# Breast Geometry Characterization of Young American Females Using 3D Image Analysis
## 2 Materials and Methods
### 3D Image Analysis  
After screening the SizeUSA database, 156 scan files were imported to a 3D image analysis tool, GeoMagic Design X (3D System), and processed to extract the breast measurements. The basic reference points were defined, and they are summarized in Table 3. A bust point (BP) was located after a visual assessment of the most prominent point of the breast. An inner bust point (IBP) was declared as an additional important reference for the further investigation of breast geometry, which was the bust point projected on the breast base (Figure 1). The breast base was placed along the ribcage that separated the breast cup from the body. The body center point (BCP) was defined as the sagittal/transverse midpoint of a body at the BP level. The upper, lower, inner, and outer points of the breast (UPB, LPB, IPB, OPB) were located to define the breast boundary. The procedures to identify the reference points are as follows. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**678 White Females**} & \multicolumn{2}{c}{**298 White Females**} & \multicolumn{2}{c}{**156 White Females**} \\ \cline{2-7}  & **Mean** & **st.dev.** & **Mean** & **st.dev.** & **Mean** & **st.dev.** \\ \hline height (cm) & 164.70 & \(\pm\)6.54 & 164.57 & \(\pm\)6.34 & 162.93 & \(\pm\)5.56 \\ weight (kg) & 70.01 & \(\pm\)18.15 & 66.37 & \(\pm\)8.38 & 65.56 & \(\pm\)7.87 \\ bust girth (cm) & 101.88 & \(\pm\)13.08 & 99.80 & \(\pm\)6.02 & 99.23 & \(\pm\)5.93 \\ waist girth (cm) & 85.12 & \(\pm\)14.01 & 82.35 & \(\pm\)6.38 & 82.40 & \(\pm\)6.16 \\ upper body length (cm) & 40.24 & \(\pm\)2.79 & 40.21 & \(\pm\)1.46 & 40.17 & \(\pm\)1.49 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Descriptive summary of body builds in the age of 26–35. IPB and OPB were placed first at the BP level after reviewing the cross-sectional body contour along the transversal plane (Figure 1). The inner bust point (IBP) was located on the line connecting IPB and OPB, where the normal line from BP landed. Based on this line, the transversal plane at the BP level was rotated every 30\({}^{\circ}\), and 12 radial lines were formed around the BP where the body mesh met each rotated plane (Figure 2). Twelve breast boundary points were located on each radial line after reviewing its shape, where the curvature of the breast cup started to dim. Four major boundary points were named UPB, IPB, LPB, and OPB in 1  
The breast-specific measurements were extracted based on those reference points, lines, and planes. The total number of measurements was as many as 39 (Table 4), including various lengths, angles, areas, and volumes. The length measurements were either contour lengths measured along the meshes or linear lengths across the space. Breast depth was the distance between BP and IBP, and body depth was defined between BP and BCP (Figure 4). Several measurements were converted into ratios when proportions were considered more meaningful than absolute dimensions because some dimensions were substantially dependent on breast size or body build. For example, the distances between BP and shoulder points were divided by the upper body length and expressed as percentages.