Biomedical subjects

Miguel Souto

Publications and source records attributed to Miguel Souto.

4 recordsLinked to original sources

PubMed2005

Free-response receiver operating characteristic evaluation of lossy JPEG2000 and object-based set partitioning in hierarchical trees compression of digitized mammograms.

PURPOSE: To assess the effects of two irreversible wavelet-based compression algorithms--Joint Photographic Experts Group (JPEG) 2000 and object-based set partitioning in hierarchical trees (SPIHT)--on the detection of clusters of microcalcifications and masses on digitized mammograms. MATERIALS AND METHODS: The use of the images in this retrospective image-collection study was approved by the institutional review board, and patient informed consent was not required. One hundred twelve mammographic images (28 with one or two clusters of microcalcifications, 19 with one mass, 17 with both abnormal findings, and 48 with normal findings) obtained in 60 women who ranged in age from 25 to 79 years were digitized and compressed at 40:1 and 80:1 by using the JPEG2000 and object-based SPIHT methods. Five experienced radiologists were asked to locate and rate clusters of microcalcifications and masses on the original and compressed images in a free-response receiver operating characteristic (FROC) data acquisition paradigm. Observer performance was evaluated with the jackknife FROC method. RESULTS: The mean FROC figures of merit for detecting clusters of microcalcifications, masses, and both radiographic findings on uncompressed images were 0.80, 0.81, and 0.72, respectively. With object-based SPIHT 80:1 compression, the corresponding values were larger than the values for uncompressed images by 0.005, 0.009, and -0.005, respectively. The 95% confidence interval for the differences in figures of merit between compressed and uncompressed images was -0.039, 0.033 for the microcalcification finding; -0.055, 0.034 for the mass finding; and -0.039, 0.030 for both findings. Because each of these confidence intervals includes zero, no significant difference in detection accuracy between uncompressed and object-based SPIHT 80:1 compression was observed at a P value of 5%. The F test of the null hypothesis that all of the modes (uncompressed and four compressed modes) were equivalent yielded the following results: F = 0.255, P = .903 for the microcalcification finding; F = 0.340, P = .848 for the mass finding; and F = 0.122, P = .975 for both findings. CONCLUSION: To within the accuracy of these measurements, lossy compression of digital mammographic data at 80:1 with JPEG2000 or the object-based SPIHT algorithm can be performed without decreasing the rate of detection of clusters of microcalcifications and masses.

Adult↗

PubMed2003

A high resolution workstation prototype for diagnosis of digital mammograms.

The development of a total digital high resolution mammography display system must meet a number of requirements that remain a challenge nowadays, most probably because of the special nature of breast imaging. In this paper, we discuss our particular approach to address some problems concerning the complexity of soft-copy diagnosis in digital mammography, such as image quality and user interface evaluation. Based on the experience obtained in the previous implementation of a medical image browser, a more ambitious project is being developed at the Department of Radiology of the University of Santiago de Compostela (Spain) in collaboration with the Department of Medical Informatics of INTELSIS, an emerging software company in our country. This new system will provide complete support to display, store and analyze mammographic studies in digital format.

Mammography↗

PubMed2003

Region-based wavelet coding methods for digital mammography.

Spatial resolution and contrast sensitivity requirements for some types of medical image techniques, including mammography, delay the implementation of new digital technologies, namely, computer-aided diagnosis, picture archiving and communications systems, or teleradiology. In order to reduce transmission time and storage cost, an efficient data-compression scheme to reduce digital data without significant degradation of medical image quality is needed. In this study, we have applied two region-based compression methods to digital mammograms. In both methods, after segmenting the breast region, a region-based discrete wavelet transform is applied, followed by an object-based extension of the set partitioning in hierarchical trees (OB-SPIHT) coding algorithm in one method, and an object-based extension of the set partitioned embedded block (OB-SPECK) coding algorithm in the other. We have compared these specific implementations against the original SPIHT and the new standard JPEG 2000, both using reversible and irreversible filters, on five digital mammograms compressed at rates ranging from 0.1 to 1.0 bit per pixel (bbp). Distortion was evaluated for all images and compression rates by the peak signal-to-noise ratio. For all images, OB-SPIHT and OB-SPECK performed substantially better than the traditional SPIHT and JPEG 2000, and a slight difference in performance was found between them. A comparison applying SPIHT and the standard JPEG 2000 to the same set of images with the background pixels fixed to zero was also carried out, obtaining similar implementation as region-based methods. For digital mammography, region-based compression methods represent an improvement in compression efficiency from full-image methods, also providing the possibility of encoding multiple regions of interest independently.

Algorithms↗

PubMedDate not supplied

Computer aided diagnosis for breast masses detection on a telemammography system.

A Computer-Aided Diagnosis (CAD) scheme for breast masses detection has been developed and integrated as a part of a telemammography system. This work derives from the close cooperation between the Laboratory for Radiologic Image Research of the University of Santiago de Compostela (Spain) and the company Intelsis Sistemas Inteligentes (Santiago de Compostela, Spain). This cooperation has been supported by funds from different projects, mainly from the European Union, the Spanish Health Administration, and the Galician Public Health's Service. As a result, a first prototype is ready to begin a demonstration project.

Female↗