Journal of Dental Medicine

---

Concern for adverse effects must accompany any use of ionizing radiation. Such concern for the expanded use of CT scanning, conventional tomography and panoramic in dental implant radiology can be expressed by the establishment of absorbed radiation dose for critical tissues (resulting from these radiographic procedures). Potential patient benefit should be weighted against the risk and other disadvantages and/or advantages of a particular radiographic imaging technique. Measurement of dose values can act as a guidline for such risk determinations. The purpose of this study was to measure and compare the absorbed doses of various anatomic sites during these radiographic techniques. The absorbed radiation doses in bone marrow, thyroid gland, salivary gland, eye, brain and skin entrance were determined by placement of lithium fluoride thermoluminescent dosimetres (TLD, S) at selected anatomic sites within and on a humanlike x-ray phantom. The phantom was exposed to radiation from panoramic, linear tomographic and computer- assisted tomographic (CT) stimulated dental implant radiographic examinations. The mean dose was determined for each anatomic site. CT examination showed disruption dose, while panoramic radiography was generally the lowest. The mean absorption value by paratid gland was higher than of other salivary glands.

---

Background and Aim: The objective of this study was to measure and compare the tissue absorbed dose in thyroid gland, salivary glands, eye and skin in maxillofacial imaging with panoramic, conventional linear tomography, cone beam computed tomography (CBCT) and computed tomography (CT).
Materials and Methods: Thermoluminescent dosimeters (TLD) were implanted in 14 sites of RANDO phantom to measure average tissue absorbed dose in thyroid gland, parotid glands, submandibular glands, sublingual gland, lenses and buccal skin. The Promax (PLANMECA, Helsinki, Finland) unit was selected for Panoramic, conventional linear tomography and cone beam computed tomography examinations and spiral Hispeed/Fxi (General Electric,USA) was selected for CT examination. The average tissue absorbed doses were used for the calculation of the equivalent and effective doses in each organ.
Results: The average absorbed dose for Panoramic ranged from 0.038 mGY (Buccal skin) to 0.308 mGY (submandibular gland), linear tomography ranged from 0.048 mGY (Lens) to 0.510 mGY (submandibular gland),CBCT ranged from 0.322 mGY (thyroid glad) to 1.144 mGY (Parotid gland) and in CT ranged from 2.495 mGY (sublingual gland) to 3.424 mGY (submandibular gland). Total effective dose in CBCT is 5 times greater than Panoramic and 4 times greater than linear tomography, and in CT, 30 and 22 times greater than Panoramic and linear tomography, respectively. Total effective dose in CT is 6 times greater than CBCT.
Conclusion: For obtaining 3-dimensional (3D) information in maxillofacial region, CBCT delivers the lower dose than CT, and should be preferred over a medical CT imaging. Furthermore, during maxillofacial imaging, salivary glands receive the highest dose of radiation.

---

Background and Aims: The evaluation of absorbed dose received by patients could give useful information for radiation risk estimation. This study was performed to compare the entrance skin dose received by patients in cone beam computed tomography (CBCT), conventional and spiral computed tomography (CT).
Materials and Methods: In this experimental study, 81 calibrated TLD chips were used. the TLD chips were placed on facial, thyroid and end of sternum skin surface in patients referred for CT of the paranasal sinuses (3 TLD chips for each area) to estimate the absorbed dose received by central part of radiation field, thyroid and out of field areas, respectively. The data were analyzed using one-way ANOVA and Tukey tests.
Results: The dose delivered to the center of irradiated field was about 0.79±0.09 mGy in CBCT technique compared with 16.31±3.71 and 18.84±4.12 mGy for spiral and conventional CT, respectively. The received dose by the out of field areas was about 54 percent of central area dose. There was statistical significant relationship between the imaging modalities and absorbed dose received by patients (P=0.016). The least absorbed dose was for CBCT and the greatest dose was for conventional CT imaging technique.
Conclusion: The dose delivered to central area of irradiated field in conventional and spiral CT imaging modalities was about 24 times greater than of that in CBCT. Also, the highest received dose was for central area of radiated field and the lowest dose was for the out of field areas.