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Up to the time when Ian Donald started to experiment with ultrasound in Glasgow there had already... more Up to the time when Ian Donald started to experiment with ultrasound in Glasgow there had already been many significant developments in diagnostic applications of ultrasound around the world. A number of researchers had managed to acquire industrial flaw detectors and publish the results of their A-mode investigations of tissues. In 1949, R P McLaughlin and G N Guastavino at the Argentinian laboratory of the American electronics company RCA, published a paper describing their own pulse echo instrument for detecting foreign objects in tissue, including the example of a stone embedded in an excised kidney [1]. In the same year, George Ludwig, a medical officer, and Francis Struthers, a physicist, both at the Naval Medical Research Institute in Bethseda, Maryland, measured the acoustic properties of a range of tissues and demonstrated gallstones implanted in dogs [2]. Also in 1949, John Wild, an English surgeon working at the University of Minnesota in the USA, measured changes in bowe...
BMUS Bulletin, 1999
Over the last year or so, several major manufacturers of ultrasound scanners have brought out mac... more Over the last year or so, several major manufacturers of ultrasound scanners have brought out machines equipped with a new grey-scale imaging option called "tissue harmonic imaging", or THI for short. Although this new technique has only been in use for a relatively short period of time, it has already established itself as an important tool in a number of clinical applications, most notably in the field of echocardiography', THI has proved to be particularly useful with patients who were considered to be "difficult to image" using conventional B-mode imaging (e.g. obese patients).
European Journal of Ultrasound, 1995
Ultrasound in Medicine & Biology, 1978
Abstract It is desirable to be able to measure power output of diagnostic ultrasonic transducers ... more Abstract It is desirable to be able to measure power output of diagnostic ultrasonic transducers for both technical and biological reasons. Design criteria for an instrument to fulfill this purpose on a routine basis are suggested. Previous approaches are discussed in relation to these criteria and a new instrument design is presented. This is based on a measurement of radiation force using a null system, with a magnetic restoring force controlled by a pair of photo-detectors. The method of calibration is described and a selection of field results obtained with the prototype instrument are presented. Methods for applying the same principal to beam plotting, and modifying the instrument for use with therapy machines are also described.
Diagnostic Ultrasound
Introduction The basic principles of B-mode scanning were introduced in Chapter 1. The way the be... more Introduction The basic principles of B-mode scanning were introduced in Chapter 1. The way the beam is formed and swept through the patient (scanned) in different types of scanner will now be described in more detail. The transducer is the device that actually converts electrical transmission pulses into ultrasonic pulses and, conversely, ultrasonic echo pulses into electrical echo signals. The simplest way to interrogate all the scan lines that make up a B-mode image is to physically move the transducer so that the beam is swept through the tissues as the pulse–echo cycle is repeated. This was the original method used but it has been superseded by electronic scanning methods which use multi-element array transducers with no moving parts. Array transducers allow the beam to be moved instantly between positions, and give the additional benefit of allowing the shape and size of the beam to be changed to suit the needs of each examination. The beam-former is the part of the scanner that determines the shape, size and position of the interrogating beams by controlling electrical signals to and from the transducer array elements. In transmission, it generates the electrical signals that drive each individual transducer element, and in reception it combines the individual echo sequences received by all the transducer elements into a single echo sequence.
Diagnostic Ultrasound, 2001
Physics in Medicine and Biology, 1991
The reconstruction of the speed-of-sound distribution within a target can be achieved by CT techn... more The reconstruction of the speed-of-sound distribution within a target can be achieved by CT techniques from measurements on transmitted ultrasonic pulses. The mathematical relationship between speed-of-sound imaging and the conventional CT situation is explained. An experimental system, which has been developed to investigate speed-of-imaging and other forms of in-vivo ultrasound CT, is described, along with the techniques used for data acquisition and image reconstruction. These include measurement of pulse time-of-flight by the threshold or cross-correlation methods. Techniques for reducing artifacts in speed-of-sound images are also described, such as median filtering and modified Shepp-Logan filtering. These techniques have been used to obtain high quality speed-of-sound images of various phantoms. Images of tissue in-vitro have been less satisfactory, because of refraction and attenuation effects. Ways of overcoming these difficulties in an improved system are proposed.
Physics in Medicine and Biology, 1991
The factors limiting the resolution achievable with array-based imaging methods are considered. T... more The factors limiting the resolution achievable with array-based imaging methods are considered. The limitations on beamwidth and field of view for beam scanning systems are first examined using plane wave diffraction theory, treating focusing and any array curvature as separable to the plane wave analysis. It is found that in all cases the number of half-beamwidths (maximum to null) across the field of view cannot exceed the number of electrically addressable elements in the array. The minimum beamwidth achievable by strong focusing is shown to be limited to twice the inter-element pitch. Digital reconstruction is then considered as an alternative to beam scanning. Here the number of image points recoverable across the field of view is equal to the number of elements in the array. The mathematical equivalence of the two methods is demonstrated, and the inference is made that the half-beamwidth represents a fundamental measure of lateral resolution. Alternative array configurations, suitable for CT methods, are then compared to probe arrays and it is found that the total number of resolution cells within a two-dimensional image is dependent on the pulse length and number of elements, rather than on the array configuration and imaging method. This again reveals the fundamental similarity of the various methods, essentially in combining position line information from the separate elements, albeit in different orders. Finally an expression for the information capacity of a scanning system is presented which relates the limitations on spatial and contrast resolution to the bandwidth and dynamic range of the system and the number of elements in the array.
Physics in Medicine and Biology, 1993
The Northern Regional Medical Physics Department has been involved in measurement of the acoustic... more The Northern Regional Medical Physics Department has been involved in measurement of the acoustic output of diagnostic ultrasound equipment for several years. As the complexity of diagnostic ultrasound equipment has increased, so have the problems of measuring the acoustic outputs of this equipment in the field. Measurements made in the field are often made on unfamiliar pieces of equipment and under tight constraints of time. In these circumstances the magnitude and the conditions under which the true maximum Ispta value occurs may not always be found. The aim of a measurement protocol is therefore to facilitate the measurement of Ispta in the field, so that the measured maximum Ispta value is as close as possible to the 'true maximum' Ispta value. To be of practical benefit the protocol must be succinct and easy to use, as well as applicable to most if not all types of scanner. Our experience has led us to believe that this is possible and that the benefits of a well designed measurement protocol will far outweigh any disadvantages. The development of two measurement protocols is discussed in this paper. The time required to carry out each measurement depends on the number of assumptions made about the operation of the scanner in the protocol used. The first protocol makes very few assumptions about the operation of a scanner; the results from measurements made using this protocol can be used to assess the validity of the much larger number of assumptions made in the second protocol. The results from measurements on three types of scanner using the two protocols are presented. The results demonstrate the validity of most of the assumptions made by the protocols and the potential benefits of using a protocol for measurement of maximum Ispta in the field in terms of reduced measurement time and greater consistency.
The British Journal of Radiology, 1992
The use of duplex ultrasound with colour flow mapping is compared with that of intravenous digita... more The use of duplex ultrasound with colour flow mapping is compared with that of intravenous digital subtraction angiography (IVDSA) in the investigation of carotid and vertebral artery disease. Ninety-nine carotid and vertebral arteries were examined independently by IVDSA and ultrasound for location and degree of disease in 30 men (mean age 58) and 20 women (mean age 53). For purposes of comparison the carotid tree was divided into six segments. In 46% of cases no disease was detected by either modality. In 36% of cases where disease was found, ultrasound found mild disease in arteries reported as normal by IVDSA. Both modalities detected the six cases of total occlusion found in the study. IVDSA underestimated five cases of major disease found by ultrasound at the bifurcation or in the bulb. Overall agreement in grading vessel segments was good, with 74.5% in complete agreement and 90.3% grading stenoses to within +/- 25% of the other modality. There was good qualitative agreement in the findings for vertebral arteries. In four patients conventional arteriography was also available for comparison.
The British Journal of Radiology, 1973
Experience in the estimation of the volumes of enlarged prostates by ultrasonic section scanning ... more Experience in the estimation of the volumes of enlarged prostates by ultrasonic section scanning indicates that this technique is more reliable than existing methods, including—rectal examination, cystoscopy, bimanual examination and contrast radiography. Our investigations suggest that the technique described here is capable of accuracy of the order of 20–30 per cent depending on the time and care exercised by the operator, and on the anatomical peculiarities of the patient at the time of the scan (e.g. obesity, size, and shape of prostate, etc.).
Up to the time when Ian Donald started to experiment with ultrasound in Glasgow there had already... more Up to the time when Ian Donald started to experiment with ultrasound in Glasgow there had already been many significant developments in diagnostic applications of ultrasound around the world. A number of researchers had managed to acquire industrial flaw detectors and publish the results of their A-mode investigations of tissues. In 1949, R P McLaughlin and G N Guastavino at the Argentinian laboratory of the American electronics company RCA, published a paper describing their own pulse echo instrument for detecting foreign objects in tissue, including the example of a stone embedded in an excised kidney [1]. In the same year, George Ludwig, a medical officer, and Francis Struthers, a physicist, both at the Naval Medical Research Institute in Bethseda, Maryland, measured the acoustic properties of a range of tissues and demonstrated gallstones implanted in dogs [2]. Also in 1949, John Wild, an English surgeon working at the University of Minnesota in the USA, measured changes in bowe...
BMUS Bulletin, 1999
Over the last year or so, several major manufacturers of ultrasound scanners have brought out mac... more Over the last year or so, several major manufacturers of ultrasound scanners have brought out machines equipped with a new grey-scale imaging option called "tissue harmonic imaging", or THI for short. Although this new technique has only been in use for a relatively short period of time, it has already established itself as an important tool in a number of clinical applications, most notably in the field of echocardiography', THI has proved to be particularly useful with patients who were considered to be "difficult to image" using conventional B-mode imaging (e.g. obese patients).
European Journal of Ultrasound, 1995
Ultrasound in Medicine & Biology, 1978
Abstract It is desirable to be able to measure power output of diagnostic ultrasonic transducers ... more Abstract It is desirable to be able to measure power output of diagnostic ultrasonic transducers for both technical and biological reasons. Design criteria for an instrument to fulfill this purpose on a routine basis are suggested. Previous approaches are discussed in relation to these criteria and a new instrument design is presented. This is based on a measurement of radiation force using a null system, with a magnetic restoring force controlled by a pair of photo-detectors. The method of calibration is described and a selection of field results obtained with the prototype instrument are presented. Methods for applying the same principal to beam plotting, and modifying the instrument for use with therapy machines are also described.
Diagnostic Ultrasound
Introduction The basic principles of B-mode scanning were introduced in Chapter 1. The way the be... more Introduction The basic principles of B-mode scanning were introduced in Chapter 1. The way the beam is formed and swept through the patient (scanned) in different types of scanner will now be described in more detail. The transducer is the device that actually converts electrical transmission pulses into ultrasonic pulses and, conversely, ultrasonic echo pulses into electrical echo signals. The simplest way to interrogate all the scan lines that make up a B-mode image is to physically move the transducer so that the beam is swept through the tissues as the pulse–echo cycle is repeated. This was the original method used but it has been superseded by electronic scanning methods which use multi-element array transducers with no moving parts. Array transducers allow the beam to be moved instantly between positions, and give the additional benefit of allowing the shape and size of the beam to be changed to suit the needs of each examination. The beam-former is the part of the scanner that determines the shape, size and position of the interrogating beams by controlling electrical signals to and from the transducer array elements. In transmission, it generates the electrical signals that drive each individual transducer element, and in reception it combines the individual echo sequences received by all the transducer elements into a single echo sequence.
Diagnostic Ultrasound, 2001
Physics in Medicine and Biology, 1991
The reconstruction of the speed-of-sound distribution within a target can be achieved by CT techn... more The reconstruction of the speed-of-sound distribution within a target can be achieved by CT techniques from measurements on transmitted ultrasonic pulses. The mathematical relationship between speed-of-sound imaging and the conventional CT situation is explained. An experimental system, which has been developed to investigate speed-of-imaging and other forms of in-vivo ultrasound CT, is described, along with the techniques used for data acquisition and image reconstruction. These include measurement of pulse time-of-flight by the threshold or cross-correlation methods. Techniques for reducing artifacts in speed-of-sound images are also described, such as median filtering and modified Shepp-Logan filtering. These techniques have been used to obtain high quality speed-of-sound images of various phantoms. Images of tissue in-vitro have been less satisfactory, because of refraction and attenuation effects. Ways of overcoming these difficulties in an improved system are proposed.
Physics in Medicine and Biology, 1991
The factors limiting the resolution achievable with array-based imaging methods are considered. T... more The factors limiting the resolution achievable with array-based imaging methods are considered. The limitations on beamwidth and field of view for beam scanning systems are first examined using plane wave diffraction theory, treating focusing and any array curvature as separable to the plane wave analysis. It is found that in all cases the number of half-beamwidths (maximum to null) across the field of view cannot exceed the number of electrically addressable elements in the array. The minimum beamwidth achievable by strong focusing is shown to be limited to twice the inter-element pitch. Digital reconstruction is then considered as an alternative to beam scanning. Here the number of image points recoverable across the field of view is equal to the number of elements in the array. The mathematical equivalence of the two methods is demonstrated, and the inference is made that the half-beamwidth represents a fundamental measure of lateral resolution. Alternative array configurations, suitable for CT methods, are then compared to probe arrays and it is found that the total number of resolution cells within a two-dimensional image is dependent on the pulse length and number of elements, rather than on the array configuration and imaging method. This again reveals the fundamental similarity of the various methods, essentially in combining position line information from the separate elements, albeit in different orders. Finally an expression for the information capacity of a scanning system is presented which relates the limitations on spatial and contrast resolution to the bandwidth and dynamic range of the system and the number of elements in the array.
Physics in Medicine and Biology, 1993
The Northern Regional Medical Physics Department has been involved in measurement of the acoustic... more The Northern Regional Medical Physics Department has been involved in measurement of the acoustic output of diagnostic ultrasound equipment for several years. As the complexity of diagnostic ultrasound equipment has increased, so have the problems of measuring the acoustic outputs of this equipment in the field. Measurements made in the field are often made on unfamiliar pieces of equipment and under tight constraints of time. In these circumstances the magnitude and the conditions under which the true maximum Ispta value occurs may not always be found. The aim of a measurement protocol is therefore to facilitate the measurement of Ispta in the field, so that the measured maximum Ispta value is as close as possible to the 'true maximum' Ispta value. To be of practical benefit the protocol must be succinct and easy to use, as well as applicable to most if not all types of scanner. Our experience has led us to believe that this is possible and that the benefits of a well designed measurement protocol will far outweigh any disadvantages. The development of two measurement protocols is discussed in this paper. The time required to carry out each measurement depends on the number of assumptions made about the operation of the scanner in the protocol used. The first protocol makes very few assumptions about the operation of a scanner; the results from measurements made using this protocol can be used to assess the validity of the much larger number of assumptions made in the second protocol. The results from measurements on three types of scanner using the two protocols are presented. The results demonstrate the validity of most of the assumptions made by the protocols and the potential benefits of using a protocol for measurement of maximum Ispta in the field in terms of reduced measurement time and greater consistency.
The British Journal of Radiology, 1992
The use of duplex ultrasound with colour flow mapping is compared with that of intravenous digita... more The use of duplex ultrasound with colour flow mapping is compared with that of intravenous digital subtraction angiography (IVDSA) in the investigation of carotid and vertebral artery disease. Ninety-nine carotid and vertebral arteries were examined independently by IVDSA and ultrasound for location and degree of disease in 30 men (mean age 58) and 20 women (mean age 53). For purposes of comparison the carotid tree was divided into six segments. In 46% of cases no disease was detected by either modality. In 36% of cases where disease was found, ultrasound found mild disease in arteries reported as normal by IVDSA. Both modalities detected the six cases of total occlusion found in the study. IVDSA underestimated five cases of major disease found by ultrasound at the bifurcation or in the bulb. Overall agreement in grading vessel segments was good, with 74.5% in complete agreement and 90.3% grading stenoses to within +/- 25% of the other modality. There was good qualitative agreement in the findings for vertebral arteries. In four patients conventional arteriography was also available for comparison.
The British Journal of Radiology, 1973
Experience in the estimation of the volumes of enlarged prostates by ultrasonic section scanning ... more Experience in the estimation of the volumes of enlarged prostates by ultrasonic section scanning indicates that this technique is more reliable than existing methods, including—rectal examination, cystoscopy, bimanual examination and contrast radiography. Our investigations suggest that the technique described here is capable of accuracy of the order of 20–30 per cent depending on the time and care exercised by the operator, and on the anatomical peculiarities of the patient at the time of the scan (e.g. obesity, size, and shape of prostate, etc.).