  A major obstacle when attempting to train a machine learning system to
evaluate facial clefts is the scarcity of large datasets of high-quality,
ethics board-approved patient images. In response, we have built a deep
learning-based cleft lip generator designed to produce an almost unlimited
number of artificial images exhibiting high-fidelity facsimiles of cleft lip
with wide variation. We undertook a transfer learning protocol testing
different versions of StyleGAN-ADA (a generative adversarial network image
generator incorporating adaptive data augmentation (ADA)) as the base model.
Training images depicting a variety of cleft deformities were pre-processed to
adjust for rotation, scaling, color adjustment and background blurring. The ADA
modification of the primary algorithm permitted construction of our new
generative model while requiring input of a relatively small number of training
images. Adversarial training was carried out using 514 unique frontal
photographs of cleft-affected faces to adapt a pre-trained model based on
70,000 normal faces. The Frechet Inception Distance (FID) was used to measure
the similarity of the newly generated facial images to the cleft training
dataset, while Perceptual Path Length (PPL) and the novel Divergence Index of
Severity Histograms (DISH) measures were also used to assess the performance of
the image generator that we dub CleftGAN. We found that StyleGAN3 with
translation invariance (StyleGAN3-t) performed optimally as a base model.
Generated images achieved a low FID reflecting a close similarity to our
training input dataset of genuine cleft images. Low PPL and DISH measures
reflected a smooth and semantically valid interpolation of images through the
transfer learning process and a similar distribution of severity in the
training and generated images, respectively.
