Table 3.
Description of the parameters in PBM
| Parameters | Descriptions |
|---|---|
| Laser sources | Light sources can be classified into two categories: diode lasers and semiconductor lasers. Each type has distinct biological effects. Diode lasers emit coherent light with an uneven energy distribution from the center to the edge of the spot, while semiconductor lasers emit light energy that is evenly distributed throughout the spot. Diode lasers have greater penetration capabilities compared to semiconductor lasers; however, semiconductor lasers are more cost-effective and are advantageous for creating array laser sources. Depending on the specific research requirements, both diode and semiconductor lasers can be utilized effectively in experiments |
| Wavelength (nm) | Defined as the distance between two consecutive wave peaks, wavelength plays a significant role in determining the depth of penetration and biological effects of these waves. In the field of PBM, a wavelength range of 620–1270 nm is commonly chosen for its therapeutic benefits |
| Mode | Lighting modes are commonly classified into two categories: continuous and pulsed wave. In the continuous wave mode, the light source emits light continuously during the illumination process, whereas in the pulse wave mode, light emission occurs periodically according to a specific time wave. In this context, the frequency at which these pulses occur is referred to as the pulse frequency, measured in Hertz (Hz), while the duration of each pulse is known as the pulse width, measured in seconds (s). The duty cycle, which is the ratio of the total time of illumination to the total time, reflects the actual degree of illumination achieved. Typically, the pulse frequency ranges from 1 to 3000 Hz (Sommer et al. 2012). Research suggests that pulsed light may influence the electronic oscillations within nerve cells, potentially enhancing the opening or closing of ion channels(Kampa et al. 2004) |
| Power density (mW/cm2) | Power density is a crucial parameter that must be carefully considered in any application involving electromagnetic fields. It plays a significant role in determining the potential effects on living organisms, including modulation effects and the risk of tissue damage. Typically, power density levels are maintained within the range of 0.1–100 mW/cm2 to minimize the risk of thermal damage |
| Radiant exposure (J/cm2) | Radiant exposure serves as a crucial parameter in quantifying the accumulation of light energy on the surface of action. It is defined as the product of power density, which represents the amount of power per unit area, and the actual illumination time |
| Duration | The determination of illumination time stands as a pivotal parameter in experimental design, directly shaping the course of research endeavors. This factor, which encompasses both the number and duration of illuminations, exhibits remarkable flexibility, adapting to the unique demands of each study subject |
| Spot area (cm2) | The spot area is a crucial parameter that is often underestimated in its importance. Even with identical power levels, variations in spot area can lead to substantial differences in power density. Moreover, the size of the spot area directly influences the precision of PBM manipulation. In research involving rodents as experimental subjects, maintaining the spot diameter at the millimeter level is imperative. If the spot size is too large, multiple areas may inadvertently receive irradiation simultaneously, introducing a notable system bias due to the anatomical curvature of the irradiation point. This factor cannot be disregarded, as it may contribute to the diminished credibility of numerous experiments |
| Location | The location of illumination in a study can vary depending on the specific research objectives. Common areas for illumination include the head, limbs, chest, and abdomen. Researchers should carefully consider the purpose of their study when selecting the appropriate location for illumination to ensure accurate and reliable results |
| Distance (cm) | Distance refers to the space separating the light source from the subject, impacting the spot size and the thermal influence of the rising ambient temperature from the light source |