[Objectivity, reproducibility and validity of 3D ultrasound in dermatology]

Recently it has become possible to visualize the three-dimensional (3D) architecture of sonographic structures using high-resolution ultrasound above 20 MHz (Dermascan C, Denmark; DUB 20, Germany). We studied the objectivity, reproducibility, and validity of these two 3D analysis systems on 22 skin tumors. To validate both systems, we compared the sonometric and histometric volume in 4 tumors. The objectivity was calculated by repeated evaluation of the volume on the same serial B-scan sections at 3-month intervals. The two-dimensional B-scans and 3D images exhibited similar characteristics. Volumetric evaluations were reproducible with both systems (variation coefficient < or = 9.9%), when the applicator was oriented longitudinal to the body axis. By changing the orientation, the coefficient increased up to 58.1% (DUB 20). Sonometric and histometric volumes of a phantom model and of the tumors exhibited small deviations in the Dermascan C (< or = 8.1%) and in some tumors large deviations in the DUB 20 (< or = 93.1%). We can conclude that the 3D sonography is a reproducible method, which can be used to evaluate the volume of skin tumors and metastases under chemotherapy or radiotherapy. We suggest in particular to use the in-vivo tumor volume as a prognostic parameter for the malignant melanoma.