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J C Bamber

Publications and source records attributed to J C Bamber.

At least 19 recordsLinked to original sources
PubMed1999

Evaluation of soft-tissue masses using segmented color Doppler velocity images: preliminary observations.

OBJECTIVE: We report our initial experience with segmented color Doppler velocity-based estimates of tumor vascularity for various histogically proven soft-tissue masses. SUBJECTS AND METHODS: Color Doppler sonography of 23 histologically proven masses in 22 patients was performed. Digital color Doppler images were acquired directly off the scanner output or from video recordings and stored on a personal computer as 24-bit gray-scale and color composite images. A color Doppler velocity segmentation and analysis algorithm was applied to the digital images, from which we calculated the normalized percentage of color Doppler area. Normalization was determined by expressing color Doppler area as a percentage of the area enclosed by a preselected region of interest. We also calculated mean percentage, SD, and cumulative distribution of color Doppler area, relative to a fixed threshold, for the acquired image data sets. RESULTS: Estimates of mean percentage of color Doppler area showed a dynamic range of at least two or three orders of magnitude between lowest and highest values obtained. A scatterplot of mean percentage of color Doppler area versus SD of percentage of color Doppler area showed a linear monotonic relationship (r2 = .92), illustrating increasing vascular heterogeneity with mean vascularity. Preliminary data also suggest the presence of at least two distinct groups of masses (p < .0001) based on these vascularity estimates. One group corresponds to high-grade lesions in which tumor angiogenesis is expected to be important in predicting biologic behavior. The second group appeared to have little or no relationship to tumor vascularity or was of an intermediate (or lower) histologic grade. CONCLUSION: Quantitative color Doppler estimates of tumor vascularity can be obtained over a wide dynamic range. Such estimates provide a mechanism to assess vascular heterogeneity of soft-tissue tumors. Preliminary data suggest that two biologically distinct groups of masses may be separable on the basis of quantitative velocity-based estimates of tumor vascularity as obtained from color Doppler sonography.

Adolescent↗
PubMed1996

Microbubble contrast agent for color Doppler US: effect on breast masses. Work in progress.

PURPOSE: To evaluate the effects of a new microbubble contrast agent for ultrasound (US) on breast masses. MATERIALS AND METHODS: Thirty-four patients underwent color Doppler US before and after intravenous injection of a "contrast agent" containing microbubbles. The authors subjectively evaluated the increase in intensity of the Doppler signals, the changes in the vascular patterns, and the timing of the transit of the microbubble bolus. The diagnostic confidence was assessed before and after administration of contrast material. RESULTS: After contrast material injection, there was greater and longer signal enhancement in the cancers than in the benign lesions. The cancers displayed characteristic vascular morphologic features, with more additional vessels visualized in relation to the lesion and a greater increase in vascular tortuousity. Shunts between vessels were demonstrated in all cancers but were not seen in any benign lesion. The diagnostic confidence increased with use of the contrast agent. The appearance at contrast-enhanced US led to a change in the US diagnosis in four patients. This increased both sensitivity and specificity to 100%. CONCLUSION: Injection of a microbubble agent enabled accurate differentiation of benign masses from carcinomas.

Adult↗
PubMed1995

Segmentation and analysis of colour Doppler images of tumour vasculature.

A technique has been developed to segment (separate), from a digitized colour Doppler video image, the colour and greyscale information and then to estimate from the colour information the original mean Doppler frequency shift data from which the image was created. The remapped velocity image is then analysed to extract numerical features of the tumour vasculature. The present version of the software is set-up to work for an Acuson 128 colour Doppler system using the V4 colour scale, although it should work well with any system which modulates only two colours for each flow direction and displays a colour calibration scale at the side of the image. Accuracy of classification of greyscale, colour and flow direction was estimated as being in the region of 95% for typical breast tumour images. The degree of agreement between the remapped colour velocity values and those stated by the scanner at the same image locations was evaluated in terms of the linearity of the relationship (> 99%), precision (better than +/- 5%) and accuracy (better than 7.6%). We investigated the value, for diagnosis and assessment of response of, a variety of characteristics of the displayed vascularity. At present, the software calculates the following vascular image features within any region of interest defined by the operator: mean displayed velocity, maximum displayed velocity, standard deviation of displayed velocity, total area occupied by colour signal, percentage area occupied by colour signal, area integral of displayed velocity and the total displayed velocity per unit area.

Algorithms↗
PubMed1995

Ultrasonic propagation properties of excised human skin.

Eight human skin samples were excised postmortem from the upper and lower back, chest and abdomen from two cadavers. The acoustical speed, attenuation and backscatter were measured as a function of frequency (20 to 30 MHz) at 100 positions on a uniform grid over a cross-sectional slice through each sample with the sound incident in a direction parallel to the skin surface. Measurements were made at 24 +/- 0.5 degrees C. Samples were then frozen, cut and stained for histological examination and quantification of fibrous proteins and fat content. The mean attenuation coefficients obtained for whole skin agreed well with previously published results. Employing the model alpha = alpha 1f" where alpha is the attenuation coefficient in decibels per centimeter, alpha 1 is the value of the attenuation coefficient at 1 MHz and f is frequency raised to the power n, mean values (+/- 1 standard deviation) for epidermis were alpha 1 = 0.44 +/- 0.26 and n = 1.55 +/- 0.12, and for dermis alpha 1 = 0.264 +/- 0.17 dB cm-1 and n = 1.69 +/- 0.084. Using a similar model the mean backscatter coefficient was defined by mu 1 = (5.01 +/- 25.76) x 10(-8) Sr-1 cm-1, n = 3.77 +/- 1.5 for the epidermis, and mu 1 = (1.79 +/- 19.5) x 10(-6) and n = 2.76 +/- 1.4 for the dermis. The speed of sound values fell within the range to be found in the literature with a mean value in the epidermis of 1645 m s-1 and in the dermis of 1595 m s-1. Significant, strong correlation existed between the spatially averaged fibrous protein content in the epidermis and dermis and the spatially averaged integrated attenuation measurements. Likewise, strong correlation existed between integrated backscatter and fibrous protein content in the epidermis but not in the dermis. Further research is required to confirm these preliminary findings and to evaluate the role of collagen fibre orientation as a source of variation in the backscattering coefficient of dermis.

Abdomen↗
PubMed1995

Colour DOPPLER image analysis for tissue vascularity and perfusion: a preliminary clinical evaluation.

An automated system for measuring features of colour Doppler (CD) images has been examined for its ability to measure tissue perfusion in vivo under conditions of diffuse vascularity. Seven statistical features were extracted from CD images of human calf muscle and compared with the arterial input measured by plethysmography. It was found that, when appropriate scanning procedures are employed, good correlation is achieved with arterial input (r = 0.96 to 0.99). Ultrasound beam angle was important, even for the assessment of "colour area." A sensitive velocity scale was ideal for "percentage colour" (r = 0.979). "Mean colour velocity" correlates well with arterial input (r = 0.979) when the volocity scale was optimised for each CD scan. "Integrated colour velocity per unit area" was more responsive when using a variable velocity scale (r = 0.99) than a fixed velocity scale (r = 0.98), but was less responsive to low flow. Automated CD analysis speeds up the process of quantitative assessment of tissue vasculature and perfusion. It is therefore essential for the analysis of dynamic studies of ultrasound contrast agents and serial examinations when monitoring response to therapy.

Arteries↗
PubMed1995

Automated quantification of color Doppler signals: a preliminary study in breast tumors.

PURPOSE: To quantify color Doppler (CD) signals reflected by breast lesions to improve differential diagnosis and serial comparisons. MATERIALS AND METHODS: Frame-grabbed color-capture scans were remapped to original velocities on a pixel-by-pixel basis for statistical analysis. Total CD area and its percentage, peak and mean velocities, standard deviation of velocity, and integral CD velocity and its percentage were calculated. These indexes were applied to scans of 44 cancers, 16 fibroadenomas, and 14 benign breast changes in 74 patients. RESULTS: With the region of interest confined to the lesion and a 5-mm margin, no CD signals were reflected by the benign breast changes. All carcinomas and 12 fibroadenomas (those that were vascular) reflected CD signals, and, except for mean and peak velocity, all scores for cancers were significantly higher than for fibroadenomas (P < .0001). Integral CD velocity was the best discriminator, with no overlap between carcinomas (range, 1,128-50,228 cm3/sec) and fibroadenomas (range, 0-1,027 cm3/sec). CONCLUSION: Automatic CD quantification improved differential diagnosis of breast masses.

Adult↗
PubMed1995

Adaptive speckle reduction for improving the differential diagnosis of breast lesions.

Adaptive speckle reduction could mask diagnostic features and adversely affect diagnosis of focal breast lesions. Four radiologists assessed focal breast lesions (29 malignant and 31 benign) by blind review of representative static B-mode scans before and after adaptive speckle reduction processing, scoring 14 diagnostic features for breast cancer and recording their opinions on the diagnosis and on how adaptive speckle reduction affected interpretation of each feature. No adverse affect on diagnosis of malignant (P = 0.756) or benign (P = 1.000) breast lesions was found, despite some differences in scoring of the diagnostic features after adaptive speckle reduction. Observer recognition of most diagnostic features was easier after adaptive speckle reduction (e.g., edge definition [50% of cases], edge regularity [40%], lesion texture [44%], and lesion echogenicity [35%]).

Adult↗
PubMed1994

Breast carcinoma: measurement of tumor response to primary medical therapy with color Doppler flow imaging.

PURPOSE: To assess the ability of color Doppler flow imaging to help evaluate the response of breast cancer to medical therapy. MATERIALS AND METHODS: Thirty-four patients with large or centrally located breast carcinomas were studied. All tumors had been treated medically. Tumor size was assessed at clinical examination, volume at B-mode ultrasound (US), and vascularity at color Doppler flow imaging. The changes seen during the treatment course were cross compared and correlated with final tumor response. RESULTS: In 97 of the 126 treatment cycles (77%), changes in vascularity were concordant with changes in the size of the tumors (reduction in the vascularity with response to therapy and an increase in tumor size with lack of response or progression). Changes seen at color Doppler flow imaging occurred at least 4 weeks before those seen at clinical and B-mode US examination in 40% and 38% of cases, respectively. Changes in vascularity could be assessed in every patient. CONCLUSION: Color Doppler flow imaging can help assessed and predict the response of breast cancer to medical treatment.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Acoustic properties of lesions generated with an ultrasound therapy system.

Methods for quantitative imaging of ultrasound propagation properties were applied to the examination of the acoustic appearance of lesions generated by high intensity focused ultrasound in excised pig livers. Single lesions, about 10 mm maximum diameter by 30 mm long, were created in each of six liver specimens. Two dimensional images (32 by 32 points) of sound speed, mean attenuation coefficient (as a function of frequency in the range 3 to 8.5 MHz) and mean backscattering coefficient (5 to 8 MHz) were obtained in 7 mm thick sections of tissue, cut to include a cross-section through the lesion. Images of these properties, presented alongside surface photographs of the samples, provided a qualitative demonstration that attenuation coefficient was the most useful and backscattering coefficient was the least useful acoustic parameter for visualizing such lesions. Quantitatively the data demonstrated significant increases in attenuation coefficient and sound speed in lesioned liver relative to normal, whereas backscattering was shown not to change in a significant manner except when undissolved gas is the mechanism for increased acoustic scattering. Samples where gas was not fully removed following lesion production gave significant increases in backscattering at the lesion centre, but the shape and size of regions of high backscattering coefficient corresponded poorly with the shape and size of the lesions, unlike attenuation and sound speed for which such correspondence was good.

Acoustics↗
PubMed1993

Compensation for the signal processing characteristics of ultrasound B-mode scanners in adaptive speckle reduction.

A systematic method to compensate for nonlinear amplification of individual ultrasound B-scanners has been investigated in order to optimise performance of an adaptive speckle reduction (ASR) filter for a wide range of clinical ultrasonic imaging equipment. Three potential methods have been investigated: (1) a method involving an appropriate selection of the speckle recognition feature was successful when the scanner signal processing executes simple logarithmic compressions; (2) an inverse transform (decompression) of the B-mode image was effective in correcting for the measured characteristics of image data compression when the algorithm was implemented in full floating point arithmetic; (3) characterising the behaviour of the statistical speckle recognition feature under conditions of speckle noise was found to be the method of choice for implementation of the adaptive speckle reduction algorithm in limited precision integer arithmetic. In this example, the statistical features of variance and mean were investigated. The third method may be implemented on commercially available fast image processing hardware and is also better suited for transfer into dedicated hardware to facilitate real-time adaptive speckle reduction. A systematic method is described for obtaining ASR calibration data from B-mode images of a speckle producing phantom.

Algorithms↗
PubMed1993

High frequency, high resolution B-scan ultrasound in the assessment of skin tumours.

Sixteen skin tumours and one BCG vaccination granuloma were examined by 20-MHz B-scan ultrasound. Images were compared with closely matched histological sections of excised lesions. The correlation between histology and ultrasound was excellent for maximum tumour depth measurements (r = 0.96, P < 0.0001), but less good for maximum width (r = 0.84, P < 0.0001) because of the elastic contraction of tissue at excision. Architectural detail of lesions on histological sections corresponded well with that on ultrasound images. There was a good correlation for heterogeneity (collagen distribution vs. echo pattern (r = 0.86, P < 0.0001)), and between collagen content and echogenicity of lesions (r = 0.69, P < 0.003). Strong correlations were also obtained for echogenicity vs. spacing of collagen bundles (r = -0.65, P < 0.005), echogenicity vs. collagen bundle size (r = 0.58, P < 0.02), and echogenicity vs. cellularity (r = -0.68, P < 0.003). Results for dermatofibroma were atypical, due to paradoxical low internal echogenicity and increased echo absorption. B-scanning is a reliable non-invasive method for assessing tumour dimensions, and has potential for the study of tumour characteristics for diagnostic purposes.

Adult↗
PubMed1993

Breast diseases: color Doppler US in differential diagnosis.

PURPOSE: To subjectively and semiquantitatively evaluate color Doppler signals on images of breast lesions. MATERIALS AND METHODS: A 5-MHz ultrasound (US) system was used to examine 210 new breast lesions. Signals were evaluated subjectively with an analog scale. A semiquantitative scoring system involved analysis of the average number of vessels per square centimeter and average density of color pixels. RESULTS: Vessels were detected in 57 of 58 cancers (mean, 0.11 vessels per square centimeter, occupying 1.76% of the scan area). Color Doppler scores had no correlation with conventional prognostic indicators such as lymph node status or survival. Fewer vessels per square centimeter (mean, 0.06) occupying a smaller area (mean, 0.41%) were detected in the five fibroadenomas (n = 36) that showed color Doppler signals. Most cases (99 of 104 [96%]) of benign breast changes had no color Doppler signals. CONCLUSION: Color Doppler signals in a lesion otherwise thought to be benign should prompt a biopsy, while the absence of signals in an indeterminate lesion is reassuring.

Adenofibroma↗
PubMed1992

Visual impact of adaptive speckle reduction on US B-mode images.

Adaptive speckle reduction, which is designed to improve image contrast, dramatically alters the familiar appearance of the ultrasonographic B-mode scan. The acceptability to radiologists of this alternative method of display was assessed. Four experienced radiologists selected B-mode scans from 83 liver and 71 breast examinations and graded the change in diagnostically important features after adaptive speckle reduction. There was no loss of important anatomic detail in the smoothed images and a net reduction in image artifacts. Removal of speckle noise improved definition of lesion margins in 38.3% of cases and enhanced visibility of metastases in 35.4% of liver studies and 7.7% of breast lesions. In 42.1% of cases, the textural information in the image was judged to be enhanced. Image information in general was said to be better seen in 49.5% of cases. The preliminary radiologic experience with speckle-reduced B-mode echograms is favorable and does not indicate generation of any substantial image artifacts.

Breast Neoplasms↗
PubMed1991

Real-time implementation of coherent speckle suppression in B-scan images.

Early experiences of new forms of adaptive filtering for ultrasound speckle reduction and parametric imaging, using off-line conventional digital processing, have been sufficiently encouraging to warrant examining the feasibility of implementing specific algorithms in real-time. A hardware two-dimensional real-time filter is described which consists of a hybrid digital/analogues system in which the video signal from any scanner is sampled to 256 points per line and passed sequentially through a series of shift registers, in order to derive a 5 x 5 window of values which surrounds the image point currently being processed. These 25 video signals are then used as inputs to an analogue processor, which provides the filtered output. The real-time processed images show clear evidence of speckle smoothing without blurring of tissue structural information but possess limited pixel resolution.

Filtration↗
PubMed1991

What might echography learn from image science?

We review the current state of knowledge of the processes by which the information content of ultrasonic pulse-echo images is transferred to an observer, to the point of contributing to diagnostic judgments. As systematic knowledge in this specific field is rather sparse, we present relevant information and techniques derived from other areas of image science, both medical and otherwise. Quantitative measures both of the information content of ultrasonic and other images and of their characteristic noise content are first considered. An account is then given of the relevant aspects of human visual psychophysics, with particular reference to perception of contrast and detail, image texture, movement and colour, again with emphasis on documenting quantitative aspects of such behaviour. Against this background, we consider the efficiency, in current practice, of image information transfer to a human observer, how and to what extent this could be improved by changes in practice and, in particular, in what situations substantial innovations in machine processing of image data would be expected to improve human performance. It is suggested that several problems in the field may provide a worthwhile and challenging scope for future research.

Humans↗
PubMed1991

A new coaxial needle for pre-operative localization of breast abnormalities.

A new coaxial needle, containing a retractable anchoring wire with a helical tip, has been developed for purposes of mammographic and sonographic localization of non-palpable suspicious breast abnormalities before surgical excision. The helically shaped tip provides the needle with a number of potential advantages over other currently available localization needles. During in vitro comparisons with other needles quantitative and qualitative evidence was obtained to suggest that the new needle can be expected to have improved anchoring capability, be deflected less by tough fibrous tissue interfaces and be more visible sonographically. The anchoring wire can also be retracted and repositioned. Preliminary clinical experience with the needle was consistent with these expectations.

Animals↗