There are some differences between 4D and 7D HIFU treatments:1. Depth of penetration: This allows the ultrasound waves to target more areas of the skin and stimulate collagen production in deeper layers.2. Number of lines:7D HIFU machines typically have more lines than 4D HIFU machines, allowing for more precise and detailed treatment.3. Treatment time:7D HIFU treatments typically take longer to perform than 4D HIFU treatments, as they require more precision.4. Results: While both treatments are effective for skin tightening and rejuvenation, 7D HIFU provides more dramatic results.