A three-dimensional transient computational study of 532-nm laser thermal ablation in a geometrical model representing prostate tissue

Figures & data

Table 1. Limitations of previous laser ablation models.

Model	Limitations
McKenzie [18]	One-dimensional, steady state, and no scattering
Partovi et al. [19]	Steady state, no precise scattering
Venugopalan et al. [20]	One-dimensional, steady state, and no scattering
Majaron et al. [21]	One-dimensional, sub-ablative, and no scattering

Figure 1. Schematic diagram showing the set-up for simulating Greenlight^TM laser tissue ablation process.

Figure 2. The axisymmetric computational control volume that is used in the model and showing heat fluxes and heat generation.

Table 2. Values of the parameters that were used in the computational model [25–28].

Property/parameter	Value
Average density	ρ = 1000 kg m^−3
Thermal conductivity	k = 0.6 W m^−1 K^−1
Specific heat capacity	cp = 4187 J kg^−1 K^−1
Latent heat of vaporization	Lv = 2.27*10^6 J kg^−1
Vaporization temperature	Tv = 100 °C
Energy of ablation	habl = 2.7 *10^6 J m^−3
Absorption coefficient	µa = 1 cm^−1
Scattering coefficient	µs = 100 cm^−1
Anisotropy factor	g = 0.9

Table 3. The values of laser parameters employed in the computational model.

Results	Pulse duration	Pulse frequency (Hz)	Power (W)
Figure 5	CW	CW	50
Figure 6	100 ns, 100 µs, and CW	10, 100, and CW	10
Figure 7	100 ns, 100 µs, and CW	10, 100, and CW	100
Figure 8	CW	CW	10, 20, 30, 40, 50, 60, 70, 80, 90, 100, and 125

Figure 3. Validation of the computational model against analytical and experimental results. (A) temperature profile of analytical and computational models, (B) tissue front position of analytical and computational models, and (C) Ablation area obtained experimentally and from the computational model [9].

Figure 4. Light energy density (J cm ^{− 2}) distribution in a tissue after irradiating by laser pulse of 1 J cm ^{− 2} fluence and 0.5 mm spot radius. (A) Distribution prior to ablation crater had formed. (B) Distribution after ablation crater had formed.

Figure 5. Longitudinal sections showing model predicted evolving temperature profile and ablation crater resulting from irradiation by a 50 W CW laser at times of: (A) 25 ms, (B) 250 ms, (C) 0.5 s, (D) 1 s, (E) 2 s, (F) 3 s.

Figure 6. Tissue laser ablation outcomes evaluated in terms of (A) coagulation depth and (B) ablation rate after irradiating with 10 W CW mode and pulsed mode lasers at selected pulse durations and pulse frequencies.

Figure 7. Tissue laser ablation outcomes evaluated in terms of (A) coagulation depth; (B) coagulation zone thickness; and (C) ablation rate after irradiating with 100 W CW mode and pulsed mode lasers at selected pulse durations and pulse frequencies.

Figure 8. Tissue laser ablation outcome evaluated in terms of (A) coagulation zone thickness and coagulation depth, (B) ablation rate (C) steady-state ablation rate, and (D) ablation depth after irradiating with CW mode laser using different power settings.

McKenzie AA. A three-zone model of soft-tissue damage by a CO2 laser. Phys Med Biol. 1986;31:967–983.

 PubMed Web of Science ®Google Scholar

Partovi F, Izatt J, Cothren R, et al. A model for thermal ablation of biological tissue using laser radiation. Lasers Surg Med. 1987;7:141–154.

 PubMed Web of Science ®Google Scholar

Venugopalan V, Nishioka NS, Mikic BB. The effect of laser parameters on the zone of thermal-injury produced by laser-ablation of biological tissue. J Biomech Eng. 1994;116:62–70.

 PubMed Web of Science ®Google Scholar

Majaron B, Plestenjak P, Lukac M. Thermo-mechanical laser ablation of soft biological tissue: modeling the micro-explosions. Appl Physics B Lasers Optics. 1999;69:71–80.

 Web of Science ®Google Scholar

Elkhalil H, Akkin T, Pearce J, et al. Potassium titanyl phosphate laser tissue ablation: development and experimental validation of a new numerical model. J Biomech Eng. 2012;134:101002.

 PubMed Web of Science ®Google Scholar