1940s radiotherapy physics

Irradiation of liquids

In June 1940 Frank L Hopwood spoke on the irradiation of liquids (Hopwood BJR 1940; 13(151): 221-226) for his Silvanus Thompson Memorial Lecture.  Hopwood was interested in the action of neutrons compared to beta and gamma rays and on the activation of water by irradiation.

Neutrons gamma ray irradiation chart

Source: Hopwood BJR 1940; 13(151): 221-226 

Hopwood was a pioneer in medical physics and W V Mayneord dedicated his article “Some Applications of Nuclear Physics to Medicine” (BJR Supplement No.2 1950) to him.

Frank HopwoodFrank Hopwood died in 1954 and his death is recorded (Stead BJR 1954; 27(318): 317).

 

 

Frank Hopward image source: (Stead BJR 1954; 27(318): 317).

 

The Second World War stimulated work on nuclear physics and led to the development and use of the atomic bomb. In 1946 J S Mitchell from Cambridge wrote about recent applications of nuclear physics to medicine (Mitchell BJR 1946; 19(228): 481–487). Mitchell saw the radioactive isotopes as being used as tracers to study metabolic processes, as radioactive sources for therapy and as agents with therapeutic properties related to their selective concentration in body tissues.

Radioactive isotopes for use in radiotherapy

Mitchell made a provisional calculation of the tolerance flux of fast neutrons in May 1947 (Mitchell BJR 1947; 20(233): 177–180) and experimented on their biological effects, publishing his results in September 1947 (Mitchell BJR 1947; 20(237): 368-380).

 

Radiotherapy machines

The apparatus used for radiotherapy developed rapidly in the 1940s.

Synchrotron accelerator

D A Fry from the Atomic energy Research Establishment in Harwell described the new Synchrotron accelerator in August 1949 (Fry BJR 1949; 22(260): 462–472). The synchrotron accelerates particles in a circular orbit and Fry discussed possible therapeutic uses.


Microwave linear electron accelerator

G R Newbery from the Hammersmith Hospital described the microwave linear electron accelerator in August 1949 (Newbery BJR 1949; 22(260): 473–486). Newberry reviewed linear accelerators and described such a machine that could work at 4 – 5 MeV. At that time there was no plan to develop such a machine for either experimental or clinical use. This was to change.

 

L H Gray and John Read

L H Gray from Mount Vernon Hospital and the Radium Institute in London published frequently in the BJR. In January 1940 (Gray BJR 1940; 13(145): 25–30) he published his work on the contribution of the photo-electrons of sulphur to X-ray ionisation. In March 1940 with John Read and J G Wyatt (Gray Read and Wyatt BJR 1940; 13(147:) 82-94) he is writing about a neutron generator for biological research. Neutrons had been discovered in 1932 and LH Gray had approached the British Empire Cancer Research Campaign in 1935 for finance for a project to find the mode of action of neutrons on biological material. It was his work on the distribution of ions across the track of a recoiling nucleus made it likely that the different biological actions of neutrons could be of use in therapy. Construction of a neutron generator had started in 1936 and this paper described the apparatus. In July 1940, and again with John Read, the subject of neutron emission from this 300kV generator was considered (Gray and Read BJR 1940; 13(151): 248–253) by Gray.

Lead instrument for neutron absorber and chart showing aborptionN

Neutron emmission from a generator operating at 300 KV. Image source: Gray and Read BJR 1940; 13(151): 248–253

In March 1941 with John Read and H Liebmann we find Gray comparing the effects of neutrons and gamma rays on the mobility of colloidal graphite particles (Gray, Read and Liebmann BJR 1941; 14(159): 102–106).

In December 1949 L H Gray was investigating a series of radioactive substances and looking at the emission of beta ray and gamma ray energy using ionisation methods (Gray BJR 1949; 22(264): 677–697).

In July 1949 John Read reviewed the lateral distribution of ions across the track of an ionizing particle (Read BJR 1949; 22(259): 366–374) and further considered the equilibrium in June 1951 (Read BJR 1951; 24(282): 345-347).

 

W V Mayneord

W V Mayneord continued to contribute the BJR in the 1940s. In July 1940 (Mayneord BJR 1940; 13(151): 235–247) wrote on energy absorption. This is an important topic and he was challenging what he thought were overly simplistic models of the time and he believed that the energy absorbed in a cell may not be the sole factor determining the biological effects of the radiation on that cell.  He returned to the topic in two papers written with J R Clarkson in May 1944 (Mayneord and Clarkson BJR 1944; 17(197): 151–157) and June 1944 (Mayneord and Clarkson BJR 1944; 17(198): 177–182) and they were particularly concerned with whole body irradiation. Mayneord again considered energy absorption and gave a mathematical theory of integral dose and its application to physics in December 1944 (Mayneord BJR 1944; 17(204): 359–367) and to radium in January 1945 (Mayneord BJR 1945; 18(205): 12-19).

His important paper on depth dose data appeared in August 1941 (Mayneord and Lamerton BJR 1941; 14(164): 255–264) with detailed appended tables. In August 1941 J R Clarkson from the Royal Cancer Hospital (Free) wrote on depth doses for irregularly shaped fields (Clarkson BJR 1941; 14(164): 265–268) with his method of calculation suggested by WV Mayneord.

 

Wax man for measuring intergral doseIn October 1943 Mayneord reviewed isodose surfaces (Mayneord BJR 1943; 16(190): 291–297) demonstrated using a variety of solid models.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Source: Mayneord BJR 1943; 16(190): 291–297

Mayneord is always interesting and had a thoughtful approach to his field on medical physics. His paper “What may we expect from physics?” of 1942 (Mayneord BJR 1942; 15(178): 286–288) is still very interesting. Mayneord was a team player with a strong belief in the need for cross speciality cooperation. He finishes the paper by saying “Finally then it seems that physics is likely to play an important part in medical radiology of the future, and we may look forward confidently to both technical and fundamental advances based upon the collaboration of physicist and radiologist” and this is the fundamental ethos at the heart of the British Institute of Radiology which Mayneord served so faithfully and is remembered in our eponymous lecture. Mayneord was inducted as BIR President in October 1942 (BJR 1943; 16(181): 1–2).

 

Jack Boag

Jack Boag from Hammersmith Hospital measured the energy absorbed by a patient during therapy in August 1945 (Boag BJR 1945; 18(212): 235–238) and found that the energy absorbed depended more on the area and size of the field and less upon the focal-skin distance, linear dimensions of the patient and half-value layer of the radiation. In March 1948 he surveyed the presentation an analysis of the results of radiotherapy (Boag BJR 1948; 21(243): 128–138) and gave the mathematical theory in April 1948 (Boag BJR 1948; 21(244): 189–203) and clinical features in June 1951 (Boag BJR 1951; 24(282): 299–304).

 Distribution of survival times of patients with cancer

Source: Boag BJR 1951; 24(282): 299–304

The Measurement of Radiation

Frank Happy described his universal dosemeter in October 1941 (Happey BJR 1941; 14(166): 336–340). His object was to design an instrument capable of measuring ionising currents of widely differing values.

 

Frank Farmer

Frank Farmer from the Middlesex Hospital wrote an interesting paper in July 1942 on the importance of reliable measurement in the use of radiation (Farmer BJR 1942; 15(175): 203–208). At the Middlesex Hospital they were using the thimble-chamber dosimeter, tube output calibrations or a fixed chamber integrating dosimeter. In May 1944 Farmer described a new integrating dosemeter (Farmer BJR 1944; 17(197): 160–162). In May 1945 Farmer developed a small condenser ionisation chamber that could comfortably be inserted into body cavities (Farmer BJR 1945; 18(209): 148–152). In January 1946 Farmer described his feed-back amplifier for ionization currents (Farmer BJR 1946; 19(217): 27–30).

Geiger counter

J D Craggs and J F Smee wrote an interesting account of tube counters and the Geiger-Müller counter in August (Craggs and Smee BJR 1942; 15(176): 228–232) and September (Craggs and Smee BJR 1942; 15(177): 243–248) 1942 explaining the principles involved.

 

Source: Craggs and Smee BJR 1942; 15(177): 243–248

One of the gamma ray counters is shown far right  in Fig. 11.

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