High-intensity focused ultrasound (HIFU) was first developed to ablate prostatic tissue
[1]. The ultrasound beam is focused at the focal point of the transducer and the energy
concentration produces tissue necrosis [2]. HIFU has also been used to ablate metastases on the surface of the liver either
surgically or via the transcutaneous approach [3]
[4]. However, beam reflection on gastric gas has produced necrosis of the interposed
abdominal wall [5]. An endoscopic device is potentially valuable in treating tumors localized near
to the gastric lumen without the difficulties of gas interposition. We developed an
endoscopic ultrasound (EUS) HIFU device. We report the first experience of the use
of HIFU to treat lesions completely endoscopically under EUS control.
We designed a miniaturized HIFU transducer with a 40-mm focal point, a working frequency
of 3.8 MHz, and an acoustic power of 35 W. We adapted it to fit onto an Olympus linear
echoendoscope ([Fig. 1]). To test this new device, a living pig model was chosen because of its similarity
to the human digestive anatomy.
Fig. 1 The endoscopic ultrasound (EUS) high-intensity focused ultrasound (HIFU) device:
a a three-dimensional (3-D) representation of the prototype; b a photograph of the final prototype.
The procedure was performed in two pigs that had been given general anesthetics. In
each pig, the stomach was initially filled with degassed water. The prototype was
then placed on a guide wire in the gastric lumen and focused onto the left lobe of
the liver under EUS control ([Fig. 2]). We applied 10 consecutive shots each of 10 seconds and with an effective acoustic
power of 35 W. This was repeated five times moving the scope 2 cm between each group
of shots. No bleeding or other complications occurred during the procedures.
Fig. 2 Endoscopic ultrasound (EUS) image highlighting the target zone within the liver.
The pigs were sacrificed immediately after the procedures. Examination showed that
we had achieved complete necrosis of the liver at the five sites with lesions in the
liver 10 mm in length and 8 mm in depth ([Fig. 3]). Only one of the five sites showed evidence of gastric mucosal erythema with whitening
of the external gastric wall but with no evidence of perforation or muscle wall damage.
The target zone appeared hypoechoic on the EUS endoscopy.
Fig. 3 Appearances at necropsy following endoscopic ultrasound (EUS)-guided high-intensity
focused ultrasound (HIFU) treatment showing: a the liver with five pale areas (within blue box) consistent with the treated zones;
b the cut surface of the liver indicating the depth of the lesions; c the surface of the gastric wall with an area of external whitening. d Endoscopic appearance of the gastric mucosa following HIFU treatment. Other lesions
correspond to the probe test at the beginning of the experiments.
We report for the first time the ability to make HIFU lesions on the liver with a
completely endoscopic procedure under EUS control with no immediate adverse effects.
Other possible targets that could be treated in this way include pancreatic tumors
or nodes.
This work was supported by a grant from the Agence Nationale de la Recherche (ANR)
through the Programme Blanc 2008.
Endoscopy_UCTN_Code_TTT_1AS_2AG
