1963 to 1993
The x-ray equipment as I knew it, when introduced into the business in March of 1963 was fairly advanced but somewhat unreliable because of the use of vacuum tubes and relay logic to control the functions. Vacuum tubes tended to grow "soft" with age or just plain burn out thus causing failure or loss of proper regulation of equipment. Tube failure could even be caused by relay and X-ray contactors vibrating in the cabinetry. Relays and contactors tended to get dirty or burned contacts which could cause many problems. Because of the high DC and or AC voltages used in the control circuits, things like resistors and capacitors tended to burn up or fail quicker. This old style equipment was still around, and was being used when I first arrived on the scene.
The first hospital that I went into had a room that was as archaic as you could imagine. One small room was loaded with transformer equipment and large capacitors that were literally "banked" up against the wall from floor to ceiling in what was called a "capacitor bank". This was the room where the voltage was built up from 220VAC Single Phase to almost 100,000 Volts DC or more. The high voltage was than sent into the adjoining X-ray room through a series of open conductors near the ceiling that carried the high voltage to the x-ray tube. It was really scary! In order for a service technician (like myself) to work on the system, you had to go into the capacitor room and discharge the capacitors with a large well grounded paddle, which had a metal plate on the far end and a very long wooden handle on it to prevent electrocution. You had to leave the grounded paddle touching the top most capacitor as you worked on the equipment because the voltage would build up all by itself, just setting there. You haven't been properly educated until you experience this kind of High Voltage discharge through you're own body! I judged it to be very close to "shock therapy", if not worse. In today's terms they would call it "clearing your register". I know, because it happened to me on several occasions through the 5 years that I worked directly in the X-ray repair business.
We had a sales/service man in North Dakota that almost got killed when a technician stepped on the fluoroscopy foot switch while the salesman was working on the X-ray tube in the table. The high voltage cable termination had been removed from the X-ray tube and was laying on the bed of the table, when the foot switch was actuated when an x-ray technician stepped on it. The salesman had neglected to remove one of the power inputs to the High Voltage transformer, which was a safety requirement when working on the High Voltage circuits. The High Voltage traveled from the loose cable termination, through the table and exited through the salesman's leg and into a metal plate in the floor that he had been standing on. It ripped his leg open to the bone from the crotch down to his knee. It took a rather long stay in that same hospital to help him to recover. His friends said he was never the same after that.
I had an occasion to get a High Voltage jolt when I had been in the business about 8 or 10 months. I was servicing a shorted high voltage X-ray cable in a hospital in St. Paul, and had the High Voltage cable termination out of the X-ray tube, hanging from the ceiling. The usual procedure for testing for a shorted cable was to remove the suspected cable from the X-ray tube and let it hang while you made an exposure. If the circuit breaker blew, you knew you had the shorted cable. A rather beautiful young female X-ray technician came into the room and asked if I had found the problem. Totally distracted by her, and wanting to show her how good I was at my job, I rather casually leaned against the X-ray table with my hand on a metal rail, and I pointed to the cable which I had tied to the tube crane before the test. My pointing finger got within 7 or 8 inches from the tip of the cable, when it discharged from the cable through me to the grounded X-ray table. I had forgotten that a shorted cable becomes capacitive and will hold a charge when shorted. I was zapped with almost 70,000 volts in a heartbeat. She didn't realize what had happened, but I can guarantee you that I did! I think my whole life went before my eyes in a nanosecond. It took me almost an hour to stop breathing hard, re-terminate the bad cable, and get the room back into operation. As I said, you haven't lived until it happens to you.
Another story revolves around the great guy that really trained me in the X-ray business. He had asked me to meet him at a hospital in Minneapolis, and when I arrived at the room where he was supposed to be working, I found a streak of transformer oil going up the wall and across the ceiling. The streak started from the High voltage transformer tank. I knew that he was changing out a shorted Valve tube in the tank because he had asked me to bring one along for the replacement. The normal procedure is to use a long bladed screwdriver to reach into the tank and short the plate cap on the valve tube to ground. He did just that, but he failed to ground out the screwdriver blade first. The same thing happens when a valve tube is bad, the thing goes capacitive and holds a charge. I found him in the coffee shop still breathing rather hard from the jolt. We all did it at one time or another!
This was my introduction to the X-ray business. By the way, that archaic room with it's capacitors and power supply equipment were removed several months later so that a new more modern machine could be installed. Thank GOD.
The machine consisted of a large cabinet that was usually in a well protected lead lined "control" room that was separated from the main X-ray room. The cabinet was called a Console. Most functions were controlled using electron (vacuum) tubes. The console contained a well insulated 220VAC single phase 500Amp (more or less) input which was terminated in the console and controlled by a very large "contactor". A large breaker box on the wall could be thrown to cut the power to the unit. The console also contained all of the necessary electronics, and mechanical switches to set the Kilo voltage, Milli amperage, Timer, MA stabilizer, and other items that could be in the unit depending on the cost of the installation.
The above mentioned contactor (a large relay style breaker device) was controlled by the timer which would power the unit for a specific or preset time. The contactor buttons when in the closed position would pass the preset voltage on to a large transformer (large oil filled tank) usually located some where in the X-ray room proper. The oil filled transformer tank contained the transformer (it converted adjusted AC to Kilo voltage) and very large rectifier tubes called "Valve" tubes which converted the AC to DC through rectification. There were usually 4 tubes installed in the oil filled tub which would take the voltage and convert it to DC voltage which was than transported through special high voltage cables to the X-ray tube which was enclosed under vacuum in a special pyrex glass housing. The X-ray tube would than convert the high voltage/current to X-radiation which was projected through a special pyrex glass window in the tube. The X-ray tube sent photons or bundles of X-radiation out and through the patient. The altered X-ray beam would than impact on film which was mounted in a light tight cassette, thus producing an image (really just a shadow of the patient) on the enclosed film.
There were usually 2 X-ray tubes in an average X-ray room . One of the tubes was mounted on an overhead traveling crane. This tube could be used over the X-ray table (where a patient would lie) or repositioned to face the wall where a special holder was mounted to hold X-ray cassettes for "Chest" X-rays, or other special studies. The second X-ray tube was mounted inside the X-ray table, and was setup to travel within the confines of the inside of the table. This tube was powered up whenever the Radiologist wanted to do Fluoroscopic studies or actually make a full powered X-ray exposure of some part of the patients body. Fluro studies were really Low KV, Low MA studies which were at first viewed on a special Fluro Screen which fluoresced when struck with X-radiation. Later this screen was replaced with an "Image Intensifier" tube which was designed to amplify the image by over a thousand times in intensity. This image was projected onto a special mirror which the Radiologist viewed.
Advances were made, when the images were projected onto Plumbicon, Image Orthicon, or Vidicon tubes, where the image was than picked up by television monitors. This evolution took place over a number of years, but was significant in reducing the patient exposure to X-ray by hundreds of times. Where an old study would require up to 100MA of exposure, the new techniques used 1 or 2 MA.
The advent of Solid State equipment , allowed better control of all aspects of the generation of X-rays. Instead of using "valve" tubes, solid state rectifiers are now used. All timing and related circuits are now controlled by using microprocessor technology. The output is now (usually) digital instead of analog. X-ray tubes now use (and have used for several years) special high speed rotating anodes. Incidentally, this technology (rotating anodes) was adapted into the Space industry for use in outer space applications where the requirement for bearing technology could stand the vacuum. Where else could you find special bearings and lubricants that could be operated in a vacuum? The evolution of the X-ray tube is a study all by itself. When I first started, the tube had a static tungsten anode which when struck with electrons converted them to X-rays. But the heat generated by the very action of conversion was unbelievable. This led to many premature failures of the X-ray tube. You could actually find X-ray tubes with holes burned through the tungsten anode.
Then someone came along with the idea that a very heavy rotating tungsten disc inside a special glass envelope would help to dissipate the heat. Each time the pulsing DC electron beam hit the rotating disk, it would strike at a different place on the surface. This allowed each spot where the beam struck, to cool down slightly before it was hit again. Along with this was the problem of bearings and grease that would not only operate for long periods of time, but not break down from the heat that was generated. The heat was dissipated through those very bearings on the rotator, Stator, and glass that held the vacuum. This was one of the great break breakthrough in the history of X-ray generation.
In today's operation of an X-ray room, one would almost not recognize it when compared to rooms that were used 20 to 30 years ago. Today you will more than likely have a study done on a CAT scanner , PET scanner, Ultrasound, or a MRI machine which uses the actions of reacting body parts to produce an image. Images produced by this equipment are converted to digital data and stored in solid state memories or on computer hard drives. The data can be archived and later recalled, and sent to devices that can print the resultant data onto film for hard copy review by the radiologist. 30 years ago, these procedures would not have been possible, and could only be dreamed about.
Don't get me wrong, they still do standard X-ray procedures on standard X-ray tables and other devices that were around 20 or 30 years ago. But today you would be hard put to find a hospital that doesn't use an automatic "chest filmer" unit for making routine chest X-rays. These units are almost always attached to a dedicated film processor as a time saver. Time in a hospital, in today's world is everything! They still do procedures on X-ray tables such as "Upper and Lower G.I.'s". They still use a standard procedure for shooting a Foot or Body part when looking for fractures or whatever. But it's the new style devices that have come along in the last 10 to 15 years that are paying most of the Bills in the Hospital. Can you imagine a building that is dedicated to CAT scanners, that has to remain open almost 24 hours per day just to keep up with the patient load? Years ago the average hospital was done with all procedures by somewhere around 3:30 PM. each day. Now a service person has to try hard to find a time when he or she can come in to do routine or even emergency repairs.
Times have changed!
As stated, 30 years ago a single film would have taken 30 or more minutes to be produced and be ready for reading by the Radiologist. Some times the Radiologist would do "wet" reading of the films in the dark room in order to speed up the system. He would pull the wet film out of the developer tank and read it by holding it up to one of the RED safe lights in the dark room. Some of them were good enough that they could "sight develop" the film. In other words, they would determine when the film had enough development time by looking at it against the red lights and popping it into the fixer tank to stop development. They were trying to Speed up the system! Now in some Hospitals, you may be lucky to find a dark room that is being used. How times have changed!
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Last updated on 14 January 2006