June 14, 2021

How many incidental findings do we detect on orthodontic CBCTs?

There is currently a debate on the risk/benefit balance of CBCT images for orthodontic patients. Some people suggest that the benefits of using CBCT images outweigh the risks. In contrast, others feel that we cannot justify the increased radiation dose. This new paper looked at the number of incidental findings detected on orthodontic CBCT views.

We all know that CBCT images provide much more information than conventional 2D views.  However, while this information appears to be valuable, we also realise that we obtain this at the cost of increased radiation exposure.  Some proponents of CBCT state that one advantage of using these techniques is that we may find Incidental Findings (IFs) that we would miss with conventional 2D methods.  However, there is little large scale research that has looked at this area.

This new study provides us with some helpful information.

 

A team from Korea and the USA did this study. Nature Scientific Reports published the paper. It is open access.

Effectiveness of 2D radiographs in detecting CBCT‑based incidental findings in orthodontic patients

Jin‑Young Choi et al. Nature: Scientific Reports.

https://doi.org/10.1038/s41598-021-88795-3

 

I have not reviewed a paper published in Nature before. It is challenging to get a report published in these journals, and I am not aware of such a high impact journal publishing an orthodontic article.

What did they ask?

They did this study to answer two questions:

“What is the rate of incidental findings of craniofacial disease or abnormal structures from 3D CT images that were taken for orthodontic diagnosis without other symptoms”?  And

“What is the detection accuracy of 2D radiographs compared to 3D CBCT images”?

What did they do?

They did a large retrospective study of case records of patients who had attended a dental hospital orthodontic clinic from January 2010 to July 2019.  They had taken the  CBCT images for orthodontic purposes only. Notably, the images had a wide field of view.

They found a total of 1020 images taken for 1020 patients.  They also collected 2 D images from the patients.

Two oral and maxillofacial radiologists then evaluated the images.  They classified the IFs into five categories.  These were

  • Maxillary sinus
  • TMJ
  • Nasal Cavity
  • Soft tissue calcification
  • Pathology.

They classified these as the “Gold Standard”.

The same two examiners reviewed the 2D images and compared the Incidental Findings to the CBCT “gold standards”.  This design gave them sufficient information to calculate the sensitivity/specificity, positive/negative predicted value and accuracy of the 2D images.

What did they find?

Their most significant finding was that they found at least one IF in 709 (69%)  images. The most common of these were nasal cavity problems, for example, nasal septum deviation.  The mean age of the patients with IFs was 22.3 years old, and the mean age for those without was 20.1 years old.

The highest accuracy for the 2D radiographs was 85% for soft tissue calcification. The lowest was 62.2% for nasal cavity findings.

In their discussion, the authors pointed out that these findings were similar to other studies. However, their sample was the largest that any researchers had studied to date.  They also pointed out that the FOV of their sample was very large and evaluated the entire craniofacial area.

Importantly, they did not find any malignancies or life-threatening pathologies in the CBCT images.

Their conclusions were;

“69% of the CBCT views contained an incidental finding. As a result, clinicians should be responsible for carefully investigating their findings”. and

“The accuracy of detecting IFs on 2D views was not high”.

What did I think?

This paper is very interesting and relevant to clinical practice. I was surprised at the high number of IFs that they detected in their population of patients. I was even more surprised that other authors had found similar levels. However, and I may be being a bit cynical here. What I want to know is how many of these IFs warranted onward referral and treatment. Importantly, the authors mention that none of the patients had a life-threatening severe IF.  Indeed, we may consider these IFs to be”normal” and expected.

These findings bring me back to the previous discussion. If we feel that the incidental findings are minor and not of clinical significance, we cannot justify taking higher radiation dose images.  Paradoxically, with such a high level of IFs, we also need to ensure that we are carefully viewing the 3D images.  As a result, we must be proficient in 3D image analysis or send our CBCTs to radiologists.    This dilemma is real, and I know that I would err on the side of caution and send my CBCTs for expert evaluation.  This practice was routine in the NHS Children’s Hospital that I used to work in.

Final comments

This paper deserves a debate. This subject is undoubtedly controversial. However, I am finding it difficult to interpret its findings clinically because of the absence of information on the action taken following the identification of the IFs. Nevertheless,  if I were still working clinically, I could not justify taking CBCTs in the search for incidental findings. Furthermore, I would get a radiologist to report the images.  Some may think that this is too cautious, so let’s have a debate in the comments.

Have your say!

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    I agree with your comments. I am not sure but that a deviated septum without a ‘complaint’ isn’t ‘normal’ variation.

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    Here (Netherlands and Germany) the guidelines state unequivocally that you may not take CBCT’s routinely (e.g. for orthodontic treatment planning) also not to replace an OPT. To take and / or review CBCT’s you need to have absolved an additional course.
    Carefully studying and diagnosing any X-Rays taken has always been required.
    In the guidelines indications for taking CBCT’s are listed.

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    Kevin, just to further the debate I would ask? Do you send your cephalometric radiographs off for evaluation by a Maxillofacial Radiologist to be safe since it covers roughly the same head and neck area?

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    The British Orthodontic Society Guidelines on the use of Radiographs indicate that ONLY when conventional techniques do not give enough information Small Field of View (FOV) CBCT images may be used. The location of unerupted maxillary canines is given as the most likely indication for their use.
    In all cases CBCT images must be reported on by an appropriately qualified and trained individual.

    Keith Isaacson

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    The reputable cbct mfgs all offer low dose protocol which is almost and in some cases less radiation than digital 2D imaging. For me to use 2D imaging it would be equal the amount of radiation. Why would I choose to have less information (with 2D) at my disposal when evaluating a case when the 3D radiation dose is the same?
    Disclosure: KOL for Planmeca

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      Thanks for identification as a Planmeca KOL and looking for clarification.

      Which Planmeca machine in low dose protocol when taking CBCT of the panoral region, creates lower dosage than THE SAME MACHINE in panoral mode?

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      THANK YOU FOR YOUR ETHICAL REPLY AND
      THAT YOU ARE A KOL FOR PLANMECCA.

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    I totally agree with you Kevin. I would not feel confident assessing a CBCT image with the risk of missing a cancer and would refer for reporting to a Radiologist. Fortunately CBCT imaging was only in its infancy when I retired!

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    Dear Kevin. Excellent point on the how the IFs can be considered ‘normal’ and expected. One other point I would mention is how many of these IFs lead a clinician and patient down a rabbit hole where the initial IF requires more tests and specialist consults? This can get costly and create unnecessary anxiety where none was warranted.

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    Dear Kevin. Excellent point on how the IFs can be considered ‘normal’ and expected. One other point I would mention is how many of these IFs lead a clinician and patient down a rabbit hole where the initial IF requires more tests and specialist consults? This can get costly and create unnecessary anxiety where none was warranted.

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    Quite right Kevin, the key point here is not how many incidental findings are made. It’s how often the CBCT information, over and above what would be detected with clinical examination and conventional radiographs, changes the management of the patient.

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    Thank you deeply for your introduction and comments on my Kyung Hee University Dental Hospital and UCSF div. Orthodontics’ research work. I am Seong-Hun Kim (Sunny) the corresponding author of this article.
    Yes we are quite proud of being published to the Scientific Reports as Orthodontic issues.
    Some issues raised by Kevin are needed to be explained more.
    1.” In their discussion, the authors pointed out that these findings were similar to other studies. However, their sample was the largest that any researchers had studied to date. They also pointed out that the FOV of their sample was very large and evaluated the entire craniofacial area.”
    Yes. even though our research showed relatively similar IF compared to previous studies, large FOV CBCT made five categorized IF systematically on the contrary to small FOV researches. We have many craniofacial deformity patients in the university hospital in korea. This means 3 dimension asymmetry evaluation, airway evaluation, alveor bone thickness evaluation, and both the upper and lower skeletal evaluation are needed. Only 1020 patients’s dicom files who took CBCT due to above reasons were .used from quite huge amount of Orthodontic department patients’ pool in my dental hospital. We also mentioned in the Discussion section the meaning of large FOV CBCT’s importance. .
    “In contemporary orthodontics, a large FOV is beneficial for complicated craniofacial or orthognathic cases30,
    and the evaluation of the TMJ area and pharyngeal airway has become more important for orthodontic patients. In addition, CBCT with a large FOV can replace conventional 2D radiographs, such as panoramic radiographs and cephalograms, because the region of interest (ROI) of the orthodontists includes all craniofacial parts, not only the dental area.” We also definitely mentioned the clinical indication of CBCT taking in this resarch article. “CBCT images are taken only in patients with special purposes such as the evaluation for orthognathic surgery, impacted teeth, alveolar bone housing, or transverse discrepancy at the furcation level, in cases which had definite benefits. If the benefits were higher than the expected risks, taking required radiographs could be considered to be allowed ethically.” I am quite confusing that many doctors who read this blog can blame our team that we do take CBCT routinely to every patients who do not need CBCT data. we are embrassed to this.
    2. “Importantly, they did not find any malignancies or life-threatening pathologies in the CBCT images.”What I want to know is how many of these IFs warranted onward referral and treatment. Importantly, the authors mention that none of the patients had a life-threatening severe IF. Indeed, we may consider these IFs to be”normal” and expected.”
    Fortunately, we did not found any cancer or malignancy to threaten the patients’ life. But, as we showed the actual case in the Figure 1, one six-year old male patient who visited to my hospital due to severe skeletal class III malocclusion with extremely flat palatal vault (we did palatal vault molding also) showed IF, Fibrous dysplasia of the right sphenoid sinus during orthodontic diagnosis. It is highly related with future blindness if this become grown. We transferred this petients to department of neuro surgery whenevere we found this, and he is now successfully controlled by neurosurgery team now. This is why we decide to perform this kinds of researches and submit this to the Scientific reports.
    “Despite the relatively low severity of pathologies found in this study, some of them required therapeutic interventions (Fig. 1).”

    3. “Nevertheless, if I were still working clinically, I could not justify taking CBCTs in the search for incidental findings. Furthermore, I would get a radiologist to report the images. Some may think that this is too cautious, so let’s have a debate in the comments.”
    Quite welcome the positive debate!
    Orthodontists in the post COVID-19 pandamic have big responsibility on quite new era such as craniofacial airway orthodontics, craniofacial deformity orthodontics, and psychological counseling orthodontics. If extremely low radiation dose CBCT apparatus become distributed worldwide, then radiographic evaluation and related treatment strategy will be changed revolutionary! I am all the time beliving this mention. ” GOOD SCIENCE COMES WITH OPEN MINDS!” Thank you again for your interest on my research article.

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    Some issues raised by Kevin are needed to be explained more.
    1.” In their discussion, the authors pointed out that these findings were similar to other studies. However, their sample was the largest that any researchers had studied to date. They also pointed out that the FOV of their sample was very large and evaluated the entire craniofacial area.”
    Yes. even though our research showed relatively similar IF compared to previous studies, large FOV CBCT made five categorized IF systematically on the contrary to small FOV researches. We have many craniofacial deformity patients in the university hospital in korea. This means 3 dimension asymmetry evaluation, airway evaluation, alveor bone thickness evaluation, and both the upper and lower skeletal evaluation are needed. Only 1020 patients’s dicom files who took CBCT due to above reasons were .used from quite huge amount of Orthodontic department patients’ pool in my dental hospital. We also mentioned in the Discussion section the meaning of large FOV CBCT’s importance. .

    • Avatar

      As a representative of this CBCT research, We also definitely mentioned the clinical indication of CBCT taking in this resarch article. “CBCT images are taken only in patients with special purposes such as the evaluation for orthognathic surgery, impacted teeth, alveolar bone housing, or transverse discrepancy at the furcation level, in cases which had definite benefits. If the benefits were higher than the expected risks, taking required radiographs could be considered to be allowed ethically.” I am quite confusing that many doctors who read this blog can blame our team that we do take CBCT routinely to every patients who do not need CBCT data. we are embrassed to this.

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    Dear all,
    I think the question we should always ask of any research is ‘So what?’. I accept that opg’s are necessary, I personally think that the vast majority of lateral Cephs are totally pointless. The CBCT’s I take are for impacted teeth (mostly canines) and third molars. Incidental findings are not a justification for irradiating children’s brains.

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    I get the impression that the authors of the paper under revision consider ‘non-dental IF’ a positive yield of the large field CBCT.
    Let us take a step back: We collect diagnostic information (including radiographs) before starting orthodontics to help us plan and monitor the treatment. Nasal septum deviations (among others) are not what we are looking for and do not change our treatment plan. We can also make full body scan and find even more IF’s, would that be positive?
    We teach our students at ACTA in the CBCT courses: try to avoid non-dental IF by correct collimation! At first this sounds weird, but it has many benefits: less anxiety, less diagosing in areas you are unfamiliar with, less referals of images and patients to radiologists and ENT specialists, and lower health care costs. Almost never are non-dental IF in the end beneficial to patients.
    About dose: ultra-low dose protocols deliver images with low disgnotic quality because of large voxelsize and low SNR. Their dose is presented as comparable to conventional as a result of using unrealistically high dose for conventional images, which is apples and oranges. Well collimated pan and ceph with modern equipment give a higher diagnostic yield for lower radiation dose (7 to 12 microSv) compared to large field low dose CBCT. Also: they prevent unnecessary non-dental IF.
    Disclosure: Owner of GentleCeph.

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    I read an article in AJO -DO (Impact of CBCT on orthodontic diagnosis and treatment planning ) by Hodges et.al
    2013 they showed orthodontists( n= 24) full records of different malocclusions asked them for a treatment plan then later added the CBCT and noted if there were changes in the treatment plan .Results showed there were 28 changes in treatment plan after viewing CBCT

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    Dear Kevin,
    We published some work in this area in 2014 titled “Clinical importance of incidental findings reported on small-volume dental cone beam computed tomography scans focused on impacted maxillary canine teeth”. We reviewed the radiology reports that were prepared by specialists in dental and maxillofacial radiology, classifying the incidental findings as either a) anatomic variant/low-grade importance, b) intermediate grade (follow-up required) and c) high-grade importance (requiring immediate attention). Of 183 patients who had CBCT exams towards their impacted maxillary canines, there were 340 incidental findings reported that we categorised into 40 different types, of which 0.3% were high-grade, 28.5% intermediate and 71.1% low-grade/anatomic variant.
    Our article can be accessed at DOI: 10.1016/j.oooo.2014.09.006
    I hope this will be helpful for the community and the ongoing discussion regarding what to do if/when one encounters an incidental finding.
    Best wishes,

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