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Biomedical subjects

E G Aird

Publications and source records attributed to E G Aird.

15 recordsLinked to original sources
PubMed1995

Quality assurance in the CHART clinical trial.

As part of the clinical trial of CHART (continuous hyperfractionated accelerated radiotherapy) a quality assurance programme was included. The technical part of this--which is reported in this paper--is a series of tests designed to check all aspects of treatment planning and delivery. The results of visits to the 13 participating centres--and repeat visits to some of these centres--are discussed. The main areas tested were as follows. The linear accelerator: mechanical, and optical, scales and indicators; radiation field size; flatness and symmetry. DOSIMETRY: output; wedge factor; beam energy; phantom measurements against a plan calculated by the centre. SIMULATOR: mechanical, optical scales and indicators. The results show these centres work within the tolerances chosen for most parameters. Flatness, wedge factor and energy were areas of weakness in some centres. This must be partly the cause of the spread of phantom measurements which, after removal of variations in output, still range from -7 to +6% between calculated and measured values.

Bronchial Neoplasms↗
PubMed1992

A dosimetric intercomparison of megavoltage photon beams in UK radiotherapy centres.

A dosimetry intercomparison has been carried out for all 64 radiotherapy centres in the UK. Doses were measured with an ionization chamber in an epoxy resin water-substitute phantom of relatively simple geometry. Reference-point measurements were made for all MV photon beams. For 61 Co-60 beams, a mean ratio of measured-to-stated dose of 1.002 was observed with a standard deviation of 0.014, whilst for 100 MV x-ray beams, the corresponding figures were 1.003 and 0.015. 97% of beams lay within a +/- 3% deviation. One measurement was instrumental in discovering a large discrepancy. Doses were also investigated in two planned three-field distributions at one beam quality in each centre. One of these was in a homogeneous phantom, whilst the second included a lung-equivalent insert. Doses were measured at the central point and at four other points in the high dose volume. In both situations, the mean ratio of measured-to-calculated doses for all points was 1.008, with standard deviations of 0.027 and 0.035 for the uniform and non-uniform phantoms, respectively. Discrepancies over 5% were followed up. The work must be viewed in the context of other international intercomparisons and is an essential part of wider radiotherapy audit processes.

Humans↗
PubMed1988

Direct measurement of dose at depth in breast cancer using lithium fluoride.

In 23 cases of breast cancer treated conservatively using external beam and interstitial radiotherapy, lithium fluoride thermoluminescent dosimetry has been used to measure the radiation dose received by the breast tissue at depth. Thirty-six investigations were made using a number of lithium fluoride micro-rods for each investigation. Three results could not be analysed because of measurement problems in two and insufficient information in one. Twenty-eight results were obtained at a depth in tissue greater than the build-up zone, 23 of the 28 falling within +/- 5% and 27 of the 28 falling within +/- 10% of the computer-calculated prescribed dose. Of five results obtained within the build-up zone, two fell within +/- 5% and four within +/- 10% of the prescribed dose.

Brachytherapy↗
PubMed1985

Preliminary experience with iodine-125 seeds in Newcastle upon Tyne.

Iodine-125 is useful in curietherapy because of its advantages relating to radiation protection. Dosimetric systems for 125I are discussed. It is concluded that 12 000 cGy calculated by the Manchester system leads to acceptable late results. Nineteen patients were treated, mostly for palliation. Therapeutic benefit was seen in nine; one developed necrosis.

Brachytherapy↗
PubMed1977

Photon absorptiometry of bone after successful renal transplantation.

Photon absorptiometric measurements of the right lower femur were carried out at regular intervals of one to three months in 58 recipients of renal transplant. (1) During the first six months after transplant 57% showed a significant and abnormal rate of loss of bone mineral (mean 11.7% per year. +/- 1.1% S.E.M.) while 30 months' after transplantation only 17% showed such a significant loss (p=0.025). (2) Eighteen months after transplantation both male and female recipients of transplants had a significantly lower mean bone mineral index than controls (p less than 0.001). (3) Male patients who developed new post-transplant fractures had a lower mean bone mineral content compared with age and sex-matched controls taken from transplant recipients without such fractures (p less than 0.01). Similarly male patients with post-transplant fractures had a significantly longer mean period on regular haemodialysis (p less than 0.05) compared with patients without such fractures. Regular photon absorptiometric measurements provide an accurate, informative and non-invasive technique for following changes of bone mineral content after successful renal transplantation.

Bone Diseases↗