Simulated lesion, human observer performance comparison between thin-section dedicated breast CT images versus computed thick-section simulated projection images of the breast.

The objective of this study was to compare the lesion detection performance of human observers between thin-section computed tomography images of the breast, with thick-section (>40 mm) simulated projection images of the breast. Three radiologists and six physicists each executed a two alterative force choice (2AFC) study involving simulated spherical lesions placed mathematically into breast images produced on a prototype dedicated breast CT scanner. The breast image data sets from 88 patients were used to create 352 pairs of image data. Spherical lesions with diameters of 1, 2, 3, 5, and 11 mm were simulated and adaptively positioned into 3D breast CT image data sets; the native thin section (0.33 mm) images were averaged to produce images with different slice thicknesses; average section thicknesses of 0.33, 0.71, 1.5 and 2.9 mm were representative of breast CT; the average 43 mm slice thickness served to simulate simulated projection images of the breast.The percent correct of the human observer's responses were evaluated in the 2AFC experiments. Radiologists lesion detection performance was significantly (p < 0.05) better in the case of thin-section images, compared to thick section images similar to mammography, for all but the 1 mm lesion diameter lesions. For example, the average of three radiologist's performance for 3 mm diameter lesions was 92% correct for thin section breast CT images while it was 67% for the simulated projection images. A gradual reduction in observer performance was observed as the section thickness increased beyond about 1 mm. While a performance difference based on breast density was seen in both breast CT and the projection image results, the average radiologist performance using breast CT images in dense breasts outperformed the performance using simulated projection images in fatty breasts for all lesion diameters except 11 mm. The average radiologist performance outperformed that of the average physicist observer, however trends in performance were similar. Human observers demonstrate significantly better mass-lesion detection performance on thin-section CT images of the breast, compared to thick-section simulated projection images of the breast.

Automated detection of mass lesions in dedicated breast CT: a preliminary study.

PURPOSE: To develop an automated method to detect breast masses on dedicated breast CT (BCT) volumes and to conduct a preliminary evaluation of its performance. This method can be used in a computer-aided detection (CADe) system for noncontrast enhanced BCT. METHODS: The database included patient images, which were acquired under an IRB-approved protocol. The database in this study consisted of 132 cases. 50 cases contained 58 malignant masses, and 23 cases contained 24 benign masses. 59 cases did not contain any biopsy-proven lesions. Each case consisted of an unenhanced CT volume of a single breast. First, each breast was segmented into adipose and glandular tissues using a fuzzy c-means clustering algorithm. The glandular breast regions were then sampled at a resolution of 2 mm. At each sampling step, a 3.5-cm(3) volume-of-interest was subjected to constrained region segmentation and 17 characteristic features were extracted, yielding 17 corresponding feature volumes. Four features were selected using step-wise feature selection and merged with linear discriminant analysis trained in the task of distinguishing between normal breast glandular regions and masses. Detection performance was measured using free-response receiver operating characteristic analysis (FROC) with leave-one-case-out evaluation. RESULTS: The feature selection stage selected features that characterized the shape and margin strength of the segmented region. CADe sensitivity per case was 84% (std = 4.2%) at 2.6 (std = 0.06) false positives per volume, or 6 × 10(-3) per slice (at an average of 424 slices per volume in this data set). CONCLUSIONS: This preliminary study demonstrates the feasibility of our approach for CADe for BCT.

Cassette-based digital mammography.

Over the past several years, digital mammography systems have been installed clinically across North America in small but growing numbers. A photostimulable phosphor-based full-field digital mammography image was evaluated in this investigation. Commonly known as computed radiography (CR), its use closely mimics the screen-film mammography paradigm. System performance using modulation transfer function (MTF) and detective quantum efficiency (DQE) metrics show MTF(2.5 mm(-1)) = 0.5, DQE(2.5 mm(-1)) = 0.3, and MTF(5.0 mm(-1)) = 0.2, DQE(5.0 mm(-1)) = 0.05, for a 26 kVp beam, 0.03 mm molybdenum tube filtration, 4.5 cm tissue attenuation, and 15 mR incident exposure to the detector. Slightly higher DQE values were measured at 32 kVp with 0.025 mm rhodium tube filtration. CR mammography advantages include the ability to use existing mammography machines, where multiple rooms can be converted to "digital" operation, which allows overall cost savings compared to integrated digital mammography systems. Chief disadvantages include the labor-intensive handling of the cassettes prior to and after the imaging exam, lack of a direct interface to the x-ray system for recording technique parameters, and relatively slow processing time. Clinical experience in an IRB-approved research trial has suggested that digital mammography with photostimulable storage phosphors and a dedicated CR reader is a viable alternative to conventional screen-film mammography.

Dedicated breast CT: radiation dose and image quality evaluation.

PURPOSE: To evaluate the feasibility of breast computed tomography (CT) in terms of radiation dose and image quality. MATERIALS AND METHODS: Validated Monte Carlo simulation techniques were used to estimate the average glandular dose (AGD). The calculated photon fluence at the detector for high-quality abdominal CT (120 kVp, 300 mAs, 5-mm section thickness) was the benchmark for assessing the milliampere seconds and corresponding radiation dose necessary for breast CT. Image noise was measured by using a 10-cm-diameter cylinder imaged with a clinical CT scanner at 10-300 mAs for 80, 100, and 120 kVp. A cadaveric breast was imaged in the coronal plane to approximate the acquisition geometry of a proposed breast CT scanner. RESULTS: The AGD for 80-kVp breast CT was comparable to that for two-view mammography of 5-cm breasts (compressed breast thickness). For thicker breasts, the breast CT dose was about one-third less than that for two-view mammography. The maximum dose at mammography assessed in 1-mm(3) voxels was far higher (20.0 mGy) than that at breast CT (5.4 mGy) for a typical 5-cm 50% glandular breast. CT images of an 8-cm cadaveric breast (AGD, 6.3 mGy) were subjectively superior to digital mammograms (AGD, 10.1 mGy) of the same specimen. CONCLUSION: The potential of high signal-to-noise ratio images with low anatomic noise, which are obtainable at dose levels comparable to those for mammography, suggests that dedicated breast CT should be studied further for its potential in breast cancer screening and diagnosis.

False-positive screening mammograms: effect of immediate versus later work-up on patient stress.

PURPOSE: To compare the stress experienced by women who had false-positive screening mammograms and had undergone immediate on-site diagnostic imaging evaluation with that experienced by those who had been recalled for subsequent imaging. MATERIALS AND METHODS: A retrospective survey was mailed to women with false-positive screening mammograms that had proved negative or benign at diagnostic imaging. The women were divided into (a) those who had undergone diagnostic imaging during the same appointment as their screening examination and (b) those who had returned at a later date for work-up. The survey included questions about stress that was related to the screening and diagnostic experiences, how subjects had been notified about screening results, and their breast health histories. RESULTS: From the group that had undergone immediate work-up (n = 100), 50 eligible surveys were received; 71 were received from women who had undergone later work-ups (n = 176). The self-reported overall stress was significantly greater (P =.027) in the group recalled for subsequent diagnostic imaging. Among all respondents, stress from a false-positive screening result was greatest in women younger than 50 years of age with a positive first-degree family history of breast cancer. CONCLUSION: Providing immediate on-site diagnostic evaluation can reduce the stress of a false-positive screening mammogram.

Scatter/primary in mammography: comprehensive results.

Monte Carlo procedures using the SIERRA code (validated in a companion article) were used to investigate the scatter properties in mammography. The scatter to primary ratio (SPR) was used for quantifying scatter levels as a function of beam spectrum, position in the field, air gap, breast thickness, tissue composition, and the area of the field of view (FOV). The geometry of slot scan mammography was also simulated, and SPR values were calculated as a function of slot width. The influence of large air gaps (to 30 cm) was also studied in the context of magnification mammography. X-ray energy and tissue composition from 100% adipose to 100% glandular demonstrated little effect on the SPR. Air gaps over a range from 0 to 30 mm showed only slight effects. The SPR increased with increased breast thickness and with larger fields of view. Measurements from 82 mammograms provided estimates of the range of compressed breast thickness (median: 5.2 cm, 95% range: 2.4 cm to 7.9 cm) and projected breast area onto the film (left craniocaudal view, median: 146 cm2, 95% range: 58 cm2 to 298 cm2). SPR values for semicircular breast shapes, Mo/Mo spectra, and a 15 mm air gap were parametrized as a function of breast thickness and (semicircular) breast diameter. With the coefficients a = - 2.35452817439093, b = 22.3960980055927, and c = 8.85064260299289, the equation SPR= [a + b x (diameter in cm)--(-1.5) + c x (thickness in cm) --(-0.5)]-- -1 produces SPR data from 2 to 8 cm and from 3 to 30 cm breast diameters with an average error of about 1%.

A breast density index for digital mammograms based on radiologists' ranking.

The purpose of this study was to develop and evaluate a computerized method of calculating a breast density index (BDI) from digitized mammograms that was designed specifically to model radiologists' perception of breast density. A set of 153 pairs of digitized mammograms (cranio-caudal, CC, and mediolateral oblique, MLO, views) were acquired and preprocessed to reduce detector biases. The sets of mammograms were ordered on an ordinal scale (a scale based only on relative rank-ordering) by two radiologists, and a cardinal (an absolute numerical score) BDI value was calculated from the ordinal ranks. The images were also assigned cardinal BDI values by the radiologists in a subsequent session. Six mathematical features (including fractal dimension and others) were calculated from the digital mammograms, and were used in conjunction with single value decomposition and multiple linear regression to calculate a computerized BDI. The linear correlation coefficient between different ordinal ranking sessions were as follows: intraradiologist intraprojection (CC/CC): r = 0.978; intraradiologist interprojection (CC/MLO): r = 0.960; and interradiologist intraprojection (CC/CC): r = 0.968. A separate breast density index was derived from three separate ordinal rankings by one radiologist (two with CC views, one with the MLO view). The computer derived BDI had a correlation coefficient (r) of 0.907 with the radiologists' ordinal BDI. A comparison between radiologists using a cardinal scoring system (which is closest to how radiologists actually evaluate breast density) showed r = 0.914. A breast density index calculated by a computer but modeled after radiologist perception of breast density may be valuable in objectively measuring breast density. Such a metric may prove valuable in numerous areas, including breast cancer risk assessment and in evaluating screening techniques specifically designed to improve imaging of the dense breast.

Short-interval follow-up mammography versus immediate core biopsy of benign breast lesions: assessment of patient stress.

OBJECTIVE: The stress experienced by women undergoing surveillance mammography for benign lesions was compared with that experienced by women undergoing core biopsy of benign lesions. MATERIALS AND METHODS: A retrospective survey was mailed to women in whom were diagnosed breast abnormalities that were likely to be benign and that were stable at short-interval follow-up mammography (n = 174) or in whom a core biopsy of the breast was performed, with benign findings (n = 116). The survey included questions about stress related to the diagnostic experience as well as questions about who advised the women of the results of their breast imaging studies and about the information provided. RESULTS: Eighty eligible surveys were received from the women who underwent short-interval follow-up mammography, and 58 surveys were received from the women who underwent biopsies. The self-reported overall stress experienced by the women who underwent core biopsies was significantly greater (p < .001) than that reported by the group who were followed up with mammography. The level of anxiety was not affected by the patient's perception of the probability that the lesion represented carcinoma. We found no significant differences in stress between women who discussed their mammogram results with a radiologist and women who were notified by their primary care provider. CONCLUSION: Short-interval follow-up mammography continues to be acceptable for the evaluation of lesions that are probably benign, even when patient anxiety is considered.

Screening mammography beginning at age 40 years: a reappraisal of cost-effectiveness.

BACKGROUND: Several recent studies have added significant information regarding the benefit of screening mammography, especially in the 40-49-years age group. This new information makes it important to reassess the cost-effectiveness of screening. METHODS: A Markov model was used to study the cost-effectiveness of 4 age-related screening strategies: 1) annually from ages 40-79 years; 2) annually from ages 40-64 years and biennially from ages 65-79 years; 3) annually from ages 40-49 years and biennially from ages 50-79 years; and 4) annually from ages 40-79 years in high risk women (10%) and biennially from ages 40-49 years followed by annually from ages 50 -79 years in normal risk women (90%). An additional strategy simulating hormone status and estrogen exposure was evaluated. Cost-effectiveness was expressed as marginal cost per year-life saved (MCYLS). RESULTS: The MCYLS varied from $18,800 to $16,100. For all strategies this was within the range of other generally acceptable diagnostic and therapeutic medical procedures. There was a 14% decrease in MCYLS from the least cost-effective to the most cost-effective strategy. CONCLUSIONS: Cost-effectiveness of four age-related mammographic screening strategies was evaluated. The MCYLS for all strategies was within a generally accepted range. With increasing concerns regarding the cost of health care, this information may be useful in health policy decision-making.

The cost-effectiveness of mammographic screening strategies.

OBJECTIVE: To compare and analyze the cost-effectiveness of different mammographic screening strategies. DESIGN: A computer simulation model was developed to compare mammographic screening with observation without screening. Cost-effectiveness was expressed as marginal cost per year of life saved (MCYLS) and was calculated for the following mammographic screening strategies: (1) annual for ages 40 to 79 years; (2) annual for ages 50 to 79 years; (3) biennial for ages 50 to 79 years; (4) annual for ages 40 to 49 years with biennial for ages 50 to 79 years; (5) annual for ages 40 to 64 years with biennial for ages 65 to 79 years; (6) biennial for ages 40 to 49 years with annual for ages 50 to 79 years; and (7) annual for high-risk and biennial for normal-risk women aged 40 to 49 years with annual for ages 50 to 79 years. DATA SOURCES: The probability and cost of all outcomes were established from previously published data or community experience. RESULTS: The most cost-effective screening strategy is biennial mammography for women aged 50 to 79 years, with an MCYLS of $16,000. Adding annual mammography for women aged 40 to 49 years increases the MCYLS to $20,200, but is more cost-effective than other tested protocols that included women in their 40s; annual mammography for ages 40 to 49 years with biennial for ages 50 to 79 years is also more cost-effective than annual mammography for ages 50 to 79 years. CONCLUSION: Screening programs that include women in their 40s can be as cost-effective as some that exclude such women. Choice of a screening strategy depends on financial resources and desired effectiveness.

Screening mammography in women aged 40-49 years: analysis of cost-effectiveness.

PURPOSE: To evaluate the cost-effectiveness of screening mammography in women 40-49 years old. MATERIALS AND METHODS: A Markov model compared two hypothetical groups; one underwent screening mammography and the other, observation without mammography. Variables tested included frequency of mammography, reduction in breast cancer mortality, and cost-effectiveness by age group. Results were expressed as marginal cost per year of life saved. RESULTS: If the estimated mortality reduction from mammographic screening was 15% or greater, the marginal cost per year of life saved was comparable to that of other generally accepted medical procedures. Annual screening with an assumed 30% reduction in mortality had a cost-effectiveness similar to that of biennial screening with a 20% reduction. Screening mammography was less cost-effective in the 40-49-year-old age group than in women aged 50-79 years but more cost-effective than in those aged 80-84 years. CONCLUSION: Although the parameters for screening mammography in women aged 40-49 years are not known with certainty, the results of this analysis may help establish priorities for utilization of medical resources.

Needle core biopsy guided with mammography: a study of cost-effectiveness.

PURPOSE: To analyze the cost-effectiveness of needle core biopsy (NCB) in a breast cancer screening program. MATERIALS AND METHODS: A computer model was used to compare two hypothetical groups of women: those who undergo annual mammographic screening and those observed without screening. All clinically significant outcomes for each group were included in the model, which reflected the state of a woman's health each year beginning at age 40 years and ending at age 85 years. RESULTS: The marginal cost per year of life saved by screening was reduced a maximum of 23% (from $20,770 to $15,934) with use of NCB instead of surgical biopsy. The cost of NCB had less effect on cost-effectiveness than the number of women who underwent NCB. CONCLUSION: When used for the same indications as surgical biopsy, NCB substantially reduces the cost of a breast cancer screening program.

Diuretic Doppler sonography following successful repair of renal obstruction in children.

The measurement of resistive index (RI = [peak systolic velocity--end diastolic velocity]/peak systolic velocity) by Doppler sonography has demonstrated variable reliability as an indicator of pediatric urinary obstruction. By modifying Doppler studies with the addition of furosemide (diuretic Doppler sonography), we previously found significant differences between 10 nonobstructed and 10 obstructed kidneys in children (median age 7 months). The obstructed kidneys have since undergone surgical repair, and postoperative reevaluation has been performed by diuretic Doppler sonography and diuretic renography. Diuretic Doppler sonography was performed on well hydrated catheterized patients, with resistive index measurement of the renal interlobar and arcuate arteries obtained before and 10 minutes after 1 mg./kg. furosemide infusion. Following surgical repair of obstruction all 10 kidneys had stable glomerular filtration rate with improved pelvic emptying times as demonstrated by half-time. Of 6 kidneys evaluated by diuretic Doppler sonography before 3 months 2 had resistive index levels greater than 75. Of the 9 kidneys measured at 3 months or more postoperatively all had resistive index values of less than 75, even after furosemide infusion (5 kidneys underwent repeat evaluation). In our study the previously demonstrated post-diuretic elevation of resistive index in pediatric urinary obstruction was eventually reversed following surgical repair. Diuretic Doppler sonography appears to be a promising noninvasive method for evaluating pediatric hydronephrosis, providing an alternative physiological parameter with which to measure renal obstruction.

Diuretic Doppler sonography in postnatal hydronephrosis.

Renal resistive indexes were measured by Doppler sonography in 12 children undergoing other standard diagnostic studies to evaluate hydronephrosis. Measurement of renal resistive indexes was modified by prior placement of a bladder catheter, oral hydration and administration of 1 mg./kg. furosemide after baseline measurement. Renal resistive indexes were again measured at 10 and 30 minutes after diuretic. While diuretic administration had no measurable influence on 10 nonobstructed kidneys, the elevated 10-minute post-diuretic renal resistive indexes recorded in 10 obstructed kidneys differed significantly from the indexes recorded in the nonobstructed group (p less than 0.001). The highest elevations in renal resistive indexes were recorded in nonpaired kidneys, which included 7 of the 10 kidneys in the obstructed group. In the 3 unilaterally obstructed kidneys the 10-minute post-diuretic renal resistive indexes did not differ significantly. However, renal resistive indexes in these kidneys increased at least 15% over baseline readings after diuretic administration. Diuretic Doppler sonography appears to be another useful method for differentiating functionally significant hydronephrosis from nonobstructive hydronephrosis in children.

The roles of ultrasonography and amniocentesis in evaluation of elevated maternal serum alpha-fetoprotein.

A total of 681 pregnant women were referred for evaluation of elevated maternal serum alpha-fetoprotein levels. Ultrasonographic examination yielded an explanation for the elevation of maternal serum alpha-fetoprotein in 42% of patients. Diagnoses made by ultrasonography included incorrect fetal dating, multiple gestation, fetal death, open neural tube defect, abdominal wall defect, placental abnormalities, cystic hygroma, renal anomalies, and oligohydramnios. Optimal prenatal diagnosis of fetal anomalies also requires the use of amniocentesis in many patients. Amniocentesis may be obviated if fetal dating is incorrect, if an unsuspected multiple gestation is discovered, or if there is a clear anomaly and the parents do not desire genetic counseling based on karyotype information. If the fetus appears normal, the ultrasonographic results are equivocal, or the parents desire more detailed genetic counseling when an anomaly is found by ultrasonography, then amniocentesis should be performed. Thirteen abnormalities were diagnosed by amniocentesis alone in this group.

Cytologic interpretation of fine-needle aspiration biopsies from clinically occult breast masses.

Fine-needle aspiration biopsy (FNAB) was performed on 39 occult breast masses of soft tissue density using standard mammographic guidance. All malignant tumors were diagnosed as either positive or suspicious for carcinoma, and there were no false-positive or false-suspicious diagnoses. These excellent results can be attributed to accurate cytologic interpretation based on consideration of problems unique to these lesions and the sampling method, such as scantier cellularity, potentially less confidence in needle placement, and the nature of the occult mass itself. The team approach between pathologist, radiologist, and clinician is emphasized.

The rediscovery of infant feeding formula with magnetic resonance imaging.

In six newborns, regular infant feeding formula given approximately one-half hour to four hours prior to MR examination, demonstrated a high intensity signal within the infant's stomach, small bowel, and colon. This effect was observed on both 0.5 Tesla and 1.5 Tesla magnets on T1 (SE TR/TE 433-600/20-25) and on T2 (SE TR/TE 1500/30-80) weighted images. Infant feeding formula has the potential to be used as an oral contrast agent for visualization of the newborn gastrointestinal tract. Chloral hydrate and other agents were also tested.