Remo Sala

Politecnico di Milano, Milano, Lombardy, Italy

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Publications (26)17.44 Total impact

  • E Canciani · A Vandone · R Sala
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    ABSTRACT: This paper presents a metrological characterization study of SICK LMS 511 laser scanner, with an extended analysis of its main acquisition issues. Various parameters that could affect the sensor performances, such as warm-up time, target properties (color and material), and target position (distance and orientation) are investigated. Moreover, the mixed pixel problem is introduced and, finally, since the sensor is designed to work in a wide outdoor environment, the effect of direct sun light is taken into account. Some cases of faulty data are identified and explanations discussed.
    No preview · Article · Nov 2015 · Journal of Physics Conference Series
  • C Cattaneo · G Mainetti · R Sala
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    ABSTRACT: Video surveillance systems are commonly used as important sources of quantitative information but from the acquired images it is possible to obtain a large amount of metric information. Yet, different methodological issues must be considered in order to perform accurate measurements using images. The most important one is the camera calibration, which is the estimation of the parameters defining the camera model. One of the most used camera calibration method is the Zhang's method, that allows the estimation of the linear parameters of the camera model. This method is very diffused as it requires a simple setup and it allows to calibrate cameras using a simple and fast procedure, but it does not consider lenses distortions, that must be taken into account with short focal lenses, commonly used in video surveillance systems. In order to perform accurate measurements, the linear camera model and the Zhang's method are improved in order to take nonlinear parameters into account and compensate the distortion contribute. In this paper we first describe the pinhole camera model that considers cameras as central projection systems. After a brief introduction to the camera calibration process and in particular the Zhang's method, we give a description of the different types of lens distortions and the techniques used for the distortion compensation. At the end some numerical example are shown in order to demonstrate the importance of the distortion compensation to obtain accurate measurements.
    No preview · Article · Nov 2015 · Journal of Physics Conference Series
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    ABSTRACT: This paper presents an overview of the Lecco Innovation Hub project and in particular to the Sailing Yacht Lab project a 10 m length sailing yacht which aims to be a full scale measurement device in the sailing yacht research field. A description of scientific framework, measurement capabilities as well as of the principal design, building process, project management and commissioning is provided with some examples of preliminary collected data obtained during the first sea trials. Finally an overview of the ongoing project tasks and future project developments is provided including potential research and knowledge achievements for sailing yacht research field.
    Full-text · Article · Aug 2015 · Ocean Engineering
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    ABSTRACT: Measurement of body temperature provides relevant data on postmortem interval, and different studies have been so far attempted to apply temperature assessment methods also under extreme environmental conditions; however, none of them has been performed yet on charred or heated bodies, where temperature measurement is presumed to be unreliable because of the possible influence of heating. This study aimed at verifying any possible early-stage alterations of rectal and endocranial temperature due to fire on an animal model during the charring process.Three pigs, 2 adults (pigs 1 and 2) whose weight was about 50 kg each and 1 piglet weighing 3 kg, were heated and burnt on a natural fire lit on top of a wooden stack, without the use of accelerants; 2 thermocouples were positioned in the rectum and in the cranium to record second-by-second rectal and endocranial temperature values. Results demonstrate that the rectal temperature does not seem to increase in adult pigs for 40 to 50 minutes after the body has been exposed to fire, probably because of the thermal insulating characteristics of the adipose tissue. Therefore, temperature may still be of some help for estimating postmortem interval on heated or burnt cadavers.
    No preview · Article · Jan 2014 · The American journal of forensic medicine and pathology: official publication of the National Association of Medical Examiners
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    ABSTRACT: As literature is poor in functional synthetic cranial models, in this study, synthetic handmade models of cranial vaults were produced in two different materials (a urethane resin and a self-hardening foam), from multiple bone specimens (eight original cranial vaults: four human and four swine), in order to test their resemblance to bone structure in behavior, during fracture formation. All the vaults were mechanically tested with a 2-kg impact weight and filmed with a high-speed camera. Fracture patterns were homogeneous in all swine vaults and heterogeneous in human vaults, with resin fractures more similar to bone fractures. Mean fracture latency time extrapolated by videos were of 0.75 msec (bone), 1.5 msec (resin), 5.12 msec (foam) for human vaults and of 0.625 msec (bone), 1.87 msec (resin), 3.75 msec (foam) for swine vaults. These data showed that resin models are more similar to bone than foam reproductions, but that synthetic material may behave quite differently from bone as concerns fracture latency times.
    No preview · Article · Jul 2013 · Journal of Forensic Sciences
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    ABSTRACT: Fast documentation of complex scenes where accidents or crimes occurred is fundamental not to lose information for post-event analyses and lesson learning. Today 3D terrestrial laser scanning and photogrammetry offer instruments capable of achieving this task. The former allows the fast geometric reconstruction of complex scenes through dense point clouds. Different kinds of instruments can be used according to the size of the area to survey and to the required level of details. The latter can be used for both geometric reconstruction and for photo-realistic texturing of laser scans. While photogrammetry better focuses on small details, laser scanning gives out a more comprehensive view of geometry of whole crime/accident scene. Both techniques can be used for recording a scene just after a crime or a disaster occurred, before the area is cleared out to recover regular activities. Visualization of results through an easy-to-use 3D environment is another import issue to offer useful data to investigators. Here two experiences of crime scene documentation are proposed.
    Full-text · Article · May 2012 · Proceedings of SPIE - The International Society for Optical Engineering
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    ABSTRACT: Identification from video surveillance systems is frequently requested in forensic practice. The "3D-2D" comparison has proven to be reliable in assessing identification but still requires standardization; this study concerns the validation of the 3D-2D profile comparison. The 3D models of the faces of five individuals were compared with photographs from the same subjects as well as from another 45 individuals. The difference in area and distance between maxima (glabella, tip of nose, fore point of upper and lower lips, pogonion) and minima points (selion, subnasale, stomion, suprapogonion) were measured. The highest difference in area between the 3D model and the 2D image was between 43 and 133 mm(2) in the five matches, always greater than 157 mm(2) in mismatches; the mean distance between the points was greater than 1.96 mm in mismatches, <1.9 mm in five matches (p < 0.05). These results indicate that this difference in areas may point toward a manner of distinguishing "correct" from "incorrect" matches.
    No preview · Article · Nov 2011 · Journal of Forensic Sciences
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    ABSTRACT: The aim of this work is to show a new scintigraphic device able to change automatically the length of its collimator in order to adapt the spatial resolution value to gamma source distance. This patented technique replaces the need for collimator change that standard gamma cameras still feature.Monte Carlo simulations represent the best tool in searching new technological solutions for such an innovative collimation structure. They also provide a valid analysis on response of gamma cameras performances as well as on advantages and limits of this new solution.Specifically, Monte Carlo simulations are realized with GEANT4 (GEometry ANd Tracking) framework and the specific simulation object is a collimation method based on separate blocks that can be brought closer and farther, in order to reach and maintain specific spatial resolution values for all source-detector distances.To verify the accuracy and the faithfulness of these simulations, we have realized experimental measurements with identical setup and conditions. This confirms the power of the simulation as an extremely useful tool, especially where new technological solutions need to be studied, tested and analyzed before their practical realization.The final aim of this new collimation system is the improvement of the SPECT techniques, with the real control of the spatial resolution value during tomographic acquisitions. This principle did allow us to simulate a tomographic acquisition of two capillaries of radioactive solution, in order to verify the possibility to clearly distinguish them.
    Full-text · Article · Sep 2010 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
  • Lorenzo Comolli · Remo Sala
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    ABSTRACT: Mechanical calibration and alignment are fundamental steps in the development of any new aerial photogrammetric scanner. One aim of a film scanner in the digital era is to digitise the accumulated historic archives of images belonging to photogrammetric institutes. The present analysis is centred on a scanner with a translating 2D array camera. Two phases of equal importance can be outlined: the first phase is the alignment of all the mechanical parts inside the scanner, and the second is mechanical calibration, when the systematic effects in the camera positioning are measured and compensated. Among the design requirements of this scanner was to avoid the need for geometrical modification of the scanned images: they should be acquired in the correct position and not require a posteriori correction with a software routine. The proposed solutions lead to a final result of a metrologically satisfactory scanner with a geometric uncertainty of 2...μm or less throughout the frame (250...mm....×....250....mm), a value definitely smaller than the pixel size (10...μm/pixel). © 2010 The Authors. Journal Compilation © 2010 The Remote Sensing and Photogrammetry Society and Blackwell Publishing Ltd.
    No preview · Article · Jun 2010 · The Photogrammetric Record
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    ABSTRACT: This work explores the effect of sensor fill-factor, acquisition noise and blurring level on sub-pixel edge detection uncertainty and finally proposes a new edge detection algorithm to reduce the measurement uncertainty. Optics analysis demonstrates that the intensity profile of an edge, acquired with a digital camera, has the mathematical shape of the error function (erf). The erf is therefore expected to be the best function to fit the intensity profiles of edges. The position of the edge is then estimated through the position of the flex of the approximating curve. However, the hyperbolic tangent can be used to fit the erf with a low discrepancy, though requiring a lower computation time. For this reason the hyperbolic tangent was selected to implement the proposed edge detection algorithm. This algorithm was tested using both numerically generated images and real data. Results demonstrated the efficiency of the proposed algorithm, strongly reducing sub-pixel edge detection systematic effect.
    No preview · Article · Oct 2009 · Measurement
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    ABSTRACT: The paper describes a procedure aimed at identification from two-dimensional (2D) images (video-surveillance tapes, for example) by comparison with a three-dimensional (3D) facial model of a suspect. The application is intended to provide a tool which can help in analyzing compatibility or incompatibility between a criminal and a suspect's facial traits. The authors apply the concept of "geometrically compatible images". The idea is to use a scanner to reconstruct a 3D facial model of a suspect and to compare it to a frame extracted from the video-surveillance sequence which shows the face of the perpetrator. Repositioning and reorientation of the 3D model according to subject's face framed in the crime scene photo are manually accomplished, after automatic resizing. Repositioning and reorientation are performed in correspondence of anthropometric landmarks, distinctive for that person and detected both on the 2D face and on the 3D model. In this way, the superimposition between the original two-dimensional facial image and the three-dimensional one is obtained and a judgment is formulated by an expert on the basis of the fit between the anatomical facial districts of the two subjects. The procedure reduces the influence of face orientation and may be a useful tool in identification.
    Preview · Article · Jul 2009 · Deutsche Zeitschrift für die Gesamte Gerichtliche Medizin
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    ABSTRACT: A new measuring system was developed at the Mechanical Department of the Politecnico di Milano to measure displacements of aeroelastic models during wind tunnel experiments relying on image processing. The system is able to track the variation of the 3D coordinates of model's points that are identified post processing the images recorded by CCD digital cameras using an active stereoscopic vision technique. The measuring system is described in the present paper and some applications to different wind tunnel applications are reported in order to show the system peculiarities and to discuss the advantages of a similar techniques in comparison to other traditional systems.
    No preview · Article · Jan 2009
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    ABSTRACT: This paper deals with the study of a system prototype that can be used as an auxiliary tool in radioguided surgery methods. The use of new technologies in radioguided surgery concern the exact positioning of the lesion to be exerted. This is possible, in operation theatre, thanks to portable scintigraphics devices or to radiation counters. Due to lack of a coordinate system in the operation field, it is difficult for the surgeon to localize the pathology after removing the detection instrument. The system proposed in this paper is composed mainly of three elements: a handheld, high-resolution gamma camera with a small Field Of View (FOV) based on Hamamatsu R8900-00-C12 Position Sensitive Photomultiplier Tube (PSPMT), a laser scanner for the reconstruction of the body district and a stereoscopic system for contactless surgical tool tracking. Analyzing a set of scintigraphic images, taken from different projections, it is possible to localize the three-dimensional position of the lesion. Thanks to the use of the scanner and image fusion techniques, the pathology is shown on a PC monitor correctly positioned with respect to the body surface. Using a couple of stereoscopic cameras, the surgical tool can be tracked and shown on the same monitor, so that the surgeon can know the instantaneous relative position between the tool and the pathology. Exploiting these systems, a navigation system prototype has been developed that is suitable for radioguided surgical application.
    Full-text · Article · Dec 2007 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    ABSTRACT: The article describes a method developed and applied by the authors for the purpose of determining the height of subjects taped on video surveillance systems. The determination of height is obtained by developing a virtual telecamera having the same characteristics of the video surveillance system with which the images have been shot. The results demonstrate that height is a parameter that can be accurately estimated with the method proposed, in the experimental conditions described, and consequently, can be utilized in probatory inquiry.
    Full-text · Article · Dec 2007 · Deutsche Zeitschrift für die Gesamte Gerichtliche Medizin
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    ABSTRACT: 1.Introduction The nuclear medicine imaging is a technique based on functional, rather than morphological, information. To this aim, a properly dimensioned scintigraphic device is attractive to "probe" small lesions location in diagnostic and bioptic modalities. Imaging Probes (IP) have to be small, portable, low cost, real time scintigraphic systems that yield high-resolution images on a small field of view (FOV), even in intra-operatorial modality. In order to minimize the patient and operator radiation exposure, Imaging Probe should operate with small doses of low energy gamma emitter (typically 99m Tc). Both the prototypical and final version of the IP-824 device, produced by Li-tech, were designed with the aid of computer simulations and successfully used as localization devices [1-2] in cancer breast biopsy and sentinel node detection [3-4]. Thyroid nodules are lumps which common arise within an otherwise normal thyroid gland and frequently manifest only benign behavior. Physician bases diagnoses on ultrasound morphological probing, examination and Thyroids Fine Needle Aspiration (FNA). Anger camera scintigraphy could furnish functional information in the case of almost evident lesion (1 cm of diameter). The use of the IP, with its improved resolution, could help to establish nature and position of small dimension thyroidal nodules. Aim of this work is to report Monte Carlo simulation results of lesion localization based on a triangulation procedure. The entire IP collimation and scintillation array detector system, along with an elementary thyroidal digital phantom, were set up on a Monte Carlo N particles (MCNP) input deck [5]. The simulation results allow general consideration on the trade off between lesion dimension and mechanical requirements in the triangulation procedure. This study could be also considered as preliminary investigation on the potentiality of the IP-824 device as "building units" for fast tomographic systems. 2. Model assumption The study was focused on a relatively simple phantom that yields an unambiguous response on the simulated IP-824 acquisition mechanisms. In the following model radiation transport from the phantom distributed gamma source, collimation, detailed mechanisms of energy deposition in scintillating crystals, image rendering, and localization procedure were simulated by a calculation chain along MCNP code and other dedicated codes. The next three sections illustrate, in more details, the assumption of each of the distinct task. In all the simulations the effects of the different stages of the nuclear electronic (Photo-multiplication, Amplification, Analog to Digital conversion) weren't taken into account. 2.1 Monte Carlo transports. MCNP is a general-purpose code for the coupled transport of neutrons, photons and electrons. It allows a detailed description of the problem geometry and, by using a complete set of continuous cross sections, to locate user defined materials into specific zones of that geometry (cells).
    Full-text · Conference Paper · Jun 2004
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    ABSTRACT: Since 1999 our group started with practical experience on diagnostic use of small, transportable prototypes of high-resolution gamma cameras (patented) for radioguided surgery: the Imaging Probe (IP). First experiences allowed us to develop dedicated prototypes for specific applications. At the moment the most intriguing field is guiding biopsy. Dedicated detectors, characterized by low cost and weight, allow to transfer imaging where the biopsy has to be done. In this paper, a new combined application for breast cancer detection is described. In present system IP is put inside a Fisher digital stereotactic device prepared for Mammotome biopsy: so biopsy can contemporaneously be driven by X-ray stereotaxis and 99mTc-Sestamibi (MIBI) images from IP. The Field Of View (FOV) is about 2×2 cm2 and 0.8 kg weight. This novel scintillation camera is based upon the compact Hamamatsu R7600-00-C8 Position Sensitive Photomultiplier Tube (PSPMT), coupled to scintillating arrays. The PSPMT can be arranged as array when larger FOV is needed.Present application was provided with off line software for image fusion running on the IP dedicated PC. It was matched with the Fisher digital stereotactic X-ray device dedicated to address Mammotome (Ethicon Endo-surgery by Johnson and Johnson) towards breast opacities. Spatial resolution of the IP was 2.5 mm Full-Width Half-Maximum (FWHM) at laboratory tests. A preliminary IP–X-ray digital system inter-calibration was performed using a Perspex-lead phantom. 99mTc MIBI was injected at the dose of 740 MBq 1 h before biopsy to three patients with breast opacities of respectively 0.6, 0.8 and 1.5 cm, scheduled for Mammotome biopsy. Sixty-four pixel scintigraphic images were acquired before and after biopsy in each patient. Operator was allowed to slightly correct the direction of the Mammotome needle taking into account stereotactic X-ray, scintigraphic and fused images. Bioptic samples were also counted with IP before sending them to pathologist.High-resolution IP scintigraphy showed substantial, though not exact, matching between MIBI hot spots and X-ray opacities. More than one hot spot were detected even in the smallest 0.6 cm lesion. Post biopsy scintigraphy showed absence of significant hot spots in two patients, whereas in the third one of the three hot spots still was partially present. All the lesions showed cancer at histological exam. Measurement of radioactivity on biopsy specimens confirmed the heterogeneous distribution of radioactivity within cancers that IP had detected before biopsy. Or study confirms the ability of IP to guide biopsy or anyway to correct X-ray stereotactic drive.
    Full-text · Article · Jan 2003 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    Alfredo Cigada · Remo Sala · Emanuele Zappa
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    ABSTRACT: Image based measurement techniques allow for quick and contact-less measurement of single or multiple target displacement, shape, orientation and so on. The sub-pixel analysis increases the vision based displacement resolution. In the present paper resolution and uncertainty of 1D camera based displacement measurements is analysed, paying particular attention to the target geometry effect on the results. Comparison between camera based and laser interferometer displacement measurement is performed and some target modifications are tried, in order to reduce measurement uncertainty, due to sub-pixel systematic effect; the use of including the systematic effect into uncertainty, is wrong in theory but in practise often justified by the usual need of coarse and speed measurements. The uncertainty in target displacement estimation given by three different image analysis algorithms is also tested in the case of rectangular, rhomboidal and circular targets. 1. SYSTEMATIC EFFECT IN SUB-PIXEL ANALYSIS Image processing is becoming one among the most common techniques in industrial process control and contactless measurement technique: this is mainly due to the increasing CPU capabilities, to the improvements in CCD sensors and the related electronics, and to the new post-processing image algorithms. The main purpose of this paper is to look for a metrological qualification of a camera, as a displacement transducer. This is due to the fact that the above mentioned improvements have pulled image processing to performances comparable to those of some more traditional, well known and frequently used transducers. In order to obtain accurate measurements both resolution and uncertainty must be considered because, as stated in Italian standard [1], high resolution is useless if uncertainty is larger than the resolution. In order to improve the resolution capabilities of an image-based measurement system, two approaches are possible: increasing the CCD resolution (i.e. increasing the total number of pixels, but this usually contrasts with the dynamic properties) or applying a sub-pixel image processing. The number of pixels can be increased only up to a certain level, depending on the technical development of the CCD sensors, and imply an increase of the system cost. On the other hand, using a sub-pixel algorithm does not require a hardware improvement and it is usually cheaper. Of course both the pixel number increasing and the sub-pixel analysis can be applied together. Even if applying sub-pixel analysis the available resolution of the vision-based measurement device can be very high (some software houses state that the maximum resolution obtainable using their routines is 1/50 of the pixel size, sometimes without explaining wich algorithm is applied), the uncertainty of the measured displacements is often worse ([2]), vanishing the resolution capabilities ([1]). It is in fact known in literature that, applying sub-pixel algorithms, a systematic effect is introduced in the measured data.
    Full-text · Article · Jan 2003
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    ABSTRACT: The present paper describes the advantages of the combined use of morphologic and functional diagnostic images for improving the accuracy in pathology localization. The main goal of the position uncertainty reduction is to carefully select the area of interest for the biopsy. The paper describes the new diagnostic technique based on the synergic use of morphologic and functional diagnostic images and shows examples images obtained during breast stereotactic biopsy on some patients.
    Full-text · Article · Jan 2003
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    ABSTRACT: The "Imaging Probe" (IP) is a small, portable, high-resolution gamma camera to be used in radioguided surgery. The present work discusses a special prototype designed for guiding biopsies. The IP was mounted to a Fischer digital X-ray stereotactic core biopsy system in such a way that biopsy could be guided simultaneously by X-ray stereotaxis and 99mTc-Sestamibi (MIBI) images from IP. The IP field of view was 22.8 x 22.8 mm(2), with a spatial resolution of approx. 2.5 mm. We used off-line software for image fusion on a dedicated Pentium III portable PC. It was matched with a Fischer digital X-ray stereotactic biopsy system dedicated to direct the mammotome towards breast opacities. The operator was allowed to slightly correct the direction of the mammotome needle taking into account stereotactic X-ray, scintigraphic and fused images. Biopsy samples were counted by IP before they were sent to the pathologist. High-resolution IP scintigraphy showed substantial, though not exact, matching between MIBI hot spots and X-ray opacities. More than one hot spot was detected even in the smallest (0.6 cm) lesion. Post-biopsy scintigraphy showed absence of significant hot spots in two patients, whereas in the third patient one of the three hot spots was still partially present. All lesions showed cancer on histological examination. Measurement of radioactivity in biopsy specimens confirmed the heterogeneous distribution of radioactivity within cancers that IP had detected before biopsy.
    No preview · Article · May 2002 · Tumori
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    ABSTRACT: The present work is aimed at defining a repeatable procedure for evaluating the "quality" of the measurement results in the field of face-based personal recognition. The problem of the minimum requirement on source image metrological features is also accounted for in order to avoid useless calculation and possibly misleading results in case of images with too low information content.
    Full-text · Article · Jul 0002