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M. S. Whiteley

would arise from veins that had previously been competent and had become incompetent during that year. This development of new varicose veins from previously normal veins is called “de novo” varicose veins.

It is interesting to note that the “de novo” rate of developing new varicose veins is the minimum recurrence rate that is possible, and to even achieve this, one has to completely overcome the risks of recurrent varicose veinsthat are discussed above. This has been the aim of The Whiteley Clinic over the last 18years. Through the development of a rigid protocol of venous duplex ultrasound diagnosis and treatment of all venous incompetence, including incompetent perforators and pelvic vein incompetence, using techniques that we have shown to cause transmural death in the treated vein segments, our audited recurrence rate is consistently 3.3% per year. This recurrence rate, coupled with the identication of the source of any recurrent reux and checking that it isalways from a de novo source and not a previously targeted vein, allows us to be condent that our protocol—The Whiteley Protocol—is currently the optimal way to treat varicose veins.

References

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FG.Chronic venous insufciency: clinical and duplex correlations. The Edinburgh Vein Study of venous disorders in the general population. J Vasc Surg. 2002;36(3):520–5.

2. Evans CJ, Fowkes FGR, Ruckley CV, Lee AJ.

Prevalence of varicose veins and chronic venous insufciency in men and women in the general population: Edinburgh Vein Study. J Epidemiol Community Health. 1999;53:149–53.

3. Maurins U, Hoffmann BH, Losch C. Distribution

and prevalence of reux in the supercial and deep venous system in the general population—results from the Bonn Vein Study, Germany. J Vasc Surg. 2008;48:680–7.

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Saphenofemoral valve: gate keeper turned into rear guard. Phlebology. 2002;17:29–31.

7. Abu-Own A, Scurr JH, Coleridge Smith PD. Saphenous vein reux without incompetence at the saphenofemoral junction. Br J Surg. 1994;81(10):1452–4.

8. Schul MW, Schloerke B, Gomes GM.The reuxing anterior accessory saphenous vein demonstrates similar clinical severity when compared to the reuxing great saphenous vein. Phlebology. 2016;31(9):654–9.

https://doi.org/10.1177/0268355515604532.

9. Rutherford EE, Kianifard B, Cook SJ, Holdstock JM, Whiteley MS.Incompetent perforating veins are associated with recurrent varicose veins. Eur J Vasc Endovasc Surg. 2001;21(5):458–60.

10. Whiteley MS. Part One: for the motion. venous perforator surgery is proven and does reduce recurrences. Eur J Vasc Endovasc Surg. 2014;48(3):239–42.

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11. Hobbs JT. Varicose veins arising from the pelvis due to ovarian vein incompetence. Int J Clin Pract. 2005;59(10):1195–203.

12. Giannoukas AD, Dacie JE, Lumley JS. Recurrent varicose veins of both lower limbs due to bilateral ovarian vein incompetence. Ann Vasc Surg. 2000;14(4):397–400.

13. Whiteley AM, Taylor DC, Dos Santos SJ, Whiteley MS. Pelvic venous reux is a major contributory cause of recurrent varicose veins in more than a quarter of women. J Vasc Surg Venous Lymphat Disord. 2014;2(4):411–5.

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14. Whiteley MS, Dos Santos SJ, Harrison CC, Holdstock JM, Lopez AJ. Transvaginal duplex ultrasonography appears to be the gold standard investigation for the haemodynamic evaluation of pelvic venous reux in the ovarian and internal iliac veins in women. Phlebology. 2015;30(10):706–13. https://doi.

org/10.1177/0268355514554638.

15. Dos Santos SJ, Holdstock JM, Harrison CC, Lopez AJ, Whiteley MS.Ovarian vein diameter cannot be used as an indicator of ovarian venous reux. Eur J Vasc Endovasc Surg. 2015;49(1):90–4.

16. Asano M, Yoshida K, Tatai K. Observation of the behavior of microcirculation by rabbit ear chamber technique. I.Bull Inst Publ Health. 1963;12:34.

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18. Asahara T, Masuda H, Takahashi T, Kalka C, Pastore C, Silver M, Kearne M, Magner M, Isner JM.Bone marrow origin of endothelial progenitor cells responsible for postnatal vasculogenesis in physiological and pathological neovascularization. Circ Res. 1999;85(3):221–8.

19. Jones L, Braithwaite BD, Selwyn D, Cooke S, Earnshaw JJ.Neovascularisation is the principal cause of varicose vein recurrence: results of a randomised trial of stripping the long saphenous vein. Eur J Vasc Endovasc Surg. 1996;12(4):442–5.

20. Munasinghe A, Smith C, Kianifard B, Price BA, Holdstock JM, Whiteley MS.Strip-track revascular-

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4 Recurrent Varicose Veins

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ization after stripping of the great saphenous vein. Br J Surg. 2007;94(7):840–3.

21. Kianifard B, Holdstock J, Allen C, Smith C, Price B, Whiteley MS.Randomized clinical trial of the effect of adding subfascial endoscopic perforator surgery to standard great saphenous vein stripping. Br J Surg. 2007;94(9):1075–80.

22. Ostler AE, Holdstock JM, Harrison CC, Price BA, Whiteley MS.Strip-tract revascularization as a source of recurrent venous reux following high saphenous tie and stripping: results at 5-8 years after surgery. Phlebology. 2015;30(8):569–72.

org/10.1177/0268355514535927

23. Rautio T, Ohinmaa A, Perälä J, Ohtonen P, Heikkinen T, Wiik H, Karjalainen P, Haukipuro K, Juvonen T.Endovenous obliteration versus conventional stripping operation in the treatment of primary varicose veins: a randomized controlled trial with comparison of the costs. J Vasc Surg. 2002;35(5):958–65.

24. Fassiadis N, Kianifard B, Holdstock JM, Whiteley MS. A novel endoluminal technique for varicose vein management: the VNUS closure. Phlebology. 2002;16:145–8.

25. Fassiadis N, Kianifard B, Holdstock JM, Whiteley MS. Ultrasound changes at the saphenofemoral junction and in the long saphenous vein during the rst year after VNUS closure. Int Angiol. 2002;21(3):272–4.

26. Kianifard B, Holdstock JM, Whiteley MS. Radiofrequency ablation (VNUS Closure®) does not cause neo-vascularisation at the groin at one year: results of a case controlled study. Surgeon. 2006;4(2):71–4.

27. Whiteley MS, Holdstock J. Percutaneous radiofrequency ablations of varicose veins (VNUS closure). In: Greenhalgh RM, editor. Vascular and endovascular challenges. London: Biba Publishing; 2004. p.361–81.

28. Whiteley M.Varicose veins: endovascular options. In: Greenhalgh RM, editor. Towards vascular and endovascular consensus. London: Biba Publishing; 2005. p.564–72.

29. Whiteley M. New methods of vein ablation. In: Davies AH, Lees T, Lane IF, editors. Venous disease simplied. London: Harley; 2006.

30. Proebstle TM, Krummenauer F, Gül D, Knop J. Nonocclusion and early reopening of the great saphenous vein after endovenous laser treatment is uence dependent. Dermatol Surg. 2004;30(2 Pt

1):174–8.

31. Proebstle TM, Moehler T, Gül D, Herdemann S.Endovenous treatment of the great saphenous vein using a 1,320 nm Nd:YAG laser causes fewer side effects than using a 940 nm diode laser. Dermatol Surg. 2005;31(12):1678–83.

32. Cowpland CA, Cleese AL, Whiteley MS. Factors affecting optimal linear endovenous energy density for endovenous laser ablation in incompetent lower limb truncal veins - a review of the clinical evidence. Phlebology. 2017;32(5):299–306. https://doi.

org/10.1177/0268355516648067.

https://doi.

33. Badham GE, Strong SM, Whiteley MS. An in vitro study to optimise treatment of varicose veins with radiofrequency-induced thermo therapy. Phlebology. 2015;30(1):17–23.

org/10.1177/0268355514552005

34. Badham GE, Dos Santos SJ, Whiteley MS. Radiofrequency-induced thermotherapy (RFiTT) in a porcine liver model and exvivo great saphenous vein. Minim Invasive Ther Allied Technol. 2017;26:200–6.

https://doi.org/10.1080/13645706.2017.1282520.

35. Ashpitel H, Salguero F, La Ragione R, Whiteley M.Radial-ring endovenous laser penetrates deeper into the vein wall than forward-ring jacket-tipped bers and reduces carbonization— an exvivo study using histology and immunohistochemistry. J Vasc Surg Venous Lymphat Disord. 2017;5(1):147–8.

https://doi.org/10.1016/j.jvsv.2016.10.016.

36. Whiteley MS.Endovenous thermal ablation of varicose veins and examination of the use and failings of linear endovenous energy density (LEED). In: Whiteley M, Dabbs E, editors. Advances in phlebology and venous surgery, vol. 1. Milton Keynes: Whiteley Publishing; 2017. p.11–24.

37. Braithwaite B, Hnatek L, Zierau U, Camci M, Akkersdijk G, Nio D, Sarlija M, Ajduk M, Santoro P, Roche E. Radiofrequency-induced thermal therapy: results of a European multicentre study of resistive ablation of incompetent truncal varicose veins. Phlebology. 2013;28(1):38–46.

org/10.1258/phleb.2012.012013.

38. Badham GE, Dos Santos SJ, Lloyd LBA, Holdstock JM, Whiteley MS. One-year results of the use of endovenous radiofrequency ablation utilising an optimised radiofrequency-induced thermotherapy protocol for the treatment of truncal supercial venous reux. Phlebology. 2017;33:298.

org/10.1177/0268355517696611.

39. Parsi K.Interaction of detergent sclerosants with cell membranes. Phlebology. 2015;30(5):306–15. https://

doi.org/10.1177/0268355514534648.

40. Cooley-Andrade O, Cheung K, Chew AN, Connor DE, Parsi K.Detergent sclerosants at sub-lytic concentrations induce endothelial cell apoptosis through a caspase dependent pathway. Apoptosis. 2016;21(7):836–45.

https://doi.org/10.1007/s10495-016-1252-3.

41. Wollmann JC. The history of sclerosing foams. Dermatol Surg. 2004;30(5):694–703.

42. Ikponmwosa A, Abbott C, Graham A, HomerVanniasinkam S, Gough MJ. The impact of different concentrations of sodium tetradecyl sulphate and initial balloon denudation on endothelial cell loss and tunica media injury in a model of foam sclerotherapy. Eur J Vasc Endovasc Surg. 2010;39(3):366–71.

https://doi.org/10.1016/j.ejvs.2009.12.025.

43. Whiteley MS, Dos Santos SJ, Fernandez-Hart TJ, Lee CT, Li JM.Media damage following detergent sclerotherapy appears to be secondary to the induction of inammation and apoptosis: an immunohistochemical study elucidating previous histological observations. Eur J Vasc Endovasc Surg. 2016;51(3):421–8.

https://doi.org/10.1016/j.ejvs.2015.11.011.

https://doi.

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44. Lam YL, Lawson JA, Toonder IM, Shadid NH, Sommer A, Veenstra M, et al. Eight-year follow-up of a randomized clinical trial comparing ultrasoundguided foam sclerotherapy with surgical stripping of the great saphenous vein. British Journal of Surgery. 2018;105(6):692–8.

45. Kendler M, Averbeck M, Simon JC, Ziemer M.Histology of saphenous veins after treatment with the ClariVein® device - an ex-vivo experiment. J Dtsch Dermatol Ges. 2013;11(4):348–52.

org/10.1111/ddg.12022

46. Boersma D, van Haelst ST, van Eekeren RR, Vink A, Reijnen MM, de Vries JP, de Borst GJ.Macroscopic and histologic analysis of vessel wall reaction after mechanochemical endovenous ablation using the clarivein OC device in an animal model. Eur J Vasc Endovasc Surg. 2017;53(2):290–8.

org/10.1016/j.ejvs.2016.11.024.

47. Whiteley MS, Dos Santos SJ, Lee CT, Li JM. Mechanochemical ablation causes endothelial and medial damage to the vein wall resulting in deeper penetration of sclerosant compared with sclerotherapy alone in extrafascial great saphenous vein using an exvivo model. J Vasc Surg Venous Lymphat Disord. 2017;5(3):370–7.

jvsv.2016.12.009.

48. Boersma D, van Eekeren RR, Werson DA, van der Waal RI, Reijnen MM, de Vries JP.Mechanochemical endovenous ablation of small saphenous vein insufciency using the ClariVein(®) device: one-year results of a prospective series. Eur J Vasc Endovasc Surg. 2013;45(3):299–303.

ejvs.2012.12.004.

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https://doi.

49. Todd KL, Wright D, Orfe E.The durability of polidocanol endovenous microfoam treatment effect on varicose vein symptoms and appearance in patients with saphenofemoral junction incompetence: oneyear results from the VANISH-2 study. J Vasc Surg Venous Lymphat Disord. 2014;2(1):112.

org/10.1016/j.jvsv.2013.10.027

50. Chan YC, Law Y, Cheung GC, Cheng SW.Predictors of recanalization for incompetent great saphenous veins treated with cyanoacrylate glue. J Vasc Interv Radiol. 2017;28(5):665–71.

jvir.2017.01.011

51. Chan YC, Law Y, Cheung GC, Ting AC, Cheng SW. Cyanoacrylate glue used to treat great saphenous reux: measures of outcome. Phlebology. 2017;32(2): 99–106.

52. Proebstle TM, Alm J, Dimitri S, Rasmussen L, Whiteley M, Lawson J, Cher D, Davies A. The European multicenter cohort study on cyanoacrylate embolization of reuxing great saphenous veins. J Vasc Surg Venous Lymphat Disord. 2015;3(1):2–7.

https://doi.org/10.1016/j.jvsv.2014.09.001.

53. Frullini A, Fortuna D. Laser assisted foam sclerotherapy (LAFOS): a new approach to the treatment of incompetent saphenous veins. Phlebologie. 2013;66(1):51–4.

54. Smarandache A.Laser beams interaction with polidocanol foam: molecular background. Photomed Laser Surg. 2012;30(5):262–7. https://doi.org/10.1089/

pho.2011.3187.

55. Brand FN, Dannenberg AL, Abbott RD, Kannel WB. The epidemiology of varicose veins: the Framingham Study. Am J Prev Med. 1988;4(2):96–101.

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https://doi.

Relevance ofWavelength inLaser

https://t.me/med1917

Treatment ofVaricose Veins

HarinderSinghBedi andYudhishtarSinghBedi

Endovenous laser therapy (EVLT) or endovenous laser ablation (EVLA) was introduced as a minimally invasive treatment for varicose veins. Lasers work by producing endovenous thermal damage and hence obliteration of the diseased vein. The short- and long-term efcacy and extent of ablative damage and also the complications of pain, phlebitis, etc. are dependent to some extent on the wavelength of the laser. There are continuous modications in the wavelength used with the aim of minimizing side effects and improving efciency. Different laser systems as well as varying application strategies are under study. Investigational research and close analysis have helped in a better understanding of the relationship between the clinical efcacy and the physical aspects of the laser with a continuous renement of treatment.

Endovenous thermal ablation of varicose veins came into vogue because of the need for reducing the morbidity associated with the open stripping technique and to reduce the hospitalization and pain and need for general anaesthesia and so hasten patient recovery. Early clinical results of endovenous laser therapy (ELT) were published by Navarro and Bone [1].

The laser system introduces the laser light into the vein lumen by a malleable optical bre. Laser energy is absorbed and transformed into heat energy. Depending on the absorption characteristics of the target molecules in the tissue (e.g. water or haemoglobin) and on the laser wavelength used, there are cellular damage and destruction and collagen shrinkage leading to occlusion of the vein. The laser light energy is carried in a bre of diameter of up to 600 μm. The bre is inserted into the vein via a catheter system. Systems emitting laser light of wavelengths in the near-infrared spectral eld (810, 940, 980, 1064, 1320 and 1470nm) are used in clinical practice.

Using these techniques, the thermal damage of the vein results in occlusion. One characteristic of ELT is the different varieties of treatment protocols using different laser systems. A critical analysis of clinical results and research have elucidated on the connection between different types of laser application and efcacy of clinical results. This has led to a continuous renement and development of ELT.The following article outlines the basics of endovenous laser and research for improving this minimally invasive procedure.

H. S. Bedi (*) Cardiovascular Sciences of Ludhiana Mediways Hospital, Ludhiana, Punjab, India

Y. S. Bedi USC, Los Angeles, CA, USA

https://t.me/med1917

H. S. Bedi and Y. S. Bedi

5.1 Simple Basics ofaLaser

5.1.1 Spontaneous andStimulated Emission

By nature most atoms exist in a low-energy (ground) state [2, 3]. They can be excited to a higher-energy state when they absorb thermal, optical or electrical energy. An electron in a higher-energy orbit is unstable. On returning to the original state, it releases its dened energy as a photon (particle of light). This is known as spontaneous emission. The amount of energy released determines the wavelength or colour of the light emitted. If an electron already in an excited state encounters a photon of the proper energy, the electrons drop to a lower orbit and emit a photon. The stimulating photon is not absorbed but continues on its way, resulting in two identical energy or wavelength photons. Einstein called this stimulated emission. For stimulated emission to occur in a majority, it is necessary for more electrons to be in the upper energy level. This is known as population inversion. It is created by pumping electrical or light energy into the population of atoms (the gain medium) to move them to higher-energy levels. When the laser is switched on, the gain medium is pumped, population inversion occurs and individual atoms in the population undergo spontaneous emission, emitting photons in random directions. A photon will pass by an atom with electrons in the upper level and cause it to emit a second photon travelling in the same direction, phase and wavelength. There are now two photons; each can cause stimulated emission and give four photons and so on. In order for photons to continuously amplify, the gain medium is placed between two mirrors. One of these emitted photons, purely by accident, is in the axis of the two mirrors and is reected back into the gain medium, continuing the amplication. Each photon reected back causes stimulated emission, and photon numbers go on increasing. This produces an avalanche of coherent light. One of the mirrors is designed to allow some of the light through—the output beam. The beam is monochromatic, collimated and coherent.

5.1.2 Laser Construction

There are three components making up a laser system: an energy source or a pump, a gain medium and two mirrors that form an optical resonator [2, 3]. The pump source which provides energy to the laser system includes electrical discharges, ash lamps, light from another laser and even chemical reactions. The type of pump source used principally depends on the gain medium. The gain medium is the major determining factor of wavelength and energy, and it can be a gas, liquid, solid or semiconductor (diode laser) (Fig. 5.1). In this gain medium, spontaneous or stimulated emission of photons takes place. The optical resonator, or optical cavity, in its simplest form is two mirrors at each end of the gain medium. Light from the medium, produced by spontaneous emission, is reected back into the medium many hundreds of times amplifying the beam. Thus we have LASER: Light Amplied by Stimulated Emission of Radiation.

5.2 Radiation

Radiation is a form of energy that travels at the speed of light and spreads out or radiates [2, 3]. It includes visible light, infrared, ultraviolet, radio waves, microwaves and X-rays. Energy and momentum get imparted when the radiation interacts with matter.

The electromagnetic spectrum is a complete range of electromagnetic waves (waves with both electric and magnetic components) ranging from those with low frequency and energy levels along with correspondingly long wavelengths to those with high-frequency and high-energy levels with correspondingly short wavelengths (Fig. 5.2). This relationship is explained by the formula:

Wavelength = speed of light/frequency; and

energy = Planks constant (h)

× frequency.

Lasers produce nonionizing radiation at frequencies in the infrared, visible or ultraviolet region of the electromagnetic spectrum.

300

Diode 980 nm

20000

Wavelengh

Visible spectrum

10 km

1 pm

5 Relevance ofWavelength inLaser Treatment ofVaricose Veins

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Pulsed Dye

Argon

KTP

Excimer

Ultraviolet

400 500 600 700 800 900

Ruby

Fig. 5.1 The types of lasers

1 km

100 m

10 m

1 m

Alexandrite

Diode

100 mm

Near Infrared

1 mm

10 mm

Ho:YAG

1 µm

Er:YAG

100 nm

Mid Infrared

10 nm

Nd:YAG

1000 1500 2000 3000 4000 5000

100 µm

10 µm

7500 10000

1 nm

100 pm

CO2

10 pm

100 kHz

1 MHz

10 MHz

1 GHz

100 MHz

Frequency

Radio waves

Radar Infrared Ultraviolet X-radiation

FM radio

and TV

700

Crimson

Fig. 5.2 The electromagnetic spectrum

10 GHz

100 GHz

Microwaves

600

RED GREEN

Yellow

1 THz

10 THz

Optical IR

500

Cyan

100 THz

BLUE

1 PHz

Optical UV

400

Violet

10 PHz

100 PHz

1 EHz

10 EHz

Gamma radiation

100 EHz

A b s o

o n

Wavelength (nm)

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H. S. Bedi and Y. S. Bedi

5.3 Qualities ofLaser Light

A laser’s characteristic wavelength is associated with the energy gap between electrons in the ground state and electrons in the excited state.

Laser light is monochromatic—of one wavelength or colour (if within the visible light spectrum) [2, 3].

Laser light is coherent—this refers to the wave nature of light; the peaks and troughs occur synchronously or in phase.

Laser light is collimated—the light rays are parallel and nondiverging unlike conventional light sources that emit light in all directions. A laser is more powerful than ordinary light of the same power. If light from a 60W bulb enters the eye, it would not damage the retina. A collimated laser beam on the other hand is a focused, concentrated light and is damaging to the eye at much lower power.

5.4 Laser Tissue Interaction

When laser energy hits a biological tissue, it may be reected, scattered or absorbed. Light absorption has to take place for a biological effect to occur. The greater the degree of absorption, the greater the degree of transformation to heat. A given wavelength may be scattered by

one tissue and absorbed by another. The main light- absorbing components of tissue (chromophores) are haemoglobin, melanin, protein and water. Selecting a wavelength which is strongly absorbed by a chromophore present in a particular tissue will target that tissue. Visible and UV light is primarily absorbed by haemoglobin and melanin, respectively (Figs. 5.3 and 5.4), and infrared light is absorbed primarily by water. In general as the wavelength of light increases, so does the depth of penetration into skin. However, in the far infrared where water absorption dominates, the depth of penetration falls. Because of the strong absorption of water at 418, 542 and 577nm, depth of penetration is attenuated [4, 5].

5.5 Biological Eects ofLasers

Laser energy gets transformed into heat due to absorption of the photon energy. The intensity of the change depends on the laser wavelength and on the optical properties of the irradiated tissue. Changes in power settings and laser wavelength result in different temperature levels and thermal alterations [3]. There are three types of reactions when tissue reacts with laser energy: photothermal, photochemical and photoplasmal. For endovenous therapy, it is the photothermal which is of importance.

300

400 500 600 700 800 900 1000 1500 2000 3000 4000 5000

Ultraviolet

Fig. 5.3 The relationship of absorption vs wavelength for various lasers

Pulsed Dye

KTP

Nd:YAG

(1320nm)

Nd:YAG

(1064nm)

Diode

(1450nm)

Er:Glass

1540nm

Hemoglobin

Melanin

Water

Scatter

Mid InfraredNear Infrared

7500 10000

20000

10.000

The absorption coefficient of water at 1470nm is significantly higher than in the wavelength range of 810-1064nm.

5 Relevance ofWavelength inLaser Treatment ofVaricose Veins

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1.000

100

)

-1

Absorption (cm

0.1

0.01

0.001

Fig. 5.4 The absorption coefcient of water and water in relation to wavelength

Water

200 500

5.5.1 Photothermal

Hemoglobin

KTP

Wavelength (nm)

1470

Nd:YAG

Diode 980

1000

2000 5000 10000

depending on laser parameters; in most applica-

tions, however, only one specic effect is aimed Tissue chromophores absorb laser light and heat is generated. Depending on the duration and peak

at and a precise biological target can be thermally

damaged [2]. value of the temperature achieved, different effects like coagulation, vaporization, carbonization and melting may occur.

5.6 Wavelength

At tissue temperatures of 42–50 °C (hyperthermia), bond destruction and membrane alteration occur ending in necrosis if the hyperthermia lasts for several minutes. Beyond 50°C, enzyme activity is reduced, cell immobility occurs and cell repair mechanisms are disabled. At 60°C, there is denaturation of proteins and collagen leading to coagulation of tissue and necrosis of cells. At >80 °C, membrane permeability is increased. At 100 °C, there is vaporization of water molecules. Gas bubbles are formed inducing mechanical cell rupture and thermal decomposition (photoablation). At temperatures exceeding 100°C, carbonization occurs; beyond 300°C, melting can occur [3].

In general, the exact temperature for the onset of cell necrosis varies and is dependent on the temperature achieved and also on the duration. Quite often, several thermal effects are induced

Wavelength determines to some extent the effect of light energy on tissue. Erythema, hyperpigmentation and cutaneous cancer can be caused by light in the UV region (100–400 nm) which is invisible to the human eye. Light energy in the visible spectrum (380–700nm) is mostly innocuous but can be absorbed and cause thermal damage when delivered to the skin at high intensity. Light in the near-infrared (IR) region of the spectrum (780–3000nm), invisible to the human eye, causes skin and retinal injury [6].

The degree of absorption and its thermal effect on tissue vary with the amount and type of chromophores present. Different chromophores have different absorption coefcients. As laser is monochromatic and has narrow bandwidth, it permits selective targeting of chromophores [6].

Er:YAG

Ho:YAG

Energy Joules Power Watts Time seconds() () ()=´

Joule Watt/s= 1

()

())

H. S. Bedi and Y. S. Bedi

https://t.me/med1917

5.7 Quantication ofEnergy Delivered

Two parameters are used: Fluence and linear endovenous energy density (LEED).

Fluence is a unit of energy. The uence is the

Therefore, uence is the product of irradiance

and exposure time:

energy (in Joules) delivered per unit area.

FluenceJ/cmLaser power output Wexposure time seconds

Fluence denotes the energy per unit area for a single pulse. For a xed beam diameter and pulse duration, uence can be altered by changing the exposure time or the power.

The level of energy delivered (which will cause a proportional degree of damage) is dened as linear endovenous energy density (LEED). This is measured in reference to the length and diameter of the vein segment to be treated and is described in Joule per cm of vein [7]. The laser energy applied in relation to the irradiated surface is described as endovenous uence equivalent (EFE) given in Joule/cm2. For this parameter a cylindrical model of the vein segment is used, calculating the inner vein surface according to F=2×r×p×l, where r is the vein radius and l the length of the treated vein segment. Hence, it is important to note the following parameters for every treatment: vein diameter d (cm), length of the treated vein segment l (cm), laser wavelength λ (nm), laser power P (Watt), irradiation time t (s) or pull-back speed v (mm/s) for continuous pull- back. Only then will we be able to compare clinical results with different regimes.

Inappropriate results like non-occlusion or recanalization after ELT treatment are observed

sectional area cm

()

energy density [LEED]) was selected for analysis. However, to take into account also the diameter of the vein (a bigger vein should need more joules per centimetre than a smaller one), another unit was created—endovenous uence equivalent (EFE). This describes the amount of joules delivered per cm proven to be the unit that is statistically linked to a sustained GSV occlusion or an early recanalization after laser ablation [8].

Calculation of the inner surface of the GSV is done by a cylindrical approximation using the biggest diameter of the GSV measured while the patient is lying down. Testing of this unit was performed in a prospective series of GSV diode laser ablations, and it was found that a 100% occlusion rate and a recanalization rate of not more than 1% was possible during a 1-year follow- up period if an EFE of more than 20J/cm2 is delivered [10].

Even now it has not been possible to establish generally valid recommendations for appropriate energy density. Table 5.1 gives an overview of recommendations from a number of authors.

A recent trend has been observed towards recommendations for higher-energy density.

less when sufciently high-energy density is used—compared to lower LEED or EFE [8–15].

On the other hand, energy densities above a

Table 5.1 Recommendations for appropriate energy density for endovenous lasers

certain level can lead to side effects such as transmural ablation, perforations and alteration of perivenous tissue [16, 17].

5.8 Thermal Ablation: Energy Dosing

Earlier a unit with the dimension of joules per centimetre of vein length (called linear endovenous

Author Proebstle etal. [7] 940 23.6 13.0 Timperman etal. [9] 810/940 >80 n.d. Proebstle etal. [10] 940 n.d. 20.0 Kim [11] 980 32.7 9.82 Desmyttère etal. [12] 980 50–120 29–41 Kontothanassis etal.

[13] Vuylsteke etal. [14] 980 n.d. 52.0 Elmore etal. [15] 810 109.6 46.6

/laser beam cross

of inner vein wall surface, and it has

Wavelength (nm)

980 45–60 n.d.

LEED (J/cm)

EFE (J/cm2)

5 Relevance ofWavelength inLaser Treatment ofVaricose Veins

https://t.me/med1917

5.9 Pulse Duration (Pulse Width)

This is the time during which the laser power remains continuously above half its maximum value. Pulsed laser systems may be either longpulsed such as PDL (pulsed dye laser) with pulse durations ranging from 450 to 40ms or very short-pulsed (5–100 ns) such as the quality- switched lasers. The pulse duration controls the spatial connement of heat and should match the thermal relaxation time of the target. The thermal relaxation time is a measure of the cooling time of the target and is the time taken for the target to dissipate half of the incident thermal energy. Cooling time is related to the physical size of the target: the larger the target, the longer the thermal relaxation time. A pulse duration equal to or less than the thermal relaxation time of the target makes for reduced unwanted heat diffusion to adjacent tissue [18]. Extended pulse durations allow the delivery of higher uences of energy in a more gentle fashion. Greater uences enable treatment of veins that are larger and deeper inlocation. Also, the ability to deliver higher uences in the management of lower extremity vessels has produced more consistent and complete destruction of vessels, leading to more consistent results [2].

5.10 Pulse Repetition Rate

This is the number of emitted pulses per second (Hz). After one pulse, if the second comes before sufcient thermal diffusion into the surrounding tissues occurs, a pronounced temperature rise and thermal damage can occur. Even ultrashort laser pulses with pulse durations shorter than 100ps, each of them having no thermal effect, may add up to a measurable increase in temperature if applied at repetition rates higher than about 10–20Hz [18].

5.11 Diode Lasers

Diode lasers generate coherent monochromatic light through excitation of small diodes.

5.12 Nd:YAG Laser (1064nm)

A longer wavelength (e.g. the 1064-nm Nd:YAG laser) translates to a better penetration and a better absorption in deoxyhaemoglobin and the greater the sparing of the epidermis and a decreased melanin coefcient absorption.

5.13 Mode ofAction ofLasers

The mechanism of action of lasers is still not fully understood. Vein wall injury is mediated both by direct effect and indirectly via laserinduced steam generated by heating small amounts of blood within the vein. Proebstle etal. [19] showed that intravascular blood plays a key role for this evenly distributed thermal damage to the inner vein wall during EVLA.Microscopic studies showed that in saline-lled veins, EVLAinduced vessel wall injury was conned to the site of direct laser impact. In contrast, bloodlled veins exhibited thermal damage in more remote areas including the vein wall opposite to the laser impact. Lasers generate steam bubbles in blood and not in normal saline or plasma. Thus the thermal damage is caused by direct absorption of the laser light and also by indirect heating of the vein wall by endovenous steam bubble formation, causing occlusion of the vessel [20]. Many researchers however believe that the combined effects of vein spasm, compression by perivenous tumescent anaesthesia and ablation in the Trendelenburg position result in an ‘empty’ vein and direct thermal damage to the vein wall. Several histological studies show that intimal damage combined with discrete full-thickness perforations and relatively ‘normal’ intervening veins [21, 22] occurs along with direct damage of the vein wall structures due to direct contact between the laser tip and the vein wall [23].

Occlusion is completed by collagen remodelling and proliferation of broblasts involved in the restructuring and repair processes [17, 24]. Initial energy absorption by the small amount of residual blood (the chromophore) in the target vein occurs and then this sets off a chain of events that leads to carbonization along the vein wall [25].

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