Manufacturing Challenges with the Original Mini C-Arm

By Larry Grossman, Inventor of the Mini C-arm

Manufacturing Challenges with the Original Mini C-arm

Overcoming early engineering and manufacturing problems with a new product is never easy. The Fluoroscan was no exception. With funding in hand, the challenges began.

X-ray Tube Arcing

The low-intensity high-voltage power supply was a new invention engineered exclusively for the Fluoroscan Mini C-arm by Arthur Ruitberg of NASA, patented by NASA, and exclusively licensed to HealthMate, Inc. In the first prototype, the power supply controlled the X-ray tube, which was specially designed to emit a fraction of the radiation of larger X-ray machines. Eureka, Inc., a reputable supplier in the medical X-ray industry, was engaged by HealthMate, Inc. to develop the specialized X-ray tube. During the initial testing of the prototype, the power supply arced, causing the X-ray tube filament circuit to spike in current. This caused the filament to overheat and melt, instantly destroying the X-ray tube. It took months of re-designing both the power supply and the specialized X-ray tube to correct the problem so manufacturing could begin.

Operating Stand with an Articulating Arm

The Mini C-arm required an operating stand with an articulating arm that held the C-arm and enabled it to be maneuvered into various positions as required by the surgeon. HealthMate’s mechanical engineers developed a prototype for an arm but it proved to be too heavy, causing the stand to tip over.

In order to compensate for the weight, the engineers determined that the legs of the stand should be hollow and filled with lead pellets to weight the stand and prevent it from tipping. This concept worked in the testing facility but failed in an operating room environment, where there were cords on the floor from various equipment. As the Fluoroscan rolled over the cords, the plugs on the legs would fall off, causing the lead pellets to fall out of the legs and onto the operating room floor, destroying the sterile environment. The legs were re-engineered using larger lead ‘bricks’ instead of pellets that could not fall out.

High Voltage Power Supply Leaking

Tests of the new Fluoroscan power supply were initially successful in an operating room in Scottsdale, Arizona. It worked as expected. During a second test, conducted during surgery at a Denver, Colorado hospital, the oil that was used to cool the power supply started leaking onto the operating room floor, once again destroying the sterile environment. The machine was brought back to the R&D manufacturing facility in Scottsdale, where it worked without issue. Further research finally indicated the problem had been caused by Denver’s altitude. The change in air pressure forced oil out of the seals and gaskets. The HealthMate, Inc. engineers redesigned the power supply with a reserve tank and recirculating pump, which collected the leading oil and redistributed it to the power supply.

Fiber Optic Taper

The night vision image intensifier was 25 mm round (about 1 inch). In order to obtain an acceptable field of view the Fluoroscan needed a minimum of a 75 mm field of view (about 3 inches). The engineers needed to attach a fiber optic taper (25mm to 75 mm) from the image intensifier to the camera. HealthMate, Inc. commissioned the Schott company to make a special taper to fit the requirements of the Fluoroscan. A problem arose when the tapers developed dark spots on them during the manufacturing process, which was unacceptable for medical imaging. It took six months for Schott to develop a specialized technique to manufacture tapers without dark spots.

Hard Copy Image Storage

The Fluoroscan was being used for medical purposes and insurance companies required hard copy proof of all procedures. HealthMate, Inc. needed to provide that capability on the Fluoroscan before the machine could be sold and used for surgeries. The only way to accomplish that at the time (1982) was with a Polaroid camera. HealthMate, Inc. engineers developed a mounting device that allowed for a Polaroid camera to be swung into position to take a photo and then swung away from the surgeon’s field of view. The concept was tested successfully and put to work in the field. Insurance companies, however, reimbursed at a higher rate (300%) for fluoroscopy (real-time video) versus an X-ray (still photo). A VCR (video recording machine) was added to the Fluoroscan’s hard copy capabilities. HealthMate, Inc. contracted with BASF to produce special shorter-length videotapes so that all surgeries would have their own tape record.

After overcoming these early engineering and manufacturing problems, the Fluoroscan was ready to be sold and delivered in 1983.