Biomedical subjects
L K Harding
Publications and source records attributed to L K Harding.
Pattern of radiopharmaceutical administration to patients between 1982 and 1986.
Analysis of the workload of a nuclear medicine department over the period 1982 to 1986 has shown the prevalence of repeated investigations in individual patients. Records from 23,152 investigations on 17,063 patients indicated that 88.5% received a single administration and only 0.5% received more than four doses of the same radiopharmaceutical. Patterns of usage of a wide range of radiopharmaceuticals are presented and show that the technetium bone imaging agent is the radiopharmaceutical most commonly used for repeated administrations. Analysis of the radiation dose to individual patients arising from radiopharmaceutical administration has shown that only two patients in the survey exceeded 50 mSv per annum and approximately 25% of patients exceeded 5 mSv per annum.
Effect of Roux-en-Y reconstruction on the gastric emptying of a solid meal.
The gastric emptying of a solid meal was measured in 39 patients after Roux-en-Y reconstruction and compared with that in 27 patients after truncal vagotomy and pyloroplasty and that in 22 patients after Polya gastrectomy. There were no significant differences among the groups. It is concluded that despite the disruption of the normal motor pathway produced by the Roux-en-Y reconstruction it does not lead to clinically significant delay in gastric emptying.
Radiation safety in the nuclear medicine department: impact of the UK Ionising Radiations Regulations.
The practice of nuclear medicine requires integration of radiation safety with patient care and radiopharmaceutical standards. Nationally there was useful discussion in the UK before the Ionising Radiations Regulations and Approved Code of Practice were published, although such consultation had been lacking when the Medicines Act was implemented. Most of the new considerations relating to nuclear medicine stem from Schedule 6 of the Regulations. Generally, the presence of a single patient does not require a controlled area. However, when several patients are present, or radiopharmaceuticals are being prepared prior to injection, a controlled area is required. Classification of workers is not likely to be required in a typical nuclear medicine department in the UK, although most parts of the nuclear medicine department will need to be controlled areas. These include the radiopharmacy, radionuclide dispensary, injection room, and imaging rooms if patients are injected in them. The importance of finger dose measurements is emphasised. Patient wards, however, need not be controlled areas. A particular concern in nuclear medicine was that patients should not need to be admitted to hospital merely to comply with legislation. This is possibly the case and clarification will probably be available when the Notes for Guidance are published. Most procedures in nuclear medicine departments will remain unchanged. Further information is required, however, on patient waiting rooms, handling flood sources, pregnancy, and breast feeding. Within the hospital, detailed and multidisciplinary discussion will need to take place within the forum of the radiation safety committee.
Nuclear medicine and clinical chemistry departments.
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Implications of the ionizing radiations regulations for typical nuclear medicine departments.
The application of the 1985 Ionizing Radiations Regulations and Approved Code of Practice to a typical Nuclear Medicine Department has been considered. References to the Regulations are given so that their implications in a given department may be examined. The radiopharmacy, radioisotope dispensary and injection room will need to be Controlled Areas. It will also be necessary to designate Controlled Areas if radiopharmaceuticals are injected in imaging rooms or on wards. Waiting rooms will need to be Controlled Areas. The area around individual patients will, however, not need to be Controlled except for some patients receiving therapeutic doses of 131I for thyrotoxicosis. It should not generally be necessary to designate employees as Classified persons. Major problems in implementing the Regulations are not envisaged in situations where the previous Code of Practice has been followed.
Regulations affecting the practice of nuclear medicine.
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Hospital income from private patients.
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Screening procedures for identifying patients after gastric operations at high risk of developing premalignant histological changes.
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Dose rates from patients having nuclear medicine investigations.
Dose rates have been measured at 0.1 m, 0.5 m and 1.0 m from patients in a Nuclear Medicine Department. Data are presented for a variety of Nuclear Medicine procedures using doses of radiopharmaceuticals within the recommendations of the administration of Radioactive Substances Advisory Committee (ARSAC). The corresponding figures when the patient left the department, and the time average dose rate over the next 8 h were calculated. At 1.0 m the dose rates do not exceed 7.5 microSv h-1, and at 0.5 m the time average dose rate does not exceed 60 microSv h-1. Assuming that the nurse is as close to the patient as 0.1 m for 20 min in a working day, the accumulated dose over a working day would not exceed 60 microSv.
The value of syringe shields in a nuclear medicine department.
The radiation dose to the pulp of both index fingers has been measured in a radiopharmacy supplying 11 000 patient doses a year, in a hospital dispensary (4500 doses a year) and in its injection area. Tungsten syringe shields were used for one week and not used during the other week. In the radiopharmacy and the dispensary the highest finger dose recorded was 6.8 mSv, which corresponds to an annual figure of 330 mSv. Syringe shields gave a protection factor of less than two, and the dose to the left hand was approximately half that to the right. When giving injections the corresponding weekly and annual doses were 4.6 and 220 mSv respectively. If all injections had been given by a single person the corresponding annual dose would have been 430 mSv. Using syringe shields this could be reduced by factors of at least eight for the right hand but only 1.3 for the left hand. Dose rates for unshielded syringes expressed per 10 GBq handled are similar to other data in the literature. However, syringe shields reduce the dose rates less than anticipated. Tungsten 1.94 to 3.05 mm thick would be expected to give an attenuation factor of 27 to 178.
The cost of X-rays and nuclear medicine investigations.
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Role of lung scanning in assessing the resectability of bronchial carcinoma.
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Gastric histology and its relationship to entero-gastric reflux after duodenal ulcer surgery.
Thirty-six volunteers, asymptomatic 7 to 22 years after various operations for duodenal ulcer, were screened for enterogastric reflux by external scanning following injection of 99mTc HIDA; they also had endoscopy for measurement of the fasting juice pH, and multiple biopsies. In patients with a pH above 4 there was an association between a positive bile reflux test and the presence of pre-malignant changes in the gastric mucosa. Carcinoembryonic antigen in the gastric mucosa was found in all patients and was not, therefore, a useful screening test for stump cancer. Blind examination of two sets of endoscopic biopsies obtained 6 weeks apart in symptomatic patients with post-operative reflux gastritis showed that histological assessment remained reproducible. Gastric biopsies obtained from 16 patients before, and a year after, Roux-en-Y gastro-jejunostomy demonstrated that foveolar hyperplasia tended to regress after bile diversion.
The incidence of duodenogastric reflux in peptic ulcer disease.
Using 99mTc diethyl HIDA, a gamma camera was used to assess duodenogastric reflux of bile in the supine position in control patients and patients with active duodenal ulceration. Cholecystokinin was injected intravenously during the test to contract the gall bladder. Patients with benign gastric ulcers, and a group of age matched controls, were investigated for duodenogastric bile reflux in the sitting position by a nasogastric aspiration technique after a 10% dextrose meal. Of 60 patients with duodenal ulceration 32 (53%) were reflux positive, and of 13 control patients 6 (46%) were positive. Of 30 patients with gastric ulceration 17 (53%) were reflux positive, and 8 out of 15 (53%) control subjects were positive. The incidence of duodenogastric reflux assessed supine in the fasting state, and seated after a liquid meal, was similar in patients with peptic ulceration and in normal controls.
Bile reflux after duodenal ulcer surgery. A study of 114 asymptomatic and symptomatic patients.
The hypothesis has been examined that the quantity of enteral contents refluxing into the stomach affects the severity of symptoms after peptic ulcer surgery. 99mTc HIDA scintigraphy was used to investigate the incidence and quantity of reflux in 20 normal subjects, in 94 symptomatic or asymptomatic patients after traditional operations for duodenal ulcer, and after revision of surgery for bile reflux gastritis. The percentage of the injected dose of 99mTc HIDA (PID) counted in the stomach area was used as an index of the quantity of refluxed bile. After duodenal ulcer surgery, symptomatic patients had a PID (6.2%) not significantly different (4.5%) from that of asymptomatic patients but higher than (2.1%) that of normals (p less than 0.05). After operations for reflux gastritis, 10 symptom free patients had no reflux, whereas 3 of 8 patients who remained symptomatic and had a short Roux-en-Y gastrojejunostomy, had persistent reflux.
Does duodenogastric reflux affect the rate of gastric emptying?
The gastric emptying of a liquid meal (10% dextrose solution) and a semi-solid meal (minced meat, peas, potatoes and milk) was measured in the sitting position; both meals were 400 ml. Duodenogastric reflux was assessed supine after intravenous injection of 75 MBq of 99 mTc HIDA and cholecystokinin. Patients were ajudged reflux positive (R+), or reflux negative (R-) by looking at gamma camera pictures. Thirty-two duodenal ulcer patients (DU), 22 patients after truncal vagotomy and pyloroplasty (TV+P) and 21 after proximal gastric vagotomy (PGV) were studied. In DU sufferers the mean volume of early liquid emptying in R+ patients (74 ml) was similar to R- patients (78 ml). After TV+P early liquid emptying was greatly increased (mean 176 ml) but no difference was found between R+ and R- patients. After PGV excessive early emptying was less common but emptying was significantly greater in R+ patients (R+ mean = 132 ml, SD = 48 n = 8; R- mean = 63 ml, SD = 21, N = 13: t = 4.2 p less than 0.001). There was no difference in solid meal emptying between R+ and R- patients in any group.
The pharmacokinetics of 99mTc HIDA in man and its relationship to intra-gastric bile acids.
We have examined the pharmacokinetics of 99mTc diethyl HIDA in five patients with a T-tube inserted into their common bile duct after choledocotomy. Blood clearance was rapid with 27.5% of the injected dose in the circulation at 2.5 min and 5% at 30 min. The peak bile excretion of 15.4% occurred between 45 and 60 min after injection of the HIDA. By 2 h 69% of the dose was excreted in the bile and 14% in the urine. In a second group of 33 patients a naso-gastric tube was passed after injection of HIDA. The patients drank 400 ml of 10% dextrose and aliquots of the stomach contents were aspirated every 10 min for an hour. In specimens with a pH greater than 4, the amount of HIDA correlated well (p less than 0.01) with the amount of bile acid determined by an enzymatic method.