1950s radiotherapy physics

Radiotherapeutic physics

An interesting symposium on radiotherapeutic physics took place at the 6th International Congress of Radiology in 1950 and a selection of the papers appeared in the BJR of July 1951. These included FW Spiers from Leeds who wrote on dosage measurements in irradiated bone and soft tissue (Spiers BJR 1951; 24(283): 365-370) and  CW Wilson from the Middlesex Hospital wrote on recent developments in teleradium therapy (Wilson BJR 1951; 24(283): 374-380). The Westminster Hospital had had two radium mass units in use since 1936. WG Meredith reviewed dosage control in interstitial gamma ray therapy (Meredith BJR 1951; 24(283): 380-384). This particular branch of radiotherapy physics had received more attention in the UK than other countries.

Artificial radioactive sources for interstitial therapy were reviewed by WK Sinclair from the Royal Cancer Hospital in August 1952 (Sinclair BJR 1952; 25(296): 417-419). These agents were short lived and had many clinical advantages. HJ Hodt and DW Smithers from the Royal Cancer Hospital described a gun for implanting radioactive gold grains in August 1952 (Hodt, Sinclair and Smithers BJR 1952; 25(296): 419-421). Radioactive gold grains replaced the older radon seeds. DM Wallace and others from the Royal Cancer Hospital then described the use of radioactive tantalum wire for bladder cancer (Wallace, Stapleton and Turner BJR 1952; 25(296): 421-424).

The planning of radiotherapy treatments necessitates the calculation of the absorbed dose to be given to the target volume that is to be treated. The manual calculation involves superimposing the isodose charts from the radiotherapy machine and this is a long and laborious process. In August 1955 a paper by KC Tsien from New York was published on the application of automatic computing machines to radiation treatment planning (Tsien BJR 1955; 28(332): 432-439).Tsien analysed the problems encountered in calculating treatment plans and this paper marks a milestone in radiotherapy treatment planning.

Problems encountered in calculating radiotherapy treatment plans 

Image source: Tsien BJR 1955; 28(332): 432-439

 

The measurement of radiation

Jack Boag from Hammersmith Hospital wrote about the saturation curve for an ionization chamber exposed to pulsed radiation in October 1950 (Boag BJR 1950; 23(274): 601-611) and December 1952 (Boag BJR 1952; 25(300): 649-650). This was a topic that interested Boag and he returned to it in May 1980 (Boag and Currant BJR 1980; 53(629): 471-478) when he found that his existing theory of 1950 was accurate over the range of charge densities then examined. In October 1950 he described his ionization measurements of pulsed radiation beams at very high intensities (Boag BJR 1950; 23(274): 601-611). In June 1951 he described ionisation chambers for electron dosimetry (Boag, Pilling and Wilson BJR 1951; 24(282): 341-344).

By the 1950s the use of ionization to measure X-ray intensity was well developed and the history of this achievement of radiation dosimetry was well reviewed by Edith Quimby in January 1951 (Quimby BJR 1951; 24(277): 2-5). The Silvanus Thompson Memorial Lecture for 1950 was given by Lauriston Taylor from the National Bureau of Standards in the USA and he reviewed the measurement of radiation  (Taylor BJR 1951; 24(278): 67-81). EE Smith from Sutton reviewed the standardisation of X-ray dosemeters in December 1955 (Smith BJR 1955; 28(336): 662-669) and discussed the problems involved with the original NPL standard free-air chamber of 1930.

 Unit of Xray Dose

Image sourcxe: Smith BJR 1955; 28(336): 662-669

 

The Baldwin-Farmer Sub-Standard Dosemeter

In June 1955 Frank Farmer from Leeds described his “Sub-Standard X-ray Dose-Meter” (Farmer BJR 1955; 28(330): 304-306). The instrument had been in use for several years before Farmer published this account. Whilst the dosemeter was designed for the calibration of X-ray therapy machines it had been found useful in many other areas. It was based on a thimble ionisation chamber and was found to be both reliable and stable.  It became the standard instrument for most radiotherapy departments and was made by the Baldwin Instrument Company.

 

Nuclear medicine

The discipline of nuclear medicine was in its infancy in the 1950s. In 1950 the BJR published Supplement 2 “Some Applications of Nuclear Physics to Medicine” by WV Mayneord. Mayneord had given a series of lectures to the Institute on this topic. The term “Nuclear Medicine” is a contraction of Mayneord’s title. A symposium was held on the diagnostic and therapeutic use of radioactive isotopes and the papers appeared in the BJR. They are a fascinating account of knowledge at the start of a new discipline. N Veall from Hammersmith wrote on the measurement of radioactivity and there is an illustration of the measurement of thyroid uptake of radioiodine (Veall BJR 1950; 23(273): 527-534). CP Haig from Bristol Mental Hospitals looked at clinical diagnosis (Haig and Reiss BJR 1950; 23(273): 534-541) an investigated thyroid function and performed early brain analysis. Joseph Rotblat and R Marcus from Liverpool (Marcus and Rotblat BJR 1950; 23(273): 541-549) examined a case of multiple melanomas and considered if internal irradiation from a radioactive isotope might be of value in treatment by being concentrated in the tumour. Alastair Macgregor from Sheffield assessed radioiodine in the diagnosis of thyrotoxicosis (Macgregor BJR 1950; 23(273): 550-553). Ralston Paterson from Manchester reviewed its use in the treatment of thyroid cancer (Paterson BJR 1950; 23(273): 553-556) and HC Warrington from Manchester presented their preliminary treatment results (Warrington BJR 1950; 23(273): 556-559). The Manchester group had been using radioiodine and had treated 21 patients in 1949. RJ Walton described the use of radioactive isotopes at the Royal Cancer Hospital  (Walton BJR 1950; 23(273): 559-566) where they had been putting radioactive sodium into the bladder and using radioactive phosphorus for polycythaemia vera. Finally RG Blomfield from Sheffield gave his experience of radioiodine in thyroid disease (Blomfield BJR 1950; 23(273): 566-568).


In August 1951 Edward Pochin gave a full report of discussions on radioiodine treatment in thyroid cancer (Pochin BJR 1951; 24(284): 461) and by this time over 300 patients had been treated with radioiodine. In 1956 with Gwen Hilton, RM Cunningham and Keith Halnan he jointly gave the Mackenzie Davidson Memorial lecture on the radioiodine treatment of thyroid cancer (Hilton, Pochin, Cunningham and Halnan BJR 1956; 29(342): 297-310).

Radioiodine treatment of thyroid cancer

 

Image source: Hilton, Pochin, Cunningham and Halnan BJR 1956; 29(342): 297-310

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