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April 10, 2006

First Person
Is Your Treadmill Affecting Your Camera? Secrets of a Nuclear Medicine Field Service Engineer
By Michael W. Buzard
Radiology Today
Vol. 7 No. 7 P. 30

Save money and your equipment with these tips.

Editor’s Note: This article is the first in an occasional series of people’s individual professional stories in radiology. Michael W. Buzard is an experienced nuclear medicine field service technician.

I service equipment for a well-known nuclear medicine manufacturer. The following are some observations gleaned from my years of service experience. Nuclear medicine rooms can work without following these guidelines, but they won’t be optimal.

The most common shortcut in designing a new room is to leave out the lead lining of the walls and doors. Recently at a new facility, I stood in front of a doctor who was experiencing flashes in two frames of many heart studies. I informed him that he had positioned his treadmill directly across from the front of the gamma camera. This means that each head would be directly facing the treadmill at some point in the camera’s rotation. There was a wall between the treadmill and the camera, but the wall was not lined with lead. So during a heart study, if a patient was on the treadmill, there were two positions when radiation from the patient on the treadmill was also being seen in the study. The problem was solved with a roll-around lead shield.

Here is a common scenario: You have three nuclear cameras and a busy department. Camera No. 2 is due for preventive maintenance and calibration. Your service contract includes standard coverage between 8 am and 5 pm. Normally, you use the hour from 7 to 8 am for quality assurance (QA) and the department schedules patients between 8 am and 4 pm. Can the service provider be expected to give you a good preventive maintenance (PM) and calibration on camera No. 2 Wednesday between 8 am and 5 pm to avoid overtime charges?

The answer is “yes” if camera room No. 2 is lead lined and the background can be maintained at or near 300 counts per second intrinsic with a detector with no collimator. If the background cannot be maintained at or fewer than 300 counts per second intrinsic, you should reschedule the maintenance or pay the overtime if you want a good detector calibration (tune).

Overtime & Contracts
In many cases, the room is not designed for low background. Usually, the emphasis in the design is mostly on getting a patient scanned. Having the ability to seal a room from outside radiation is not a priority; however, it should be. The increased costs of paying overtime because you can’t tune during normal working hours can greatly outrun the cost of the initial lead lining of the room over time. It can also cost the department revenue because some repairs cannot be accomplished in a “hot” environment. If the camera must be tuned to complete the repair, the service person must wait until later in the day when the room is clear. In such a scenario, the room should be clear with low background by approximately 4:30 pm; overtime kicks in at 5 pm.

What’s the difference? A service that would have been covered in your contract if the room was lead lined will now cost you $500 per hour. Even worse, if you lowered your patient load for that day to accommodate the maintenance, you forgo a great deal of revenue and gain nothing in return.

Along the same lines, your waiting area, injection area, and bathroom should not be in direct line of sight to the camera’s detectors. If a radioactive patient walks through a nuclear area with no lead separation between cameras and three heart studies are occurring at the same time, it is possible that the patient walking could cause a bright flash on all three heart studies. Hence again the answer to “Why are there some brighter frames in some studies?”

Studs in Floods
The following is a scenario I must include, only because it really made me laugh. I received a call from a customer who had just built a brand new facility. When I asked her what the problem was, she said, “I’ve got studs in my floods.” I asked her to clarify the statement and she said, “It looks like I can see the studs in the wall.” I asked her how she was doing the flood. She said she had hung a 0.5-milicurie technetium source on the wall approximately 8 feet away and centered on the intrinsic head, just as she had been trained to do. Then I asked her to check the room on the other side of the wall. Sure enough, one of her coworkers was preparing to scan a patient in the adjoining room. With no lead in the wall, the patient dose in the next room was producing more counts on her camera than the QA dose she was using and she was indeed seeing the metal studs in the wall.

Another scenario: We are again trying to accomplish a PM in nuclear room No. 2. This time the room and door to the room are lead lined. The service technician is on his way and should begin at 9:30 am. At 8:15 am, you receive a patient for an emergency lung scan. Is it OK to do the lung scan in room No. 2? If you do the scan, the scheduled PM may be in jeopardy. It is very likely that a ventilation lung scan will cause the room’s background to elevate much higher than 300 counts per second and, therefore, not be optimal for tuning the detectors for several hours.

It’s the Humidity
Humidity, another often overlooked problem, affects at least two important aspects of your operation. The first is static electricity, which becomes a potential problem when humidity is too low. Most electrical control circuits in modern cameras are low voltage and can be easily affected when you touch the grounded metal case of the camera and discharge a high static charge.

The low room humidity limit for my company is 20%. Anything at or below this limit may cause increased static problems with your system. Using an antistatic mat and monitoring and correcting low humidity can help eliminate the problem. In one of my accounts, the techs resorted to wearing rubber gloves in the department, which was registering humidity at 20%. The gloves were a creative short-term fix to keep from shocking patients and having static discharges into the gantry. Shortly after having a static charge take out a $4,000 computer motherboard (that was not covered in their contract), the maintenance department decided to purchase a humidifier.

At the opposite end of the spectrum is humidity at or above 60%. This can cause areas of the camera to sweat and possibly short circuit. In most cases, these limits are laid out by the manufacturer and are therefore the responsibility of the camera owner to maintain. In other words, if you exceed the guidelines of your warranty, the contract may not cover the repairs.

Another common problem in nuclear rooms is heat. Modern cameras contain a generous helping of computer equipment. Computers are very susceptible to heat. My company recommends that heat be set at or below 70° F in the camera room. This problem commonly surfaces when seasons change, so the staff adjusts the thermostats to compensate. When patients complain that the room is too cold, reach for a nice warm blanket and leave the thermostat set low. This will greatly help your computers stay healthy and keep your camera producing consistently good studies.

A rapid drop in temperature could crack your camera head crystal. Let’s say you come in one morning and your heating system has gone haywire, raising room temperature to 90° F. Thinking this will harm the computers, you decide to open a window. It’s winter and 10° F outside. The next sound you hear may be some very expensive crystals cracking on your camera heads. A better idea is to cool down the room slowly.

Clean Power
You should also give great consideration to electricity and electrical energy in the camera room. Again, it is usually the customer’s responsibility to provide clean power to the equipment. A line dedicated for main power to the camera is best. A Universal Power Supply (UPS) is often used with the camera; however, the UPS usually has limits. Most UPS systems are not designed to run the equipment indefinitely. In many configurations, it is only capable of running the system long enough for you to complete a study and do a proper shutdown in the event of a power failure.

The following is another example of a problem with electrical energy in the room that nearly drove me crazy. I was asked to look at a camera that had suddenly started having energy shifts. When you would watch the spectrum, the energy was definitely moving off the 140 peak to approximately 145 and then back again. After spending several days working with other engineers and quite a few parts troubleshooting the problem, we found that the department had located a new patient paging system in the room very close to our electronics cabinet. The system was similar to those that some restaurants use to let you know your table is ready. The paging system was emitting a high-energy pulse every five seconds. The pulse was also being picked up by our circuitry and was causing a peak shift. After the paging system was removed, the camera operated normally again.

Drinks around keyboards can and will cause damage to computers. If you spill into a keyboard and damage it, or your monitor goes out and brings you to a point where you don’t think you can shut down the computer properly using the keyboard, please think before you decide to shut it off. Unless there is an immediate hazard, you should try to shut it down remotely, either through another computer or wait and let the service person shut the computer down. This may keep you from crashing your hard drive.

You can certainly cause a lot of damage to a rotating gantry with stainless steel carts and step stools. When a very heavy steel gantry rotates into a well-made steel cart or step stool handle, it can rip parts off the camera or send the cart or stool flying. Either way, it’s not good. Try to keep them in a specific designated location away from the gantry. Foreign objects have been known to cause the camera to tip when encountered by a rotating detector or moving gantry, causing patient injury or death.

When designing or remodeling your nuclear department, please give some thought to these ideas. It will help you produce great studies and lower service costs, and it will help me keep your cameras in service.

Bottom Line
Design facilities to retain good QA and good studies and you will save money in the long run. Allow 8 feet from the intrinsic detector to the source holder for QA if you can. Ensure that radiation sources—including patients who are not being scanned—do not pass in front of detectors while a patient is being scanned. It is best to lead line walls to separate cameras from all outside radioactivity. If you want to cut costs, you can just lead line the wall to 6 feet off the floor. Make sure all hot materials, including hot lab needles, sharps containers, and trash, are placed behind lead barriers. Use antistatic mats to help eliminate static discharge into camera. Monitor rooms for proper temperature and humidity. Use a dedicated electric line with a UPS for each camera. Locate the camera in an area that is free from high-energy pulse equipment or high magnetism. A clean room that is ready to begin QA is at or less than 300 counts per second intrinsic. Location of more background than that could shade your QA and affect calibrations or flood tables. Small sources such as a band-aid can be located by blocking angles to the detector with a lead shield. Tuning is commonly accomplished with 0.5 milicuries, so allowing any injected patient or radioactive object into a camera view area while tuning is in progress may compromise the tune.

Thanks, from your friendly nuclear service guy.

— MB

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