Conventional Mammograms Research Articles

Tomosynthesis in X-ray: proven additional value?

Digital breast tomosynthesis (DBT) is a new promising modality for breast imaging. Breast tomosynthesis is based on a full-field digital mammography (FFDM) platforms, and the DBT images are obtained in the same standard projections (cranio-caudal and mediolateral oblique views) as for conventional mammography [1,2]. The tomographic images or “slices” are usually reconstructed at 1mm intervals and presented in the default setting as thin “slices” on the dedicated work-station. The images may, however, also be displayed as a volume consisting of several slices (“slabs”). The idea of using DBT is that the shape and margins of breast masses may be more clearly delineated by reducing or eliminating overlapping tissue, and the ability to distinguish superimposed tissue from breast lesions would be improved. Thus, it is suggested that this new technology may improve the specificity as compared with conventional mammography. Furthermore, the elimination of superimposed breast tissue should theoretically improve the detection of lesions otherwise hidden by dense breast parenchyma. The ability of DBT to reduce or eliminate the interpretation problems caused by overlapping breast tissue may be particularly valuable in women with dense breasts. Furthermore, it is suggested that digital breast tomosynthesis may improve the detection of architectural distortion especially in women with heterogeneous dense breasts. Theoretically, the very thin spiculations seen in architectural distortion would be expected to be more easily identified on 1mm thin slices as compared with a conventional projection mammogram. There has been a lot of concern regarding the perception (detection) and analysis (characterization) of calcifications on digital breast tomosynthesis. Theoretically, micro-calcifications may represent a challenge for DBT due to the so-called “thin-sliceeffect” since only few or microcalcifications might be seen on each slice and not all calcifications of cluster as is the case on conventional FFDM projection images. Viewing the microcalcifications in a “slab”-mode may resolve some of these problems, and a larger study comparing sharpness, contrast, and diagnostic quality of microcalcifications concluded that calcifications can be demonstrated with equal or even greater clarity on DBT than on mammography [3]. Analysis of microcalcification clusters on DBT may have a learning curve effect. There have been only few publications on DBT in a clinical setting so far, and consequently the future role of tomosynthesis, whether its implementation will be in mammography screening or in clinical (i.e., “diagnostic”) imaging, or in both settings, is still not clear.

Fusion of dynamic contrast-enhanced magnetic resonance mammography at 3.0 T with X-ray mammograms: Pilot study evaluation using dedicated semi-automatic registration software

Rationale and objectives To evaluate the semi-automatic image registration accuracy of X-ray-mammography (XR-M) with high-resolution high-field (3.0 T) MR-mammography (MR-M) in an initial pilot study. Material and methods MR-M was acquired on a high-field clinical scanner at 3.0 T (T1-weighted 3D VIBE ± Gd). XR-M was obtained with state-of-the-art full-field digital systems. Seven patients with clearly delineable mass lesions >10 mm both in XR-M and MR-M were enrolled (exclusion criteria: previous breast surgery; surgical intervention between XR-M and MR-M). XR-M and MR-M were matched using a dedicated image-registration algorithm allowing semi-automatic non-linear deformation of MR-M based on finite-element modeling. To identify registration errors (RE) a virtual craniocaudal 2D mammogram was calculated by the software from MR-M (with and w/o Gadodiamide/Gd) and matched with corresponding XR-M. To quantify REs the geometric center of the lesions in the virtual vs. conventional mammogram were subtracted. The robustness of registration was quantified by registration of X-MRs to both MR-Ms with and w/o Gadodiamide. Results Image registration was performed successfully for all patients. Overall RE was 8.2 mm (1 min after Gd; confidence interval/CI: 2.0–14.4 mm, standard deviation/SD: 6.7 mm) vs. 8.9 mm (no Gd; CI: 4.0–13.9 mm, SD: 5.4 mm). The mean difference between pre- vs. post-contrast was 0.7 mm (SD: 1.9 mm). Conclusion Image registration of high-field 3.0 T MR-mammography with X-ray-mammography is feasible. For this study applying a high-resolution protocol at 3.0 T, the registration was robust and the overall registration error was sufficient for clinical application.

Development of Low-Dose Photon-counting Contrast-enhanced Tomosynthesis with Spectral Imaging

To demonstrate the feasibility of low-dose photon-counting tomosynthesis in combination with a contrast agent (contrast material-enhanced tomographic mammography) for the differentiation of breast cancer. All studies were approved by the institutional review board, and all patients provided written informed consent. A phantom model with wells of iodinated contrast material (3 mg of iodine per milliliter) 1, 2, 5, 10, and 15 mm in diameter was assessed. Nine patients with malignant lesions and one with a high-risk lesion (atypical papilloma) were included (all women; mean age, 60.7 years). A multislit photon-counting tomosynthesis system was utilized (spectral imaging) to produce both low- and high-energy tomographic data (below and above the k edge of iodine, respectively) in a single scan, which allowed for dual-energy visualization of iodine. Images were obtained prior to contrast material administration and 120 and 480 seconds after contrast material administration. Four readers independently assessed the images along with conventional mammograms, ultrasonographic images, and magnetic resonance images. Glandular dose was estimated. Contrast agent was visible in the phantom model with simulated spherical tumor diameters as small as 5 mm. The average glandular dose was measured as 0.42 mGy per complete spectral imaging tomosynthesis scan of one breast. Because there were three time points (prior to contrast medium administration and 120 and 480 seconds after contrast medium administration), this resulted in a total dose of 1.26 mGy for the whole procedure in the breast with the abnormality. Seven of 10 cases were categorized as Breast Imaging Reporting and Data System score of 4 or higher by all four readers when reviewing spectral images in combination with mammograms. One lesion near the chest wall was not captured on the spectral image because of a positioning problem. The use of contrast-enhanced tomographic mammography has been demonstrated successfully in patients with promising diagnostic benefit. Further studies are necessary to fully assess diagnostic sensitivity and specificity.

Cone-Beam CT for Breast Imaging: Radiation Dose, Breast Coverage, and Image Quality

The primary objectives of this pilot study were to evaluate the radiation dose, breast coverage, and image quality of cone-beam breast CT compared with a conventional mammographic examination. Image quality analysis was focused on the concordance of cone-beam breast CT with conventional mammography in terms of mammographic findings. This prospective study was performed from July 2006 through August 2008. Twenty-three women were enrolled who met the inclusion criteria, which were age 40 years or older with final BI-RADS assessment category 1 or 2 lesions on conventional mammograms within the previous 6 months. The breasts were imaged with a flat-panel detector-based cone-beam CT system, and the images were reviewed with a 3D visualization system. Cone-beam breast CT image data sets and the corresponding mammograms were reviewed by three qualified mammographers. The parameters assessed and compared in this pilot study were radiation dose, breast tissue coverage, and image quality, including detectability of masses and calcifications. The mammograms and cone-beam breast CT images were independently reviewed side by side, and the reviewers were not blinded to the other technique. The observed agreement and Cohen's kappa were used to evaluate agreement between the mammographic and cone-beam breast CT findings and interobserver agreement. Each subject responded to a questionnaire on multiple parameters, including comfort of the cone-beam breast CT examination compared with mammography. For a conventional mammographic examination, the average glandular radiation dose ranged from 2.2 to 15 mGy (mean, 6.5 [SD, 2.9] mGy). For cone-beam breast CT, the average glandular dose ranged from 4 to 12.8 mGy (mean, 8.2 [SD, 1.4] mGy). The average glandular dose from cone-beam breast CT was generally within the range of that from conventional mammography. For heterogeneously dense and extremely dense breasts, the difference between the mean dose of conventional mammography and that of cone-beam breast CT was not statistically significant (7.0 vs 8.1 mGy, p = 0.06). Breast tissue coverage was statistically significantly better with cone-beam breast CT than with mammography in the lateral (p < 0.0001), medial (p < 0.0001), and posterior (p = 0.0002) aspects. Mammography had statistically significantly better coverage than cone-beam breast CT in the axilla and axillary tail (p < 0.0001). Overall, most calcifications and all masses detected with mammography were also detected with cone-beam breast CT. The interobserver agreement on cone-beam breast CT was 83.7% in the detectability of imaging findings. The overall interobserver agreement on type of findings, size of findings (<1, 1-4.99, and > or = 5 mm), and location of findings was 77.2%, 84.8%, and 78.3%, respectively. The results of this study show that cone-beam breast CT can be used to image the entire breast from chest wall to nipple with sufficient spatial and contrast resolution for detection of masses and calcifications at a radiation dose within the range of that of conventional mammography.

Adjunctive ultrasound processing and display for breast cancer screening

An adjunctive ultrasound mammography system and associated methods are described comprising an adjunctive ultrasound display configured for quick, intuitive, interactive viewing of data derived from volumetric ultrasound scans, the data being displayed near a conventional x-ray mammogram display. Preferred embodiments for navigating among a thick-slice image array, a selected enlarged thick-slice image, and planar ultrasound views are described, including a preferred embodiment in which the planar ultrasound views are updated in real time as a cursor is moved across an active thick-slice image. In one preferred embodiment the thick-slice images are inverted prior to display, with non-breast areas of the image preferably segmented out and reset to dark. The inverted thick-slice images are of more familiar significance to radiologists having years of expertise in analyzing conventional x-ray mammograms. For example, the inverted thick-slice images allow benign features to be more easily dismissed as compared to non-inverted thick-slice images. Preferred embodiments for computing thick-slice image values from the volumetric scan data are also described that emphasize larger mass lesions in the resulting thick-slice images, and that compensate for mass lesions that straddle thick-slice region borders.

Dedicated breast computed tomography: Volume image denoising via a partial‐diffusion equation based technique

Dedicated breast computed tomography (CT) imaging possesses the potential for improved lesion detection over conventional mammograms, especially for women with dense breasts. The breast CT images are acquired with a glandular dose comparable to that of standard two-view mammography for a single breast. Due to dose constraints, the reconstructed volume has a non-negligible quantum noise when thin section CT slices are visualized. It is thus desirable to reduce noise in the reconstructed breast volume without loss of spatial resolution. In this study, partial diffusion equation (PDE) based denoising techniques specifically for breast CT were applied at different steps along the reconstruction process and it was found that denoising performed better when applied to the projection data rather than reconstructed data. Simulation results from the contrast detail phantom show that the PDE technique outperforms Wiener denoising as well as adaptive trimmed mean filter. The PDE technique increases its performance advantage relative to Wiener techniques when the photon fluence is reduced. With the PDE technique, the sensitivity for lesion detection using the contrast detail phantom drops by less than 7% when the dose is cut down to 40% of the two-view mammography. For subjective evaluation, the PDE technique was applied to two human subject breast data sets acquired on a prototype breast CT system. The denoised images had appealing visual characteristics with much lower noise levels and improved tissue textures while maintaining sharpness of the original reconstructed volume.

Microcalcifications of Breast Tissue: Appearance on Synchrotron Radiation Imaging with 6-μm Resolution

The purpose of this study was to use synchrotron radiation imaging with 6-microm resolution to evaluate amorphous and pleomorphic breast tissue microcalcifications. Synchrotron radiation imaging depicted microcalcifications as small as 24 microm. Imaging with this technique revealed that most amorphous and pleomorphic calcifications on conventional mammograms are clusters of fine specks and that in addition to the shape or density of a speck, the distribution density of clustered specks is a factor determining the apparent shape.

SU‐EE‐A2‐01: Evaluation Based On Breast Tomosynthesis of Amorphous Selenium Full Field Digital Mammography System

Purpose: Our goal is to develop and evaluate breast tomosynthesis of amorphous selenium (a‐Se) based full field digital mammography (FFDM) system. The clinical value of tomosynthesis will be to provide additional clinical information in order to improve decision making accuracy to either confirm or exclude a suspected abnormality, verify correct target for biopsies and analyze tumor margin better to get knowledge of the possible extent breast cancer. Method and Materials: The prototype of tomosynthesis full field digital mammography system which is used in evaluation is based on amorphous selenium flat‐panel detector technology. The overall thickness of the selenium structure is 200μm, and the pixel size on this detector is 85μm. The total arc of the breast tomosynthesis system is 60° (−30° to +30°) and tomosynthesis sequence is performed at approximately 1–1.5 times the radiation dose of a conventional mammogram including 15 low‐dose exposures. Reconstruction methods will be also discussed. Results: Based on the experimental results of this study, we believe that FFDM tomosynthesis can be used to determine whether a mammography finding is caused by a real abnormal lesion or by superimposition of normal parenchymal structures to be able to diagnose and analyze the findings properly. Conclusion: We need to be able to find screening and diagnostic method, which has high sensitivity as well high specificity to avoid unnecessary surgical interventions and to be able to detect breast cancer in its early stage. The technology has already proved its benefits in detecting early breast cancers and the capability of diagnosing breast cancers. Although FFDM tomosynthesis evaluation needs to concentrate on proving that it is clinically successful in the sense of increased sensitivity and specificity, with lower cost of workflow and reduced risk. Conflict of Interest: Mari Varjonen and Pekka Strommer are employees of Planmed Oy.

Digital mammography using storage phosphor plate technique — optimizing image processing parameters for the visibility of lesions and anatomy

Digital mammograms from a storage phosphor plate system for general radiography were compared to conventional mammograms by means of visual grading analysis (VGA). For the digital images, image processing parameters were optimized and evaluated through observer preference analysis (OPA). The results of the VGA showed significantly better gradings for the conventional mammograms for parenchyma, linear structures, and cysts, and significantly better gradings for the digital mammograms for the skin surface. For calcifications, no significant difference was seen. For the OPA, contrast enhanced mammograms graded significantly best. Using standard image processing, the digital mammograms were considered as adequate for diagnosis in 49% of the cases, as uncertain in 20%, and as inadequate in 31%. However, the observers differed considerably in their gradings both in the VGA and in the OPA.

Calcified trichinosis of pectoral muscle: mammographic appearance

By mammographic screening we had detected six asymtomatic women who showed numerous tiny and well-delineated round to ovoid microcalcifications superimposed on pectoral shadows, in the oblique medio-lateral (OML) view. Our objective was to achieve a better evaluation of these calcifications and investigate their origin. Magnified mammograms of pectoral muscles were done in the six women. A questionnaire concerning the patients' diets was also administered. Trichinella antibody titres were quantified by sero-agglutination. Microcalcifications within pectoral muscle fibres were demonstrated in all the cases. Five women admitted to having eaten home-made pork products in the past. One of them showed a slightly elevated antibody titre. We confirmed the suspected diagnosis of calcified trichinosis by a surgical biopsy of the pectoral muscle performed on one of the patients. We conclude that chronic calcified trichinosis of the pectoral muscle can be visualised in the OML view of a conventional mammogram. The mammographic appearance of this entity is very characteristic and biopsy would not be required for its diagnosis in the future.

Role of equalisation mammography of dense breasts

Parenchymal patterns characteristic of dense breasts are known to degrade the mammographic detection of small breast cancers and microcalcifications. This arises from large variations in exposure of the film, resulting in reduced image contrast over areas of suboptimal exposure. Based on sensitometric measurements of mammograms from a typical patient population, it is shown that over 60% of a typical mammogram in Wolfe's DY classification was found to be exposed suboptimally, suggesting a significant margin for improving mammography for these patients. In order to address this problem, a prototype mammographic version of scanning equalisation radiography (MSER) has been developed, which delivers a patient-specific spatially non-uniform distribution of breast exposure, adjusted to maintain optimal film exposure and contrast over the entire mammogram. Anthropomorphic phantom MSER images show a marked improvement in subjective image quality relative to conventional mammograms, while exhibiting a similar radiation risk. The detection of small microcalcifications and fibrils over clinically significant breast densities is found to be improved by factors eight and four, respectively. Such a system may be clinically practical through the use of multiple-beam equalisation methods with available X-ray tube technology.

Localization of impalpable breast masses: value of sonography in the operating room and scanning of excised specimens.

Despite the variety of techniques available, mammographically guided preoperative localization of impalpable masses in the breast can be a difficult procedure for radiologists. Furthermore, in a few cases, an impalpable lesion is clearly seen on sonograms and yet poorly seen or not visible on mammograms. Accordingly, we studied the value of localizing impalpable masses with sonography in the operating room and of scanning excised specimens to confirm successful removal of the mass. All of the lesions were visible on preoperative sonograms. Twenty-six patients had sonographic examination of the breast in the operating room to guide the localization of an impalpable mass previously seen on sonograms. In eight patients, the lesion was poorly seen or not seen on conventional mammograms. Localizing techniques included one or more of the following: insertion of a needle, injection of dye, or simple marking on the skin. In 18 cases, sonography of the freshly excised specimen was done in the operating room. The sizes of the masses (13 fibroadenomas, 10 carcinomas, two cysts, and one tubular adenoma) measured on the sonograms ranged from 0.6 to 2.7 cm (mean +/- SD, 1.2 +/- 0.5 cm). In all 26 cases, the mass was clearly identified on sonograms obtained in the operating room. In all 18 cases in which it was used, sonography of the specimen correctly showed the presence or absence of the lesion. In two cases, sonographic determination of the absence of the lesion in the specimen prompted immediate reexcision, which was successful. Our experience shows that sonography in the operating room is a rapid and efficient method of localizing impalpable breast masses that have been seen on sonograms. Sonography of the specimen can indicate within seconds whether the excision has been successful. This technique is particularly valuable for masses that are not visible or only poorly visible on mammograms.

Mammographic scanning equalization radiography.

It is well recognized that variations in breast thickness and parenchymal composition can produce a range of exposure which exceeds the latitude of high contrast mammographic film/screen combinations. Optimal imaging of the dense breast is desired since 30%-60% of women present with dense breasts, and they are believed to be at the highest relative risk of developing breast cancer. The application of scanning equalization radiography to mammography has been investigated through the construction and characterization of a prototype mammographic scanning equalization radiography (MSER) system, designed to image mammographic phantoms. The MSER system exposes a Min-R/MRH cassette by raster scanning a 2.0 x 1.6 cm beam of pulsed x-rays across the cassette. A scanning detector behind the cassette measures the local x-ray transmission of the breast. Feedback of the transmission information is used to modulate the duration of each x-ray pulse, to equalize the film exposure. The effective dynamic range of the MSER system is 25 times greater than that of conventional mammography. Artifact-free images of mammographic phantoms show that MSER effectively overcomes the latitude limitations of film/screen mammography, enabling high contrast imaging over a wide range of object x-ray transmission. Anthropomorphic phantom images show that MSER offers up to a sixfold increase in film contrast in the normally underexposed regions of conventional mammograms. Characterization of the entrance exposure shows that there is not a significant difference in exposure between MSER and conventional mammographic techniques, suggesting that both would pose comparable risk to the patient. Calculations show that the construction of a clinical multiple beam MSER system is feasible with minor changes to existing technology.

Improved image quality for dense breasts in mammography.

Within the UK breast scanning age range of 50-65 years, about 15% of breasts show a dense structure that is underexposed in conventional mammography. This gives rise to a severe reduction in contrast. Methods of improving this contrast by variation of exposure factors are explored, using a Dupont phantom that has a simulated dense breast structure. Results are assessed by considering measured contrast from a Perspex stepwedge, and by obtaining relative scores, on a scale of 1-10, from 15 radiologists involved in mammography. It is concluded from both these methods that approximately doubling the mAs at the normal kV is preferable to increasing the kV by more than a small amount. A modified mammographic technique on these lines could be valuable in selected cases where a previous conventional mammogram was available, i.e. assessment stage or repeat screening in a screening programme, or symptomatic patients. Practical problems in choosing exposure factors and the magnitude and implications of the increased dose are discussed.

Digital Luminescence Mammography

In a pilot study, mammography using digital luminescence was compared to conventional film-screen mammography regarding detectability of micro-calcifications and malignant tumors. The data processing algorithms were designed by the manufacturer to produce an image with characteristics close to conventional mammograms. Three observers reviewed 99 digital and their corresponding conventional mammograms. There was no difference in the detectability of micro-calcifications between digital and conventional mammography. On the digital mammograms, however, artifacts were misjudged as micro-calcifications. In an ROC analysis regarding malignant breast tumors, no significant difference was found between the 2 systems. There was a slight, but not significant, difference between the results of different observers regarding the digital system.

Digital Luminescence Mammography

In a pilot study, mammography using digital luminescence was compared to conventional film-screen mammography regarding detectability of micro-calcifications and malignant tumors. the data processing algorithms were designed by the manufacturer to produce an image with characteristics close to conventional mammograms. Three observers reviewed 99 digital and their corresponding conventional mammograms. There was no difference in the detect-ability of micro-calcifications between digital and conventional mammography. on the digital mammograms, however, artifacts were misjudged as micro-calcifications. in an ROC analysis regarding malignant breast tumors, no significant difference was found between the 2 systems. There was a slight, but not significant, difference between the results of different observers regarding the digital system.

Dual‐energy mammography: A detector analysis

Dual-energy mammography acquisition scenarios employing single-shot techniques are examined using computer simulation. A figure of merit of the signal-to-noise ratio squared over the glandular dose was chosen for the optimization task due to its exposure independence. Doses were evaluated using Monte Carlo techniques. The effects of kilovoltage, prepatient filtration, front detector thickness, mid-detector filtration thickness and composition were studied. Of the six detector pairs studied (Y2O2S/Gd2O2S, SrFBr/BaFBr, Y2O2S/LaOBr, Y2O2S/CaWO4, Y2O2S/YTaO4, and Y2O2S/LuTaO4), Y2O2S/Gd2O2S and SrFBr/BaFBr were found to be the best combinations. The effects of scatter and signal quantization were also examined. An alternative display technique whereby the tissue-subtracted (i.e., calcium) image is colorized and overlaid onto the conventional mammogram is introduced.

Digital Mammography

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.

Microfocal Spot Magnification Mammography Using Xeroradiographic and Screen-Film Recording Systems

Direct radiographic magnification (1.5X) of the breast, using a microfocal spot x-ray tube and either a xeroradiographic or screen-film recording system, produces images superior in quality (improved resolution, reduced noise) to conventional contact mammograms. Six hundred twenty-one patients had a single magnification mammogram in addition to conventional mammography; 216 subsequently underwent biopsy within one month of study. The additional magnification mammogram increased the diagnostic accuracy of the conventional examination in 40% of the pathologically proved cases, particularly among those for which conventional mammograms were interpreted as equivocal for malignancy. The superior image quality of magnification mammograms appears useful in distinguishing malignant from benign breast disease.