Alexandre Carpentier

Blood-brain barrier, cytotoxic chemotherapies and glioblastoma.

ABSTRACT Introduction: Glioblastomas (GBM) are the most common and aggressive primary malignant brain tumors in adults. The blood brain barrier (BBB) is a major limitation reducing efficacy of anti-cancer drugs in the treatment of GBM patients. Areas covered: Virtually all GBM recur after the first-line treatment, at least partly, due to invasive tumor cells protected from chemotherapeutic agents by the intact BBB in the brain adjacent to tumor. The passage through the BBB, taken by antitumor drugs, is poorly and heterogeneously documented in the literature. In this review, we have focused our attention on: (i) the BBB, (ii) the passage of chemotherapeutic agents across the BBB and (iii) the strategies investigated to overcome this barrier. Expert commentary: A better preclinical knowledge of the crossing of the BBB by antitumor drugs will allow optimizing their clinical development, alone or combined with BBB bypassing strategies, towards an increased success rate of clinical trials.

1D multi-element CMUT arrays for ultrasound thermal therapy

Interstitial therapeutic ultrasound devices are a promising technology for performing thermal ablation in a wide variety of organs. In this study, the use of Capacitive Micromachined Ultrasound Transducers (CMUTs) for interstitial heating applications was investigated. CMUTs exhibit potential advantages for use in therapeutic ultrasound applications in comparison to standard piezo ultrasound transducer technologies as they have good characteristics in terms of miniaturization (cell size: few dozens of microns), bandwidth (several MHz) and high electro-acoustic efficiency. Two designs of CMUT arrays were studied: (1) a 1D 128-element planar-CMUT array originally dedicated to abdominal ultrasound imaging purposes (5u2005MHz, element size: 0.3 × 8.0 mm2); (2) a 12-element linear-array, 32.4-mm long and 0.8-mm wide, developed specifically for minimally-invasive interstitial therapeutic applications (6u2005MHz, element size: 2.7 × 0.8 mm2). Simulations were performed to evaluate the ability to generate thermal lesions...

MR-guided interstitial thermal therapy for the treatment of brain tumors with a multi-element ultrasound probe

In this work, a new therapeutic ultrasound device is presented that is designed for performing minimally invasive thermal ablation of brain tumors under guidance with magnetic resonance imaging (MRI). The device consists of an array of ultrasound transducers, oriented on multiple faces of a flexible sheath with an integrated cooling system that can be directly inserted into the brain through a small burr hole in the skull. Heating can be monitored using real-time MRI and conformed to the tumor volume by varying the power to the individual elements on the probe. In this work, preliminary testing of the device was performed and included acoustic characterization, numerical simulations, and experiments in a clinical MRI system. Numerical simulations of the acoustic field and temperature rise during heating were compared with results of in vitro testing using bovine brain samples. The results demonstrate that the device has good MRI compatibility and is capable of generating output surface intensities of grea...