Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia with high laser power.
The purpose of this study was to validate the feasibility of photoactive dye injection to enhance light absorption
and eventually to facilitate tissue ablation with low laser power. The experiment was implemented on chicken
breast due to minimal optical absorption Amaranth (AR), black dye (BD), hemoglobin powder (HP), and
endoscopic marker (EM), were selected and tested in vitro with a customized 532-nm laser system with radiant
exposure ranging from 0.9 to 3.9 J/cm2. Light absorbance and ablation threshold were measured with UV-VIS
spectrometer and Probit analysis, respectively, and compared to feature the function of the injected dyes.
Ablation performance with dye-injection was evaluated in light of radiant exposure, dye concentration, and
number of injection. Higher light absorption by injected dyes led to lower ablation threshold as well as more
efficient tissue removal in the order of AR, BD, HP, and EM. Regardless of the injected dyes, ablation
efficiency principally increased with input parameter. Among the dyes, AR created the highest ablation rate of
44.2±0.2 μm/pulse due to higher absorbance and lower ablation threshold. Preliminary tests on canine prostate
with a hydraulic injection system demonstrated that 80 W with dye injection yielded comparable ablation
efficiency to 120 W with no injection, indicating 33 % reduced laser power with almost equivalent performance.
In-depth comprehension on photoactive dye-enhanced tissue ablation can help accomplish efficient and safe
laser treatment for BPH with low power application.
The feasibility of photoacoustic imaging (PAI) application was evaluated to map punctured blood vessels thermally treated by high-intensity focused ultrasound (HIFU) for hemostasis. A single-element HIFU transducer with a central frequency of 2.0 MHz, was used to induce thermal hemostasis on the punctured arteries. The HIFU-treated lesion was imaged and localized by high-contrast PAI guidance. The results showed that complete hemostasis was achieved after treatment of the damaged blood vessels within 25 to 52 s at the acoustic intensity of 3600 W/cm2. The coagulation time for the animal artery was ∼20% longer than that of the phantom possibly due to a lower Young’s modulus. The reconstructed PA images were able to distinguish the treated area from the surrounding tissue in terms of augmented signal amplitudes (up to three times). Spectroscopic studies demonstrated that the optimal imaging wavelength was found to be 700 nm in order to reconstruct high-contrast photoacoustic images on HIFU-treated lesions. The proposed PAI integrated with HIFU treatment can be a feasible application to obtain safe and rapid hemostasis for acute arterial bleeding.
High Intensity Focused Ultrasound (HIFU) technology provides a feasible method of achieving thermal coagulation during surgical procedures. One of the potential clinical benefits of HIFU can induce immediate hemostasis without suturing. The objective of this study was to investigate the efficiency of a HIFU system for blood coagulation on severe vascular injury. HIFU treatment was implemented immediately after bleeding in artery. The ultrasound probe was made of piezoelectric material, generating a central frequency of 2.0 MHz as well as an ellipsoidal focal spot of 2 mm in lateral dimension and 10 mm in axial dimension. Acoustic coagulation was employed on a perfused chicken artery model in vitro. A surgical incision (1 to 2 mm long) was made with a scapel on the arterial wall, and heparinized autologous blood was made to leak out from the incision with a syringe pump. A total of 5 femoral artery incisions was treated with the HIFU beam. The intensity of 4500 W/cm2 at the focus was applied for all treatments. Complete hemostasis was achieved in all treatments, along with the treatment times of 25 to 50 seconds. The estimated intraoperative blood loss was from 2 to 5 mL. The proposed HIFU system may provide an effective method for immediate blood coagulation for arteries and veins in clinical applications.