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Biomedical subjects

D L Buckley

Publications and source records attributed to D L Buckley.

31 records · Page 2Linked to original sources
PubMed1997

Dynamic MR imaging of invasive breast cancer: correlation with tumour grade and other histological factors.

The purpose of this study was to explore the association between dynamic MR enhancement characteristics and histopathological prognostic factors of invasive breast cancer. 53 women with primary invasive breast cancer underwent dynamic contrast enhanced breast MRI. Region of interest (ROI) analysis was performed on synthetic images obtained by kinetic modelling of the dynamic data. Operator-defined, large ROIs and computer-defined, 9-pixel ROIs were selected for each tumour. The relative increase in mean ROI pixel intensity was expressed in the form of enhancement ratios. Univariate and multivariate analyses were performed to explore the association of these ratios with standard histological factors, including tumour size, histopathological classification, histological grade, the presence of extensive in situ component and lymphovascular invasion, multifocal disease, and axillary lymph node status. All enhancement ratios showed significant differences between node-positive and node-negative tumours (max. p = 0.002). However, automated ROI ratios showed less overlap between node-positive and node-negative carcinomas than did large ROI ratios. A strongly significant association was observed between all automated ROI enhancement ratios and histological tumour grade (max. p = 0.001). Based on stepwise multiple regression analysis, node status and histological grade were the only histopathological factors with a significant independent effect on the enhancement characteristics. In summary, there is a strong association between dynamic MR characteristics and two important prognostic markers of invasive breast cancer, namely axillary node status and histological grade. This may allow MRI to be used in pre-operative predictions of tumour behaviour and biological activity.

Adult↗
PubMed1996

Tumour volume determination from MR images by morphological segmentation.

Accurate tumour volume measurement from MR images requires some form of objective image segmentation, and therefore a certain degree of automation. Manual methods of separating data according to the various tissue types which they are thought to represent are inherently prone to operator subjectivity and can be very time consuming. A segmentation procedure based on morphological edge detection and region growing has been implemented and tested on a phantom of known adjustable volume. Comparisons have been made with a traditional data thresholding procedure for the determination of tumour volumes on a set of patients with intracerebral glioma. The two methods are shown to give similar results, with the morphological segmentation procedure having the advantages of being automated and faster.

Brain Neoplasms↗
PubMed1996

Improved peripheral MR angiography with temperature regulation in healthy patients.

Peripheral magnetic resonance (MR) angiography was performed in eight volunteers, with a temperature-controlled water blanket. After warming of the right foot, unobserved vessels became conspicuous in all patients: Average increase in signal intensity was nearly twofold in the major artery and vein depicted. A similar improvement was observed in an examination in one patient with diabetes. Peripheral MR angiography performed after warming provided additional diagnostic information.

Adult↗
PubMed1996

Observer variability in the interpretation of contrast enhanced MRI of the breast.

The purpose of this study was to determine observer variability in the interpretation of contrast enhanced breast MRI and to evaluate its effect on the detection and differentiation of breast cancer. 57 women underwent breast MRI using spin echo and dynamic spoiled gradient-recalled sequences. Images were independently reviewed by three radiologists, two experienced and one newly trained in breast MRI interpretation. One of the experienced readers reviewed all examinations twice. Interpretation was based on lesion conspicuity, signal intensity, contour and enhancement pattern. Contrast uptake was assessed using region of interest (ROI) analysis of the dynamic images and calculation of a maximum enhancement index. Sensitivity and specificity in the diagnosis of malignancy irrespective of disease extent, and in the diagnosis of multifocal malignancy were estimated. 113 lesions were reported. Kappa coefficient estimations showed only a moderate agreement between the two experienced readers in rating morphological characteristics; the agreement between the newly trained reader and the experienced readers was even worse. Moreover, there was significant interobserver and intraobserver variation in the enhancement index measurements. Weighted kappa values indicated good agreement between the experienced readers in lesion and overall interpretation, excellent intraobserver agreement, but substantial disagreement between the newly trained reader and both experienced readers. All readers showed good sensitivity in cancer detection, but specificity was substantially lower. There is significant observer variability and a substantial learning curve in the interpretation of breast MRI, and variability in the ROI analysis of dynamic data. Further efforts to improve the reliability of ROI analysis and image interpretation are needed to help MRI realise its full potential in the clinical management of breast cancer.

Adult↗
PubMed1995

Dynamic gradient-echo and fat-suppressed spin-echo contrast-enhanced MRI of the breast.

PURPOSE: To evaluate heavily T2-weighted, dynamic contrast-enhanced and fat-suppressed magnetic resonance imaging (MRI) of the breast in comparison with conventional imaging and fine needle aspiration cytology (FNAC). PATIENTS AND METHODS: Fifty patients with surgically/pathologically proven breast disease were examined pre-operatively by MRI. The majority, 45 patients, had invasive carcinoma. T1-weighted spin-echo, T2-weighted fast spin-echo (with chemical-shift-selective fat-suppression in 20 cases), rapid dynamic contrast-enhanced gradient-echo and post-contrast fat-suppressed T1-weighted images were obtained. Signal intensity changes during dynamic scanning were assessed qualitatively and quantitatively. Comparison was made with the results of X-ray mammography, ultrasound and fine needle aspiration cytology. RESULTS: Unenhanced MRI was inadequate for determining the location, extent or nature of most lesions even when fat-suppressed T2-weighted images were obtained. Following contrast injection, there was significantly greater enhancement of invasive carcinomas than normal parenchyma. Invasive carcinomas of ductal and lobular subtypes did not differ significantly in their enhancement profiles. Prominent enhancement of the lesion periphery, which was a feature in 33 out of 50 cases (the majority of which were invasive carcinomas) was not due to central tumour necrosis. In four cases, invasive carcinomas which were clearly visible on early dynamic scans could not be identified on post-contrast fat-suppressed images. Lesions that were more numerous or extensive than had been recognised clinically or mammographically were revealed by MRI in 14 patients, though MRI was no more specific than conventional assessment. Invasion of the chest wall was accurately predicted by MRI in three cases. There was excellent correlation between tumour size shown by MRI and histopathology. FNAC was accurate in predicting the final histological diagnosis except in those cases where samples were unsatisfactory. CONCLUSIONS: Contrast-enhanced MRI appears useful in the assessment of suspected malignant breast masses, especially in younger women with predominantly glandular breast tissue. Specificity is no better than FNAC but tumour extent and multifocality are more accurately disclosed than by conventional imaging techniques. Contrast-enhanced chemical-shift-selective fat-suppressed images are sub-optimal in a small proportion of cases (particularly where lesions are located posteriorly) and some benign breast disease may appear misleadingly conspicuous on such images. Morphological features and quantification of lesion enhancement during dynamic scanning presently offer only limited prospects for discrimination between various pathologies. Heavily T2-weighted sequences appear of marginal value.

Adolescent↗
PubMed1995

Dynamic contrast-enhanced magnetic resonance imaging of the breast combined with pharmacokinetic analysis of gadolinium-DTPA uptake in the diagnosis of local recurrence of early stage breast carcinoma.

RATIONALE AND OBJECTIVES: This study was designed to assess the efficacy of dynamic contrast-enhanced magnetic resonance imaging (MRI) of the breast combined with pharmacokinetic analysis of gadolinium (Gd)-DTPA uptake in the diagnosis of local recurrence of early stage breast carcinoma. METHODS: Fifty women treated with breast-conserving surgery and radiotherapy underwent breast MRI. Dynamic magnetic resonance data obtained at four preselected slice locations were analyzed to examine Gd-DTPA uptake based on a pharmacokinetic model using three parameters: wash-in rate, wash-out rate, and amplitude of uptake. Synthetic images were produced from the above parameters and their derivatives--maximum uptake and reciprocal of half the time to maximum. For each region of interest (ROI), median parameter values were calculated. The mean pixel signal intensity of each ROI was plotted against time, and an enhancement index was determined. RESULTS: Sixty ROIs were selected: 49 lesions were benign, and 11, malignant. Significant differences between benign and malignant lesions were found for the enhancement index (P < 0.0001), maximum uptake (P < 0.0001), amplitude of uptake (P < 0.0001), wash-in rate (P = 0.03), wash-out rate (P = 0.01), and the reciprocal of half the time to maximum (P = 0.0005). The respective sensitivities and specificities were as follows: for the enhancement index, 1.00 and 0.96; for maximum uptake, 1.00 and 0.96; for amplitude of uptake, 0.91 and 0.94; for wash-in rate 0.82 and 0.47; for wash-out rate 0.91 and 0.59; and for the reciprocal of half the time to maximum, 1.00 and 0.51. CONCLUSIONS: Dynamic scanning proved essential for the detection and differential diagnosis of local tumor recurrence. Pharmacokinetic analysis of Gd-DTPA uptake can be used to produce parametric images that retain the spatial resolution of the original images while providing additional information about lesion permeability and vascularity, and helping to avoid the observer variability associated with ROI analysis.

Adult↗
PubMed1994

Quantitative analysis of multi-slice Gd-DTPA enhanced dynamic MR images using an automated simplex minimization procedure.

Quantitative analysis of Gd-DTPA enhanced dynamic MR images has potential for discriminating lesions, especially because the introduction of clinical fast imaging techniques has enabled good sampling of the relatively rapid Gd-DTPA wash-in curves. Analysis of such data requires curve fitting to a nonlinear model, which to date has been performed using a nonlinear least squares (NLLS) fitting procedure. However, this method often fails to converge to the appropriate minima without good initial parameter estimates when multi-exponential models are involved, making automated analysis of complete multislice or volume data sets problematic. In this report we demonstrate the robust performance of a simplex minimization procedure compared with NLLS, by the method of Marquardt, using a Monte Carlo simulation. Further, we illustrate the applicability of such a technique to the analysis of dynamic contrast enhanced images on a pixel-by-pixel basis. As a preliminary example, the technique is applied to a breast lesion but is expected to be suitable for examination of many lesion types.

Algorithms↗
PubMed1994

Fingers: three-dimensional MR imaging and angiography with a local gradient coil.

The authors interfaced a 12-cm-diameter local gradient coil with a solenoid radio-frequency coil (2.2-cm internal diameter, 1.4-cm long) to a recalibrated clinical magnetic resonance imaging system. Three-dimensional gradient-echo imaging and phase-contrast angiography were performed on the fingers of five healthy volunteers (four men and one woman, aged 23-33 years). Data sets (256 x 256 x 28) were acquired with spatial resolution of 100 x 100 x 500 microns in 6 minutes 51 seconds. The angiograms clearly delineated blood vessels that were less than 1 mm in diameter.

Adult↗
PubMedDate not supplied

Microvessel density of invasive breast cancer assessed by dynamic Gd-DTPA enhanced MRI.

It has been postulated that the rapid enhancement demonstrated by breast carcinomas after administration of contrast media is a direct result of tumor angiogenesis. However, to date, little quantitative data have been published to support this view. A retrospective study has been undertaken to compare dynamic contrast-enhanced data obtained from 40 patients with microvessel density (MVD) evaluated in specimens immunohistochemically stained with a factor VIII related antigen. The dynamic data were analyzed quantitatively using both simple indices of enhancement and a two-compartment kinetic model. A moderate but significant correlation was demonstrated between initial enhancement and MVD, and this correlation strengthened when node-positive tumors were considered in isolation (r = .77, P < .0005). However, the data showed considerable variability. The enhancement characteristics of the tumors could not be explained solely by their MVD; therefore, MRI cannot be used to predict MVD in vivo. Further work is required to address the exact relationship between contrast-enhanced MRI and tumor angiogenesis.

Adult↗
PubMedDate not supplied

Dynamic MRI of invasive breast cancer: assessment of three region-of-interest analysis methods.

PURPOSE: In this study, three region-of-interest (ROI) analysis methods based on operator-defined and semiautomated sampling of pharmacokinetic breast maps of contrast uptake are described. The observer variability and impact of the methods on the estimated enhancement characteristics of invasive cancer are also presented. METHOD: Fifty-four women with invasive breast cancer underwent dynamic Gd-DTPA-enhanced MRI. ROIs were drawn by two observers on parametric images obtained from compartmental modeling of the dynamic data. Three methods were used: (a) An irregular ROI was drawn to include as much of the enhancing part of the tumor as possible (large ROI); (b) a 12 pixel circular ROI was placed at the most rapidly enhancing part of the large region (small ROI); and (c) a computer algorithm interrogated the large region pixel by pixel using a 9 pixel square mask and selected the region with the highest mean parameter value (semiautomated ROI). RESULTS: Significant observer variability and bias were found in the enhancement measurements using the large ROI method. There was no observer bias associated with the other methods, but the variability of the small ROI method was substantial. An almost perfect observer agreement was achieved using the semiautomated method. The small and semiautomated ROI methods produced significantly higher enhancement ratios than the large ROI method, especially in grade III carcinomas. CONCLUSION: Variability is inherent in subjective ROI analysis, but the semiautomated method of ROI selection and sampling of parameter images of the breast is an efficient and reliable alternative that may allow better standardization of the MR technique.

Adult↗
PubMedDate not supplied

Effect of temporal resolution on the diagnostic efficacy of contrast-enhanced MRI in the conservatively treated breast.

PURPOSE: Our goal was to assess the effect of image acquisition rate on the diagnostic efficacy of contrast-enhanced MRI in the conservatively treated breast. METHOD: Sixty-seven women, treated with breast-conserving surgery and radiotherapy for early-stage breast cancer, were imaged at 1.5 T using a dynamic contrast-enhanced sequence with a temporal resolution of 12 s. Enhancement was recorded over time for the dominant lesion in each patient. Data were subsequently removed to simulate various acquisition rates and the enhancement indexes of benign and malignant lesions were compared. RESULTS: Seventeen patients had confirmed local recurrence and 50 remained disease-free. There were significant differences in the enhancement indexes of benign and malignant lesions 24-264 s after contrast agent administration. Acquisition rate had a negligible effect upon diagnostic efficacy. CONCLUSION: Two image data sets collected before contrast agent administration and between 1.5 and 3.5 min afterward may be sufficient to differentiate recurrent and benign disease.

Adult↗
PubMedDate not supplied

Heterogeneity analysis of Gd-DTPA uptake: improvement in breast lesion differentiation.

PURPOSE: The aim of this study was to assess whether lesion heterogeneity through pixel-by-pixel analysis of contrast-enhanced MR parameter maps would improve breast lesion differentiation. METHOD: Forty-nine female patients with primary tumors of the breast were imaged using contrast-enhanced MRI. The rate of transfer of contrast medium between the lesion and plasma was calculated via compartmental modeling over semiautomatically delineated regions of interest. The distributions of transfer rate values were subdivided into 10 segments for each lesion. The rate of change of the statistical moments of the transfer rate measured over the 10 segments allowed a quantitative measure of heterogeneity. RESULTS: In this patient group of 25 malignant and 25 benign lesions, improved differentiation was achieved by using a measure of lesion heterogeneity. The sensitivity and specificity obtained were 88 and 88%, respectively, compared with 84 and 76% when using the mean value of the transfer rate coefficient. CONCLUSION: Pixel-by-pixel analysis of contrast medium transfer rate maps allows the examination of lesion heterogeneity and offers improved lesion differentiation. The new method used to quantify lesion heterogeneity relies on the manner in which the exchange rate parameter varies when calculated over different segments of the distribution.

Adult↗