Theoretical Analysis and Experimental Evaluation of Laser-Induced Interstitial Thermotherapy in Ex Vivo Porcine Pancreas

Abstract

Laser-induced interstitial thermotherapy (LITT) has been recently applied to pancreas in animal models for ablation purpose. Assessment of thermal effects due to the laser-pancreatic tissue interaction is a critical factor in validating the procedure feasibility and safety. A mathematical model based on bioheat equation and its experimental assessment was developed. The LITT procedure was performed on 40 ex vivo porcine pancreases, with an Nd:YAG (1064 nm) energy of 1000 J and power from 1.5 up to 10 W conveyed by a quartz optical fiber with 300 μm diameter. Six fiber Bragg grating sensors have been utilized to measure temperature distribution as a function of time at fixed distances from the applicator tip within pancreas undergoing LITT. Simulations and experiments show temperature variations Δ T steeply decreasing with distance from the applicator at higher power values: at 6 W, ∆T > 40 °C at 5 mm and Δ T is approximately equal to 5 °C at 10 mm. Δ T nonlinearly increases with power close to the applicator. Ablated and coagulated tissue volumes have also been measured and experimental results agree with theoretical ones. Despite the absence of data in the current literature on pancreas optical parameters, the model allowed a quite good prediction of thermal effects. The prediction of LITT effects on pancreas is necessary to assess laser dosimetry.

Characterization of fiber optic distributed temperature sensors for tissue laser ablation

“…1, in case of temperature gradients this simple relation provides a rough underestimation of the actual temperature along the grating length.This is particularly limiting in LITT since large temperature gradients due to the localized absorption of the laser beam or the presence of blood vessels could originate local underestimations, with subsequent risk of unpredicted carbonizations [15], [16]. III.…”

Magnetic resonance-based thermometry during laser ablation on ex-vivo swine pancreas and liver

“…Indeed, the variation of λ B , λ B , can be caused by both fiber strain, ε, and temperature variation, T. During LA, the errors introduced by the FBG strain are negligible [5], and FBG can sense only temperature changes, as in Eq. (5)…”

“…Since 2010, the research group led by Di Matteo et al investigated the use of LA for pancreatic cancer treatment [4,5]. The choice to focus on pancreas is motivated by the high mortality, the complexity and invasiveness of the current common treatment of pancreatic cancer (i.e., Whipple procedure [6]), which usually requires an open surgical access to reach the gland.…”

“…Several thermometric techniques were investigated along the last 30 years [7]. These techniques can be divided into two categories: the invasive ones, including thermocouples [8], thermistors, and fiber optic sensors (fluoroptic sensors and fiber Bragg grating, FBG, sensors [5]); and the non-invasive ones, based on medical imaging techniques (e.g., magnetic resonance -MR-, computed tomography -CT- [9] and ultrasound based thermometry [10]). …”

The evaluation of the influence of laser treatment parameters on the type of thermal effects in the surface layer microstructure of gray irons

“…Lasers are widely used in many fields, for example in medicine (for example dentistry, or cancer recognition and treatment) analytical chemistry, bioanalysis, agricultural and environmental applications, for monitoring of air and water quality, vegetation, in atomic and molecular spectroscopy, interferometry, in development of frequency standards, metrology, holography, cryptography, telecommunication, in atomic optics, space and defense applications [1][2][3][4][5].…”