Introduction/Background In this digital age, it is remarkable that the size of vulvar tumors is still measured with a ruler. Surface area can be estimated with an ellipse model (pi/4*height*width). These estimates have been used to assess the effectiveness of systemic treatments in reducing tumor size. Effects were considered relevant if tumor sizes decreased with >20%. However, measurement errors interfere with these results. The aim of this study is to compare the accuracy and precision of surface area measurements with rulers and digital tools, obtained from the field of wound treatment.
Methodology A silicone phantom of the vulva was created (Figure 1A), including four tumors with known surface area (A0). Two small tumors had an ellipse shape, and two large tumors had a more complex shape. Surface area (A) was measured with a ruler using the ellipse model, the imitoMeasure app, the imitoMeasure app with standardized angle (orthogonal) and distance to tissue (15 cm), the eKare system, and a 3D scan processed in Meshlab. The software of eKare automatically delineated tumors, while the other methods used user-indicated boundaries. Each method was tested 24 times on both tumor shapes.
Results Relative errors were computed as (A-A0)/A0, and are shown in Figure 1B. The eKare system was most accurate (0.03±0.07, mean±std). When using the ruler, the large tumor could not be measured accurately (-0.10±0.18). In this setting, 46% of surface area estimates departed from the expected value with >20%.
Conclusion This study shows that methods using 3D scans are very suitable to measure surface area on these curved tissue surfaces. The use of rulers should be avoided in case of tumors with complex shapes. A next step for us will be the assessment of these methods in a patient study, when tumor visibility may not always be optimal.
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