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Biomedical subjects

G H Weiss

Publications and source records attributed to G H Weiss.

At least 73 records · Page 4Linked to original sources
PubMed1982

The use of phantom views to reduce CT streaks due to insufficient angular sampling.

An artefact that can occur in CT scans with too few views is the appearance of streaks at some distance from the sharp edge that causes them. We investigate, for parallel beam scanners, the effectiveness of the method of phantom views, as well as other methods of angular interpolation, in diminishing the view-limited streak artefact. The phantom view method consists of inserting data points obtained by interpolation in angle, along with the real data points. We show by a theoretical analysis, as well as by using simulated scans, that the phantom view method does tend to diminish the distant streaks more than other methods tested. Furthermore, we show that there is a point of diminishing returns in increasing the number of phantom views.

Technology, Radiologic↗
PubMed1981

Analysis of brain abscess after penetrating craniocerebral injuries in Vietnam.

A population of 1221 patients from the Vietnam War with penetrating craniocerebral trauma was analyzed. Thirty-seven cases of brain abscess were documented (incidence 3%). This sequela occurred more frequently in association with extensive, deep penetrating injuries; deep, prolonged coma; cerebrospinal fluid fistulas; wound infections; facio-orbital cranial/air sinus injuries; and retained bone fragments. The mortality rate was 54%, and, of the patients who survived, 82% had significant morbidity. This is the last large population study of brain abscess after penetrating craniocerebral trauma before the availability of computed tomographic scanning and more comprehensive coma care. It should serve as base line data against which we can measure improvement.

Brain Abscess↗
PubMed1981

Cerebrospinal fluid fistulas complicating missile wounds of the brain.

The records of 101 casualties of the war in Vietnam have been analyzed, with particular attention to missile wounds of the brain complicated by a cerebrospinal fluid (CSF) fistula. Fifty-four developed CSF drainage at the wound site, 30 presented with rhinorrhea, and 23 with otorrhea. Fifty of the 101 men developed infection, an incidence of 49.5%. The occurrence of a fistula in vertex wounds can usually be traced to failure to close the dura, or to achieve watertight closure of the dura primarily, or by graft. Approximately two-thirds of compound basilar fractures, complicated by rhinorrhea or otorrhea, are due to direct fractures of the anterior, middle, or posterior fossa. The remaining one-third are due to elusive "discrete" fractures of the base of the skull, occurring at a distance from the entry wound, and not in continuity with the fracture of the vault. While direct basilar fractures can readily be recognized, facilitating repair of the dura overlying the basilar fractures, "discontinuous" fractures pose a challenging diagnostic problem. More commonly occurring in vertex wounds crossing the midline, discontinuous fractures producing rhinorrhea or otorrhea may be identified with the aid of tomograms of the base of the skull. Their early diagnosis may well prove to be a significant factor in the reduction of morbidity and mortality of missile wounds of the brain complicated by a CSF fistula.

Brain Injuries↗
PubMed1980

Asymptotic form for random walk survival probabilities on three-dimensional lattices with traps.

The problem of calculating statistics of time-to-trapping of a random walker on a trap-filled lattice is of interest in solid state physics. Several authors have suggested approximate methods for calculating the average survival probabilities. Here, an exact asymptotic form for the probability that an n step random walk visits S(n) distinct sites is used to ascertain the validity of a simple approximation suggested by Rosenstock. For trap concentrations below 0.05, the relative error in using Rosenstock's approximation is less than 10%.

Journal Article↗
PubMed1980

Language and motor disorders after penetrating head injury in Viet Nam.

Aphasia occurred in 244 of 1030 patients with head wounds, correlating with gunshot cause (p < 0.03) and initial loss of consciousness (p < 10(-6)). Aphasia disappeared within 10 years in 84 cases (34%). Sensorimotor aphasia usually changed to motor aphasia; motor aphasia disappeared; and sensory aphasia persisted. These improvements continued years after the accompanying hemiparesis stabilized, and were not related to wound site, depth, or whether the wound was caused by gunshot or fragment. Parietal wounds caused hemiparesis more often (p < 10(-6))than did wounds elsewhere. Regardless of the features of the hemiparesis initially, the severity of the final syndrome was greatest in the hand and arm and least in the face.

Adult↗
PubMed1980

Evolution of craniotomy as a debridement technique for penetrating craniocerebral injuries.

A craniotomy debridement technique was recommended for penetrating craniocerebral injuries as early as 1940, in World War II. However, with due consideration for the bacterial contamination of penetrating injuries, the safety of this technique was questionable. The technique has been recommended in each succeeding war, but no data substantiating the safety or eventual sequelae have been available. Analysis of the data from the large Head Injury Registry of Vietnam casualties indicates that, in properly selected cases, debridement by craniotomy technique can be safe and efficacious.

Adult↗
PubMed1979

Cranioplasty: a review of 1030 cases of penetrating head injury.

A total of 491 cranioplasties performed in a population of 1030 cases of penetrating head injury are reviewed. The morbidity rate was 5.5%, and the mortality rate was 0.2%. The clinical criteria of improving cosmetic defects and restoring craniocerebral protection are established, based on the location and size of the skull defect. Cranioplasty after penetrating head injury should be deferred for a minimum of 1 year to control morbidity. Complication of the original injury and surgical debridement increase the morbidity rate of cranioplasty. Post-traumatic epilepsy is not related to skull defects per se; neither is it affected by cranioplasty. Acrylic is an acceptable cranioplasty material if there is strict adherence to good surgical technique.

Acrylic Resins↗
PubMed1979

Regional ventilatory clearance by xenon scintigraphy: a critical evaluation of two estimation procedures.

Estimates of ventilatory clearance are usually made by inspecting xenon washout images. Quantitative computer procedures have been described that produce regional clearance rates, yet their accuracy is not well established. We define a mathematical model for scintigraphic ventilation data based on 96 clinical studies, and with this model we test the accuracy of two procedures used to estimate ventilatory clearance. The least-squares curve-fitting technique for both washin and washout data has the same accuracy as a modified Stewart-Hamilton method (A/H) that uses washout data alone. Both procedures demonstrate relative errors of less than 5% and coefficients of variation of 10-20% when regions with equilibrium count rates of 3 cps and clearance times between 10 and 90 sec are examined. Because the A/H procedure is preferred for its simplicity and speed, we analyze two of its main sources of error: early washin/washout termination and background activity. To measure regional ventilation by the A/H procedure, we recommend: (a) washin and washout periods at least three times the largest clearance time of clinical interest; b) a regional equilibrium count rate of at least 3cps; and c) a 25- to 50-sec average of the equilibrium count rate.

Humans↗
PubMed1978

Effect of CT noise on detectability of test objects.

Three types of test objects were superimposed on noisy backgrounds and observed by 58 subjects: large low-contrast disks to simulate tumors, small disks to simulate calcifications, and bars to simulate blood vessels. Three types of noise were used: random noise, CT noise (reconstructed random noise), and an actual water scan taken with an EMI CT1010 scanner. In addition, each image was smoothed by a factor of two, giving six test patterns altogether. Photographic images were presented to 25 lay observers, while 25 other lay observers and eight radiologists used a viewing console. The photographs produced a slightly lower true positive rate than the console, although the degree of confidence in the identifications was slightly greater. The anticorrelation property of CT noise gives it a "lumpy" structure, which aided the identification of bars but impeded the identification of small disks. Smoothing did not significantly affect the detectability with random noise, but with CT noise, smoothing improved the detectability of bars and large disks.

Humans↗
PubMed1976

Numerical study of the Johnston-Ogston effect in two-component systems.

Numerical solutions of the Lamm equation are presented for systems exhibiting the Johnston--Ogston effect. From these solutions it is apparent that the movement of the maxima of the concentration gradient curves reflects the sedimentation velocity of the slow or fast components in their appropriate plateaus. A simple generalization of the Johnston--Ogston analysis is presented, valid for all centrifugation times in a radial field and sector shaped cell provided only that there exist both a plateau of the slow component by itself and the mixed plateau with both slow and fast components present.

Mathematics↗