Biomedical subjects
Publications and source records attributed to D Shackleton.
A new daytime sleepiness scale was constructed on the basis of interviews with 96 apnea patients (the Rotterdam Daytime Sleepiness Scale) and included three subscales of Global Evaluation, Behavioral Impact, and Affected Life Domains. The scale showed satisfactory convergent and discriminant validity.
The use and development of iodine-125 plaque therapy for choroidal malignant melanoma are described. Since 1975 experience has led to changes in plaque design and insertion techniques. Twenty-one patients were irradiated with local episcleral iodine-125 plaques. Three patients required a second plaque for tumour recurrence. Four eyes were enucleated because of continued tumour growth and a further eye was removed because of glaucoma secondary to radiation retinopathy. Two patients (9.5%) died of metastases. The remaining 19 patients are alive and clinically clear of metastases, with a mean follow up time of 73.1 months (range 43-142 months).
125I has an energy of 27-35 keV which permits highly effective screening and makes it eminently suitable for treating ophthalmic tumours. It was first used for this in 1974 (Sealy et al., 1976), and since then a flexible system has been developed to treat a variety of such tumours including localized retinoblastoma. A gold foil backed plaque is custom built to cover the tumour(s). The turned edges reduce the dose and thus protect vital adjacent structures such as the optic nerve and lens. The iodine seeds are sealed in the plaque in a predetermined position to give the required dose. A range of doses and times have been used but the authors now aim to give a TDF of 100 to the apex of the tumour in two to three days. Ten tumours in the remaining eye of seven patients with bilateral retinoblastoma were treated. The size ranged from 3 X 3 X 2 to 10 X 10 X 6 mm. There were nine complete responses from 17-90 months and a partial response in one patient who died of metastases at ten months. Vision was maintained in all. Eight recurrent tumours in seven patients were also treated together with a subsequent new tumour in one of the patients. There were three complete responses at 28-39 months and six tumours persisted. Vision was maintained in three of seven patients. The only complication was a vitreous haemorrhage which was mild in two patients, moderate in one patient and severe in three previously treated patients. These latter three patients subsequently had the eye enucleated and were found to have recurrent tumour.
Patients who are at risk for developing an orbital recurrence after enucleation of the eye for retinoblastoma are those with full thickness choroidal invasion or further extension into the sclera or extension into the optic nerve beyond the lamina cribrosa. The authors have treated these patients routinely with external irradiation to the orbit but this usually resulted in a dry contracted socket that often would not accept a prosthesis. An orbital implant was designed with 125I seeds in an attempt to improve the cosmetic result. It consisted of seven rows of 125I seeds, six of which were partially screened and implanted around the periphery of the orbit so that the contents were irradiated whilst reducing the dose to the bony orbit. The seventh central row was unscreened. A metal disc, with 125I seeds sealed to the posterior surface, was sutured beneath the eyelids thus protecting them and the accessory lacrimal glands. A TDF of 90-100 over two to three days was given. Thirteen patients have been treated, nine prophylactically and four therapeutically. Three of the latter patients have died of metastases but no local recurrences have been seen. All 13 patients were left with a moist socket that accepted a prosthesis.
Developments in a new system of brachytherapy for tumours of the eye are reported. This involves the use of 125I sources with special screens and filters to avoid irradiation of vital structures and to produce a homogeneous radiation field. Methods for the treatment of tumours of the lids, conjunctiva, retina, choroid and lachrymal gland have been developed. Sixteen out of 20 treatments appear to have been successful. This system would seem to be a material advance on those previously reported.
It has long been suspected that the depth-dose characteristics of modern 60Co teletherapy units are no longer well represented by the traditional data of The British Journal of Radiology Supplement 11. Extensive measurements have been undertaken on three modern 60Co units in an attempt to clarify this position. Three different values of source-to-skin distance were studied, namely 50, 80 and 100 cm. Systematic deviations from the traditional data are unambiguous, amounting to up to 3% at 80 cm SSD and as much as 7% at 50 cm SSD. Comparison with calibration results at a large number of institutions lends confidence that the present results are representative of modern treatment units.
Seventeen patients with idiopathic autoimmune thrombocytopenic purpura were studied in order to establish whether the amount of platelet-bound antibody influenced the rate and site at which these platelets were destroyed. Platelet-bound antibody was measured by a quantitative antiglobulin consumption technique, and platelet survival and sites of sequestration were determined by the use of 51Cr-labeled platelets and surface radioactivity measurements. A correlation significant at the 5% level was observed between the amount of platelet-bound antibody and the rate of platelet destruction. A highly significant correlation (p less than 0.001) existed between antiplatelet antibody and spleen: liver surface radioactivity ratios, demonstrating that greater amounts of antibody bound to platelets result increasingly in their destruction within the liver.
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Platelets eluted from nylon fiber filters after filtration leukapheresis have been studied. The platelet yield from 61 routine donations was 1.25 +/- 0.18 x 10(11), (mean +/- SEM) corresponding to 1.78 x 10(10) per 500 ml blood processed. Filtered platelets labeled with radiochromate demonstrated reduced recovery in vivo 15 minutes after infusion (38.5 +/- 1.7%) when compared to the control value (68.5 +/- 6.8, p less than 0.001). The survival of those platelets remaining in the circulation after 15 minutes did not however differ from the control value. ADP (10 micrometer, 1 mM), adrenaline (100 micrometer) and collagen (7.25 mg/ml) added in vitro induced less aggregation of filtered platelets than normal control platelets and electron microscopy revealed structural abnormalities. It is concluded that recipients of granulocyte transfusions obtained by filtration leukapheresis are unlikely to be benefited by the platelets contained in these transfusions.