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Biomedical subjects

J R Mallard

Publications and source records attributed to J R Mallard.

At least 37 records · Page 2Linked to original sources
PubMed1982

The influence of picture element size on the quality of clinical radionuclide images.

The effect of picture element (pixel) size on image quality is investigated. Asked simply to state their preference for clinical images displayed with different pixel sizes, observers preferred those with the smallest pixel. Specific perceptual tasks, however, such as abnormality detection, are found to be insensitive to changes in pixel size up to a limit. Interpolation is found to have no effect on perceptual tasks, but 'random interpolation' produced a more pleasing image than simple linear interpolation.

Humans↗
PubMed1982

Nuclear magnetic resonance tomographic imaging in renal disease.

The non-invasive diagnostic technique of whole body nuclear magnetic resonance (NMR) imaging was evaluated in 60 patients. 30 of these patients were known to have various renal diseases and the remainder had normal renal function. In the demonstration of space-occupying lesions of the kidney, NMR proved to be as diagnostically accurate as ultrasound and intravenous urography; it was, moreover, as specific as ultrasound in differentiating malignant tumours from benign cystic lesions. The specificity of NMR was superior to both ultrasound and IVU in the diagnosis of parenchymal disease in normally situated kidneys and in renal transplants. Hydronephrotic kidneys were readily demonstrated.

Graft Rejection↗
PubMed1981

Nuclear magnetic resonance tomographic imaging in liver disease.

The non-invasive diagnostic technique of whole-body nuclear magnetic resonance (NMR) imaging was evaluated in 30 patients with established liver disease and 20 patients without liver disease. Comparison with diagnostic ultrasound and radionuclide liver scan shows that NMR easily differentiates malignant tumours from benign cystic lesions and provides useful information in patients with cirrhosis and metastatic deposits. In the demonstration of space-occupying lesions in the liver, NMR is as sensitive as ultrasound and more so than radionuclide liver scans when the metastases are less than 1.5 cm in diameter. In the demonstration of cirrhosis it is more sensitive than both ultrasound and radionuclide liver scan. The specificity of NMR is superior to both ultrasound and radionuclide liver scan, both of which only demonstrate the presence of lesions, whereas NMR tomographic imaging based on the proton spin-lattice time (T1) of tissue accurately indicates the nature of the lesion.

Cysts↗
PubMed1981

Oesophageal carcinoma demonstrated by whole-body nuclear magnetic resonance imaging.

The quality of the images produced by nuclear magnetic resonance (NMR) imaging has steadily improved over the past five years. Images of the head, thorax, and abdomen have clearly shown the normal anatomy. A clinical trial of NMR imaging has therefore been started in Aberdeen to assess its diagnostic accuracy and compare it with conventional radiography and other imaging technique. The first patient examined by whole-body NMR imaging had carcinoma of the oesophagus diagnosed on barium meal examination. A technetium-99m-sulphur colloid liver scan also showed hepatic metastases. NMR imaging showed a large tumour in the lower third of the oesophagus, and areas of increased proton spin-lattice relaxation time (T1) on a section through the liver corresponded with the metastases shown on the radionuclide scan. Increased areas of T1 were present in some vertebrae, and a technetium-99m bone scan confirmed the presence of bone metastases. The NMR images in this patient compared well with the images from other techniques. The continuing clinical trial may show that NMR is an accurate diagnostic aid which will complement existing techniques for diagnosing intrathoracic and intra-abdominal conditions.

Adenocarcinoma↗
PubMed1981

Whole-body nuclear magnetic resonance imaging: the first report of its use in surgical practice.

This is the first report of whole-body nuclear magnetic resonance (NMR) imaging being of value in clinical surgery. Following aortobifemoral grafting, a 54-year-old man developed a pyrexia and hypotension which did not respond to antibiotic therapy and which was thought to be caused by early graft infection. Whole-body NMR imaging showed the graft and iliac arteries to be normal and an empyema of the gallbladder to be present, NMR imaging is a safe, non-invasive technique for imaging the body in transverse sections and specifically measures the water concentration of tissues, enabling normal and inflamed tissues to be differentiated.

Aorta, Abdominal↗
PubMed1981

A clinical trial of the value of a tomographic section view to identify liver abnormalities by radionuclide imaging, with special reference to metastatic disease.

A prospective trial was carried out to assess the value of a radionuclide transverse section view in addition to conventional radionuclide scans of the liver. Reports for 373 patients were analysed and compared with the final independent clinical diagnosis. Although several individual cases were more accurately diagnosed using the tomographic section view, the trial did not demonstrate a significant increase in accuracy of diagnosis in liver disease. Some possible reasons for this are discussed, mainly the difficulty of identifying and quantifying truly abnormal features of liver radioisotope scans.

Evaluation Studies as Topic↗
PubMed1981

The effects of some physical factors on the production of hyperthermia by ultrasound in neoplastic tissues.

A one-dimensional and a three-dimensional computer model have been built in order to study the importance of blood flow and ultrasonic absorption in tissues during local hyperthermia. The decreased blood flow in the interior of certain tumours and possibly the increased ultrasonic absorption of the malignant tissue in some cases may cause selectively higher temperatures inside the tumours though the heat input is the same as in the surrounding tissues. Also, the vasodilation of blood vessels in normal tissues as a response to heat causes a therapeutically useful temperature difference. These blood flow differences can lead to enhanced effects during sonication to produce hyperthermia in the tumour. The inhomogeneity of blood flow in the tumour causes a non-uniform temperature distribution leaving the well-perfused cells in the advancing front at a much lower temperature than the cells in the necrotic centre. Thus, the combination of local hyperthermia with radio-and chemotherapy seems to offer the most attractive means of destroying malignant tissue.

Fever↗
PubMed1980

Contribution of radioisotope CAT to the detection of recurrent tumour in the brain.

Two cases are described showing the value of Radioisotope Computerized Axial Tomography in the early detection of tumour recurrence in the brain. The possibility of recurrence could not be excluded from the information provided by the conventional views since the suspicious areas found could be due to post-operative uptake. In the first case, reliable identification of tumour recurrence was provided by the transverse section scan through the suspicious area. In the second case, the transverse scan showed the uptake to be due to previous craniotomy.

Brain Neoplasms↗
PubMed1980

A preliminary investigation of 67Ga citrate distribution in hyperferraemic patients.

Scanning for malignant or inflammatory lesions with 67Ga citrate currently has a number of major limitations. In an effort to improve visualisation of the abdomen and pelvis, and to reduce the time between 67Ga citrate injection and the scan (usually 72 h) a series of patients was given an intramuscular injection of 100 mg iron-sorbitol citric acid complex (jectofer) two hours prior to receiving an intravenous injection of 67Ga citrate. Laboratory measurements on blood samples removed at different times showed that this pre-treatment altered radically both the amount of free transferrin and the level of 67Ga activity in the blood pool for the majority of patients. Follow up of 30 patients entered in this preliminary trial showed that when 24 h and 48 h scans were analysed together, accuracy in the diagnosis and localisation of pathological lesions was at least as good as by the standard method. We believe that by saturating the free transferrin with iron, uptake into normal soft tissues may be modified sufficiently to enhance significantly the tumour to background ratio, thereby making earlier scanning possible. Investigations are continuing.

Citrates↗