I am delighted to have been asked to participate in the 1989 Annual Conference of the Canadian Nuclear Association and the Canadian Nuclear Society and to help commemorate the discovery of fission fifty years ago. It is because of this discovery that I have had the opportunity of being associated with a part of the medical industry that has utilized fission products for the benefit of man.
Every year nearly one million nuclear medicine procedures are carried out in Canada alone, while around the world, over a half a million cancer patients are treated annually with cobalt therapy units designed and developed by AECL. Canada has played and continues to play an important role in nuclear medicine and radiation therapy. I am proud of the fact that these two disciplines occupied my full attention throughout most of my years as a student and then as medical physicist with the Saskatchewan Cancer Foundation and the University of Saskatchewan.
It is my intention today to briefly describe two early developments in nuclear medicine and then conclude with my recollection of the early days of the first two cobalt units. Time does not permit an overview of all aspects of the clinical uses of radionuclides but I do know that Dr. Wilkinson will undoubtedly do so in his paper at this conference.
I am finding the career change from medical physicist to Lieutenant Governor of Saskatchewan to be both interesting and exciting. One of the perks of office is an invitation to visit with the Queen at Buckingham Palace. Often while in Europe I have stood outside the palace gates, like every tourist, and watched cars come and go and wondered about the occupants who were lucky enough to visit the palace. Well, my turn is coming - I will be in the car and tourists will stare at me and wonder, "Now who can she be?"
If I could answer, I would tell them that I am a girl from Saskatchewan who considers herself a lucky person to have been able to study and work as a physicist during the pioneering days of the use of high energy radiation in the treatment of cancer and the use of radionuclides in the diagnosis of disease.
I was a graduate student of Dr. Harold Johns, and following graduation from the University of Saskatchewan, I became his assistant at the Saskatoon Cancer Clinic in 1951. The following year, Dr. Johns arranged for me to tour several radiological centres in the United States. During the two month tour, which incidentally cost less than a thousand dollars, I became aware of the growing interest in the use of radionuclides to diagnose disease. It was an exciting time in the world of medical physics: high energy accelerators such as the betatron were being used to treat cancer; cobalt units were just beginning to be tested clinically; scintillation crystals and photomultiplier tubes were more readily available to university laboratories, and radiopharmaceuticals were beginning to appear on the market.
During my visits with Dr. K. Corrigan at the Harper Hospital, Detroit, and Dr. G. Bromnell at Massachusetts General Hospital, Boston, I observed pioneering work in the measurement of thyroid uptakes and external localization of brain tumors. The visit to the Oak Ridge Institute of Nuclear Studies introduced me to problems being encountered with instrumentation and standardization. It was at Oak Ridge that I met Dr. Marshall Brucer who was just as interested in what we were doing in radiation therapy in Saskatoon as I was in the many interesting projects underway at the Oak Ridge Laboratory.
It was the same Marshall Brucer who made me aware of the confusion surrounding measurement of thyroid uptake - that there were some one thousand physicians throughout the world trying to do a simple procedure and most were obtaining the wrong results. It appeared to be a simple procedure - two identical aliquots of 1-131 were prepared - one was given to a patient to drink and the second vial was kept as a "standard". The patient returned twenty four hours after drinking the atomic cocktail. An external detector was then positioned near the thyroid gland and the count-rate observed over the thyroid was compared to the count-rate recorded for the standard. In this way, the percentage of iodine taken up by the thyroid indicated whether the gland was functioning in a normal manner (20 to 40%), hyperthyroid condition (over 40%), hypothyroid (0 to 20%).
It was only after the Oak Ridge Group undertook a world wide study using a bevy of mannekins (Fig. 1 - these beauties had names such as Drusila, Hortense and Lulu) that it was realised that there was a large variation in the measurement of uptake in various labs. The mannekins were shipped to over 300 laboratories where indeed the large variation in the uptakes measured in the labs was quickly demonstrated. The Saskatoon Cancer Clinic was an active participant in the Canadian Group which included Dr. Sternberg in Montreal and Dr. Harold Johns in Toronto.
Figure 1: Mannekins used in a worldwide study of the iodine uptake in the thyroid
It was during the 1952 tour that I attended the annual meeting of the Radiological Society of North America in Cincinnati and listened to Dr. B. Cassen who described a new rectilinear scanning device. The machine had a scintillation detector mounted on a motor driven trolley. The trolley was driven in the X and Y directions, and when placed over the neck of a patient who had been given 1-131 the scintillation counter scanned the neck, recording the amount of radiation seen by the detector in its travel. The recording was done by a mechanical stamping device activated by the scaling unit. The stamper recorded a larger number of strokes on a sheet of carbon-backed paper when over the area of high activity, such as the gland itself, than over the areas of low activity in the tissue surrounding the gland. Scan speed was constant and so a positive impression or scintigram was obtained of the gland itself.
The paper was the hit of the meeting because, up until the meeting, external mapping of the thyroid was carried out in a very primitive way using a hand-held detector. Within a year, the first commercial unit was on the market and we were very fortunate to obtain two such units for the Saskatchewan program (Fig. 2).
Figure 2: One of the world's first commercial units located in Saskatchewan, to detect 1-131 in the neck of a patient.
The original detector used a 1/4" x 3/4" thick scintillator and a single hole aperture. As larger crystals became available, our interest in improving sensitivity, resolution and data recording led to the acquisition of a 2" x 2" crystal, a multi-focusing collimator and the use of pulse height analysis (Fig. 3). In addition, the mapping device was replaced with a light source which exposed a sheet of X-ray film to produce photoscans - scanning of the liver in search of metatastic cancer became a required test in the Saskatchewan program.
Figure 3: An early pulse height analyser and multi-focusing collimator.
As the crystals became large, the rectilinear scanner grew in size. This slide (Fig.4) shows the Saskatoon whole body scanner which had a 4" x 5" NaI(Tl) crystal shielded by 5" of lead. The number of holes in the focusing collimator had been increased to 37 and raw data were stored on magnetic tape. The data were processed and images such as that of a kidney scan (Fig.5) were produced by photographing the oscilloscope screen. An abnormality is shown in the left kidney (displayed on the right).
Figure 4: The Saskatoon whole body counter.
Figure 5: The results of a kidney scan with abnormality seen in the left kidney shown on the right.
It was in the late 1950's that Harold Anger at UCLA reported on his development of a scintillation camera (Fig. 6). The camera used a pinhole collimator and the location of each scintillation event occurring in the single crystal was identified in a similar location on the face of an oscilloscope screen. Thus rectilinear scanning, was being replaced by electronic scanning with the patient and camera remaining stationary during the imaging procedure.
Figure 6: Schematic of Harold Anger's scintillation camera.
Figure 7 is a photograph of a camera that was developed in Saskatoon by T.D. Cradduck as a Ph. D. project and used an 11" x 1/2" thick crystal and 19 photomultiplier tubes (Fig. 8). The camera enabled us to study the resolution and sensitivity of scintillation cameras, and reports of our work received international attention. It also enabled us to learn first hand the horrors that can occur when a Nal crystal is exposed to a sudden change in temperature during our cold Saskatchewan winters. Today equipment in Saskatoon is located in imaging rooms that have no windows which can be left open during the night.
Figure 7: The scintillation camera developed by T.D. Cradduck in Saskatoon.
Figure 8: Photomultiplier tube assembly of Cradduck's scintillation camera.
However, by this time, commercial cameras were mushrooming on the market and the unit shown here was purchased for the Saskatoon Cancer Clinic (Fig. 9) and by the middle 1970's, rectilinear scanning was a thing of the past, having been replaced by large crystal cameras with multiaperture collimators.
Figure 9: Commercial scintillation camera at the Saskatoon Cancer Clinic showing W.B. Reid on the right with a patient.
The gentleman on the right in Fig. 9 is Dr. W.B. Reid, a dear friend and colleague who passed away only five weeks ago. Bill, as a graduate student along with Dr. W. Feindel and Dr. H.E. Johns, developed a unique brain scanning device (Fig. 10). It was a departure from the rectilinear approach and had two detectors that scanned the contour of the head in search of brain tumours. The head was scanned in nine arcs (Fig. 11) and the counts as recorded by each detection system were compared to produce an image shown in (Fig. 12) where a localization has been recorded in the right hemisphere.
Figure 10: Brain scanning device developed by W. Feindel, H.E. Johns and W.B. Reid.
Figure 11: Schematic of the nine areas scanned by the device of Feindel, Johns and Reid.
Figure 12: Image produced from a head scan with the device of Feindel, Johns and Reid.
There were only three of these units built and these were used successfully for about 15 years in Saskatoon, in the Montreal Neurological Institute and in Princess Margaret Hospital in Toronto. This machine was ahead of its time and never received much international attention. I often wonder what might have happened if microprocessor technology had been available in 1956 when the unit was first put into use. Today the microprocessor is a vital component in camera imaging as is evidenced in this brain tumour localization (Fig. 13).
Figure 13: A brain tumour localised by a modern day camera with microprocessor controls.
In 1948, The University of Saskatchewan acquired a 22 MeV Allis Chalmers Betatron to do nuclear physics research and investigate its usefulness in treating deep-seated cancer (Fig. 14) and thus began the first real clinical testing of multimegavoltage therapy. The first patient was treated on 29 March 1949 and, as M.D. Schultz (A.J.R. 124: 541-549,1975) said: "... thus started the first really concerted clinical investigation of the usefulness of multimegavoltage as a radiotherapeutic tool." In 17 years only 301 patients were treated.
Figure 14: The 22 MeV Allis Chalmer Betatron acquired by the University of Saskatchewan in 1948
It was also in 1949 that Dr. Harold Johns turned his attention to using cobalt-60 as a radiation source in teletherapy equipment. His application to NRC for the source resulted in a letter from Dr. W.B. Lewis (Fig.15) which indicated that some doubts were being expressed about the wisdom of applying cobalt in this way for therapeutic work.
However, the application was approved and in fact three sources were placed in the reactor in 1949. From a rather shaky beginning, Canada has gone from scratch to becoming the world's largest supplier of medical isotopes. Through AECL, Canada supplies about 80% of the international market for cobalt 60. It is a Canadian story and in particular for someone from Saskatchewan, very much a Saskatchewan story.
So often many of our good ideas are exported and someone else picks up the glory. However, as far as cobalt-60 is concerned, it is a story of where we, as Canadians, have exploited original work done in Canada. The precise chronology of the development of cobalt-60 teletherapy devices is somewhat befogged by differences in how people remember things as they were. There were, however, three principal stages and sets of actors - one in the United States and two in Canada - and the Canadians prevailed.
The beginning of our story comes with Canadian nuclear research during World War II. A new reactor became operational at Chalk River and it was the only installation in the world capable of producing large quantities of radioactive cobalt. Three sources - one for the U.S. and the other two for Canada, were put into the reactor to cook in the fall of 1949. Two years later, two sources were made available by NRC's Atomic Energy Project for experimental and clinical use in Canada. The source destined to go to the U.S. was kept in the reactor and not released until the following year.
Each source, 1" in diameter, 1/2" thick, had an approximate strength of about 1000 curies. Two quite different units were designed to use these sources for radiation therapy.
This unit (Fig. 16) was designed by the development division of Eldorado Mining & Refining Limited. Chief designers were R.F. Errington and D.T. Green who, incidentally, was a graduate of the University of Saskatchewan. The unit was installed in the Ontario Cancer Foundation Clinic, Victoria Hospital, London, Ontario. The unit consisted of a head pivoted between the arms of a horizontal Y which could be raised and lowered. The beam was turned on and off by an air compressor that forced mercury in and out of the reservoir, the radiation beam being off when a pool of mercury was between the source and a conical opening in the head. Field size was varied by means of four lead blocks at right angles to each other.
Figure 16: Early cobalt-60 unit designed by R.F. Errington and D.I. Green from Eldorado Mining and Refining Limited. Installed in the Victoria Hospital, London, Ontario.
The Saskatoon unit (Fig. 17) was designed by Harold Johns and Lloyd Bates, a graduate student. It was built by Johnny McKay, Acme Machine & Electric, Saskatoon, for the Saskatchewan Cancer Commission and was installed in University Hospital, Saskatoon. The unit consisted of a steel-encased cylinder suspended from an overhead carriage. The source was mounted on the circumference of a wheel near the centre of the head so that by rotating the wheel, the source could be brought opposite an opening through which the radiation could emerge.
Figure 17: Cobalt-60 unit designed by H.E. Johns and L. Bates and built by J.McKay from Acme Machine and Electric, Saskatoon. Installed in the University Hospital, Saskatoon.
The Canadian sources were released in 1951. The summer and fall of 1951 became most memorable seasons that year in Saskatoon and London, Ontario. The cobalt race was on! The American source was left "cooking" in the reactor - they were left in the starting gate and the Canadians ran for the roses - Saskatoon jumped into an early lead. The Saskatoon group received the source on July 31,1951 and the Saskatoon Star Phoenix proudly proclaimed under this photo (Fig. 18):
"Wearing specially treated smocks and masks as protection against deadly gamma rays. Dr. Johns and Mr. McKay are seen transferring the radioactive source from the shipping container to the treatment head."
Figure 18: H.E. Johns and J. McKay loading their cobalt-60 unit in 1951
The room was hardly ready for use - plaster was still going on the walls, the concrete floor was yet to be poured, but the measurements began. The Saskatoon unit was officially opened on October 23rd and the measurements continued until November 8th when the first patient was treated by Sandy Watson.
Eldorado Mining & Smelting were most anxious for as much publicity as possible. After all, they were going to market their machine. Stories began to appear in the Eastern papers - Ivan Smith quickly treated the first patient in London, Ontario. Sandy Watson played down attempts to publicize the importance of cobalt - after all, "This is not a new thing in the fight against cancer, it is but a device that may be more efficient and economical to operate". However, he did allow MacLean's magazine to feature the Saskatoon unit with a headline for the story: The Atom Bomb That Saves Lives. The chronology of events in 1951 is shown in Table 1.
Ivan Smith passed Sandy Watson in the stretch. The battle of the cobalt bomb war was fought in the editorial pages of Canada's major newspapers. On November 7th the editor of the Star-Phoenix wrote: "We hope Messrs. Truman, Stalin, Peron et al. won't think someone is trying to steal their thunder, but we think they ought to know theirs is not the only atomic race going on in the world...with all due respect to the preservation of national peace and goodwill, that is a boast which this newspaper cannot allow to go unchallenged - especially since the Free Press is brazen enough to remark that a cobalt bomb 'is also being installed in Saskatoon, Saskatchewan'. One is indeed, or, to be more accurate, one has."
Scientific publications followed very quickly. The first article on the physical measurements carried out on both units appeared in the December 15th, 1951 issue of "Nature" by H.E. Johns, L.M. Bates, E.R. Epp, D.V. Cormack, S.O. Fedoruk (Saskatchewan Cancer Commission and Physics Department, Univ. of Saskatoon) and A. Morrison, W.R. Dixon and C. Garrett (Radiology Laboratory, Physics Division, National Research Council). The authors, all from Saskatchewan, tentatively said that cobalt units may prove to be very convenient sources of high energy radiation for therapy. More detailed papers were published in the Journal of the Canadian Asso- ciation of Radiologists in March 1952 and the British Journal of Radiology in June, 1952.
Not everyone shared Canada's optimism - after all, the American source was still in Chalk River.
In 1952 when teletherapy was being introduced to the manufacturers of therapeutic X-ray equipment, a poll was taken on how popular the new supervoltage cobalt-60 would be. One highly respected commercial consultantdidn't think the idea was very good and predicted that in ten years there would be only thirty machines in use. By 1981, there were about 2,200 units in routine use in the free world.
The Saskatoon unit was in service until 1972 when it was replaced by an AECL progeny (Fig. 19). In all, 6,728 patients were treated with a unit which gave us 21 years of quality service. The first patient that was treated in London died a few weeks later but the first Saskatoon patient who completed her full course of treatments on November 29, 1951, was alive and well thirty-seven years later and when she was asked regarding her condition in 1988, she replied "yes, all's well so far".
Figure 19: Cancer therapy unit produced by Atomic Energy of Canada Limited and installed in the University Hospital, Saskatoon in 1972.
Canadians played an important role in the development of the cobalt unit. Cobalt-60 teletherapy units were a means of making supervoltage widely available: part of its appeal was compactness. Though born of war-time nuclear research, the "bomb" was, in practice, a ploughshare rather than a sword. It was readily available, inexpensive both to purchase and maintain and, therefore, of potential value to developing countries.
Thank you for giving me an opportunity to walk down memory lane.
|Cobalt-60 source delivered||30 July||16 Oct|
|Unit installed||17 Aug||23 Oct|
|First patient treated||8 Nov||27 Oct|
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