Focal Depth Selection: What 1.5/3.0/4.5 mm Cartridges Each Target

The coagulation point always forms at the cartridge’s geometric focus, so focal length sets the layer. Facial support structures span dermis (0.3-2 mm), septa (2-4 mm) and superficial fascia (~4-4.5 mm) — no single depth covers all, so mainstream platforms use multi-depth cartridge sets.

• 1.5 mm: reticular dermis and dermal-subcutaneous junction, for fine lines, texture, thin periorbital skin.
• 3.0 mm: superficial fat and septa, for lower-face contour, submental area, neck.
• 4.5 mm: cheek superficial fascia (SMAS level), the workhorse layer for lifting.

• Forehead: chiefly 1.5 mm, avoiding supraorbital nerve lines, reduced energy.
• Zygoma and jawline: 4.5+3.0 mm, avoiding bony high-pain zones.
• Neck: 3.0+1.5 mm; thyroid territory is off-limits.
• Periorbital: dedicated 0.5-1.5 mm cartridges, caution inside orbital rim.

1. Thin faces step down in focal length — 4.5 mm can pass fascia into deep structures.
2. Avoid mapped danger zones (parotid duct, temporal branch of facial nerve, thyroid).
3. Treat deep before shallow in the same zone to limit cumulative energy.

Can the whole face be done with 4.5 mm only?

Not advised — forehead and periorbital zones carry deep-structure risk at that depth. Multi-depth layering is the proper protocol.

Are more shots per cartridge better?

Shot count is a capacity figure; point density and energy selection decide results. Line length and point spacing matter more at equal counts.

• HIFU
• SMAS Layer
• RF Treatment Depth