An 18mm spot size is preferred because it significantly improves both the depth of laser penetration and the speed of treatment. By minimizing the physical scattering of the laser beam within the skin, an 18mm diameter allows energy to reach deep hair roots more effectively than a 12mm spot, while simultaneously covering a larger surface area per pulse to accelerate procedures on extensive zones like the legs.
Core Takeaway While a 12mm spot size is capable of hair removal, increasing the diameter to 18mm fundamentally changes how light travels through tissue. The larger spot size reduces lateral energy loss, ensuring that the therapeutic dose reaches the deepest follicles for higher clearance rates, all while drastically reducing the time required to treat large body areas.
The Physics of Penetration and Scattering
Minimizing Lateral Scattering
When a laser beam enters the skin, photons naturally scatter. With a smaller 12mm spot, a significant percentage of photons scatter sideways (laterally) and are lost before they can penetrate deep into the dermis.
An 18mm spot size creates a wider column of light. This larger volume creates a "shielding" effect where central photons are less likely to scatter out of the treatment zone, maintaining high intensity deeper into the tissue.
Reaching Deep-Seated Follicles
Leg hair roots can be situated deep within the dermis. Because the 18mm spot minimizes scattering losses, it achieves a deeper effective penetration depth.
This ensures the laser energy is delivered uniformly to the bulb of the hair follicle. In contrast, a smaller spot might dissipate too much energy in the upper layers of the skin, failing to heat deep roots sufficiently for permanent damage.
Operational Efficiency for Large Zones
Reducing Treatment Duration
Treating large surface areas like the legs or back requires thousands of individual laser pulses. An 18mm spot covers significantly more surface area per pulse than a 12mm spot.
This reduction in the total number of pulses required leads to a substantial decrease in overall treatment time. For busy clinics, this means shorter sessions for patients and the ability to book more appointments per day.
Lowering Operator Fatigue
Using a larger spot size reduces the frequency of handpiece movements and the repetition required by the practitioner.
This lowers operator labor intensity, allowing staff to maintain precision and consistency throughout a long day of treatments. This efficiency directly correlates to a higher patient turnover rate for medical aesthetic clinics.
Understanding the Trade-offs
The Energy Density Requirement
While larger spot sizes are superior for depth, they require more power to be effective. To maintain the same fluence (energy per square centimeter) across an 18mm spot as you would on a 12mm spot, the machine must generate significantly more total energy.
If a machine lacks sufficient power, increasing the spot size to 18mm might result in a "diluted" beam that is too weak to be effective.
Precision vs. Coverage
An 18mm spot is excellent for legs, backs, and thighs, but it lacks the maneuverability required for contoured or small areas.
Using an 18mm tip on the upper lip or around the ears can be difficult and may result in treating unintended areas. A comprehensive setup often requires the ability to switch between large and small spot sizes.
Making the Right Choice for Your Goal
When deciding between spot size configurations for your equipment or treatment plan, consider the specific anatomical targets.
- If your primary focus is treatment speed and turnover: Prioritize the 18mm spot size, as it drastically reduces the time needed for backs and legs while increasing patient throughput.
- If your primary focus is clinical efficacy on deep hair: Choose the 18mm spot size, as the reduced scattering ensures the energy actually reaches the deep roots typical of leg hair.
- If your primary focus is precision on small areas: Stick to a 10mm or 12mm spot size, which offers better control for facial work or small contours where deep penetration is less critical.
Ultimately, for large areas like the legs, the 18mm spot size is the superior technical choice because it combines deep, uniform energy delivery with the logistical benefit of rapid application.
Summary Table:
| Feature | 12mm Spot Size | 18mm Spot Size |
|---|---|---|
| Penetration Depth | Moderate (higher scattering loss) | Deep (minimal lateral scattering) |
| Treatment Speed | Standard | High (covers more area per pulse) |
| Target Areas | Facial & small contours | Legs, back, and large body zones |
| Operator Fatigue | Higher (more pulses required) | Lower (fewer pulses required) |
| Power Requirement | Lower | Higher (requires robust energy output) |
Scale Your Clinic's Efficiency with BELIS Technology
At BELIS, we specialize in professional-grade medical aesthetic equipment designed exclusively for high-traffic clinics and premium salons. Our advanced laser systems—including Diode Laser Hair Removal, Pico, and Nd:YAG—are engineered to deliver the power needed for large-diameter spot sizes, ensuring superior depth of penetration and rapid patient turnover.
Whether you are looking for high-performance hair removal solutions or specialized care devices like HIFU, Microneedle RF, and Body Sculpting (EMSlim, Cryolipolysis), BELIS provides the technical edge your business needs to stay ahead.
Ready to upgrade your treatment capabilities and increase your ROI? Contact us today to explore our professional equipment portfolio
References
- Seyyed Masoud Davoudi, Alireza Firooz. Comparison of Long-Pulsed Alexandrite and Nd:YAG Lasers, Individually and in Combination, for Leg Hair Reduction. DOI: 10.1001/archderm.144.10.1323
This article is also based on technical information from Belislaser Knowledge Base .
Related Products
- Diode Tri Laser Hair Removal Machine for Clinic Use
- Clinic Diode Laser Hair Removal Machine with SHR and Trilaser Technology
- Trilaser Diode Hair Removal Machine for Beauty Clinic Use
- Diode Laser SHR Trilaser Hair Removal Machine for Clinic Use
- Clinic Use IPL and SHR Hair Removal Machine with Nd Yag Laser Tattoo Removal
People Also Ask
- Why is the Anagen phase crucial for effective diode laser hair removal? Master Timing for Permanent Results
- Why should clinics conduct detailed literature research before adopting new laser hair removal technologies?
- How does extending the pulse duration protect dark skin? Master Safe Laser Hair Removal for Fitzpatrick Types IV-VI
- How is high-resolution optical microscopy utilized in the clinical evaluation of laser hair removal? Scientific Metrics
- What are the primary functions of an epidermal cooling system? Enhance Safety and Efficacy in Laser Hair Removal
