Dose Reduction by Field of View Optimisation in Cone-Beam Computed Tomography of Unilateral Alveolar Clefts.

Objective: This study aimed to investigate how much the field of view (FOV) can be decreased while still depicting the necessary anatomical structures. A secondary aim was to assess how many incidental findings were missed with a reduced FOV.

Material and methods: In this retrospective study, 170 CBCT volumes from children with a mean age of 9.4 years were collected. All CBCT had a FOV of 80 × 50 mm covering the maxilla. The present study analysed whether a smaller FOV can be used while still including necessary anatomical structures. Measurements of the minimal height and width that include vital anatomical structures were performed with two FOV reduction protocols: one smaller (includes the cleft, adjacent central incisor and adjacent canine) and one larger (includes both canines, nasal floor and the cleft).

Results: The use of the larger protocol resulted in a FOV of 44.3 × 36.5 mm (95th percentile); for the smaller protocol, the FOV was 28.1 × 34.9 mm (95th percentile). In the larger protocol, incidental findings were missed in 22%. In the smaller protocol, 35% of the incidental findings were missed. However, most of these findings were irrelevant to the planning of the bone graft.

Conclusion: A FOV of 50 × 40 mm (41% dose reduction compared with the original FOV) is suggested to fully depict the cleft area, central incisors, nasal floor and both canines. A FOV of 35 × 40 mm (56% dose reduction compared with the original FOV) is suggested to depict the cleft and the ipsilateral canine and central incisor adjacent to the cleft.