Compensating for ultrasound frequency attenuation in tissue when determining tissue effective particle size
(2021) BMEM01 20212Department of Biomedical Engineering
- Abstract
- Giant cell arteritis is a disease the affects the arteries, for example the temporal artery. When affecting the temporal artery, it can cause serious consequences such as blindness and stroke. The existing methods for diagnosing the disease are invasive, time consuming and costly. Ultrasound would therefore be an attractive diagnostic alternative providing a lot of benefits. Information about the characteristics of tissue can be obtained from the frequency spectra of the ultrasound echo pulse. This can be used to distinguish diseased tissue from healthy tissue.
When using this method in in vivo studies, the tissue, for example the skin, between the ultrasound transducer and the tissue being investigated also impacts the frequency spectra... (More) - Giant cell arteritis is a disease the affects the arteries, for example the temporal artery. When affecting the temporal artery, it can cause serious consequences such as blindness and stroke. The existing methods for diagnosing the disease are invasive, time consuming and costly. Ultrasound would therefore be an attractive diagnostic alternative providing a lot of benefits. Information about the characteristics of tissue can be obtained from the frequency spectra of the ultrasound echo pulse. This can be used to distinguish diseased tissue from healthy tissue.
When using this method in in vivo studies, the tissue, for example the skin, between the ultrasound transducer and the tissue being investigated also impacts the frequency spectra of the ultrasound pulse. This project examines this impact and how to compensate for it so that it does not influence the measurements of the actual tissue being investigated. A graphical user interface is also developed as a tool for evaluating measurement data obtained during the in vivo study.
It was found that the frequency attenuation in the tissue between the skin and the tissue being investigated can be approximated as linear. When compensating for this attenuation it is not possible to use a general compensation curve for all patients. The compensation has to be done individually for each patient. (Less) - Popular Abstract
- Diagnosing giant cell arteritis (GCA) with ultrasound center frequency shift (CFS)
Giant cell arteritis (GCA) is a disease that casuses inflamation of larger blood vessels. This can for example affect the temporal artery, an artery supplying blood to the head and brain. GCA of the temporal artery results in symptoms such as headaches, dizziness, and problems with vision. If left untreated it can cause blindness, aneurysm and stroke. When a patient is suspected of having GCA, a biopsy is performed. During the biopsy a part of the temporal artery is surgically removed. Diagnosing GCA non invasively with ultrasound would be of benefit to the patient as it is less harmful and avoids risks associated with biopsy and can be performed at the... (More) - Diagnosing giant cell arteritis (GCA) with ultrasound center frequency shift (CFS)
Giant cell arteritis (GCA) is a disease that casuses inflamation of larger blood vessels. This can for example affect the temporal artery, an artery supplying blood to the head and brain. GCA of the temporal artery results in symptoms such as headaches, dizziness, and problems with vision. If left untreated it can cause blindness, aneurysm and stroke. When a patient is suspected of having GCA, a biopsy is performed. During the biopsy a part of the temporal artery is surgically removed. Diagnosing GCA non invasively with ultrasound would be of benefit to the patient as it is less harmful and avoids risks associated with biopsy and can be performed at the bedside.
Determining the size of tissue particles can be a way of characterizing the tissue as healthy or diseased. This can be done with the use of ultrasound. The ultrasound pulse has a frequency spectrum with a certain center frequency. The center frequency of ultrasound echo is impacted by the size of the tissue particles reflecting the sound. When reflected, the ultrasound frequency spectrum will get a lower center frequency. The change in center frequency is larger for larger tissue particles and smaller for smaller tissue particles. The center frequency shift (CFS) is the measured center frequency compared to a reference frequency. The arrows in Figure 1 points out the the center frequency shift (CFS). The upper image is the spectrum from very small scatterers compared to the wavelength of the ultrasound (reference spectrum) and the lower image is the spectrum from large scatterers.
The method has been evaluated in an ex vivo study showing promising results to differentiate GCA positive from GCA negative arteries. The next step is to eveluate the method in vivo. However, a difficulty when in vivo measurements are made, is that there is always some additional tissue between the transducer and tissue of interest. This additional tissue causes a gradual, depth dependant lowering of the ultrasounds center frequency, so called frequency attenuation. The purpose of this thesis was to study the frequency attenuation and how to compensate for it, so it does not influence the measurements from the tissue of interest. A graphical user interface was also developed as a tool to help clinicians with analysing the center frequency measurements and compensating for the frequency attenuation.
As a first step it was necessary to study the behaviour of the frequency attenuation, if it is linear and if the same general compensation can be done for all patients or if the compensation has to be done individually. For this purpose, the average of all patient’s frequency attenuation in the tissue between the ultrasound transducer and the temporal artery was calculated and plotted. Figure 2 shows the average frequency attenuation of the patients +/-2 standard deviations. The frequency attenuation curve was compared to the frequency attenuation in a material designed to resemble tissue to determine which characteristics were due to tissue and which were due to the instrumentation.
The frequency attenuation was found to be approximately linear, however it varies between patients. It was concluded that it is not possible to use a standardized slope for all patients, because the variation in frequency attenuation would affect the measured CFS too much. Instead, the frequency attenuation should be calculated individually for all patients. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9069342
- author
- Sandell, Karolina LU
- supervisor
-
- Tobias Erlöv LU
- organization
- course
- BMEM01 20212
- year
- 2021
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- additional info
- 2021-21
- id
- 9069342
- date added to LUP
- 2022-01-21 11:56:40
- date last changed
- 2022-01-21 11:56:40
@misc{9069342,
abstract = {{Giant cell arteritis is a disease the affects the arteries, for example the temporal artery. When affecting the temporal artery, it can cause serious consequences such as blindness and stroke. The existing methods for diagnosing the disease are invasive, time consuming and costly. Ultrasound would therefore be an attractive diagnostic alternative providing a lot of benefits. Information about the characteristics of tissue can be obtained from the frequency spectra of the ultrasound echo pulse. This can be used to distinguish diseased tissue from healthy tissue.
When using this method in in vivo studies, the tissue, for example the skin, between the ultrasound transducer and the tissue being investigated also impacts the frequency spectra of the ultrasound pulse. This project examines this impact and how to compensate for it so that it does not influence the measurements of the actual tissue being investigated. A graphical user interface is also developed as a tool for evaluating measurement data obtained during the in vivo study.
It was found that the frequency attenuation in the tissue between the skin and the tissue being investigated can be approximated as linear. When compensating for this attenuation it is not possible to use a general compensation curve for all patients. The compensation has to be done individually for each patient.}},
author = {{Sandell, Karolina}},
language = {{eng}},
note = {{Student Paper}},
title = {{Compensating for ultrasound frequency attenuation in tissue when determining tissue effective particle size}},
year = {{2021}},
}