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A small portion of our patients are terminal patients. On these patients we feel impelled to take more extreme measures as, for example, the use of some of the less well known isotopes involving, in some cases, higher specific gravity.

We also felt that our program should be to do things that could not be done at other medical schools. An example of one phase of this internally administered isotope program is well illustrated by the use of the particulate matter injected into the body which would not spread; it was not soluble in the body fluids. The radioactive gold work that was started by Dr. Hahn was also started by Professor Mueller of Switzerland working with an entirely different isotope. He was injecting colloidal or a very small or just barely visible particle of zinc, or of gold into the body, and since those particles were insoluble, they would not go into solution. They stayed just about where they were put.

There are many difficulties in working with such substances. The use of colloidal gold has turned out to be very valuable within the last few years. Many schools are now using colloidal gold for such things as carcinoma of the prostate and for the carcinoma of the ovaries. For the pleural effusion (the water that develops in the pleural sac from such things as carcinoma of the breast) with a large amount of radiation put into these cavities you can sometimes stop the production of fluid. This does not cure the cancer, but it makes the patient comfortable, up to 2 years, in some cases, and in about 30 percent of the cases it has been very valuable.

There are some things wrong with the gold isotope. It does not always go where you want it. It does not always deliver its radiation where you want it delivered. There is an argument among the people who are using this isotope as to why it does not always produce exactly the effect that you want. The arguments are generated around two phases. There are two kinds of radiation coming out of the radioactive gold. One is the beta rays which have a very short range but very powerful ionization where they do penetrate and are absorbed in the body.

There is another type of radiation and that is the very long range gamma rays which spread out through the body but have a weaker ionization effect when they are absorbed in the body.

Well, we can study this by taking an isotope which has only a shortrange beta emission. It happens to be an isotope of yttrium. The isotope of yttrium has only a beta radiation and by using this isotype we can see if it has the same effect, if it can be used in the same way as gold, and if so, it would show us that the important factor, the important therapeutic agent we are using is the beta particle.

On the other hand, we have another isotope, an isotope of an element called lutecium, which has a beta particle but also a very low energy gamma ray. It is a combination. Both of these materials could be made into insoluble material and can be used, and so this is one of the things now that cannot be done very easily by schools outside of Oak Ridge. It demands very expensive and sometimes highly expensive preparation methods.

We feel, therefore, this is the type of study that we should take part in and concentrate our efforts on. Also, yttrium is associated very closely with the strontium isotope, which is very dangerous. This means that the use of this material as a new drug should be very carefully considered before it is used on humans, and again we think that it should only be done with those very specially trained because if a mistake is made and we are always likely to make mistakes the mistake cannot be disastrous. This is one phase of the new isotopes for internal use.

The other phase of the program is on the development of external use of isotopes. Radium has a number of gamma rays. Some are very high energy and some are very low. Now for about 50 years it has been used as a source of these rays on the outside of the body to shine a beam of radiation inside the body. In the same way that the X-ray machine is used to destroy cancer. Many of these isotopes have these gamma rays and at various energies. Some have lowenergy gamma rays and some have high-energy gamma rays.

In order to use an external beam we must have a very powerful source of gamma rays, and there are about 11 isotopes in the entire table which can be produced which have just the right radiation characteristic, so they could possibly be used for producing external beams of radiation.

The question comes up as to how to use these. We cannot copy the X-ray machine as it now exists. There may be a better way of doing it. The problem is exactly how to do this and what is the best way to apply this external beam of radiation. We did not think that we should make the decision, and so we got together a group of reputable representatives from 22 medical schools to join in an evaluation board to help us to decide how best we could apply these powerful external sources of gamma rays.

The program first developed about the problem which was mentioned by Dr. Warren in the testimony yesterday. It is very important that we make things available to many physicians. We can treat 1 or 2 but not 20 patients at 1 time. This is an insignificant contribution. What we do is no good unless many physicians can use it. And so we felt the first problem we should take is a very, very practical machine, something that could be used by many people. So we have designed, and there was shown to this teletherapy board just 2 weeks ago a small cobalt 60 therapy machine. This machine uses an isotope of cobalt which gives off a radiation which is equivalent to about a 30-million-volt X-ray machine. It is made up from cobalt, which is readily available to all of us. It is available to all hospitals that are qualified to use high-energy sources of radiation. And very important in the development of this machine, in working with the company that helped us develop it, we made the very strict stipulation that there was a cost to this machine which was very important. We said that the machine at its final development must be competitive with machines now available, the X-ray machines on the market, and so we have developed a small cobalt machine which will be priced somewhere close to the price of an X-ray machine. It has, however, some advantages over X-ray.

This is not the end, the theoretical end of the program. This is an adaptation, or a modification of what we really want in order to make something available today.

What we really want is to take the fullest dvantage of an isotope source of a powerful source of gamma rays. In every nuclear reactor that has been built and that will be built, in order to keep the nuclear reactor going, there has to be a fission of uranium, plutonium, or some other fissionable source. When this fission of uranium occurs there is produced certain fissionable products. One is cesium. This means that no matter what kind of a reactor is developed by the commission, wherever it is developed, they will be producing the cesium. Cesium has a gamma-ray energy, which is equivalent to something between a 1-million-volt X-ray machine and the 2-million-volt X-ray machine. It is a waste product. It is produced whether we like it or not. There is a large amount of it being produced. Here is a source of energy that can be put to use, and so we have developed a cesium teletherapy machine which has as its main feature a small housing which can be easily manipulated mechanically. It does not have to have large power lines coming into it to keep it ctivated. Cesium lasts a long time, and since cesium is a waste product eventually, it should be a very economical and practical source of radiation. Therefore we designed the cesium machines so there would be a completely free rotating machine.

The whole problem of developing this machine shows a very interesting relationship to the studies that have been going on all through the Commission.

Cesium was discovered as an isotope in 1945. In 1947 they were sure it had the energy that we now know it has. In 1950 we were sure it could be separated in large amounts and at the end of 1953 we will have for the first time approximately 1,000 to 2,000 curie source, which is a very large source of cesium. This has taken only about 5 to 8 years from the beginning of the knowledge of a new isotope until it will be used in a practical sense.

There are many other sources that still remain. We do not have to stay completely on this type of source. There are other fissions producing the cesium isotope, the strontium isotope, which also can be used for teletherapy machines, and eventually, as soon as this initial problem of the small and large teletherapy machines are through this teletherapy board of seven medical school, they will go into the problem of other types of fission production that can be used.

Dr. BUGHER. Thank you very much. Are there any questions?

(The following information on the application of atomic energy for medical purposes in Europe was later submitted by Dr. Bruce for the record :)

REPORT ON EUROPEAN TRIP, JULY 1953, BY MARSHALL BRUCER, M. D., CHAIRMAN,

THE MEDICAL DIVISION, OAK RIDGE INSTITUTE OF NUCLEAR STUDIES

I. PAPERS PRESENTED AT THE SEVENTH INTERNATIONAL CONGRESS OF RADIOLOGY AT

COPENHAGEN, JULY 1953

For an estimate of the probable direction of development of the use of radiation in medicine, it is instructive to review the choice of subject of a large segment of radiation workers attending the International Congress. This estimate is highly biased by the economics of attendance and by the exhibitionist tendencies of the participants, but it is still the best first impression we can get of what people are thinking about. Table 1 shows my breakdown of the listed papers.

TABLE 1.--The subject matter of 504 papers presented to the 7th International

Congress of Radiology at Copenhagen, July 1953 A. Diagnostic reports---

212

54 35 32 29

Clinical diagnostic studies with ordinary equipment.
Physics and techniques with ordinary equipment-
Tomographic studies and techniques.-
Special angiographic methods and equipment.--
Correlation studies with anatomy-pathology-physiology ---
Fluoroscopic amplification, microfocal point tubes and cinefluorog-

raphy
Contrast media, materials, methods, and equipment.
High-voltage diagnostic equipment and problems---

9 8

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Diagnostic studies_
Internally administered for therapy (1 131, p. 32, Ga. 72, etc.).
Semimechanical placement (Au 198, etc.)
Mechanically placed (seeds and needles)
Isotope production problems.---
Autoradiographic studies.--

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One major departure from the program was the sudden appearance of three delegates from the U. S. S. R. At least two were immediately given a place on the program. The one I heard gave a talk in Russian on the subject of tomography in the middle of our symposium on integral dose. From the translation I judge that he said nothing I have not heard previously from American radiologists. Another Russian gave a talk on the use of cobalt 60 in teletherapy. Dr. Hollaender of ORNL was present at the meeting when this talk was given but he reported nothing beyond the fact that the translation was difficult to understand and that the U. S. S. R. is apparently producing cobalt 60 in sufficient amounts to make a teletherapy machine.

In the field of diagnostic radiology, which I am in no sense competent to judge, there was an overwhelming emphasis on tomographic and angiographic studies. There seemed to be more emphasis on the use of high energies in diagnostic equipment and high energy techniques than is apparent in the table.

In the field of therapy there was the usual emphasis on cancer. In addition, however, there seems to be an evergrowing realization that the reporting of results is the backbone of the field and that it represents an unsolved problem of first magnitude. There is continuing agitation for a worldwide standardization of classification and reporting methods and techniques.

In the field of special therapeutic equipment, moving field therapy was the outstanding subject of discussion. Many individuals have pet techniques usually built around an individual piece of equipment which they push as an outstanding new development. There seems to be a slowly growing appreciation among a number of men that the problem of the moving field is an extensive one and has many ramifications worthy of investigation.

High energy accelerators of various kinds seem to have a popularity out of proportion to their immediate practicality. There were more papers on the subject than machines in use. It is apparent, however, that a number of European manufacturing houses are actively engaged in selling machines and, as was pointed out repeatedly, that the high energy accelerators can be purchased while isotope machines must be begged for.

In the use of isotopes there was little that has not already been reported. A few special problems are noted later in this report. Outstanding were the papers by officials of the governments producing isotopes. It is obvious throughout Europe that both England and Kjeller are making a bid for a worldwide isotope market. At every place I visited there was praise for the Harwell isotope service. The amount of service that they perform is truly remarkable. A separate paragraph appears in this report on the cyclotron sales from Holland.

In the field of radiation biology the outstanding discussions were not the numerous ones on radiation effects but rather the amount of effort and thought being put into the problems of chemical resistance and sensitization to radiation. Although the field is an old one, and some of the compounds being used are in the books as failures, the results obtained show ever increasing encouragement. J. S. Mitchell's preliminary report will be published shortly and will describe an experimental method which is worth careful study.

The problems of dosage and measurement were among the most important at the meeting. Some of these will be discussed separately in the following report. The papers on instruments, methods, and equipment were on the whole a rehash of subjects already out-of-date in America. A few outstanding exceptions to this are discussed separately.

Of the outstanding importance were the deliberations of the international commissions. These were reported only briefly at the closing ceremonies of the congress, and will shortly be published in full in standard journals.

Briefly:
1. The eighth congress will meet in Mexico City in 1956.

2. An International Society of Radiology will be organized with its first membership taken from the present national societies.

3. The definition of the “r” remains unchanged up to 3 mev. 4. A new unit, the “rad”, is defined as 100 ergs/gram. 5. A maximum permissible exposure standard was adopted for 96 isotopes. 6. A maximum permissible exposure for total body radiation was adopted.

7. New recommendations for handling isotopes and isotope bearing wastes were accepted.

II. ACTIVITIES CONCERNING TELETHERAPY UNITS At Southampton, Dr. Taylor, therapist, and Dr. Clarkson, physicist, have designed a cesium 137 machine that will use either 2 or 4 sources of cesium 137 of somewhat less than kilocurie size. These sources are placed on a large, ringshaped, double gimble that will completely surround the patient and that will allow most kinds of rotational therapy. By adding movements of the bed, any kind of moving therapy can be accomplished. The source shields are placed opposite each other so that the direct beam from one source, but not scatter, is always shielded by the opposite head. It is doubtful that the design of each

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