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History of Dosimetry in Radiology and early Radiotherapy
R. Van Loon and R. Van Tiggelen Click here to see our objects about the history of radioprotection This contribution is a pseudo- or para-scientific contribution: we do not present any work in progress or results of research, but rather outline the history of the discovery of X-rays and the application to radiotherapy, even if frequently the first approach was not straightforward and scientific but the result of an unexpected stroke of luck. We briefly sketch the knowledge about cancer in the XIX century, the discovery of X-rays at the end of that century, some very early applications to therapy and the attempts to quantify in energy and dose these new rays. Some of the principles we still use, go back to the end of XIX century. Cancer and its treatment in the XIXth century. Cancer was known since ancient times, and the name “cancer” of this terrific disease comes from Greek language, meaning a crab, and explained by Paré A. (1509-1590) in the XIV Century as follows: “Cette tumeur a pris le nom de chancre, ou crabe, parce qu’elle lui ressemble beaucoup... Cet animal, quand il est attaché de ses pieds contre quelque chose, adhère à elle si fort qu’à peine on le peut arracher, principalement de ses deux pieds de devant qui sont en manière de pincettes” In the middle of the XIX century, cancer patients were still considered incurable chronic patients, and taken into care by private and mostly religious organisations. Some progress in treatment was made by surgery, once Pasteur’s (1822-1895) work suggested rules of asepsis in surgery but success was limited to cancers discovered in an early stage. Since surgery treated the cancer by local treatment, due to a lack of knowledge of the metastatic process or on the cellular theory: observation of tissues using a microscope (discovered in the XVIIth century) lead to development of “histology”, name proposed by Heusinger C. F. (1792-1863) in 1822. Virchow R. (1821-1902), another German scientist, will lay down the basis of the cellular theory summarised in the “omnis cellula a cellula”, each cell originates from an other cell. We are in the middle of the XIXth century. Three weeks after Röntgen’s public demonstration, on Jan 29th 1896 Grubbé E.H. (1875-1960), a chemist, physicist, and physician duplicated Röntgen's experiments and, with physicians and friends, tested the new "rays" on patients. He was one of the first physicians to utilize the "Röntgen's ray" in the treatment of breast cancer. The irradiation scheme was eighteen daily 1-hour exposures. The first patient, with advanced cancer of the breast was relieved but she died shortly afterward from metastases. Treatment of deep seated tumour and using only low energy X-rays however obtained only a temporary regression, and we will see mainly dermatologists using in the beginning this kind of therapy, e.g. for esthetical depilation or skin infection. The discovery of X-rays helped to fight in a more efficient way cancer, almost immediately after Röntgen’s discovery: already in Lyon by Despeignes V. (1866-1937) in July 1896 a first attempt was made to treat with X-rays a cancer of the stomach. At the end of 1896 Freund L. (1868-1943) showed the first successful application of X-ray therapy: a five-year-old girl, suffering from congenital hypertrichose, was cured by X-rays. This talented dermatologist will undertake a research on the quantitative and qualitative factors of treatments, and propose the fractionation of the applied dose, just one year after Röntgen’s discovery. The first really successful treatment by X-rays of a proven carcinoma, was obtained by Sjogan in 1899 in a man with advanced epithelioma of the cheek. Since the discovery of Becquerel A. (1852-1908) and the work of Marie (1867-1934) and Pierre Curie (1859-1906), cancers were also treated by radium therapy, and a first successful treatment was given in 1903 by Goldberg SW (1880-?) and London ES who treated facial basal-cell carcinoma in two patients. The two types of therapy –X-ray and radioactivity- developed separately for many years in separate departments, and needed urgently dosimetric methods. X-Rays and...N-Rays End 1895 Röntgen W.C. (1845-1923) contemplated a fogged photographic plate that his laboratory assistant has just developed by error. On the photograph he saw the silhouette of small limps out of paperboard containing a metal part. These objects were placed in the drawer of his office. He is extremely intrigued. So, while trying out the day before a cathode ray tube, mysterious rays crossed the office, and exposed the photographic plate! Consequently a long process starts where reflection and intuition will lead it to its discovery. Initially, he observes the flutter of fluorescent substances located at some distance of the tube, when under operation. Obviously, there is a radiation escaping from the tube. Interposed between the apparatus and the screen, a large book lets pass these mysterious rays. Röntgen is convinced: these rays he investigates, and which cross matter without disappearing, can’t be cathode rays! But still stranger, these rays are stopped by the bones of the hand! Röntgen already made a first attempt on energy determination: he patiently builds a small metal snail shaped staircase. After a long exposure, and by examining the photographic plate, he notes that the absorption of these x-rays increases with the thickness of metal. More on the story of X-ray can be found on display in the Belgian Museum of Radiology and the DVD. Röntgen received the Nobel Prize for physics in 1901, Becquerel and Pierre and Marie Curie in 1903. It was so easy to get a Nobel Prize with “mysterious rays” thought an other French scientist Blondot R. (1849-1930).. He was Professor of Chemistry at the Nancy University, and introduced to the Academy of Sciences his discovery: N-rays, with a capital N, to honour his town of Nancy. A note was send to the Academy on March 23, 1903 with the message that these rays were not ordinary X-rays but a new kind of light (“une nouvelle espèce de lumière”) crossing aluminium, wood, paper,...N-rays can be found in many places, the Sun is one source. Stones exposed to the sunlight will receive and in turn emit N-rays (“Des cailloux ramassés vers 4 heures de l’après-midi dans une cour ou ils avaient reçu des radiations solaires deviennent à leur tour de formidables émetteurs”). And of course, these N-rays have an influence on vegetal and animal structures… Blondot will receive a Prize of 50.000 Francs from the Academy in 1904. The "discovery" excited international interest and many physicists worked to replicate the effects. Following his failure to do so, US physicist Wood R.W. (1868-1955) was prevailed upon to travel to France to investigate further. He secretly removed an essential prism from the experimental apparatus, yet the experimenters still said that they observed N rays. He secretly replaced a piece of aluminium that was supposed to be giving off N rays with a piece of wood, yet the N rays were still "observed". His investigations, published in the September 29, 1904 edition of Nature, showed that these were a purely subjective phenomenon, with the scientists involved having recorded data that matched their expectations. By 1905 no one outside Nancy believed in N rays. Early observations of effects of X-rays. Röntgen discovered X-rays on the 8th of November 1895 and within a few months X-ray dermatitis of the hands was observed by Grubbé and in the UK Drury H.C. published a paper also on dermatitis. The first known recommendation on protection was probably given by Fuchs W. (1865-1907): - make the exposure as short as possible -do not stand within 12 inches of the X-ray tube -coat the skin with Vaseline and leave an extra layer on the area most exposed. In March 1896, an accidental radiation depilation was observed and reported by Vanderbilt Professor of Physics Daniel J. (1861-1950): In February of 1896, the physics professor at Vanderbilt University persuaded the dean of the medical school to sit for an experimental radiograph of the skull . Three weeks later the dean's hair fell out, a result treated with some laughing by those recording the event. By late 1896, similar reports were less humorous. Among the reported problems associated with X-rays were redness, numbness, depilation, infection, desquamation, and severe pain. Numerous possible causes were investigated: ozone generated by static machines, excessive heat and moisture, over-exposure to electricity, and "X-ray allergy." In retrospect the reluctance to blame the "New Rays" for these unusual symptoms may seem puzzling. But there was no historical precedent on which to base a rational fear of the rays, no reason to assume their effect could be any more or less damaging than that of electricity or light. Many papers were published on radiation damage during the following decades, but we have to wait till the International Congress of Radiology in 1925 to consider establishing protection standards. The Stockholm meeting of the ICR in 1928 will give birth to the ICRP. The human detector of X-rays. While generally considered invisible to the human eye – and also declared as such by Röntgen himself: "The retina of the eye is insensitive to our rays; the eye brought close to the discharge apparatus registers nothing"- however in special circumstances, X-rays can be seen: An effect was first reported by Brandes G.S.B. in experimentations a short time after Röntgen’s 1895 paper; after dark adaptation and placing his eye close to an X-ray tube, he sees a faint "blue-grey" glow which seemed to originate within the eye itself… . .After reading Brandes, Röntgen reviewed his record books and found he in fact, also saw the effect, but only with ONE powerful tube. Röntgen then in his third paper on X-rays reported on “ a feeble sensation of light that spread over the whole field of vision” . The fact that X-rays are actually faintly visible to the dark-adapted naked eye has largely been forgotten today is probably due to the lack of desire to repeat what we would now see as a recklessly dangerous and harmful experiment with ionizing radiation. While the mechanism is not completely understood, we nowadays assume that these effects known as « radiation phosphenes », are due to the direct action of the X-rays on the visual purple of the retina. Understanding penetration: measurement of the QUALITY of the radiation. For a relatively long time radiology and radiotherapy were carried out with the X-rays as they came out of the tube: to compare equipment and thus treatment, minute details of the generator, tube, distance from the tube and time of exposure were given. But even than, effects were often quite different from one location to another due to quality and quantity of radiation. A textbook of that period recommended for setting up the equipment do routine testing of the penetration capability of the beam by the fluoroscopy of the radiologist’s own hand or the hand of his assistant, perhaps the physicist?. Several methods were invented to assess the penetration and thus what even now we call the quality of the radiation: indirectly by absorption measurements or by measurement of the potential applied to the tube and directly, by characterization of the spectrum. Röntgen did already in 1895 some experiments on absorption. He wrote, “These results lead to the conclusion that the transparency of different substances, assumed to be of equal thickness, is essentially conditioned upon their density” and “the density is not the only cause acting”… The idea and names of Hard” and “Soft” to be used for the penetrative quality of the X-rays was first used by Kienbock R. (1871-1954) in 1900. Also the effect of the focus-to-skin distance on the penetration in tissue was recognised soon. But results were far from what is obtained now: and Knox R. (1867-1828) stated in 1915 that “up to quite recently it has been held that X-rays penetrate successfully to a depth of 1 cm or less, and anything had been left alone”. Further also that “with hard tubes, effects can be produced up to 10cm” From the beginning methods and instruments became available for the measurement of the quality of the X-ray beam, called penetrameters or quality meters. The “radiochromometer” by Benoist L. (1856-?) was possibly inspired by Röntgen’s snail-like object mentioned earlier. Radiotherapy was starting cautious incursions into the treatment of internal tumours. This made new demands on technology. Gradually empiricism gave in to rational methods. Benoist L. a French physics teacher, invented a device that permitted the appraisal of the beam’s penetrability for comparison with others. Benoist described the “skiameter” in 1902: it was a thin disk of silver, 16mm in diameter, 0.11 mm thick, and surrounded by 12 Al disks of increasing thickness. When the penetrameter was put in front of a fluorescent screen (or a photographic plate) an equal colour or density was observed between the central disk and one of the sectors: this gave the “beam quality” in Benoist degrees. For instance, a hard beam was 7 or 8° Benoist, 7 or 8 mm Aluminium thickness. The basic principle was the contrast between the selective and the non-selective absorption of Aluminium and Silver. The radiochromatic viewer, “pénétratomètre”, of Belot J. (1876-1953) and the “kryptoradiometer” according to Wehnelt A. (1871-1944) is built on the same principle. A very simple way to evaluate the voltage applied to the tube was the “spintermeter”, so called by Dr Béclère A. (1856-1939) from" hôpital Tenon" in Paris. Two electrodes, one fixed, one mobile, are placed in parallel to the tube. When the electrodes are approaching, the distance when sparking occurs was called the “equivalent spark” [“l’étincelle équivalente”]. This wording was used by almost all authors in the first decades of the 20th century. Of course, the accuracy was not extraordinary: the distance depends on the shape of the electrodes, small spheres, point-shaped electrodes, flat disks. A. d’Arsonval (1851-1940) was a French Physicist and Medical Doctor. His name is of course linked with the galvanometer with mobile coil, but he contributed also by a quality measurement of the beam based on the measurement of the PRIMARY lower voltage, instead of the tube voltage. However, the straightforward application of the ratio n1/n2 lead to errors, since ohmic magnetic losses were neglected: this method required a calibration by the spinter method e.g., but was safer than the latter. Evaluation of the QUANTITY of radiation: dose. Evaluation of the penetration capability was solved, but the second problem remained: how measures the quantity of radiation delivered by a given exposure? Guido Holtzknecht G. (1872-1931), of Vienna, at the Second International Congress of Medical Electrology, in Berne in 1902 gave a solution to the problem of the quantity of radiations delivered by a given exposure: he presented the “Chromoradiometer” Based on the photochemical effect and the consequent changes in colour of a mixture of sodium carbonate and potassium chloride, Holtzknecht evaluated the dose that would produce a mild skin reaction and designated it as 3H. Unfortunately the colour change could be affected by temperature and humidity, and Holtzknecht did not reveal the chemicals he used in his device: result was that the device was not really popular. Dermatologists frequently used the dosimeter developed by Sabouraud R. (1864-1938) and Noiré H. (1878-1937 or the one of Bordier L. (1863-1949) . Both used small disks or “pastilles” of barium platinocyanide which would change colour from green to a dark yellow-orange as a result of the exposure to x-rays. Bordier’s pastilles, placed directly on the patient’s body, used the following standard scale of four colours: tint I, a pale yellowish green, produced depilation after 20 days; tint II, a sulphur-yellow shade, produced erythema (i.e., a reddening of the skin); tint III, the colour of gamboge, produced dermatitis, and; tint IV, ulceration and necrosis (tissue death). An exposure equivalent to Tint IV, “should never be applied to the skin”. In 1905 already, the German Kienböck already proposed his “Kienböck strips”, small strips of film to be exposed on the patient's skin. The density of the film was compared to an arbitrary standard scale from 1 to 10. All these quantitative determinations were of course dependent on the quality of the beam, and conversion from one unit to an other was approximate: general agreement was that Sabouraud-Noiré’s tint B was more less equivalent to five Holtzknecht and ten Kienböck. These dose determinations remained in use till about 1930, when the condenser chamber could make energy-independent measurements. The blackening of film was also proposed as a STANDARD for radiation protection in 1902 by Rollins W. (1852-1929) in a paper called “Notes on X-ray light: vacuum tube burns” and later effectively became a “Radium” unit, introduced by Tousey S. (1864-1937) as a “Tousey unit of power”. Wagner R. (1869-1908), a tube manufacturer, used film as personnel dosimeter to know if he was exposed when repairing or inspecting malfunctioning units: “The thing is to know whether you have been exposed during the day…so I carry a photographic plate in my pocket, and in the evening… I develop this film to see whether I have been exposed”. Wagner died from radiation induced cancer of the liver . Already in 1900 by Rutherford E. (1871-1937) mentioned that the intensity of the beam could be measured by the intensity of the fluorescence of a screen. In the fluorometer of Guilleminot H. (1869-1922), a standard illumination was given by a luminescent paper strip, giving a almost constant output during one year. A luminescence of screen in platino-cyanide has to be made equal to that of the standard by changing distance to the source tube. A small ribbon meter was attached to the side of the tube. The unit was the M: Let us quote him: “L’unité M d’intensité est l’intensité du champ de rayonnement fourni par un tube marchant à un régime moyen et å un degré de dureté moyenne (no 6 de benoist) lorsque ce rayonnement , agissant normalement sur la solution d’iodoforme à 2% de Freund et Brdiwer et suivant un centimètre de surface et un centimètre de profondeur, libère en une seconde 10-8 grammes d’iode” “ Selenium cell measurements were proposed by Fürstenau R. (1887- ?) and were based on the change in electrical resistance of a layer of selenium when exposed to X-rays. The system was in fact a dose rate meter calibrated in F/minute, but very dependent on beam quality. We are all familiar now with the ionisation chamber, but it took a long time to have this multipurpose instrument with a rather good accuracy and precision. In February 1896 it was reported in “The Electrician” that an electrically charged leaf electroscope had been discharged by exposure to X-rays. This is probably the first measurement of ionisation effect. In the same year Thomson J.J. (1856-1940) showed already that air, normally an isolator, was made conductive by X-rays. He and Rutherford hypothesized that this occurred by stripping off small charged particles from the air molecules. Medical physicists are familiar with the W value, mean energy expended in a gas per ion pair formed: this concept was introduced in 1900 by Rutherford when he tried to improve Dorn’s method of calorimetry to measure X-ray energy. Indeed, in 1897 Dorn F. (1848-1916) attempted to measure the energy emitted from an X-ray tube: he exposed a metal plate inside a vessel to the beam, and measured the increase of pressure of the gas in the vessel! “Nil novi sub sole” . Villard P. (1860-1934) in 1908 and Szilard L. (1898-1964) in 1914 set down detailed requirements for a practical instrument. Indeed, ionisation was to become the method of choice for precision measurements and standards. Electrometers and ionisation chambers became the preferred instrument. Krönig B. (1863-1917) and Friedrich W. (1883-1968) in 1918 in Freiburg motivated their use of electrometer of Wulf T. (1868-1946) as follows: “As it was necessary for our biological experiments to measure the intensity at each location within the irradiated medium, we had to design the apparatus is a way that allows us to insert the ionisation chamber like a probe into the medium. The method of measurement was the discharge of an electrometer combined with a capacitor. We used the well-known two-fibre electrometer of Wulf. The amount of charge can be determined by the spreading of two conducting quartz-fibers under a microscope” Ionization chambers were further developed, a variety of models appeared, but in 1912 Makower W (1879-?) and Geiger H. (1882-1945) reduced them to the two basic will still know today: the cylindrical chamber, with a rod electrode along the central axis, and the flat chamber consisting of two parallel conductive plates. Dr Solomon I. (1880- ?), author of a “Précis de Radiothérapie” introduced “Solomon” units, based on an electrometer. The electrometer was charged by turning a small handle. The ionisation chamber was on the extremity of a rigid section of cable,then linked by a flexible cable - that could be shielded- to the instrument. The chamber was of the graphite type central electrode and wall. At the end of the twenties, we come close to equipment we are familiar with. The Victoreen Company of Cleveland Ohio introduced in the 30’s the Model 70 condenser "R meter" charger-reader. The Model 70 was based on a design of 1928 by Glasser and Seitz and commercialized by Victoreen. It proved to be very popular due to its rugged nature and flat energy response; some examples have been in use for nearly 50 years. The Model 70 is used in conjunction with air equivalent condenser chambers. Its primary purpose was to measure exposure rates associated with diagnostic and therapeutic x-ray facilities (nevertheless, it was often adapted for gamma ray measurement). Detachable condenser chambers were charged by the unit prior to use. After charging, the chambers were placed in x-ray or gamma ray fields (often for 1 minute) where the ionization created by the radiation would reduce the charge. When the chamber was reconnected to the Model 70, the exposure (in Röntgens) could be read from an illuminated scale seen through the eyepiece. The origin of the Survey meter, we all know and are familiar with, can probably be traced back to 1928. It was during 1928, his first year at the NBS, that Taylor L. (1902-2004) was calibrating clinical radiation meters in an x-ray beam. At one moment he forgot to replace a two foot by two foot lead panel that was in his direct line of sight of the 200 kV water-cooled tube. He had completed several minutes of high intensity measurements. He felt that it was probably best to prevent the recurrence of such an event. His solution was to construct a battery operated instrument which he could carry with him to measure exposure rates. The device employed a string electrometer that was coupled to one of three interchangeable thin-walled aluminium chambers. If not the first, it was certainly a very early portable survey instrument. Taylor recently died at the age of 102, proving that work with radiation does not necessarily shorten a life. Many others scientist contributed to dosimetry and radiation quality determination. The story of the units, from “Treshold Erythema Dose”: to Gray is worth a separate presentation Conclusion With this contribution we hope to have illustrated that, although very important technological progress has been made, from the beginning of radiology and radiotherapy many of the basic ideas and principles were already known and used one century ago. The ultra-fast development of the use of X-rays was also possible by the fact that no patent was taken by Röntgen on his discovery. The advancement of science and technology nowadays is handicapped by the preference given to economical and financial development for happy few. Finally, let us recall year by year from 1895 on some important developments for dosimetry in the early years: 1895-1896: Discovery of X-rays and radioactivity; use of electroscopes, electrometers and biological effects such as erythema, epilation, necrosis 1897 Attempt of calorimetry by Dorn 1900 Kienböck introduces terms Hard and Soft X-rays 1900 Concept of W, energy to produce ion-pair 1902 Chromoradiometer of Holtzknecht 1902 Penetrameter of Benoist 1904 Pastille radiometer of Sabouraud-Noire 1905 Quantimeterof Kienbock 1906 Chromoradiometer of Bordier 1908 Villard proposes the “free air” ionization as dosimetric method 1910 Improved pastille radiometer of Holtzknecht, in use till 1930 1912 Bragg theory and Half Value Layer concept 1915 Selenium dose rate meter of Fürstenau 1927 Solomon’s ionometer 1928 The Survey meter 1930 Victoreen Hodges P C The Life and Times of Emile H. Grubbe. Chicage. University of Chicago Press., 1964. We recommend the DVD movie “Röntgen Rediscovered”, produced by the Belgian Museum of Radiology . Röntgen W C. Uber eine neue Art von Strahlen, Sitzungberichte d. Physikalisch-Medizinischen Gesellschaft zu Wurzburg 9:132; 1895. Grubbé E H. Priority in the therapeutic use of X-rays. Radiology:156; 1933. Drury H C . Dermatitis caused by Röntgen X-rays. Br. J. Med 2:1377; 1896. Fuchs W. Simple recommendations on how to avoid radiation harm. Western Electrician 12; 1896. Daniel J. Depilatory action of X-rays. Med Record 1896; 49, 595. Brandes G.S. Preus Akad Wis 1: 547;1896. Unfortunately all of Röntgen’s notebooks were burned after his death! Röntgen W. Further observations on the properties of the x-rays. In:Otto Glaser, Math u Naturw Mitt a d Sitzberger Preuss Akad Wiss, Physik-Math; Kl 392;1897. Röntgen was colour blind. He never commented on the colours of the fluorescence he observed. Steidley et al. Observations of visual sensations produced by cerenkov radiation from high-energy electrons. Int J. Radiat.Oncol Biol Phys 17: 685;1989. Benoist L.Définition expérimentale de divers types de rayons X par le radiochromomètre. CRAS Paris, 134:225; 1902. Holtzknecht G. Das Chromoradiometer. Forthsch a d Geb d Röntgenstrah 1902; 4. 1-49. Sabouraud R, Noiré H. Traitement des teignes tondantes par les rayons X à l’école Lailler. Presse Med 12: 825; 1904. Bordier L. Radiometric methods. Arch Rontgen Ray 11:4-13; 1906. Brecher R, Brecher E. The rays – a history of radiology in the US and Canada. Baltimore: Williams and Wilkins Co; 1969. Fürstenau R. Ueber die Verwendbarkeit des Selens zu Röntgenstrahlenergiemessungen, Physikalische Zetung: 16: 276; 1915. ThomsonJ J, Rutherford E. On the passage of electricity through gases exposed to Röntgen rays. Phil Mag ser5: 392; 1896. Rutherford E., McLung R K. Energy of Röntgen and Becquerel rays, and the energy to produce an ion in gases. Phil Trans Roy Soc sera 196:25;1900. Dorn F. Heating effects of Röntgen rays. Ann Phys Chem 63: 160; 1897. Solomon. Ecclesiaste, I,10. Villard P. The radiosclerometer. Archives d’électricité médicale, Bordeaux, 14: 692; 1908. Szilard B. Absolute measurements of röntgen and gamma rays in biology. Makower W, Geiger H. Practical radioactivity measurements. New York: Longman, Green and Co; 1912. Solomon I. Précis de radiothérapie profonde. Masson, Paris 1926. An overview can be found in: “A Century of X-rays and Radioactivity in Medicine”, Mould R.F., Institute of Physics Publishing, Bristol; 1993. |