title: Defining the optimal age for focal lesioning in a rat model of transcranial HIFU.
abstract: This study aimed at determining the optimal age group for high-intensity focused ultrasound (HIFU) experiments for producing lesions in rats. Younger rats have thinner skulls, allowing for the acoustic waves to propagate easily through the skull without causing burns of the skin and brain surface. Younger rats however, have a smaller brain that can make HIFU focusing in the brain parenchyma challenging because of the focus size. In this study, we conducted transcranial HIFU sonications in rat pups of different ages (from 9 to 43 d) with a 1.5MHz MR compatible transducer. The electric power was selected to always reach a target temperature of at least 50°C in the parenchyma. The thickness of the skull and of the brain parenchyma was measured using T2-weighted MR imaging. Results showed that the thickness of the brain parenchyma increased quickly from P9 to P12, reaching 8.5 mm at P16, and then increasing gradually along with age. The skull thickness increased gradually from P9 to P26, and then more quickly after P30. The ratio between brain parenchyma thickness and skull thickness decreased gradually with age. For the pups at 30 d, the temperature in the brain tissue adjacent to the skull increased to 48.9°C, and those from the rodents older than 33 d reached 60°C or higher, which can produce undesired irreversible damage in this location. We conclude that young rats aged 16-26 d are optimal for experiments producing transcranial HIFU lesions in rats with an intact skull.
authors.affiliation: Department of Ultrasound, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China; Neuroradiology Division, Department of Radiology, University of Virginia, Charlottesville, VA, USA.
authors.forename: Yanrong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, University of Virginia, Charlottesville, VA, USA; ESPCI ParisTech, PSL Research University, Institut Langevin, Paris, France; CNRS, Institut Langevin, Paris, France; INSERM, Institut Langevin, Paris, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Aubry
authors.affiliation: Department of Anesthesiology, University of Virginia, Charlottesville, VA, USA; Department of Anesthesiology, Shanghai Sixth Hospital, Shanghai Jiaotong University, Shanghai, China.
authors.forename: Junfeng
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Departments of Neuroscience and Neurologic Surgery, University of Virginia, Charlottesville, VA, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Radiology, University of Virginia, Charlottesville, VA, USA.
authors.forename: Jack
authors.initials: J
authors.lastname: Roy
authors.affiliation: Department of Radiology, University of Virginia, Charlottesville, VA, USA.
authors.forename: Jaime F
authors.initials: JF
authors.lastname: Mata
authors.affiliation: Department of Radiology, University of Virginia, Charlottesville, VA, USA.
authors.forename: Wilson
authors.initials: W
authors.lastname: Miller
authors.affiliation: Image Guided Therapy, Pessac, France.
authors.forename: Erik
authors.initials: E
authors.lastname: Dumont
authors.affiliation: Department of Ultrasound, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Mingxing
authors.initials: M
authors.lastname: Xie
authors.affiliation: Departments of Neuroscience and Neurologic Surgery, University of Virginia, Charlottesville, VA, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Lee
authors.affiliation: Department of Anesthesiology, University of Virginia, Charlottesville, VA, USA.
authors.forename: Zhiyi
authors.initials: Z
authors.lastname: Zuo
authors.affiliation: Neuroradiology Division, Department of Radiology, University of Virginia, Charlottesville, VA, USA. Electronic address: Max.Wintermark@gmail.com.
authors.forename: Max
authors.initials: M
authors.lastname: Wintermark
mesh_terms: D000367:Age Factors; D000818:Animals; D001921:Brain / Q000473:pathology / Q000601:surgery; D001932:Brain Neoplasms / Q000601:surgery*; D004195:Disease Models, Animal; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D008279:Magnetic Resonance Imaging; D015642:Radiology, Interventional / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley
keywords: Magnetic resonance imaging; Optimal age group; Research model; Transcranial high-intensity focused ultrasound