Computer-aided detection of breast masses depicted on full-field digital mammograms: a performance assessment.

OBJECTIVES: To investigate the feasibility of converting a computer-aided detection (CAD) scheme for digitised screen-film mammograms to full-field digital mammograms (FFDMs) and assessing CAD performance on a large database. METHODS: The database included 6478 FFDM images acquired on 1120 females, with 525 cancer cases and 595 negative cases. The database was divided into five case groups: (1) cancer detected during screening, (2) interval cancers, (3) "high-risk" recommended for surgical excision, (4) recalled but negative and (5) negative (not recalled). A previously developed CAD scheme for masses depicted on digitised images was converted and re-optimised for FFDM images while keeping the same image-processing structure. CAD performance was analysed on the entire database. RESULTS: The case-based sensitivity was 75.6% (397/525) for the current mammograms and 40.8% (42/103) for the prior mammograms deemed negative during clinical interpretation but "visible" during retrospective review. The region-based sensitivity was 58.1% (618/1064) for the current mammograms and 28.4% (57/201) for the prior mammograms. The CAD scheme marked 55.7% (221/397) and 35.7% (15/42) of the masses on both views of the current and the prior examinations, respectively. The overall CAD-cued false-positive rate was 0.32 per image, ranging from 0.29 to 0.51 for the five case groups. CONCLUSION: This study indicated that (1) digitised image-based CAD can be converted for FFDMs while performing at a comparable, or better, level; (2) CAD detects a substantial fraction of cancers depicted on prior examinations, albeit most having been marked only on one view; and (3) CAD tends to mark more false-positive results on "difficult" negative cases that are more visually difficult for radiologists to interpret.

The ability of helical CT to preoperatively stage endometrial carcinoma.

OBJECTIVE: This study evaluated helical CT as an imaging modality for preoperative staging of endometrial carcinoma. MATERIALS AND METHODS: Three radiologists retrospectively and independently reviewed the preoperative helical CT scans of 25 consecutive patients with endometrial carcinoma. The presence or absence of deep myometrial invasion and the presence or absence of cervical involvement were evaluated on helical CT and compared with pathologic findings at hysterectomy. RESULTS: Helical CT has a sensitivity of 83% and a specificity of 42% for the detection of deep myometrial invasion (stage IC). Helical CT has a sensitivity of 25% and a specificity of 70% for the detection of cervical involvement (state II). These results compare poorly with those of MR imaging (sensitivity 92%, specificity 90% for the detection of deep myometrial invasion; sensitivity 86%, specificity 97% for the detection of cervical involvement). CONCLUSION: Helical CT is insensitive and nonspecific compared with MR imaging for the preoperative staging of endometrial carcinoma. MR imaging remains the imaging modality of choice.

Detection of masses and clustered microcalcifications on data compressed mammograms: an observer performance study.

OBJECTIVE: To evaluate observers' ability to detect breast masses and clustered microcalcifications depicted on data compressed mammograms, an observer performance study was performed. MATERIALS AND METHODS: Eight observers assessed 60 mammographic images obtained in six modes, ranging from noncompressed to a maximum data compression level of 101:1. Observers were asked to rate the images on a scale of 0 to 100 for the likelihood of the presence of a mass and also independently for the likelihood of the presence of clustered microcalcifications. In addition, observers were asked to rate their subjective assessment of the quality of each image for the detection of a mass and separately for the detection of microcalcifications. Receiver operating characteristic analyses were performed. RESULTS: The average area under the receiver operating characteristic curve, A(z), for the detection of clustered microcalcifications decreases significantly at the highest data compression level when compared with the noncompressed and two lowest levels of data compression (p < 0.01), and a trend test of the average area under the receiver operating characteristic curve for all observers is statistically significant (p < 0.05). No statistically significant differences among or between any of the data compression level modes for the detection of masses were detected. CONCLUSION: At a high level of mammogram data compression, observer performance was degraded for the detection of clustered microcalcifications. Detection of masses was not affected by the data compression methods and levels used in this study.

Applying computer-assisted detection schemes to digitized mammograms after JPEG data compression: an assessment.

RATIONALE AND OBJECTIVES: The authors' purpose was to assess the effects of Joint Photographic Experts Group (JPEG) image data compression on the performance of computer-assisted detection (CAD) schemes for the detection of masses and microcalcification clusters on digitized mammograms. MATERIALS AND METHODS: This study included 952 mammograms that were digitized and compressed with a JPEG-compatible image-compression scheme. A CAD scheme, previously developed in the authors' laboratory and optimized for noncompressed images, was applied to reconstructed images after compression at five levels. The performance was compared with that obtained with the original noncompressed digitized images. RESULTS: For mass detection, there were no significant differences in performance between noncompressed and compressed images for true-positive regions (P = .25) or false-positive regions (P = .40). In all six modes the scheme identified 80% of masses with less than one false-positive region per image. For the detection of microcalcification clusters, there was significant performance degradation (P < .001) at all compression levels. Detection sensitivity was reduced by 4%-10% as compression ratios increased from 17:1 to 62:1. At the same time, the false-positive detection rate was increased by 91%-140%. CONCLUSION: The JPEG algorithm did not adversely affect the performance of the CAD scheme for detecting masses, but it did significantly affect the detection of microcalcification clusters.

Use of preoperative MR imaging in the management of endometrial carcinoma: cost analysis.

PURPOSE: To compare the cost of magnetic resonance (MR) imaging and its ability to direct the use of lymph node dissection with the cost and ability of conventional surgery for the staging of endometrial carcinoma. MATERIALS AND METHODS: Preoperative MR images of 25 patients who underwent hysterectomy for endometrial carcinoma were retrospectively evaluated. MR imaging results were compared with those of intraoperative gross dissection of the uterus and final histopathologic examination. Medicare reimbursements for two scenarios were compared in each patient. In the MR imaging scenario, the necessity for lymph node dissection was based on MR imaging results and histologic findings at biopsy. In the actual scenario, lymph node dissection was performed at the surgeon's discretion on the basis of findings at gross dissection of the uterus and histologic examination at biopsy. RESULTS: The cost of the MR imaging scenario, as defined by Medicare reimbursements, was 1% ($1, 265/$148,500) less than that of the actual scenario. In the MR imaging scenario, all patients who required lymph node dissection received it, and 86% of the lymph node dissections performed were necessary. In the actual scenario, one necessary lymph node dissection was not performed, and only 31% of the lymph node dissections performed were necessary. CONCLUSION: Staging with MR imaging has costs and accuracy similar to those of the current method of staging with intraoperative gross dissection of the uterus. In addition, MR imaging decreases the number of unnecessary lymph node dissections.

Effects of luminance and resolution on observer performance with chest radiographs.

PURPOSE: To examine the combined effects of image resolution and display luminance on observer performance for detection of abnormalities depicted on posteroanterior chest radiographs. MATERIALS AND METHODS: A total of 529 radiographs were displayed on a specially constructed view box at three luminance levels (770, 260, and 85 cd/m(2)) and three resolutions (100-microm, 200-microm, and 400-microm pixels). Each image was reviewed nine times by six radiologists who participated in this study. The abnormalities included nodule, pneumothorax, interstitial disease, alveolar infiltrates, and rib fracture. Negative (normal) radiographs were also included. RESULTS: Receiver operating characteristic curves indicated that the effect of image luminance was greater than that of resolution. The detection of pneumothorax, interstitial disease, and rib fracture showed statistically significant differences (P <. 05) due to luminance. The detection of pneumothorax was the only abnormality with a statistically significant difference due to resolution. There was no evidence that luminance was related to image resolution for any of the abnormalities. CONCLUSION: At a resolution of 400-microm pixels or higher across the field of view and a luminance of 260 cd/m(2) or more, primary diagnosis with posteroanterior chest radiographs is not likely to be affected by the quality of display.

Computerized localization of breast lesions from two views. An experimental comparison of two methods.

RATIONALE AND OBJECTIVES: The authors compared two computerized methods, the arc and cartesian straight-line, for the localization of breast lesions in two mammographic views. METHODS: A total of 571 craniocaudal and 571 mediolateral oblique matched mammographic image pairs (or 1142 individual images) depicting 290 pathology-verified masses on both views were selected from our image database. Using a previously developed computer-aided detection scheme, all 290 masses and 3992 suspicious but negative regions were identified. After pairing all identified regions from both views, all masses (true-positive-true-positive matched pairs) and a total of 10330 false-positive pairs (including false-positive-false-positive, true-positive-false-positive, and false-positive-true positive pairs) were assessed as to their position in relation to the nipple using both the arc and the cartesian straight-line methods. Receiver operating characteristic methodology was used to evaluate the performance levels for each method in determining, based solely on location, whether a pair of suspicious regions represented a true mass or a false-positive combination. RESULTS: The areas under the receiver operating characteristic curves (Az) were 0.79 and 0.78 for the arc and cartesian straight-line methods, respectively. The difference between the two techniques (as measured by Az) was not statistically significant (P > 0.99). CONCLUSIONS: These preliminary results demonstrated that the two methods are comparable in identifying true masses from triangulated observations on two views. However, the arc method is somewhat favorable because only the nipple location is required for localization.

Observer sensitivity to small differences: a multipoint rank-order experiment.

OBJECTIVE: To evaluate observer sensitivity to small differences in image presentation, a multipoint rank-order experiment was used to identify small differences or trends in observations. MATERIALS AND METHODS: Ten observers were presented with 50 sets of breast images that had been compressed at five different levels. Each set contained six images ranging from noncompressed to approximately 101:1 compression. Observers were asked to review all images of a case side by side and rank order the quality of each to enable determination of the presence or absence of masses and clustered microcalcifications. RESULTS: As a group, observers were able to detect small differences among the images, even at the lower compression levels (p < .001). As compression levels and image degradation increased, the ability to identify differences between different modes also increased. Large observer variability in discrimination ability was observed. CONCLUSION: Multipoint rank ordering of images viewed side by side can be an efficient method to identify small differences in image presentation. This approach to image ranking could be used to rule out or confirm the need for objective observer performance-type studies.

Computed radiography versus screen-film mammography in detection of simulated microcalcifications: a receiver operating characteristic study based on phantom images.

RATIONALE AND OBJECTIVES: The authors compare a 43-micron computed radiographic system with a mammographic screen-film system for detection of simulated microcalcifications in an observer-performance study. MATERIALS AND METHODS: The task of detecting microcalcifications was simulated by imaging aluminum wire segments (200-500 microns in length; 100, 125, or 150 microns in diameter) that overlapped with tissue background structures produced by beef brisket. A total of 288 such simulations were generated and examined with both computed radiography and conventional screen-film mammography techniques. Computed radiography was performed with high-resolution plates, a 43-micron image reader, and a 43-micron laser film printer. Computed radiographic images were printed with simple contrast enhancement and compared with screen-film images in a receiver operating characteristic study in which experienced readers detected and scored the simulated microcalcifications. Observer performance was quantitated and compared by computing the area under the receiver operating characteristic curve. RESULTS: Although the resolution of the computed radiography system was better than that of commercial systems, it fell short of that of screen-film systems. For the 100-micron microcalcifications, the difference in the average area under the curve was not statistically significant, but it was significant for the larger simulated microcalcifications: the average area under the curve was 0.58 for computed radiography versus 0.76 for screen-film imaging for the 125-micron microcalcifications and 0.83 versus 1.00, respectively, for the 150-micron microcalcifications. CONCLUSION: Observer performance in the detection of small simulated microcalcifications (100-150 microns in diameter) is better with screen-film images than with high-resolution computed radiographic images.

Lactating adenoma: US features and literature review.

PURPOSE: To describe the ultrasonographic (US) features of adenoma in a lactating breast. MATERIALS AND METHODS: The US scans of 11 lactating adenomas in nine patients aged 25-36 years examined in 1991-1996 were retrospectively reviewed. In all lesions, diagnoses were cytologically or histologically proved after US-guided fine-needle aspiration biopsy (eight lesions) or core biopsy (three lesions). Six patients were lactating, and three patients were in the third trimester of pregnancy. The US features analyzed were shape, orientation to the chest wall, border characteristics, echogenicity, homogeneity, enhancement or shadowing, and depth within the breast. RESULTS: Most lesions had benign US features such as ovoid shape with the long axis parallel to the chest wall (10 of 11), well-defined margins (eight of 11), homogeneous echotexture (eight of 11), and posterior acoustic enhancement (10 of 11). Four lesions had US features that resembled malignant lesions, such as irregular margins, heterogeneous echotexture, and posterior acoustic shadowing. CONCLUSION: The US features, although generally benign, are not specific. Tissue sampling with fine-needle aspiration biopsy is recommended. Core biopsy is necessary if a diagnosis cannot be made with the aspirate but is not performed initially because of the possibility of milk fistula formation.

Preliminary clinical evaluation of a high-resolution telemammography system.

RATIONALE AND OBJECTIVES: The authors designed, assembled, tested, and clinically evaluated a high-quality, fast, and relatively inexpensive telemammography system. METHODS: The authors designed a telemammography system that uses a high-resolution film digitizer and high data compression (> or = 40:1) to send images over regular telephone lines to a high-resolution laser printer that produces images with the look and feel of the original image and can operate in a hub and spokes mode. The authors then evaluated the system's performance. In a preliminary clinical study, interpretations of the laser-printed system's output of 119 cases were compared with the original interpretations, followed by a review of any clinically significant differences. RESULTS: With the exception of the laser printer, which is a modified off-the-shelf product, all hardware components of the system are commercially available products. The system digitizes (50 microns pixel size), compresses, transmits, receives, decompresses, and prints a 30 MB mammography file in less than 4 minutes. In the clinical study, there were 13 differences (in 13 cases) in the level of concern or recommendations. Seven were found to be clinically insignificant by a third-party review. The remaining six were reviewed by the original interpreter, and three were determined to be significant enough for further action. All were found to result from intra-reader variability rather than differences in visualization of possible abnormalities. CONCLUSIONS: Almost real-time, high-quality telemammography without geographic boundaries is possible with the use of high-level data compression. Telemammography with laser-printed film as the display may make it possible to offer mammographic services in remote locations while using commercially available technology.

Automated large-core needle biopsy of surgically removed breast lesions: comparison of samples obtained with 14-, 16-, and 18-gauge needles.

PURPOSE: To determine the needle size that would consistently enable the pathologist to correctly diagnose tissue core biopsy specimens. MATERIALS AND METHODS: Fifty-seven surgically removed mass lesions of the breast were sampled with a short-throw automated biopsy gun and an 18-gauge needle first, followed by a 16- and a 14-gauge needle. Samples were evaluated independently by three pathologists, and findings were compared with the final diagnosis made at surgical excision biopsy. RESULTS: The sensitivity for the diagnosis of all 26 malignant lesions was 100%, 92%, and 65% for biopsy samples obtained with 14-, 16-, and 18-gauge needles, respectively. Specificity for malignancy was 100% for all three needle sizes. All of the benign diseases were correctly diagnosed in samples obtained with all three size needles except for two samples that did not survive processing. CONCLUSION: Biopsy samples obtained with a 14-gauge needle provide the most accurate diagnosis, which correlates with the diagnosis made with the surgical excision biopsy technique.

Diagnostic reading session: temporal patterns and case-order effects.

The authors analyzed receiver-operating-characteristic studies to determine temporal patterns and performance as a function of the elapsed time in a reading session. Nineteen radiologists each read as many as 300 chest images with use of seven different display modalities, including conventional and laser-printed film and high-resolution soft display. With a computerized reporting system, the ratio of observers' interpretation rates (time to diagnosis) were recorded for the last five and 10 compared with the first five and 10 of 30-40 cases seen in sessions lasting 45-110 minutes. Observers tended to accelerate their interpretation as the sessions progressed by an average of 15% (P < .001). The acceleration was consistent for all readers (both fast and slow) with a variety of display modes under the nonrestricted time environment.

Contemporary radiologic percutaneous abscess drainage in the pelvis.

In summary, PAD of pelvic abscesses is an established radiologic procedure. The procedure has gained wide acceptance as an adjunct in the management of patients with pelvic abscess. The procedure involves minimal trauma, is well tolerated, and produces early relief of symptoms. In many instances, it may shorten the length of the hospital stay, reduce costs, and often eliminate the need for surgical intervention. In selected patients, PAD may serve as a temporizing measure in a critically ill or endstage patient. Initial results of PAD treatment of TOA are encouraging, suggesting that this procedure, just as elsewhere in the abdomen, is safe and effective, but larger series are required and long-term follow-up is necessary for evaluation of the cure rate, rate of recurrence, and possible complications.

US-guided venipuncture for venography in the edematous leg.

A technique for sonographic-guided venipuncture was developed especially for venography made difficult by gross leg edema. Five patients were evaluated in whom venography had been attempted but was initially unsuccessful because of difficult venous access. All five underwent successful venipuncture after sonographic localization of a vein. Ultrasound-guided venipuncture is simple and useful when venous access by palpation is difficult.

CT appearance of the Roux limb following choledochojejunostomy in liver transplantation.

Choledochojejunostomy in Roux-en-Y is a frequent form of biliary reconstruction in liver transplants. On computed tomography (CT), fluid in the Roux limb may simulate a fluid collection. We studied the CT appearance of the Roux jejunal limb in 25 normal and complicated liver transplant patients. The Roux limb was identified in 21 (84%) of 25 cases. Most frequently useful features were characteristic location, continuous tubular appearance, biliary stent, "bull's eye" appearance, and gas in the loop. Two of 18 normal Roux loops were initially suspected of being abscesses and one gas-containing abscess was initially mistaken for the Roux limb. In five of seven patients with complications (four abscesses, two bile leaks, one anastomotic hemorrhage), identification of the Roux limb was possible and was useful in interpreting CT scans. Knowledge of the appearance of the normal and abnormal Roux limb is essential for proper interpretation of CT scans in liver transplant patients.

The effect of clinical history on chest radiograph interpretations in a PACS environment.

The effect that accompanying patient information has on diagnostic accuracy in radiologic interpretation has been studied by many researchers but remains a matter of contention. Experiments in the past emphasized the chest film because this procedure is the one done most frequently in radiology. However, with the increasing importance of digital imaging, the role of patient history in these procedures should be assessed. The use of a model computerized patient history in the interpretation of digitized chest images that were displayed on a high-resolution workstation was studied. Two hundred forty-seven selected posteroanterior chest images that indicated disease and that indicated no disease were interpreted in random sequence by five board-certified radiologists, with and without accompanying patient histories. Readers were prompted by the response forms to evaluate images for the possible occurrence of interstitial diseases, nodules, or pneumothorax. No significant differences (P = .05) in the detection of these abnormalities were noted between case readings with and without history for any of the radiologists or for the group as a whole. However, this methodology reflects a direct interpretation approach. The results of this study may not necessarily be applicable to individual prompts, different imaging procedures, or other abnormalities.

Liver transplant rejection: value of the resistive index in Doppler US of hepatic arteries.

The authors prospectively evaluated the accuracy of the resistive index (RI) in Doppler ultrasound (US) for the detection of the increased vascular resistance that theoretically occurs with acute liver transplant rejection. RIs were calculated for the proximal hepatic artery and a more distal hepatic artery branch in 67 liver transplant recipients. Biopsies were performed within 24 hours of transplantation, with no intervening therapy. Examination of biopsy specimens by a single pathologist revealed findings of no, minimal, or moderate to severe rejection. RIs in hepatic arteries showed no significant differences among the three pathologic groups. No correlation was found between the RI and improved or worsened rejection in 11 patients who underwent biopsy and US more than once. RIs in hepatic arteries are of no value in the prediction of liver transplant rejection.

Periportal low-attenuation areas on CT: value as evidence of liver transplant rejection.

CT scans of liver transplants may show periportal areas that are lower in attenuation than adjacent portal veins and liver. These areas appear as low-density rims that surround or parallel the portal vein and its intrahepatic branches as well as the immediate subhepatic portal area. In order to determine the value of periportal low attenuation as an indicator of rejection, we reviewed the CT scans of 37 liver transplant patients with biopsy evidence of either acute rejection (12 patients) or nonspecific change without rejection (25 patients). Low-attenuation areas around peripheral portal branches were identified in six of 12 patients with rejection and in four of 25 patients with nonspecific change (sensitivity, 50%; specificity, 84%; accuracy, 73%). The correlation between peripheral periportal low attenuation and rejection was statistically significant (p less than .05). Periportal low attenuation in a central location was seen in eight of 12 patients with acute rejection and in 14 of 25 patients with nonspecific change (sensitivity, 67%; specificity, 44%; accuracy, 51%). The correlation was not statistically significant. Low-attenuation areas were evident on scans obtained either with or without IV contrast enhancement. Periportal low-attenuation areas are commonly seen on CT scans of liver transplants. Peripheral areas correlate with acute rejection, but other factors probably contribute to their occurrence. Central areas do not correlate with acute rejection. Low sensitivity and relatively low accuracy limit the usefulness of peripheral periportal low attenuation as a sign of acute liver allograft rejection.