What Are Skin Tightening Treatments?

Skin tightening treatments are procedures designed to improve laxity and firmness by delivering controlled energy or regenerative stimulation into selected layers of the skin and underlying tissue.

They are commonly used for:

• Mild facial sagging
• Reduced skin elasticity
• Early jowls
• Loose jawline skin
• Double-chin laxity
• Neck wrinkles
• Crepey skin
• Fine lines
• Lower-face heaviness
• Mild brow drooping
• Loose body skin
• Overall facial aging

Non-surgical skin tightening does not remove excess skin in the same way as surgery.

The best results are generally achieved in patients with early to moderate laxity and realistic expectations.

How Skin Tightening Treatments Work

Many skin tightening procedures use controlled heat to stimulate tissue contraction and collagen remodeling.

Depending on the technology, treatment may target:

• Superficial dermis
• Deep dermis
• Fibrous tissue
• Superficial connective tissue
• Subcutaneous layers
• Facial-supporting structures

The treatment may help:

• Stimulate new collagen
• Support elastin remodeling
• Improve skin firmness
• Strengthen dermal support
• Refine facial contours
• Improve skin texture
• Reduce the appearance of mild laxity

Results usually develop gradually because collagen remodeling takes time.

Common Skin Tightening Treatments in Seoul

Depending on the patient’s skin thickness, facial anatomy, laxity, and goals, a dermatologist may recommend:

• Ultherapy
• Ultherapy Prime
• Shurink Universe
• Doublo Gold
• Sofwave
• Thermage FLX
• Oligio
• Density
• Volnewmer
• InMode Forma
• InMode FX
• Potenza
• Secret RF
• Sylfirm X
• Scarlet RF
• Titanium Lifting
• Thread Lift
• Collagen Stimulator Injections
• Skin Boosters
• Combination Lifting Programs

Each technology targets a different depth and type of tissue.

A device that works well for one patient may not be appropriate for another.

Ultrasound Skin Tightening

Ultrasound lifting treatments deliver focused ultrasound energy beneath the skin.

Common ultrasound lifting devices include:

• Ultherapy
• Ultherapy Prime
• Shurink Universe
• Doublo Gold
• Ultraformer
• Sofwave

Depending on the device and cartridge, ultrasound energy may be delivered at different depths.

Potential benefits include:

• Improved jawline definition
• Mild brow lifting
• Firmer lower-face skin
• Reduced jowl appearance
• Improved neck laxity
• Gradual collagen remodeling
• Minimal surface damage

Ultrasound treatment is often selected for patients who want deeper lifting support without surgery.

Radiofrequency Skin Tightening

Radiofrequency treatments use electrical energy to produce controlled heat within the tissue.

Common RF tightening treatments include:

• Thermage FLX
• Oligio
• Density
• Volnewmer
• InMode Forma
• Bipolar RF
• Monopolar RF
• Multipolar RF

Potential benefits include:

• Firmer skin
• Improved elasticity
• Smoother texture
• Reduced fine lines
• Better facial contours
• Improved lower-face laxity
• Gradual collagen remodeling

Radiofrequency treatment may be particularly useful for patients concerned about skin quality and diffuse laxity.

RF Microneedling for Skin Tightening

RF microneedling combines needle penetration with radiofrequency energy.

Common RF microneedling systems include:

• Potenza
• Secret RF
• Sylfirm X
• Scarlet RF
• Morpheus8

The needles deliver energy directly into selected skin layers.

Potential benefits include:

• Skin tightening
• Pore refinement
• Acne-scar improvement
• Fine-line reduction
• Improved texture
• Collagen stimulation
• Mild lower-face contouring

RF microneedling is more invasive than surface radiofrequency treatment and usually involves more visible recovery.

Device settings, needle depth, energy level, and treatment area must be carefully selected to reduce the risk of burns, scarring, pigmentation changes, nerve injury, or unwanted fat loss.

Monopolar RF vs Bipolar RF

Monopolar Radiofrequency

Energy travels between the treatment tip and a grounding component.

It is commonly used for:

• Deeper tissue heating
• Full-face tightening
• Jawline definition
• Lower-face laxity
• Collagen remodeling

Examples include:

• Thermage FLX
• Oligio
• Volnewmer

Bipolar Radiofrequency

Energy travels between electrodes positioned close together.

It is commonly used for:

• Controlled dermal heating
• Skin texture
• Mild laxity
• Facial maintenance
• Combination treatments

The best option depends on the depth and type of laxity being treated.

HIFU vs Radiofrequency

HIFU and Focused Ultrasound

Often focus on:

• Deeper tissue support
• Jawline lifting
• Mild jowls
• Brow lifting
• Lower-face definition
• Neck laxity

Radiofrequency

Often focuses on:

• Skin firmness
• Dermal collagen
• Fine lines
• Skin texture
• Diffuse laxity
• Overall skin quality

Many patients benefit from combining or alternating ultrasound and radiofrequency because they can target different tissue layers.

Ultherapy for Skin Tightening

Ultherapy uses microfocused ultrasound energy to target selected depths beneath the skin.

It is commonly used for:

• Jawline laxity
• Jowls
• Loose neck skin
• Mild brow drooping
• Lower-face lifting
• Décolletage lines

Potential benefits include:

• Gradual lifting
• Improved definition
• Collagen stimulation
• No surgical incision
• Minimal surface downtime

Treatment discomfort varies according to the treatment area, number of lines, anatomy, and pain-management protocol.

Shurink Universe for Skin Tightening

Shurink Universe is a Korean HIFU treatment frequently used for facial lifting and contour maintenance.

It may be selected for:

• Early facial laxity
• Jawline definition
• Mild jowls
• Lower-face contouring
• Double-chin concerns
• Regular lifting maintenance

Potential advantages include:

• Short treatment time
• Multiple cartridge depths
• Customized treatment areas
• Minimal downtime
• Compatibility with other procedures

The number of shots and treatment depth should be selected according to facial anatomy rather than using the same protocol for every patient.

Sofwave for Skin Tightening

Sofwave uses synchronous parallel ultrasound energy to heat the mid-dermis.

It is commonly considered for:

• Fine lines
• Mild laxity
• Lower-face firmness
• Neck skin
• Brow-area lifting
• Overall skin quality

Because it primarily targets the dermal layer, Sofwave may be chosen by patients who want tightening without aggressive treatment of deeper facial tissue.

Thermage FLX for Skin Tightening

Thermage FLX uses monopolar radiofrequency to produce controlled tissue heating.

It is commonly used for:

• Facial laxity
• Fine lines
• Jawline definition
• Lower-face firmness
• Eye-area tightening
• Body skin tightening

Potential benefits include:

• Full-face collagen remodeling
• Improved firmness
• Smoother skin
• Limited downtime
• Gradual results

The treatment plan depends on the tip used, number of shots, treatment area, and skin condition.

Oligio for Skin Tightening

Oligio is a Korean monopolar radiofrequency treatment used to improve skin firmness and mild laxity.

It may be selected for:

• Lower-face tightening
• Jawline definition
• Fine lines
• Skin texture
• Early sagging
• Preventive anti-aging care

Oligio is often chosen by patients seeking radiofrequency tightening with a customized number of shots and minimal downtime.

Density and Volnewmer Skin Tightening

Density and Volnewmer are radiofrequency-based treatments used in Korean dermatology programs.

Depending on the device and treatment protocol, they may target:

• Skin laxity
• Fine lines
• Jawline definition
• Facial firmness
• Collagen remodeling
• Overall skin quality

The appropriate device should be selected based on tissue thickness, facial fat distribution, skin sensitivity, and treatment goals.

InMode Skin Tightening

InMode platforms may combine different technologies for facial contouring and skin tightening.

Common treatment modes may include:

• Forma
• MiniFX
• FaceTite in more invasive settings
• RF-based contouring
• Bipolar radiofrequency

Potential treatment goals include:

• Skin firmness
• Jawline contouring
• Submental definition
• Lower-face shaping
• Reduced appearance of mild laxity

Some InMode treatments may affect both skin and fat.

Patients with naturally thin faces should receive conservative treatment planning to avoid unwanted volume reduction.

Titanium Lifting

Titanium Lifting is a light-based treatment used for immediate-looking facial tightening, brightening, and contour refinement.

It may be selected for:

• Mild facial laxity
• Jawline definition
• Skin brightness
• Event preparation
• Minimal-downtime lifting
• Overall facial rejuvenation

Results may be subtler than those achieved with deeper ultrasound or monopolar RF treatments.

Thread Lift

A thread lift uses absorbable threads placed beneath the skin to provide mechanical support and stimulate collagen.

It may be considered for:

• Mild to moderate jowls
• Lower-face sagging
• Poor jawline definition
• Cheek descent
• Early neck laxity

Compared with energy-based treatments, thread lifting may provide a more immediate repositioning effect.

However, possible risks include:

• Bruising
• Swelling
• Tenderness
• Asymmetry
• Skin dimpling
• Thread visibility
• Infection
• Thread migration

Thread lifting cannot reproduce the results of a surgical facelift in patients with significant laxity.

Collagen Stimulator Injections for Tightening

Collagen-stimulating injectables may improve skin firmness and structural support over time.

Options may include:

• Sculptra
• AestheFill
• Radiesse
• Juvelook Volume
• Other PLLA, PDLLA, CaHA, or PCL products

These treatments may help:

• Improve dermal thickness
• Restore facial support
• Improve elasticity
• Reduce crepey texture
• Support gradual rejuvenation
• Improve selected areas of volume loss

Collagen stimulators do not create the same mechanical lift as surgery, HIFU, or thread lifting.

Skin Boosters for Firmness

Skin boosters primarily improve hydration and skin quality, but better dermal condition may create a firmer and healthier-looking appearance.

Common options include:

• Rejuran Healer
• Rejuran HB
• Juvelook
• SKINVIVE
• Profhilo
• Hyaluronic acid skin boosters
• PRP
• Exosome-based recovery treatments

Skin boosters are generally best for:

• Fine lines
• Poor texture
• Dehydration
• Reduced elasticity
• Crepey skin
• Overall skin quality

They may be combined with lifting devices for more comprehensive treatment.

Skin Tightening for the Jawline

Jawline laxity may be caused by:

• Loose skin
• Descending facial tissue
• Enlarged masseter muscles
• Submental fat
• Facial volume loss
• Bone structure
• Reduced skin elasticity

Depending on the cause, treatment may include:

• Ultherapy
• Shurink Universe
• Thermage FLX
• Oligio
• InMode
• Jaw Botox
• Fat-dissolving injections
• Dermal fillers
• Collagen stimulators
• Thread lift

Treating the wrong cause may produce limited improvement.

A complete lower-face assessment is important before treatment.

Skin Tightening for Jowls

Jowls develop through a combination of skin laxity, tissue descent, facial volume changes, and jawline anatomy.

Potential treatments include:

• Focused ultrasound
• Monopolar RF
• RF microneedling
• Thread lift
• Collagen stimulators
• Chin or jawline filler
• Facial contouring treatment

Patients with significant jowls may require a surgical facelift for substantial correction.

Skin Tightening for the Neck

Neck laxity may involve:

• Loose skin
• Horizontal neck lines
• Platysmal bands
• Submental fat
• Reduced elasticity
• Crepey texture

Treatment options may include:

• Ultherapy
• Shurink Universe
• Sofwave
• Thermage FLX
• Oligio
• RF microneedling
• Profhilo
• Hyperdiluted Radiesse
• Neck Botox
• Thread lift

The appropriate treatment depends on whether the main concern is skin, muscle, fat, or structural aging.

Skin Tightening Around the Eyes

Eye-area laxity requires conservative treatment because the skin is thin and delicate.

Potential options include:

• Thermage eye treatment
• Focused ultrasound around selected areas
• Sofwave
• RF microneedling
• Rejuran I
• Eye Botox
• Fractional laser
• Medical skincare

Patients with substantial upper-eyelid skin excess or lower-eye bags may require surgical evaluation.

Skin Tightening for the Forehead and Brows

Non-surgical brow-area treatments may include:

• Ultherapy
• Shurink
• Sofwave
• Botox brow lift
• Thread lift
• RF treatment

Potential goals include:

• Mild brow elevation
• Improved forehead firmness
• Reduced upper-eyelid heaviness
• More refreshed eye appearance

Non-surgical treatment generally creates a modest lift.

Patients with significant brow descent may need a surgical brow lift or upper blepharoplasty assessment.

Body Skin Tightening

Skin tightening devices may also be used on:

• Abdomen
• Upper arms
• Inner thighs
• Knees
• Buttocks
• Flanks
• Décolletage
• Hands

Potential treatment options include:

• Radiofrequency
• RF microneedling
• Ultrasound
• Collagen stimulators
• Fractional laser
• Combination body contouring

Non-surgical treatments are most suitable for mild to moderate laxity.

Large amounts of excess skin after major weight loss commonly require surgical removal.

Benefits of Skin Tightening Treatments

Potential benefits may include:

• Firmer skin
• Improved elasticity
• Better jawline definition
• Reduced appearance of mild jowls
• Improved neck firmness
• Softer fine lines
• Better skin texture
• Collagen stimulation
• Minimal or limited downtime
• Natural-looking, gradual results
• Customized treatment depths
• Non-surgical rejuvenation

Results vary according to age, anatomy, skin thickness, degree of laxity, device settings, and individual collagen response.

Skin Tightening vs Facial Slimming

Skin tightening and facial slimming are not the same.

Skin Tightening

Targets:

• Loose skin
• Reduced elasticity
• Mild sagging
• Poor dermal support
• Fine lines

Facial Slimming

May target:

• Enlarged masseter muscles
• Excess facial fat
• Double chin
• Wide lower face
• Heavy facial contours

Facial slimming treatments may include jaw Botox, InMode FX, fat-dissolving injections, or lipolysis procedures.

Patients with thin faces should avoid unnecessary fat-reduction treatment.

Skin Tightening vs Dermal Fillers

Skin Tightening

Focuses on:

• Collagen remodeling
• Skin firmness
• Mild lifting
• Improved elasticity
• Gradual results

Dermal Fillers

Focus on:

• Volume restoration
• Chin projection
• Jawline definition
• Cheek enhancement
• Structural contouring

Some patients need tightening, while others need volume replacement.

Many patients benefit from a carefully balanced combination of both.

Skin Tightening vs Botox

Skin Tightening

Targets:

• Loose skin
• Collagen loss
• Reduced elasticity
• Mild sagging

Botox

Targets:

• Dynamic wrinkles
• Muscle activity
• Masseter enlargement
• Platysmal bands
• Facial-expression lines

Botox may complement skin tightening but cannot directly tighten significant loose skin.

Skin Tightening vs Surgical Facelift

Non-Surgical Skin Tightening

Generally offers:

• No large incisions
• Minimal or limited downtime
• Gradual improvement
• Modest lifting
• Maintenance treatments
• Lower treatment intensity

Surgical Facelift

Generally offers:

• Stronger tissue repositioning
• Removal of excess skin
• Correction of advanced jowls
• More significant neck improvement
• Longer recovery
• Longer-lasting structural correction

Non-surgical treatment should not be marketed as equivalent to a surgical facelift.

Combination Skin Tightening Programs

A personalized program may combine:

• HIFU and monopolar RF
• HIFU and Botox
• RF and skin boosters
• RF microneedling and Rejuran
• RF microneedling and Juvelook
• Thread lift and collagen stimulators
• Jaw Botox and lifting devices
• Fat-reduction treatment and skin tightening
• Dermal fillers and energy-based lifting
• Laser rejuvenation and RF treatment

Combination treatment is most effective when every procedure addresses a different component of facial aging.

What Happens During a Skin Tightening Consultation?

Patients typically receive:

• Facial analysis
• Skin-laxity assessment
• Skin-thickness evaluation
• Facial-fat assessment
• Jawline evaluation
• Neck assessment
• Medical-history review
• Previous procedure review
• Personalized treatment recommendations

The clinic should evaluate whether the concern is primarily caused by:

• Loose skin
• Facial fat
• Muscle activity
• Volume loss
• Tissue descent
• Bone structure

This helps prevent unnecessary or unsuitable treatment.

What Happens During Treatment?

The procedure depends on the selected technology.

A typical session may involve:

• Skin cleansing
• Clinical photography
• Treatment-area marking
• Ultrasound gel or coupling fluid
• Topical numbing when necessary
• Energy-based treatment
• Cooling or soothing care
• Post-treatment instructions

Treatment time may range from approximately 30 minutes to more than two hours depending on the device and treatment area.

Is Skin Tightening Painful?

Comfort varies according to:

• Device type
• Treatment depth
• Energy level
• Treatment area
• Number of shots
• Individual pain sensitivity
• Pain-management protocol

Possible sensations include:

• Heat
• Tingling
• Pressure
• Brief electrical sensations
• Deep aching
• Pinching with RF microneedling

Pain-management options may include:

• Topical anesthetic
• Oral medication
• Cooling
• Vibration
• Local anesthesia
• Sedation for selected invasive procedures

Pain control should not compromise safe communication during treatment.

Recovery After Skin Tightening

Recovery depends on the treatment.

Non-Invasive Ultrasound or RF

Temporary effects may include:

• Mild redness
• Swelling
• Tenderness
• Tingling
• Temporary sensitivity
• Mild bruising

Most patients return to normal activities immediately or shortly after treatment.

RF Microneedling

Temporary effects may include:

• Redness
• Swelling
• Pinpoint crusting
• Dryness
• Rough texture
• Mild bruising
• Temporary sensitivity

Recovery may take several days depending on treatment intensity.

Thread Lift

Possible recovery effects include:

• Swelling
• Bruising
• Tenderness
• Tightness
• Temporary dimpling
• Restricted facial movement

Recovery instructions vary according to the thread type and treatment area.

Results Timeline

Immediate Changes

Some patients may notice:

• Temporary contraction
• Better facial definition
• Mild tightening
• Smoother-looking skin

Immediate improvement may partly reflect temporary swelling or tissue contraction.

Progressive Results

Over the following weeks and months, patients may notice:

• Firmer skin
• Improved elasticity
• More defined jawline
• Reduced appearance of mild laxity
• Better skin texture
• Progressive collagen remodeling

Results generally continue developing for approximately two to six months depending on the treatment.

How Many Sessions Are Needed?

The number of treatments depends on:

• Device used
• Degree of laxity
• Treatment area
• Age
• Skin thickness
• Previous treatments
• Treatment intensity
• Individual collagen response

Some ultrasound and monopolar RF treatments are performed as one primary session.

Other treatments may require:

• Three or more initial sessions
• Monthly treatment
• Maintenance every several months
• Annual maintenance

A customized schedule should be recommended after assessment.

How Long Do Results Last?

The duration of results varies according to:

• Treatment technology
• Energy level
• Age
• Degree of laxity
• Lifestyle
• Sun exposure
• Smoking
• Weight changes
• Skincare
• Natural aging
• Maintenance treatment

Results are not permanent because skin aging continues.

Many patients repeat treatment every six to eighteen months, depending on the device and treatment plan.

Estimated Skin Tightening Cost in Seoul

Treatment costs vary depending on:

• Device used
• Number of shots or lines
• Treatment area
• Treatment tip
• Number of sessions
• Combination procedures
• Pain-management method
• Clinic expertise
• Aftercare included

For accurate comparison, patients should ask whether the quoted price includes:

• Full treatment area
• Genuine device tip
• Exact number of shots
• Doctor treatment
• Anesthesia
• VAT
• Aftercare

Most clinics provide customized pricing after consultation.

Who Is a Good Candidate?

Skin tightening may be suitable for individuals who:

• Have mild to moderate skin laxity
• Have early jowls
• Want improved jawline definition
• Have loose neck skin
• Have reduced elasticity
• Want preventive anti-aging treatment
• Prefer non-surgical rejuvenation
• Accept gradual and modest improvement
• Want minimal downtime

The best candidates usually have some remaining skin elasticity and do not have large amounts of excess skin.

Who May Not Be a Good Candidate?

Treatment may need to be delayed, modified, or avoided for patients with:

• Active skin infection
• Open wounds
• Severe inflammatory skin disease
• Certain implanted electrical devices
• Metal implants in relevant treatment areas
• Significant sensory impairment
• Uncontrolled medical conditions
• Pregnancy
• Severe facial volume loss
• Very thin facial tissue
• Advanced skin laxity requiring surgery
• Recent incompatible procedures

Contraindications vary by device.

Patients should disclose medical conditions, medications, implants, dental work, and previous aesthetic procedures before treatment.

Potential Risks and Side Effects

Possible risks vary by treatment and may include:

• Redness
• Swelling
• Bruising
• Tenderness
• Temporary numbness
• Tingling
• Burns
• Blistering
• Pigmentation changes
• Infection
• Scarring
• Facial asymmetry
• Nerve irritation
• Unwanted facial fat loss
• Temporary weakness
• Skin dimpling after threads

Serious complications are uncommon but possible.

Correct device selection, conservative settings, accurate anatomy knowledge, and experienced medical supervision are important.

Avoiding Unwanted Facial Fat Loss

Some energy-based devices can affect subcutaneous fat when treatment depth or intensity is unsuitable.

Patients with thin faces should discuss:

• Existing facial volume
• Hollow cheeks
• Temple hollowing
• Previous fat grafting
• Previous facial liposuction
• Desired treatment depth
• Whether fat reduction is intended

A more aggressive treatment is not always a better treatment.

The goal should be tightening the appropriate tissue while preserving natural facial volume.

Why Skin Tightening Treatments Are Popular in Seoul

Skin tightening treatments are popular in Seoul because clinics offer a wide range of ultrasound, radiofrequency, microneedling, injectable, and combination options.

Potential advantages include:

• Multiple device choices
• Customized treatment depths
• Non-surgical facial lifting
• Minimal or limited downtime
• Preventive anti-aging options
• Combination with injectables
• Facial contouring programs
• International patient support
• Personalized maintenance plans

Many international patients visit Hongdae and Seoul for customized skin tightening programs focused on the jawline, lower face, neck, eye area, and overall facial firmness.

Frequently Asked Questions

What is the best skin tightening treatment?

The best treatment depends on whether the concern is caused by loose skin, facial fat, volume loss, muscle activity, or tissue descent. Ultrasound may be selected for deeper support, while radiofrequency may be preferred for diffuse skin firmness and texture.

Can non-surgical treatment lift sagging skin?

Non-surgical treatment may provide modest improvement in mild to moderate laxity. It cannot remove large amounts of excess skin or reproduce the results of a surgical facelift.

Is HIFU better than radiofrequency?

Neither is universally better. HIFU and focused ultrasound generally target deeper tissue layers, while radiofrequency commonly emphasizes dermal heating, skin firmness, and texture. Some patients benefit from both.

Is Thermage better than Ultherapy?

Thermage and Ultherapy use different types of energy and target different tissue characteristics. Thermage uses monopolar radiofrequency, while Ultherapy uses focused ultrasound. Treatment selection should be based on anatomy and goals.

Does skin tightening reduce facial fat?

Some devices or settings may affect fat, while others are intended primarily for skin and collagen. Patients with thin faces should receive conservative, tissue-preserving treatment planning.

Can skin tightening improve jowls?

Skin tightening may improve early or mild jowls. More advanced jowls may require fillers, thread lifting, fat treatment, or surgical lifting depending on the cause.

Can skin tightening improve a double chin?

Skin tightening can improve laxity beneath the chin, but significant submental fat may require fat-dissolving injections, lipolysis, liposuction, or another contouring treatment.

How soon will I see results?

Some patients notice early firmness, but most collagen-related improvement develops gradually over approximately two to six months.

How long do results last?

Results may remain visible for several months to over a year depending on the treatment, age, skin condition, and maintenance plan. Results are not permanent.

Is skin tightening painful?

Discomfort varies by device, depth, and treatment area. Patients may experience heat, pressure, tingling, aching, or pinching. Pain-management options may be available.

Is there downtime after skin tightening?

Most non-invasive ultrasound and radiofrequency treatments have minimal downtime. RF microneedling and thread lifting generally involve more redness, swelling, or bruising.

Can skin tightening be combined with Botox?

Yes. Botox may improve dynamic wrinkles, jaw width, or platysmal bands while an energy-based treatment addresses skin firmness and laxity.

Can skin tightening be combined with fillers?

Yes. Fillers may restore structural support or facial volume while tightening treatments improve skin firmness. Timing should be planned carefully.

Can skin tightening be combined with Rejuran or Juvelook?

Yes. Rejuran, Juvelook, and other skin boosters may be used to improve skin quality alongside energy-based lifting treatments. The treatment order and timing depend on the procedures selected.

How many shots of HIFU or RF do I need?

The appropriate number depends on facial size, treatment area, skin thickness, device type, cartridge depth, and degree of laxity. Shot count alone does not determine treatment quality.

Are skin tightening treatments available for international patients in Seoul?

Yes. Dermatology clinics in Hongdae and Seoul provide ultrasound lifting, radiofrequency tightening, RF microneedling, thread lifting, and customized combination programs for international patients.