| Objective:(1)To study the patients’ radiation dose in the different field of view(FOV)of oral and maxillofacial cone beam CT in oral clinic.(2)According to the radiation dose limits prescribed by the International Commission on Radiological Protection(ICRP),to specified the number of scans that can be performed by the patient in different views of the oral and maxillofacial cone beam CT.Methods:Seven non-target sensitive organs in the emulated radiometric head module were selected.The thermoluminescent chips were placed on the set of the seven sensitive organs and scanned under the six different field of views of the NewTom VGi CBCT respectively.Calculated the absorption dose(DT),equivalent dose(HT),effective dose(E)and analyzed the results.Results:(1)The average absorbed dose in 12cm*8cm scanning field with the high resolution are the highest(4.85mGy)and the average absorbed dose in the 8cm*8cm scanning field with the standard resolution are the lowest(1.23mGy),the highest dose of the lowest dose were about 4 times.(2)After scanning the six fields of view,there was a significant difference between every two groups in radiation dose(P<0.05)(3)Under the same resolution,the absorptive dose increased with the increase of the scanning field,and the amount of absorbent after high resolution scanning was higher than the standard resolution under the same scanning field.The radiation dose after scanning of different organs and tissues was positively correlated with the sensitivity of the tissue and the range and resolution of the radiation field.(4)The different tissues or organs received different doses of radiation after scanning in the same view domain while the radiation doses of the same tissue or organ was different after scanning in different view fieldsConclusions:(1)New TomVGi oral and maxillofacial cone-beam CT has a large difference in radiation dose in different view fields.the appropriate view field should be selected according to the patient’s clinical needs,so as to reduce unnecessary radiation dose during medical imaging examination.(2)The equivalent dose of the ophthalmic len absorbed dose in 15cm*15cm scanning field with the normal resolution are the highest was 2.85mSv.According to recommendation issued by ICRP,the annual dose of the lens was not more than 50mSv,and in that FOV the annual irradiation explore was limited to 17times. |
