Abstract
Objectives: Technical innovations in radiography enable the development of
new approaches to reduce the dose to patients. The aim of this thesis
was to explore dose optimization approaches for the most frequently
used radiographic modalities in dentistry.
Material and Methods. Intraoral radiography: The performance of the Automatic exposure control function (AEC)
was tested on dry mandibles with soft tissue equivalent of different
thicknesses. Furthermore the image quality was compared between
images exposed manually and with AEC function.
Two different generations of direct digital intraoral sensors, based
on charged couple device (CCD) and complementary metal oxide
semi-conductor (CMOS) were compared in terms of dose response
function, minimal perceptible contrast details and minimal
perceptible exposure difference.
Panoramic radiography: Effective doses obtained from panoramic examinations with ten
different collimation features were assessed using the metal-oxide
semiconductor field-effect transistor (MOSFET) method. In
addition, the applicability of the collimation function under clinical
situations was evaluated.
Cone Beam Computed Tomography: Optimized exposure protocols for temporomandibular joint (TMJ)
examinations on a phantom were obtained for CBCT and MSCT
through subjective image quality analysis. Effective doses, before
and after, optimization were compared for CBCT and MSCT using
thermoluminescent dosimeter (TLD) technique.
Results: The exposure times using AEC were adjusted automatically
according to the thickness of the objects and the resulting image
quality was considered adequate by observers. The CMOS sensor
was more sensitive to radiation and presented better image quality
on low contrast details perception compared to the CCD sensor.
The calculated effective dose of a full size panoramic radiograph
was 17.6 μSv at 8mA and 66kV. In 61% of the studied referrals, a
collimation including the dental alveolar region was applicable,
providing a dose reduction by 40.3%.
The effective doses for bilateral TMJ examination was 92 μSv for
CBCT and 124 μSv for MSCT. The image quality of CBCT was
considered better than that of MSCT.
Conclusions: AEC might be a feasible approach for acquiring intraoral digital
radiographs with good image quality. ProSensor with CMOS
technique was preferred in comparison to Dixi sensor with CCD
technique due to lower exposure and better detectability of low
contrast details.
Collimating panoramic radiographs was an effective approach to
reduce radiation dose to patients when clinical indication allowed.
For TMJ examination CBCT was preferred to MSCT due to better
image quality at comparable effective doses.