Today we will continue discussing HIFU (Ultrasound lifting devices). To use this technology properly, we must fully understand and master its working principles.

1. Mechanism of Micro-Focused Ultrasound

(1) Energy Source: Ultrasound

HIFU lifting devices use Ultrasons focalisés de haute intensité (HIFU) as their energy source, which is high-frequency ultrasound.

However, the energy used for non-invasive anti-aging treatments est much lower than the energy used in surgical HIFU for cutting tissue.

Therefore, the more accurate academic term is:

Micro-Focused Ultrasound (MFU).

The US FDA-approved Ultherapy system includes real-time ultrasound visualization, so its academic name is:

Micro-Focused Ultrasound with Visualization (MFU-V).

The frequencies used by Ultherapy include:

• 4 MHz
• 7 MHz
• 10 MHz

Among them:

• 7 MHz and 10 MHz lose energy rapidly in tissue because molecular friction and scattering occur more frequently.
  Therefore they can only treat superficial skin layers, tel que 1.5 mm or 3.0 mm depths.
• 4 MHz attenuates more slowly in tissue and can pénétrer plus profondément, reaching layers such as the 4.5 mm SMAS fascia layer.

---

(2) Ultrasound Focusing Principle

The principle is similar to using a magnifying glass to focus sunlight.

Le transducer emits high-frequency ultrasound waves and focuses energy precisely at a specific depth beneath the skin.

This is called geometric focusing.

As ultrasound passes through the epidermis and superficial dermis, the energy remains dispersed.
Therefore, the heat per unit area is insufficient to cause tissue damage.

Only at the geometric focal point does the energy density suddenly reach its maximum peak.

---

(3) Ultrasound Heat Generation

When ultrasound waves travel through tissue, they cause high-frequency oscillation of tissue molecules, vibrating millions of times per second.

This produces instant heat.

Due to intense molecular friction, acoustic energy converts into thermal energy, raising the temperature at the focal point rapidly to 60°C–70°C within milliseconds.

---

(4) Transducer

The most critical component of the ultrasound treatment probe is the transducer.

Its function is to convert electrical energy into ultrasound (mechanical vibration energy).

The working mechanism relies on the inverse piezoelectric effect.

Processus

Inside the transducer are piezoelectric ceramic crystals.

When high-frequency alternating current is applied:

• the crystals expand and contract rapidly according to the electrical frequency.

Résultat

This rapid mechanical vibration pushes the surrounding medium (such as coupling gel and skin tissue) to form longitudinal pressure waves, which we call vagues échographiques.

---

(5) Thermal Coagulation Points

Focused ultrasound produces instant temperatures of 60–70°C at specific depths in the skin.

This heat creates thermal coagulation points (TCPs) approximately 1 mm in size.

These points are surrounded by healthy tissue, forming a fractional pattern of controlled micro-injuries.

Inside each TCP:

• Collagen fibers undergo thermal denaturation
• Collagène contracts immediately

This produces an instant tightening and lifting effect.

Both thermal denaturation and coagulation trigger the body’s wound healing response, conduisant à months of collagen and elastin regeneration.

Histologically:

• TCPs appear as white round regions under the microscope.
• In reality, they are wedge-shaped, not perfectly round.

---

(6) Wound Healing Response: New Collagen and Elastin Formation

Thermal coagulation points initiate three biological repair phases.

1. Inflammatory Phase

Duration: Immediately after treatment up to about 70 days.

When tissue reaches the collagen denaturation temperature (60–70°C):

• significant inflammation occurs
• macrophages remove damaged tissue
• cytokines recruit fibroblasts

Fibroblasts then begin producing new collagen.

---

2. Proliferation Phase

This phase may overlap with inflammation and begins within hours after treatment.

Fibroblasts synthesize:

• Type III collagen
• Elastin
• Fibronectin
• Glycosaminoglycans
• Other matrix components

These substances rebuild the extracellular collagen matrix.

---

3. Remodeling Phase

This stage usually begins around 3 weeks after treatment and can last up to one year.

During this phase:

• Type III collagen gradually converts into Type I collagen
• Collagen fibers form stronger cross-linking structures

This remodeling process is the key to long-term skin tightening and lifting.

2. Mechanism of Chinese “Ultraformer-type” HIFU Devices

Le Ultraformer-type cartridges of Chinese devices function similarly to those of the US Ultherapy system.

Difference Between 2D hifu Head and Ultraformer-type Head

HIFU 2D et MPT HIFU (Micro-Pulse Technology HIFU) refer to different energy delivery methods and treatment modes in micro-focused ultrasound devices. The distinction mainly lies in how ultrasound energy is emitted and how heat accumulates in tissue.

Below is a clear technical comparison.

---

2D HIFU vs MPT HIFU

Paramètre	HIFU 2D	MPT-HIFU
Energy emission	Single pulse or traditional pulse	Multiple micro-pulses
Livraison d'énergie	One strong pulse per point/line	Energy divided into many small pulses
Thermal formation	Instant high-temperature coagulation point	Gradual heat accumulation
Temperature peak	Higher instantaneous temperature	Lower instantaneous temperature
Niveau de douleur	Plus haut	Inférieur
Tissue damage	More concentrated	More controlled
Sécurité	Modéré	Plus haut
Treatment comfort	Modéré	Plus haut
Vitesse de traitement	Normale	Usually faster with continuous scanning
Technology generation	HIFU traditionnel	Newer generation technology

---

2D HIFU (Traditional HIFU)

Principe de travail

2D HIFU usually uses single pulse energy to create thermal coagulation points (TCPs) dans la peau.

Energy is released once per shot, creating a focused point that quickly reaches: ~60–70°C

This causes:

• contraction du collagène
• dénaturation du collagène
• SMAS tightening

Caractéristiques

Avantages

• Strong lifting effect
• Pénétration profonde
• Clear TCP formation

Désavantage

• Higher pain
• Higher nerve irritation risk
• Heat concentration at one point

---

2. MPT HIFU (Micro Pulse Technology)

MPT stands for Micro Pulse Technology.

Instead of delivering one large pulse, the system splits energy into multiple micro-pulses.

Example:

Traditional pulse

1 pulse = 25–50 ms

MPT pulse

1 pulse = multiple sub-pulses
each ≤5 ms

These micro-pulses are released in rapid sequence, allowing heat to accumulate gradually.

---

How MPT changes the heating process

HIFU traditionnel

Energy → instant heat spike → TCP

MPT-HIFU

micro pulse
micro pulse
micro pulse
heat accumulation → TCP

Résultat:

• smoother heating
• less nerve stimulation
• Amélioration du confort

---

Thermal Effect Comparison

Facteur	HIFU traditionnel	MPT-HIFU
Heating pattern	Instant spike	Gradual build-up
Tissue response	Strong thermal shock	Controlled thermal stimulation
Pain sensation	Sharp pain	Sensation de réchauffement
Safety margin	Smaller	Plus grand

---

Clinical Effect Comparison

Treatment goal	HIFU 2D	MPT-HIFU
SMAS lifting	Fort	Fort
Resserrement de la peau	Bien	Bien
Confort	Moyen	Haut
Temps d'arrêt	Minimal	Minimal
Risk of nerve irritation	Plus haut	Inférieur

---

Why many new HIFU machines use MPT

Modern HIFU devices adopt MPT because it:

1. reduces pain significantly
2. improves safety
3. maintains lifting effect
4. improves patient tolerance

This is particularly important for:

• full face treatment
• sensitive patients
• sliding treatment modes

---

Simple analogy

HIFU traditionnel
→ Hammer strike

MPT-HIFU
→ Many small taps building heat

Both can produce the same thermal effect, but the second is more controlled and comfortable.

---

💡 Important:
MPT is not a different ultrasound technology, it is simply a different pulse delivery method within micro-focused ultrasound systems.

---

Sliding Operation and Volumetric Heating

Unlike the stamping method used by the knife head, the MPT HIFU head slides across the skin continuously.

It releases high-frequency pulses repeatedly, allowing heat to accumulate gradually in deeper tissues.

This sliding motion transforms treatment coverage:

from points → to surfaces

Heat becomes more evenly distributed in target layers such as:

• derme
• fat layer
• fascia layer

Avantages :

• reduced overheating risk
• significantly reduced pain

---

Typical Clinical Operation

Usually:

1. 2D hifu head is used first
   → precise lifting of key areas
   (jawline, lower cheek, apple cheek support)
2. MPT hifu head is then used
   → sliding across the entire face
   → enhancing collagen contraction and fat tightening

---

3. Relationship Between Mechanism and Clinical Efficacy

The fundamental principle of ultrasound lifting is: controlled thermal injury in target tissue layers.

In theory: Higher temperatures within a safe range produce stronger lifting effects.

However, excessive temperature can cause:

• excessive tissue damage
• poor healing
• fibrosis
• severe pain
• higher nerve injury risk

Therefore:

• Ultherapy (US system)
  temperature: 65–70°C
  → theoretically stronger effect
• Chinese HIFU systems
  temperature: around 60°C
  → theoretically safer

---

3. Fractional Pattern of HIFU Treatment

HIFU treatment essentially uses a fractional pattern, similar to:

• lasers fractionnés
• Micro-aiguilletage RF

Each ultrasound line:

• length: 25 mm
• contains 17–25 TCPs
• TCP diameter: 0.5–1 mm
• spacing: 1.1–1.5 mm
• maximum adjustable spacing: 2 mm

Healthy tissue remains between points, acting as biological support zones to accelerate healing and collagen regeneration.

Without these gaps, treatment would resemble large-area burns, leading to necrosis or scarring.

---

4. Key Operating HIFU Principles

A. Full Contact (Prevent Misfire / Burns)

The treatment probe must maintain complete contact with the skin.

Reason:

Air gaps cause ultrasound reflection, shifting energy to the surface and causing epidermal burns or blisters.

Operation:

• apply sufficient ultrasound coupling gel
• maintain stable vertical pressure

---

B. Avoid Overlapping Shots (Prevent Heat Accumulation)

Never fire repeatedly at the same position in a short time.

Reason:

Independent thermal points may merge into sheet-like burns, causing:

• severe pain
• nerve damage
• fat destruction

Operation:

Maintain at least 1 mm spacing between lines.

---

5. Technical Innovations in the Peninsula “Super HIFU”

To balance Efficacité et sécurité, Peninsula devices control TCP temperature at about 60 ° C.

This is lower than Ultherapy.

To maintain efficacy, they introduced dual focal technology.

---

Comfort Micro-Pulse Technology

Instead of one large pulse, energy is divided into multiple micro-pulses.

Pulse width comparison:

• Ultherapy: 25–50 ms
• Peninsula Gen-2: ≤20 ms
• Latest Super HIFU: ≤5 ms sub-pulses

Avantages :

• Amélioration du confort
• improved safety

---

Résumé

1. Micro-focused ultrasound is one of the most widely used non-invasive skin lifting technologies worldwide.
2. The treatment technique is closely linked to the physical principles of ultrasound energy delivery.
3. There are many technical details involved in MFU treatments. If you want to master non-invasive anti-aging treatments, continuous learning is essential.