Use of hand-held laser scanning in the assessment of facial swelling: a preliminary study.

A new generation lightweight, hand-held, laser surface scanner (FastSCAN) was validated and clinically evaluated for the assessment of postoperative facial swelling. The potential sources of error-scanner error, registration error, and repositioning and movement error were established for laser scans of a mannequin head and seven volunteers. For the mannequin head the mean (S.D.) volume of the simulated swelling was 12.5 (0.5) cm3. The measurement error was therefore about 4%, and reflected the error in scanned data and in surface registration. Among the volunteers, repositioning of the head introduced additional errors of up to 7.6 cm3 (mean 1.8 cm3), illustrating the additional influence of variable positions. We then scanned 20 patients (9 women and 11 men, age range 18-26) before and 2 days after, third molar removal. The external, facial soft tissue volume changes were calculated for both left and right sides (range 0.2-64.3 cm3). The main source of inaccuracy was again variability of position. Despite this, the FastSCAN proved to be a simple, accurate, and non-invasive method of measuring postoperative changes in volume in the external, soft tissues of the face. Minimising variability in position by using more precise positioning techniques will increase the accuracy of this technique and is a focus for future work.