Perioperative cardiovascular morbidity in patients with coronary artery disease undergoing vascular surgery after percutaneous transluminal coronary angioplasty

PURPOSE: To develop a method for receiver operating characteristics (ROC) studies in mammography. MATERIAL AND METHODS: We developed a phantom based on excised breast tissue and overlay tiles that could be arranged in an arbitrary pattern across the surface of the breast tissue. Some of the tiles contained structures simulating calcifications or masses that produced image contrast near the experimentally determined detection threshold. Based on this phantom, a methodology for performing ROC studies in mammography was developed. The ROC curves were constructed from reporting schemes filled in by radiologists at five different laboratories. The curves were determined by a novel method: a non-linear least-squares fit of a mathematical model to the data. RESULTS: There were large differences among the areas under the ROC curves obtained from the five laboratories.     

Effects of ambient light and view box luminance on the detection of calcifications in mammography

OBJECTIVE: Viewing conditions can affect diagnostic performance differently depending on background optical densities. We quantified detection accuracy when viewing calcifications in glandular tissue under recommended viewing conditions versus accuracy with lower view box luminance and higher ambient lighting. MATERIALS AND METHODS: A phantom with adipose, 50% adipose and 50% glandular, and glandular-simulating material was imaged, and images were interpreted by five medical imaging physicists using two lighting conditions: the recommended one, high view box luminance (4365 nits) with low ambient light (25 lx), and a suboptimal one, low view box luminance (1763 nits) with moderate ambient lighting (290 lx). Then, a dense (Breast Imaging Reporting and Data System breast composition pattern type 4) unfixed cadaveric breast with numerous native calcifications was imaged 28 times. Nineteen of the films had added clusters of simulated calcifications. Three radiology fellows, each with 11 months of training in mammography, identified the added calcification clusters in the images under the two lighting conditions. Changes in phantom analysis and accuracy of the clinical diagnosis were compared for each lighting condition. RESULTS: On mammograms of the phantom, both speck and fibril identification were degraded by an average of 1.4 objects for the adipose-simulating section (with its darker optical density). For medium optical densities, found in the section with the simulation of 50% glandular and 50% adipose tissue, suboptimal lighting conditions had little or no effect on speck and fibril identification. For sections of the phantom that simulated glandular tissue, an average of 0.6 specks or fibers were not seen when lighting was suboptimal. With the dense cadaveric breast, the fraction of added calcification clusters detected by the three observers improved by an average of 17% when low luminance viewers and high ambient light were replaced with recommended viewing conditions; individual scores of the observers improved significantly: p values ranged from .02 to .05. CONCLUSION: Luminance of the view box and ambient lighting significantly affect detection of calcifications in dense breasts when images are interpreted by radiologists with about 1 year of training in mammography. Detection of calcifications in phantoms is primarily degraded for adipose tissue with its darker optical density. However, when lighting conditions are suboptimal, some observers also have trouble detecting calcifications in glandular tissue with its low optical density.     

Mammography grid performance

PURPOSE: To measure directly the grid performance of mammography units for the range of breast thicknesses and x-ray tube potentials encountered in clinical practice. MATERIALS AND METHODS: Contrast improvement factors and Bucky factors were determined for four mammographic units as a function of x-ray tube potential (25, 30, and 35 kVp), phantom thickness (2, 4, and 8 cm) and, on one unit, three target-filter combinations. Three units used a linear grid; one, a cellular grid. Two methods were used for nongrid measurements. RESULTS: For all units tested, contrast improvement factor increased with increased phantom thickness and with increased kilovolt peak level for the 8-cm-thick phantom and changed little with kilovolt peak level for 2- and 4-cm-thick phantoms. At 25 and 30 kVp, contrast improvement factor performance with the linear grids was comparable; with the cellular grid, it was 5%-10% higher. In all cases, the Bucky factor increased with increased phantom thickness and decreased with increased tube potential. CONCLUSION: Differences in grid performance exist. At 25 and 30 kVp, the cellular grid exhibited superior contrast improvement factor performance, whereas one of the linear grids exhibited superior Bucky factor performance. Measured contrast improvement and Bucky factors are dependent on nongrid technique. Cassette tunnels introduce scatter and should not be used with nongrid or magnification techniques.     

National survey of mammographic facilities in 1985, 1988, and 1992

PURPOSE: To determine trends in mammography in the United States. MATERIALS AND METHODS: A sample of mammographic facilities was selected for each year of the Nationwide Evaluation of X-ray Trends. The same protocol was followed for the 1985, 1988, and 1992 surveys. Data were collected with use of the same imaging phantom for all three surveys and also with a different phantom in the 1988 and 1992 surveys. RESULTS: Of the 356 facilities surveyed in 1992, 59% claimed to be in compliance with the Health Care Financing Administration (HCFA) mammography requirements, 42% were accredited by the American College of Radiology (ACR), and 23% did not hold credentials from either the HCFA or the ACR. Since 1985, there has been a 34% improvement in acceptable phantom image quality score and a 20% decrease in the mean glandular dose. CONCLUSION: Mammography as practiced today is essentially a screen-film technique. Mammographic phantom image quality has improved considerably. The overall mean glandular dose has decreased primarily because of the elimination of xeroradiography.     

Storage phosphor direct magnification mammography in comparison with conventional screen-film mammography--a phantom study

Contact mammography with current photostimulable storage phosphors is hampered by its low spatial resolution. Detail visualization can be improved by geometric magnification radiography which enlarges small details to exceed inherent image noise. This study compares storage phosphor mammography using a dedicated direct magnification system with state-of-the-art conventional screen-film mammography. Storage phosphor direct magnification survey views (1.7x) and spot views (4x) were obtained with a prototype mammography unit providing focal spot sizes of 120-40 microns. Conventional technique screen-film survey views (1.1x) and spot views (1.8x) served as comparison. A contrast detail study and a receiver operating characteristic (ROC) analysis using an anthropomorphic breast phantom with superimposed microcalcifications was performed. Contrast detail resolution in the digital and conventional survey views were equivalent. For the spot views, contrast detail resolution was significantly higher with the digital technique (p < 0.001). ROC analysis of 400 observations demonstrated a significantly higher performance (p < 0.001) with digital images versus conventional screen-film mammograms. The area under the ROC curve (Az) in the digital survey views was 0.76 +/- 0.07 versus 0.59 +/- 0.02 in the conventional technique. In digital spot views, Az was 0.82 +/- 0.07 as compared with 0.66 +/- 0.04 in the conventional spot views. These results suggest that storage phosphor digital mammography in conjunction with direct geometric magnification technique may be superior to conventional screen-film mammography in the detection of microcalcifications.     

Phantom standards with temperature- and field-independent relaxation rates for magnetic resonance imaging

RATIONALE AND OBJECTIVES: For use as magnetic resonance imaging reference standards, the optimal set of phantoms should cover a wide range of T1 values, with each phantom having a T1 that is stable over time and is independent of temperature and magnetic field strength. To date, no set of phantoms fulfilling these four requirements has been prepared. In the current work, the construction of such optimal phantom standards is attempted. METHODS: Two linear gadolinium DTPA polymers are used: the first with relaxivities that are independent of temperature and magnetic field strength, and the second with relaxivities that are independent of magnetic field strength, but have an opposite temperature dependence from that of the 1/T1 of the diamagnetic matrix (agarose gel or water). Depending on the desired T1, either one or a combination of the two agents is used. RESULTS: Phantom standards were constructed with 1/T1 values that are independent of temperature (20-35 degrees C) and magnetic field strength (0.47-1.2 T) over a wide range of 1/T1 values (> or = 0.95 s-1). Phantom standards prepared in water were found to be stable with respect to 1/T1 for at least 18 months. CONCLUSIONS: Stable phantoms standards have been constructed covering a wide range of T1 values, where the T1 of any particular phantom is independent of temperature and magnetic field strength for magnetic resonance imaging conditions.     

Fast inversion-recovery MR: the effect of hybrid RARE readout on the null points of fat and cerebrospinal fluid

PURPOSE: To evaluate the effect of the hybrid RARE (rapid acquisition with relaxation enhancement) readout, commonly coupled to inversion-recovery pulse sequences, on the null inversiton time (TI) of fluid and fat using both phantoms and human volunteers. METHODS: Two phantoms, simulating fat (phantom A) and cerebrospinal fluid (phantom B), respectively, were imaged using a fast inversion-recovery sequence that coupled an inversion-recovery preparation pulse to a hybrid RARE readout. At repetition times (TRs) ranging from 700 to 20,000, the TI necessary to null the signal from each phantom (null TI) was determined for an echo train length of 4, 6, 8, 10, 12, 14, 16, 18, and 20, respectively. Plots of null TI versus echo train length at different TRs were generated for both phantoms. Fast inversion-recovery MR imaging of the cervical spine and brain was performed in healthy volunteers. At a fixed TR and TI, the adequacy of signal suppression from bone marrow and cerebrospinal fluid was assessed as a function of echo train length. RESULTS: There was a gradual decrease of null TI for both phantoms with echo train length. This decrease persisted at longer TRs for phantom B (T1 = 3175 +/- 70 milliseconds) than for phantom A (T1 = 218 +/- 5 milliseconds). In the human volunteers, there was a gradual loss of suppression of signal from bone marrow and cerebrospinal fluid, with changes in the hybrid RARE readout. CONCLUSION: To optimize specific tissue suppression, radiologists implementing fast inversion-recovery MR imaging should be aware of the effects of the hybrid RARE readout on null TI.     

Computer analysis of mammography phantom images (CAMPI): an application to the measurement of microcalcification image quality of directly acquired digital images

The purpose of this investigation was to apply the recently developed CAMPI (computer analysis of mammography phantom images) method to a Fischer Mammotest Stereotactic Digital Biopsy machine. Another aim was to further elucidate the nature of the empirically introduced CAMPI measures. Images of an American College of Radiology (ACR) accreditation phantom centered on the largest two speck groups were obtained on this machine under a variety of x-ray conditions. An additional measure, alternative SNR (ASNR) is introduced which is complementary to the SNR measure. Analyses of the Mammotest images revealed that the mAs and kVp dependencies of the CAMPI measures could be understood from basic imaging physics principles. It is shown that: (1) the measures reflect the expected linearity of the digital detector and Poisson photon statistics; (2) under automatic exposure control (AEC) conditions the signal (SIG) measure is proportional to subject contrast; and (3) under AEC conditions the noise (NOI) measure is proportional to the square root of the average absorbed photon energy. Correspondence with basic imaging physics principles shows that the measures are significantly free of artifacts. Precision of the CAMPI measures exceeds that of human observers by orders of magnitude. CAMPI measures are expected to be more relevant to clinical mammography than Fourier metrics as the measurements are done on objects of arbitrary shape and size that were designed by the manufacturer to resemble various detection tasks in mammography. It is concluded that CAMPI can perform objective and highly precise evaluations of phantom image quality in mammography. It could be used as a sophisticated quality control tool, as a replacement for the current ACR/MQSA phantom evaluation program, and to evaluate the rapidly evolving digital mammography technology.     

The influence of dressings on venous ulcer healing--a randomised trial

PURPOSE: Since the routine use of storage phosphor systems for mammography has been limited by its inadequate spatial resolution of 5 linepairs/mm, a combination of a magnification mammography technique with storage phosphor plates was investigated to detect microcalcifications. MATERIAL AND METHODS: A new mammography system with a microfocus tube using an anode of 0.05-0.12 mm allowed to obtain survey views of the breast with 1.7x magnification (m), and spot views with 4x magnification. The digital image receptor comprised a high resolution storage phosphor plate. To determine spatial resolution, contrast transfer curves were obtained, and the detection of microcalcifications was investigated by ROC (receiver operating characteristic) analysis. RESULTS: Spatial resolution for digital survey views (m = 1.7) was 8 linepairs/mm and for spot views (m = 4) was 18 linepairs/mm. ROC analysis demonstrated a significantly higher performance of the digital magnification technique compared to the conventional screen-film mammography technique. CONCLUSIONS: The limitations of digital mammography with respect to spatial resolution can be overcome by using a high magnification technique.     

Establishing minimum performance standards, calibration intervals, and optimal exposure values for a whole breast digital mammography unit

Methods are developed to establish minimum performance standards, calibration intervals, and criteria for exposure control for a whole breast digital mammography system. A prototype phantom was designed, and an automatic method programmed, to analyze CNR, resolution, and dynamic range between CCD components in the image receptor and over time. The phantom was imaged over a 5 month period and the results are analyzed to predict future performance. White field recalibration was analyzed by subtracting white fields obtained at different intervals. Exposure effects were compared by imaging the prototype phantom at different kVp, filtration (Mo vs Rh) and mAs. Calcification detection tests showed that phantom images, obtained at 28 kVp with a Mo/Mo anode/filter and low mAs technique, often could not depict Al2O3 specks 0.24 mm in diameter, while a 28 kVp Mo/Rh, higher mAs technique usually could. Stability of the system tested suggests that monthly phantom imaging may suffice. Differences in CCD performance are greater (12%) than differences in a single CCD over time (6%). White field recalibration is needed weekly because of pixel variations in sensitivity which occur if longer intervals between recalibration occur. When mean glandular dose is matched, Rh filtration gives better phantom performance at 28 kVp than Mo filtration at 26 kVp and is recommended for clinical exposures. An aluminum step wedge shows markedly increased dynamic range when exit exposure is increased by using a higher energy spectrum beam. Phantoms for digital mammography units should cover the entire image receptor, should test intersections between components of the receptor, and should be automatically analyzed.     

Interleukin-8 (IL-8) and monocyte chemotactic and activating factor (MCAF/MCP-1), chemokines essentially involved in inflammatory and immune reactions

We analyzed the noise characteristics of two-dimensional (2-D) and three-dimensional (3-D) images obtained from the GE Advance positron emission tomography (PET) scanner. Three phantoms were used: a uniform 20-cm phantom, a 3-D Hoffman brain phantom, and a chest phantom with heart and lung inserts. Using gated acquisition, we acquired 20 statistically equivalent scans of each phantom in 2-D and 3-D modes at several activity levels. From these data, we calculated pixel normalized standard deviations (NSD's), scaled to phantom mean, across the replicate scans, which allowed us to characterize the radial and axial distributions of pixel noise. We also performed sequential measurements of the phantoms in 2-D and 3-D modes to measure noise (from interpixel standard deviations) as a function of activity. To compensate for the difference in axial slice width between 2-D and 3-D images (due to the septa and reconstruction effects), we developed a smoothing kernel to apply to the 2-D data. After matching the resolution, the ratio of image-derived NSD values (NSD2D/NSD3D)2 averaged throughout the uniform phantom was in good agreement with the noise equivalent count (NEC) ratio (NEC3D/NEC2D). By comparing different phantoms, we showed that the attenuation and emission distributions influence the spatial noise distribution. The estimates of pixel noise for 2-D and 3-D images produced here can be applied in the weighting of PET kinetic data and may be useful in the design of optimal dose and scanning requirements for PET studies. The accuracy of these phantom-based noise formulas should be validated for any given imaging situation, particularly in 3-D, if there is significant activity outside the scanner field of view.     

Changes in photon dose distributions due to breast prostheses

PURPOSE: Subcutaneous prosthetic implants had been routinely used for cosmetic augmentation and for tissue replacement following mastectomy over the last 15 years. The implants come in many forms as the gel filler material and surrounding shell material(s) vary significantly. METHODS AND MATERIALS: This study uses a thin window parallel-plate chamber and thermoluminescent dosimeters to quantify and dosimetric changes to surrounding breast tissue due to the presence of the prosthesis. A mammographic phantom was compared to four commercial prostheses, namely two silicon gel fillers within two different shells (silicon or silicon/polyurethane), a tri-glyceride within silicon and a bio-oncotic gel within silicon/polyurethane. The latter two implants were designed with a low-Z fill for diagnostic imaging benefits. RESULTS: Ion chamber results indicate no significant alteration of depth doses away from the implant with only minor canceling (parallel opposed) interface perturbations for all implants. In addition the physical changes to the irradiated prostheses were quantified by tonometry testing and qualified by color change. Each implant exhibited color change following 50 Gy, and the bio-oncotic gel became significantly less formable following irradiation, and even less formable 6 weeks postirradiation. CONCLUSION: The data indicates that prostheses do not affect the photon beam distribution, but radiation does affect the prostheses.     

An automated method for mapping human tissue permittivities by MRI in hyperthermia treatment planning

This paper presents an automatic method to obtain tissue complex permittivity values to be used as input data in the computer modelling for hyperthermia treatment planning. Magnetic resonance (MR) images were acquired and the tissue water content was calculated from the signal intensity of the image pixels. The tissue water content was converted into complex permittivity values by monotonic functions based on mixture theory. To obtain a water content map by MR imaging a gradient-echo pulse sequence was used and an experimental procedure was set up to correct for relaxation and radiofrequency field inhomogeneity effects on signal intensity. Two approaches were followed to assign the permittivity values to fat-rich tissues: (i) fat-rich tissue localization by a segmentation procedure followed by assignment of tabulated permittivity values; (ii) water content evaluation by chemical shift imaging followed by permittivity calculation. Tests were performed on phantoms of known water content to establish the reliability of the proposed method. MRI data were acquired and processed pixel-by-pixel according to the outlined procedure. The signal intensity in the phantom images correlated well with water content. Experiments were performed on volunteers' healthy tissue. In particular two anatomical structures were chosen to calculate permittivity maps: the head and the thigh. The water content and electric permittivity values were obtained from the MRI data and compared to others in the literature. A good agreement was found for muscle, cerebrospinal fluid (CSF) and white and grey matter. The advantages of the reported method are discussed in the light of possible application in hyperthermia treatment planning.     

Indicator measurement in tissues: CT with iohexol versus storage-phosphor autoradiography with carbon-14-labeled inulin

RATIONALE AND OBJECTIVES: Computed tomography (CT) provides accurate measurement of blood iodine concentration in vivo, as well as in phantoms simulating tissue; however, its ability to measure radiopaque agents in biologic tissues in comparison with a standard technique does not seem to have been demonstrated. To validate the performance of CT imaging for quantification of contrast media in a variety of biologic tissues in vivo, a comparison between CT imaging with an iodinated contrast agent (iohexol) and the reference tracer quantification technique (storage-phosphor autoradiography with carbon-14-labeled inulin) was performed. MATERIALS AND METHODS: Six New Zealand White rabbits were injected intravenously with a cocktail of iohexol and C-14-labeled inulin at different dose ratios and sacrificed shortly after injection to arrest blood flow at different stages of tissue tracer distribution. One rabbit received no iohexol-inulin mixture and provided baseline data. Liver, spleen, kidneys, testis, and heart were excised and rapidly frozen. Each organ was scanned with CT (1-mm contiguous sections) to determine tissue iodine distribution. Twenty-micrometer tissue slices were made in the same planes in which the CT images had been acquired, and storage-phosphor screen autoradiography was performed to quantify C-14-labeled inulin distribution. RESULTS: Digital image analysis of CT images and autoradiograms was performed on spatially matched regions, and resultant tracer concentrations were compared. Tracer concentrations were highly correlated, with resultant R2 values exceeding 0.9 in all tissues. CONCLUSION: The highly correlated results for iodinated tracer quantification in tissues for CT versus those obtained with the reference technique validate the performance of CT as an accurate means of measuring concentration of radiopaque agent in tissue, independent of tracer dose.     

The quality of impressions for crowns and bridges received at commercial dental laboratories

OBJECTIVE: To determine the quality of impressions for crown and bridge work made in general dental practice. DESIGN AND SETTING: All impressions for crown and bridge work which had been sent to four commercial dental laboratories in the UK were assessed by two examiners, each laboratory being visited on two occasions. MATERIALS AND METHODS: 290 cases which had been received by the laboratories on the days of the visits were assessed for a number of factors related to quality. There was no selection or rejection--all impressions received were examined. RESULTS: Flexible plastic trays were used for the majority of working impressions for crown and bridge work in general dental practice (72%), many had been re-used (> 13%), defects in the recording of the prepared teeth were common, and cross infection control was not routine. CONCLUSIONS: Quality standards for impressions for crown and bridge work in general dental practice in the UK are a cause for concern if the sample of cases seen in this study is typical.     

An index for diagnostic accuracy in the multiple disease setting

RATIONALE AND OBJECTIVES: Evaluation of diagnostic accuracy in the clinical environment should entail some assessment of performance in patients with multiple abnormalities. Although receiver operating characteristic (ROC) curves often are used to assess the diagnostic accuracy of imaging systems, the concept is not easily generalizable to patients with multiple abnormalities. I propose a measure of diagnostic accuracy that is a generalization of the area under the ROC curve for a single disease. METHODS: The proposed measure of diagnostic accuracy is a weighted average of the area under individual ROC curves for the single disease setting and of components representing areas under ROC curves constructed for patients with multiple diseases. Several options are discussed for scoring the presence of abnormality for patients who have two or more abnormalities. RESULTS: Methods of estimating diagnostic accuracy are demonstrated on a set of data in which more than one third of the abnormal cases included multiple abnormalities of chest disease. CONCLUSION: An easy-to-use method is given to estimate diagnostic accuracy in the multiple abnormality setting. This should make it easier to incorporate cases with multiple abnormalities when assessing the diagnostic accuracy of imaging systems.     

Observer performance comparison of digital radiograph systems for stereotactic breast needle biopsy

RATIONALE AND OBJECTIVES: Two digital radiograph systems for stereotactic mammography, one using a lens to couple a Lanex Regular screen to a back-illuminated charge-coupled device (CCD) and one using a fiber-optic taper to couple a Min-R Regular-type screen to a front-illuminated CCD, were evaluated with respect to observer performance. METHODS: A contrast-detail phantom was imaged in a variety of equivalent exposure conditions on both systems. Six observers viewed images on a video monitor and recorded which objects were detected. RESULTS: Performance (percent correct detections) with the lens-coupled system using the Lanex Regular screen was significantly higher than with the fiber-optic-coupled system using the Min-R Regular-type screen. CONCLUSION: Differences in absorption efficiencies of phosphors used, as well as differences in design of the two cameras, can explain differences in observer detection performance.     

Acute varicella hepatitis in human T-cell lymphotrophic virus types I and II infection

The delayed-gamma neutron activation facility at Brookhaven National Laboratory was originally calibrated using an anthropomorphic hollow phantom filled with solutions containing predetermined amounts of Ca. However, 99% of the total Ca in the human body is not homogeneously distributed but contained within the skeleton. Recently, an artificial skeleton was designed, constructed, and placed in a bottle phantom to better represent the Ca distribution in the human body. Neutron activation measurements of an anthropomorphic and a bottle (with no skeleton) phantom demonstrate that the difference in size and shape between the two phantoms changes the total body calcium results by less than 1%. To test the artificial skeleton, two small polyethylene jerry-can phantoms were made, one with a femur from a cadaver and one with an artificial bone in exactly the same geometry. The femur was ashed following the neutron activation measurements for chemical analysis of Ca. Results indicate that the artificial bone closely simulates the real bone in neutron activation analysis and provides accurate calibration for Ca measurements. Therefore, the calibration of the delayed-gamma neutron activation system is now based on the new bottle phantom containing an artificial skeleton. This change has improved the accuracy of measurement for total body calcium. Also, the simple geometry of this phantom and the artificial skeleton allows us to simulate the neutron activation process using a Monte Carlo code, which enables us to calibrate the system for human subjects larger and smaller than the phantoms used as standards.     

A bimetal anode with tungsten or rhodium? Comparative studies on image quality and dosage requirement in mammography

PURPOSE: The impact of different anode materials (tungsten and rhodium) on spatial resolution, image contrast and radiation exposure was studied. MATERIALS AND METHODS: Two mammographic systems providing bimetal x-ray tubes (Mo/W and Mo/Rh) were compared by imaging a breast radiography phantom with additional acrylic plates from 3 to 8 cm thickness. Spatial resolution was evaluated using a line bar pattern. Image contrast was assessed by measuring the ratio of optical densities in a acrylic step-wedge. The entrance dose was measured with a low energy ionisation chamber. RESULTS: The spatial resolution was about 13 lp/mm regardless of the beam quality. The image contrast depended substantially on the thickness. A similar image contrast was found with Mo/Mo, Mo/Rh and Rh/Rh for simulated breast thicknesses of 4 to 6 cm and with Rh/Rh and W/Rh for 7 cm. In comparison to Mo/Mo the dose reduction was significant for Mo/Rh (35%), Rh/Rh (50%) and W/Rh (60%). CONCLUSIONS: Bimetal x-ray tubes provide optimal conditions for screen film mammography of both normal and dense breasts, allowing good contrast and dose reduction by using the adequate anode/filter-combination.     

Nocturnal variation in human sympathetic baroreflex sensitivity

INTRODUCTION: The differential diagnosis of malignancy in small foci of microcalcifications or in extremely small nodes can be difficult. We carried out a retrospective analysis of integrated mammographic and US results, correlated with histologic data, to assess the limitations of each method and to optimize and benign/malignant ratio. MATERIALS AND METHODS: Our series consisted of 485 nonpalpable breast lesions submitted to histologic examination after vegetable charcoal marking. We gave each lesion an 0-5 score according to the degree of diagnostic doubt/suspicion after mammography and US, which results were correlated with histologic data to assess the carcinoma frequency in the various groups identified. RESULTS: The analysis of mammographic and US images showed that the most frequent mammographic alteration in the lesions submitted to biopsy was an isolated cluster of microcalcifications (40.99%): of these, 36.86% were neoplastic. The nodules submitted to biopsy, which were 29.81% of the total, showed a cancer rate (36.80%) very similar to that of the microcalcifications. The carcinoma rate rose to 37.93% when the microcalcifications were associated with nodes. The highest carcinoma rates, i.e., 52.94% and 66.66%, respectively, were found in parenchymal distortions, either isolated or associated with microcalcifications, which however were only 7.03% and 3.10%, respectively, of the total number of cases. DISCUSSION AND CONCLUSIONS: Our study showed that: 1) a highly suspicious US result must be seriously considered when a negative mammography has poor intrinsic contrast; 2) a highly suspicious US image with a little suspicious good contrast mammography requires further confirmation before surgery is planned; 3) when the mammographic finding is mid-to-highly suspicious, further investigations are needed even if US is negative. To conclude, even though the histologic examination of nonpalpable breast lesions involves performing a biopsy, we believe this is acceptable when performed on an outpatient basis, under local anesthesia and removing a limited amount of tissue only. The benign/malignant ratio ranges 2 to 1.5: if it is further reduced (below 1.5), there will be the risk of missing some early neoplastic lesions.