Measuring Differential Volume Using the Subtraction Tool for Three-Dimensional Breast Volumetry: A Proof of Concept Study

Abstract

Background. Three-dimensional (3D) photography provides a promising means of breast volumetry. Sources of error using a single-captured surface to calculate breast volume include inaccurate designation of breast boundaries and prediction of the invisible chest wall generated by computer software. An alternative approach is to measure differential volume using subtraction of 2 captured surfaces. Objectives. To explore 3D breast volumetry using the subtraction of superimposed images to calculate differential volume. To assess optimal patient positioning for accurate volumetric assessment. Methods. Known volumes of breast enhancers simulated volumetric changes to the breast (n = 12). 3D photographs were taken (3dMDtorso) with the subject positioned upright at 90° and posteriorly inclined at 30°. Patient position, breathing, distance and camera calibration were standardised. Volumetric analysis was performed using 3dMDvultus software. Results. A statistically significant difference was found between actual volume and measured volumes with subjects positioned at 90° ( P < .05). No statistical difference was found at 30° ( P = .078), but subsequent Bland–Altman analysis showed evidence of proportional bias ( P < .05). There was good correlation between measured and actual volumes in both positions (r = .77 and r = .85, respectively). Univariate analyses showed breast enhancer volumes of 195 mL and 295 mL to incur bias. The coefficient of variation was 5.76% for single observer analysis. Conclusion. Positioning the subject at a 30° posterior incline provides more accurate results from better exposure of the inferior breast. The subtraction tool is a novel method of measuring differential volume. Future studies should explore methodology for application into the clinical setting.

Challenges in developing a quantitative method of measuring breast development using 3D imaging: An example of a novel method for use in induced breast development with exogenous oestrogen

“…22 Anatomy and tissue definition may vary depending on patient positioning including sitting angle, head and arm placement and respiratory effort. 20,[22][23][24][25] Overlaying two static images of the same male subject taken on different occasions using a positioning protocol with a bespoke posture support resulted in minimal calculated differential volume, demonstrating that breast volume was not a consequence of artefact or positioning. Furthermore, the intraobserver reproducibility of this process and measurements calculated was reassuring suggesting that volume change was not examiner or measurement technique dependent.…”

“…Reproducibility of repeated imaging and measurements may be related to several factors including those related to subject and examiner 22 . Anatomy and tissue definition may vary depending on patient positioning including sitting angle, head and arm placement and respiratory effort 20,22–25 . Overlaying two static images of the same male subject taken on different occasions using a positioning protocol with a bespoke posture support resulted in minimal calculated differential volume, demonstrating that breast volume was not a consequence of artefact or positioning.…”

Reproducibility of Three-Dimensional Volumetric Measurement of Periocular Tumor Models

“…In previous studies, RMS threshold values equal to or less than 0.5 mm were described as the maximum clinically acceptable level of variation [ 16 ]. Therefore, we repeated the superimpositions and checked the alignment until RMS values in this range were obtained [ 17 , 18 ], thereby ensuring that the images were correctly superimposed (Fig. 2 B).…”

Investigation of Smallest Volume Difference Measurable Using 3D Imaging

“…However, there was good correlation between the actual volume and the volume computed from surface images at both angles, with r = 0.77 and r =0.85 for 90° and 30°, respectively. They recommend positioning the subject at 30° for determination of breast volume because it provides better exposure of the inferior breast [6].…”