Evaluation of computer-aided detection of lesions in mammograms obtained with a digital phase-contrast mammography system

A computer-aided detection (CAD) system was evaluated for its ability to detect microcalcifications and masses on images obtained with a digital phase-contrast mammography (PCM) system, a system characterised by the sharp images provided by phase contrast and by the high resolution of 25-μm-pixel mammograms. Fifty abnormal and 50 normal mammograms were collected from about 3,500 mammograms and printed on film for reading on a light box. Seven qualified radiologists participated in an observer study based on receiver operating characteristic (ROC) analysis. The average of the areas under ROC curve (AUC) values for the ROC analysis with and without CAD were 0.927 and 0.897 respectively (P?=?0.015). The AUC values improved from 0.840 to 0.888 for microcalcifications (P?=?0.034) and from 0.947 to 0.962 for masses (P?=?0.025) respectively. The application of CAD to the PCM system is a promising approach for the detection of breast cancer in its early stages.     

Effect of soft-copy display supported by CAD on mammography screening performance

Diagnostic performance and reading speed for conventional mammography film reading is compared to reading digitized mammograms on a dedicated workstation. A series of mammograms judged negative at screening and corresponding priors were collected. Half were diagnosed as cancer at the next screening, or earlier for interval cancers. The others were normal. Original films were read by fifteen experienced screening radiologists. The readers annotated potential abnormalities and estimated their likelihood of malignancy. More than 1 year later, five radiologists reread a subset of 271 cases (88 cancer cases having visible signs in retrospect and 183 normals) on a mammography workstation after film digitization. Markers from a computer-aided detection (CAD) system for microcalcifications were available to the readers. Performance was evaluated by comparison of A_z-scores based on ROC and multiple-Reader multiple-case (MRMC) analysis, and localized receiver operating characteristic (LROC) analysis for the 271 cases. Reading speed was also determined. No significant difference in diagnostic performance was observed between conventional and soft-copy reading. Average A_z-scores were 0.83 and 0.84 respectively. Soft-copy reading was only slightly slower than conventional reading. Using a mammography workstation including CAD for detection of microcalcifications, soft-copy reading is possible without loss of quality or efficiency.     

Detection of masses and calcifications by soft-copy reading: comparison of two postprocessing algorithms for full-field digital mammography

Purpose  The purpose of this study was to determine the effects of a commercially available postprocessing algorithm on the detection of masses and microcalcifications of breast cancer by soft-copy reading. Materials and methods  The study included 64 digital mammograms with 16 histologically proven abnormal findings (eight masses and eight microcalcifications) and 48 normal breasts. Two image-processing algorithms were applied to the digital images, which were acquired using General Electric units. The commercially available advanced and standard postprocessed digital mammograms were evaluated in a localization receiver operating characteristic (ROC) curve experiment involving seven mammography radiographers. Results  The mean area under the ROC curve was 0.921 ± 0.022 for the commercially available advanced postprocessed digital mammograms session and 0.904 ± 0.026 for the standard postprocessed digital mammograms session (P = 0.1953). Observer agreement among the readers was better for the advanced postprocessed digital mammograms than for the standard postprocessed digital mammograms. Conclusion  During soft-copy reading, the interpretation accuracy might be influenced by the postprocessing algorithm.     

Radiologist detection of microcalcifications with and without computer-aided detection: a comparative study

AIM: To compare the sensitivity and specificity of microcalcification detection by radiologists alone and assisted by a computer-aided detection (CAD) system. MATERIALS AND METHODS: Films of 106 patients were masked, randomized, digitized and analysed by the CAD-system. Five readers interpreted the original mammograms and were blinded to demographics, medical history and earlier films. Forty-two mammograms with malignant microcalcifications, 40 with benign microcalcifications and 24 normal mammograms were included. Results were recorded on a standardized image interpretation form. The mammograms with suspicious areas flagged by the CAD-system were displayed on mini-monitors and immediately re-reviewed. The interpretation was again recorded on a new copy of the standard form and classified according to six groups. RESULTS: Forty-one out of 42 (98%) malignant microcalcifications and 32 of 40 (80%) benign microcalcifications were flagged by the CAD-system. There was an average of 1.2 markers per image. The sensitivity for malignant microcalcifications detection by mammographers without and with the CAD-system ranged from 81% to 98% and from 88% to 98%, respectively. The mean difference without and with CAD-system was 2.2% (range 0-7%). CONCLUSION: No statistically significant changes in sensitivity were found when experienced mammographers were assisted by the CAD-system, with no significant compromise in specificity.     

Diagnostic accuracy of digital mammography in patients with dense breasts who underwent problem-solving mammography: effects of image processing and lesion type

PURPOSE: To determine effects of lesion type (calcification vs mass) and image processing on radiologist's performance for area under the receiver operating characteristic curve (AUC), sensitivity, and specificity for detection of masses and calcifications with digital mammography in women with mammographically dense breasts. MATERIALS AND METHODS: This study included 201 women who underwent digital mammography at seven U.S. and Canadian medical centers. Three image-processing algorithms were applied to the digital images, which were acquired with Fischer, General Electric, and Lorad digital mammography units. Eighteen readers participated in the reader study (six readers per algorithm). Baseline values for reader performance with screen-film mammograms were obtained through the additional interpretation of 179 screen-film mammograms. A repeated-measures analysis of covariance allowing unequal slopes was used in each of the nine analyses (AUC, sensitivity, and specificity for each of three machines). Bonferroni correction was used. RESULTS: Although lesion type did not affect the AUC or sensitivity for Fischer digital images, it did affect specificity (P =.0004). For the General Electric digital images, AUC, sensitivity, and specificity were not affected by lesion type. For Lorad digital images, the results strongly suggested that lesion type affected AUC and sensitivity (P <.0001). None of the three image-processing methods tested affected the AUC, sensitivity, or specificity for the Fischer, General Electric, or Lorad digital images. CONCLUSION: Findings in this study indicate that radiologist's interpretation accuracy in interpreting digital mammograms depends on lesion type. Interpretation accuracy was not influenced by the image-processing method.     

Observer variability in screen-film mammography versus full-field digital mammography with soft-copy reading

Full-field digital mammography (FFDM) with soft-copy reading is more complex than screen-film mammography (SFM) with hard-copy reading. The aim of this study was to compare inter- and intraobserver variability in SFM versus FFDM of paired mammograms from a breast cancer screening program. Six radiologists interpreted mammograms of 232 cases obtained with both techniques, including 46 cancers, 88 benign lesions, and 98 normals. Image interpretation included BI-RADS categories. A case consisted of standard two-view mammograms of one breast. Images were scored in two sessions separated by 5 weeks. Observer variability was substantial for SFM as well as for FFDM, but overall there was no significant difference between the observer variability at SFM and FFDM. Mean kappa values were lower, indicating less agreement, for microcalcifications compared with masses. The lower observer agreement for microcalcifications, and especially the low intraobserver concordance between the two imaging techniques for three readers, was noticeable. The level of observer agreement might be an indicator of radiologist performance and could confound studies designed to separate diagnostic differences between the two imaging techniques. The results of our study confirm the need for proper training for radiologists starting FFDM with soft-copy reading in breast cancer screening. Presented at ECR, Wien 2006.     

Digital mammography. ROC studies of the effects of pixel size and unsharp-mask filtering on the detection of subtle microcalcifications

We investigated the spatial resolution requirement and the effect of unsharp-mask filtering on the detectability of subtle microcalcifications in digital mammography. Digital images were obtained by digitizing conventional screen-film mammograms with a 0.1 X 0.1 mm2 pixel size, processed with unsharp masking, and then reconstituted on film with a Fuji image processing/simulation system (Fuji Photo Film Co., Tokyo, Japan). Twenty normal cases and 12 cases with subtle microcalcifications were included. Observer performance experiments were conducted to assess the detectability of subtle microcalcifications in the conventional, the unprocessed digital, and the unsharp-masked mammograms. The observer response data were evaluated using receiver operating characteristic (ROC) and LROC (ROC with localization) analyses. Our results indicate that digital mammograms obtained with 0.1 X 0.1 mm2 pixels provide lower detectability than the conventional screen-film mammograms. The detectability of microcalcifications in the digital mammograms is improved by unsharp-mask filtering; the processed mammograms still provide lower accuracy than the conventional mammograms, however, chiefly because of increased false-positive detection rates for the processed images at each subjective confidence level. Viewing unprocessed digital and unsharp-masked images in pairs resulted in approximately the same detectability as that obtained with the unsharp-masked images alone. However, this result may be influenced by the fact that the same limited viewing time was necessarily divided between the two images.     

Breast lesion detection and classification: comparison of screen-film mammography and full-field digital mammography with soft-copy reading--observer performance study

PURPOSE: To retrospectively compare screen-film and full-field digital mammography with soft-copy interpretation for reader performance in detection and classification of breast lesions in women in a screening program. MATERIALS AND METHODS: Regional ethics committee approved the study; signed patient consents were obtained. Two-view mammograms were obtained with digital and screen-film systems at previous screening studies. Six readers interpreted images. Interpretation included Breast Imaging Reporting and Data System (BI-RADS) and five-level probability-of-malignancy scores. A case was one breast, with two standard views acquired with both screen-film mammography and digital mammography. The standard for an examination with normal findings was classification of normal (category 1) assigned by two independent readers; for cases with benign findings, the standard was benign results at diagnostic work-up in patients who were recalled. Cases with normal or benign findings that manifested as neither interval cancer nor as cancer at subsequent screening were considered the standard. All cancers were confirmed histologically. Images were interpreted by readers in two sessions 5 weeks apart; the same case was not seen twice in any session. Receiver operating characteristic (ROC) analysis and, for a given true-positive fraction, 2 x 2 table analysis and the McNemar test were used. For binary outcome, classification of BI-RADS category 3 or higher was defined as positive for cancer. RESULTS: Cases with proved findings (n = 232) were displayed: 46 with cancers, 88 with benign findings, and 98 with normal findings. ROC analysis for all readers and all cases revealed a higher area under ROC curve (A(z)) for digital mammography (0.916) than for screen-film mammography (0.887) (P = .22). Five of six readers had a higher performance rating with digital mammography; one of five demonstrated a significant difference in favor of digital mammography with A(z) values; two showed a significant difference in favor of digital mammography with ROC analysis for a given false-positive fraction (P = .01 and .03, respectively). For cases with cancer, digital mammography resulted in correct classification of an average of three additional cancers per reader. For digital versus screen-film mammography, 2 x 2 table analysis for cancers revealed a higher true-positive rate; for benign masses, a higher true-negative rate. Neither of these differences nor any others from analysis of subgroups between the modalities were significant. CONCLUSION: Digital mammography allowed correct classification of more breast cancers than did screen-film mammography. A(z) value was higher for digital mammography; this difference was not significant.     

Diagnostic value of the stand-alone synthetic image in digital breast tomosynthesis examinations

Objective

To demonstrate the non-inferiority of synthetic image (SI) mammography versus full-field digital mammography (FFDM) in breast tomosynthesis (DBT) examinations.

Methods

An observational, retrospective, single-centre, multireader blinded study was performed, using 2384 images to directly compare SI and FFDM based on Breast Imaging Reporting and Data System (BIRADS) categorisation and visibility of radiological findings. Readers had no access to digital breast tomosynthesis slices. Multiple reader, multiple case (MRMC) receiver operating characteristic (ROC) methodology was used to compare the diagnostic performance of SI and FFDM images. The kappa statistic was used to estimate the inter-reader and intra-reader reliability.

Results

The area under the ROC curves (AUC) reveals the non-inferiority of SI versus FFDM based on BIRADS categorisation [difference between AUC (ΔAUC), -0.014] and lesion visibility (ΔAUC, -0.001) but the differences were not statistically significant (p=0.282 for BIRADS; p=0.961 for lesion visibility). On average, 77.4% of malignant lesions were detected with SI versus 76.5% with FFDM. Sensitivity and specificity of SI are superior to FFDM for malignant lesions scored as BIRADS 5 and breasts categorised as BIRADS 1.

Conclusions

SI is not inferior to FFDM when DBT slices are not available during image reading. SI can replace FFDM, reducing the dose by 45%.

Key Points

? Stand-alone SI demonstrated performance not inferior for lesion visibility as compared to FFDM.? Stand-alone SI demonstrated performance not inferior for lesion BIRADS categorisation as compared to FFDM.? Synthetic images provide important dose savings in breast tomosynthesis examinations.

     

Comparison of independent double readings and computer-aided diagnosis (CAD) for the diagnosis of breast calcifications

RATIONALE AND OBJECTIVES: The aim of the study is to compare independent double readings by radiologists and computer-aided diagnosis (CAD) in diagnostic interpretation of mammographic calcifications. MATERIALS AND METHODS: Ten radiologists independently interpreted 104 mammograms containing clustered microcalcifications. Forty-six of these were malignant and 58 were benign at biopsy. Radiologists read the images with and without a computer aid by using a counterbalanced study design. Sensitivity and specificity were calculated from observer biopsy recommendations, and receiver operating characteristic (ROC) curves were computed from their diagnostic confidence ratings. Unaided double-reading sensitivity and specificity values were derived post hoc by using three different objective rules and an additional rule of simulated-optimal double reading that assumed that consultations for resolving two radiologists' different independent diagnoses always produce the correct clinical recommendation. ROC curves of unaided double readings were obtained according to the literature. RESULTS: Single reading without computer aid yielded 74% sensitivity and 32% specificity, whereas CAD reading yielded 87% sensitivity and 42% specificity and appeared on a higher ROC curve (P < .0001). Three methods of formulating independent double readings generated sensitivities between 59% and 89%, specificities between 50% and 13%, and operating points that moved essentially along the average unaided single-reading ROC curve. ROC curves of unaided independent double readings showed small, statistically insignificant improvement over those of unaided single readings. Results of the simulated-optimal double reading were similar to CAD: 89% sensitivity and 50% specificity. CONCLUSION: Independent double readings of mammographic calcifications may not improve diagnostic performance. CAD reading improves diagnostic performance to an extent approaching the maximum possible performance.     

Improvement in radiologists' detection of clustered microcalcifications on mammograms. The potential of computer-aided diagnosis

Relatively simple, but important, detection tasks in radiology are nearing accessibility to computer-aided diagnostic (CAD) methods. The authors have studied one such task, the detection of clustered microcalcifications on mammograms, to determine whether CAD can improve radiologists' performance under controlled but generally realistic circumstances. The results of their receiver operating characteristic (ROC) study show that CAD, as implemented by their computer code in its present state of development, does significantly improve radiologists' accuracy in detecting clustered microcalcifications under conditions that simulate the rapid interpretation of screening mammograms. The results suggest also that a reduction in the computer's false-positive rate will further improve radiologists' diagnostic accuracy, although the improvement falls short of statistical significance in this study.     

Diagnosis of breast calcifications: comparison of contact, magnified, and television-enhanced images

Matched contact and microfocal-spot-magnified images of 31 breasts, each containing a cluster of microcalcifications within a biopsy-proved benign (n = 21) or malignant (n = 10) lesion, were evaluated. Each matched set consisted of one image magnified 1.5 or 2.0 times by a microfocal spot; one contact film-screen mammogram; and one television-digitized, enhanced, and optically magnified contact film-screen mammogram. Three experienced mammographers and three senior diagnostic radiology residents with 2 weeks of training in mammography interpreted the calcifications. The average area under the receiver-operating-characteristic curve for the experienced mammographers was 0.60 for contact radiographs, 0.61 for the television-digitized images, and 0.69 for the microfocal-spot-magnified radiographs. The less experienced senior residents scored below a random choice, 0.44, for the television-digitized images; 0.51 for contact radiographs; and 0.69 for the microfocal-spot-magnified radiographs. We conclude that when evaluating microcalcifications, radiologists without extensive experience in mammography should not substitute television-digitized and enhanced contact mammograms for microfocal-spot-magnified mammograms; rigorous clinical evaluation is needed before this system is accepted for clinical use.     

Zooming method (× 2.0) of digital mammography vs digital magnification view (× 1.8) in full-field digital mammography for the diagnosis of microcalcifications

The purpose of this study was to determine whether the interpretation of microcalcifications assessed on images zoomed (× 2.0) from digital mammograms is at least equivalent to that from digital magnification mammography (× 1.8) with respect to diagnostic accuracy and image quality. Three radiologists with different levels of experience in mammography reviewed each full-field digital mammography reader set for 185 patients with pathologically proven microcalcification clusters, which consisted of digital magnification mammograms (MAGs) with a magnification factor of 1.8 and images zoomed from mammograms (ZOOM) with a zoom factor of 2.0. Each radiologist rated their suspicion of breast cancer in microcalcific lesions using a six-point scale and the image quality and their confidence in the decisions using a five-point scale. Results were analysed according to display methods using areas under the receiver operating characteristic curves (A_z value) for ZOOM and MAGs to interpret microcalcifications, and the Wilcoxon matched pairs signed rank test for image quality and confidence levels. There was no statistically significant difference in the level of suspicion of breast cancer between the ZOOM and MAG groups (A_z = 0.8680 for ZOOM; A_z = 0.8682 for MAG; p = 0.9897). However, MAG images were significantly better than ZOOM images in terms of visual imaging quality (p < 0.001), and the confidence level with MAG was better than with ZOOM (p < 0.001). In conclusion, the performance of radiologists in the diagnosis of microcalcifications using ZOOM was similar to that using MAGs, although image quality and confidence levels were better using MAGs.Magnification mammography produces better spatial resolution and signal-to-noise ratio than does contact mammography. It is well established as a valuable adjunct to contact mammography, especially for the diagnosis of microcalcifications, despite the additional radiation exposure and increased radiation dose because of the shorter distance between the breast and X-ray source during examination [1–4].However, with respect to full-field digital mammography (FFDM), a few studies using zoomed images from contact mammograms have recently been reported and, as a result, a debate has arisen over whether a digital zooming system of FFDM can replace the magnification view of digital mammography [5–7]. Whereas Fischer et al [5] reported that zoomed images of a digital contact mammogram were equivalent to direct magnification of FFDM for the interpretation of microcalcifications, our previous report suggested that magnification mammography yielded better sensitivity and receiver operating characteristic (ROC) analysis than did zoomed images [7]. However, that study compared images zoomed by a factor of 1.3 with images magnified by a factor of 1.8. Therefore, we wondered whether using a zooming factor comparable to a magnification factor of 1.8 would yield the same results.The purpose of this study was to determine whether the diagnostic accuracy and image quality of microcalcification assessments using images twice zoomed from contact mammograms were equivalent to those obtained using digital magnification mammography by a magnification factor of 1.8.     

Comparing the performance of mammographic enhancement algorithms: a preference study

OBJECTIVE: The objective of this study was to compare the performance of four image enhancement algorithms on secondarily digitized (i.e., digitized from film) mammograms containing masses and microcalcifications of known pathology in a clinical soft-copy display setting. MATERIALS AND METHODS: Four different image processing algorithms (adaptive unsharp masking, contrast-limited adaptive histogram equalization, adaptive neighborhood contrast enhancement, and wavelet-based enhancement) were applied to one image of secondarily digitized mammograms of forty cases (10 each of benign and malignant masses and 10 each of benign and malignant microcalcifications). The four enhanced images and the one unenhanced image were displayed randomly across three high-resolution monitors. Four expert mammographers ranked the unenhanced and the four enhanced images from 1 (best) to 5 (worst). RESULTS: For microcalcifications, the adaptive neighborhood contrast enhancement algorithm was the most preferred in 49% of the interpretations, the wavelet-based enhancement in 28%, and the unenhanced image in 13%. For masses, the unenhanced image was the most preferred in 58% of cases, followed by the unsharp masking algorithm (28%). CONCLUSION: Appropriate image enhancement improves the visibility of microcalcifications. Among the different algorithms, the adaptive neighborhood contrast enhancement algorithm was preferred most often. For masses, no significant improvement was observed with any of these image processing approaches compared with the unenhanced image. Different image processing approaches may need to be used, depending on the type of lesion. This study has implications for the practice of digital mammography.     

Reproducibility of Computer-Aided Detection Marks in Digital Mammography

Objective

To evaluate the performance and reproducibility of a computer-aided detection (CAD) system in mediolateral oblique (MLO) digital mammograms taken serially, without release of breast compression.

Materials and Methods

A CAD system was applied preoperatively to the full-field digital mammograms of two MLO views taken without release of breast compression in 82 patients (age range: 33 - 83 years; mean age: 49 years) with previously diagnosed breast cancers. The total number of visible lesion components in 82 patients was 101: 66 masses and 35 microcalcifications. We analyzed the sensitivity and reproducibility of the CAD marks.

Results

The sensitivity of the CAD system for first MLO views was 71% (47/66) for masses and 80% (28/35) for microcalcifications. The sensitivity of the CAD system for second MLO views was 68% (45/66) for masses and 17% (6/35) for microcalcifications. In 84 ipsilateral serial MLO image sets (two patients had bilateral cancers), identical images, regardless of the existence of CAD marks, were obtained for 35% (29/84) and identical images with CAD marks were obtained for 29% (23/78). Identical images, regardless of the existence of CAD marks, for contralateral MLO images were 65% (52/80) and identical images with CAD marks were obtained for 28% (11/39). The reproducibility of CAD marks for the true positive masses in serial MLO views was 84% (42/50) and that for the true positive microcalcifications was 0% (0/34).

Conclusion

The CAD system in digital mammograms showed a high sensitivity for detecting masses and microcalcifications. However, reproducibility of microcalcification marks was very low in MLO views taken serially without release of breast compression. Minute positional change and patient movement can alter the images and result in a significant effect on the algorithm utilized by the CAD for detecting microcalcifications.     

A comparison of digitized storage phosphors and conventional mammography in the detection of malignant microcalcifications

The detectability of malignant tumor-derived microcalcifications with conventional mammography was compared to that with digital images (2000 X 2510 pixels by 10 bits) derived from a storage phosphor-based digital radiography system capable of 5 line pair/mm resolution at identical exposure factors (30 kVp, 250 mAs, 65 cm film-focus distance). Microcalcifications (50-800 microns in diameter) were randomly superimposed on a preserved human breast specimen. ROC analysis based on 480 observations made by four readers indicated that the ability to detect the calcifications with digital images (ROC area = 0.871 +/- 0.066) was equivalent to conventional mammography (ROC area = 0.866 +/- 0.075) despite lower spatial resolution. With digital mammography, 62% of all clusters were correctly localized, but only 23.6% of the individual calcifications were counted. With conventional mammography 61% of all clusters were correctly localized, but significantly more of the individual calcifications (31.5%) were counted.     

Computer-aided diagnosis in full digital mammography

RATIONALE AND OBJECTIVES: The authors clarify the detection rates for breast cancerous tumors and clustered microcalcifications with computer-aided diagnosis (CAD) based on Fuji Computed Radiography. The authors also determine whether mammographic reading with CAD contributes to the discovery of breast cancer. METHODS: Data acquired by Fuji Computed Radiography 9000, which consisted of 4148 digital mammograms including 267 cases of breast cancer, was transferred directly to an analysis workstation where an original software program determined extraction rates for breast tumors and clustered microcalcifications. Furthermore, using another 344 mammograms from 86 women, observer performance studies were conducted on five doctors for receiver operating characteristic (ROC) analysis. RESULTS: Sensitivity to breast cancerous tumors and clustered microcalcifications were 89.9% and 92.8%, respectively false-positive rates were 1.35 and 0.40 per image, respectively. The observer performance studies indicate that an average Az value for the five doctors was greater with the CAD system than with a film-only reading without CAD, and that a reading with CAD was significantly superior at P < 0.022. CONCLUSIONS: It has been shown that CAD based on Fuji Computed Radiography offers good detection rates for both breast cancerous tumors and clustered microcalcifications, and that the reading of mammograms with this CAD system would provide potential improvement in diagnostic accuracy for breast cancer.     

Interpretation of digital mammograms: comparison of speed and accuracy of soft-copy versus printed-film display

PURPOSE: To compare the speed and accuracy of the interpretations of digital mammograms by radiologists by using printed-film versus soft-copy display. MATERIALS AND METHODS: After being trained in interpretation of digital mammograms, eight radiologists interpreted 63 digital mammograms, all with old studies for comparison. All studies were interpreted by all readers in soft-copy and printed-film display, with interpretations of images in the same cases at least 1 month apart. Mammograms were interpreted in cases that included six biopsy-proved cancers and 20 biopsy-proved benign lesions, 20 cases of probably benign findings in patients who underwent 6-month follow-up, and 17 cases without apparent findings. Area under the receiver operating characteristic curve (A(z)), sensitivity, and specificity were calculated for soft-copy and printed-film display. RESULTS: There was no significant difference in the speed of interpretation, but interpretations with soft-copy display were slightly faster. The differences in A(z), sensitivity, and specificity were not significantly different; A(z) and sensitivity were slightly better for interpretations with printed film, and specificity was slightly better for interpretations with soft copy. CONCLUSION: Interpretation with soft-copy display is likely to be useful with digital mammography and is unlikely to significantly change accuracy or speed.     

Three-dimensional color-modulated display of myocardial SPECT perfusion distributions accurately assesses coronary artery disease.

The objective of this study was to compare visual assessment of 3-dimensional color-modulated (to counts) surface displays with visual assessment of oblique tomographic slices of myocardial SPECT perfusion distributions in the detection and localization of coronary artery disease (CAD). METHODS: Sixty-two consecutive patients (41 men, 21 women; mean age, 61 +/- 11 y) who had undergone conventional dual-isotope perfusion SPECT were retrospectively chosen; 50 had undergone coronary arteriography previously, and 12 had less than a 5% likelihood of CAD. Four readers interpreted the 3-dimensional displays and slices in separate sessions while unaware of the findings of previous readings, the interpretations of others, and the angiographic results. The readers used a 5-point scoring system. Their average score was used for receiver operating characteristic (ROC) analysis. The area under the ROC curves was determined so that the ability of the 2 methods to detect and localize CAD could be compared. RESULTS: No significant differences were found between visual interpretation of 3-dimensional displays and visual interpretation of slices. CONCLUSION: These preliminary results indicate that visual interpretation of 3-dimensional displays of myocardial perfusion SPECT distributions may someday replace visual assessment of conventional slices without loss of diagnostic accuracy.     

Computer-aided detection (CAD) in mammography: Does it help the junior or the senior radiologist?

OBJECTIVES: To evaluate the impact of a computer-aided detection (CAD) system on the ability of a junior and senior radiologist to detect breast cancers on mammograms, and to determine the potential of CAD as a teaching tool in mammography. METHODS: Hundred biopsy-proven cancers and 100 normal mammograms were randomly analyzed by a CAD system. The sensitivity (Se) and specificity (Sp) of the CAD system were calculated. In the second phase, to simulate daily practice, 110 mammograms (97 normal or with benign lesions, and 13 cancers) were examined independently by a junior and a senior radiologist, with and without CAD. Interpretations were standardized according to BI-RADS classification. Sensitivity, Specificity, positive and negative predictive values (PPV, NPV) were calculated for each session. RESULTS: For the senior radiologist, Se slightly improved from 76.9 to 84.6% after CAD analysis (NS) (one case of clustered microcalcifications case overlooked by the senior radiologist was detected by CAD). Sp, PPV and PNV did not change significantly. For the junior radiologist, Se improved from 61.9 to 84.6% (significant change). Three cancers overlooked by the junior radiologist were detected by CAD. Sp was unchanged. CONCLUSION: CAD mammography proved more useful for the junior than for the senior radiologist, improving sensitivity. The CAD system may represent a useful educational tool for mammography.