Attenuation characteristics of MagnaDense high-density concrete at 6, 10 and 15 mv for use in radiotherapy bunker design.

The attenuation characteristics of MagnaDense high-density concrete are measured using the x-ray beams from two Varian linear accelerators at nominal 6, 10, and 15 megavolt energies. The tenth value layers for the primary beam are evaluated under broad- and narrow-beam conditions. The attenuation of secondary radiation is also investigated. Measured data are compared with existing data used in radiotherapy bunker design, derived from the scaling of published tenth value layers for ordinary concrete according to physical density. Instantaneous dose rates around an existing bunker with MagnaDense concrete walls and a conventional concrete roof are predicted using the various different data and compared to actual dose-rate measurements. Primary beam tenth value layer values derived from the broad-beam measurements are found to represent the attenuation properties of the MagnaDense more accurately than those produced by density-based scaling or from narrow-beam measurements.

Quantitative assessment of the radiation hazards and risks in sentinel node procedures.

Sentinel node localization using an injected radiopharmaceutical and a gamma probe is performed in many hospitals. Employers have a duty to give appropriate training to staff who may not have been previously formally trained to work with unsealed radioactive sources. A study was performed to assess hazards and risks at all stages of the localization procedure. Whole body doses and finger doses of imaging, surgery and pathology staff were determined. The activity remaining in the tumour specimen, excised nodes and disposable waste from the operating theatre was measured. Any radioactive contamination of the operating theatre and equipment was also ascertained. All results were then assessed in light of current UK radiation protection legislation for the protection of staff and members of the public. Results showed that radiation doses are low and no additional procedures are required for protection of staff, provided the usual procedures for biohazards are in place. However, an information sheet has been prepared for the reassurance of staff, and theatre swabs may need to be stored temporarily before disposal. Injecting and imaging on the day before surgery is preferred, compared with injecting and imaging before surgery on the same day, since this gives lower radiation doses to staff, lower activity in excised specimens and waste, and provides a higher count rate giving better image quality.

Quality assurance and harmonisation of nuclear medicine investigations in Europe.

A survey of all member societies of the European Association of Nuclear Medicine has shown that a satisfactory degree of harmonisation exists for the quality assurance of the preparation and handling of radiopharmaceuticals and the performance of nuclear medicine instrumentation. However, variations were found in acquisition protocols, data analysis and the interpretation and presentation of clinical results. Harmonisation of these areas of a nuclear medicine investigation would help ensure the overall quality. A European initiative is proposed to collect and collate procedures in these areas in order to produce a reference framework of good practice for the acquisition, analysis and interpretation of nuclear medicine investigations. This would involve collaboration between national societies and exchange of information with and support from European organisations, taking into account relevant international activities. The reference framework should be compatible with quality management guidelines.

Extremity doses during interventional radiology.

The radiation doses received by the unprotected parts of a radiologist undertaking biliary and renal interventional techniques using an overcouch X-ray tube have been measured with thermoluminescent dosimeters. Mean doses to the eyes, thyroid and fingers ranged from 0.27 to 1.29 mSv per examination. The results substantiate the need for such monitoring but the study demonstrates that the doses to the radiologist can be kept to an acceptable level with careful technique.

Variability of ejection fraction results using commercial cardiac phantoms.

Variable ejection fraction results were obtained using two commercial phantoms with three different computer systems. The reasons for the results and their implications are discussed.

Improved accuracy of ejection fraction measurements using a commercial cardiac phantom.

Variable ejection fraction results were obtained with a cardiac phantom using different computer systems. The problems was traced to the phantom design. A modification produced more reliable results consistent with expected values.

Defects in intrathyroid binding of iodine and the perchlorate discharge test.

The kinetics of [123I]iodide uptake were studied when organification of iodine by the thyroid gland was normal and when this binding function was diminished by drugs or disease. Each study was terminated by a sodium perchlorate discharge test (300--600 mg iv) at 60 min or, in some cases, 10--30 min. The results confirmed that binding takes place rapidly in the uninhibited gland with the binding rate constant being at least 0.150 min-1. Discharge from the uninhibited gland is less than 3.5% of the gland uptake when perchlorate is given 60 min after the radioiodide. Subjects with an intrinsic binding defect manifested discharges of 11% of greater of the 60 min uptake and the estimated binding rate constants ranged from 0.003--0.057 min-1. Thyrotoxic subjects receiving 5 mg carbimazole twice daily manifested discharges ranging from 5.4--64.2%, and in those receiving 20 mg twice daily the observed discharges were 67.6--94.6% of the 60 min uptake. The study shows that a correctly performed perchlorate discharge test will detect minimal inhibition of iodine binding. An important factor is the duration of the follow-up period after perchlorate is given. In some of the cases studied discharge was not complete until 60 min after the perchlorate.

Antiprostaglandin synthetase activity of nonsteroidal anti-inflammatory drugs and gastrointestinal micro-bleeding: a comparison of flurbiprofen with benoxaprofen.

By using 51Cr-labelled erythrocytes and 141Ce-labelled microspheres to correct for daily variations in faecal output, gastrointestinal microbleeding was measured in hospital patients with rheumatoid arthritis before and after administration of 2 propionic acid derivatives. These were flurbiprofen and benoxaprofen, respectively a potent and a weak prostaglandin synthetase inhibitor. Increased faecal blood loss occurred consistently with flurbiprofen and not with benoxaprofen. Our results provide indirect evidence for the cytoprotective effect of prostaglandins on the gastrointestinal mucosa in man. The quantitative correlation between faecal occult blood loss as measured by the above techniques and the Haemoccult slide test is also discussed.

Assessment of total and divided renal plasma flow by 123I-hippuran renography.

We studied 23 patients with suspected renal hypertension, including 12 with renal artery stenosis, or occlusion. Total effective renal plasma flow (ERPF) was measured in all patients by conventional p-aminohippurate (PAH) clearance and by 123I-hippuran clearance performed on the same day. A close correlation between the two techniques was obtained (r = 0.87, P less than 0.001) with the latter technique underestimating the former by a mean ratio of 0.89:1.00. We describe a technique for deriving ERPF for individual kidneys by 123I-hippuran renography, and the data obtained by this method correlate well with data obtained from bilateral ureteric catheterization studies (r = 0.076, P less than 0.001 for both affected and unaffected sides) in 17 patients. The renographic technique is particularly accurate in quantitating ERPF in the 12 patients with renal artery stenosis, and is recommended as the investigation of choice in the assessment of ERPF in patients with this condition.

Quantitation of thyroidal binding of iodide by compartmental analysis verified by an intravenous perchlorate discharge test.

Compartmental analysis was applied to 123I-iodide uptake data to quantitate iodine binding in the human thyroid gland. The method allowed for arterio/venous differences in plasma tracer level and for an "instantaneous" phase of thyroid uptake. Results were checked by an intravenous perchlorate discharge test. Observations in eleven normal and untreated thyrotoxic subjects confirmed earlier findings that iodine binding takes place rapidly, the binding rate constant being much greater than the exit rate constant. A lower limit of 0.15 min-1 for the binding rate constant in the uninhibited gland was estimated from the observations in one subject who demonstrated a small perchlorate discharge. The method was used in the study of eight subjects with an intrinsic binding defect and of twenty-four thyrotoxic subjects being treated with 5 mg or 20 mg carbimazole, twice daily. Binding rate constants (range 0.003--0.105 min-1) were typically less than the exit rate constants (range 0.027--0.156 min-1), the net clearance of iodide ranging from 1.5 to 67.9% of the unidirectioinal clearance, compared to 72% in the uninhibited gland. The method proved useful in assessing the severity of an intrinsic binding defect and in the investigation of lack of response to antithyroid drug therapy.

Monitoring of airborne contamination during the handling of technetium-99m and radioiodine.

Measurements have been made using an air sampler to measure airborne radioactivity produced during the routine handling of large activities of technetium-99m, iodine-125 and iodine-131. The results indicate that 99Tcm can be safely handled in environments without direct exhaust of the ventilated air but that 125I and 131I should always be handled in a ventilated environment such as a fume cupboard or a down-draught work-station of the total-exhaust type. Monitoring of thyroid uptake proves to be the most reliable means of monitoring airborne contamination by these radionuclides, but burdens and radiation doses for typical procedures are well within the maximum permissible limits of the Code of Practice for the Protection of Persons from Ionizing Radiation arising from Medical and Dental Use.

Clinical comparison of three liver scanning agents.

The biological distributions of 99mTc-sulphur colloid, 99mTc-tin colloid and 99mTc phytate colloid were quantitatively compared in a randomised trial. All three radiopharmaceuticals gave satisfactory liver images. There is evidence to suggest that the phytate colloid significantly underestimates splenic uptake. The tin colloid was easier to dispense than the sulphur colloid and was found to be the most suitable radiopharmaceutical.

The clinical comparison of skeletal imaging agents.

99-MTc-methylene diophosphonate from two manufacturers was compared with 99mTc-ethane hydroxy diphosphonate in a randomised trial to assess the relative blood clearances and the subsequent image quality. The 99mTc-methylene diphosphonate preparations were found to be superior with respect to both blood clearance and subjectively assessed image quality, particularly when the interval between injection and scanning was three hours. Bone/soft tissue ratios did not mirror the highly significant qualitative comparisons of image quality.

Colon blood flow in the dog: effects of changes in arterial carbon dioxide tension.

A new method for measuring blood flow in the colon using a 133Xenon clearance technique has been developed in the greyhound. Values for 133Xe tissue blood partition coefficient for colon have been established. The mean basal colon blood flow in 35 animals was 39.8 cm3.min-1.100g-1 with a coefficient of variation for repeat measurements of 8.7%. Hypercapnia produced a significant rise in colon blood flow to a mean maximum level of 62.2 cm3.min-1.100g-1 and hypocapnia a significant fall to a mean level of 27.9 cm3.min-1.100g-1. For arterial carbon dioxide tension (PCO2) values between 2 and 12 kPa (15 and 90 mmHg) there was a straight line relationship between colon blood flow and arterial PCO2. When hypercapnia was prolonged for 75 min, the initial rise in colon blood flow was only partially sustained, while prolonged hypocapnia for a similar period resulted in sustained reduction in flow. Mean resting colon oxygen consumption in 35 animals was 1.17 cm3.min-1.100g-1 and this was not significantly affected by hypocapnia. Hypercapnia to arterial PCO2 levels between 8 and 14 kPa (60 and 105 mmHg), however, produced a significant rise in colon oxygen consumption. Since changes in colon blood flow during and after surgery may affect healing of colonic anastomoses, these results may be relevant when considering anaesthetic techniques for patients undergoing colon resection.

Theoretical of the measurement of choroidal blood flow using a radioactive inert gas clearance technique.

A mathematical model for the diffusion of krypton in ocular tissues and its removal by blood flow has been developed to explain the complex clearance pattern found experimentally in the rabbit--an animal which has predominantly a choroidal circulation. Comparison of theoretical and experimental results has shown that the initial slope of the clearance curve is a measure of choroidal blood flow for values of blood flow over 500 ml/100 g/min. The shape of the curve at later times has been shown to be attributable predominantly to the diffusion of krypton into other ocular tissues.

Scintiscanning in ankylosing spondylitis: a clinical, radiological and quantitative radioisotopic study.

Twenty-six patients with ankylosing spondylitis and 10 control subjects had quantitative dorso-lumbar and sacroiliac scintigraphy performed using 99mtechnetium methylene diphosphonate. No difference was found in the mean uptakes of radionucleide at each vertebral level or in the sacroiliac joints between the diseases patients and controls. No correlation was found between radionucleide uptake and radiological score, pain and tenderness assessments. The large variation in quantiative measurements resulted in a large overlap between control and diseased patients and it is unlikely that scintigraphy will be of diagnostic value in the absence of improved methodology.

The value of the 14C breath test in the assessment of fat absorption.

The absorption of oral 14C-glyceryl tripalmitate was tested in 77 subjects by hourly interval sampling of breath 14CO2 for up to 6 h. A highly significant correlation was obtained between maximum breath 14CO2 activity and faecal fat excretion. The test was very effective in differentiating between patients with and without steatorrhoea. Repetition of this examination with oral 14C-palmitic acid demonstrated normal absorption in pancreatic steatorrhoea but impaired absorption in intestinal steatorrhoea, thus enabling these conditions to be distinguished. The 14C breath tests are most useful as simple and inexpensive outpatient screening tests for steatorrhoea.