**10. Time period estimation**

The temperature elevation in the irradiated tissues could be estimated easily related to the SAR calculations owing to Eq. (1). It is noticed from this equation that the temperature elevation in the tissue is depending mainly on the time period of exposing to NAs for a certain SAR, so the time period should be selected carefully to verify the wanted temperature for tumor cells killing.

### **10.1 Time period estimation in tumor tissue at single nano-antenna**

The main goal of the treatment of the tumors is the temperature rise over the normal level to cause cells damage which could be estimated by (60°C). **Table 2**

#### **Figure 4.**

*The calculated SAR in the proposed tumor tissue exposed to a single NA at 532 nm for different distances. (a) 100 nm, (b) 200 nm, (c) 300 nm, and (d) 400 nm.*

#### **Figure 5.**

*Specific absorption rate as a function of the distance from the tissue at single unit for 532 nm.*

*Plasmonic Optical Nano-Antenna for Biomedical Applications DOI: http://dx.doi.org/10.5772/intechopen.105458*

**Figure 6.**

*The calculated SAR in the proposed tumor tissue subjected to single NA at 1064 nm at different distances (a) 100 nm, (b) 200 nm, (c) 300 nm, and (d) 400 nm.*

**Figure 7.**

*The specific absorption rate as a function of the distance from the proposed tissue at 1064 nm for single unit.*

represents the time period estimation to attain the required temperature in the proposed tumor tissue for single NA at two wavelengths (532 and 1064) nm for different distances (100, 200, 300 and 400) nm from the tissue. It is clear that the time period is shorter for closer distance from the tissue for both wavelengths while it shortest for

#### *Plasmonic Nanostructures - Basic Concepts, Optimization and Applications*


#### **Table 2.**

*The calculation of the time period in the proposed for distances (100, 200, 300 and 400) at two wavelengths (532 and 1064) nm for single nano-antenna.*

longer wavelength (1064 nm). It is observed from the results that the time period is varied related to the field distribution in the tissue and how much regular and hence for SAR calculation.

It is worth to mention that the short time period is quite important in the treatment of the diseased tumor cells because of the generated heat does not dissipated to the surrounding healthy tissues, for this reason the calculated time period in this study does not possible unless using the laser either in pulse mode or in chopped mode.

The optical plasmonic nanoantenna proves high ability to destruct the tumor tissues especially the cancer cells due to those antennas are considered as a hot point source which means that the desired tissue could be destroyed without affecting the surrounding healthy tissues. Our purpose is to estimate the thermal distribution in the tissue at different distances from the nanoantenna. The bow tie shape of plasmonic nanoantenna is selected because in the sharp tip the group and phase velocities of surface plasmonic waves decreases with the distance of propagation and finally become zero. The generated field could be enhanced several order of magnitude in the gap, so the gap width should be selected accurately. The calculated results of the SAR proved that the best value is the closest to the tissue which causes to the higher temperature generated in it, knowing that the resonance wavelength is varied related to every distance and does not represent the best.

The maximum temperature generated in the tissue under the influence of optical plasmonic bow tie nanoantenna is detected at a distance of 100 nm, which gives a clear indication that the distance from the tissue affects on the distribution field in the tissue and hence on the temperature elevation.
