Enoch Peserico

VirtualShave: Automated hair removal from digital dermatoscopic images

VirtualShave is a novel tool to remove hair from digital dermatoscopic images. First, individual hairs are identified using a top-hat filter followed by morphological postprocessing. Then, they are replaced through PDE-based inpainting with an estimate of the underlying occluded skin. VirtualShaves performance is comparable to that of a human operator removing hair manually, and the resulting images are almost indistinguishable from those of hair-free skin.

Where's the naevus? Inter-operator variability in the localization of melanocytic lesion border.

The first step in the analysis of a dermatoscopically imaged melanocytic lesion is segmentation – informally, isolating those points in the image belonging to the lesion from those belonging to the surrounding non‐lesional skin. Although typically studied in the context of automated analysis, segmentation is a necessary step even for human operators who plan to evaluate quantitative features of a lesion (such as diameter or asymmetry).

Psoriasis segmentation through chromatic regions and Geometric Active Contours

We present a novel approach to the segmentation of psoriasis lesions in “full body” digital photographs potentially involving dozens or even hundreds of separate lesions. Our algorithm first isolates a set of zones that certainly correspond to lesional plaques based on chromatic information, and then expands these zones to achieve an accurate segmentation of plaques through a Geometric Active Contours method. The variability in segmentation between our algorithm and different human operators appears comparable to the variability between human operators.

PariSync: Clock synchronization in P2P networks

This paper presents PariSync, a distributed system for clock synchronization in DHT-based peer to peer networks. PariSync is formed by two modules: a topology module, that chooses for each node a small subset of neighbors with which to exchange timing information (piggybacking on the DHT link structure) and an extimation module, that assembles the information into an extimate of the nodes offset and drift from a global virtual clock emerging from the consensus of all peers. PariSync works on extremely large peer-to-peer networks (millions of nodes) exhibiting good performance even in the presence of churn and malicious nodes. We provide a version of PariSync in pure Java and in JXTA.

Variability in human and automatic segmentation of melanocytic lesions

In a double blind evaluation of 60 digital der-matoscopic images by 4 “junior”, 4 “senior” and 4 “expert” dermatologists (dermatoscopy training respectively less than 1 year, between 1 and 5 years, and more than 5 years), a significant inter-operator variability was observed in melanocytic lesion border identification (with a disagreement of the order of 10 - 20% of the area of the lesions). Expert dermatologists showed greater agreement among themselves than with senior and junior dermatologists, and a slight tendency towards “tighter” segmentations. The human inter-operator variability was then used to evaluate the segmentation accuracy of 4 algorithms, representative of the 3 fundamental state-of-the-art automated segmentation techniques and of a fourth, novel, technique. Our evaluation methodology addresses a number of crucial difficulties encountered in previous studies and may be of independent interest. 3 of the 4 algorithms showed considerably less agreement with expert dermatologists than even senior and junior dermatologists did (with a disagreement of the order of 30% of the area of the lesions); the remaining algorithm, however, showed agreement with expert dermatologists comparable to that of other expert dermatologists.

psort, Yet Another Fast Stable Sorting Software

psort was the fastest sorting software in 2008 according to the Pennysort benchmark, sorting 181GB of data for 0.01

The power of local information in PageRank

of computer time. This paper details its internals, and the careful fitting of its architecture to the structure of modern PCs-class platforms, allowing it to outperform state-of-the-art sorting software such as GNUsort or STXXL .

Is (N)PRI suitable for evaluating automated segmentation of cutaneous lesions

Can one assess, by visiting only a small portion of a graph, if a given node has a significantly higher PageRank score than another? We show that the answer strongly depends on the interplay between the required correctness guarantees (is one willing to accept a small probability of error?) and the graph exploration model (can one only visit parents and children of already visited nodes?).

Automated Detection of New or Evolving Melanocytic Lesions Using a 3D Body Model

An example of anomalous behaviour of the (Normalised) Probabilistic Rand Index - due to its non-monotonicity with the fraction of misclassified pixels - raises doubts on its suitability as a metric for cutaneous lesion segmentation.

Brief Announcement: On Approximating PageRank Locally with Sublinear Query Complexity

Detection of new or rapidly evolving melanocytic lesions is crucial for early diagnosis and treatment of melanoma. We propose a fully automated pre-screening system for detecting new lesions or changes in existing ones, on the order of 2 - 3mm, over almost the entire body surface. Our solution is based on a multi-camera 3D stereo system. The system captures 3D textured scans of a subject at different times and then brings these scans into correspondence by aligning them with a learned, parametric, non-rigid 3D body model. This means that captured skin textures are in accurate alignment across scans, facilitating the detection of new or changing lesions. The integration of lesion segmentation with a deformable 3D body model is a key contribution that makes our approach robust to changes in illumination and subject pose.