Lossy compression in diagnostic virtual 3-dimensional microscopy--where is the limit?

Data compression is inevitable to reduce the huge data amounts of virtual slides, especially in virtual 3-dimensional (3D) microscopy. Lossy compression influences the image quality and leads to recognizable compression artifacts above a compression ratio of 20:1 in JPEG2000 format. To test out whether higher compression ratios are acceptable in diagnostic pathology, we prepared virtual 3D slides of gastric biopsy specimens with or without Helicobacter pylori gastritis using 5 different compression ratios as follows: 20:1, 40:1, 50:1, 75:1, and 200:1. The virtual 3D slides were diagnosed in a blinded manner by 3 pathologists according to the updated Sydney classification. The results showed no significant differences using virtual 3D slides with any compression of up to 200:1. We conclude that compression ratios higher than those commonly used can be applied in virtual microscopy, even in diagnostic applications.