PubMed Health⌕ Search

Biomedical subjects

D Plummer

Publications and source records attributed to D Plummer.

35 records · Page 2Linked to original sources
PubMed1989

The external rotation method for reduction of acute anterior shoulder dislocation.

Acute anterior shoulder dislocation is a common disorder confronting the emergency physician. Traditional methods of reduction are often technically difficult, time consuming, and painful to the patient. Furthermore, they frequently require more than one physician and occasionally exacerbate the injury. Conversely, the recently described method of reduction by external rotation is a reliable and safe method. A single physician performs the reduction rapidly and patients tolerate it well.

Emergencies↗
PubMed1988

19F NMR imaging of blood oxygenation in the brain.

Perfluorocarbon (PFC) emulsions have been developed as oxygen carrying blood substitutes. High fluorine concentrations allow them to be used in 19F NMR imaging of blood vessels. Furthermore, 19F relaxation times in PFCs are dependent on oxygen tension (pO2) so that NMR imaging may provide a noninvasive method of measuring spatially localized pO2 values in vivo. Using these principles, we have formed 19F images and calculated pO2 maps of the cat brain.

Animals↗
PubMed1988

Evaluation of computer advisor in the interpretation of CT images of the head.

This paper describes the evaluation of a computer advisor system (BRAINS), which was constructed to aid in the interpretation of CT images of the head. It was developed at the National Hospital for Nervous Diseases, Queen Square, London. The system was transferred, without difficulty, to an 'external', that is previously unassociated, site (the Department of Diagnostic Radiology, University of Manchester) for an external evaluation. Response of external users to the system was mixed. Many were unfamiliar with the concept of formal description of images and the evaluation demonstrated the need for a person to person training programme. Users who accessed the HELP facilities most frequently were the most successful in obtaining accurate descriptions and hence satisfactory diagnostic advice. An objective appraisal of user's success in describing images to obtain the correct diagnosis as first choice indicated that, in general, the system performed well.

Brain Diseases↗
PubMed1988

Towards an advisor for MRI.

This paper discusses the role of a computer advisor in MR image acquisition, interpretation and the diagnosis of cerebral disease. The development of an image and statistical database for use in providing advice is described.

Brain Diseases↗
PubMed1988

Echocardiography performed by emergency physicians: impact on diagnosis and therapy.

Echocardiography is the "gold standard" for diagnosing many cardiac and pericardial abnormalities. It is noninvasive and accurate, but in most emergency departments is only as available as the technician or the cardiologist. We describe our experience in training emergency physicians to perform cardiac ultrasound, and clinical situations in which we have found echocardiography to be useful.

Adolescent↗
PubMed1988

19F imaging of cerebral blood oxygenation in experimental middle cerebral artery occlusion: preliminary results.

Fluorine (19F) nuclear magnetic resonance may be used to image cerebral perfusion in cats receiving perfluorocarbon blood substitutes. 19F relaxation times in these blood substitutes are dependent on oxygen tension (PO2) and may be used to calculate and spatially map cerebrovascular PO2 values in vivo. We have applied this noninvasive method to experimental middle cerebral artery (MCA) occlusion. Following MCA occlusion a perfusion defect is evident in the sylvian region, followed by the appearance of collaterals. Signal from the ipsilateral rete mirabilis is increased. Calculated cortical vascular PO2 values indicate a relative reduction in oxygenation in the ischaemic hemisphere. PO2 maps show a perfused hypoxaemic zone adjacent to the perfusion defect. These changes are partly reversed with reperfusion.

Animals↗
PubMed1982

An analysis of signal amplification using small detectors in positron emission tomography.

Spatial resolution in computed tomography (CT) has been limited because of the excessive increases in statistical noise associated with increasing resolution. Reconstruction filter functions have been designed to produce tomographic images with resolution as close as possible to the intrinsic detector resolution. Since these filter functions apply an increasing weight to increasing spatial frequencies in the measured data, this produces a large amplification of noise at the upper end of the spatial frequency band of the filter function where the signal from the detector has a low amplitude. This mathematical approach to spatial frequency amplification cannot distinguish between signal and noise and thus both are amplified equally. An approach for improving tomographic resolution is the use of very small detectors to selectively amplify the signal but not noise. This signal amplification technique (SAT) can provide improvements in image resolution without increases in the cutoff frequency of the reconstruction algorithm. Alternatively, in cases in which image counts are low, statistical noise can be reduced by lowering the cutoff frequency. A possible system design for a positron CT system with SAT is described.

Animals↗
PubMed1982

Quantitation in positron emission computed tomography: 6. effect of nonuniform resolution.

The intrinsic resolution (FWHM) of coincident bismuth germanate detector pairs was measured for geometries consistent with positron emission computed tomography systems designed for brain imaging. The resolutions were measured as a function of the position in the field of view (FOV) for single slice and multislice configurations for both the image and axial resolutions. System diameters of 66 to 42 cm were simulated, and intrinsic resolution variation for image and axial dimensions for a 24 cm FOV were 14 and 32% and 24 and 39%, respectively. Measurement of axial resolutions of interplane slices of multiplane systems employing interplane septa showed resolution variations for the 24 cm FOV of as large as a factor of three. A simple model was shown to predict the dominant features of the line shapes. Images of phantoms with small axial dimensions indicate that the variations in resolution, particularly in interplane data, seriously compromise the validity of point to point comparison of information within an image or between single plane and interplane images. Serious variations in axial resolution were shown to create artifacts and degrade the image resolution. Index Terms: Emission computed tomography--Image quality.

Tomography, Emission-Computed↗
PubMed1981

Quantitation in positron emission computed tomography: 5. Physical--anatomical effects.

The effect of neuroanatomical structure size, shape, and position versus spatial tomographic resolution on quantitation in positron computed tomography was investigated. For neuroanatomical structures, voxel sizes in excess of 3 ml exceeded the volume of most structures examined. When the voxel size exceeded structure volume, calculated recovery coefficient (fraction of the true isotope concentration measured in the image) fell to less than or equal to 42%. Partial volume effects in the plane of section analyzed by computer simulation produced errors that were largest for small, thin, irregularly shaped structures whose averaged pixel values were most different from neighboring structures. Smallest errors occurred in large, circular structures surrounded by regions of similar pixel values. Computer simulation of regional cerebral asymmetries of pixel values demonstrated that the measurement of these asymmetries was often predominated (enhanced or obliterated) by partial volume effects related to structure size and shape. Large, circular, and widely separated regional asymmetries were more easily detected at a given spatial resolution than small, thin, adjacent regions. Recommendations for error reduction and possible correction factors are provided and discussed.

Brain↗
PubMed1980

A new radioisotope for lung ventilation studies: 19-neon.

Neon 19, 17-second positron-emitting radioelement, is produced continuously by 23MeV alpha particle bombardment of oxygen. For a 12 muA particle current the method of preparation described delivers 14 mCi of neon 19 per min to the functional exploration room. The radiochemically pure radioactive gas is diluted in air and breathed continously by the patient lying under a positron tomographic camera. The regional lung ventilation distribution is obtained on 2 cm thick sections of organ with a transverse resolution of 17 mm. Quantification of the ventilation output per unit lung volume is contemplated.

Heart Ventricles↗
PubMed1979

The physical performances of a single slice positron tomographic system and preliminary results in a clinical environment.

Metabolic phenomena can be studied and measured non-invasively using positron emitting radionuclides and a suitably adapted tomographic system. The choice of a single slice ring camera is justified by its physical performance, which is presented here and discussed. A series of measurements with geometrical phantoms and analytical simulations have been performed to determine the critical characteristics of the system. This has permitted optimization of certain parameters enabling very interesting clinical results to be obtained at SHFJ, particularly in the area of cerebral physiopathology. In addition, the potential of obtaining absolute quantitative values of regional activity is presented. The calibration of the regional activity is presented. The calibration of the system, spatial non-stationarities, and attenuation correction, which represent the main sources of error, are considered in detail. A precision of the order of 10% should be obtainable. Such a quantitation method has been successfully applied to the in vivo study of the regional extraction of cerebral oxygen.

Brain↗
PubMed1979

[11C]methionine pancreatic scanning with positron emission computed tomography.

By the use of [11C]methionine and positron computed tomography (PCT), images of the pancreas were obtained in 32 patients. The injection of between 10 and 20 mCi of this product enables four to six transverse sections to be obtained. Seventeen of the patients studied had no exocrine pancreatic disease, and in all these cases the pancreas was clearly visible. In four cases of pancreatic carcinoma and one of retroperitoneal tumor, there were abnormalities visible. In five cases of chronic pancreatitis, no pancreatic uptake was observed. In a sixth case, concentration was visible, but only in the head of the pancreas. One case of acute pancreatitis, which showed no concentration during the acute phase, returned to normal after recovery. When visible, the pancreas was easily located and distinguishable from the intestinal image, except in two cases that were uninterpretable for technical reasons. No false positive or negative was observed, but a differential diagnosis between cancer and pancreatitis was impossible.

Carbon Radioisotopes↗
PubMed1978

[Tomographic study in humans of blood flow and oxygen consumption of the brain by continuous inhalation of oxygen 15. Preliminary findings in cerebral ischemic accidents].

Transverse axial tomographic imaging of regional cerebral blood flow (rCBF) and regional oxygen extraction fraction (rOEF) were obtained in 13 patients hospitalizedfor ischemic strokes (eleven middle cerebral artery territory infarcts, one capsular or pontine lacune, one transient hemispheric attack) by continuous inhalation of 15O2 and C15O2 to equilibrium and exclusive detection of the gamma rays emitted in coincidence by means of a tomograph for positron emitting agents. In the transient ischemic attack and in the case of lacune the rCBF and the rOEF images were found to be normal, and they were abnormal in all cases of middle cerebral artery territory infarcts. In recent infarcts, rOEF was always strikingly decreased in the clinically suspected area, whilst the rCBF was either decreased, normal or increased. In infarcts older than 30 days rCBF was always clearly decreased over the clinically suspected area whilst rOEF was in most cases normal or only slightly decreased. These results are briefly discussed. Some practical and theoretical limitations of this method are mentioned. The potential of the present technique appears great however, since it is possible to simultaneously visualize in tomographic fashion the blood flow and the oxygen metabolism in areas of the brain that are of small volume, and however deep they are. A quantification of these parameters is presently under investigation, as well as the verification of the theoretical model on which such method is based. The non-invasiveness of the present method, the feasibility of repeating it at regular intervals of time, and the possibility of measuring the immediate effects of a given therapeutic mode on the regional metabolism of brain all constitute further advantages whose action apply preeminently in the field of the cerebral ischemic diseases.

Aged↗
PubMedDate not supplied

Computer assistance for C.T. scan interpretation and cerebral disease diagnosis.

This paper describes the development and use of a system to aid in the radiological interpretation of C.T. scan images of patients with cerebral disease. The system is able to provide guidance, both on diagnosis and the need for further scan investigations. Explanation and help facilities, similar to those found in certain rule-based expert systems, are available on demand. Diagnostic and other advice is, however, based on hard statistical data. The scan interpretation and diagnostic system offers important benefits in the training of less experienced radiologists.

Brain Diseases↗