François Cotton

Management of Respiratory Motion in Extracorporeal High-Intensity Focused Ultrasound Treatment in Upper Abdominal Organs: Current Status and Perspectives

Extracorporeal high-intensity focused ultrasound (HIFU) is a minimally invasive therapy considered with increased interest for the ablation of small tumors in deeply located organs while sparing surrounding critical tissues. A multitude of preclinical and clinical studies have showed the feasibility of the method; however, concurrently they showed several obstacles, among which the management of respiratory motion of abdominal organs is at the forefront. The aim of this review is to describe the different methods that have been proposed for managing respiratory motion and to identify their advantages and weaknesses. First, we specify the characteristics of respiratory motion for the liver, kidneys, and pancreas and the problems it causes during HIFU planning, treatment, and monitoring. Second, we make an inventory of the preclinical and clinical approaches used to overcome the problem of organ motion. Third, we analyze their respective benefits and drawbacks to identify the remaining physical, technological, and clinical challenges. We thereby consider the outlook of motion compensation techniques and those that would be the most suitable for clinical use, particularly under magnetic resonance thermometry monitoring.

Acute Headache Followed by Focal Neuropsychological Impairment in Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL)

Occasionally, patients with Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL) present atypical features such as confusion, coma, or nonconvulsive status epilepticus. Acute focal neuropsychological syndrome revealing the disease has been poorly documented. We report the atypical presentation of two patients in whom CADASIL was revealed by an episode of headache followed by focal neuropsychological impairment.

Diffusion Tensor Imaging Tractography Detecting Isolated Oculomotor Nerve Damage After Traumatic Brain Injury

A 24-year-old woman was hit by a bus and suffered an isolated complete oculomotor nerve palsy. Computed tomography scan did not show a skull base fracture. T2*-weighted magnetic resonance imaging revealed petechial cerebral hemorrhages sparing the brainstem. T2 constructive interference in steady state suggested a partial sectioning of the left oculomotor nerve just before entering the superior orbital fissure. Diffusion tensor imaging fiber tractography confirmed a sharp arrest of the left oculomotor nerve. This recent imaging technique could be of interest to assess white fiber damage and help make a diagnosis or prognosis.

Pathogenesis of peri-tumoral edema in intracranial meningiomas

Peri-tumoral edema in intracranial meningiomas occurs frequently and obviously impacts the morbidity and mortality of these predominantly benign neoplasms. Several causative factors (age, gender, volume, location…) have been unsuccessfully investigated. Despite recent progresses in metabolic imaging and molecular biology, the pathogenesis of peri-tumoral edema remains debated. Hypotheses include vascular endothelial growth factor, metalloproteinases and interleukins among many others. It is probable that this pathogenesis encompasses all these factors with different levels. The current review aims to shed the light on the investigated factors involved in the pathogenesis of peri-tumoral edema in meningiomas and identify the potential therapeutic targets.

Reply to: High-Frequency Jet Ventilation for HIFU

We would like to thank Dr. Denys for his insightful comments and to the Editorial Board of this Journal for offering us the opportunity to communicate a reply letter. We aim here to evaluate, comprehensively and concisely, what we believe to be essential issues concerning the use of HFJV as a motion suppression technique for abdominal ablation during extracorporeal HIFU. At the time we made the final submission of our review article [1], Denys et al. article [2] had not yet been publicly released. Moreover, no clinical experience describing the association of HIFU and HFJV techniques had been published and to the best of our knowledge, this continues to be the situation today. The reports we have cited consider the application of HFJV to radiation therapy, percutaneous thermal ablation, or extracorporeal shock wave lithotripsy. To summarize, Fritz et al. [3], working with radiotherapy, showed that HFJV enabled liver motion to be minimized to 3 mm, in agreement with Denys et al. experience. In the field of percutaneous ablation, the only series we found in literature was a retrospective observational study published in 2011 in which nine patients with hepatic or renal lesions were treated under HFJV [4]. We have also acknowledged several reports associating high frequency jet ventilation with extracorporeal shock wave lithotripsy [5–7], a technique similar to some extent to HIFU. It was shown that HFJV reduced urinary stone movement, which increased lithotripsy efficiency with better utilization of shockwave energy and less patient exposure to tissue trauma. Denys et al. study is the first prospective study for percutaneous thermal ablation with the inclusion of a large subset of patients with an intention to treat with HFJV. A real estimation of the proportion of patients noneligible for HFJV therefore can be calculated and details of the exclusion criteria are provided. Overall, their report provides detailed informations on HFJV applied to thermotherapy while we have only summarized some principles in our referenced article whose aim was to review broader topics. We agree with the observation that some lesions located in the upper part of the liver may not be treatable with extracorporeal HIFU under HFJV due to patient being ventilated in a position near of end expiration. This is a problem we have already been confronted with during conventional mechanical ventilation, since we performed sonication during the expiration phase (in sheep and pig animal studies), as it is the longest and most stable phase. Interestingly, intercostal sonication was demonstrated to be feasible [8]; however, the interposition of the right lung’s inferior lobe in the HIFU beam may be a complicated problem for this configuration. Dr. Denys and his team mentioned the possibility of using HFJV for a long period of time. In the specific A. Muller (&) P.-J. Valette F. Cotton Radiology Department, Lyon University Hospital, Centre Hospitalier Lyon Sud, Claude Bernard Lyon 1 University, 165 Chemin du Grand Revoyet, 69495 Pierre Bénite, France e-mail: arnaud.muller@chu-lyon.fr

Accurate Temperature Feedback Control for MRI‐Guided, Phased Array HICU Endocavitary Therapy

Effective treatment of malignant tumours demands well controlled energy deposition in the region of interest. Generally, two major steps must be fulfilled: 1. pre‐operative optimal planning of the thermal dosimetry and 2. per‐operative active spatial‐and‐temporal control of the delivered thermal dose. The second issue is made possible by using fast MR thermometry data and adjusting on line the sonication parameters. This approach is addressed here in the particular case of the ultrasound therapy for endocavitary tumours (oesophagus, colon or rectum) with phased array cylindrical applicators of High Intensity Contact Ultrasound (HICU). Two specific methodological objectives have been defined for this study: 1. to implement a robust and effective temperature controller for the specific geometry of endocavitary HICU and 2. to determine the stability (ie convergence) domain of the controller with respect to possible errors affecting the empirical parameters of the underlying physical model. Experimental setup...

In Vitro Validation of a Sector-Switching HIFU Device for Accelerated Treatment

A sector‐switching method that increases the HIFU sequence duty‐cycle and reduces the equivalent treatment time was tested in vitro. The MR‐compatible HIFU device used consisted of 2 symmetric sectors arranged on a truncated spherical cap (focus = 45 mm, long diameter = 57.5 mm, short diameter = 35 mm). A MR‐compatible, 2D positioning system provided 0.5 mm accuracy. Two sonication sequences were considered, each with the same pattern for the focal point trajectory and with identical on‐state power. First, both sectors radiated simultaneously, with a power duty cycle of 60%. Second, the sectors radiated separately with balanced temporally‐interleaved sonication and a power duty cycle of 87.5%. Numerical simulations were performed to predict the shape of the lesion for a given set of sequence parameters, according to a theoretical model. Fast MR thermometry (voxel size: 0.85×0.85×4.25 mm3; temporal resolution: 2 sec) was performed in two orthogonal planes (sagittal and transverse) while the 2D sonication p...

Optimization of the Thermal Dosimetry for Endocavitary HICU Ablation of Sectorial Digestive Tumours

Effective treatment of malignant tumours demands well controlled energy deposition in the region of interest. Generally, two major steps must be fulfilled: pre‐operative optimal planning of the thermal dosimetry and per‐operative active control of the delivered thermal dose. The first issue is addressed here in the particular case of the ultrasound therapy for endocavitary tumours (oesophagus, colon or rectum) with phased array cylindrical contact applicators. Computation is divided into two main parts: 1. definition of the heating sequence parameters (the total sonication time, the number of independent beams, the orientation and the applied time for every beam), and 2. calculation of the corresponding thermal dose. One slice orthogonal to the symmetry axis of the High Intensity Contact Ultrasound (HICU) device is considered. User defined tumoral geometry is divided into a regular polar grid (5.625 degrees step). The different duration applied for interleaved fast switched beams corresponding to selected...

MRI‐guided Therapeutic Ultrasound : In vitro Validation of a New MR Compatible, Phased Array, Contact Endorectal Ultrasound Transducer with Active Feedback Control of Temperature Evolution

Contact application of high intensity ultrasound was demonstrated to be suitable for thermal ablation of sectorial tumours of the digestive duct. Experimental validation of a new MR compatible ultrasonic device is described here, dedicated to the minimal invasive therapy of localized colorectal cancer. This is a cylindrical 1D 64‐element phased array transducer of 14 mm diameter and 25 mm height (Imasonic, France) allowing electronic rotation of the acoustic beam. Operating frequency ranges from 3.5 to 4.0 MHz and up to 5 effective electrical watts per element are available. A plane wave is reconstructed by simultaneous excitation of eigth adjacent elements with an appropriate phase law. Driving electronics operates outside the Faraday cage of the scanner and provides fast switching capabilities. Excellent passive and active compatibility with the MRI data acquisition has been demonstrated. In addition, feasibility of active temperature control has been demonstrated based on real‐time data export out of t...