Digital mammography: observer performance study of the effects of pixel size on the characterization of malignant and benign microcalcifications.

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate the effects of pixel size on the characterization of mammographic microcalcifications by radiologists. MATERIALS AND METHODS: Two-view mammograms of 112 microcalcification clusters were digitized with a laser scanner at a pixel size of 35 microm. Images with pixel sizes of 70, 105, and 140 microm were derived from the 35-microm-pixel size images by averaging neighboring pixels. The malignancy or benignity of the microcalcifications had been determined with findings at biopsy or 2-year follow-up. Region-of-interest images containing the microcalcifications were printed with a laser imager. Seven radiologists participated in a receiver operating characteristic (ROC) study to estimate the likelihood of malignancy. The classification accuracy was quantified with the area under the ROC curve (Az). The statistical significance of the differences in the Az values for different pixel sizes was estimated with the Dorfman-Berbaum-Metz method and the Student paired t test. The variance components were analyzed with a bootstrap method. RESULTS: The higher-resolution images did not result in better classification; the average Az with a pixel size of 35 microm was lower than that with pixel sizes of 70 and 105 microm. The differences in Az between different pixel sizes did not achieve statistical significance. CONCLUSION: Pixel sizes in the range studied do not have a strong effect on radiologists' accuracy in the characterization of microcalcifications. The low specificity of the image features of microcalcifications and the large interobserver and intraobserver variabilities may have prevented small advantages in image resolution from being observed.

Computer-aided characterization of mammographic masses: accuracy of mass segmentation and its effects on characterization.

Mass segmentation is used as the first step in many computer-aided diagnosis (CAD) systems for classification of breast masses as malignant or benign. The goal of this paper was to study the accuracy of an automated mass segmentation method developed in our laboratory, and to investigate the effect of the segmentation stage on the overall classification accuracy. The automated segmentation method was quantitatively compared with manual segmentation by two expert radiologists (R1 and R2) using three similarity or distance measures on a data set of 100 masses. The area overlap measures between R1 and R2, the computer and R1, and the computer and R2 were 0.76 +/- 0.13, 0.74 +/- 0.11, and 0.74 +/- 0.13, respectively. The interobserver difference in these measures between the two radiologists was compared with the corresponding differences between the computer and the radiologists. Using three similarity measures and data from two radiologists, a total of six statistical tests were performed. The difference between the computer and the radiologist segmentation was significantly larger than the interobserver variability in only one test. Two sets of texture, morphological, and spiculation features, one based on the computer segmentation, and the other based on radiologist segmentation, were extracted from a data set of 249 films from 102 patients. A classifier based on stepwise feature selection and linear discriminant analysis was trained and tested using the two feature sets. The leave-one-case-out method was used for data sampling. For case-based classification, the area Az under the receiver operating characteristic (ROC) curve was 0.89 and 0.88 for the feature sets based on the radiologist segmentation and computer segmentation, respectively. The difference between the two ROC curves was not statistically significant.

Improvement of radiologists' characterization of mammographic masses by using computer-aided diagnosis: an ROC study.

PURPOSE: To evaluate the effects of computer-aided diagnosis (CAD) on radiologists' classification of malignant and benign masses seen on mammograms. MATERIALS AND METHODS: The authors previously developed an automated computer program for estimation of the relative malignancy rating of masses. In the present study, the authors conducted observer performance experiments with receiver operating characteristic (ROC) methodology to evaluate the effects of computer estimates on radiologists' confidence ratings. Six radiologists assessed biopsy-proved masses with and without CAD. Two experiments, one with a single view and the other with two views, were conducted. The classification accuracy was quantified by using the area under the ROC curve, Az. RESULTS: For the reading of 238 images, the Az value for the computer classifier was 0.92. The radiologists' Az values ranged from 0.79 to 0.92 without CAD and improved to 0.87-0.96 with CAD. For the reading of a subset of 76 paired views, the radiologists' Az values ranged from 0.88 to 0.95 without CAD and improved to 0.93-0.97 with CAD. Improvements in the reading of the two sets of images were statistically significant (P = .022 and .007, respectively). An improved positive predictive value as a function of the false-negative fraction was predicted from the improved ROC curves. CONCLUSION: CAD may be useful for assisting radiologists in classification of masses and thereby potentially help reduce unnecessary biopsies.

Women with breast cancer: histologic findings in the contralateral breast.

PURPOSE: To investigate contralateral breast biopsy histologic findings in women with breast cancer. MATERIALS AND METHODS: Histologic findings in 237 patients with breast cancer who underwent contralateral breast biopsy for clinically or mammographically detected abnormalities were retrospectively reviewed. Malignant findings were categorized by histologic type. Benign findings were categorized by risk of breast cancer. Comparison was made with mammographically guided breast biopsy results in 1,294 patients without breast cancer. RESULTS: Of the 237 patients, 168 (70.9%) had either malignancy or high-risk histologic findings. One hundred thirty-nine patients (58.6%) had malignant findings; 98 (41.4%) had benign findings. Of the 98 with benign findings, 29 (30%) had high-risk histologic findings. Thirty (33%) of the 91 patients with invasive cancer had invasive lobular carcinoma. Forty-seven (45.6%) of the 103 patients with malignant lesions at mammographically guided biopsies had ductal carcinoma in situ alone. CONCLUSION: Compared with biopsy in women without breast cancer, contralateral biopsy in women with breast cancer was more likely to show malignancy, invasive lobular carcinoma, or ductal carcinoma in situ alone (P < .001) or to show high-risk histologic benign findings (P < .001). Mammographic and clinical findings in the contralateral breast should be regarded as more suspicious than those in patients without known breast cancer.

Mammographic appearance of cancer in the opposite breast: comparison with the first cancer.

OBJECTIVE: Patients who have had cancer in one breast are at high risk for cancer in the contralateral breast. These bilateral cancers may be synchronous or metachronous. If the manifestations on mammography were similar in both breasts, an aggressive search for the mammographic findings of the first breast cancer might lead to early detection of the contralateral cancer. The purpose of this study was to evaluate mammograms for patients with bilateral cancers to determine whether the mammographic appearance of the contralateral cancer is likely to be the same as that of the first cancer. MATERIALS AND METHODS: We retrospectively reviewed the pathologic and mammographic records of 69 patients with surgically proven bilateral primary breast cancer. Thirty four of 69 (49%) had synchronous cancer, and 35 (51%) had metachronous cancer. Mammographic appearances were classified as microcalcifications, spiculated mass, nonspiculated mass (whether circumscribed or poorly defined), asymmetric or developing density, architectural distortion, and normal. Multiple findings were subclassified as major and minor findings. All findings were compared between both breast cancers, and statistical significance was determined by the two-sample Z test. RESULTS: Forty six (67%) of 69 patients had different major mammographic findings in the contralateral cancer. Of 30 patients whose first cancers had microcalcifications, 20 (67%) had microcalcifications in the contralateral cancer. Of 39 patients whose first cancers lacked microcalcifications, 17 (44%) had microcalcifications in the contralateral cancer. This difference was statistically significant (p = .02). Of 26 patients whose first cancers had spiculated masses, 9 (35%) had a contralateral spiculated mass. Of 43 patients whose first cancers lacked spiculated masses, 12 (28%) had a contralateral spiculated mass. This difference was not statistically significant (p = .22). CONCLUSION: Our results show that contralateral tumors usually have major mammographic findings different from those of the first cancer, and the mammographic signs of the first cancer do not indicate the most likely appearance of cancer in the contralateral breast. Evaluation of a contralateral mammogram should be performed without regard for the mammographic findings for the first cancer.

Bilateral breast cancer: early detection with mammography.

PURPOSE: To assess the contribution of mammography in the detection of cancer in the contralateral breast in women with bilateral breast cancer. MATERIALS AND METHODS: Mammograms and clinical records of 77 patients with bilateral breast cancer were reviewed in a retrospective study. RESULTS: The contralateral cancer was detected at mammography in 68 of 77 patients (88%) and identified at mammography alone in 50 patients (65%). No statistically significant differences in either mammographic detection rates or stage of the contralateral cancer were noted in patients younger than 50 years (n = 25) compared with those 50 years of age or older (n = 52). Cancers detected at annual screening mammography were of lower stage than cancers in unscreened patients. In the screened group, 41% of tumors were ductal carcinoma in situ alone and 23% were stage II or III, compared with 22% and 50%, respectively, in the unscreened group. CONCLUSION: Mammographic examination and follow-up in patients with unilateral breast cancer allow detection of the majority of contralateral breast cancers and earlier stage cancers.

Invasive lobular carcinoma: sonographic appearance and role of sonography in improving diagnostic sensitivity.

PURPOSE: To characterize the ultrasonographic (US) appearance of invasive lobular carcinoma (ILC) and to assess the potential role of US in the earlier detection of ILC. MATERIALS AND METHODS: US scans in 19 patients with ILC were retrospectively studied for the presence of a mass, characteristics of the margins, internal echogenicity, and attenuation effects. RESULTS: US showed masses in 13 of the 19 patients (68% sensitivity). Irregularly marginated masses with heterogeneous internal echoes and acoustic attenuation were present in seven patients. A variety of US findings, mimicking a benign lesion, were noted in the other six patients. US sensitivity in the detection of small cancers (< 1 cm) was 25% (one of four patients). Mammographic sensitivity in the detection of ILC in this series was 89% (17 of 19 patients). CONCLUSION: ILC has a variety of US appearances. US was insensitive and nonspecific in the diagnosis of ILC, especially for small cancers. A negative US result should not deter surgical biopsy if indicated by mammographic findings or clinical findings.

Invasive lobular carcinoma. Imaging features and clinical detection.

RATIONALE AND OBJECTIVES: Mammographic findings and method of detection of 52 cases of invasive lobular carcinoma (ILC), the second most common breast carcinoma, are reported. METHODS: Preoperative mammograms and clinical records of all patients with ILC not associated with a second mammary carcinoma (other than lobular carcinoma in situ) from 1979-1991 at the authors' institution were retrospectively reviewed. RESULTS: Abnormal mammographic findings were present in 48/52 (92%) and included irregular spiculated masses (33/52, 63%), asymmetric densities (7/52, 13%), architectural distortion (5/52, 10%), microcalcifications (2/52, 4%), and well circumscribed masses (1/52, 2%). The mean mammographic diameter was 2.1 cm. The tumor was most often best visualized in the craniocaudal projection. At the time of diagnosis, 54% of women had coexistent suggestive breast physical findings and 35% had metastatic carcinoma in axillary lymph nodes. CONCLUSIONS: The infrequency of microcalcifications in pure ILC may hinder mammographic detection and contrasts markedly with ductal carcinoma. Mammography and breast physical examination play complementary roles in the detection of ILC.

An in vitro comparison of computed tomography, xeroradiography, and radiography in the detection of soft-tissue foreign bodies.

Computed tomography (CT), xeroradiography, and radiography were compared in vitro to assess the relative value of each in detecting soft-tissue foreign bodies. Results indicate that CT may prove useful.