Fusion of range camera and photogrammetry: a systematic procedure for improving 3-D models metric accuracy

The generation of three-dimensional (3-D) digital models produced by optical technologies in some cases involves metric errors. This happens when small high-resolution 3-D images are assembled together in order to model a large object. In some applications, as for example 3-D modeling of Cultural Heritage, the problem of metric accuracy is a major issue and no methods are currently available for enhancing it. The authors present a procedure by which the metric reliability of the 3-D model, obtained through iterative alignments of many range maps, can be guaranteed to a known acceptable level. The goal is the integration of the 3-D range camera system with a close range digital photogrammetry technique. The basic idea is to generate a global coordinate system determined by the digital photogrammetric procedure, measuring the spatial coordinates of optical targets placed around the object to be modeled. Such coordinates, set as reference points, allow the proper rigid motion of few key range maps, including a portion of the targets, in the global reference system defined by photogrammetry. The other 3-D images are normally aligned around these locked images with usual iterative algorithms. Experimental results on an anthropomorphic test object, comparing the conventional and the proposed alignment method, are finally reported.

The usefulness of holding in the management of congenital heart disease

BACKGROUND

In our Pediatric Cardiology Unit we have implemented a number of specific interventions in order to support parents and their children who have congenital heart disease. We paid particular attention about how communicating the diagnosis and how supporting psychologically the parents.

METHODS

In order to check the validity of these interventions we used the State-Trait Anxiety Inventory to analyze and compare the anxiety levels of 380 parents of already established patients here in the hospital to the anxiety levels of 240 parents of children seen in our unit for the first time (for screening or evaluating anomalous symptoms).

RESULTS

Our analysis shows that during daily life the seriousness of the disease affects parents adversely (the "anxiety trait" in parents of children with cyanotic congenital heart disease has a higher rate than other parents, p < .05). While waiting for medical assessment, the parents of children with a previous diagnosis of congenital heart disease or those with symptomatic children live an increment of the level of anxiety (the "anxiety state" has a higher score than the "anxiety trait", p < .001), but the "anxiety state" of parents of children with congenital heart disease has a lower rate in respect to parents of symptomatic children (p < .001).

CONCLUSIONS

Thus adequate interventions, specifically an effective communication in a comfortable environment, can reduce anxiety of parents while waiting for medical assessment. It is very important as the child's psychological wellbeing is very directly related to the emotional state of the parents.

Detection of vascular haemodynamics through a high-speed velocity profiler

OBJECTIVE

This paper aims at demonstrating that ultrasound Doppler multigate spectral analysis performed with advanced equipment may provide detailed and significant haemodynamic information.

METHODS

A novel multigate system was recently introduced and shown capable of performing real-time spectral analysis of Doppler data from 64 resolution cells located at different depths from the transducer. The system extends the typical capabilities of conventional Pulsed Wave (PW) equipment by displaying the full spectral content of Doppler signals over an ultrasound scan line rather than in a single resolution cell. In cases where it is appropriate to display the available information in a simpler form, parameters such as the maximum frequency can be extracted from each spectrum, by using conventional or advanced image processing methods.

RESULTS

In-vitro experiments show that the multigate system can perform velocity measurements with good accuracy and precision. Examples of in vivo profiles detected from carotid, femoral and radial arteries are presented. In particular, the first results obtained from the aorta are shown.

CONCLUSIONS

Blood flow behavior can be accurately investigated using a real-time multigate system which extends Doppler spectral analysis to a whole scan line.

Synchronous dynamic focusing for ultrasound imaging

An approach to dynamic focusing of ultrasound linear array scanners is presented, leading to the unique capability of implementing a focus that continuously tracks the return signal along the penetration depth. An electronically variable lens is obtained by a heterodyning process, in which the phases of echo signals at the array elements are equalized by mixing with suitable reference oscillations. These are generated by control of a single voltage-controlled oscillator, whose frequency is properly varied in synchronism with the delay of signal from different depths. The technique has been experimentally demonstrated by modifying the focusing processor of a conventional echographic linear scanner. Superior performances have been obtained with respect to fixed-focus operation mode. The image quality results are comparable with those of multizone-focus operation mode, in which the focus is varied over more transmit/receive cycles at the expense of lower frame rate.

Blood flow images by a SAW-based multigate Doppler system

Multigate operation of an ultrasound pulsed Doppler flowmeter, providing Doppler frequency detection in a number of adjacent sample volumes, is capable of displaying the instantaneous blood velocity distribution along the cross section of a sonified vessel. Real-time serial Doppler processing of 32 range cells has been implemented in a novel system using fast spectral analysis based on surface-acoustic wave (SAW) dispersive filters. The basic architecture and first in vitro experiments were reported previously. The in vivo application of the system is described here, and images of human carotid artery and jugular vein are presented. Appropriate display formats are introduced to use the great amount of information known on spatial and temporal behavior of flow profiles. Digital postprocessing of spectral Doppler data allows velocity profiles to be displayed at selected times to correlate spatial and temporal evolution. A color code can be used to represent different velocity strengths. The potential application of the system to two-dimensional (2-D) flow imaging is discussed.

Optical signal processing by filtering fresnel images of acoustic light modulators

Spatial filtering of the instantaneous interference pattern displayed by an ultrasonic light modulator (ULM) in a plane of its Fresnel diffraction field was recently devised as a means of achieving real-time optical signal processing. This approach has been used to obtain the correlation of an electric signal, propagated in a ULM, by filtering a Fresnel image of the acoustic wave through an amplitude replica of the expected waveform, recorded on an optical mask. Careful investigation of the ULM interference patterns is needed, however, since Fresnel images vary with the distance from the ULM, and, accordingly, the correlator response critically depends on the ULM-signal replica separation. In this paper the interference patterns formed by a ULM fed with a linear FM signal are analyzed, and the performance of the device is investigated by computing the correlation response as a function of the ULM-replica separation.