Biomedical subjects
Publications and source records attributed to C B Clayton.
The effect of global immunosuppression by sublethal whole body X-irradiation on the development of cerebral oedema was assessed 24 h after right middle cerebral artery occlusion in the rat. Irradiation produced a significant leukopenia and thrombocytopaenia, and significantly reduced cortical oedema when compared to non-irradiated control animals.
The oedema which forms around an intracerebral haemorrhage has a complex aetiology. The immune response may have a role in its formation. There is clinical and experimental evidence that circulating leucocytes and platelets may mediate oedema formation. Global depletion of circulating leucocytes and platelets by whole body irradiation in a rodent model of intracerebral haemorrhage was found to confer protection against both ischaemia and oedema formation. This was not a direct effect of irradiation of the brain. The possible mechanisms for this protection are discussed.
Thallium isotope scintigraphy is used to localize parathyroid adenomas but the mechanism underlying the technique is poorly understood. While larger adenomas are reliably localized the results are less certain for small tumours. This study explores the relationship between cellular DNA profile and thallium uptake (localization accuracy) in 24 parathyroid adenomas. The DNA profile was assessed using flow cytometry and standard subtraction thallium scintigraphy was performed before surgery. Fifteen of the 24 adenomas demonstrated excessive mitotic activity and 13 of these glands were accurately localized. Of the remaining nine glands, only five were localized accurately (P less than 0.01, chi 2 test including Yates' correction). This difference in thallium uptake could not be accounted for on the basis of gland weight. Thallium localization of parathyroid adenomas is related to mitotic activity. This may explain some of the limitations of this technique.
The purpose of the study was twofold: (a) to relate the degree of clinical suspicion of pulmonary embolism (PE) to the findings of isotope ventilation-perfusion (V/Q) scans, and (b) to determine the extent to which the scan results influence patient management. A questionnaire was completed by the requesting clinician before V/Q scanning in 60 consecutive in-patients in whom PE had, with varying degrees of probability, been considered possible. Retrospectively, the case notes were reviewed to determine whether or not the patients were anticoagulated when discharged. Prior to scanning, PE was considered probable or almost certain in 35 (58 per cent) patients and unlikely or very unlikely in 25 (42 per cent) patients. Thirty-seven (62 per cent) scans were confidently reported positive or negative for PE; in the remaining 23 (38 per cent) cases, the scan report was necessarily inconclusive. The clinical assessment was supported by the scan result in 23/25 (92 per cent) patients in whom PE was felt unlikely or very unlikely, but in only 14/35 (40 per cent) in whom this diagnosis was felt probable or almost certain. Twenty (33 per cent) patients were already anticoagulated when scanned; this treatment was initiated in nine (15 per cent) and discontinued in eight (13 per cent) in the light of the scan result. Isotope V/Q scans are not always useful in confidently confirming or excluding the presence of PE. Nevertheless, the scan reports, even when necessarily guarded and somewhat at variance with the clinical assessment of the probability of PE, strongly influence clinicians in their decisions as to whether to anticoagulate their patients.
A double-radionuclide autoradiographic method has been assessed for sequential determinations of local CBF (LCBF). It is based on two successive intravascular injections of N-isopropyl-p-iodoamphetamine (IMP) labelled with different radionuclides, whose concentrations can later be differentiated in the same tissue section using double-radionuclide autoradiography. Previous studies suggested that the distribution of IMP, up to 30 min after its administration, still represents LCBFs. Our data indicate that, provided the tracer is injected directly into the left ventricle, there is little back diffusion from normal brain to blood under physiological conditions for at least 35 min following the tracer injection and an injection of unlabelled IMP, in a dose larger than that used for blood flow determination, does not displace any labelled IMP previously taken up by the brain, nor does it displace any labelled IMP previously accumulated in the lung that would lead to secondary brain uptake. On the basis of these results, we conclude that sequential autoradiographic determinations of LCBF using IMP labelled with different radionuclides is possible. This is a promising experimental method for the simultaneous investigation of changes in LCBF in several CNS structures.
Eighty patients who had sustained a fracture of the tibial shaft were studied by scintigraphy using technetium-99m labelled methylene diphosphonate (99Tcm MDP) and a gamma camera. Static scintigrams were obtained in the early stages following injury and examined for the presence of 'cold spots' which may indicate loss of blood supply to fracture fragments; these were found in 10 per cent of cases but did not bear any definite relationship to the normal progression of union. Sequential dynamic scintigrams were obtained at intervals up to 20 weeks after fracture to determine whether a pattern of uptake of tracer could be identified which correlated with the subsequent progression of union, but no significant difference was observed between fractures healing promptly (less than 20 weeks) and those in which healing was delayed (greater than 20 weeks).
The ratio of the uptake of radioactivity in each sacroiliac joint to the uptake in the sacrum has been measured in 57 patients with early ankylosing spondylitis and in 51 control subjects. The distribution of ratios of uptake obtained in each of these two groups shows appreciable overlap, and it is shown that the specification of a 'normal range' in this sort of situation can be misleading in the interpretation of the uptake ratio obtained in a given subject. An alternative approach described here is to use Bayes' theorem, which combines a probability based on the numerical value of the measured ratio with the pretest clinical impression about the likelihood of ankylosing spondylitis to yield a post-test probability of the presence of the disease.
During a one-year period 53 patients were referred for the investigation of epiphora. All underwent bilateral dacryoscintigraphy. Following the isotope study the patients had either bilateral or unilateral macrodacryocystography; a total of 66 tear ducts were shown by this procedure. The scintigraphs were more sensitive for obstruction (51/66 systems or 77%) than radiography (33/66 systems or 51%). Normal dacryoscintigraphy was always associated with duct patency on dacryocystography. We have concluded that scintigraphy should always be the first investigation and that, if this is normal, radiography is not necessary. The use of digital subtraction imaging for the lacrimal passages is discussed. It is suggested that this may provide information obtained at present only by combining dacryoscintigraphy with conventional contrast radiography.
A scintigraphic study of the human tibia in the early stages following fracture of the shaft was carried out to investigate the condition of the blood supply of the main fracture fragments. Using a gamma camera and 99mTc-MDP, scintigraphs were obtained from less than 24 hours to 21 days after injury. A generalized increase in tracer uptake was found in the tibia in all cases. In some cases very early after injury there was an additional local increase at the fracture site. In 10% of cases "cold spots" were observed, which may indicate an impaired blood supply to bone tissue adjacent to the fracture. Neither the presence of a "cold spot" nor any other scintigraphic feature could be correlated with the progress or time to fracture union.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.