When I first arrived on the scene in the 3M Medical Products Group after 6 years in the 3M Central Research Group, I was introduced to the 3M Intensimatic Cassette. As mentioned in the article on Cassettes/Films, the film cassette was extremely important in the production of a readable X-ray film. If the film cassette was not constructed right or had been damaged, the film/screen "contact" could affect the image quality. This resulted in a product where you would see sharp areas, and virtually unreadable areas on the film. 3M had done some research into this problem and came up with a "vacuum" cassette. It consisted of a large cassette "platform" which would take a 14x17 inch (35x43CM) film in either vertical or horizontal direction (portrait or landscape), and all smaller size films. The outer area of the platform had a rubber gasket which circled (unbroken) around the area containing the film. The cover was constructed of a flexible plastic. A pair of Intensifying Screens were placed inside the unit so that one screen was on the platform and the other was glued or taped to the cover. The cover when resting on the gasket, could be vacuumed down over the film, which was sandwiched between the intensifying screens. A vacuum port was built into the rear of the platform. When an external vacuum pump was actuated, the screens were pulled into very strong contact with the film. This film/screen contact offered the sharpest images possible with the existing film/screen system.
I was assigned to this project to try to improve the system operation so that use in the Hospital would offer maximum efficiency and reliability. One of the things that was happening, was that the vacuum at 21 inches of mercury was pulling down so hard that the film edge was damaging the phosphor on the intensifying screens. It would leave a line on the screen that in later radiographs with different size films, would show up on the image as a non-exposed line. I found that I could reduce the vacuum to around 8 to 10 inches of mercury and still maintain excellent contact. I also changed the hinge construction which connected the cover to the platform base. This offered better alignment of the cover in relation to the base. Immediate vacuum could not always be obtained if the cover happened to be slightly warped or out of place. This required the X-ray Technician to stop and smooth out the cover to ensure contact with the gasket. I solved this be attaching a special latch arrangement at the front of the cover, which required the technician to sort of stretch the cover while latching it to the base. This solved the intermittent vacuum problem.
This device turned out to be very popular in the field because the X-ray department could always be guaranteed of getting the sharpest images possible. We made many modifications to the original units which improved the operation of the overall system. The Intensimatic Cassette was used for Chest X-rays and it could also be used inside the X-ray table. Some units may still be operational although I think that Government regulations which outmoded the operation of this unit make it almost illegal to use the system. Because too many technicians were lax in keeping the radiation beam from the X-ray tube "Collimator" with in the bounds of the X-ray cassette, Government regulations were enacted which required an automatic system to be implemented, which would mechanically cause the beam to be collimated to the size of the cassette being used for the study. Because the 3M Intensimatic system handled all sizes of films in the one cassette, it was virtually impossible to develop a system that would automatically collimate to the size of film contained in the unit. We did try and we did develop a system that detected the different size films, but it was too complicated and the project was abandoned. That was the demise of the 3M Intensimatic Cassette!
THE 3M LASER IMAGER/FILM PROCESSOR DOCKING UNIT:
When I worked on the documents which helped with the design of the 3M Medical Laser Imager, I decided that in order to speed up the developing process, it would be advantageous to hook an X-ray Film Processor directly onto the Laser Imager. At that time 3M had a processor designed (3M Italy) and used in Europe. It had not been introduced into the U.S. market at that time so I chose the Kodak M6 processor as the unit that should be attached to the Laser Imager. The M6 was probably the most popular processor on the market at that time, and I felt if we were going to use a system in the field, it would be wise to use a processor that almost every hospital in the country already used.
The concept for a unit called a "Docking Unit" (DU), was my idea. It was nothing new in the medical business to attach a film processor to some device such as one built by Picker X-ray, which was an automated chest filmer. The "Chest Filmer" was nothing more than a unit that automatically advanced film from a supply magazine into the exposure area, made the exposure on external command, and than transported the film to an attached film processor. I felt we needed a name which at the time would help people identify our Laser/DU as "Space Age" stuff. This was the age when "Apollo/Soyuz" was on every one's mind, so it was appropriate, and thus the name Docking Unit.
I drew a conceptual "box" that showed what should be included in the DU. All AC or DC power had to be brought from the Laser Imager so that adapting the system to other film processors would not present any problems in future applications. It would require film travel actuated switches which would keep the Laser Imager and the Film Processor informed as to the position of the film while in the Docking Unit. One of the things that "Experience" told me we should have, was an external light tight blower fan which would keep the DU pressurized, to provide an "air" barrier between the Imager and the Processor. This was really necessary because of the potential for the Laser Imager to become corroded from the Developer and Fixer fumes generated by the Film Processor. My boss at that time was a PHD Chemist and should have understood this concept, but overruled me and said that the Blower operation would cause vibration which would affect the film print quality. How wrong he was! The Laser Imager already had 3 fans on its body for cooling electronics. He could not explain why they didn't cause vibration. Later corrosion problems in the 3M Laser Imager, in the field proved that I was right. To this day I don't think 3M has added a fan to prevent this problem!
One of the best compliments I had, was when I was asked to go to the G.E. Company near Milwaukee, Wisconsin to review a Docking Unit built by a Company in Japan. They (the Japanese) wanted the unit to be approved by 3M to avoid any Warranty problems. The Docking Unit was beautiful! It was built from stainless steel and had solid state control systems built into the body of the unit which told the Laser Imager and the Processor (also theirs) where the film was. It also had something else built into the body which surprised and delighted me. They had built in an external blower which prevented any exchange of air between the units. This was exactly what I wanted on our D.U. and couldn't get. I complimented them on the design and especially for including the blower.
They said "Well we just copied your document on how to build a Docking Unit". I was surprised because my document was supposed to have been "company confidential", but they had some how or another got a copy of it. I suspect it was one of our "great" marketing people that gave it to them! One of the Japanese guys said, " I always wanted to meet the man who wrote up that document". What a compliment! You will now find thousands of the 3M D.U.'s in operation around the World, and I am sure that there are more than a few of the Japanese models out there also.
In about 1985 or 1986, 3M began negotiations with the G.E. Company to develop a contract to sell the 3M Medical Laser Imager. We had hundreds of the Imagers in Hospitals by that time. We knew that the Imager worked exceptionally well on the G.E. CAT scanner systems. There was one problem that existed, CAT scanners developed by most companies used two operating consoles in their systems. One console was called the "Operators" console and the other was a "Doctor's or Physician's" console. In other words each operating system had 2 consoles that could be operated independently or in conjunction with each other. Each console could use information gathered on a central memory unit that had been supplied by the other console. This was designed to speed up the system by allowing one console or the other to do the CAT scanning, and the other could be used to process the data at the same time.
Hospitals wanted 3M to provide a system that would allow a single 3M Laser Imager to be used on either console. 3M had been working on a system that was later called the Multi Modality Unit or MMU, that would take care of this problem. We were almost 2 years behind in the development of this unit and I had heard that G.E. would not sign a contract with 3M until this unit became available.
I was very curious about the perceived problems with developing the MMU, and found out that many of our people thought the signal from the Operators console was different from the Doctors console. I went to Midway Hospital in St. Paul and ran a test using our "test" Laser Imager that was installed there. I ran control and coaxial cables from each operating console of the G. E. computer. The control cable was used to transmit the video data and the coaxial cable was used to transmit the computer "clock" signal to the 3M Laser Imager for correct timing. I found that the bus clock signal from each computer was slightly different, and this was why 3M thought the signals from each computer would not be compatible in a single 3M Laser Imager. I found that the "clock" signal was the only difference. I was in fact able to bring up an image from either console and print it on the 3M Laser Imager with out any problems, as long as the computer clock from each console was used with it's particular signal. This dispelled any thoughts in my mind about whether the signals could be switched from one console to the other and be printed on the Imager.
I came back to 3M and showed the results to my boss and the supervisor that ran our "electronic design" section. Both still said that IT WOULDN'T WORK. I knew better because I had already done it in a test mode. I knew that I needed help to get a prototype built in order to give it a real try. I also knew that I would have to get it done by "bootlegging" the project right under my Boss's and the electronic design supervisor's nose. I went to two of the people that worked in electronic design and asked them to help me build the "box", in secret of course. I asked them to make it solid state so that I would only need a manual switch to do the switching from "A" to "B". I also wanted it to amplify the signal in case we had to make a long run from the switch to the Laser Imager. They very quietly built an all electronic device with three RS232 plugs and three coaxial jacks on the back of the box, and a single A-B switch on the front. Two of each of the RS232's and Coaxial jacks for the inputs and the third set for the output to the Laser Imager.
In order to keep my test secret, I could no longer go to Midway Hospital, because the Chief Technician knew what I was up to and demanded that I give him the first prototype. He already knew the potential! I instead went to Unity Hospital near Coon Rapids, Minnesota. I also knew the Chief Technician there and he agreed to let me use his GE cat scanner after hours.
The first test showed that I had lines in both images, and I soon found they were caused by the RF signal from the Bus Clock on each computer. I went out to my car and cut some capacitors out of my HAM radio and installed them inside the box on each input and output coaxial cable to bypass the RF signals to ground. The problem was solved, and the images were excellent. I also had to repair my HAM radio!
I went back to 3M the next day and showed the results to my Boss and the Electronic Design Supervisor. They were both angry because I had bypassed them and threatened to punish the guys that had built the box. I refused to tell them who had done it and it was soon forgotten. They knew that this was going to save them and the GE contract. It just happened that the Technician at Midway Hospital had told the GE Salesman about my test and he passed the information on to his home office. G.E. agreed to sign the contract only if 3M would produce my "A-B" switch.
The ironic part was that they sent me to 3M Italy a few weeks or so after the box had been "bootlegged". I was gone for about 3 weeks, and during that time, someone went through my desk, found the plans, went to our 3M New Ulm, MN. plant and had 50 or 60 units built for the G.E. contract, all without telling me what was happening. I had the last laugh on them for doing it that way because the units they produced didn't work properly because of those RF interference line in the images. They didn't know that I had added some .002 MFD capacitors to the units to bypass the stray RF signals. When I got back from Italy, I received several angry comments from them because the unit didn't perform as I had said. I very calmly said I can solve that problem in about 20 minutes, and I did.
The A-B switch worked well on many other kinds of CAT scanners, and was used to "save" many other accounts from going to the competition. I would guess almost 1000 units were produced and sold to several companies and hundreds of Hospitals. They were produced until the MMU came on line, which was close to 2 years later.
I never received any thanks or compliments for "inventing" the A-B switch. I think I might have embarrassed too many of the people who said it couldn't be done!
The 3M Trimatic Cassette/Film Changer was designed and developed at the 3M plant in Ferrania, Italy. I must hand it to my Italian friends, for innovation in the development of this fine piece of equipment. The Trimatic was designed to remove film from a cassette and feed the film into an attached film processor. The unit than replaced the removed film with a fresh unexposed sheet, closed the cassette, and returned it to the technician. The machine is placed out in a lighted environment, and is intended to replace the traditional dark room.
The only thing the technician has to do is feed the film cassette into a slot at the front of the Trimatic, and the machine does the rest of the operation.
The operational concept is simple, but the machine design could not have happened with out the use of microprocessors to control the complicated functions.
The machine is built in modules that can be installed or removed depending on the number and sizes of films that the hospital uses. The normal module stack is 7, which provides the hospital with 7 sizes and/or types of films to operate with. Each module is detected by a system using a bar code to identify the film size and film type. Each cassette that is used in the system also is identified by an attached bar code label on its surface, thus matching cassette to module.
When a cassette with an X-ray exposed film inside is slid into the front access slot, the system detects the cassette and pulls it into the unload area. A special device opens the cassette and another pick-up arm removes the film and begins the transport of the film into the waiting film processor. At the same time, the correct film supply module is brought into action, and a film is removed and transported down a series of rollers into the waiting cassette. When this operation is completed, the cassette is closed and returned to the operator. This operation takes about 18 seconds to complete the full cycle. The dry to dry operation of the film processor can take anywhere from 45 to 90 seconds depending on the system used with the Trimatic.
There are several other manufacturers that produce products that are similar to the Trimatic. They may operate differently, but they perform the same function.
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Last updated on 5 July 2008