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J J Vidal

Publications and source records attributed to J J Vidal.

26 records · Page 2Linked to original sources
PubMedDate not supplied

A low-cost system for digital image processing of moving images in real time: application to X-ray fluoroscopy.

A low-cost image processing system and two real-time digital image processing algorithms using parallel processing have been developed to provide automatic equalization of moving images at video frequencies. The algorithms differ in the processing time required and the characteristics of the final image. The system takes an entire image from the video sequence, digitizes it, automatically calculates its histogram and the lowest and highest useful grey levels, equalizes the histogram, and finally converts it to the analogue image. Methods were applied to X-ray fluoroscopy (angiography) images, which are usually saturated or of uniform intensity (low contrast), leading to information loss. An application of these methods is in interventional radiography, which requires images in real time.

Algorithms↗
PubMedDate not supplied

Evaluation of an automated wavelet-based system dedicated to the detection of clustered microcalcifications in digital mammograms.

Mammographic screening programs are delivering reductions in breast cancer mortality. However, breast cancer screening will be cost effective and will provide a real profit only when both high sensitivity and specificity levels are reached. To date, due to human or technical factors, a significant number of breast cancers are still missed or misinterpreted on the mammograms. Computer methodologies, developed to assist radiologists, could represent further amelioration by increasing diagnostic accuracy in the screening programs. We have tested a computerized scheme to detect clustered microcalcifications in digital mammograms, employing 360 mammograms that were randomly selected from the mammographic screening program, currently undergoing at the Galicia Community (Spain). After the digitization process, the breast border was initially determined. A wavelet-based algorithm was employed to detect the clusters of microcalcifications. The performance of the automated system over the test set was evaluated employing Free-response Receiver Operating Characteristic (FROC) methodology. The sensitivity achieved was 74% at a false positive detection rate of 1.83. The corresponding area under the Alternative FROC (AFROC) curve was A1=0.667 +/-0.09.

Algorithms↗
PubMedDate not supplied

Acute lobar collapse in canine lungs.

A series of experiments was carried out on 28 dogs in which the following aspects were investigated: in 9 dogs, the special configuration of acute lobar atelectasis; in 10 dogs, the pressure-volume characteristics of collapsed and non-collapsed diaphragmatic lobes; in 12 dogs, the wet-weight/dry-weight ratios of atelectatic contralateral lobes; in 6 dogs, the amount of blood sequestered in atelectatic diaphragmatic lobes was estimated. The relationships of an atelectic lobe closely resemble those described in man. Loss of apposition between visceral and parietal pleural surfaces was never observed. The W/D weight ratio of the collapsed lobe invariably was higher than that of the non-collapsed contralateral lobe indicating a slight increase in the volume of fluid in the atelectatic lobe. No pressure-volume differences were found between atelectatic and non-collapsed lobes.

Acute Disease↗
PubMedDate not supplied

A limited PACS dedicated to a research environment. Nine years' experience in Santiago de Compostela.

A digital image network has been installed at the Department of Radiology of the University of Santiago de Compostela, Spain, to create a "limited' Picture Archiving and Communication System (PACS). This experience is being dedicated to address problems associated with digital techniques in a research environment. The backbone of the system is a multiprotocol ethernet network. Attached to the network are a number of advanced devices such as DEC VAX and UNIX workstations. Currently, a high resolution film digitizer and a laser printer are under evaluation for radiologic image research. During a period of nine years, 1987 to 1995, experimental and clinical trials have been conducted on different film based digital radiography apparatus primarily dedicated to chest and breast imaging. Several research projects have been completed. In this paper we describe the results of these investigations and discuss the advantages and disadvantages of this digital technique. The results of the different completed studies will be presented separately. A description of the physical characteristics of the limited PACS system dedicated to a research environment will serve as background.

Computer Communication Networks↗