Diagnostic radiology has undergone profound changes in the last 30 years. New technologies are available
to the dental field, cone beam computed tomography (CBCT) as one of the most important. CBCT is
a catch-all term for a technology comprising a variety of machines differing in many respects: patient
positioning, volume size (FOV), radiation quality, image capturing and reconstruction, image resolution
and radiation dose. When new technology is introduced one must make sure that diagnostic accuracy
is better or at least as good as the one it can be expected to replace. The CBCT brand tested was two
versions of Accuitomo (Morita, Japan): 3D Accuitomo with an image intensifier as detector, FOV 3 cm
x 4 cm and 3D Accuitomo FPD with a flat panel detector, FOVs 4 cm x 4 cm and 6 cm x 6 cm.
The 3D Accuitomo was compared with intra-oral radiography for endodontic diagnosis in 35 patients
with 46 teeth analyzed, of which 41 were endodontically treated. Three observers assessed the images by
consensus. The result showed that CBCT imaging was superior with a higher number of teeth diagnosed
with periapical lesions (42 vs 32 teeth).
When evaluating 3D Accuitomo examinations in the posterior mandible in 30 patients, visibility of
marginal bone crest and mandibular canal, important anatomic structures for implant planning, was
high with good observer agreement among seven observers.
Radiographic techniques have to be evaluated concerning radiation dose, which requires well-defined
and easy-to-use methods. Two methods: CT dose index (CTDI), prevailing method for CT units, and
dose-area product (DAP) were evaluated for calculating effective dose (E) for both units. An asymmetric
dose distribution was revealed when a clinical situation was simulated. Hence, the CTDI method was not
applicable for these units with small FOVs. Based on DAP values from 90 patient examinations effective
dose was estimated for three diagnostic tasks: implant planning in posterior mandible and examinations
of impacted lower third molars and retained upper cuspids. It varied between 11-77 μSv.
Radiation dose should be evaluated together with image quality. Images of a skull phantom were obtained
with both units varying tube voltage, tube current, degree of rotation and FOVs. Seven observers assessed
subjective image quality using a six-point rating scale for two diagnostic tasks: periapical diagnosis and
implant planning in the posterior part of the jaws. Intra-observer agreement was good and inter-observer
agreement moderate. Periapical diagnosis was found to, regardless of jaw, require higher exposure
parameters compared to implant planning. Implant planning in the lower jaw required higher exposure
parameters compared to upper jaw. Substantial dose reduction could be made without loss of diagnostic
information by using a rotation of 180°, in particular implant planning in upper jaw.
CBCT with small FOVs was found to be well-suited for periapical diagnosis and implant planning.
The CTDI method is not applicable estimating effective dose for these units. Based on DAP values
effective dose varied between 11-77 μSv (ICRP 60, 1991) in a retrospectively selected patient material.
Adaptation of exposure parameters to diagnostic task can give substantial dose reduction