Acoustic Radiation Force Impulse (ARFI) Imaging
Encyclopedia
Acoustic Radiation Force Impulse (ARFI) Imaging uses acoustic radiation force
to generate images of the mechanical properties of soft tissue
.
includes both scattering and absorption of the acoustic wave. Attenuation is a frequency dependent phenomenon, and in soft tissues it is dominated by absorption. With increasing acoustic frequencies, the tissue does not respond fast enough to the transitions between positive and negative pressures, thus its motion becomes out of phase with the acoustic wave, and energy is deposited into the tissue. This energy results in a momentum
transfer in the direction of wave propagation and tissue heating. The momentum transfer generates a force that causes displacement of the tissue, and the time scale of this response is much slower than that of the ultrasonic wave propagation. This interaction of sound with tissue can be used to derive additional information about the tissue, beyond what is normally provided in an ultrasonic image. The magnitude, location, spatial extent, and duration of acoustic radiation force can be controlled to interrogate the mechanical properties of the tissue.
Liver Fibrosis Quantification efforts at Duke University
Acoustic Radiation Force Impulse Imaging (ARFI): a New Technique to Assess Liver Elasticity
Yoneda et al. also recently compared ARFI shear wave imaging as implemented on the Siemens Acuson S2000 with transient elastography using the FibroScan system (EchoSens, Paris, France) in the context of evaluating patients with Non-alcoholic Fatty Liver Disease (NAFLD).
results from a transfer of momentum
from an acoustic wave to tissue in the direction of wave propagation, arising from absorption and scattering of the wave. The tissue displacement response to radiation force excitation occurs on a slower time-scale than ultrasonic wave propagation, thus, conventional ultrasonic methods can be used to monitor the tissue response to radiation force. For breast imaging, experiments have been conducted to measure the potential for ARFI images to provide adjunctive information to matched ultrasonic images
in order to enhance clinical confidence in diagnosis of breast masses. Patients scheduled for core biopsy
of breast masses are recruited and matched B-mode and ARFI images of masses were obtained. The images were then correlated with biopsy result.
is the second leading cause of cancer
death in the United States (after lung cancer
), and the third most common cancer overall in men (after prostate
and lung cancer) and women (after breast
and lung cancer). Once identified, the treatment approach for rectal cancer is dictated by the stage of the tumor (T-stage
) and local lymph nodes
(N-stage). There are currently no imaging methods that provide reliable N-staging accuracy of colorectal cancers. While endorectal ultrasound
(EUS) is the standard for staging the degree of wall invasion of rectal cancers (T-stage), its accuracy is poor in the critical determination between uT2 and uT3, with 10-35% of uT2 tumors being overstaged. The consequences for the patient are dramatic. A stage uT3 rectal carcinoma is treated by radical surgical resection, and is typically treated with neoadjuvant chemotherapy and radiation. Neoadjuvant treatment damages adjacent healthy tissues, and can impair the healing process following surgery, leading to increased complications of infection, bleeding, decreased colonic mobility, and incontinence. Whereas stage uT2, N- and lower tumors generally receive a transanal local excision and are not treated neoadjuvantly, eliminating these additional risks to the patient.
The objective of ARFI Imaging development is to develop and evaluate the ability of ARFI imaging techniques to image layered tissue structures as found in the gastrointestinal tract, and to guide treatment decisions yhrough improved preoperative tumor and lymph node staging.
is the most common cancer and the second leading cause of cancer
death in American men. According to the American Cancer Society
(ACS), an estimated 218,890 new cases of prostate cancer will be found and 27,050 men will die of this disease in 2007. Early diagnosis is essential for better treatment and increasing survival rate. Although the current screening techniques, antigen (PSA) blood testing
and digital rectal examination (DRE) are considered sensitive enough for cancer screening, follow-up biopsies have significant shortcomings. Without a good imaging technique to target the needle biopsy in the prostate gland, only about 25% of tests are positive for cancer in more than 1 million prostate biopsies performed each year; the false negative rates range from 25-45% based on the first time biopsy.
Although imaging techniques are essential for cancer diagnosis, imaging the structures and lesions within prostates has been a challenging task. The goal of ARFI imaging is to optimize and evaluate ARFI techniques for prostate imaging, which will potentially provide a more accurate, low cost and patient friendly imaging guidance for targeting prostate biopsies.
Acoustic radiation force
Acoustic radiation force is a physical phenomenon resulting from the interaction of an acoustic wave with an obstacle placed along its path. Generally, the force exerted on the obstacle is evaluated by integrating the acoustic radiation pressure over its time-varying surface.- Medical Imaging...
to generate images of the mechanical properties of soft tissue
Soft tissue
In anatomy, the term soft tissue refers to tissues that connect, support, or surround other structures and organs of the body, not being bone. Soft tissue includes tendons, ligaments, fascia, skin, fibrous tissues, fat, and synovial membranes , and muscles, nerves and blood vessels .It is sometimes...
.
How it works
Acoustic radiation force is a phenomenon associated with the propagation of acoustic waves in attenuating media. AttenuationAttenuation
In physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, X-rays are attenuated by lead, and light and sound are attenuated by water.In electrical engineering and telecommunications, attenuation affects the...
includes both scattering and absorption of the acoustic wave. Attenuation is a frequency dependent phenomenon, and in soft tissues it is dominated by absorption. With increasing acoustic frequencies, the tissue does not respond fast enough to the transitions between positive and negative pressures, thus its motion becomes out of phase with the acoustic wave, and energy is deposited into the tissue. This energy results in a momentum
Momentum
In classical mechanics, linear momentum or translational momentum is the product of the mass and velocity of an object...
transfer in the direction of wave propagation and tissue heating. The momentum transfer generates a force that causes displacement of the tissue, and the time scale of this response is much slower than that of the ultrasonic wave propagation. This interaction of sound with tissue can be used to derive additional information about the tissue, beyond what is normally provided in an ultrasonic image. The magnitude, location, spatial extent, and duration of acoustic radiation force can be controlled to interrogate the mechanical properties of the tissue.
Liver Fibrosis Quantification
The speed at which shear waves propagate in tissue can be used to quantify the shear modulus of the tissue. Acoustic radiation force-based imaging modalities are being studied to non-invasively characterize the liver without the need for liver biopsy.Liver Fibrosis Quantification efforts at Duke University
Acoustic Radiation Force Impulse Imaging (ARFI): a New Technique to Assess Liver Elasticity
Yoneda et al. also recently compared ARFI shear wave imaging as implemented on the Siemens Acuson S2000 with transient elastography using the FibroScan system (EchoSens, Paris, France) in the context of evaluating patients with Non-alcoholic Fatty Liver Disease (NAFLD).
Breast Mass Imaging
Focused acoustic waves that propagate through tissue are absorbed and generate radiation force. Acoustic radiation forceAcoustic radiation force
Acoustic radiation force is a physical phenomenon resulting from the interaction of an acoustic wave with an obstacle placed along its path. Generally, the force exerted on the obstacle is evaluated by integrating the acoustic radiation pressure over its time-varying surface.- Medical Imaging...
results from a transfer of momentum
Momentum
In classical mechanics, linear momentum or translational momentum is the product of the mass and velocity of an object...
from an acoustic wave to tissue in the direction of wave propagation, arising from absorption and scattering of the wave. The tissue displacement response to radiation force excitation occurs on a slower time-scale than ultrasonic wave propagation, thus, conventional ultrasonic methods can be used to monitor the tissue response to radiation force. For breast imaging, experiments have been conducted to measure the potential for ARFI images to provide adjunctive information to matched ultrasonic images
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
in order to enhance clinical confidence in diagnosis of breast masses. Patients scheduled for core biopsy
Biopsy
A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
of breast masses are recruited and matched B-mode and ARFI images of masses were obtained. The images were then correlated with biopsy result.
Colorectal Tumor Imaging/Staging
Colorectal cancerColorectal cancer
Colorectal cancer, commonly known as bowel cancer, is a cancer caused by uncontrolled cell growth , in the colon, rectum, or vermiform appendix. Colorectal cancer is clinically distinct from anal cancer, which affects the anus....
is the second leading cause of cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
death in the United States (after lung cancer
Lung cancer
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary...
), and the third most common cancer overall in men (after prostate
Prostate
The prostate is a compound tubuloalveolar exocrine gland of the male reproductive system in most mammals....
and lung cancer) and women (after breast
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
and lung cancer). Once identified, the treatment approach for rectal cancer is dictated by the stage of the tumor (T-stage
Cancer staging
The stage of a cancer is a description of the extent the cancer has spread. The stage often takes into account the size of a tumor, how deeply it has penetrated, whether it has invaded adjacent organs, how many lymph nodes it has metastasized to , and whether it has spread to distant organs...
) and local lymph nodes
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
(N-stage). There are currently no imaging methods that provide reliable N-staging accuracy of colorectal cancers. While endorectal ultrasound
Endoscopic ultrasound
Endoscopic ultrasound or echo-endoscopy is a medical procedure in endoscopy is combined with ultrasound to obtain images of the internal organs in the chest and abdomen. It can be used to visualize the wall of these organs, or to look at adjacent structures...
(EUS) is the standard for staging the degree of wall invasion of rectal cancers (T-stage), its accuracy is poor in the critical determination between uT2 and uT3, with 10-35% of uT2 tumors being overstaged. The consequences for the patient are dramatic. A stage uT3 rectal carcinoma is treated by radical surgical resection, and is typically treated with neoadjuvant chemotherapy and radiation. Neoadjuvant treatment damages adjacent healthy tissues, and can impair the healing process following surgery, leading to increased complications of infection, bleeding, decreased colonic mobility, and incontinence. Whereas stage uT2, N- and lower tumors generally receive a transanal local excision and are not treated neoadjuvantly, eliminating these additional risks to the patient.
The objective of ARFI Imaging development is to develop and evaluate the ability of ARFI imaging techniques to image layered tissue structures as found in the gastrointestinal tract, and to guide treatment decisions yhrough improved preoperative tumor and lymph node staging.
Prostate Imaging
Prostate cancerProstate cancer
Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing; however, there are cases of aggressive prostate cancers. The cancer cells may metastasize from the prostate to other parts of the body, particularly...
is the most common cancer and the second leading cause of cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
death in American men. According to the American Cancer Society
American Cancer Society
The American Cancer Society is the "nationwide community-based voluntary health organization" dedicated, in their own words, "to eliminating cancer as a major health problem by preventing cancer, saving lives, and diminishing suffering from cancer, through research, education, advocacy, and...
(ACS), an estimated 218,890 new cases of prostate cancer will be found and 27,050 men will die of this disease in 2007. Early diagnosis is essential for better treatment and increasing survival rate. Although the current screening techniques, antigen (PSA) blood testing
Prostate cancer screening
Prostate cancer screening is an attempt to identify individuals with prostate cancer in a broad segment of the population—those for whom there is no reason to suspect prostate cancer. There are two methods used: One is the digital rectal examination , in which the examiner inserts a gloved,...
and digital rectal examination (DRE) are considered sensitive enough for cancer screening, follow-up biopsies have significant shortcomings. Without a good imaging technique to target the needle biopsy in the prostate gland, only about 25% of tests are positive for cancer in more than 1 million prostate biopsies performed each year; the false negative rates range from 25-45% based on the first time biopsy.
Although imaging techniques are essential for cancer diagnosis, imaging the structures and lesions within prostates has been a challenging task. The goal of ARFI imaging is to optimize and evaluate ARFI techniques for prostate imaging, which will potentially provide a more accurate, low cost and patient friendly imaging guidance for targeting prostate biopsies.
ARFI Imaging In the News & External links
- Kathy Nightingale Lab Website
- Gregg Trahey Lab Website
- Tissue Strain Analytics from Siemens Ultrasound Website
- Elastography advances feature prominently among ultrasound exhibits
- http://www.ehealthnews.eu/siemens/1943-siemens-showcases-advanced-ultrasound-solutions
- http://www.hospitalhealthcare.com/default.asp?title=Siemenspresentthelatestindiagnosticimaging&page=article.display&article.id=20464