Chairs:
madeleine rohlin
ralf schulze

181: PATIENT RADIATION DOSE IN ORTHODONTICS (PRADO)

R.C. Hoogeveen1, H. Abdelzahra1, E. Berkhout1

1ACTA Amsterdam, Oral Radiology, Amsterdam, Netherlands

Aim: to investigate the patient radiation dose during an episode of orthodontic treatment.

Methods: in 70 orthodontic clinics the number of X-ray exposures were retrieved for the year 2023, as well as the number of orthodontic treatment starts. These data were combined with the setting parameters of the exposures for every clinic. These parameters were linked to estimated effective patiënt dose. Average numbers of all types exposures per treatment were calculated per clinic and average effective patient dose per orthodontic treatment episode was calculated.

Results: 19532 treatmenst were commenced in 70 offices, which performed in total 52025 panoramic radiographs, 22442 lateral cephalograms, 11 PA cephalograms, 58 intra-oral radiogrpahs and 22 CBCT-scans. The average number of exposures per treatment was 2,76 panoramic radiographs (sd 0.75; range 0.92 – 4.93), 1.15 lateral cepaograms (sd 0.26; range 0.77 – 1.98). A variety of exposure settings was encountered resulting in a range of patient dose per exposure. Preliminary results indicate the average patient dose to be between 25 uSv and 100uSv per episode of orthodontic treatment.

Conclusions: Differences in number of exposures and exposure settings result in a large range in average patient dose during orthodontic treatment. Education and training and improvement of procedures could reduce the dose for the orthodontic patient in many of the participating offices.

192: ESTABLISHMENT OF DIAGNOSTIC REFERENCE LEVELS FOR DENTAL CONE BEAM CT IN GREECE

G. Manousaridis1, E. Carinou1, C.J. Hourdakis1

1Greek Atomic Energy Commission, Agia Paraskevi, Greece

Aim: This work aims to establish national Diagnostic Reference Levels (DRLs) for dental Cone Beam Computed Tomography (CBCT) in Greece.

Materials and Methods: An email survey was conducted, inviting all authorized parties with accessible email addresses to provide dose-related data from a minimum of 20 patients. The data collected included patient demographics (sex, age), referral indications selected from a predefined list, dose protocols utilized, field sizes, and reported Kerma Area Product (KAP). A total of 114 facilities responded, representing 120 CBCT scanners (50 in dental and 70 in radiology facilities), with data from 2928 patient scans.

Results: The 75th percentile values for each referral indication were successfully determined. Predominant referrals included multiple or single implant planning (40% and 17% of reported data, respectively) and impacted wisdom teeth (8%), with other indications ranging from 2% to 7%. A wide distribution of dosimetric data was observed, averaging 58%. The 75th percentile values for the most common examinations were determined as follows: 1165 mGycm2 for multiple implant planning, 923 mGycm2 for single implant planning, 897 mGycm2 for impacted wisdom teeth, and 983 mGycm2 for non-specific pathology investigation.

Conclusion: Diagnostic Reference Levels for the most common dental CBCT examinations have been established. The wide distribution in dose is likely due to the relatively recent adoption of dental CBCT as a modality. While international guidelines exist, further efforts are needed for their effective implementation.

204: CONVERTING DOSE-AREA PRODUCT TO EFFECTIVE DOSE IN CONE-BEAM CT USING ORGAN-SPECIFIC DEEP LEARNING

R. Pauwels1,2

1Aarhus University, Department of Dentistry and Oral Health, Aarhus, Denmark, 2Chulalongkorn University, Department of Radiology, Faculty of Dentistry, Bangkok, Thailand

Aim: To convert dose-area product (DAP) to effective dose (ED) for cone-beam computed tomography (CBCT) using deep learning.

Material and Methods: 24,384 CBCT exposures of an adult phantom were simulated using PCXMC 2.0 (STUK, Finland), using permutations of tube voltage, filtration, source-isocenter distance, beam width/height and isocenter position. Equivalent doses for each organ used in the ICRP 103 ED calculation as well as DAP values were recorded. Next, a series of dense neural networks (NN) were trained for each organ using Keras/TensorFlow. Two methods were explored: (1) ‘Coordinate’ mode, which uses the XYZ-coordinates of the isocenter; (2) ‘AP/JAW’ mode, which uses categorical codes for the anteroposterior (AP) and craniocaudal (JAW) position. For both methods, the six aforementioned scan parameters were used as inputs as well. Each network was trained, validated and tested using a 3/1/1 data split. ED/DAP was calculated from the NN outputs using ICRP 103 tissue weighting factors, and the accuracy was compared with that of a multiple linear regression (LR) model as well as direct conversion coefficients.

Results: The mean absolute error (MAE) for equivalent dose/DAP on the test data ranged from 0.18% (bone surface) to 2.90% (oesophagus) in ‘Coordinate’ mode and from 2.74% (red bone-marrow) to 14.13% (brain) in ‘AP/JAW’ mode. The MAE for ED was 0.23% and 4.30%, respectively, for the two modes, both of which outperformed the LR model (MAE: 5.70%) and conversion coefficients (MAE: 20.19%-32.67%).

Conclusion: NNs allow for a fast and accurate estimation of patient dose based on DAP in CBCT.

208: DO ALADA-DIP GUIDE OPERATORS IN CHOOSING THE CBCT PROTOCOL?

B. Roshihotzki1, L. Yeshurun1, T. Amiel1, C. Nadler1

1Hebrew University of Jerusalem, Hadassah Medical Center, Maxillofacial Imaging, Department of Oral Medicine, Sedation and Imaging, Jerusalem, Israel

Aim: Despite the existing radiation protection principles, guidelines are not available for the use of specific CBCT machines in particular diagnostic tasks. This study aimed to analyze the scan parameters used in our department, their correlation with patient age and reason for referral (RFR).

Materials and Methods: This retrospective study retrieved demographic data, scan protocols and radiation dose of CBCT scans performed from 2021 to 2022 for three indications: (1) impacted teeth, (2) bone lesions and (3) pre-implant evaluation. Demographic included patient age and RFR. Technical parameters included field of view (FOV), tube current, projection method, rotation type, exposure time, voxel size and dose-area-product (DAP). Statistical analysis aimed to identify correlation between technical parameters and patient age and specifically examine whether there is a specific age below which lower dose CBCT protocols are more commonly applied. It also compared the technical parameters and DAP for protocols frequently used in each RFR.

Results: The study evaluated 617 scans. Protocols with the same FOV, such as high-speed mode with full rotation and standard mode with half rotation, displayed similar DAP. Overall, DAP increased with the average age of patients, with those beyond their third decade of life more likely to receive higher radiation dose. The RFR also affected DAP, with the highest values observed in pre-implants bone assessment.

Conclusion: Patients in their first to third decades of life are more likely to be scanned with lower-dose protocols. Additional research is needed to determine whether common protocols with similar radiation doses differ in their image quality