Biomedical subjects

J J Lloyd

Publications and source records attributed to J J Lloyd.

27 records · Page 2Linked to original sources

PubMed1995

Texture analysis of technegas lung ventilation images.

Technegas lung ventilation images sometimes have 'hot spots', particularly in patients with respiratory disease. A novel technique is presented for quantifying this 'spottiness' using morphological texture analysis. A set of 32 images from patients with various respiratory diseases is studied. Images are filtered at a range of scales using morphological opening, and the slopes of image metrics versus structuring element size are used as texture parameters. The results are compared with the opinions of three experienced nuclear medicine physicians who have classified the images into two groups, 'spotty' and 'non-spotty', and have ranked the former. For the spotty images, the computer and observer ranks are compared; the highest correlation is rs = 0.66 (p = 0.01) for a single parameter, and rs = 0.71 (p < 0.01) for a combination of two parameters. Using a pair of parameters, 83% and 90% correct classification rates are obtained for the spotty and non-spotty classes, respectively. It is concluded that these texture parameters provide a useful measure of image spottiness, and it is demonstrated that this technique is superior to previously published methods. The practical value of the technique is illustrated using two applications.

Humans↗

PubMed1995

Inter-relation between "classic" motor neuron disease and frontotemporal dementia: neuropsychological and single photon emission computed tomography study.

The purpose of this study was to examine the possible association between "classic" motor neuron disease (cMND) and frontotemporal dementia (FTD), using neuropsychological evaluation and single photon emission computed tomography (SPECT). Psychological tests assessing language, perceptuospatial, memory, and "frontal lobe" functions were given to patients with cMND and test scores were compared with those of normal control subjects. 99mTc-HMPAO SPECT was performed on patients with cMND, FTD and motor neuron disease (FTD/MND), FTD alone, and normal control subjects. Regional cerebral blood flow indices (rCBFi) were determined in 36 cortical regions, and differences between grouped rCBFi data were investigated by canonical discriminant analysis. There were significant group differences in the scores of picture sequencing and token tests in patients with cMND compared with normal controls. Regional CBFi data showed frontal and anterior temporal reductions in patients with cMND compared with normal controls. A similar pattern of SPECT abnormality was seen in patients with FTD/MND and FTD alone, but to a more pronounced degree than in patients with cMND. Neuropsychological and SPECT findings in cMND, FTD/MND, and FTD showed a common pattern of cerebral involvement, most pronounced in the second two conditions. It is suggested that cMND, FTD/MND, and FTD represent a clinical range of a pathological continuum.

Adult↗

PubMed1994

The influence of inhalation technique on Technegas particle deposition and image appearance in normal volunteers.

The aim of this work was to investigate the influence of inhalation technique on Technegas image quality and on fractional particle deposition. This was investigated in six normal volunteers using three different types of breathing pattern. Fractional deposition was determined by analysis of dynamic gamma camera images acquired during Technegas administration. Static lung images were subsequently acquired and assessed independently by three experienced observers. High-quality images were obtained in all cases although slight differences were noted. The images produced using a slow deep inspiration with a breath hold (i.e. the standard method) were of more uniform texture and also had the least gradient in activity from apex to base. The converse was true for a rapid inhalation technique. The average fractional deposition per breath was 55%, but this varied between individuals and with breathing pattern, being most influenced by the total duration of a breath. We conclude that for patient studies the standard inhalation technique is best, although variation to suit individual patients would be acceptable. These results contrast with similar studies using conventional radio-aerosols, which tend to show a greater sensitivity of image appearance to changes in breathing pattern and lower fractional depositions.

Adult↗

PubMed1994

Choice of reference region in the quantification of single-photon emission tomography in primary degenerative dementia.

This study evaluated the effect of using two different reference regions in the quantification of single-photon emission tomography (SPET). SPET scans of 30 patients with Alzheimer's disease (AD) and 30 patients with frontotemporal dementia were compared with the scans of ten age-matched controls. Regions of interest (ROIs) were defined on transaxial slices by a semi-automatic method. Regional cerebral blood flow indices (rCBFi) in each ROI were determined by normalizing the count densities to both cerebellar and occipital cortex reference regions. Mean rCBFi for each ROI were calculated for the patient and control groups and significant group differences determined. The number and topographical distribution of ROIs with significant group differences varied depending upon the choice of reference region. The magnitude of these differences was greatest when the cerebellum was used as the reference region. The disparity between results obtained with the two reference regions was most apparent in the AD group. The reasons for these differences are discussed and we conclude that the cerebellum is the more appropriate choice of reference region in the quantification of SPET in primary degenerative dementia.

Alzheimer Disease↗

PubMed1994

Contamination levels and doses to staff arising from the use of Technegas.

The aim of this work was to assess the levels of airborne activity and contamination arising from Technegas ventilation scintigraphy and to estimate doses to staff. The maximum air concentration was below the 99Tcm-derived air concentration limit and considerably lower than reported levels for conventional radioaerosols. The level of contamination on staff gloves and aprons exceeded the body surface contamination limit in 63 and 9% of cases, respectively. Levels of contamination and air concentration were generally higher if the patient had difficulty with the administration procedure. Room surface contamination was very low. In 24% of cases activity was detectable on staff (either in the hair or nose) using gamma camera imaging. Annual skin doses from these sources are calculated to be below the limit for deterministic effects. Whole body effective doses are calculated to be similar to those received by staff performing other nuclear medicine studies. However, care should be exercised to keep exposure from both airborne and fixed sources to a minimum and a regular review of contamination levels is recommended. We recommend the wearing of gloves for all Technegas administrations and disposable hats and masks may be considered in certain cases.

Air Pollutants, Occupational↗

PubMed1994

Condylar hyperplasia: correlation of histological and scintigraphic features.

Scintigaphy using 99mTc-MDP is widely advocated as a method of diagnosis and presurgical assessment of patients with condylar hyperplasia. A previous study has demonstrated that hyperplasia of the mandibular condyle is characterized histologically by the presence of an uninterrupted layer of undiffentiated germinative mesenchyme cells, a layer of hypertrophic cartilage and the presence of islands of chondrocytes in the subchondral trabecular bone. This study was undertaken to determine whether there was any association between the degree of 99mTc-MDP uptake and the histological features of condylar hyperplasia. The parameters examined were trabecular bone volume, depth of cartilage islands and the presence of forming and resorbing surfaces. The images were analyzed by three experienced observers, who ranked the images according to degree of asymmetry between sides and the degree of uptake on the affected side. There was a significant correlation between the proportions of resorbing and osteoid covered bone surfaces and scintigraphic appearances. The rank correlations were rs = 0.55 (P = 0.3) between the resorptive surfaces and degree of symmetry and rs = 0.53 (P = 0.04) between the osteoid surfaces and absolute uptake. The correlation was higher for both methods (rs = 0.64 in each case) when the osteoid surface and resorptive surface measurements were combined. The results indicate that visual examination of radioisotope bone scans by experienced observers is a valid form of assessment of bone activity in condylar hyperplasia.

Adolescent↗

PubMed1992

The incidence and severity of hypoxia associated with 99Tcm Technegas ventilation scintigraphy and 99Tcm MAA perfusion scintigraphy.

Inhalation of the ventilatory radiopharmaceutical 99Tcm Technegas leads, in some patients, to symptoms that may be attributed to temporary lowering of oxygen saturation. In order to evaluate this, oxygen saturation was measured by pulse oximetry in a series of patients undergoing Technegas ventilation scintigraphy. A decrease in oxygen saturation was recorded in 87% of the patient group. The mean change, as a percentage of the initial value, was 8.3% (range 1-24%). Hypoxia arising in association with Technegas administration may be reduced by pre-oxygenation. In patients who were pre-oxygenated, oxygen saturation did not fall below 85% (PaO2: 50 mmHg) but in 39% of those not pre-oxygenated the value fell below this level. Oxygen saturation was also monitored in a series of patients undergoing perfusion scintigraphy. In 17% of patients a decrease was recorded (range 2-11%). In view of the large number of perfusion scans performed annually in this department and elsewhere without untoward effect, such temporary decreases in oxygen saturation presumably present no hazard to the patient.

Adolescent↗

PubMed1992

99Tcm-Technegas and krypton-81m ventilation scintigraphy: a comparison in known respiratory disease.

Krypton-81m gas, by virtue of its imaging characteristics, is often considered the "gold standard" for ventilation scintigraphy but its use is restricted by its high cost and limited availability. The new radiopharmaceutical 99Tcm-Technegas, a suspension of ultrafine technetium-99m labelled carbon particles, produces high-quality images of ventilation and has the advantage of continuous availability. As part of our evaluation of Technegas the two were compared in 40 patients with a variety of established respiratory diseases. Disparities were seen in five patients in five diagnostic groups and may be a consequence of the differing physical properties of the two agents and the different inhalation techniques used. In addition two interesting features were noted on the Technegas images. (1) Hot spots were seen in 50% of patients, particularly in those with a degree of airways obstruction; (2) preferential basal deposition of activity was seen in 30%, particularly in patients with idiopathic pulmonary fibrosis. Both features were significantly associated with parameters of pulmonary function indicating obstructive lung disease in the former case and restrictive lung disease in the latter.

Adult↗

PubMed1991

Evaluation of 99Tcm Technegas ventilation scintigraphy in the diagnosis of pulmonary embolism.

In the diagnosis of pulmonary embolism, perfusion lung scintigraphy offers high sensitivity but low specificity. The specificity can be significantly increased by the use of combined ventilation and perfusion studies. Most aspects of perfusion lung scintigraphy are uniformly accepted but the technique of ventilation imaging varies from centre to centre. This study describes a new technique for the performance of ventilation scintigraphy using a suspension of ultrafine carbon particles labelled with 99Tcm ("Technegas"). The technique combines the ready availability of 99Tcm and its optimal imaging properties with an easily administered radiopharmaceutical of particle size sufficiently small to deposit in the alveoli. Of 63 patients studied by conventional perfusion scintigraphy plus Technegas ventilation scintigraphy, images of diagnostic quality were obtained in all. 31 of these patients also had a ventilation study using 81Krm gas and in only one instance did the two methods of ventilation imaging lead to differing interpretations. We conclude that high quality diagnostic images may be obtained using this new technique, which can be made available on both a routine and an emergency basis, thus improving the service provided for patients suspected of having pulmonary embolism.

Adult↗