Development of Japanese Radiological Equipment in the Post-World War II
Period (25)

Sumio Makino (Advisor, JIRA)

I. X- ray cassette

Outline of the previous installment for the history of the development

"Radiology Japan No.59" was the first installment for the history of the development of radiology-related apparatus and accessories in the postwar period. First of all, I referred to the X-ray grid, which is indispensable for radiography. I described the origin and subsequent history of "MS grid", which was developed by Mitaya Manufacturing Co. Ltd. (abbreviated as Mitaya) whose president was the late Mr. Yasunobu Iida. Mr. Iida and all his employees made an assiduous effort, contributing to the development of the apparatus and progress of X-ray diagnosis.

History of the development of the X-ray cassette

This installment describes the history of development of X-ray film cassette, which receives X-ray images. Recent technical progress and development has brought about a convenient daylight system etc. and the so-called "cassetteless" mechanism, which uses raw film without a cassette. The progress of "IT technology" has changed the recording methods of medical images. Consequently, X-ray cassettes are less frequently used than when they were indispensable for all radiological procedures. But, the demand is still constantly active. Furthermore, the recent sophisticated purpose of radiography seems to require special functions in addition to the conventional simple radiography.

A remarkable change has occurred in the market, usage, and purpose of cassette. Addressing this change, Okamoto Manufacturing Co. Ltd. (abbreviated as Okamoto) manufactured the world-famous "Okamoto cassette". The history of this company represents that of JIRA. The brief history follows.

1. The founding of Okamoto

The business was started by Mr. Masaharu Okamoto, who is father of Mr. Tadaomi Okamoto, the present president.

In the early period of the Showa Era (1926-1989), though the exact year is not known, he started his business in Tokyo as a subcontractor of Shimadzu Corp.'s Science Division. He was dealing also with gifts to royal families.

Beginning of the manufacture of the cassette

As seen in the Japanese history of X-ray equipment and accessories, Japan had depended on imports until the early period of the Showa Era. In 1938, Okamoto was requested by the purchasing manager of Shimadzu to manufacture what was called a "cassette". In those days, the X-ray cassette was for military use. Shimadzu ordered 5000 cassettes. This motivated the subsequent manufacture of the cassette.

2. Okamoto during and after the war

In 1944 during the War, a military subcontractor named "Kaseidou Kouku" was located in Tachikawa. Under a governmental order during the War, this company requisitioned Okamoto, which was then located in Akabane, forcing Okamoto to interrupt the business of the cassette and Shimadzu subcontracted.

Resumption of cassette manufacture

Immediately after the war, the former president intended a leisurely life, spending what he saved until then. However, his plan collapsed, because rising inflation caused him to earn a living once more by resuming the cassette manufacture in 1949.

Handmade cassette --- Resumption of business through a typical cottage industry

A handmade cassette consisted of a board of Bakelite screwed to the outer frame of aluminum casting. The former president and his wife were engaged in the cottage industry, using a small set of tools such as a hammer, a file, a manual borer, and a tapping machine.The workplace was a remodeled bathroom (about 7 square meters) behind their house located at Takadanobaba.Even under these circumstances, they manufactured 20 pieces of 10"x12" cassettes and delivered them to Asia Roentgen Rays in April 1949 . This was the first sale in the postwar period. Then, the cassette market spread gradually to Chiyoda Roentgen Rays, Yayoi X-rays, Orion Denki, Seikosha, Nishimoto Sangyo, Tanaka Roentgen Rays and Fuji Roentgen rays.

Fig. 1 Cassette used in the early period of Showa Era (1945-1964)

3. The increasing demand for cassettes, especially lightweight cassettes, and the development of Okamoto

The cassette used in Japan in those days was compliant with the so-called Asian standard, and not with the IEC international standard.

After 1955, Japan's economy grew astonishingly. Until then, the so-called national disease, tuberculosis, was almost under control. The problem of stomach cancer came next. It was called the second national disease. Starting in 1965, the medical community advocated the necessity for X ray medical checkups for early stomach cancer. The mass screening examination used a fluorographic system mounted on a vehicle. On the other hand, improvement of examination efficiency was attempted by using direct radiography, which is a "remote-controlled X-ray system". The research of this system successfully developed into a large industrial sector.

Toshiba planned to develop a mass stomach screening system and respond to an increasing demand. The present president of Okamoto was asked to come to Tamagawa Works and was told as follows. "The future model of remote-controlled X-ray system will have several films (i.e. several cassettes) contained in the tabletop. The Japanese cassette is too heavy and it is not easy to use. We urgently need an aluminum cassette that is marketed by Philips, in the Netherlands. It is called a 'lightweight cassette'. A large demand is expected. Although it is a rush order, delivery within three months is requested."

When he was told this, he regarded this order as a big business chance. However, this order was beyond the technology of his company in those days.

He was in such shock that he could not get an idea. He went to a movie theater for two consecutive days, sitting at the very back of the second floor, and staying there all day long. After watching the first run of the movie, he devoted himself to medication. At last, he got an idea of mass production. In the spring of 1965 ,he manufactured a prototype, which was certified by Toshiba, and he started mass production. This became a big start. The cottage industry developed into a full-fledged industry of "mass orders and mass production". At last, a new factory was built in 1968.

However, the lightweight cassette of this stage needed some structural improvements. In 1969, a "PL (push-lightweight) type cassette" of one-touch structure was manufactured, leading to the subsequent development of business.

Fig. 2 A cassette for a remote- controlled diagnostic system (1965 - 1969)

4. Internationalization of Okamoto Manufacturing The second change of the domestic market

The manufacturing of lightweight cassettes expanded in Japan. Around 1972, we modified the design of the remote-controlled X-ray system for stomach mass screening. The new system used raw film directly and did not use any cassettes. It was the so-called "cassetteless system". As a result, the trend of the industry changed greatly.

Participation in an exhibition at the International Congress of Radiology in 1973, starting the overseas market

At this stage, Okamoto intended to export their products for the first time, and displayed their newly developed cassette at the 13th International Congress of Radiology (in Madrid) in 1973. The visitors to the exhibition responded favorably, resulting in the establishment of the sales subsidiary as the first step for marketing overseas. The products enjoyed a good reputation through Europe, and a trading firm was founded later.

5. Development of Okamoto as a manufacturer

The main product was the "newest lightweight cassette" featured with excellent performance. Its market share became as high as about 30% in the world. It was awarded "Good Design Prize from the Director-General of the Small and Medium Enterprise Agency" in October 1994. It was certified with the ISO 9002 (quality management system) standard in April 1998.

Fig. 3 Present PL-B type cassette, awarded Good Design Special Prize

II. Radiation protective materials

1. History of the development of postwar JIRA, the facts and my reflection

My running story covers the whole development of Japanese radiological equipment in the postwar period. In the meantime, "Radiology Japan No.59" was the first installment for the development of radiology-related apparatus and accessories. Since I was 23 years old at the end of war, I have been involved in the technical development of Toshiba radiological equipment, starting with radiation measurement apparatus immediately after the war and leading to MRI in recent years. I worked for one of the member companies and saw the progress of JIRA. It was housed in a wooden office initially and moved to a modern building later. Every year, we participated in the exhibition held at the time of Japan Radiology Congress. All these events are described in this series.

JIRA consists of a variety of member companies. A dozen or so companies are major enterprises engaged in domestic and international business. Others are the small and medium-sized enterprises that are peculiar to Japan. The latter specialize in the apparatus and accessories related to radiological equipment. The entrepreneurs and the family of these companies made a tremendous effort, and the employees were united firmly. Their achievement in the Japanese radiological equipment industry should be recorded as a part of JIRA history.

It is a matter of course that major companies do business in the international market, contributing to health throughout the world. However, it is necessary for the performance of such equipment to be complemented by related apparatus and accessories. Japanese companies in this field, irrespective of their size, must make an effort toward further progress. With this in mind, I am about to conclude the series with final chapters.

2. The history of Maeda & Co., Ltd. in the development of radiation protective materials

"Hagoromo-brand" protective clothing made by Maeda & Co., Ltd. (abbreviated as Maeda) is popular in all hospitals and clinics throughout Japan. The history of this company represents the history of a specialized enterprise. Details are as follows.

Beginning of Maeda

(1) In May 1928, Mr. Ichiro Maeda (father of the present President Mr. Koichi Maeda) founded Maeda at Komagome, Hongoku (now Honkomagome, Bunkyoku) Tokyo, starting the manufacture and sales of leather tools and mats for medical use. The present president was born in 1940.

(2) After that, the company was located near Tsumakoi Bunkyoku, and moved to Ogawamachi, Saitama Prefecture for evacuation from air raids. In 1944, Mr. I. Maeda closed his company and worked for a munition factory located at Higashimatsuyamashi, Saitama Prefecture.

(3) In February 1947, after the war, Maeda resumed business at the present location: 3-11-9, Hongo, Kinsukemachi, Bunkyoku.

(4) In January 1954, Maeda was reorganized with the capital of 300,000 yen, and Mr. K. Ueda was appointed as the first representative director.

Idea of protective clothing

Nihon Ika Kogyo, a single munition supplier of medical apparatus, was liquidated after the war. The two employees, Mr. Arai and his brother, established Chuwa Shoji, which manufactured and sold X-ray equipment and protective material. The business went on smoothly. At that time, the protective clothes were merely aprons made of thick, hard lead-containing rubber. They improved the product so that the whole body could be covered. "Whole-body protective clothing" was the starting point of Maeda's business for the specialized manufacture and sales of protective devices.

The designing of whole-body type clothing was made by Mr. K. Maeda's eldest sister, Sachiko. Although she was not familiar with protective clothes and protective sheets, she was good at sewing and developed three new protective clothes: type A (hospital gown), type B (sleeved apron), and type C (sleeveless apron). The lead equivalent was 0.07 mm, and the color was only white, implying white robes were used in hospitals in those days.

The start of the protective clothing business

After mutual negotiation, Maeda became a manufacturer and Chuwa became a seller. The Chuwa's Bunkyo Factory was licensed as a medical device manufacturer. This was the first step toward future progress. Coincidentally, a Japanese fishing boat was exposed to an atomic bomb test conducted in the Bikini Atoll in 1954, resulting in higher concerns about radiation among public. The type A protective clothes appeared in the market in a timely manner.

Episode (1) The origin of the brand name "Hagoromo"

Protective clothes are heavy because they contain lead. The president and employees looked for a good name that suggests lightweight. After repeated consultation, they selected unanimously "Hagoromo (robe of feathers)", an imaginary, celestial maiden's clothes. These days, younger people do not know Hagoromo. It is a pity that as good a naming as this is losing its original effect.

Episode (2) The quality control of lead-containing sheeting

In 1954 Mr. K. Maeda (the present president) was a second grader of junior high school. The 0.07 mmPb lead-containing sheet was at the early stage of manufacture, and it often contained many air bubbles because of the immature method of manufacture. He was asked by his father to locate air bubbles. He was told to stay at night under a makeshift tent made of the lead-containing sheet. He had to look for electric light leaking from the outside. He lifted the light spot from the inside, and his father marked the spot from the outside. The portion without such marked spots was used for manufacture of protective clothes. Looking back it was a very primitive technique of quality control in homemade products. However that was a sign of the times, as in the joke that everything was hand-made back then.

Protective clothing manufacturing was getting on track

In 1958, the present president entered Maeda. His first job was to find out how to remove the air bubbles. The thin sheet should have less bubbles, but it is fragile. So, if many thin sheets were laminated, the product would be strong and free from bubbles. The sheet maker reluctantly adopted this layman's idea. The success was an example of the proverb "The onlooker sees most of the game". The products were priced at 7,000 yen, 5,000 yen, and 3,000 yen for each type, because seven, five and three are lucky numbers in Japanese superstition.

In January 1969, Mr. K. Maeda became president. In November 1973, Maeda became a joint-stock company, and got dealership from Chuwa. Chuwa's president became the advisor. The company was renamed "Maeda Corp." in expectation of further growth of both manufacture and sales. In the meantime, the imports of overseas products increased, and new domestic companies joined the market, resulting in severe competition. To compete with foreign products having high Pb equivalent, a product must have a higher Pb equivalent, be lightweight and soft.

Maeda Corp. laminated the 0.1, 0.13, and 0.18 mmPb sheets into the 0.25, 0.35, and 0.50 mmPb products. In 1982, "Hagoromo Soflight series" was announced. This product was remarkably soft and lightweight. Furthermore, in 1986, "Hagoromo Dreamlight series" was announced with 30% reduction of weight. This resulted actually in 45% reduction of weight compared with initial products.

Improvement and development of the product continued steadily. At present, "Hagoromo Magicallight" has been added to the product line, which is lead-free protective sheeting. This is contrary to common sense that radiation protection needs lead". They supply monochrome clothes of blue, pink, green, orange, yellow, and grey color, as well as 12 kinds of clothes with multicolor patterns. Thus, they have a wide variety of products that can be provided only by a specialized supplier.

Establishment of company motto and management concept

In September 1995, Maeda Corp. completed the business infrastructure, sending its president to the JIRA Board of Directors and established the company motto and management concept to cope with greater social responsibility.

President message, company motto and management concept

The president said as follows:

My father founded this company in May 1928, starting with the manufacture of leather products for medical use. His motto was: "Be fair, righteous, cheerful, merry and fearless!" (Text partly omitted.) For the "Growth of Maeda Corp.", every employee must grow up with a clear understanding of the present business situation. For that purpose, I announce the company motto and management concept, upon which I stipulate the working regulations and other rules. Our company must satisfy all employees and our customers, thus contributing to the medical community.

It is worthwhile working for the company where:.

1. you are proud of your job,
2. you are aggressive in addressing any problems,
3. you are responsible for your job,
4. you are thankful for your job and customers, and
5. you are evaluated fairly in your job. Fairness is different from mere equality. Evaluation should be based on what you have achieved.

Let us try and develop through our work and make our efforts be reflected on our work. Yes, we can.

3. Summary

As described at the beginning of this article, 80% of JIRA member companies are "small-and-medium-sized-enterprises". They are mostly related to medical imaging devices and X-ray equipment. Many companies emerged after the war and some of them succeed to continue their business, entering the international market more or less, and occupying a majority of the market share. This achievement was due to specialization of products, production quality assurance and low prices, which are characteristic of small-and-medium-sized-enterprises.

"Hagoromo" brand products of Maeda Corp. are no exception. The president and all the employees follow the company motto faithfully for further progress of business. I conclude this article hoping that they continue their effort for the growth of this sector of Japanese industries.

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III. Fluorescent-screens and intensifying-screens

Sumio Makino (Advisor, JIRA) Keiji Shinomiya (Ex.Kasei Optonix,Ltd.) Toshio Yamamoto (Ex.Okamoto)

1. Back to the "history of discovery of X-rays"

The discovery of X-rays by Dr. Roentgen in 1895 is detailed in "Roentgen-rays retrospection" published by Shimadzu Corp as follows.

"In order to observe cathode rays, one piece of paper coated with cyanidation platinum barium was prepared. (This is called a fluorescent screen). (Text is partly omitted.) On November 8, 1895, Mr. Roentgen covered the Crookes tube in black paper, and began the experiment. The light from a crookes tube was not visible at all. But, the fluorescent screen placed near the Crookes tube brightened (sic).

The fluorescent material (fluorescent screen) played a leading role in discovery of Roentgen rays (X rays), and it is the subject of this article.

2. The origin and progress of fluorescence material research

Fluorescent materials have been familiar since a long time ago. Luminous paints (phosphor) existed already in the 10th century. Barium sulfide (BaS phosphor) was developed by alchemists in Bologna, Italy in the 17th century. Subsequently in 1886, ZnS phosphor was discovered in France. This lead further to the fluorescent screen being used in the discovery of X-rays in 1895 mentioned above.

As early as in 1896, i.e. one year after the discovery of X-rays by Roentgen, Shimadzu Corp. succeeded in the trial production of a cyanidation platinum barium fluorescent screen for the first time in Japan.

3. The history of the development of photosensitive-materials industry in the postwar period

This history is detailed on and after page 135 in volume 1 of "The History of Japanese Radiological Technology" (published by Japanese Society of Radiological Technology in 1989. For a comprehensive history, readers are advised to refer to this publication. This article describes mainly Dai Nippon Toryo (later Kasei Optonix Ltd.) and Toshiba Corp.

3-1 Dai Nippon Toryo (now Kasei Optonix Ltd.)

1) Manufacture of basic products immediately after the war

In 1936 at the Yokohama Factory, research of the luminous paint using a sulfide phosphor began. During the war, the luminous paint was used for an emergency light source in submarines or for radar screens. After the war, it was directed for peaceful use. Firstly, for medical use such as X ray fluorescent screens and for intensifying screens.

In the postwar period, well-equipped hospitals used foreign fluorescent screens and intensifying screens provided as an aid supply. In the meantime, research continued to manufacture national products that surpassed foreign products.

Immediately after the war, the power supply situation was inferior. Hospitals used only X-ray equipment with small X-ray output. Then, the savior was the HS intensifying screen, which was very sensitive at that time and usable for small X-ray output. Then, in contrast to the highly sensitive HS type, they announced also the FS type, which was featured with excellent sharpness of X-ray images obtained. Finally, they completed the MS type, in which the sensitivity and sharpness were compatible. The three types were called "Kyokko HS, FS, and MS" and were dominant as typical screens. By 1951, these products became popular as "intensifying screens, S series" and established a stable position in the market.

Especially, the FS type adopted the particulate phosphors and absorption layer support mechanism, thus preventing the optical diffusion in phosphor layers. It was so well received that "a new FS type screen was regarded indispensable" for being awarded at the X-ray image contests sponsored by X-ray filmmakers. The market share then reached 55%.

2) Development of application products

After the postwar unstable period, X-ray examination methods advanced, leading to special radiological techniques and special examinations. High-voltage became popular, simultaneous multitomography was developed, and axial transverse laminography was invented. These innovative techniques required the special intensifying screens, which were developed successively in 1960s, and are still in use at present.

3) Challenge to X-ray dose reduction and development of the second generation of intensifying screens

In 1958, the International Commission on Radiological Protection (ICRP) issued a recommendation. In 1959, Japan established the Ordinance on the Prevention of Ionizing Radiation Hazards (labor ministerial ordinance No. 11) based on ICRP recommendation, resulting in research on radiation dose reduction including the warning, controlled areas etc.

In order to reduce the radiation dose of patients who undertake X-ray examination in hospitals, the intensifying screens required higher sensitivity and performance. To meet the requirements, they studied the structure of the intensifying screen, improving performance drastically, and introducing "LT-II". For the L-series screen, the surface had larger phosphor particles to reduce the loss of light, while the deep base layer had smaller phosphor particles to reflect fluorescence. This was the "proximity reflective technology", which ensures sensitivity and improves sharpness at the same time. "LT-II" (1973) was able to ensure good image quality and to reduce radiation dose. This product and "LF-II" (1976) established the second generation of the intensifying screens.

4) Appearance of the rare-earth intensifying screen

In 1971, the short supply of silver worldwide raised its price sharply. In 1972, Mr. R.A.Buchanan (U.S. Lockheed) and others applied rare-earth phosphor to the intensifying screens and combined it with the "orthochromatic film", which was not conventionally used for direct radiography. Thus, silver was saved, while high sensitivity was attained.

In 1983, they developed the original green luminescence rare-earth intensifying screens, which had a two-layer structure of different phosphors, and was exported to the U.S. They also colored phosphor layers to increase sharpness and to decrease crossover, and developed green-sensitive screens. As a result, this screen improved the system characteristics remarkably. The percentage of use of ortho-system reached 60% in Japan and higher than that in the foreign industrialized countries.

5) Summary about Kasei Optonix Ltd.

The Kyokko-brand intensifying screen continued improvement. At present, the performance surpasses FS in terms of physical characteristics such as sharpness and granularity. For the past 30 years, the film/intensifying technology has reduced the X-ray dose to about one-third, while keeping the same image quality as before.
As mentioned above, the improvement of the intensifying screens including phosphors is a permanent research theme. The technology of fluorescent screens and intensifying screens is inherited as the signal-converting element for "flat panel display (FPD)”, which is the base of the present diagnostic imaging apparatus.

3-2 Toshiba Corp.

a) The company changed its name from Tokyo Electric Co., Ltd., to Tokyo Shibaura Electric Co., Ltd., and to Toshiba Corp. But, the development of fluorescent screens goes back to Tokyo Electric Co., Ltd.

In 1915, they manufactured platinum chloride barium (green fluorescent screen) experimentally, which was then called Giba fluorescent screen. Until around 1940, they continued the research and manufacture of Giba fluorescent screens and intensifying screens. In 1940, they changed the product name from "Giba so and so" to "Mazda so and so" because of the organization change. After 1940, they discontinued manufacture because of the outbreak of war.

b) Business development in the postwar period

In the postwar reconstruction period, "Dai Nippon Toryo" and "Shimadzu" started the manufacture of intensifying screens and fluorescent screens as early as in 1946, i.e. the year following the end of the war. Toshiba was behind them, resuming manufacture in 1948, but starting mass production only after moving the facility to "Sunamachi Works" in 1951. Around that time, Dai Nippon Toryo etc. had already preceded in making various kinds of products as follows.

Thus, the three companies mentioned above were able to supply their own various products by 1955.
The period covered so far was the first postwar period. Then, the second postwar period continued until 1965, during which they improved the quality of the abovementioned standard products, and extended their line of products to cope with the progress and diversification of radiography.

Conventionally, the X-ray tube voltage of about 80kV was used for chest radiography. In 1955, however, the high-voltage radiography became popular where about 140 KVp was used. They used the intensifying screens that complied with the high-voltage radiography. They decreased the patient dose and improved sharpness of images (by using a small focus). In 1956 and 57, they performed 3- or 5-layer (later, 11-layer) simultaneous multitomography by using multitomographic intensifying screens.

In 1956, the national product of image intensifier was developed (by Toshiba and Shimadzu) for the first time. The materials of the X ray input fluorescent screen changed from ZnSiAg to ZnCdSiAg, and Gd2O2SiTb. In 1974, they invented the CsI:Na vapor deposition columnar-crystal fluorescence screen having the epoch-making brightness and resolution, which is still in use now.

For the gastroenteric X-ray examination, the cassetteless system was introduced around 1969. A pair of intensifying screens must handle many films continuously. They changed the base of intensifying screens from baryta paper to plastics. They increased the strength of the protective film of fluorescent surface, durability, and elasticity.

c) Appearance of "rare-earth intensifying screens”

In 1974, the "rare-earth intensifying screens Gd2O2SiTb (GdY) 2O2SiTb" with higher sensitivity appeared and accelerated the modernization of products.

Toshiba started research on X-ray photosensitive materials in 1915, and has continued research and production for more than 90 years. The product is inconspicuous, but it is a supporting player in displaying the result of X-ray examination. The incessant research has brought about the present level of sensitivity and sharpness.

4. Summary

The X-ray examination started soon after the discovery of X-rays in 1895. Afterward, researchers continued their efforts toward the goals of increasing the accuracy and sharpness of X-ray images while reducing the X-ray dose. Even today, they have not yet reached the goals. Their research will continue forever. Toshiba will also continue research and extend the history.

On the other hand, X-ray examination techniques and exposure protocols will change, resulting in the innovation of X-ray equipment. Accordingly, the accompanying research on fluorescent materials will continue.