physical methods used in dermatology

8/10/2019 Physical Methods Used in Dermatology

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PhysicalPhysical

Methods ofMethods ofDermatologicalDermatological

TherapyTherapyIhab Younis , M.D.

Professor of Dermatology & Andrology

Benha Faculty of Medicine

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CHAPTER 1 :

PH!!H"#APY I$ D"#MA!%Y

!he electromagnetic s'ectrum

Definition

It is a band of radiations arranged according to their wave lengths. The longest is radio waves

(used for radio and television transmission) and the shortest is the cosmic rays which are lethal to

humans but is prevented to reach the earth by the ozone layer. The arrangement of these

radiations according to their wavelength is as follows:

1- adio waves !- "icrowave #- Infrared rays $- %isible light

&- 'ltraviolet rays ('%) - -rays *- +amma rays ,- osmic rays

(isible light

This is the portion of solar energy that the human eye detects as light. hen scattered by a prism

it can be seen that it consists of colors starting with red (longest wave length) and ending with

violet (shortest wave length). Indigo is no longer considered a part of visible light

!he ultra)iolet rays

The name means /beyond violet/ (from 0atin ultra/beyond/). The 2un emits ultraviolet

radiation in the '%34 '%54 and '% bands4 but because of absorption in the atmosphere6s

ozone layer4 778 of the ultraviolet radiation that reaches the 9arth6s surface is '%3 (some of the

'% light is responsible for the generation of the ozone).

The range of '% wavelengths is often subdivided into '%3 (#,;#1& nm)4 also called 0ong

ave or /blac !, nm)4 also called 2hort ave or /germicidal/.

$.B.nm nanometer one billionth (1 ? 1 -7) of a meter.

Health concerns of *(

+ -in

'%34 '%5 and '% can all cause s


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0ontraindications for P*(A

Relative contraindications

-3ge 1! years or less as the long term side effects are not


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A5-'%54 similar to D'%3 therapy4 stimulates the dopa-negative4 melanocytes in the outer hair

root sheaths to proliferate4 produce melanin and migrate outward to adGacent depigmented s


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%A-"#- I$ D"#MA!%Y

The word laser is an acronym for %ight Amplification by the -timulated "mission of #adiation.

History

"aiman developed the first laser in 17. It was a ruby laser4 with a wavelength of 7$ nm. It

is from this prototype that today6s lasers are made. In 17$4 +oldman and ilson reported the

first cure of a basal cell carcinoma with ruby laser irradiation. 3lso4 in 17$ the argon andcarbon dio?ide lasers were developed. @uring the 17*s and 17,s the discovery of organic

dyes and heavy metals as active media led to the production of several new lasers.

Ho3 laser light is 'roduced9

hen atoms of a substance are e?posed to a strong energy source (e.g. a strong light) they

become e?cited i.e. they gain different levels of energy. 3toms eventually return to their previous

energy level4 upon returning to this level4 the e?cess energy is released in the form of a photon

i.e. a particle of light.

3 laser is a device that controls the way in which e?cited atoms release photons. In all types of

laser devices there is: 1) a source of intense flashes of light4 !) a lasing medium e.g. ruby4 which

is e?posed to intense light to get the atoms e?cited and #) reflecting mirrors to amplify the light.

Kig. 1: 0aser light

production

In a laser device the lasing medium is found in a tube that has a highly reflective mirror at one

end and a partially reflective mirror at the other end. hen the lasing medium is e?posed to the

intense light4 e?cited atoms are reflected by the highly reflective mirror so4 they collide with each

other producing more photons (stimulated emission) then they are reflected by the partially

reflective mirror at the other end of the tube. eflection between the two mirrors continues

permitting light to reflect bac< and forth4 building up in each passage (light amplification) until

laser light is emitted out from the partially reflective mirror (Kig.1).

Pro'erties of laser

1-It is coherent : an ordinary lamp will emit light waves in all directions but in lasers waves of

light are aligned with each other because they all have the same wave length (Kigs.!M#).

!- It is collimated: i.e. the light beams travel parallel to each other (concentrated light waves).

#- It is monochromatic: i.e. light waves are of a narrow band of wavelengths.

,

9?cited atoms

Kig.! : Crdinary non coherent lightKig.# : oherent light of laser


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These properties allow to deliver high-energy radiation of a specific wavelength to a small area.

-ome im'ortant definitions

1-Irradiance (power density): It is the power per unit area incident on the s


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and delays between pulses ranging from 1 to & milliseconds. The main advantage of ID0 is

the relatively cheaper price(less than &8 of laser machines).

%aser light interactions 3ith tissue

1-Photothermolysis interactions:This is determined by the theory of selective photothermolysis4

introduced by 3nderson and Darrish in 17,#4 that suggests that selective tissue absorption

of laser light leads to selective destruction of the absorbing tissue. 2


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particularly when treating patients with dar


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&- Dermanent s


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treatment of 5ec


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treatment involves a systemic allergic or localized granulomatous tissue reaction to tattoo ina'osi?s sarcoma

2tudies to date have shown that response rates with D@T are eFual to those with other therapeutic

modalities in Paposi6s sarcoma.

7-in metastases

The conclusion from various studies is that D@T is helpful to palliate initial small metastases of

breast cancer but is not suitable for the management of advanced or inflammatory carcinoma dueto low response rate and complications.

@ther a''lications

303 and "30 D@T with the 5lu-' or ID0 devices have been used for the treatment of

photoaging. 3lso4 though no controlled studies have been done4 topical 18 303 ointment

applied for & hours followed by irradiation with !& Jcm!from an incoherent light source showed

clearing of chronic plaFue psoriasis. Birsutism responded to D@T with the advantage that hair

follicle damage was highly selective and did not damage the adGacent dermis.

-ide effects

1. 3 burning sensation is observed during light e?posure after 303 or "30 application. This

sensation usually decreases rapidly once the light source is paused or e?posure is terminated.!. 3 phototo?ic reaction on 3Ps and 5 is characterized by erythema4 edema4 crusting4

vesiculation4 or erosion occurs in most patients. This is considered a normal and desirable

reaction to achieve clearance of these lesions. It lasts only a few days but sometimes can last

*-1 days.

#. Byperpigmentation is sometimes seen after D@T. It tends to fade over a few months.

Bypopigmentation at treated sites has also been reported.

$. ases of allergic contact dermatitis and urticaria to "30 have been reported.

Precautions

1. 2un e?posure on the treated lesion sites and peripheral s


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CHAPTER 4:

"%"0!#-*#"#Y I$ D"#MA!%Y

Definition

3 surgical procedure that uses high freFuency energy to cauterize4 coagulate or cut soft tissue.$.B.9lectrosurgery is often incorrectly referred to as electrocautery. 3lthough electrocautery is a

form of electrosurgery4 in electrocautery4 the electrode tip4 rather than human tissue4 serves as the

source of electrical resistance. In electrocautery4 the electrode tip becomes hot and can cause a

burn in tissue.

History

9gyptians # years ago used heat to treat tumors. In 1,,7 2ir Benry Thopson built the first

electrosurgery unit. In 17! ushing and 5ovie built a device that provided hemostatic and

cutting effects.

De)ices used

"odern devices (e.g. Byfrecator and 2urgetrone) use freFuencies more than & Bz.

KreFuencies less than that cause neuro-motor e?citability causing repeated muscular contractions

which may lead to tetany.

Mechanism of action

9lectrosurgical eFuipment converts domestic alternating current into high freFuency alternating

current. hen this current meets the high resistance of the s


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4."lectrocoagulation

9lectrocoagulation is ideal for clotting small blood vessels (less than ! to # mm in diameter) in

deep and superficial surgery. 'sually4 a !- to &-mm metallic sphere at the end of a treatment

electrode is the optimal tip for hemostasis of small vessels. These electrode tips can be directly

applied to the relatively dry surface of a surgical bed that has been momentarily compressed. The

current used is similar to electrodessication but the voltage4 freFuency4 and current damping are

all smaller4 while amperage is higher.

5."lectrosection

In electrosection4 the electrode is used to cut tissue. 3n electrode tip in the shape of a fine needle4

wire loop4 diamond4 ellipse4 or triangle is advanced slowly through the tissue4 causing a steam

envelope to advance around the tip and producing a smooth cutting effect with little sense of

pressure against the tissue by the operator. 3 high-voltage4 low-amperage4 high-freFuency

undamped current is used.

Indications for electrosurgery

%esions !echniue used

1-warts !-ondylomata #-"olluscum contagiosum$-2


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Ad)ices to the 'atient

V Oour wound may be tender 1-! hours after the curettage when the local anesthetic wears off.

V 0eave the dressing in place for !$ hours.

V 3void strenuous e?ertion and stretching of the area.

V Peep the wound dry for $, hours. If the wound becomes red or very painful4 consult your

doctor.

V The wound will ta


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CHAPTER 5 :

0#Y-*#"#Y I$ D"#MA!%Y

Definition

It is the destruction of s


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physical methods used in dermatology

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