If you ever came across a situation to choose between CSI and GOS detector, what would you choose?.

Based on a common question that we are always asked; “which flat panel detector is more convenient for my practice, the GOS or the CSI detector".

There are two main materials being used as scintillators in the manufacture of these flat panel detectors: gadolinium oxysulfide (GOS) and caesium iodide scinitilators (CSI).

CSI flat panel detectors have the advantage of higher resolution and less x-ray dosage applied to the patients. You can apply around 10% less dose using the CSI detector and get same results of GOS detector. On the other hand the CSI detectors are roughly 20-25% more expensive.

A) X-Ray Dosage:

Does 10% sound like a big number? We can do a quick mathematical equation to understand the effect.

We can say the average common spine exposure is about 1 mSv in dosage. It varies depending on the machine, FOV, patient…. etc.

So, doing the calculations, the 10% more dosage using GOS detector for a single spine x-ray is equivalent to 0.1 mSv.

Sounds Good! But what is the annual limit for radiation exposures? 

Based on the Australian Government’s primary authority on radiation protection and nuclear safety. the current limit of radiation exposure for an individual is 20 millisieverts (mSv) per year averaged over 5 years, and not more than 50 mSv received in any one year.

• 20mSv ≈ 20 spine x-ray exposures using CSI FPD ≈ 18 spine exposures using GOS FPD.

Although we do not have clear numbers about the average dose from CR systems to achieve same GOS results as there are so many factors included, it is on average of 5%  ̴  15% higher.

(20 mSv ≈ 8 CT Head examinations ≈ 3 CT head+abdomen+pelvis examination ≈ 1 PET CT examination).

So, the extra x-ray dosage from the GOS detector for spine x-rays will not be the huge contributor for the patients to reach their annual exposure limit.

Although we proved the differences are minor, we should always strive to make exposures as low as possible following the “As Low As Reasonable Achievable” principle (ALARA).

B) Resolution:

However, the resolution of the CSI detector is slightly better, it is still an advantage that cannot be ignored, even if it can contribute to one more pathological finding for every hundreds or thousands of cases.

Obviously, the CSI detector is a better choice. But because of the budget constraints, whether you are introducing a new digital imaging service or upgrading from a Cassette Reader (CR), this is one step forward towards a better service to the patients and to the community.

"HEDI Tech” is always trying to narrow the gap in price between the GOS and CSI flat panel detectors as a minor contribution towards achieving better service to patients.

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