Electrotherapy (LEC-2) PDF

# Electromagnetic Radiation (EMR) ## Radiation - Is energy that travels and spreads out as it goes ## Electromagnetic radiation (EMR) - Composed of electric and magnetic fields that are oriented perpendicular to each other and to the direction of radiation. - It covers a broad spectrum of wave...

# Electromagnetic Radiation (EMR) ## Radiation - Is energy that travels and spreads out as it goes ## Electromagnetic radiation (EMR) - Composed of electric and magnetic fields that are oriented perpendicular to each other and to the direction of radiation. - It covers a broad spectrum of wavelengths and frequencies. ## Electromagnetic spectrum - A range of EMR frequencies and wavelengths. ## Electromagnetic wave production - Steps: - Electrical and chemical forces induce a specific material with a specific wavelength. - This forces the electrons which are currently in their ground state to a higher energy level, i.e., the material is now in the excited state. - As the electrons return to their lower energy state, they release a pulse of EMR called a "photon". - The wavelength or frequency of the photon depends on the gap in energy between the two orbit levels. ## Characteristics of EMR 1. All EMR travels at a constant speed of 300,000,000 m/s in a vacuum (the speed of light). 2. EMR does not require a medium to travel. 3. EMR is a transverse wave capable of reflection, absorption, and refraction, depending on the medium. 4. EMR always travels in straight lines. 5. EMR is classified based on wavelength and frequency. ## Wavelength and Frequency - **Wavelength**: The horizontal distance between two adjacent wave peaks. - **Frequency**: The number of complete waves or cycles that pass a point in one second, measured in Hertz. - The speed of light is equal to the product of wavelength and frequency. - The radiant energy is directly proportional to frequency and inversely proportional to wavelength. ## Ionizing vs. Non-ionizing EMR - **Ionising EMR**: - High frequency radiation. - Examples: X-rays and gamma rays. - Has the capability of breaking molecular bonds easily. - Can penetrate cell tissue and disseminate energy within the cell. - High energy can disrupt cell division and destroy cells. - Used at small doses and intervals for medical purposes, such as diagnostic X-rays and therapeutic cancer treatment. - **Non-ionizing EMR**: - Low-frequency radiation. - Examples: Radiowaves, microwaves, infrared, ultraviolet, and visible light. - Cannot break molecular bonds. - Has more therapeutic applications than ionizing EMR. - Does not damage cells or tissue, unlike ionizing EMR which can destroy tissue or kill the cell. ## Physical Laws Governing the Effects of EMR 1. **Reflection**: The return of an EM wave from an object. - The angle of incidence is equal to the angle of reflection. - Reflection depends on: - The amount of radiation - The angle of incidence - The nature of the surface 2. **Refraction**: The change in direction of an EMR wave when passing from a medium of one density to a medium with a different density. - Refraction depends on: - The media involved - The angle of incidence - EMR that falls at a 90-degree angle does not reflect or refract, and has a high effective energy. 3. **Absorption and Penetration**: When EMR passes through a medium, some of it is absorbed, and the rest penetrates the medium. - The amount of absorption and penetration depends on: - The wavelength and frequency - The nature and type of tissue - The angle of incidence - The nature of the medium - The intensity of radiation. 4. **Scattering**: When EMR travels through a non-homogenous medium, the wavelength is scattered. - Longer wavelengths scatter less than shorter wavelengths. 5. **Inverse Square Law**: Relates the source's radiant energy to the distance between the source and the tissue. - Energy received by tissue is inversely proportional to the square of the distance between the source and the tissue. 6. **Cosine Law**: The radiant energy is directly proportional to the cosine of the angle of incidence. 7. **Arndt-Shulz Law**: A minimum intensity of EMR is required to initiate a biological process. - This law explains that a certain amount of EMR is needed to initiate a physiological change. 8. **Grotthus-Draper Law**: If the energy is not absorbed in the superficial tissue, it will penetrate deeper. - This law explains that higher frequency, shorter wavelengths are absorbed more in the superficial levels than deeper levels. ## Examples of EMR Modalities - Short-wave diathermy - Light therapy - Infrared radiation - Ultraviolet radiation phototherapy - Low-power laser ## Contraindications of EMR 1. Pregnancy 2. Pacemakers 3. Recent deep X-ray therapy 4. Metastasis and malignancy 5. Metal implants