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Biomedical subjects

N G Trott

Publications and source records attributed to N G Trott.

At least 19 recordsLinked to original sources

Radiology, physical science, and the emergence of medical physics.

The early development of medical physics as a separate discipline and profession is briefly reviewed. Although both x rays and radioactivity were discovered by physicists, at first the physical investigations of these phenomena, and their medical applications, proceeded along parallel but independent lines. Radiological journals were founded in Britain, Germany, and the U.S. as early as 1896-1897 but it was not until ten years later that papers on radiation physics began to appear regularly. In 1913 the first full-time physicists were appointed to posts in medical schools and hospitals: William Duane in the U.S. and Sydney Russ in Britain. Thereafter the number of physicists engaged in medical applications increased slowly but steadily, and in the 1920s they began to apply the new science of radiation dosimetry to both x ray and radium therapy. The "Hospital Physicists' Association" was founded in Britain in 1943 with 53 members and the "American Association of Physicists in Medicine" followed in 1958 with 127 charter members.

Biophysics↗

Blood cell labelling. Theory and methods: radiation hazards.

The chief physical properties of the radionuclide In111 are outlined, and compared with those of three other radionuclides, Tc99m, I131 and Cr51 which have similar applications. It is pointed out that the gamma-rays of In111 are appreciably more penetrating in lead than those of Tc99m and the significance of this, both in the use of shielding on syringes and in the effectiveness of lead glass screens is discussed. Examples are given of the dosimetry for In111 labelled cells in humans and it is noted that the absorbed dose in the spleen per mCi (37 MBq) injected may be some 10 rad (0.1 Gy). The problems that have been noted of damage to cells arising from oxine labelling and now considered to be due to radiation damage are briefly reviewed.

Blood Cells↗

The limitations of the dual radionuclide subtraction technique for the external detection of tumours by radioiodine-labelled antibodies.

A dual radionuclide subtraction technique for external detection of tumours has been evaluated to determine the viability of the method for use with radioisotope labelled antibodies. A number of external scintigraphic investigations have been carried out with 131I-labelled antibodies to carcinoembryonic antigen (CEA). The investigations were performed on patients with metastatic disease known to produce CEA. The dual radionuclide subtraction technique was used to account for the blood and tissue background. The 131I-labelled antibodies were found to localise in the metastatic lesions, but the subtraction technique using 99Tcm-labelled HSA and pertechnetate gave ambiguous results, which included the production of artefacts. The ambiguities noted in the clinical results were substantiated by experimental data, which highlight the unreliability of this technique.

Antibodies, Neoplasm↗

Feasibility of absolute activity measurements using the Cleon emission tomography system.

Large volume and small discrete sources of Tc-99m were used to study the spatial resolution, sensitivity, linearity and reproducibility of the radionuclide brain images. The spatial resolution is constant both within and perpendicular to the section. For uniform distributions of activity the response is uniform over the field of view, and the mean pixel count rate is a linear function of the radioactive concentration and is independent of the diameter of the source. However, for discrete sources, the sensitivity was found to vary with the position of the source, and the potential of the system for quantitative assessment of the uptake of radioactivity in organs and tumors was limited initially. Later studies, with modified software, show that this undesirable effect has been reduced.

Brain↗

The application of a digital whole body scanner to the dosimetry of intralymphatic 32P/131I Lipiodol.

A quantitative, digital-output, whole-body scanner in a low background area has been used in the dosimetry of 32P/131I Lipiodol for intralymphatic radiotherapy. Five patients with malignant melanoma received intralymphatic administrations of Lipiodol labelled with 6 mCi 32P and 1.5 mCi 131I. The 131I is used primarily as a tracer for external measurements and the 32P as the chief therapeutic agent. Whole body scans were made at intervals for up to 15 days using the digital scanner, with the spectrometer set over the 364 keV photopeak of 131I. On the same occasions complete gamma-spectra were obtained for these patients using a 2 m arc, single detector whole body counter. The method used in estimating the activity at various sites in the body from the digital whole body scans is described and problems that arise in using 131I as a tracer for 32P Lipiodol in this work are discussed. For the administered activities mentioned above, maximum absorbed doses to the lymph nodes were found to range from 30-96 krad with a mean value of 51 krad. Uptake of radioactivity was also found in the lungs, resulting in absorbed doses of 350-960 rad with a mean value of 540 rad.

Adult↗

The end of the rad?

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Radiation Protection↗

Iron metabolism in patients undergoing regular dialysis therapy.

Thirteen patients with chronic renal failure maintained on regular renal dialysis were studied. Seven proved to have iron deficiency on the basis of marrow iron studies, reticulocyte iron uptake, and saturation of the serum iron-binding capacity. They absorbed iron when given it by mouth and were able to utilize it for haemoglobin formation. Iron-deficient patients given 600 mg of ferrous sulphate daily for three months showed an increase in haemoglobin, but the failure to replace stores of iron is probably related to their relatively limited ability to absorb iron and the variable but sometimes considerable blood loss occurring with each dialysis.The loss may be occult, and prolonged iron therapy may be required. This is most safely achieved by giving iron by mouth.

Adult↗