CT examinations were performed using a 64-detector CT scanner (GE Revolution EVO 64; GE Healthcare, Milwaukee, WI, USA). The standard CT protocol for orbit examinations included scanning fields from the hard palate level to the level superior to the frontal sinuses. The patients were examined in the supine position. Scanning parameters included 120 kV and 220 mA, with an X-ray tube rotation of 0.33 s and slice thickness of 0.625 mm. After the software reconstruction of CT scans, all datasets were transferred and processed in 2-dimensional (2D) and 3D projections on a diagnostic workstation (Advantage Workstation 4.7; GE Healthcare, Milwaukee, WI, USA) using AW Volume Share 7 software (General Electric Company, Waukesha, WI, USA). Then, postprocessing techniques of 3D volume rendering and multiplanar reconstruction were used. A multiplanar analysis was conducted in the coronal, sagittal, and axial planes.
All the volumetric measurements were semi-automatically conducted. First, manual segmentation was performed by using a freehand drawing cursor region of interest in the axial plane by an experienced radiologist. Next, the isolated regions were visually inspected and manually adjusted. Segmented orbital contours were reconstructed as 3D images, and orbital volumes were automatically calculated. All measurements were evaluated 3 times by one radiologist, and the arithmetical value was estimated to reduce the measurement error. The anterior orbital border was defined as a line connecting medial and lateral orbital rims, while the posterior orbital border was defined as the orbital apex. A CT examination was used for the volumetric measurement of the fractured and non-fractured (contralateral) orbit before and 6 months after the surgical procedure. In addition, we preoperatively observed the location of orbital floor fractures, incarceration of orbital soft tissue, and extraocular muscles. Orbital implant position and the effect of orbital wall reconstruction were evaluated after surgery.
A CT examination was used for volumetric measurement of the fractured and contralateral (uninjured) orbit before and after the surgical procedure. The calculation formula for orbital volume ratio is: orbital volume ratio (OVR)=(1-(A-B/B))×100% (A: volume of fractured orbit after surgery; B: volume of contralateral [uninjured] orbit).
In the situation when the volume of the fractured orbit after surgery is equal to that of the uninjured orbit, the OVR is 100%. When the volume of the fractured orbit after surgery is 20% greater than that of the uninjured orbit, the OVR is 80%.
All the volumetric measurements were semi-automatically conducted. First, manual segmentation was performed by using a freehand drawing cursor region of interest in the axial plane by an experienced radiologist. Next, the isolated regions were visually inspected and manually adjusted. Segmented orbital contours were reconstructed as 3D images, and orbital volumes were automatically calculated. All measurements were evaluated 3 times by one radiologist, and the arithmetical value was estimated to reduce the measurement error. The anterior orbital border was defined as a line connecting medial and lateral orbital rims, while the posterior orbital border was defined as the orbital apex. A CT examination was used for the volumetric measurement of the fractured and non-fractured (contralateral) orbit before and 6 months after the surgical procedure. In addition, we preoperatively observed the location of orbital floor fractures, incarceration of orbital soft tissue, and extraocular muscles. Orbital implant position and the effect of orbital wall reconstruction were evaluated after surgery.
A CT examination was used for volumetric measurement of the fractured and contralateral (uninjured) orbit before and after the surgical procedure. The calculation formula for orbital volume ratio is: orbital volume ratio (OVR)=(1-(A-B/B))×100% (A: volume of fractured orbit after surgery; B: volume of contralateral [uninjured] orbit).
In the situation when the volume of the fractured orbit after surgery is equal to that of the uninjured orbit, the OVR is 100%. When the volume of the fractured orbit after surgery is 20% greater than that of the uninjured orbit, the OVR is 80%.
