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Biomedical subjects

F Murtagh

Publications and source records attributed to F Murtagh.

At least 19 recordsLinked to original sources
PubMed2001

Image matching algorithms for breech face marks and firing pins in a database of spent cartridge cases of firearms.

On the market several systems exist for collecting spent ammunition data for forensic investigation. These databases store images of cartridge cases and the marks on them. Image matching is used to create hit lists that show which marks on a cartridge case are most similar to another cartridge case. The research in this paper is focused on the different methods of feature selection and pattern recognition that can be used for optimizing the results of image matching. The images are acquired by side light images for the breech face marks and by ring light for the firing pin impression. For these images a standard way of digitizing the images used. For the side light images and ring light images this means that the user has to position the cartridge case in the same position according to a protocol. The positioning is important for the sidelight, since the image that is obtained of a striation mark depends heavily on the angle of incidence of the light. In practice, it appears that the user positions the cartridge case with +/-10 degrees accuracy. We tested our algorithms using 49 cartridge cases of 19 different firearms, where the examiner determined that they were shot with the same firearm. For testing, these images were mixed with a database consisting of approximately 4900 images that were available from the Drugfire database of different calibers.In cases where the registration and the light conditions among those matching pairs was good, a simple computation of the standard deviation of the subtracted gray levels, delivered the best-matched images. For images that were rotated and shifted, we have implemented a "brute force" way of registration. The images are translated and rotated until the minimum of the standard deviation of the difference is found. This method did not result in all relevant matches in the top position. This is caused by the effect that shadows and highlights are compared in intensity. Since the angle of incidence of the light will give a different intensity profile, this method is not optimal. For this reason a preprocessing of the images was required. It appeared that the third scale of the "à trous" wavelet transform gives the best results in combination with brute force. Matching the contents of the images is less sensitive to the variation of the lighting. The problem with the brute force method is however that the time for calculation for 49 cartridge cases to compare between them, takes over 1 month of computing time on a Pentium II-computer with 333MHz. For this reason a faster approach is implemented: correlation in log polar coordinates. This gave similar results as the brute force calculation, however it was computed in 24h for a complete database with 4900 images.A fast pre-selection method based on signatures is carried out that is based on the Kanade Lucas Tomasi (KLT) equation. The positions of the points computed with this method are compared. In this way, 11 of the 49 images were in the top position in combination with the third scale of the à trous equation. It depends however on the light conditions and the prominence of the marks if correct matches are found in the top ranked position. All images were retrieved in the top 5% of the database. This method takes only a few minutes for the complete database if, and can be optimized for comparison in seconds if the location of points are stored in files. For further improvement, it is useful to have the refinement in which the user selects the areas that are relevant on the cartridge case for their marks. This is necessary if this cartridge case is damaged and other marks that are not from the firearm appear on it.

Algorithms↗
PubMed1995

Dynamical recurrent neural networks--towards environmental time series prediction.

Dynamical Recurrent Neural Networks (DRNN) (Aussem 1995a) are a class of fully recurrent networks obtained by modeling synapses as autoregressive filters. By virtue of their internal dynamic, these networks approximate the underlying law governing the time series by a system of nonlinear difference equations of internal variables. They therefore provide history-sensitive forecasts without having to be explicitly fed with external memory. The model is trained by a local and recursive error propagation algorithm called temporal-recurrent-backpropagation. The efficiency of the procedure benefits from the exponential decay of the gradient terms backpropagated through the adjoint network. We assess the predictive ability of the DRNN model with meterological and astronomical time series recorded around the candidate observation sites for the future VLT telescope. The hope is that reliable environmental forecasts provided with the model will allow the modern telescopes to be preset, a few hours in advance, in the most suited instrumental mode. In this perspective, the model is first appraised on precipitation measurements with traditional nonlinear AR and ARMA techniques using feedforward networks. Then we tackle a complex problem, namely the prediction of astronomical seeing, known to be a very erratic time series. A fuzzy coding approach is used to reduce the complexity of the underlying laws governing the seeing. Then, a fuzzy correspondence analysis is carried out to explore the internal relationships in the data. Based on a carefully selected set of meteorological variables at the same time-point, a nonlinear multiple regression, termed nowcasting (Murtagh et al. 1993, 1995), is carried out on the fuzzily coded seeing records. The DRNN is shown to outperform the fuzzy k-nearest neighbors method.

Environmental Monitoring↗
PubMed1991

Germ cell tumor of testis in a patient with von Hippel-Lindau disease.

Germ cell testicular tumor is a previously undescribed entity in association with von Hippel-Lindau disease. This case exemplifies the variety of pathologic entities encountered in von Hippel-Lindau disease and stresses the importance of thorough evaluation of the patient, as well as careful follow-up, to ensure early detection of potentially malignant lesions.

Adult↗
PubMed1990

Reflections on the anesthesia-neurosurgical alliance.

This is an uncommon article for a modern scientific journal in that it contains no data, it is written in the first person, and it recounts only the personal experiences of a clinical neurosurgeon about the evolution of neurosurgery, anesthesiology, and neuroanesthesiology in Philadelphia from 1939 to 1988, when the surgeon retired from the operating room. The surgeon, Fred Murtagh, practiced neurosurgery during an extraordinarily formative time for American medicine and neurosurgery. He was on the faculty of Temple University for many years and currently is Emeritus Professor of Neurosurgery at the University of Pennsylvania. His observations are from the point of view of a man who has been in the operating room continuously since the early 1940s grappling with the practical problems confronting the neurosurgeon. In addition, he is a highly observant individual and considered by many to be an extraordinary teacher. With respect to the genesis of this article, the neuroanesthesia group at the University of Pennsylvania invited Dr. Murtagh to one of their monthly meetings. A tape recorder was placed in front of him and we were privileged to listen to 2 h of reminiscence about his career and relationships between anesthesiologists and neurosurgeons. Over a several year period, Fred Murtagh and D. S. Smith extracted that tape and wrote the following article. It is my belief that this article, despite its unorthodox format, contains observations of import to clinicians in general and to those who practice the subspecialty of neurosurgical anesthesia.

Journal Article↗
PubMed1986

Comparison of surgical and anesthetic complications in neurosurgical patients experiencing venous air embolism in the sitting position.

Because venous air embolism (VAE) has been considered to be a major deterrent to use of the sitting position, records of 255 patients undergoing neurosurgery in the sitting position from 1975 to 1982 were reviewed to determine the nature of morbidity and mortality in relation to the surgical procedure as well as to the occurrence of VAE. Complications were classified as surgical or anesthetic during joint review by a neurosurgeon and two neuroanesthesiologists. Outcome was classified on the basis of postoperative hospital course and discharge examination. The incidence of VAE was 30%. Although there was a variety of perioperative complications in patients with and without VAE, most of the complications were related to the operative procedure, not the sitting position or VAE. The episodes of VAE did not seem to be significant factors in the perioperative morbidity and mortality in our series of patients operated upon in the sitting position. Two case reports are discussed in detail.

Aged↗
PubMed1981

Cavernous hemangioma in the diencephalon.

A 32-year-old man with a history of delayed puberty and obesity was seen initially with bitemporal hemianopsia and headache in 1974. Neuroradiologic studies showed a mass in the chiasmatic cistern and hypothalamus. Surgical exploration of the chiasm was unrevealing. Slowly progressive memory loss and intellectual impairment developed. Necropsy in 1978 disclosed a large cavernous hemangioma in the diencephalon.

Adult↗
PubMed1978

Spinofacial anastomosis.

Removal of large acoustic neuromas may still be followed by facial nerve palsy. The results of fourteen cases of spinofacial nerve anastomosis have been studied and compared with the results of spinofacial and hypoglossal-facial anastomoses reported in the literature. Other standard treatments of facial palsy have been briefly reviewed and criteria developed by which the most appropriate therapy for facial paralysis may be selected.

Accessory Nerve↗
PubMed1977

Applications of reconstructive craniofacial techniques to acute craniofacial trauma.

Increasing familiarity with elective reconstructive approaches to craniofacial deformity has led to the application of a similar multispecialty approach to repair of selected cases of massive frontal and upper facial trauma. The fundamental steps in craniofacial reconstruction are outlined. The process of patient selection is emphasized. Illustrative case histories review the management of this type of injury. Contributions from anesthesiology, neurosurgery, ophthalmology, and plastic surgery are required. Specialized facilities for postoperative care are mandatory.

Adult↗
PubMed1977

Evolution of cerebral abscess: correlation of clinical features with computed tomography. A case report.

Computed tomography demonstrated the evolution of a cerebral abscess. Intravenous contrast material was essential for visualization of the abscess capsule. Computed tomography was more specific than technetium 99 brain scanning and cerebral angiography, and is the only diagnostic tool so far capable of differentiating acute focal encephalitis (cerebritis) from a well-developed abscess.

Adult↗