By Aaron Molen
There continues to be controversy inside and outside our profession on how much radiation exposure is justified in the pursuit of diagnostic information. In the end there is no golden answer that will address every situation and ultimately I cannot tell you what’s appropriate in your office. However, I can arm you with information that will enable you to make an educated decision regarding what’s best for your patients.
There are many publications and websites that try to accurately compare effective radiation doses, but it’s not that simple. For example, there are two ways to quantify effective radiation, the ICRP 1990 recommendations and the ICRP 2007 recommendations. The 2007 recommendations give more weight to the salivary glands, skin, and other organs than before which results in effective doses being higher when measured using the 2007 recommendations. Most publications, though, use the 1990 recommendations which were written before the release of the 2007 recommendations. Comparing 1990 to 2007 based doses is like comparing apples to oranges so you should double-check which method is being used.
Secondly, the absorbed dose of a CBCT system varies widely within the system itself based on the FOV, scan time, kVp, and mA settings used in the scan. Recognizing this is important because sometimes CBCT manufacturers will report their scans with the lowest radiation dose and the scans of their competition with the largest radiation doses. It’s paramount when comparing effective doses between different systems to standardize the previously mentioned settings as much as possible to create a fair comparison.
Finally, the radiation dose measurement depends on the phantom used by the company, or researcher, to measure the dose. There are a number of different phantoms available that can have a varied number of sensors placed in them to measure the dose.
It’s for the above reasons that I will not be discussing specific radiation doses in this blog post since I believe with all these variables it can be like comparing apples to oranges. Instead when the time comes to make your decision as to which machine to buy or use I would encourage you to use the information we’ve thus far discussed to filter through the always changing information available in peer-reviewed journals or in the published material from the manufacturers themselves.
Using Cone-Beam in Your Office
Each orthodontic practice has its own unique set of patients and each doctor uses their own personalized treatment approaches to delivering the best care possible to their patients. Since each practice is unique, each practice will also use cone-beam differently.
In keeping with the ALARA principle I believe orthodontists should answer the following questions before taking a CBCT scan: (1) How does the dosage of this specific scan compare to my normal 2D radiographic series; (2) Does the additional 3D information have the potential to change my treatment plan; and (3) Does the additional 3D information have the potential to create a better treatment outcome for my patient? How you answer these questions will determine for each patient whether taking a CBCT scan is warranted in their unique case. Since each office has their own unique set of patients and uses their own unique treatment modalities, some orthodontic offices will take less scans than others. In the end the goals of protecting our patients, while delivering the best treatment outcomes possible must be balanced by each orthodontist. Hopefully with the information I’ve provided orthodontists can find that balance with more confidence.