Your Tubehead Might Not Be Doing What You Thought It Was
We recently had an experience where a dental office found it hard to believe that it took such a huge difference in tube head timing to achieve the same image results with their digital X-Ray sensor image.
In this specific instance the office had three tube heads, two of which were the same make and model as each other and the third tube head was a different model. The two similar tube heads were DC tubeheads and the third tubehead was AC.
To achieve the same image results in all three rooms the timers had to be set at
. 13 seconds on the AC 70KV Tubehead
.20 seconds on the first DC 60KV Tubehead
.26 seconds on the second DC 60KV Tubehead
This was with the same sensor, the same computer, and the same patient. Obviously the doctors initial belief was that there must be something wrong with his computers, monitors, or the sensor. We take our customers concerns seriously and we explained that we get the same results with different sensors and even if we do not change the computer from room to room
We discovered three really incredible things.
1. The rate of exposure was very different from sensor to sensor. We found that the three tubeheads when set to these three different settings all gave us total dosage results that were within 5% of each other.
2. We found that although the different tube heads had different rates of exposure they had very repeatable exposure results. In 36 exposures on each of the tube heads and 36 times they gave the same exposure time within .002 ms (This exposure time never matched the number on the dial though) and they emitted the same dosage within 25 micro grays.
3. The two tube heads that were of the exact same model had a 15% difference in their exposure rate. It was incredible seeing that if we set two tube heads in the same office, that were the same model, to the same timing setting it produced 15% more radiation in that time period.
Unfortunate things we discovered
- The timing was off by 7% on one tubehead, 13% on the second tubehead and 15% on the third tubehead.
- The radiation Exposure varied greatly from one tubehead to the next