Intense Pulsed Light : An alternative to Pulse Dye Laser in treatment of vascular lesions.

Abstract
In contrast to most lasers, the light pulse duration of IPL systems can easily be changed to match the TRT of the target. Most lasers emit a single, characteristic wavelength, whereas flash lamps in IPL systems emit the entire visual optical spectrum  as well as a part of the near infrared (NIR) spectrum from 400nmn -1200nm. This extended spectrum can be utilized to treat to various vascular lesions of varing depth and sizes. This article helps in understandind the potential use of IPL in vascular therapy. Device: Intense Pulsed Light with inbuilt RF and cooling. Use of 510 /530nm (Green) ,560 /570/ 585nm (Yellow) filters. Indications: IPL can be used for vascular pathology such as Post acne erythema, Rosacea, Telangiectasias, Hemangioma of infant and adults, Superficial varicose veins, Couperose. Facility: IPL can be carried out in a clinic or hospital setting or a nursing home with a small operation theatre. Informed consent and counseling: The dermatologic consultation should include detailed assessment of the patient's skin condition and skin type. An informed consent is mandatory to protect the rights of the patient as well as the practitioner. All patients must have carefully taken preoperative and postoperative pictures. Parameters: Depends on the indication, the area to be treated, the acceptable downtime for the desired correction, and to an extent the skin color. Anesthesia: There is acceptable pain and is tolerated well by patients but may require topical anesthesia. In most cases, topical cooling and numbing using icepacks is sufficient, even in an apprehensive patient. Postoperative care: The newer IPL with Rf systems are safe, even in type V VI skin types, and postoperative care is minimal. Proper postoperative care is important in avoiding complications. Post-treatment edema and redness settle in a few hours. Postoperative sun avoidance and use of sunscreen is mandatory. Use of Epidermal growth factor gel helps in faster healing and recovery time.

Introduction: Intense pulsed light (IPL) devices are non-laser high intensity light sources that make use of a high-output flashlamp to produce a broad wavelength output of noncoherent light, usually in the 400 to 1200nm range. Light pulses generated by most modern devices are produced by bursts of electrical current passing through a xenon gas-filled chamber.¹The lamp output is then directed toward the distal end of the handpiece, which, in turn, releases the energy pulse onto the surface of the skin via a sapphire or quartz crystal. Individual systems use different cooling systems, such as a cryogen spray, contact cooling, or forced refrigerated air, to protect the epidermis in contact with the conduction crystal of the handpiece.² The selection of proper filter according to the type,size and depth of vessels is crucial in obtaining favourable results. When a filter of 560nm is used it means the wavelength of 400 to 560nm is cut off or filtered and the wavelength from 560nm to 1200nm is emitted.
The first report of the use of an IPL device in dermatology dates back to 1996, when it was successfully utilized to treat a cohort of 80 patients with treatment-resistant facial port wine stains in Germany.^3,4 The device, which employed a light source emitting noncoherent light with a wavelength spectrum of 515 to 1200nm, had been originally developed for the treatment of a wide range of benign vascular lesions, including telangiectasias and reticular varicose leg veins.
There are few principles and concepts in IPL which forms the basis of treatment:
I. Thermal Relaxation Time (TRT):⁵
Defined as the time required for a structure to lose 50% of the peak heat acquired to the surrounding tissue.Target tissue damage is most selective if the pulse duration is less than or equal to the thermal relaxation time of the target tissue. TRT for epidermis is 3 to 10 milliseconds and Vessels have TRT of 0.5 to 5 msec depending on the size of the vessels.⁶
The use of TRT is of two ways,
1. Increasing the pulse Delay (PD) (Off Time) more than 10 msec saves the epidermis by allowing sufficient time for heat to diffuse from the epidermal melanin. 2. Keeping the Pulse Width (PW) (On Time) equal or slightly higher than the TRT will ensure the damage the target tissue. Lesser PW than TRT causes sub therapeutic results and much higher PW than TRT causes collateral damage to the tissue surrounding the target since excess energy diffuses out of the target giving an undesirable side effect.
Incases like Hemangioma where the target is large using higher PW is advocated to destroy the vessel walls by coagulation and increased collateral damage. Use of higher TRT can be manipulated to give a desired response but it requires experience and preplanning.7
II. Selective Photothermolysis:⁵
Anderson and Parrish coined the term “selective photothermolysis”. The term selective photothermolysis describes site-specific, thermally mediated injury of microscopic tissue targets by selectively absorbed pulses of radiation (Anderson 1983).
Three basic elements are necessary to achieve selective photothermolysis:
1. A wavelength that is target specific,
2. Pulse duration according to the TRT of the target.
3. Sufficient fluence that could damage the intended target.
According to the Theory of Selective Photothermolysis, sufficient energy must be delivered with a pulse duration that is less than or equal to the TRT of the target structure in order to effectively damage the target.
A new theory called Extended Theory of Selective Photothermolysis has been proposed where the treatment pulse width for non-uniformly pigmented targets is significantly longer than the target thermal relaxation time (TRT) to effectively treat various concentration of chromophore.⁸ The theory provides new recommendations for photoepilation and photosclerotherapy parameters.
In contrast to diffuse coagulation injury, selective photothermolysis can achieve high temperatures in structures or individual cells with little risk of scarring because gross dermal heating is minimized.
Vascular mode of IPL:
This Mode uses wavelengths from 510nm to 560nm (Green to Yellow). The targeting chromophore is oxy and deoxyhemoglobin.
The thermal relaxation time of vessels 10 to 50µm in diameter is 0.1 to 10ms, averaging 1.2ms. ^2,9 However, shorter pulse durations results in vessel rupture and haemorrhage secondary to RBC explosion.¹⁰ This will lead to hemosiderin pigmentation. Therefore, with single laser pulses, the therapeutic window is small. This lead to the development of a wider single pulse or a multipulsed technology like IPL that is able to transfer absorbed heat to the endothelium without causing its rupture. There are multiple well-established and effective laser treatments for targeting blood vessels in the skin, with the pulsed dye laser being the workhorse in many practices nationwide. However, one limitation of the latter is the need to achieve purpura in several clinical scenarios to achieve acceptable results. In contrast, one of the main advantages of IPL technology is the absence of postoperative purpura, which minimizes postprocedure downtime substantially. Rather than inducing immediate purpura, the goal of treating vascular lesions with IPL is to raise the blood vessel temperature high enough to cause its coagulation, leading to its destruction and replacement by fibrous granulation tissue. Because of its polychromaticity, IPL can target oxyhemoglobin (predominantly found in clinically red lesions), deoxygenated hemoglobin (predominantly in blue lesions), and methemoglobin, with absorption peak wavelengths of 418, 542, and 577.
The  510nm / 530nm / 560nm / 570nm / 585nm  targets  the  Chromophores  oxy  and  deoxy  haemoglobin  in  the  superficial  vessels in  conditions  like  telangiectasia, rosacea. These  Chromophores  by  absorbing  the  specific  wavelength  gets  heated  causing  selective  thermal  damage  in  the  vessels  being  treated  resulting  in  coagulation of endothelial  and  surrounding  vessel  wall  followed  by  thrombosis  and  removal  of  defective  venules  over  time.  
Parameters:

1. Filters :The 510nm / 530nm filter emits wavelength of green light which is used in superficial vascular condition, when size of vessels is small.     The 560nm / 570 / 585+ nm filter emits yellow light which is used in deeper vascular conditions and when the size of vessel is large.
2. Energy :In  light  based  medicine,  fluence which  may  be  more  properly  referred  to  as  radiant  exposure, is  a                  measurement  of  energy  over  treatment  area. The  area  is  usually  the  spot  size  of  the  light  device. Fluence              is  described  as  the  energy  delivered  per  unit  area  and  it  has  units  of  J/cm2. In Vascular mode energy /                 fluence is used starting at 25 J/cm² to as high as 50 J/cm² .
3. Pulse duration:
4. Pulse Width: The  time  each  pulse  is  On  measured  in  milliseconds ( ms). The  pulse  width  can  be  from  2ms  to  10ms  depending  on  target. The  use  of  pulse  helps  in  targeting  the  chromophore  more  specifically  and  giving  the  optimum  results.   
5. Pulse Delay:The  time  interval  when  the  light  is  Off   between  Pulses measured  in  milliseconds ( ms).The  light  is  delivered  in  pulses  of  On and  Off  time.  The   pulse  delay  is  to  give  time  for  the  epidermis  to  cool  between  pulses. Minimum  of  10ms  is  set  which  can  be  increased  depending  on  the  skin   type  the  maximum  pulse  delay  depends  on  the  different  IPL  company.

Since  most  of  the  IPL  comes  with  an  inbuilt  contact  cooling  the  pulse  width  of  10ms  is  sufficient  for  all  treatment  modes. 

1. Number of Pulses:

           The  use  of  pulsing  is  to  deliver  the  given  fluence ( joules )  in  a  divided  two, three, or  five  small  consecutive  pulses. This  can  improve  the  absorption  of  the  wavelengths  by  the  target  chromophore  and  in  turn  protecting  the  epidermis.

1. RF energy:

       IPL action on the target tissue creates an initial relatively small temperature gradient, and by applying RF energy next, a larger temperature gradient is obtained at the target chromophore. This allows heating of the target to a sufficiently high temperature to destroy the target without heating the surrounding skin tissues to damaging levels.        Rf energy of 10 – 30 W is used for a time of 0.3 to 0.5 seconds. For  doing  vascular  work  certain  basics  have  to  be  known.  Depending  on  the  condition  the   settings  will  change. The  changes  are  dependent  mainly  on  two  conditions ( a )  size  of  the  vessels  involved ( b )  Choice  of  filter.
Size  of  Vessels:
Depending on the size of the vessels to be treated the pulse durations are optimised. Smaller diameter (0.1–0.2 mm) bright red vessels are treated with the shorter pulse duration  between  2.5 – 3.5 ms. Medium vessels (0.2–0.3 mm) treated with the shorter pulse duration between  3.5– 5.0 ms. Larger vessels (0.3–0.5 mm) treated with a  pulse duration  between  5–8 ms. Greater than 0.5 mm vessels will require the longest pulse duration possible by the machine.
An initial pulse of 2.5 ms followed by a second pulse delivered after a delay or rest interval 10–20 ms. The second coupled or synchronized pulse is set for 2.5 – 8 ms depending on the diameter of the vascular target.  Fluence Joules  depends  on  the  filter. Assuming that the thermal relaxation time of the human epidermis (average thickness of 100 microns or 0.1mm) is 10 milliseconds, the treatment of smaller vessels should ideally be done with multiple pulses with at least 10 millisecond delays between pulses to allow for adequate epidermal cooling.
The  reason  for  different  pulse  duration  time,  double  and  triple  pulsing  is  to allow  preheating  of  vessels  with  absorption  by  smaller  vessels  with  the first  pulse,  then  allow  surrounding  structures  to  cool. The  second  coupled  longer  pulse  then  heats  up  the  larger vessels.
Smaller  more  superficial  vessels  theoretically  absorb  the  shorter  pulses more  selectively,  while  the  larger  diameter  vessels  absorb  the   longer  pulses. Photothermal  coagulation results  in  an  immediate  darkening  of  the  vessels  with  an  urticarial edema  10 Mins – End Point.
You  can  do  a  smaller  vessel  settings  in  the  first  pass  then  after  5  minutes  do  a  second  pass  with  a  medium  or  large  vessel  settings  if  there  is  a  mixed  picture. The  510  nm  filter  is  used  for  initial  treatment, followed  by  the  560 nm  filter  to  better  target  larger, more  deeply  situated  telangiectasias. If one takes advantage of the  longer-wavelength hemoglobin absorption  band  at  560–595 nm, where  tissue  penetration  is  enhanced  and  melanin absorption  is  reduced, less  heating  of  the  epidermis  should  occur   and  more  energy  is  transmitted  to  the  blood  vessels. The Table illustrates what settings I prefer to use in vascular work using 510nm / 560nm filter when treating type 5 type/ 6 skin.
The pulse duration/ Pulse Width (PW) can be increased in subsequent pulses and the Pulse Delay (PD) can be altered to user preference.
The Joules can be increased with caution and after determining the patient’s skin type and response to previous treatment.
The Joules can be increased upto 50 J/cm2 when treating type 1/ type 2 skin and when treating Hemangioma.

My  Experience:  Don’t  give  pressure  on  the  hand  piece  since  it  will  move  the  blood  in  the  vessels  away  from  the  treatment  area  which  will  results  in  less  target  chromophore  which  is  oxy  and  deoxy  hemoglobin.       Don’t cool  the  area  too  much  before  firing  since  it  will  constrict  the  vessels  and  resulting  in  the  same  drawback.  
                 Keeping  the  hand  piece  in  contact  with  the  skin  for  just  1 to 2  seconds before  firing  then  without  giving  pressure  on  the  skin  fire, it  gives  the  best  results. But  in  case  large  Hemangiomas  giving  pressure  slightly  will  get  the  blood  away  from  that  area  making  the  vessels  smaller  and  permits adequate coagulation  of  the  larger vessels.
In  case  of  IPL  systems  with  RF  you  can  ON  the  RF  and  use  RF energy  of  20 – 30 W  with  on  time  of  0.3  to  0.5  seconds. Always  recheck  the  settings  of the IPL before  firing  the  first  shot. I  prefer  to  apply  the  cool  gel  on  the  crystal ( Hand Piece) and  slowly glide  it  over  the  treatment  area. 

Discussion : The successful treatment of vascular lesions with IPL depends on the type and size of vessels targeted, the Filter chosen,and energy used. Rosacea, post acne redness, and superficial telangiectatic veins gives the best clinical response. In contrast to the pulsed dye laser, which delivers a 585nm wavelength at a relatively short-pulse duration (450 microseconds), thereby limiting its depth of penetration to a maximum depth of 1.5mm, the broader wavelength range emitted by IPL devices and delivered through variable pulse durations and multiple-pulse sequences enables deeper-seated vessels and cavernous vascular lesions to be targeted.¹¹ strong>Ideally, the pulse duration should be compatible with the vessel diameter and be about equal or below the thermal relaxation time for that dimension cutaneous blood vessel so that the surrounding tissue is barely harmed.¹² Modern IPL devices provide pulse durations up to 100 milliseconds, which enables delivery of light energy to vessels over longer periods of time, resulting in gentle, uniform heating or even coagulation across the entire vessel while reducing vessel rupture and its associated purpura and hyperpigmentation.¹³
                IPL systems have been used effectively in the treatment of cavernous hemangiomas, venous and capillary malformations and facial and leg telangiectasias^14,15. When treating port wine stains, especially those with a nodular component with external light sources, an old challenge has been targeting deeper-seated vessels located at the base of such lesions. It has been shown that using a 585nm wavelength pulsed dye laser source, most energy is deposited in the superficial vessels and that this decreases the amount of light available to deeper vessels (shadowing effect).¹⁶ Thus, clinical response of lightening in port wine stains with pulsed dye laser is dependent on vessel depth, diameter, and wall thickness. With IPL in contrast, the variable pulse durations and the multiple split-light pulses cause additive heating, leading to coagulation of vessels of different diameters and, theoretically, better concurrent heating of superficial and deeper vessels. A 5 to 100 millisecond delay between pulses allows the epidermis to cool down, preventing damage. In most clinical studies of port wine stains, IPL treatments were well tolerated. Side effects were infrequently observed and included temporary erythema, superficial blistering, hypopigmentation, and hyperpigmentation.¹⁷ When performing IPL in Hemangiomas the joules is kept higher with a longer pulse duration in the first session. This would end up with blistering.Regular dressing or applying epidermal growth factor permits faster healing. The treatment is performed only once in six weeks giving time for the healing process.

a)Before treatment	b)IPL 560nmCut off filter with excess of 40 J/cm2 causing immediate blistering reaction with brownishdiscolouration and shrinking of lesion.	c) Epidermolysis with crusting of lesion after 2/3 days

d)After 2 treatments one month apart there considerable reduction in size of lesion

Other vascular lesions commonly targeted by IPL are telangiectasias and cherry angiomas of various anatomical locations. 18,19 IPl is useful in treating keloids hypertrophic scar by devascularisation of the lesions.20The most frequently used intervals between treatments reported in the literature vary between 3 and 8 weeks. In a study of 1,000 consecutive patients with facial telangiectasias or vascular marks treated from 1998 to 2005 with the Photoderm VL (Lumenis Aesthetic, Santa Clara, California), IPL was shown to be a fast, safe, and effective modality. In this study, large facial veins were treated in triple-pulse mode using the 590 cutoff filter with pulse times of 2.4, 3.0, and 3.5 milliseconds; a delay of 30 and 25 milliseconds; and an energy flow of 50 to 56 J/cm2. Red fine telangectasias usually were treated in double-pulse mode using the 570nm cutoff filter with pulse times of 2.8 and 4.5 milliseconds, a delay of 30 milliseconds, and energy levels of 38 to 42J/cm2. Spider lesions were treated with the same settings as for large veins using a white screen with a varying size hole (1–4mm) to hit the arteriolar part of the lesion. Perilesional erythema, blanching, and vessel clearance were considered optimal treatment endpoints.

Two treatments of IPL two weeks apart with energy 24 J/cm2, 510nm cut off filter, reduction post acne redness is seen.

IPL is useful in treating erythematous acne scars and post acne redness which persists after treating with isotretinoin.  
Two treatments of IPL two weeks apart with energy 25 J/cm2, 560nm cut off filter Patient will need 2 more treatments.
IPL has also been shown to be an effective treatment for the telangiectasias and background erythema/flushing seen in patients with erythematotelangiectatic rosacea. Recently, it has been shown that IPL is at least equally effective as nonpurpuragenic pulsed dye laser in reducing both signs and symptoms of rosacea.21,22

Two treatments of IPL two weeks apart with energy 25 J/cm2, 560nm cut off filter Patient will need 2 more treatments

References:
1. Raulin C, Greve B, Grema H. IPL technology: a review. Lasers Surg Med. 2003;32:78–87.
2. Weiss RA, Sadick NS. Epidermal cooling crystal collar device for improved results and reduced side effects on leg telangiectasias using intense pulsed light. Dermatol Surg. 2000;26(11):1015–1018.
3. Raulin C, et al. Treatment of a nonresponding port wine stain with a new pulsed light source (PhotoDerm VL) Lasers Surg Med. 1997;21(2):203–208.
4. Raulin C, et al. Treatment of essential telangiectasias with an intense pulsed light source (PhotoDerm VL) Dermatol Surg.1997;23(10):941–945; discussion 945-946.
5. Anderson RR, Parrish JA. Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation.Science 1983,220:524–7
6. Anderson RR, Parrish JA. Microvasculature can be selectively damaged using dye lasers.Lasers Surg Med 1981,1:263–76
7. J. Stuart Nelson et al. Laser pulse duration must match the estimated thermal relaxation time for successful photothermolysis of blood vessels, Lasers in Medical Science March 1995, Volume 10, Issue 1, pp 9-12.
8. Altshuler GB, Anderson RR et al. Extended theory of selective photothermolysis Lasers Surg Med. 2001;29(5):416-32.
9. Anderson RR, Parrish JA. Microvasculature can be selectively damaged using dye lasers: a basic theory and experimental evidence in human skin. Lasers Surg Med 1981; 1:263.
10. Garden JM, Tan OT, Kerschmann R et al. Effect of dye laser pulse duration on selective cutaneous vascular injury. J Invest Dermatol 1986; 87:653.