Large-Scale Indoor Camera Positioning Using Fiducial Markers.

Estimating the pose of a large set of fixed indoor cameras is a requirement for certain applications in augmented reality, autonomous navigation, video surveillance, and logistics. However, accurately mapping the positions of these cameras remains an unsolved problem. While providing partial solutions, existing alternatives are limited by their dependence on distinct environmental features, the requirement for large overlapping camera views, and specific conditions. This paper introduces a novel approach to estimating the pose of a large set of cameras using a small subset of fiducial markers printed on regular pieces of paper. By placing the markers in areas visible to multiple cameras, we can obtain an initial estimation of the pair-wise spatial relationship between them. The markers can be moved throughout the environment to obtain the relationship between all cameras, thus creating a graph connecting all cameras. In the final step, our method performs a full optimization, minimizing the reprojection errors of the observed markers and enforcing physical constraints, such as camera and marker coplanarity and control points. We validated our approach using novel artificial and real datasets with varying levels of complexity. Our experiments demonstrated superior performance over existing state-of-the-art techniques and increased effectiveness in real-world applications. Accompanying this paper, we provide the research community with access to our code, tutorials, and an application framework to support the deployment of our methodology.

Fiducial Objects: Custom Design and Evaluation.

Camera pose estimation is vital in fields like robotics, medical imaging, and augmented reality. Fiducial markers, specifically ArUco and Apriltag, are preferred for their efficiency. However, their accuracy and viewing angle are limited when used as single markers. Custom fiducial objects have been developed to address these limitations by attaching markers to 3D objects, enhancing visibility from multiple viewpoints and improving precision. Existing methods mainly use square markers on non-square object faces, leading to inefficient space use. This paper introduces a novel approach for creating fiducial objects with custom-shaped markers that optimize face coverage, enhancing space utilization and marker detectability at greater distances. Furthermore, we present a technique for the precise configuration estimation of these objects using multiviewpoint images. We provide the research community with our code, tutorials, and an application to facilitate the building and calibration of these objects. Our empirical analysis assesses the effectiveness of various fiducial objects for pose estimation across different conditions, such as noise levels, blur, and scale variations. The results suggest that our customized markers significantly outperform traditional square markers, marking a positive advancement in fiducial marker-based pose estimation methods.

UCO Physical Rehabilitation: New Dataset and Study of Human Pose Estimation Methods on Physical Rehabilitation Exercises.

Physical rehabilitation plays a crucial role in restoring motor function following injuries or surgeries. However, the challenge of overcrowded waiting lists often hampers doctors' ability to monitor patients' recovery progress in person. Deep Learning methods offer a solution by enabling doctors to optimize their time with each patient and distinguish between those requiring specific attention and those making positive progress. Doctors use the flexion angle of limbs as a cue to assess a patient's mobility level during rehabilitation. From a Computer Vision perspective, this task can be framed as automatically estimating the pose of the target body limbs in an image. The objectives of this study can be summarized as follows: (i) evaluating and comparing multiple pose estimation methods; (ii) analyzing how the subject's position and camera viewpoint impact the estimation; and (iii) determining whether 3D estimation methods are necessary or if 2D estimation suffices for this purpose. To conduct this technical study, and due to the limited availability of public datasets related to physical rehabilitation exercises, we introduced a new dataset featuring 27 individuals performing eight diverse physical rehabilitation exercises focusing on various limbs and body positions. Each exercise was recorded using five RGB cameras capturing different viewpoints of the person. An infrared tracking system named OptiTrack was utilized to establish the ground truth positions of the joints in the limbs under study. The results, supported by statistical tests, show that not all state-of-the-art pose estimators perform equally in the presented situations (e.g., patient lying on the stretcher vs. standing). Statistical differences exist between camera viewpoints, with the frontal view being the most convenient. Additionally, the study concludes that 2D pose estimators are adequate for estimating joint angles given the selected camera viewpoints.

sSLAM: Speeded-Up Visual SLAM Mixing Artificial Markers and Temporary Keypoints.

Environment landmarks are generally employed by visual SLAM (vSLAM) methods in the form of keypoints. However, these landmarks are unstable over time because they belong to areas that tend to change, e.g., shadows or moving objects. To solve this, some other authors have proposed the combination of keypoints and artificial markers distributed in the environment so as to facilitate the tracking process in the long run. Artificial markers are special elements (similar to beacons) that can be permanently placed in the environment to facilitate tracking. In any case, these systems keep a set of keypoints that is not likely to be reused, thus unnecessarily increasing the computing time required for tracking. This paper proposes a novel visual SLAM approach that efficiently combines keypoints and artificial markers, allowing for a substantial reduction in the computing time and memory required without noticeably degrading the tracking accuracy. In the first stage, our system creates a map of the environment using both keypoints and artificial markers, but once the map is created, the keypoints are removed and only the markers are kept. Thus, our map stores only long-lasting features of the environment (i.e., the markers). Then, for localization purposes, our algorithm uses the marker information along with temporary keypoints created just in the time of tracking, which are removed after a while. Since our algorithm keeps only a small subset of recent keypoints, it is faster than the state-of-the-art vSLAM approaches. The experimental results show that our proposed sSLAM compares favorably with ORB-SLAM2, ORB-SLAM3, OpenVSLAM and UcoSLAM in terms of speed, without statistically significant differences in accuracy.

Reflection-Aware Generation and Identification of Square Marker Dictionaries.

Square markers are a widespread tool to find correspondences for camera localization because of their robustness, accuracy, and detection speed. Their identification is usually based on a binary encoding that accounts for the different rotations of the marker; however, most systems do not consider the possibility of observing reflected markers. This case is possible in environments containing mirrors or reflective surfaces, and its lack of consideration is a source of detection errors, which is contrary to the robustness expected from square markers. This is the first work in the literature that focuses on reflection-aware square marker dictionaries. We present the derivation of the inter-marker distance of a reflection-aware dictionary and propose new algorithms for generating and identifying such dictionaries. Additionally, part of the proposed method can be used to optimize preexisting dictionaries to take reflection into account. The experimentation carried out demonstrates how our proposal greatly outperforms the most popular predefined dictionaries in terms of inter-marker distance and how the optimization process significantly improves them.

Zinc associated nanomaterials and their intervention in emerging respiratory viruses: Journey to the field of biomedicine and biomaterials.

Respiratory viruses represent a severe public health risk worldwide, and the research contribution to tackle the current pandemic caused by the SARS-CoV-2 is one of the main targets among the scientific community. In this regard, experts from different fields have gathered to confront this catastrophic pandemic. This review illustrates how nanotechnology intervention could be valuable in solving this difficult situation, and the state of the art of Zn-based nanostructures are discussed in detail. For virus detection, learning from the experience of other respiratory viruses such as influenza, the potential use of Zn nanomaterials as suitable sensing platforms to recognize the S1 spike protein in SARS-CoV-2 are shown. Furthermore, a discussion about the antiviral mechanisms reported for ZnO nanostructures is included, which can help develop surface disinfectants and protective coatings. At the same time, the properties of Zn-based materials as supplements for reducing viral activity and the recovery of infected patients are illustrated. Within the scope of noble adjuvants to improve the immune response, the ZnO NPs properties as immunomodulators are explained, and potential prototypes of nanoengineered particles with metallic cations (like Zn2+) are suggested. Therefore, using Zn-associated nanomaterials from detection to disinfection, supplementation, and immunomodulation opens a wide area of opportunities to combat these emerging respiratory viruses. Finally, the attractive properties of these nanomaterials can be extrapolated to new clinical challenges.

Biosensors based on zinc oxide thin-film transistors using recyclable plastic substrates as an alternative for real-time pathogen detection.

The fabrication of biosensors has different future applications mainly from the perspective of eco-friendly technologies. Label-free strategies, recyclable materials and low-temperature processing are parameters to consider for the development of a new generation of biosensor devices. In this work, Zinc oxide (ZnO) Thin-film Transistors (TFTs) using recyclable plastic substrates were used for real-time enteropathogenic Escherichia coli detection as an approach for biosensing (bio-TFTs). Fourier Transform Infrared Spectroscopy was used to verify the characteristic absorption peaks at the different steps of the bio-TFT assembly process. The bio-TFTs are ready to observe the bacterial detection by electrical characterization. Finally, detection was validated by a coupled strategy that fuses the genomic DNA extraction from bacteria attached in situ over bio-TFTs surface and, the development of the Polymerase Chain Reaction to amplify specific genes from enteropathogenic Escherichia coli.

Joint scene and object tracking for cost-Effective augmented reality guided patient positioning in radiation therapy.

BACKGROUND AND OBJECTIVE: The research is done in the field of Augmented Reality (AR) for patient positioning in radiation therapy is scarce. We propose an efficient and cost-effective algorithm for tracking the scene and the patient to interactively assist the patient's positioning process by providing visual feedback to the operator. Up to our knowledge, this is the first framework that can be employed for mobile interactive AR to guide patient positioning. METHODS: We propose a pointcloud processing method that, combined with a fiducial marker-mapper algorithm and the generalized ICP algorithm, tracks the patient and the camera precisely and efficiently only using the CPU unit. The 3D reference model and body marker map alignment is calculated employing an efficient body reconstruction algorithm. RESULTS: Our quantitative evaluation shows that the proposed method achieves a translational and rotational error of 4.17 mm/0.82∘ at 9 fps. Furthermore, the qualitative results demonstrate the usefulness of our algorithm in patient positioning on different human subjects. CONCLUSION: Since our algorithm achieves a relatively high frame rate and accuracy employing a regular laptop (without a dedicated GPU), it is a very cost-effective AR-based patient positioning method. It also opens the way for other researchers by introducing a framework that could be improved upon for better mobile interactive AR patient positioning solutions in the future.

3D Reconstruction and alignment by consumer RGB-D sensors and fiducial planar markers for patient positioning in radiation therapy.

BACKGROUND AND OBJECTIVE: Patient positioning is a crucial step in radiation therapy, for which non-invasive methods have been developed based on surface reconstruction using optical 3D imaging. However, most solutions need expensive specialized hardware and a careful calibration procedure that must be repeated over time.This paper proposes a fast and cheap patient positioning method based on inexpensive consumer level RGB-D sensors. METHODS: The proposed method relies on a 3D reconstruction approach that fuses, in real-time, artificial and natural visual landmarks recorded from a hand-held RGB-D sensor. The video sequence is transformed into a set of keyframes with known poses, that are later refined to obtain a realistic 3D reconstruction of the patient. The use of artificial landmarks allows our method to automatically align the reconstruction to a reference one, without the need of calibrating the system with respect to the linear accelerator coordinate system. RESULTS: The experiments conducted show that our method obtains a median of 1 cm in translational error, and 1∘of rotational error with respect to reference pose. Additionally, the proposed method shows as visual output overlayed poses (from the reference and the current scene) and an error map that can be used to correct the patient's current pose to match the reference pose. CONCLUSIONS: A novel approach to obtain 3D body reconstructions for patient positioning without requiring expensive hardware or dedicated graphic cards is proposed. The method can be used to align in real time the patient's current pose to a preview pose, which is a relevant step in radiation therapy.

Safety of regadenoson as a pharmacologic stress agent for myocardial perfusion imaging in chronic kidney disease patients not on hemodialysis.

BACKGROUND: Pharmacokinetic studies suggest delayed clearance of Regadenoson (REG), a new selective A2A receptor agonist in chronic kidney disease (CKD). The safety of REG in large series of CKD patients in daily clinical practice remains unstudied. METHODS: Retrospective study of patients with eGFR < 60 mL/min (n = 411, Grp 1, CKD) were compared to patients with eGFR ≥ 60 mL/min (n = 638, Grp 2, Control) undergoing REG-SPECT from Jan to Nov 2009. Patient demographics, REG-SPECT data, side effects, and arrhythmia occurrences were evaluated. RESULTS: No major adverse events were noted immediately after REG-SPECT or at 1 week of follow-up. There were no differences in any arrhythmias in between the two groups (Grp 1, 47.2% vs Grp 2, 42.9%, P = ns). Ninety-nine percent of arrhythmias in CKD patients were PACs or PVCs. Transient junctional rhythm was observed in one CKD patient. There were no occurrences of second degree or higher degree AV block. Grp 1 had a blunted heart rate response (16.6 ± 16.1 vs 24.9 ± 20.3 bpm, P ≤ .001) and greater systolic blood pressure drop response (-7.4 ± 21.1 vs -1.4 ± 20.9 mm Hg, P ≤ .001) compared to Grp 2. Transient headache was more in Grp 2 (15.8% vs 22.6%, P ≤ .007). Aminophylline use to ward-off the side effects was comparable (9.5% vs 9.9%, P = ns). CONCLUSION: REG-SPECT can be safely performed in CKD non-dialysis patients with excellent tolerability, minimal side effects, and favorable hemodynamic responses compared to control group.

Microcarcinoma papilar de tiroides en adolescente: Extensión de la tiroidectomía y necesidad de terapia ablativa

Objetivo: Presentar el caso de una adolescente con microcarcinoma papilar de tiroides, patología de manejo terapéutico controversial. Caso Clínico: Adolescente femenina de 15 años de edad, quien presentó aumento de volumen en región lateral izquierda del cuello de 4 años de evolución, de crecimiento lentamente progresivo, al inicio indoloro, posteriormente disfagia con dolor a la palpación, motivo por el cual se le realizó tiroidectomía sub-total. Estudio anatomopatológico de la pieza reportó microcarcinoma papilar de 6 mm de diámetro, sin infiltración capsular. Es referida para valoración por Medicina Nuclear y seguimiento por el servicio de Endocrinología. Se encuentran escasos restos tiroideos bilaterales eutópicos. El tumor papilar <1 cm, en ausencia de invasión capsular, infiltración a ganglios, metástasis locales o a distancia, se consideró de bajo riesgo, por lo que se decidió no completar la tiroidectomía ni administrar terapia ablativa.Se inició terapia supresiva con levotiroxina. Se planteó seguimiento clínico, paraclínico (perfil tiroideo y tiroglobulina, a pesar de restos tiroideos, para detectar elevaciones sobre el nivel basal) e imagenológico con ultrasonido de cuello. Actualmente, adolescente en buenas condiciones generales con parámetros de seguimiento estables. Conclusiones: El microcarcinoma papilar de tiroides tiene bajo riesgo de recurrencia y de mortalidad. La extensión de la cirugía es controversial, tiroidectomía total es la indicada para algunos y lobectomía ampliada para otros. La terapia ablativa postoperatoria no ha demostrado ser beneficiosa y la terapia supresiva con levotiroxina es de utilidad. Según el curso clínico y la respuesta al tratamiento, el riesgo de recurrencia y mortalidad debe ser re-evaluado periódicamente, siempre prevaleciendo el juicio clínico.

Objective: To report the case of a teenager with papillary thyroid microcarcinoma, pathology with controversial therapeutic management. Clinical Case: Adolescent women 15 years of age, who presented a painless lowly progressive increase in volume of 4 years of evolution on the left lateral region of theneck. Subsequently dysphagia with tenderness, reason why subtotal thyroidectomy was performed. Pathologic study reported papillary microcarcinoma of 6 mm in diameter, without capsular infiltration. She was referred for evaluation by Nuclear Medicine and monitoring by the Endocrinology service. Few bilateral eutopic thyroid remnants were found. A papillary tumor<1 cm, in the absence of capsular invasion, lymphinfiltration, local or distant metastasis, was considered low risk, so it was decided not to complete the thyroidectomy and do not administer ablative therapy. It started with levothyroxine suppressive therapy. It was decided to follow up the patient by clinical, laboratory (thyroid profile and thyroglobulin, in spite of thyroid remnants, to detect elevations above baseline) and ultrasound. Currently the patient is in good general condition with stable tracking variables. Conclusion: Papillary thyroid microcarcinoma has low risk of recurrence and mortality. The extent of surgery is controversial, total thyroidectomy is indicated for some and expanded lobectomy for others. Postoperative ablative therapy has not proven beneficial and levothyroxine suppressive therapy is useful. According to the clinical course and response to treatment, the risk of recurrence and mortality should be re-evaluated periodically, always prevailing clinical judgment.

Quiste hepático gigante resuelto por laparoscopia / Giant non-árasitic liver cyst resolved by laparoscopy

Introducción. Los quistes simples no parasitarios del hígado, son malformaciones congénitas revestidas de epitelio cuboide o escamoso, que pueden ser únicos o múltiples.Caso clínico. Se presenta el caso de un paciente del sexo femenino de 8 años de edad, que ingresó con el diagnóstico de masa abdominal. Se sometió a protocolo de estudio reportando el ultrasonido (USG) y la tomografía axial computada (TAC) abdominal una gran imagen quística dependiente del hígado. Por medio de laparoscopia se efectuó destechamiento del quiste y colecistectomía por estar involucrada la vesícula. El resultado es satisfactorio a 3 años.Conclusiones. Laparoscopia se debe considerar como una buena alternativa de manejo curativo en los quistes hepáticos.

Síndrome de Peutz-Jeghers / Peutz-Jeghers syndrome

Se presentan tres pacientes con síndrome de Peutz- Jeghers. En dos de ellos su primera manifestación clínica fue la invaginación del intestino delgado. En el tercer paciente el diagnóstico se hizo por la presencia de las lesiones mucocutáneas típicas. En todos ellos se demostró la presencia de los pólipos en el tránsito de estómago e intestino delgado o en el enema baritado o la endoscopía alta a la colonoscopía. Algunos pólipos fueron extirpados durante este último procedimiento. Se destaca la utilidad de la polipectomía endoscópica

Variedades en el origen y distribución del tronco celíaco / Varieties in the origin and distribution of the celiac plexus

La revisión de la literatura acerca del tronco celíaco nos muestra múltiples variedades en cuanto a su origen y división en sus ramas clásicas. A objeto de verificar dichas variedades, de indiscutible valor anatomoquirúrgico, se efectuaron disecciones anatómicas en 40 cadáveres adultos. Como deducción de las disecciones se comprueba que el mayor porcentaje de los casos corresponde al tipo de bifurcación hepatoesplénica con un 50%de los casos (lo que coincide con Río-Branco 59%. Descomps 46%y Paturet 45%. Llama la atención el alto porcentaje de casos en que la arteria hepática nace independiente del tronco (20%, así como la ausencia de dicho tronco celíaco (10%). La longitud promedio del tronco celíaco fue de 2.22 cms. con una desviación standard de 0.59 cms.; la arteria gástrica izquierda se origina como promedio a 1.32 cms. y con una desviación stardard de 0,80 cms. Entre el tronco celíaco y la arteria mesentérica superior existe una distancia promedio de 2,35 cms. con una desviación standard de 0,50 cms. Todas estas cifras coinciden significativamente con las indicadas por los autores utilizados en las referencias bibliográficas

Indice nasal e índices faciales en individuos chilenos: morfología nasal / Nasal and facial indexes in chilean people: nasal morphology

Los autores efectuaron mediciones antropométricas destinadas a determinar INDICES FACIALES, INDICE NASAL y las características somatoscópicas de la naríz, en 503 individuos chilenos, de ambos sexos distribuídos en dos muestras: una de 12-13 años de edad y otra de 18-25 años de edad. Se analizaron ESTADISTICAMENTE los distintos índices obtenidos y se estudiaron porcentualmente los caracteres ANATOMICOS nasales, buscándose finalmente las variables y relaciones existentes entre ellos