "Delay and Sum" (DAS) algorithm. The feasibility was first numerically studied on a simple homogeneous liver model. A heterogeneous anthropomorphic 3D model of the treated region consisting of the main organs within the treated area was then used. Various standard radiofrequency ablation (RFA) catheters were placed virtually in the heterogeneous model. The location and orientation of the antenna elements of the developed imaging system and the applied frequency band were studied. Subsequently, an experimental setup consisting of a 3D printed homogeneous anthropomorphic model, eight UWB dipole antennas, and catheters was created and used in a series of measurements. The average accuracy determining the catheter position from simulated and experimental data was 3.88 ± 0.19 and 6.13 ± 0.66 mm, which are close to the accuracy of clinical navigation systems.

• Keywords
• UWB radar, catheter position determination, delay-and-sum, hepatocellular carcinoma, medical imaging, microwave imaging, radiofrequency ablation,
• Publication type
• Journal Article MeSH