Alveolar ridge preservation with guided bone regeneration or socket seal technique. A randomised, single-blind controlled clinical trial

OBJECTIVES: To compare radiographic bone changes, following alveolar ridge preservation (ARP) using Guided Bone Regeneration (GBR), a Socket Seal (SS) technique or unassisted socket healing (Control). MATERIAL AND METHODS: Patients requiring a single rooted tooth extraction in the anterior maxilla, were randomly allocated into: GBR, SS and Control groups (n= 14/). Cone Beam Computed Tomography (CBCT) images were recorded post‐extraction and at 4 months, the mid‐buccal and mid‐palatal alveolar ridge heights (BARH/PARH) were measured. The alveolar ridge width, cross‐sectional socket and alveolar‐process area changes, implant placement feasibility, requirement for bone augmentation and post‐surgical complications were also recorded. RESULTS: BARH and PARH was found to increase with the SS (0.65 mm ± 1.1/0.65 mm ± 1.42) techniques, stabilise with GBR (0.07 mm ± 0.83/0.86 mm ±1.37) and decrease in the Control (−0.52 mm ± 0.8/−0.43 mm ± 0.83). Statistically significance was found when comparing the GBR and SS BARH (p = .04/.005) and GBR PARH (p = .02) against the Control. GBR recorded the smallest reduction in alveolar ridge width (−2.17 mm ± 0.84), when compared to the Control (−2.3 mm ± 1.11) (p = .89). A mid‐socket cross‐sectional area reduction of 4% (−2.27 mm(2) ± 11.89), 1% (−0.88 mm(2) ± 15.48) and 13% (−6.93 mm(2) ± 8.22) was found with GBR, SS and Control groups (GBR vs. Control p = .01). The equivalent alveolar process area reduction was 8% (−7.36 mm(2) ± 10.45), 6% (−7 mm(2) ± 18.97) and 11% (−11.32 mm(2) ± 10.92). All groups supported implant placement, with bone dehiscence noted in 57% (n = 4), 64%(n = 7) and 85%(n = 12) of GBR, SS and Control cases (GBR vs. Control p = .03). GBR had a higher risk of swelling and mucosal colour change, with SS associated with graft sequestration and matrix breakdown. CONCLUSION: GBR ARP was found to be more effective at reducing radiographic bone dimensional changes following tooth extraction

PET/MRI 및 MR-IGRT를 위한 MRI 기반 합성 CT 생성의 타당성 연구

학위논문 (박사) -- 서울대학교 대학원 : 의과대학 의과학과, 2020. 8. 이재성.Over the past decade, the application of magnetic resonance imaging (MRI) in the field of diagnosis and treatment has increased. MRI provides higher soft-tissue contrast, especially in the brain, abdominal organ, and bone marrow without the expose of ionizing radiation. Hence, simultaneous positron emission tomography/MR (PET/MR) system and MR-image guided radiation therapy (MR-IGRT) system has recently been emerged and currently available for clinical study. One major issue in PET/MR system is attenuation correction from MRI scans for PET quantification and a similar need for the assignment of electron densities to MRI scans for dose calculation can be found in MR-IGRT system. Because the MR signals are related to the proton density and relaxation properties of tissue, not to electron density. To overcome this problem, the method called synthetic CT (sCT), a pseudo CT derived from MR images, has been proposed. In this thesis, studies on generating synthetic CT and investigating the feasibility of using a MR-based synthetic CT for diagnostic and radiotherapy application were presented. Firstly, MR image-based attenuation correction (MR-AC) method using level-set segmentation for brain PET/MRI was developed. To resolve conventional inaccuracy MR-AC problem, we proposed an improved ultrashort echo time MR-AC method that was based on a multiphase level-set algorithm with main magnetic field inhomogeneity correction. We also assessed the feasibility of level-set based MR-AC method, compared with CT-AC and MR-AC provided by the manufacturer of the PET/MRI scanner. Secondly, we proposed sCT generation from the low field MR images using 2D convolution neural network model for MR-IGRT system. This sCT images were compared to the deformed CT generated using the deformable registration being used in the current system. We assessed the feasibility of using sCT for radiation treatment planning from each of the patients with pelvic, thoraic and abdominal region through geometric and dosimetric evaluation.지난 10년간 진단 및 치료분야에서 자기공명영상(Magnetic resonance imaging; MRI) 의 적용이 증가하였다. MRI는 CT와 비교해 추가적인 전리방사선의 피폭없이 뇌, 복부 기관 및 골수 등에서 더 높은 연조직 대비를 제공한다. 따라서 MRI를 적용한 양전자방출단층촬영(Positron emission tomography; PET)/MR 시스템과 MR 영상 유도 방사선 치료 시스템(MR-image guided radiation therapy; MR-IGRT)이 진단 및 치료 방사선분야에 등장하여 임상에 사용되고 있다. PET/MR 시스템의 한 가지 주요 문제는 PET 정량화를 위한 MRI 스캔으로부터의 감쇠 보정이며, MR-IGRT 시스템에서 선량 계산을 위해 MR 영상에 전자 밀도를 할당하는 것과 비슷한 필요성을 찾을 수 있다. 이는 MR 신호가 전자 밀도가 아닌 조직의 양성자 밀도 및 T1, T2 이완 특성과 관련이 있기 때문이다. 이 문제를 극복하기 위해, MR 이미지로부터 유래된 가상의 CT인 합성 CT라 불리는 방법이 제안되었다. 본 학위논문에서는 합성 CT 생성 방법 및 진단 및 방사선 치료에 적용을 위한 MR 영상 기반 합성 CT 사용의 임상적 타당성을 조사하였다. 첫째로, 뇌 PET/MR를 위한 레벨셋 분할을 이용한 MR 이미지 기반 감쇠 보정 방법을 개발하였다. MR 이미지 기반 감쇠 보정의 부정확성은 정량화 오류와 뇌 PET/MRI 연구에서 병변의 잘못된 판독으로 이어진다. 이 문제를 해결하기 위해, 자기장 불균일 보정을 포함한 다상 레벨셋 알고리즘에 기초한 개선된 초단파 에코 시간 MR-AC 방법을 제안하였다. 또한 CT-AC 및 PET/MRI 스캐너 제조업체가 제공한 MR-AC와 비교하여 레벨셋 기반 MR-AC 방법의 임상적 사용가능성을 평가하였다. 둘째로, MR-IGRT 시스템을 위한 심층 컨볼루션 신경망 모델을 사용하여 저필드 MR 이미지에서 생성된 합성 CT 방법를 제안하였다. 이 합성 CT 이미지를 변형 정합을 사용하여 생성된 변형 CT와 비교 하였다. 또한 골반, 흉부 및 복부 환자에서의 기하학적, 선량적 분석을 통해 방사선 치료계획에서의 합성 CT를 사용가능성을 평가하였다.Chapter 1. Introduction 1 1.1. Background 1 1.1.1. The Integration of MRI into Other Medical Devices 1 1.1.2. Chanllenges in the MRI Integrated System 4 1.1.3. Synthetic CT Generation 5 1.2. Purpose of Research 6 Chapter 2. MRI-based Attenuation Correction for PET/MRI 8 2.1. Background 8 2.2. Materials and Methods 10 2.2.1. Brain PET Dataset 19 2.2.2. MR-Based Attenuation Map using Level-Set Algorithm 12 2.2.3. Image Processing and Reconstruction 18 2.3. Results 20 2.4. Discussion 28 Chapter 3. MRI-based synthetic CT generation for MR-IGRT 30 3.1. Background 30 3.2. Materials and Methods 32 3.2.1. MR-dCT Paired DataSet 32 3.2.2. Synthetic CT Generation using 2D CNN 36 3.2.3. Data Analysis 38 3.3. Results 41 3.3.1. Image Comparison 41 3.3.2. Geometric Analysis 49 3.3.3. Dosimetric Analysis 49 3.4. Discussion 56 Chapter 4. Conclusions 59 Bibliography 60 Abstract in Korean (국문 초록) 64Docto

Use of colour for hand-filled form analysis and recognition

Colour information in form analysis is currently under utilised. As technology has advanced and computing costs have reduced, the processing of forms in colour has now become practicable. This paper describes a novel colour-based approach to the extraction of filled data from colour form images. Images are first quantised to reduce the colour complexity and data is extracted by examining the colour characteristics of the images. The improved performance of the proposed method has been verified by comparing the processing time, recognition rate, extraction precision and recall rate to that of an equivalent black and white system

Historical analysis and visualization of the retreat of Findelengletscher, Switzerland, 1859–2010

Since the end of the Little Ice Age around 1850, glaciers in Europe have strongly retreated. Thanks to early topographic surveys in Switzerland, accurate maps are available, which enable us to trace glacier changes back in time. The earliest map for all of Switzerland that is usable for a detailed analysis is the Dufour map from around 1850 with subsequent topographic maps on a ~ 20 year interval. Despite the large public and scientific interest in glacier changes through time, this historic dataset has not yet been fully utilized for topographic change assessment or visualization of historic glacier extents. In this study, we use eleven historical topographic maps and more recent digital datasets for the region of Zermatt to analyze geometric changes (length, area and volume) of Findelengletscher as well as for creating animations of glacier evolution through time for use in public communication. All maps were georeferenced, the contour lines digitized, and digital elevation models (DEMs) created and co-registered. Additional digital data like the SRTM X-band DEM and high resolution laser scanning data were used to extend the analysis until 2010. Moreover, one independent DEM from aerial photogrammetry was used for comparison. During the period 1859–2010, Findelengletscher lost 3.5 km of its length (6.9 km in 2010), 4.42 ± 0.13 km² of its area (15.05 ± 0.45 km² in 2010) and 1.32 ± 0.52 km³ of its volume. The average rate of thickness loss is 0.45 ± 0.042 m yr− 1 for the 151 years period. Four periods with high thickness change from − 0.56 m ± 0.28 yr− 1 (1859–1881), − 0.40 ± 0.08 m yr− 1 (1937–1965), − 0.90 ± 0.31 m yr− 1 (1995–2000) and − 1.18 ± 0.02 m yr− 1 (2000–2005) have been identified. Small positive thickness changes were found for the periods 1890–1909 (+ 0.09 ± 0.46 m yr − 1) and 1988–1995 (+ 0.05 ± 0.24 m yr− 1). During its retreat with intermittent periods of advance, the glacier separated into three parts. The above changes are demonstrated through an animation (available from the supplementary material), which has been created to inform the general public

PNT-Edge: Towards Robust Edge Detection with Noisy Labels by Learning Pixel-level Noise Transitions

Relying on large-scale training data with pixel-level labels, previous edge detection methods have achieved high performance. However, it is hard to manually label edges accurately, especially for large datasets, and thus the datasets inevitably contain noisy labels. This label-noise issue has been studied extensively for classification, while still remaining under-explored for edge detection. To address the label-noise issue for edge detection, this paper proposes to learn Pixel-level NoiseTransitions to model the label-corruption process. To achieve it, we develop a novel Pixel-wise Shift Learning (PSL) module to estimate the transition from clean to noisy labels as a displacement field. Exploiting the estimated noise transitions, our model, named PNT-Edge, is able to fit the prediction to clean labels. In addition, a local edge density regularization term is devised to exploit local structure information for better transition learning. This term encourages learning large shifts for the edges with complex local structures. Experiments on SBD and Cityscapes demonstrate the effectiveness of our method in relieving the impact of label noise. Codes are available at https://github.com/DREAMXFAR/PNT-Edge.Comment: Accepted by ACM-MM 202

Waking-like Brain Function in Embryos

Background: Experience-dependent plastic changes in the brain underlying complex forms of learning are generally initiated when organisms are awake, and this may limit the earliest developmental time at which learning about external events can take place. It is not known whether waking-like brain function is present prenatally in higher vertebrate (bird or mammal)embryos, or whether embryos have brain circuitry that can selectively turn on a waking-like state in response to salient external sensory stimulation. Results: Combining submillimeter-resolution brain positron emission tomography (PET), structural X-ray computed tomography (CT) of the skeleton for fine-scale embryo aging, and noninvasive behavioral recording of chicken embryos in the egg revealed unexpectedly wide variation in prenatal brain activity, inversely related to behavioral activity, which developed into different sleep-like fetal brain states. Brief prenatal exposure to a salient chicken vocalization (eliciting strong postnatal behavioral responses) increased higher-brain activity significantly more than a spectrally and temporally matching ‘‘nonvocal’’ noise analog. Patterns of correlated activity between the brainstem and higher-brain areas resembling awake, posthatching animals were seen exclusively in chicken-stimulated embryos. Conclusions: Waking-like brain function is present in a latent but inducible state during the final 20% of embryonic life, selectively modulated by context-dependent monitoring circuitry. These data also reveal the developmental emergence of sleep-like behavior and its linkage to metabolic brain states and highlight problems with assigning embryo brain states based on behavioral observations.Fundación BBVA, Cátedra de Biomedicina (Spain)National Science and Engineering Research Council of CanadaCanadian Fund for InnovationScuola Internazionale Superiore di Studi Avanzati (Trieste, Italia)En prens

In situ optical coherence tomography of percutaneous implant-tissue interfaces in a murine model

Novel surface coatings of percutaneous implants need to be tested in biocompatibility studies. The use of animal models for testing usually involves numerous lethal biopsies for the analysis of the implant-tissue interface. In this study, optical coherence tomography (OCT) was used to monitor the reaction of the skin to a percutaneous implant in an animal model of hairless but immunocompetent mice. In vivo optical biopsies with OCT were taken at days 7 and 21 after implantation and post mortem on the day of noticeable inflammation. A Fourier-domain OCT was programmed for spoke pattern scanning schemes centered at the implant midpoint to reduce motion artifacts during in vivo imaging. Image segmentation allowed the automatic detection and morphometric analysis of the skin contour and the subcutaneous implant anchor. On the basis of the segmentation, the overall refractive index of the tissue within one OCT data set was estimated as a free parameter of a fitting algorithm, which corrects for the curved distortion of the planar implant base in the OCT images. OCT in combination with the spoke scanning scheme and image processing provided time-resolved three-dimensional optical biopsies around the implants to assess tissue morphology.DFGBMBF/TExoProNSF-ERC/Revolutionizing Metallic Biomaterial

Assembly of a polymer lab-on-chip device for impedimetric measurements of D-dimers in whole blood

This paper reports the development and characterisation of an assembly technology for a polymer lab-on-chip. The system consists of a 150 m deep hot embossed microfluidic channel in polycarbonate and Au electrodes fabricated separately by photolithography on polyethylenenaphthalate. The system is designed for impedimetric immunoassay detection in whole blood. Electrode layer and microfluidic substrate are joined by means of a 50 m thick double-sided medical grade adhesive tape, adjusted with an optical alignment system. The bond proved to be liquid tight at room temperature. An alignment accuracy of 34 m (+/- 19 m) evaluated over a set of 23 samples, was achieved. The effect of alignment accuracy of the intermediate adhesive film on whole blood flow properties in the device is studied. Already an alignment error of 70 m increases the flushing out time of whole blood by approximately 20 %