IEEE Robotics & Automation Magazine - September 2023 - 90

plastic, multiwell plate. The well plate had an opening in the
bottom to avoid wave reflection.
THERMAL ABLATION
EXPERIMENTAL PROTOCOL
For each test, the center of the sample was selected as the target
through the HIFUSK GUI. The HIFU lesion parameters-intensity,
duration, and duty cycle-were set at 156 W,
10 s, and 90%, respectively, to obtain a thermal lesion [23].
Sonication was executed, and the sample was then sectioned
to measure the lesion length (D) and width (d) with a
digital caliper (0.01-mm resolution; RS Components). The
volume (V) of the generated cigar-shaped lesion was computed
according to (5), approximating it with a symmetrical
ellipsoid:
Vd .D
3
= 4 2r
(5).
RESULTS
Figure 8 conveys the median value of the thermal lesion
width (d), length (D), and volume (V) in static and dynamic
conditions. Although slightly higher data variability can be
noticed in the dynamic case, high similarity can be appreciated
between the results obtained in the static condition
and in the dynamic condition, where the motion compensation
algorithm was applied. Due to the low number of analyzed
samples, the data were compared using the
nonparametric Wilcoxon rank sum test. No statistically significant
difference was found between the static and
dynamic cases for all three parameters (d, D, and V). Thus,
the accuracy of the implemented motion compensation
strategy was demonstrated on ex vivo tissue, confirming
the HIFUSK platform's capability of thermally ablating
static and dynamic targets.
IN VIVO VALIDATION
A first in vivo experiment was conducted on a porcine model
that well resembled human anatomy and pathophysiology
[28]. This in vivo testing aimed at demonstrating 1) the
HIFUSK platform's usability in a clinical environment, 2) the
platform's ability to perform tracking on real moving organs,
and 3) the safety and efficacy in performing USgHIFU treatments
in vivo by using a robotic platform. The protocol for in
vivo preclinical studies was approved by the Italian Ethical
Committee in May 2020 (protocol 65E5B.48; authorization
434/2020-PR).
EXPERIMENTAL SETUP
The in vivo test was conducted at the " Centro di Biomedicina
e Sperimentale di S. Cataldo " Animal Center, Pisa, Italy,
under the supervision of a physician with experience in
USgHIFU treatments and a veterinary expert to take care of
the animal health conditions throughout the experiment.
The liver was selected as the target organ to perform the
HIFU treatment.
90 IEEE ROBOTICS & AUTOMATION MAGAZINE SEPTEMBER 2023
Experimental Setup
Quantitative Lesion Evaluation
Therapeutic Device
6.5
6
5.5
5
Chicken Breast Sample
(a)
4.5
Static Dynamic
12
11.5
11
10.5
10
9.5
Static Dynamic
(b)
1,700
1,600
1,500
1,400
1,300
Chicken Breast Lesion
Dimension d
Static Dynamic
Static
Dynamic
(c)
FIGURE 8. (a) The experimental setup used for the HIFUSK platform ex vivo validation. (b) The lesion width (d ), length (D), and volume (V ) for both static (green) and dynamic (purple)
conditions. (c) The representative chicken breast thermal lesions obtained in static and dynamic conditions.
Dimension D
Dimension d (mm)
Dimension D (mm)
Volume V (mm3)
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