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1136
P42
Ultrasound in Medicine and Biology
yps, changes associated with hormone replacement or tamoxifen therapy, submucosal leiomyomas and other polypoid endometrial and myometrial tumors. Potential pitfalls that can mimic pathology as well as technical limitations will also be shown. Recognition of commonly encountered pitfalls and technical artifacts during SH and their appearance on images are important to avoid misinterpretation of these conditions. Several new technologies and their applications to SH have been introduced in recent years and their future usages into the clinical practices are under investigation. Color Doppler imaging combined with SH can also characterize uterine pathology by clearly depicting vessels within the lesions in cases of abnormal uterine bleeding. Recently, three-dimensional (3D) ultrasonography with either multiplanar reconstruction or surface-rendering techniques has been advocated to get a better global view of the uterine cavity. Reports with the use of 3D imaging have shown promising results, indicating that 3D SH could help to reinforce the diagnostic impression based on 2D ultrasonography, but its value remains controversial. More recently, ultrasound contrast agent can be another possibility for enhancing Doppler examination by improving the detection of small vessels beyond the resolution of color imaging. Finally, endometrial biopsies have been performed under direct real-time SH guidance. Its results are fairly comparable to the results of hysteroscopic biopsies. Although we had technical difficulties managing leakage of saline during a biopsy as well as limited steerability of the biopsy device, with equipment having improved, this technique will be valuable in performing directed biopsy of both focal and diffuse endometrial lesions adequately. PHYSICS AND BIOEFFECTS 1134 Ultrasonic biomedical microscanning: A review Wells P, Cardiff University, United Kingdom of Great Britain and Northern Ireland The smallest structures, which can be seen by the unaided eye, are about 0.1 mm (100 m) in size and this is the highest spatial resolution that has traditionally been of interest in structural and functional imaging. In ultrasonic imaging, the wavelength is 0.1 mm at a frequency of around 15 MHz, and this is the highest frequency that is currently in routine clinical use, although frequencies of up to about 30 MHz may be used in intrasvascular scanning. When higher frequencies are used, in the range from 30 to 150 MHz, the process is called “microscanning” and the corresponding spatial resolution lies between about 0.05 and 0.01 mm. Single cells, which typically are about 0.01 mm in size, can be seen at the highest frequencies in the microscanning range with B-mode imaging, but the penetration is limited to a few millimeters because of the correspondingly high attenuation (up to about 10 dB/mm of penetration in soft tissue at 150 MHz). This restricts the technique to the examination of tissue specimens, small animals and structures that are close to the transducer, as, for example, when the transducer is mounted at the tip of a needle. The potential clinical utility of structural and functional imaging in this frequency range, with and without contrast agent enhancement, has hardly yet begun to be explored, and this knowledge gap is prompting the development of instruments using various novel scanning modes, including continuous wave Doppler tomography. 1135 The study of real-time ultrasound microscope and the way to clinical application Itoh K, Irie T, Moriya T, Jichi Medical School, Japan; Micro-sonic, Japan; Tokyo Metropolitan University, Japan The purpose of this study is to know the development of real-time ultrasound microscope and how to apply to the clinical trials. We are
Volume 32, Number 5S, 2006 studying basic methodology for inserting the special needle and the optical fiber into the body. We simulated the special images for the ultrasound going into the optical fiber. We planed to make the special sheath needle, which has a special hole on the top of it. The optical fiber and the 100 and 170 MHz transducer are moved by the special driving units outside of human body. The two-dimensional images of tissue level can be seen on the monitor. 1136 Elasticity imaging: Recent progress in technology and applications Bamber JC, Institute of Cancer Research and Royal Marsden NHS Trust, United Kingdom of Great Britain and Northern Ireland Elasticity images may be thought of as “palpation” images that display the spatial distribution of quantities related to mechanical tissue properties such as Young’s modulus (tissue stiffness). They may be generated using data from any medical anatomical imaging method, but with ultrasound the principle is to process echoes so as to measure the tissue displacement or strain (distortion) that results from an applied stress (force). This is an exciting field in which imaging modalities are emerging that display new information with good resolution. The image contrast may also be high, both because detection of motion is a relatively efficient noise-reducing way to process ultrasonic echoes and because there is large variation in elastic properties from one tissue to another. Work on using ultrasound to assess tissue elasticity dates from the mid-1970s, when researchers were using M-mode to observe differences between benign and malignant breast tumours in their response to palpation. This was followed by subjective interpretation of real-time B-mode scans of the breast during palpation, the assessment of motion patterns of liver tumours using A-mode echo decorrelation and the observation of shear wave propagation in muscle using Doppler. Elasticity images were generated (independently by Parker and Bamber) in 1986, showing that tissue displacement could depict variations in stiffness. The concept of imaging strain, the spatial gradient of displacement and the term elastography to describe it, were introduced in 1991 (by Ophir), and freehand elastography in 1996 (Bamber). A number of small but encouraging clinical trials have recently shown that elastography may be a useful adjunct to conventional ultrasound examination of the breast, and several commercial scanners now have real-time elastogram display options. Substantial recent progress in this field has produced many different technical approaches to elasticity imaging. The stress may be applied to the tissue either statically or dynamically, as an impulse or with vibration, using the ultrasound probe or separately, with a compression or shear, using hand-induced motion or mechanically, at the body surface or deep within the body using natural cardiovascular pulsations or acoustic radiation force. The signal processing may measure displacement or strain, and may do this using Doppler, speckle decorrelation, envelope or RF echo tracking, echo texture change, instantaneous frequency shift and combinations of these methods in 1D, 2D or 3D. In addition to the display of displacement or strain, these quantities may be used to reconstruct other images. Iterative and direct methods of reconstructing Young’s modulus are being explored, as too are methods for displaying properties such as Poisson’s ratio, shear wave speed, shear wave attenuation coefficient, frequency dependence, nonlinearity, hysteresis, anisotropy, slip boundaries, tissue porosity and tissue fluid-permeability. Applications for which elasticity imaging is now being studied range widely, for example, from assisting with breast cancer diagnosis, to assessing deep vein thrombosis, atherosclerosis, radiation fibrosis, lymphoedema, pigmented skin tumours and myocardial function, monitoring thermal tissue ablation and intraoperative guidance for neurosurgery. The future looks set for a considerable and beneficial broadening of the subject.
Ultrasound in Medicine and Biology
yps, changes associated with hormone replacement or tamoxifen therapy, submucosal leiomyomas and other polypoid endometrial and myometrial tumors. Potential pitfalls that can mimic pathology as well as technical limitations will also be shown. Recognition of commonly encountered pitfalls and technical artifacts during SH and their appearance on images are important to avoid misinterpretation of these conditions. Several new technologies and their applications to SH have been introduced in recent years and their future usages into the clinical practices are under investigation. Color Doppler imaging combined with SH can also characterize uterine pathology by clearly depicting vessels within the lesions in cases of abnormal uterine bleeding. Recently, three-dimensional (3D) ultrasonography with either multiplanar reconstruction or surface-rendering techniques has been advocated to get a better global view of the uterine cavity. Reports with the use of 3D imaging have shown promising results, indicating that 3D SH could help to reinforce the diagnostic impression based on 2D ultrasonography, but its value remains controversial. More recently, ultrasound contrast agent can be another possibility for enhancing Doppler examination by improving the detection of small vessels beyond the resolution of color imaging. Finally, endometrial biopsies have been performed under direct real-time SH guidance. Its results are fairly comparable to the results of hysteroscopic biopsies. Although we had technical difficulties managing leakage of saline during a biopsy as well as limited steerability of the biopsy device, with equipment having improved, this technique will be valuable in performing directed biopsy of both focal and diffuse endometrial lesions adequately. PHYSICS AND BIOEFFECTS 1134 Ultrasonic biomedical microscanning: A review Wells P, Cardiff University, United Kingdom of Great Britain and Northern Ireland The smallest structures, which can be seen by the unaided eye, are about 0.1 mm (100 m) in size and this is the highest spatial resolution that has traditionally been of interest in structural and functional imaging. In ultrasonic imaging, the wavelength is 0.1 mm at a frequency of around 15 MHz, and this is the highest frequency that is currently in routine clinical use, although frequencies of up to about 30 MHz may be used in intrasvascular scanning. When higher frequencies are used, in the range from 30 to 150 MHz, the process is called “microscanning” and the corresponding spatial resolution lies between about 0.05 and 0.01 mm. Single cells, which typically are about 0.01 mm in size, can be seen at the highest frequencies in the microscanning range with B-mode imaging, but the penetration is limited to a few millimeters because of the correspondingly high attenuation (up to about 10 dB/mm of penetration in soft tissue at 150 MHz). This restricts the technique to the examination of tissue specimens, small animals and structures that are close to the transducer, as, for example, when the transducer is mounted at the tip of a needle. The potential clinical utility of structural and functional imaging in this frequency range, with and without contrast agent enhancement, has hardly yet begun to be explored, and this knowledge gap is prompting the development of instruments using various novel scanning modes, including continuous wave Doppler tomography. 1135 The study of real-time ultrasound microscope and the way to clinical application Itoh K, Irie T, Moriya T, Jichi Medical School, Japan; Micro-sonic, Japan; Tokyo Metropolitan University, Japan The purpose of this study is to know the development of real-time ultrasound microscope and how to apply to the clinical trials. We are
Volume 32, Number 5S, 2006 studying basic methodology for inserting the special needle and the optical fiber into the body. We simulated the special images for the ultrasound going into the optical fiber. We planed to make the special sheath needle, which has a special hole on the top of it. The optical fiber and the 100 and 170 MHz transducer are moved by the special driving units outside of human body. The two-dimensional images of tissue level can be seen on the monitor. 1136 Elasticity imaging: Recent progress in technology and applications Bamber JC, Institute of Cancer Research and Royal Marsden NHS Trust, United Kingdom of Great Britain and Northern Ireland Elasticity images may be thought of as “palpation” images that display the spatial distribution of quantities related to mechanical tissue properties such as Young’s modulus (tissue stiffness). They may be generated using data from any medical anatomical imaging method, but with ultrasound the principle is to process echoes so as to measure the tissue displacement or strain (distortion) that results from an applied stress (force). This is an exciting field in which imaging modalities are emerging that display new information with good resolution. The image contrast may also be high, both because detection of motion is a relatively efficient noise-reducing way to process ultrasonic echoes and because there is large variation in elastic properties from one tissue to another. Work on using ultrasound to assess tissue elasticity dates from the mid-1970s, when researchers were using M-mode to observe differences between benign and malignant breast tumours in their response to palpation. This was followed by subjective interpretation of real-time B-mode scans of the breast during palpation, the assessment of motion patterns of liver tumours using A-mode echo decorrelation and the observation of shear wave propagation in muscle using Doppler. Elasticity images were generated (independently by Parker and Bamber) in 1986, showing that tissue displacement could depict variations in stiffness. The concept of imaging strain, the spatial gradient of displacement and the term elastography to describe it, were introduced in 1991 (by Ophir), and freehand elastography in 1996 (Bamber). A number of small but encouraging clinical trials have recently shown that elastography may be a useful adjunct to conventional ultrasound examination of the breast, and several commercial scanners now have real-time elastogram display options. Substantial recent progress in this field has produced many different technical approaches to elasticity imaging. The stress may be applied to the tissue either statically or dynamically, as an impulse or with vibration, using the ultrasound probe or separately, with a compression or shear, using hand-induced motion or mechanically, at the body surface or deep within the body using natural cardiovascular pulsations or acoustic radiation force. The signal processing may measure displacement or strain, and may do this using Doppler, speckle decorrelation, envelope or RF echo tracking, echo texture change, instantaneous frequency shift and combinations of these methods in 1D, 2D or 3D. In addition to the display of displacement or strain, these quantities may be used to reconstruct other images. Iterative and direct methods of reconstructing Young’s modulus are being explored, as too are methods for displaying properties such as Poisson’s ratio, shear wave speed, shear wave attenuation coefficient, frequency dependence, nonlinearity, hysteresis, anisotropy, slip boundaries, tissue porosity and tissue fluid-permeability. Applications for which elasticity imaging is now being studied range widely, for example, from assisting with breast cancer diagnosis, to assessing deep vein thrombosis, atherosclerosis, radiation fibrosis, lymphoedema, pigmented skin tumours and myocardial function, monitoring thermal tissue ablation and intraoperative guidance for neurosurgery. The future looks set for a considerable and beneficial broadening of the subject.