Medical image registration is a highlight of actual research on medical image processing. It play an important role in clinical diagnoses and treating.Mutul information has been deeply researched and popularly applied in image registration. We discuss the principle, virtue, p- rogress and improvement of mutual information(MI). At last, other two similarity measures, a normalized similarity measure based on Jensen′s difference and f-information, are analyzede.

A survey of medical image registration

The development of portable gamma-ray imaging instruments in combination with the recent advances in sensor and related computer vision technologies enable unprecedented capabilities in the detection, localization, and mapping of radiological and nuclear materials in complex environments relevant for nuclear security and safety. Though multi-modal imaging has been established in medicine and biomedical imaging for some time, the potential of multi-modal data fusion for radiological localization and mapping problems in complex indoor and outdoor environments remains to be explored in detail. In contrast to the well-defined settings in medical or biological imaging associated with small field-of-view and well-constrained extension of the radiation field, in many radiological search and mapping scenarios, the radiation fields are not constrained and objects and sources are not necessarily known prior to the measurement. The ability to fuse radiological with contextual or scene data in three dimensions, in analog to radiological and functional imaging with anatomical fusion in medicine, provides new capabilities enhancing image clarity, context, quantitative estimates, and visualization of the data products. We have developed new means to register and fuse gamma-ray imaging with contextual data from portable or moving platforms. These developments enhance detection and mapping capabilities as well as provide unprecedented visualization of complex radiation fields, moving us one step closer to the realization of gamma-ray vision in three dimensions.

Gamma-Ray imaging for nuclear security and safety: Towards 3-D gamma-ray vision

Gamma-Ray Bursts

A prototype of hybrid gamma imager has been developed, based on a single Timpex3 readout chip hybridized with a 1 mm thick cadmium telluride semiconductor. This prototype combines coded-aperture imaging spectrometry and Compton imaging techniques to perform hybrid gamma imaging. It associates and takes advantage of both techniques to locate gamma emitters. The prototype is designed to be portable and compact in order to ease its field use. In this work, we present experimental results obtained with this prototype in coded-aperture imaging spectrometry mode, Compton imaging mode, and hybrid gamma imaging.

Development of a hybrid gamma camera based on Timepix3 for nuclear industry applications

Development of hand-held coded-aperture gamma ray imaging system based on GAGG(Ce) scintillator coupled with SiPM array

The results of more than 280 different experiments aimed at exploring the main features and performances of a newly developed gamma imager, called iPIX, are summarized in this paper. iPIX is designed to quickly localize radioactive sources while estimating the ambient dose equivalent rate at the measurement point. It integrates a 1 mm thick CdTe detector directly bump-bonded to a Timepix chip, a tungsten coded-aperture mask, and a mini RGB camera. It also represents a major technological breakthrough in terms of lightness, compactness, usability, response sensitivity, and angular resolution. As an example of its key strengths, an 241Am source with a dose rate of only few nSv/h can be localized in less than one minute.

/pdf/a-comprehensive-experimental-characterization-of-the-ipix-11zo0vvfjv.pdf

A comprehensive experimental characterization of the iPIX gamma imager

A known disadvantage of the coded aperture imaging approach is its limited field-ofview (FOV), which often results insufficient when analysing complex dismantling scenes such as post-accidental scenarios, where multiple measurements are needed to fully characterize the scene. In order to overcome this limitation, a panoramic coded aperture γ-camera prototype has
been developed. The system is based on a 1 mm thick CdTe detector directly bump-bonded to a Timepix readout chip, developed by the Medipix2 collaboration (256 × 256 pixels, 55 µm pitch, 14.08 × 14.08 mm2 sensitive area). A MURA pattern coded aperture is used, allowing for background subtraction without the use of heavy shielding. Such system is then combined with a USB color camera. The output of each measurement is a semi-spherical image covering a FOV of 360 degrees horizontally and 80 degrees vertically, rendered in spherical coordinates (θ,φ). The geometrical shapes of the radiation-emitting objects are preserved by first registering and stitching the optical images captured by the prototype, and applying, subsequently, the same transformations to their corresponding radiation images. Panoramic gamma images generated by using the technique proposed in this paper are described and discussed, along with the main experimental results obtained in laboratories campaigns.

/pdf/a-panoramic-coded-aperture-gamma-camera-for-radioactive-5aj0bd3d3k.pdf

A panoramic coded aperture gamma camera for radioactive hotspots localization

The present paper proposes a versatile procedure for the geometrical calibration of coded aperture gamma cameras and RGB-D depth sensors, using only one radioactive point source and a simple experimental set-up. Calibration data is then used for accurately aligning radiation images retrieved by means of the γ -camera with the respective depth images computed with the RGB-D sensor. The system resulting from such a combination is thus able to retrieve, automatically, the distance of radioactive hotspots by means of pixel-wise mapping between gamma and depth images. This procedure is of great interest for a wide number of applications, ranging from precise automatic estimation of the shape and distance of radioactive objects to Augmented Reality systems. Incidentally, the corresponding results validated the choice of a perspective design model for a coded aperture γ -camera.

A versatile calibration procedure for portable coded aperture gamma cameras and RGB-D sensors

Erratum: A comprehensive experimental characterization of the iPIX gamma imager

A portable stereo gamma camera has been built, based on two hybrid pixelated detectors, each of them comprising a 1 mm thick CdTe substrate bump-bonded to the Timepix readout chip, a pixelated CMOS ASIC consisting of 256 × 256 pixels with 55 µm pitch. The technique described in this paper allows the automatic estimation of the distances between the prototype and the located radioactive sources by using triangulation based on epipolar geometry. The 3-D Cartesian coordinates of the sources are provided even when they are hidden behind an occluding material, such as a wall, or inside a barrel. Furthermore, the combination of the prototype with a depth sensor enables a wide range of applications, including the 3-D volumetric reconstruction of the scene under study as well as the capability of autonomously determining if an object is occluding the located radioactive sources. We discuss here the main features of the whole methodology developed and we also present the experimental results obtained at laboratory scale.

3-D localization of radioactive hotspots via portable gamma cameras

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