The Nakagami distribution was proposed recently for modeling the echo from tissue. In vivo breast data collected from patients with lesions were studied using this Nakagami model. Chi-square tests ...showed that the Nakagami distribution is a better fit to the envelope than the Rayleigh distribution. Two parameters, m (effective number) and /spl alpha/ (effective cross section), associated with the Nakagami distribution were used for the classification of breast masses. Data from 52 patients with breast masses/lesions were used in the studies. Receiver operating characteristics were calculated for the classification methods based on these two parameters. The results indicate that these parameters of the Nakagami distribution may be useful in classification of the breast abnormalities. The Nakagami distribution may be a reasonable means to characterize the backscattered echo from breast tissues toward a goal of an automated scheme for separating benign and malignant breast masses.
High plasticity in the migrations of marine fishes can result from partial migration, where early life conditional responses to nursery conditions carryover into juvenile and adult migrations. ...Striped bass Morone saxatilis movement behaviors during the larval and early juvenile period were investigated for evidence of partial migration through otolith Sr/Ca profile analysis. Striped bass expressed expected behaviors, with contingents remaining in freshwater habitats through the early juvenile period (through 35 mm TL) or moving across the salt front to brackish water habitats (salinity ≥3); still, the range of sizes at which migration occurred was unexpectedly wide. Using a multivariate clustering analysis, 3 distinct size-based migratory contingents were identified. Two of these migrant groups dispersed following metamorphosis to the juvenile stage, while the third (and smallest) dispersed during the larval period. Both tendency to migrate and the size at which movement commenced were related to early growth, with migrants experiencing lower growth than residents. In one year, a high flow event appeared to influence the timing of migration, coinciding with the majority of dispersal events. Expected dividends for migratory juveniles in the form of improved forage (diet and stable isotope analysis), condition and growth were not detected. Partial migration within natal estuaries during ontogeny appears to be a conditional response in striped bass, possibly resulting from the interaction of liability traits and innate thresholds and influenced by environmental conditions.
This paper presents performance comparisons between breast tumor classifiers based on parameters from a conventional texture analysis (CTA) and the generalized spectrum (GS). The computations of ...GS-based parameters from radiofrequency (RF) ultrasonic scans and their relationship to underlying scatterer properties are described. Clinical experiments demonstrate classifier performances using 22 benign and 24 malignant breast mass regions taken from 40 patients. Linear classifiers based on parameters from the front edge, back edge and interior tumor regions are examined. Results show significantly better performances for GS-based classifiers, with improvements in empirical receiver operating characteristic (ROC) areas of greater than 10%. The ROC curves show GS-based classifiers achieving a 90% sensitivity level at 50% specificity when applied to the back-edge tumor regions, an 80% sensitivity level at 65% specificity when applied to the front-edge tumor regions, and a 100% sensitivity level at 45% specificity when applied to the interior tumor regions. (E-mail: donohue@engr.ukg.edu)
Breast cancer diagnosis through ultrasound tissue characterization was studied using receiver operating characteristic (ROC) analysis of combinations of acoustic features, patient age, and ...radiological findings. A feature fusion method was devised that operates even if only partial diagnostic data are available. The ROC methodology uses ordinal dominance theory and bootstrap resampling to evaluate A/sub z/ and confidence intervals in simple as well as paired data analyses. The combined diagnostic feature had an A/sub z/ of 0.96 with a confidence interval of 0.93, 0.99 at a significance level of 0.05. The combined features show statistically significant improvement over prebiopsy radiological findings. These results indicate that ultrasound tissue characterization, in combination with patient record and clinical findings, may greatly reduce the need to perform biopsies of benign breast lesions.
To determine the safety and efficacy of ferumoxtran 10-enhanced magnetic resonance (MR) imaging for diagnosis of metastases to lymph nodes and the clinical usefulness of ferumoxtran 10 in nodal ...staging.
One hundred fifty-two patients were injected with ferumoxtran 10. Readers independently evaluated precontrast MR images by using node size criteria and subjective assessment of other imaging features. Ferumoxtran 10-enhanced MR images were evaluated alone and paired with precontrast images for comparison. The diagnostic performances of precontrast MR size criteria and postcontrast MR imaging were evaluated with receiver operating characteristic (ROC) analysis. Lymph node signal intensity was correlated with histopathologic findings. MR imaging and histopathologic nodal stages were compared.
Node-level sensitivity, specificity, and accuracy of precontrast MR imaging were 54%, 82%, and 68%, respectively, with node size criterion alone; 91%, 51%, and 71%, respectively, with subjective reader assessment; 85%, 85%, and 85%, respectively, with postcontrast MR imaging alone; and 83%, 77%, and 80%, respectively, with paired pre- and postcontrast MR imaging. Compared with size criteria, subjective reader assessment had higher sensitivity but substantially lower specificity. Areas under the ROC curve for pre- and postcontrast MR imaging were 0.76 and 0.83, respectively. Nonmetastatic nodes had significantly lower signal intensity than metastatic nodes on postcontrast T2-weighted MR images (P <.001). Postcontrast nodal staging was significantly more accurate than precontrast nodal staging (P <.01). Headache, back pain, vasodilatation, and urticaria each occurred in 6% of patients.
Ferumoxtran 10-enhanced MR imaging was safe and effective and facilitated improved diagnostic performance. Use of iron oxide-enhanced MR imaging increased the positive predictive value by 20% and the accuracy by 14% compared with reader assessment. Differentiating patients with no nodal metastatic involvement was more reliable with ferumoxtran 10-enhanced MR imaging than with precontrast MR imaging.
Accuracy of T1-weighted chemical-shift MR imaging for the differentiation between benign and malignant adrenal masses was blindly assessed among three radiologists.
MR imaging was performed at 1.5 T ...in 50 patients with 58 adrenal masses, proved benign (n = 38) or malignant (n = 20) based on surgery or growth (malignant) or stable size (benign) for at least 1 year. In-phase spin-echo sequences or in-phase breath-hold fast multiplanar spoiled gradient-recalled echo (FMPSPGR) sequences with a TE of 4.2 msec were compared with opposed-phase breath-hold FMPSPGR sequences with a TR/TE of 35-155/2.2-2.9 and a 90 degrees flip angle for the detection of lipid in adrenal masses. Three radiologists who were blinded to diagnosis and clinical data independently rated the likelihood of a benign adrenal lesion on a five-point scale of confidence.
Mean sensitivity, specificity, and positive predictive value for a definite or probable diagnosis of a benign lesion by the three readers were 87%, 92%, and 95%, respectively. At the highest (definite) confidence of a benign lesion, the mean positive predictive value was 99%, with lower sensitivity (54%). Areas under receiver operating characteristic curves for the three radiologists were .98 (95% confidence interval CI = .94-1.00), .96 (CI = .91-1.00), and .95 (CI = .89-1.00). Interobserver variation for the diagnosis of a benign mass was low (kappa = .79).
Chemical-shift imaging using breath-hold opposed-phase T1-weighted MR images is a reliable and reproducible technique for the diagnosis of most benign adrenal masses at the highest threshold of confidence.
Contrast-enhanced MRI (CE-MRI) of the breast has been investigated for over 10 years. The reports of sensitivity for cancer detection have generally been greater than 90 %. However, estimates of ...specificity have varied greatly. Differing results are due to differences in study populations, technical methods and criteria for interpretation. Early and marked signal rise, detected using dynamic imaging technique following contrast administration, is the MRI hallmark of cancer. However, some malignant lesions may enhance slowly or minimally, and a variety of benign lesions may enhance rapidly with marked signal intensity. High resolution techniques generally requiring longer acquisition times are more likely to depict the slowly enhancing malignancies at the cost of a decrease in specificity due to lack of temporal resolution. This disadvantage may be offset by the improved visualization of lesion morphology with high resolution images. This report reviews the methods and results of the leading investigators of breast MRI.
To assess accuracy of three different magnetic resonance (MR) imaging techniques, including the endorectal coil, in staging prostate cancer.
MR imaging was performed in 213 patients with prostate ...cancer with a conventional body coil, with fat suppression and a body coil, and with an endorectal coil. Radiologists identified tumor invasion into periprostatic tissues, neurovascular bundles, and seminal vesicles. Each technique was evaluated separately, and in a subset of 74 patients the three techniques were evaluated together. Images obtained with the two body-coil techniques were read in combination with images obtained with the endorectal coil (combination A) and alone (combination B).
Overall accuracy for conventional body-coil, fat-suppressed body-coil, and endorectal-coil MR was 61%, 64%, and 54%, respectively. Overall group accuracy for combinations A and B was 57% and 61%. Considerable interreader variability was found for combination A.
No technique was highly accurate for staging early prostate cancer. Individual radiologists did achieve a high degree of staging accuracy with the endorectal-coil and body-coil combination.
The K-distribution had been introduced as a valid model to represent the statistics of the envelope of the backscattered echo from phantom and tissue. This paper investigates the efficacy of the ...parameters of this statistical model; namely, the effective number and the effective cross-section, to characterize breast lesions as benign or malignant. Based on the normalized values of the effective number and the effective scattering cross-section, images containing benign and malignant masses were classified for a data set from 52 patients having breast masses/lesions. The receiver operating characteristic (ROC) curves were then obtained to test the classification based on these two parameters. The results indicate that the parameters of the K-distribution may be useful in classification of the breast lesions as benign and malignant.
Classification of breast masses in ultrasonic B-scan images is undertaken using a multiparameter approach. The parameters are generated on the basis of a non-Rayleigh statistic model of the ...backscattered envelope from the breast tissue. They can be computed automatically with minimal clinical intervention once the location of the mass is known. A new discriminant is developed that combines these parameters linearly. It is seen that this new discriminant performs classification of masses into benign or malignant better than the classification by any one of the individual parameters. The data set studied consisted of 99 cases (70 patients with benign masses and 29 patients with malignant masses). The areas under the receiver operating characteristic (ROC) curves (A/sub z/) and statistical attributes of the areas were studied to establish the enhancement in performance. The A/sub z/ value after combining all the parameters was found to be 0.8701. Upon combining this parameter with the level of suspicion (LOS) scores of a radiologist, the performance is further enhanced with an area under the (empirical) ROC of 0.94 having an operating point at a sensitivity of 0.965 and specificity of 0.87. It is suggested that this automated approach may hold promise as a means of classifying breast masses.
