When should we take a Cone Beam CT? Careful with that radiation, Eugene Part 3
There is no doubt that CBCT has revolutionised orthodontic imaging. But when are we justified to take a CBCT?
I think that CBCT imaging is great. It certainly enables us to see the things that we could not see on conventional radiographs. However, we need to consider whether the additional radiation exposure is justified. I have posted about this several times before and this generated a lot of discussion. It is, therefore, relevant to see this update paper in the EJO.
Annelore De Grauwe et al
EJO: on line: doi:10.1093/ejo/cjy066
The EJO have made this open access and this means that you can access it without being a member of the EOS. This is great news!
They started the paper with a nice literature review. Importantly, they pointed out that the dose from a CBCT is still higher than conventional 2D radiographs. They also emphasised that there are three fundamental principles of radiation protection. These are justification, optimisation and dose limitation. Finally, they mentioned that the SEDENTEXCT guidelines stated that it is not possible to differentiate between safe and harmful exposure because of stochastic effects. So we need to be careful.
What did they ask?
They wanted to find information on the diagnostic efficacy of CBCT in pre-orthodontic treatment children.
What did they do?
They did a systematic review with the following PICO
Participants: Paediatric patients
Control: 2D radiography
Outcome: Treatment change caused by the availability of CBCT images
They searched for papers that described diagnosis, therapeutics and efficiency when comparing CBCT and conventional imaging.
They did a standard systematic review with two independent assessors carrying out the paper search, data extraction, and paper identification. Finally, they assessed risk of bias and quality.
What did they find?
Following their extensive search and planned exclusions, they obtained a final sample of 37 articles. They assessed the quality of the studies using the Quality Assessment of Diagnostic Studies (QADAS). This tool is used to assess the quality of diagnostic studies. You can find further information here.
They presented a narrative of their main findings and divided them up into several sections. I thought that the most relevant were:
CBCT showed better detection rates than 2D images. For example, 63% more root resorption was detected with CBCT than with 2D views.
They only found three papers on this area. These showed that CBCT was better than 2D imaging in detecting root fractures.
CLP and other craniofacial problems
CBCT was clearly superior to 2D views in rendering cleft volume, root morphology, the outcome of bone grafting and imaging complex problems.
They summarise their main findings by suggesting that CBCT had advances over 2D imaging in the:
- Diagnosis of root resorption
- Evaluation of root fractures
- Imaging of complex craniofacial problems.
What did I think?
This is an important area of our practice, as we can cause harm by over exposing children to unnecessary radiation. I thought that it was important when they related their findings to the SEDENTEXT guidelines and the DIMITRA position statement.
Both these documents clearly state that CBCT was not recommended for detection of cysts, periapical lesions, periodontal assessment and periapical disease.
In fact, SEDENTEXT is very specific. They could not recommend CBCT as a standard method of diagnosis and treatment planning in orthodontic practice. Finally, SEDENTEXT sets out this bold statement.
“Where health professionals change their practice to adopt a diagnostic technique where there are radiation risks to young patient groups, the onus is on them to demonstrate significant improvements in patient outcomes”.
I thought that this statement was very relevant when I looked at the supplementary data on radiation doses in the studies that they included in this paper. (Table 2 in this link)This showed that the dose from CBCT ranged from 26 uSV to 194 uSV. Whereas the dose from a paediatric panoramic view is 5 uSv. These comparative dosages look pretty high to me!
I cannot help thinking that this is a complex area of our care, or is it just confusing to me? It appears there are some clear indications for using CBCT and these are outlined in this paper and the advisory documents from SEDENTEXT and DIMITRA. Importantly, they do not suggest that CBCT should be routinely used in an orthodontic patient population. Yet, we seem to be starting to use CBCT in this way. Surely, it is clear that CBCT is not necessary for most of our patients when we consider the possible risks and the potential harm that we may cause.
Emeritus Professor of Orthodontics, University of Manchester, UK.