ABSTRACT
Purpose: Anterior segment optical coherence tomography (AS?OCT) by a swept source can visualize the ciliary body. The study was performed for analyzing the feasibility of a new swept?source OCT (Anterion) device for measuring iris ciliary sulcus, ciliary body thickness, and iris thickness. Methods: It is a pilot study among 30 normal young participants and hospital employees with their consent. The ciliary body, iris thickness, and ciliary sulcus were measured and compared to the results in the literature. We obtained 28 good?quality results. The main outcome measures were iris thickness (near and away from the pupillary margin), ciliary body thickness, and iridociliary sulcus measurement. Results: The iris thickness 2.5 mm from the pupillary margin was 0.70 ± 0.10 mm in the right eye and 0.68 ± 0.11 in the left eye. Closer to the root, the iris thickness varied from 0.55 ± 0.16 mm (right eye) and 0.57 ± 0.12 (left eye). Ciliary body thickness: Right eye 0.59 ± 0.14mm (28 good images), left eye 0.58 ± 0.13mm; ciliary sulcus (inner angle): right eye 82.65 ± 26.6°, left eye 83.66 ± 30.1°. Conclusion: Anterion OCT is feasible in our setting for various measurements and can provide valuable inputs to ophthalmologists for the treatment of ocular diseases.
ABSTRACT
Objective: Chemoradiation therapy is among the standard treatments for cancer, which often causes a decrease in appetite and subsequent weight loss. When weight loss occurs during treatment, the external body contour changes from that indicated during initial planning, causing changes in dose distribution to the target tumor regions and organs at risk (OARs). This study aimed to examine the dose changes to both the target regions and OARs, based on the dose-volume histogram (DVH).Methods: We established a 60 mm-diameter planning target volume (PTV) and a 30 mm-diameter rectum region of interest (OAR), using a phantom; this was followed by a 50 Gy/25 fraction irradiation to the target region that was measured using a two-dimensional-array ion chamber device. The measurement was conducted by varying the bolus thickness from 0 to −25 mm, in 5 mm decrements. In addition, the maximum dose for both PTV and OAR were evaluated based on the DVH, created using the Adaptive software.Results: The gamma analysis showed that the pass rate was less than 95% when the bolus thickness was altered by −25 mm for the helical delivery mode and by −10 mm for the direct delivery mode, resulting in a dose error greater than 3%. Results of the DVH evaluation revealed that the maximum dose of PTV increased by 5.18% when the bolus thickness was −25 mm for helical delivery, whereas a 9.95% increase was noted for the direct delivery mode compared with the dose at the reference level of 0 mm bolus thickness.Discussion: Our results suggest that it is necessary to formulate a new treatment plan owing to increased dose error, if the body thickness decreases by more than 20 mm and 10 mm for the helical and direct delivery modes, respectively. The results also demonstrate that helical delivery is less affected by changes in body thickness than direct delivery.