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Biomedical subjects

D R Hamilton

Publications and source records attributed to D R Hamilton.

At least 37 records · Page 2Linked to original sources
PubMed1986

Childhood Kaposi's sarcoma in Papua New Guinea.

In the country of Papua New Guinea, with its diverse population of nearly 3 million people, some disease patterns have a strange similarity to those seen in tropical Africa. Kaposi's sarcoma is a condition which is commonly seen in adult males; childhood Kaposi's sarcoma is relatively uncommon. Six cases, all males, aged from 6 months to 12 years have been detected since 1978. The primary organ involvement included skin in four cases, oral cavity in one case and lymph node in one case. The varied clinico-pathological features are described. This is the first report of such cases from Papua New Guinea.

Child, Preschool↗
PubMed1984

A comparative study of radiation safety practices at selected hospitals in the UK and USA.

The radiation safety practices in a group of 25 UK and USA hospitals have recently been assessed. This took the form of detailed inspections of some 62 medical radiation departments, including Diagnostic X-ray, Radiotherapy, Nuclear Medicine and Pathology/Research (Radionuclide) Departments. Empirical expressions called "Radiation Safety Indices" were devised to evaluate the incidence of personal doses and radiological incidents occurring from 1977-82 and to characterise the safety facilities, procedures, supervision and educational techniques in each department. An outline is given of national legislative material and voluntary codes of conduct, together with the results of the departmental inspections. The computed indices are presented graphically and an analysis given of apparent national trends.

Accident Prevention↗
PubMed1983

Iodine-123 assay using a radionuclide calibrator.

Iodine-123 (123I), an accelerator-produced radionuclide, gained wide acceptance recently in medical applications. Radionuclide dose calibrators are commonly used to assay radioactivities of radiopharmaceuticals, and should be maintained to read within +/- 5%, both for constancy and accuracy. Radionuclidic impurities present in commercial 123I preparations may produce an assay error larger than 10%. The type and quantity of impurities depend on the mode of production of 123I. The impurities can be reduced by either increasing the energy of the proton beam (over 60 MeV) and using the 127I (p,5n) 133Xe leads to 123I indirect reaction or using lower energies and highly enriched (better than 99%) 124Te (or 122Te) target for the direct production of 123I via 124Te (p, 2n) 123I or 122Te (d, n) 123I. A survey of radionuclide calibrators was undertaken to investigate the extent of the 123I assay error due to impurities present in commercially available preparations of 123I. Results from 24 calibrators indicate that the activity of a (p, 2n) 123I capsule is overestimated on average by 22% two half-lives after calibration time, while the activity of a (p, 5n) 123I capsule remains within the accuracy of the radionuclide calibrator of +/- 5%. The 124I fraction increases significantly with time during the useful life of a (p, 2n) 123I capsule introducing large 123I assay errors.

Calibration↗
PubMed1982

Ruptured spleen in a malarious area: with emphasis on conservative management in both adults and children.

Sixty-two consecutive cases of ruptured spleen occurring in a malarious area and reviewed. Nineteen died before treatment could be commenced. all patients who survived the initial hypotensive episode, and who were admitted to our unit, recovered, whether managed operatively or nonoperatively. We have conserved 26 spleens and removed 17. One splenectomised patient is known to have died subsequently from cerebral malaria. Although four cases of delayed rupture were seen, no conservatively treated patient had a delayed haemorrhage. Our policy is to avoid removal of the spleen in malarious areas in both adults and children.

Adolescent↗
PubMed1982

Sori tumas: the decision not to treat.

I am convinced that one of the most important and difficult aspects of the work on a specialist surgeon in Papua New Guinea, is knowing when not to treat conditions that would be enthusiastically treated in other countries. Most of our patients would rather die at home than in hospital, and they appreciate and can accept an honest assessment of their prognosis.

Hospitalization↗
PubMedDate not supplied

MR imaging signal response to sustained stimulation in human visual cortex.

The response of signal intensity to transient (on-off) motor and sensory stimulation has been well studied; however, the dependence of signal response on the duration of stimulus requires further characterization. The objective of this study was to determine the time course of signal response in the human visual cortex to prolonged, sustained stimulation and to examine possible contributory physiologic mechanisms. Nine healthy volunteers underwent magnetic resonance (MR) imaging during sustained visual stimulation with light-proof binocular goggles. With photic stimulation, activation was observed in all subjects as an increase in signal intensity of the visual cortex. With sustained stimulation, a gradual decrease in signal intensity was subsequently observed, with progression toward an apparent steady state. Correlation with positron emission tomographic, MR spectroscopic, and visual evoked-potential data suggests that the initial uncoupling of cerebral blood flow and oxidative metabolism with a neuronal activation burst may represent a transient phenomenon. This quick-response phase may proceed to an equilibrium coupling of flow and oxidative metabolism, with a gradual normalization of venous deoxyhemoglobin levels and signal intensity.

Adult↗
PubMedDate not supplied

Abdominal compressions during CPR: hemodynamic effects of altering timing and force.

To determine the optimal method of applying abdominal compressions during cardiopulmonary resuscitation (CPR), 3 levels of pressure (25, 50, and 100 torr) were applied to the abdomen a) continuously and b) as 500 msec pulses at 10 different phases during the CPR cycle in 8 anesthetized dogs. Thoracic aortic (Ao) and right atrial (RA) pressures were measured and PAo-PRA was calculated as the coronary perfusion gradient. A pneumatic piston device provided external chest compression (60/min, 120 lbs, for 50% of the cycle) and ventilation (80% O2, 12/min, at 20cm, H2O). Another identical device provided abdominal compression (AC) via an air-filled bladder. High-pressure (100 torr) AC applied for 500 msec commencing 200 msec prior to chest compression demonstrated the best overall profile, raising mean aortic pressure 26 torr (P less than 0.001) and peak coronary perfusion gradient pressure 17 torr (P less than 0.02) from control values during standard CPR of 58 and 41 torr, respectively. We conclude that applying high-pressure, 500-msec pulses of AC 200 msec before chest compressions significantly improves CPR hemodynamics.

Abdomen↗