3D Cone Beam Ct Scan (CBCT)
Getting More with Less: A Discussion of Cone-Beam and Radiographic Imaging
There’s a good chance that your doctor will need to obtain one or more x-rays of your jaw, teeth, or facial skeleton (and/or associated soft tissue structures) at some point during the diagnostic evaluation (or workup) of your condition, or during treatment or follow-up of your condition.
Often times films ( or copies of films) from your referring dentist can be utilized without the need for additional imaging; however, please be aware many times these film images are of inadequate orientation or quality (particularly when an image has been transferred to paper) and critical areas of anatomy cannot always be discerned adequately in order to make an informed decision (transferring radiographic data from electronic media to paper can result in significant loss of image resolution and clarity). In these cases, a new image in our office is typically obtained.
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Various types of films/images obtained for evaluation of Oral & Maxillofacial conditions:
Periapical (PA) films– (2-Dimensional) commonly obtained in a general dentist’s office; these films provide high detail for very small anatomic regions (and are typically used to evaluate individual teeth or structures surrounding teeth).
Panoramic films– (2-Dimensional)-essentially, a tomogram of the facial skeleton; this is the workhorse film within our specialty, as multiple anatomic regions can be evaluated in one film. Often considered a screening film, this film is essentially an extended tomogram or slice of the jaws and may provide adequate visualization of structures with the jaws. 3-Dimensional relationships (i.e. structures in front of or behind the chosen slice); however, cannot be discerned with this film (additional imaging modalities are used for this purpose).
Tomographic films– (2 Dimensional)-used for evaluating varying slices of the anatomy.
Typically used for Temporomandibular Joint evaluation or evaluation of selected regions of the facial skeletal anatomy, newer cone-beam technology incorporates tomographic sliding in a digital manner.
Cephalometric films-(lateral/AP/Waters/Townes)– (2-Dimensional)-these films are obtained when the need exists to evaluate larger areas of the facial skeleton and are commonly used for planning major facial skeletal surgery, lateral upper airway evaluation, and facial skeletal asymmetries.
Medical Grade CT scans – (2-Dimensional, with 3-Dimensional reformatted capability)-these images are obtained when understanding of 3-dimensional hard and soft tissue anatomy is required. Typically obtained in a hospital or free-standing imaging center, these images must be transferred back to our office for reading by the surgeon prior to proceeding with needed therapy. When planning for dental implant placement, CT scan images can be transferred into third-party software in order to allow the surgeon completes visualization of the planned surgical site and virtual implant treatment planning. Anatomically accurate models of a patient’s anatomy can be generated from the data obtained with this modality, however, the amount of radiation imparted from these scans is quite high (these scans subject the patient to 200-300 times the radiation required for panoramic radiography. When both jaws need to be scanned, the patient is collectively receiving 400-600 times the radiation dose compared to a panoramic radiograph).
Cone-Beam CT scans– (2 and 3-Dimensional)-representing a new imaging modality, these scanners allow excellent visualization of facial skeletal anatomy but at significantly lower radiation dosages than medical-grade CT scanners (these scanners are not as good as medical-grade scanners at providing an evaluation of soft tissue anatomy). The amount of radiation imparted to the patient by some cone beam scanners is very similar to that imparted by a traditional panoramic film. All of the above types of films (excluding medical grade CT scans) can be obtained with this modality (and indeed with time, cone-beam scans may supplant the use of these modalities). As the voxel size with these scanners is quite small, the accuracy of these images is superior to medical-grade scanners (accuracy with a cone-beam scan is within one-tenth of a millimeter (0.1mm) while medical CT scanners are off by 0.5mm or more).
What type of image will I have during my appointment?:
While individual problems are present by each patient, most patients will benefit from a traditional panoramic (the exact type of image will be determined based upon your presenting clinical problem). Traditional Panoramic films are used most often for obtaining screening views of the upper and lower jaw prior to performing wisdom tooth removal or for evaluation of other problems related to the jaws (including placement of dental implants). Panorex images allow obtaining a large amount of clinical information for relatively low radiation dosage to the patient.
Problematic, however: the Panorex is a 2-dimensional image while the jaws and facial skeleton are 3-dimensional structures-therefore, the Panorex is unable to provide all the information sometimes required (as determined by your surgeon).
As a commonly encountered example, the anatomic course of the inferior alveolar nerve (and its relation to the roots of the wisdom teeth) is an important consideration during the evaluation process of wisdom tooth surgery; its relation to areas of the lower jaw in cases of implant planning is also critical. In addition, the evaluation of sinus anatomy (in relation to the upper jaw bone) is often less than ideal with a Panorex.
More specific detail of individual teeth has been obtained historically by use of periapical (dental) films-these, however, can be difficult to place in certain needed regions of the oral cavity-and don’t provide all the information sometimes required.
In cases where more critical 3-dimensional information is required (as in determining specific nerve/root relationships, sinus anatomy, or critical evaluation of available bone prior to implant placement), a CT scan is often beneficial in helping discern critical anatomy.
Historically, patients requiring a CT scan have been sent out to a third-party office (either hospital or imaging center) for obtaining the medical-grade CT scan. There are, however, important issues to consider with Medical-Grade CT scans:
Radiation– per above-significantly higher dosages of radiation are received by the patient; a recent review of this topic in the Journal of the American Medical Association warns of the long-term risks to patients as a result of the cumulative effects of radiation received from these types of scans.
Costs– the costs for these scans run generally between $450-600. If the scan is being obtained for a well-documented medical purpose (as opposed to dental purpose-as determined by a patient’s medical insurance company), the costs for the scan are generally covered, excluding co-pays. When a scan is determined to be for a dental purpose, a patient’s medical plan will generally not provide coverage for the scan.
Inconvenience– a patient must be sent to either a hospital or imaging center in order to have these scans performed. Transference of the collected imaging data back to our office must then be performed (ideally, this data should be transferred in an electronic manner, so that the evaluating surgeon can manipulate the data to his advantage in assessing the clinical situation). Oftentimes, however, copies of the images are printed onto celluloid film which the patient brings back to the doctor (these images, however, cannot be easily reconstructed into 3-film Dimensional data).
Third-party Applications– often the surgeon will need to have the data collected from a CT scan to be transferred into a third-party treatment planning application in order to allow virtual surgical planning (commonly performed when placing dental implants). In order for this to occur, the third-party software company often charges the patient a reformatting fee (which can be as much as $200-300) and which is not covered by insurance.
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Comparisons of Medical Grade CT Scans to Cone Beam 3-D Technology:
There are multiple advantages of Cone-Beam Technology (as applies to facial skeletal imaging) compared with medical-grade CT scans:
- Significantly lower dosages of radiation are delivered to the patient by Cone-Beam CT scans. The dosage of radiation received with certain types of Cone-Beam scans is only slightly higher than that obtained with a Panorex film.
- Convenience-these scans can be obtained while in the Oral Surgeon‘s office, thereby eliminating the need for transport of the patient to a hospital or imaging center. As the images are generated within several minutes, there is no delay to the patient or surgeon in obtaining the images.
- Multiple anatomic regions can be assessed 3-dimensionally in one scan-eliminating the need for multiple PA and/or panoramic (or tomographic) images. Both upper and lower jaws are scanned at the time, eliminating the need for additional exposures.
- Lower costs to the patient-reformatting of data are eliminated with certain cone-beam technologies, eliminating these out-of-pocket costs for patients.
- Accuracy-as mentioned above, due to the small voxel size of this modality, accuracy is generally stated to be within 0.1mm superior to that of medical-grade scans.
Does Insurance coverage for Cone-beam CT imaging exist?
Oftentimes, when patients were sent out for a medical-grade CT scan (assuming they were being sent for a dental problem), the costs of the CT scan would NOT be covered by the medical insurance company. Occasionally, when the diagnosis is deemed to be medically related, a medical insurance company typically does provide insurance coverage for these scans (not including patient co-pay).
Most of the scans we obtain, however, are for dental purposes, not medical; hence, medical insurance typically will NOT provide coverage for these scans.
At the same time, new insurance codes for cone-beam CT scans have recently been developed within the dental insurance industry. The dental industry is slowly adapting to provide coverage for cone-beam scans (coverage for this procedure can be determined by you calling your insurance company to check the details of your individual plan). Problematic, however: most dental insurances only provide $1,000.00-2,000.00 of coverage/benefits for an individual for a given year (this includes all dental care). These costs, considering all of one’s dental care for a given year, can be quickly consumed. Costs beyond the stated level of benefits become the responsibility of the patient.
Dilemma! Do I need a Panorex, PA film, or Cone-Beam Scan (or some combination of these)?
Goal: It is the desire of our Oral Surgery practice to obtain the highest quality needed clinical/radiographic data in the safest manner (lowest radiation dose) and the lowest cost to the patient. Having stated this, please understand the following factors:
- Individual anatomy varies from person to person
- There exists a Cost/Benefit ratio(in other words, we want to obtain maximum benefit for the lowest cost)
- The Cone beam scan is more expensive than screening panoramic view (cost for a cone beam scan is $450 in our office, versus the panoramic view-costing approximately $150)-but the cone beam scan provides a vastly larger amount of clinical data upon which to make a clinical decision.
- Most patients will benefit from an initial screening panoramic film; in situations where the anatomy suggested from this film is uncomplicated, these may be the only images required.
- Some patients, however, based upon the information obtained from the panoramic film, will then benefit from an additional cone beam scan in order to discern more detail of areas of concern noted on the Panorex- but the costs are additive!
- Some patients should (or may choose to) proceed directly with a cone beam scan- i.e. skip the Panorex: i.e. implant patients, patients with complex facial skeletal problems, bone tumors, patients in whom a previous film has suggested close root/nerve anatomy or patients who simply choose to proceed directly to cone beam scan (again, radiation dose with a cone beam scan is just slightly higher than a panoramic film).
- Some patients may choose to proceed directly with a cone beam scan and skip the Panorex film. Given the current capabilities and low dosage of cone beam technology, this is a reasonable option.
Our practice has made an investment in providing the convenience and safety of digital cone beam imaging directly in our office to you.
We have chosen to utilize the Kodak CS 9300 cone beam scanner. This unit provides one of the lowest dosage radiation exposure of any unit currently on the market, with the best-rated quality images being provided (this rating having been performed by independent maxillofacial radiologists). The images are obtained within a matter of minutes and can be transferred into bundled treatment planning software or other software at minimal, if any, costs.
While we understand that these issues may sound somewhat complicated, we do feel it is important for those patients who have questions related to their unique imaging needs to be aware of the issues involved in the decision-making process. Please don’t hesitate to discuss your individual situation with your surgeon.