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Research Papers

A Needlelike Probe for Temperature Monitoring During Laser Ablation Based on Fiber Bragg Grating: Manufacturing and Characterization

[+] Author and Article Information
Davide Polito

Mem. ASME
Research Unit of Measurements and
Biomedical Instrumentation,
Via Álvaro del Portillo 21,
Rome 00128, Italy
e-mail: davidepol@hotmail.it

Michele Arturo Caponero

Mem. ASME
ENEA,
Photonics Micro and Nano structures Laboratory,
Research Centre of Frascati,
Via Enrico Fermi 45,
Frascati 00044, Rome, Italy
e-mail: michele.caponero@enea.it

Andrea Polimadei

Mem. ASME
ENEA,
Photonics Micro and Nano structures Laboratory,
Research Centre of Frascati,
Via Enrico Fermi 45,
Frascati 00044, Rome, Italy
e-mail: andrea.polimadei@enea.it

Paola Saccomandi

Mem. ASME
Research Unit of Measurements and
Biomedical Instrumentation,
Via Álvaro del Portillo 21,
Rome 00128, Italy
e-mail: p.saccomandi@unicampus.it

Carlo Massaroni

Mem. ASME
Research Unit of Measurements and
Biomedical Instrumentation,
Via Álvaro del Portillo 21,
Rome 00128, Italy
e-mail: c.massaroni@unicampus.it

Sergio Silvestri

Mem. ASME
Research Unit of Measurements and
Biomedical Instrumentation,
Via Álvaro del Portillo 21,
Rome 00128, Italy
e-mail: s.silvestri@unicampus.it

Emiliano Schena

Mem. ASME
Research Unit of Measurements and
Biomedical Instrumentation,
Via Álvaro del Portillo 21,
Rome 00128, Italy
e-mail: e.schena@unicampus.it

1Corresponding author.

Manuscript received November 19, 2014; final manuscript received April 24, 2015; published online August 6, 2015. Assoc. Editor: Rupak K. Banerjee.

J. Med. Devices 9(4), 041006 (Aug 06, 2015) (8 pages) Paper No: MED-14-1273; doi: 10.1115/1.4030624 History: Received November 19, 2014

Temperature distribution monitoring in tissue undergoing laser ablation (LA) could be beneficial for improving treatment outcomes. Among several thermometric techniques employed in LA, fiber Bragg grating (FBG) sensors show valuable characteristics, although their sensitivity to strain entails measurement error for patient respiratory movements. Our work describes a solution to overcome this issue by housing an FBG in a surgical needle. The metrological properties of the probes were assessed in terms of thermal sensitivity (0.027 nm °C−1 versus 0.010 nm °C−1 for epoxy liquid encapsulated probe and thermal paste one, respectively) and response time (about 100 ms) and compared with properties of nonencapsulated FBG (sensitivity of 0.010 nm °C−1, response time of 43 ms). The error due to the strain caused by liver movements, simulating a typical respiratory pattern, was assessed: the strain induces a probes output error less than 0.5 °C, which is negligible when compared to the response of nonencapsulated FBG (2.5 °C). The metallic needle entails a measurement error, called artifact, due to direct absorption of the laser radiation. The analysis of the artifact was performed by employing the probes for temperature monitoring on liver undergoing LA. Experiments were performed at two laser powers (i.e., 2 W and 4 W) and at nine distances between the probes and the laser applicator. The artifact decreases with the distance and increases with the power: it exceeds 10 °C at 4 W, when the encapsulated probes are placed at 3.6 mm and 0 deg from the applicator, and it is lower than 1 °C for distance higher than 5 mm and angle higher than 30 deg.

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References

Figures

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Fig. 1

Chain of measurement for the calibration process. (a) optical spectrum analyzer, (b) PC for recording wavelengths, (c) oven, (d) thermocouple module for the acquisition of temperature, and (e) PC for recording temperature data.

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Fig. 2

(a) Schematic drawing of the needlelike probe such as the orientation of FBG with respect to the axis of the needle; (b) picture of one needlelike probe; (c) schematic representation of the top view of the polymeric mask; the holes designed to insert the thermocouples during the experiments and their relative positions with respect to the applicator are shown; and (d) ex vivo swine liver undergoing Nd:YAG laser LA placed in the polymeric mask: (1) FBG sensor in metallic needle, fixed by thermal paste; (2) FBG sensor in metallic needle, fixed by liquid epoxy adhesive; and (3) quartz laser applicator

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Fig. 3

Comparison of the calibration curves of the sensor: (a) with liquid epoxy adhesive (gray curve) and (b) paste (black curve)

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Fig. 4

Comparison between the step responses of the three FBG sensors: dotted line (nonencapsulated FBG), dashed-dotted line (probe manufactured using thermal paste), and continuous line (probe manufactured using epoxy adhesive)

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Fig. 6

Zoom of one treatment: (a) temperature measured by encapsulated FBG and (b) temperature measured by nonencapsulated FBG. The technique employed to evaluate the artifact after 2 s of laser-on and after 2 s of laser-off.

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Fig. 5

Temperature trend in liver undergoing ten consecutive laser-on and laser-off, simultaneously measured: (a) by needlelike with epoxy adhesive (gray line) and (b) nonencapsulated FBG (black line)

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Fig. 8

Error caused by liver displacement during ten simulated adult quiet breathing. Dashed line: error experienced by the nonencapsulated FBG; dotted line: error experienced by the FBG encapsulated by thermal paste; and continuous line: error experienced by the FBG encapsulated by epoxy adhesive.

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Fig. 7

Artifact amplitude and temperature change (ΔT) at the different positions (distance, d, and angle, θ, with respect to the applicator tip) and at the two laser powers for needlelike probe encapsulated with thermal paste, and for the one encapsulated with epoxy adhesive

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