gms | German Medical Science

Introduction: Cone beam tomography (CBT) has become more common in diagnostics of diseases of ENT. Especially in diseases of the temporal bone and the anterior skull base the advantage of CBT could be evaluated [1], [2].

Material/Methods: Between 2002 and 2011 about 4500 CBT were performed. These images were critical analysed weather the imaging could answer the questions on it. So the limits of CBT can be demonstrated.

Results and discussion: First limit is the patient itself. For young patients (normally below 5 years), old patients and uncooperative patients it is difficult to sit in a quiet position for 8.5 up to 17s. This can result in artifacts with the impossibility to detect pathological findings.

Second limit are artifacts. CBT is an artifact arm but not artifact free method. Magnets or huge metal parts (e.g. bed of implant in case of cochlear implants) lead sometimes to a bad quality of the images.

Third, user dependent mistakes (wrong tube current, wrong tube voltage, wrong size of image) can result in quality of the images with the impossibility of detecting the correct diagnosis.

Fourth limit are some indications. For example imaging of “Friedrich prosthesis” or the larynx itself are not classical indication of CBT. Similarly the cervical spine and the functional imaging of the nasolacrimal duct have no standard indication to perform a CBT. Especially the last fact show limits of the CBT. It is a high contrast method and has no chance to answer special questions on soft tissues. It consequently allows a save detection only of bony structures. The resolution of CBT is quite better than of Computed tomography (CT) but it is not good enough to answer questions of extreme thin structures (e.g. bony wall of facial nerve in the middle ear, medial and apical turn of the cochlear) [3].

Classic and good indications for CBT are the diagnostics of chronic rhinosinusitis, chronic otitis media and in preoperative planning of implants in anterior and lateral skull base. Especially in preoperative planning of cochlear implantation in hearing preservation it is a fantastic tool for evaluation of the needed length of the electrode. Also in planning reconstruction of mid-face in traumatology it is a usefull tool. The possibility of intraoperative use, realize a direct control of the implants in anterior and lateral skull base.

Overall, CBT has many indications in diagnostics of diseases of the ENT. The exact differentiation between CBT and CT in dependence of the indication has to be shown by significant studies in future.