Lowlevel laser therapy for treating myofascial pain syndromes

Low-level laser therapy for treating myofascial pain syndromes of vertebral genesis • mechanisms of therapeutic effects of low-level laser irradiation • types of low-level laser therapy • low-level laser dosing and its methodology

Mechanisms of laser interaction with biotissues are usually studied in two directions: • Evaluation of physiological reactions to laser light • Search for the primary acceptor with which light photon interacts

1. Biological effects caused by laser irradiation are seen in all spectrum ranges 2. Biological effects caused by laser irradiation are dose-dependent

Dependence of biological reactions on the dosage of low-level laser irradiation

The sun spectrum outside the atmosphere (a) and at the Earth surface (b)

Asimov M. M. , Asimov R. M. , Rubinov A. N. , Mamilov S. A. , Plaksiy Ytt. S. Stimulation of aerobic cell metabolism by low energy laser irradiation. Journal “Lazernaja medicina”, vol 11, No 2, 1977

Types of low-level laser therapy By the location: 1) external contact distant 2) internal intracavital intravascular 3) combined Tactical aims of laser light impacts • Irradiation of myofascial painful zones • Irradiation of reflexive zones and acupuncture points. • Irradiation of the projection of inner organs • Irradiation of the projection of vascular and nervous bundles • Others (stimulation of the proliferative neuron activity, local control of oxyhemoglobin dissociation)

Depth of penetration of various spectral wavelengths into the skin

Irradiation power Energetic characteristics of the electromagnetic irradiation (Unit of measurement in SI – Wt) Energy (dose) Power of electromagnetic wave generated in one time unit (Unit of measurement in SI - J or Wt. sec. ) Energy density (dose density) Basic unit for measuring laser impact. (Unit of measurement in SI - J/m 2. In practice we use J/cm 2 ) Dose density is calculated by the equation: D= P·T/S [Wt·sec/ cm 2] Where: D - dose density Power – average irradiation power T - exposure time S- irradiation area

Equation for calculating the dose of laser impact D= P·T/S [Wt·sec/ cm 2] D = Paverage T S D = Ppuls T τ0. 5 S D = P T (1 – p(λ)) τ0. 5 S H D –Energy of the absorbed dose, J/cm 2 P – Power of the pulse irradiation, Wt T –Exposure time, sec p( ) –Skin reflection coefficient= 0, 38 - Pulse frequency, Hz - Laser pulse duration, sec S- Irradiation area, cm 2 D –Absorbed energy dose J/cm 2 P –Pulse power at the given depth, Wt T –Exposure time, sec p( ) –Skin reflection coefficient = 0. 38 -Pulse frequency, Hz - Laser pulse duration, sec S –Target area, cm 2 H- Target depth

Laser light power (0. 89µm) depending of the depth of penetration into soft tissues (µ=1. 84) H cm 0, 00 0, 50 1, 00 1, 50 2, 00 2, 50 3, 00 5 Wt 5, 00 1, 95 0, 79 0, 30 0, 13 0, 05 0, 02 10 Wt 10, 00 3, 91 1, 58 0, 60 0, 25 0, 10 0, 04 60 Wt 60, 00 23, 44 9, 48 3, 60 1, 50 0, 60 0, 24 100 Wt 100, 0 39, 1 5, 8 6, 0 2, 5 1, 0 0, 4

Examples of calculations Pulsed power – 5 Wt Pulse frequency – 3000 Hz Pulse duration – 0. 0000001 sec Irradiation area – 1 cm 2 Exposure – 60 sec Reflection coefficient – 0. 37 D = P T (1 – p(λ)) τ0. 5 S • Superficial dosing depending of the absorbed dosage is: 5 x 60 x(1 -0, 38)x 3000 x 0. 0000001=0. 056 J/cm 2 • Pulsed power at 3 -cm depth - 0. 02 Wt Dosing at this depth depending of the absorbed dosage is about: 0, 02 x 60 x 3000 x 0, 0000001 = 0, 0004 Дж/см 2. • To get dosage 0. 056 J/cm 2 at 3 -cm depth and on 1 cm 2 area the exposure time must be 140 minutes (!). • At pulsed power 60 Wt a tissue layer located at 3 -cm depth gets 0. 24 Wt and the necessary exposure time is 0. 56/0. 24 x 3000 x 0. 0000001=777 sec (14 min) • Dosage on the skin under such conditions will be 60 x 777 x 0. 68 x 3000 x 0. 0000001=8. 7 J/cm 2