scholarly journals Estimation of Anisotropic Material Properties of Soft Tissue by MRI of Ultrasound-Induced Shear Waves

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Charlotte A. Guertler ◽  
Ruth J. Okamoto ◽  
Jake A. Ireland ◽  
Christopher P. Pacia ◽  
Joel R. Garbow ◽  
...  
Keyword(s):  
Soft Tissue ◽  
Focused Ultrasound ◽  
Ex Vivo ◽  
Tissue Sample ◽  
Shear Waves ◽  
Chicken Breast ◽  
Fiber Direction ◽  
Fibrous Materials ◽  
Phase Gradient ◽  
Anisotropic Mechanical Properties

Abstract This paper describes a new method for estimating anisotropic mechanical properties of fibrous soft tissue by imaging shear waves induced by focused ultrasound (FUS) and analyzing their direction-dependent speeds. Fibrous materials with a single, dominant fiber direction may exhibit anisotropy in both shear and tensile moduli, reflecting differences in the response of the material when loads are applied in different directions. The speeds of shear waves in such materials depend on the propagation and polarization directions of the waves relative to the dominant fiber direction. In this study, shear waves were induced in muscle tissue (chicken breast) ex vivo by harmonically oscillating the amplitude of an ultrasound beam focused in a cylindrical tissue sample. The orientation of the fiber direction relative to the excitation direction was varied by rotating the sample. Magnetic resonance elastography (MRE) was used to visualize and measure the full 3D displacement field due to the ultrasound-induced shear waves. The phase gradient (PG) of radially propagating “slow” and “fast” shear waves provided local estimates of their respective wave speeds and directions. The equations for the speeds of these waves in an incompressible, transversely isotropic (TI), linear elastic material were fitted to measurements to estimate the shear and tensile moduli of the material. The combination of focused ultrasound and MR imaging allows noninvasive, but comprehensive, characterization of anisotropic soft tissue.

Instrumentation for Testing Soft Tissue Undergoing Large Deformation: Ex Vivo and In Vivo Studies

2008 ◽  
Vol 2 (4) ◽  
Author(s):  
Tie Hu ◽  
Alan C. W. Lau ◽  
Jaydev P. Desai
Keyword(s):  
Soft Tissue ◽  
Surface Area ◽  
Ex Vivo ◽  
Tissue Sample ◽  
Biomechanical Property ◽  
Probe Surface ◽  
In Vivo Experiments ◽  
In Vivo Testing ◽  
Force Resolution

Biomechanical property of soft tissue derived from experimental measurements is critical to develop a reality-based soft-tissue model for minimally invasive surgical training and simulation. In our research, we have focused on developing a biomechanical model of the liver with the ultimate goal of using this model for local tool-tissue interaction tasks and providing feedback to the surgeon through a haptic (sense of touch) display. In this paper, we present two devices that we have designed and built, namely, ex vivo and in vivo testing devices. We used them to measure the experimental force and displacement data of pig liver tissue. The device for ex vivo experiments uses a PC-based control system to control the motion of the probe and acquire the experimental force and displacement data. The force resolution for ex vivo testing was 0.002N (as per the resolution information provided by the manufacturer) and the probe velocity ranged from 0.1mm∕s to 25.4mm∕s. The device was designed so that it could be easily used for both small probe (tissue sample larger than the indenting probe surface area) testing as well as large probe (tissue sample smaller than the indenting probe surface area) testing. The device for in vivo experiments used a microcontroller-based instrumentation to control the motion and acquire and store the data on a multimedia memory disk. This device is designed for the purpose of acquiring experimental force and displacement data in vivo. The primary challenge in the design of the device for in vivo experiments was the limited workspace for device operation. The force resolution for in vivo testing was 0.015N and the displacement resolution was 0.02mm. The sampling frequency for data acquisition for in vivo testing was 50Hz.

scholarly journals Characterization and Ex Vivo evaluation of an extracorporeal high‐intensity focused ultrasound (HIFU) system

2021 ◽  
Author(s):  
Yufeng Zhou ◽  
Bryan W. Cunitz ◽  
Barbrina Dunmire ◽  
Yak‐Nam Wang ◽  
Steven G. Karl ◽  
...  
Keyword(s):  
High Intensity ◽  
Focused Ultrasound ◽  
Ex Vivo ◽  
High Intensity Focused Ultrasound

scholarly journals Trans-cranial focused ultrasound without hair shaving: feasibility study in an ex vivo cadaver model

2013 ◽  
Vol 1 (1) ◽  
pp. 24 ◽  
Author(s):  
Matthew DC Eames ◽  
Arik Hananel ◽  
John W Snell ◽  
Neal F Kassell ◽  
Jean-Francois Aubry
Keyword(s):  
Feasibility Study ◽  
Focused Ultrasound ◽  
Ex Vivo

scholarly journals Analysis of Staphylococcus aureus transcriptome in pediatric soft tissue abscesses and comparison to murine infections

2021 ◽  
Author(s):  
K Moffitt ◽  
E Cheung ◽  
T Yeung ◽  
C Stamoulis ◽  
R Malley
Keyword(s):  
Staphylococcus Aureus ◽  
Soft Tissue ◽  
Ex Vivo ◽  
Human Infection ◽  
Nucleic Acid Amplification ◽  
Clinical Strain ◽  
Nasal Colonization ◽  
Abscess Drainage ◽  
Mrna Transcripts

A comprehensive understanding of how Staphylococcus aureus adapts to cause infections in humans can inform development of diagnostic, therapeutic, and preventive approaches. Expression analysis of clinical strain libraries depicts in vitro conditions that differ from those in human infection, but low bacterial burden and the requirement for reverse transcription or nucleic acid amplification complicate such analyses of bacteria causing human infection. We developed methods to evaluate the mRNA transcript signature of S. aureus in pediatric skin and soft tissue (SSTI) infections directly ex vivo. Abscess drainage from 47 healthy pediatric patients undergoing drainage of a soft tissue infection was collected, and RNA was extracted from samples from patients with microbiologically confirmed S. aureus abscesses (42% due to methicillin-resistant S. aureus, MRSA). Using the Nanostring platform and primers targeting S. aureus mRNA transcripts encoding surface-expressed or secreted proteins, we measured direct counts of 188 S. aureus mRNA transcripts in abscess drainage. We further evaluated this mRNA signature in murine models of S. aureus SSTI and nasal colonization where the kinetics of the transcriptome could be determined. Heat maps of the S. aureus mRNA signatures from pediatric abscesses demonstrated consistent per target expression across patients. While there was significant overlap with the profiles from murine SSTI and nasal colonization, important differences were noted, which can inform efforts to develop therapeutic and vaccine approaches.

scholarly journals A review of techniques for visualising soft tissue microstructure deformation and quantifying strain Ex Vivo

2018 ◽  
Vol 272 (3) ◽  
pp. 165-179 ◽  
Author(s):  
C.M. DISNEY ◽  
P.D. LEE ◽  
J.A. HOYLAND ◽  
M.J. SHERRATT ◽  
B.K. BAY
Keyword(s):  
Soft Tissue ◽  
Ex Vivo ◽  
Tissue Microstructure

High-Intensity Focused Ultrasound Scattering at Mammal Vertebrae

2020 ◽  
Author(s):  
David Sanford ◽  
Christoph Schaal
Keyword(s):  
High Intensity ◽  
Laboratory Experiments ◽  
Energy Deposition ◽  
Focused Ultrasound ◽  
Complex Geometry ◽  
Ex Vivo ◽  
Pulsed Laser ◽  
High Intensity Focused Ultrasound ◽  
Focal Region ◽  
Homogeneous Media

Abstract High-intensity focused ultrasound (HIFU) is used clinically to heat cells therapeutically or to destroy them through heat or cavitation. In homogeneous media, the highest wave amplitudes occur at a predictable focal region. However, HIFU is generally not used in the proximity of bones due to wave absorption and scattering. Ultrasound is passed through the skull in some clinical trials, but the complex geometry of the spine poses a greater targeting challenge and currently prohibits therapeutic ultrasound treatments near the vertebral column. This paper presents a comprehensive experimental study involving shadowgraphy and hydrophone measurements to determine the spatial distribution of pressure amplitudes from induced HIFU waves near vertebrae. First, a bone-like composite plate that is partially obstructing the induced waves is shown to break the conical HIFU form into two regions. Wave images are captured using pulsed laser shadowgraphy, and hydrophone measurements over the same region are compared to the shadowgraphy intensity plots to validate the procedure. Next, shadowgraphy is performed for an individual, clean, ex-vivo feline vertebra. The results indicate that shadowgraphy can be used to determine energy deposition patterns and to determine heating at a specific location. The latter is confirmed through additional temperature measurements. Overall, these laboratory experiments may help determine the efficacy of warming specific nerve cells within mammal vertebrae without causing damage to adjacent tissue.

scholarly journals Thulium:YAG vs Holmium:YAG laser effect on soft tissue: Evidence from an ex vivo experimental study

2020 ◽  
Vol 19 ◽  
pp. e83-e84
Author(s):  
M.E. Rodríguez Socarrás ◽  
S. Proietti ◽  
R. Luciano’ ◽  
F. Scarfo’ ◽  
G. Saitta ◽  
...  
Keyword(s):  
Experimental Study ◽  
Soft Tissue ◽  
Ex Vivo ◽  
Holmium:Yag Laser ◽  
Laser Effect
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