31 research outputs found
Aggregated Deep Local Features for Remote Sensing Image Retrieval
Remote Sensing Image Retrieval remains a challenging topic due to the special
nature of Remote Sensing Imagery. Such images contain various different
semantic objects, which clearly complicates the retrieval task. In this paper,
we present an image retrieval pipeline that uses attentive, local convolutional
features and aggregates them using the Vector of Locally Aggregated Descriptors
(VLAD) to produce a global descriptor. We study various system parameters such
as the multiplicative and additive attention mechanisms and descriptor
dimensionality. We propose a query expansion method that requires no external
inputs. Experiments demonstrate that even without training, the local
convolutional features and global representation outperform other systems.
After system tuning, we can achieve state-of-the-art or competitive results.
Furthermore, we observe that our query expansion method increases overall
system performance by about 3%, using only the top-three retrieved images.
Finally, we show how dimensionality reduction produces compact descriptors with
increased retrieval performance and fast retrieval computation times, e.g. 50%
faster than the current systems.Comment: Published in Remote Sensing. The first two authors have equal
contributio
Dual Embedding Expansion for Vehicle Re-identification
Vehicle re-identification plays a crucial role in the management of
transportation infrastructure and traffic flow. However, this is a challenging
task due to the large view-point variations in appearance, environmental and
instance-related factors. Modern systems deploy CNNs to produce unique
representations from the images of each vehicle instance. Most work focuses on
leveraging new losses and network architectures to improve the descriptiveness
of these representations. In contrast, our work concentrates on re-ranking and
embedding expansion techniques. We propose an efficient approach for combining
the outputs of multiple models at various scales while exploiting tracklet and
neighbor information, called dual embedding expansion (DEx). Additionally, a
comparative study of several common image retrieval techniques is presented in
the context of vehicle re-ID. Our system yields competitive performance in the
2020 NVIDIA AI City Challenge with promising results. We demonstrate that DEx
when combined with other re-ranking techniques, can produce an even larger gain
without any additional attribute labels or manual supervision
Cardiac involvement in Erdheim- Chester disease: MRI findings and literature revision
: Erdheim-Chester disease (ECD) is a rare form of non-Langerhans cell histiocytosis, characterized by the involvement of several organs. The lesions may be skeletal or extra-skeletal: in particular, long bones, skin, lungs, and the cardiovascular and the central nervous systems can be affected. In this report, we describe a case of a 34-year-old man, who came to our observation with symptomatic ECD, for a correct assessment of the degree of cardiac involvement through magnetic resonance imaging (MRI)
Cardiac hybrid imaging: novel tracers for novel targets
Non-invasive cardiac imaging has explored enormous advances in the last few decades. In particular, hybrid imaging represents the fusion of information from multiple imaging modalities, allowing to provide a more comprehensive dataset compared to traditional imaging techniques in patients with cardiovascular diseases. The complementary anatomical, functional and molecular information provided by hybrid systems are able to simplify the evaluation procedure of various pathologies in a routine clinical setting. The diagnostic capability of hybrid imaging modalities can be further enhanced by introducing novel and specific imaging biomarkers. The aim of this review is to cover the most recent advancements in radiotracers development for SPECT/CT, PET/CT, and PET/MRI for cardiovascular diseases
Advanced CMR Techniques in Anderson-Fabry Disease: State of the Art
Anderson-Fabry disease (AFD) is a rare multisystem X-linked lysosomal storage disorder caused by α-galactosidase A enzyme deficiency. Long-term cardiac involvement in AFD results in left ventricular hypertrophy and myocardial fibrosis, inducing several complications, mainly
arrhythmias, valvular dysfunction, and coronary artery disease. Cardiac magnetic resonance (CMR) represents the predominant noninvasive imaging modality for the assessment of cardiac involvement in the AFD, being able to comprehensively assess cardiac regional anatomy, ventricular function as well as to provide tissue characterization. This review aims to explore the role of the most advanced CMR techniques, such as myocardial strain, T1 and T2 mapping, perfusion and hybrid imaging, as diagnostic and prognostic biomarkers
Multiscale Convolutional Descriptor Aggregation for Visual Place Recognition
Visual place recognition using query and database images from different sources remains a challenging task in computer vision. Our method exploits global descriptors for efficient image matching and local descriptors for geometric verification. We present a novel, multi-scale aggregation method for local convolutional descriptors, using memory vector construction for efficient aggregation. The method enables to find preliminary set of image candidate matches and remove visually similar but erroneous candidates. We deploy the multi-scale aggregation for visual place recognition on 3 large-scale datasets. We obtain a Recall@10 larger than 94% for the Pittsburgh dataset, outperforming other popular convolutional descriptors used in image retrieval and place recognition. Additionally, we provide a comparison for these descriptors on a more challenging dataset containing query and database images obtained from different sources, achieving over 77% Recall@10
Toward Multilabel Image Retrieval for Remote Sensing
The availability of large-scale remote sensing (RS) data facilitates a wide range of applications, such as disaster management and urban planning. An approach for such problems is image retrieval, where, given a query image, the goal is to find the most relevant match from a database. Most RS literature has been focused on single-label retrieval, where we assume an image has a single label. The primary challenge in single-label RS retrieval is that performance in most datasets is saturated, and it has become difficult to compare the performance of different methods. In this work, we extend the major multilabel classification datasets to the multilabel retrieval problem. We also define protocols, provide evaluation metrics, and study the impact of commonly used loss functions and reranking methods for multilabel retrieval. To this end, a novel multilabel loss function and a reranking technique are proposed, which circumvent the challenges present in conventional single-label image retrieval. The developed loss function considers both class and feature similarity. The proposed reranking technique achieves high performance with computation cost that is well-suited for fast online retrieval