High-resolution MR imaging of the breast: clinical context

Preliminary investigation into magnetic resonance (MR) imaging as a breast imaging technique has demonstrated several promising roles for this modality when used as an adjunct to mammography for the detection and diagnosis of breast cancer. There are many technical factors that must be considered, including high resolution, rapid imaging, fat suppression, and localization and biopsy capability. Potential clinical applications include differentiating benign from malignant lesions, detecting cancer when results of clinical examination or conventional imaging are equivocal, detecting cancer recurrence after breast conservation treatment, staging newly diagnosed breast cancer, and detecting occult cancer in patients presenting with axillary node metastasis. Pitfalls include false-positive and false-negative results. Awareness of the strengths and limitations of MR imaging of the breast will facilitate integration of this technique into the work-up of patients with suspicious breast lesions.

Effect of human variability on independent double reading in screening mammography

RATIONALE AND OBJECTIVES

To demonstrate the range of gains and losses that radiologists might experience from independent double reading in screening mammography.

METHODS

From a national random sample of radiologists, the authors formed 131 pairs. For each radiologist, the authors analyzed the increase relative to his or her individual true-positive rate (TPR) or false-positive rate (FPR), number of additional cancers detected, and change to negative biopsy rate that would result from independent double reading after pairing.

RESULTS

The average radiologist can expect an 8%-14% gain in TPR and a 4%-10% increase in FPR with pairing. For some radiologists, double reading increased the TPR with a small concomitant increase in FPR. Other radiologists, however, realized small gains in TPR with large increases in FPR. Adding the reading from a more experienced radiologist did not necessarily improve the TPR of a radiologist with less experience.

CONCLUSION

Radiologists can form complementary and noncomplementary pairs for double reading. Use of this procedure must be decided on an individual basis.

Variability in the interpretation of screening mammograms by US radiologists. Findings from a national sample

OBJECTIVE

To evaluate the effectiveness of screening mammography by estimating the variability in radiologists' ability to detect breast cancer within the US population of radiologists at mammography centers accredited by the American College of Radiology.

METHODS

A two-way sample survey design was used as follows. Fifty mammography centers having an American College of Radiology-accredited unit were randomly sampled from across the United States. One hundred eight radiologists from these centers gave blinded interpretation to the same set of 79 randomly selected screening mammograms. The mammograms were from women who had been screened at a large screening center. Before their sampling, these women had been stratified by their breast disease status, established either by biopsy or by 2-year follow-up. Rates of biopsy recommendations were summarized by the mean, median, minimum, maximum, and range of sensitivity and specificity. Overall cancer detection ability was summarized by similar statistics for receiver operating characteristic curve areas. Ninety-five percent lower confidence bounds on the ranges in accuracy measures were established by boo-strapping.

RESULTS

There is a range of at least 40% among US radiologists in their screening sensitivity. There is a range of at least 45% in the rates at which women without breast cancer are recommended for biopsy. As indicated by receiver operating characteristic curve areas, the ability of radiologists to detect cancer mammograms varies by as much as 11%.

CONCLUSIONS

Our findings indicate that there is wide variability in the accuracy of mammogram interpretation in the population of US radiologists. Current accreditation programs that certify the technical quality of radiographic equipment and images but not the accuracy of the interpretation given to mammograms may not be sufficient to help mammography fully realize its potential to reduce breast cancer mortality.

Periprosthetic mycobacterial infection. CT and mammographic findings

Organisms of the Mycobacterium fortuitum complex are an uncommon but important cause of periprosthetic infection following augmentation mammoplasty or other breast surgery. This etiological agent must be considered in the particular case of periprosthetic infection, because special handling of the fluid is crucial to enhance recovery of the organism. We describe the computed tomography (CT) and mammographic findings in such an abscess with respect to the clinical context and subsequent management. To our knowledge, CT findings associated with any periprosthetic breast infection have not been described.

Seromas in residual fibrous capsules after explantation: mammographic and sonographic appearances

PURPOSE

To evaluate the mammographic and sonographic findings associated with seromas that develop in residual fibrous capsules after explantation of breast prostheses.

MATERIALS AND METHODS

Preoperative and postoperative mammograms were reviewed in 86 patients (mean age, 51 years; age range, 24-71 years) who had undergone surgical explantation of breast prostheses. Six seromas were found in four patients 46-68 years of age. Imaging findings were correlated with surgical and laboratory results for three seromas. A presumptive diagnosis was made of the other three lesions.

RESULTS

Mammograms demonstrated all seromas as large, elliptic, water-opacity masses, some with well-circumscribed and some with irregular borders. Sonograms showed thin, compressible masses, two of which were flat and anechoic and one of which was hypoechoic. Three patients' images were initially misinterpreted, leading to excision of two seromas and aspiration of one. Seromas were not identified in patients whose implants were removed by means of complete capsulectomy.

CONCLUSION

Radiologists must be aware of the imaging findings associated with seromas and of a patient's surgical history to avoid biopsy of benign lesions.

Prediction of breast cancer malignancy using an artificial neural network

BACKGROUND

An artificial neural network (ANN) was developed to predict breast cancer from mammographic findings. This network was evaluated in a retrospective study.

METHODS

For a set of patients who were scheduled for biopsy, radiologists interpreted the mammograms and provided data on eight mammographic findings as part of the standard mammographic workup. These findings were encoded as features for an ANN. Results of biopsies were taken as truth in the diagnosis of malignancy. The ANN was trained and evaluated using a jackknife sampling on a set of 260 patient records. Performance of the network was evaluated in terms of sensitivity and specificity over a range of decision thresholds and was expressed as a receiver operating characteristic curve.

RESULTS

The ANN performed more accurately than the radiologists (P < 0.08) with a relative sensitivity of 1.0 and specificity of 0.59.

CONCLUSIONS

An ANN can be trained to predict malignancy from mammographic findings with a high degree of accuracy.

Needle core biopsy of mammographic lesions

Needle core biopsy and fine-needle aspiration cytology (FNAC) provide histologic diagnoses in a wide variety of clinical settings. In breast disease, surgeons have used these techniques to evaluate palpable masses for many years. In recent years, radiologists have used image-guided adaptations of these two techniques to evaluate mammographically detected lesions.

Impact of patient-controlled compression on the mammography experience

The authors tested the hypothesis that giving women control over the compression portion of the mammography examination results in a less painful experience, greater overall patient satisfaction, and a radiographic image as good as that produced by means of technologist-controlled compression. One hundred nine women undergoing screening mammography at a hospital-based outpatient clinic were studied. Each underwent two-view, screen-film mammography performed in routine fashion except that, by random assignment, one breast was compressed by the technologist and the other breast, by the patient. Patient-controlled compression was significantly (P = .003) less painful than technologist-controlled compression. Overall patient satisfaction (96% [105 of 109]) and willingness to repeat the experience were extremely high. The majority of images (93.5% [202 of 216]) were rated as having good to excellent compression. With minimal patient education, self-compression resulted in an image at least as good as that produced with technologist-applied compression. Further study of this technique is warranted.

The natural history of mammographic calcifications subjected to interval follow-up

The purpose of this investigation was to determine the natural history and risk of malignancy associated with isolated indeterminate microcalcifications subjected to interval follow-up. During a 2-year study, 91 patients were identified with indeterminate microcalcifications alone. Specific roentgenographic features of the calcifications were evaluated on initial and follow-up mammograms. During a mean follow-up of 36 months, 19 (21%) of the women exhibited mammographic changes. Ten patients (11%) with suspicious changes underwent a needle-directed biopsy 6 to 30 months after the initial mammographic screening. Five women (5.5%) were diagnosed as having breast carcinoma; three had invasive ductal carcinoma and two had purely intraductal lesions. Four patients had axillary lymph node dissections and no metastatic disease was found. We found no significant differences in the roentgenographic features associated with malignant vs benign lesions apart from an increased overall estimation of the probability of malignancy rating in the five patients with breast carcinoma. We recommend that patients be followed up with mammography at regular intervals for at least 18 months following recognition of indeterminate microcalcifications.

Two dimensional ultrasonic beam distortion in the breast: in vivo measurements and effects

Two dimensional arrival time data was obtained for the propagation of ultrasound across the breasts of 7 female volunteers. These profiles were extracted through the use of cross-correlation measurements and a simulated annealing process that maintained phase closure while aligning the data. The phase aberration measured in two dimensions had a larger magnitude than previously reported phase aberration measured in one dimension in the breast. A point spread function generation computer program was used to demonstrate the system response degrading effects of the measured phase aberration and the usefulness of current one dimensional phase aberration correction techniques. The results indicate that two dimensional correction algorithms are necessary to restore the system performance losses due to phase aberration.

Measurement of force applied during mammography

The discomfort that patients experience during mammography is probably related to a variety of factors, one of which might be the amount of compression used. The authors measured the amount of force applied to the breasts during mammography and the resulting breast thickness in 560 women and correlated these measurements with the patient's subjective impression of the examination. The amount of force applied ranged from 49 to 186.2 N (median, 122.5 N). Breast thickness ranged from 10 to 88 mm (median, 46.5 mm). Forty-seven women (8%) rated the examination as painful (ie, mammography was either "very uncomfortable" or "intolerable"). Logistic regression analysis revealed a highly significant relationship between probability of a painful response and ratio of force to thickness (P = .007). Current guidelines suggest that maximum available force be at least 160 N but not more than 200 N. However, because increasing force is associated with increasing likelihood of pain, technologists should be aware that these recommended maximum limits are not intended to be used routinely for all women. In this study, high-quality mammograms were obtained in a majority of women with forces less than the maximum available level.

The impact of acoustic velocity variations on target detectability in ultrasonic images of the breast

Experimentally obtained ultrasonic phase aberration profiles in the breast were used to investigate the impact of acoustic velocity variations on images of simulated breast lesions. The imaging properties of several phased-array transducers with varying frequencies and geometries were studied as phase error profiles of increasing magnitude were introduced. The targets studied were anechoic lesions of various sizes. The results indicate that phase aberrations significantly degrade the contrast of ultrasonic breast images, especially for high-resolution scanning systems.

Positron emission tomography in neuropsychiatry

Positron emission tomography (PET) allows high-resolution, three-dimensional evaluation of regional brain metabolic activity and neurotransmitter function. This imaging technique has been applied increasingly in psychiatric research and may yield new information regarding the neural mechanisms of several mental disorders. This article is an overview of PET studies conducted on schizophrenia, affective disorders, and anxiety disorders. Although this research is in the preliminary stage with some inconsistent findings, general trends have emerged that clearly warrant further investigation. These trends are discussed in light of relevant methodological and theoretical issues. Potential directions for future PET research are reviewed.

In vivo measurements of ultrasonic beam distortion in the breast

The phase aberrations encountered by ultrasonic pulses propagating through breast tissue in twenty-two female volunteers were measured. The experiments were designed to assess the impact of these aberrations on clinical ultrasonic image quality for a variety of transducer and imaging geometries. The phase aberration profiles of a given patient were correlated with the amount of parenchymal tissue determined from that patient's mammogram. These data are useful in assessing the image quality achievable with conventional ultrasonic imaging systems, and the potential application of adaptive ultrasonic imaging systems. The results indicate that phase aberrations significantly degrade breast image quality for typical transducer frequencies and sizes.

Evaluation of acute renal failure with magnetic resonance imaging using gradient-echo and Gd-DTPA

Detection of acute renal failure (ARF) using fast-scan magnetic resonance imaging (MRI) with Gd-DTPA was studied in a dog model. ARF was produced in five dogs by infusion of norepinephrine (0.75 micrograms/kg/min) into the renal arteries for 40 minutes. MRI was performed 1 hour later and compared with baseline (pre-ARF) MRI. There was no significant difference in the ratios of signal intensity-vs.-time curves from 0 to 35 seconds after injection of Gd-DTPA. However, a difference between the outer and inner medulla was significant in the time period of 5 to 20 minutes after Gd-DTPA injection. These later signal intensity differences by fast-scan (gradient-echo) technique may be useful in the evaluation of ARF.

Temporal regulation of equine herpesvirus type 3 transcription

The transcription of equine herpesvirus type 3 (EHV-3; equine coital exanthema virus) has been examined and found to be temporally regulated into three classes: immediate early (IE), early (E), and late (L). Hybridization of in vivo 32PO4-labeled transcripts revealed that IE transcript(s) are derived exclusively from the inverted repeat segments (IRs) of the viral genome, while E and L transcripts are not restricted to any specific region of the genome. Northern blot analysis of EHV-3 IE RNA revealed a single transcript of approximately 5.7 kb (3.8 MDa). We have previously shown that transcription of equine herpesvirus type 1 (EHV-1) DNA is temporally regulated and produces a single 6 kb IE RNA which is derived from the IRs segments. In this paper, we show that the EHV-1 and EHV-3 IE RNA species are homologous, reflecting the colinearity of the genomes of these two related viruses. While four IE polypeptides are synthesized in EHV-1 infected cells in the presence of actinomycin D following the removal of a cycloheximide block, only one major IE polypeptide (180 kDa) is detectable in EHV-3 infected cells under these conditions. However, immunoprecipitation of EHV-3 infected cell extracts with polyvalent rabbit antisera to IE1 of EHV-1 revealed at least two other viral specific IE polypeptides.

Synthesis and processing of equine herpesvirus type 1 glycoprotein 14

Glycoprotein 14 (gp14) of equine herpesvirus type 1 (EHV-1), the homolog of herpes simplex virus (HSV) glycoprotein B (gB), was investigated employing a panel of monoclonal antibodies to ascertain the regulatory class, rate of synthesis, and type of glycosylation of this polypeptide. Application of immunoprecipitation, Western blot, and SDS-PAGE analysis in conjunction with the use of metabolic inhibitors (cycloheximide, antinomycin D, phosphonoacetic acid, tunicamycin, and monensin), and time-course and pulse-chase experiments revealed the following information: (1) Three gp14-related polypeptides with molecular weights of 138 kilodaltons (K), 77-75K, and 55-53K are present in EHV-1-infected cell extracts. (2) All three species are synthesized in the presence of the DNA synthesis inhibitor phosphonoacetic acid although their synthesis is enhanced by DNA replication, indicative of a beta-gamma class molecule. (3) The 138K species is synthesized first as a precursor of the smaller species of gp14, the 77-75K and 55-53K forms. (4) Use of glycosylation inhibitors and digestion of immunoprecipitated gp14 with endoglycosidases indicate that the primary translation product is a 118K molecule which is cotranslationally glycosylated to the 138K form by the addition of high mannose oligosaccharides. (5) The 77-75K species contains both high mannose and hybrid oligosaccharides while the 55-53K form of gp14 contains some complex oligosaccharides. (6) In the absence of a reducing agent, the 138K polypeptide and a large 145K species are observed in both infected cell extracts and purified virions. Thus, EHV-1 gp14 appears to be synthesized as a large precursor molecule of 138K and is proteolytically cleaved to two smaller forms, 77-75K and 55-53K, which are linked by a disulfide bond(s) to form a 145K complex. This model of gp14 synthesis and maturation is similar to those proposed for a number of HSV gB equivalents found in the Alphaherpesvirnae.

Breast skin calcifications: localization with a stereotactic device

Calcifications that lie within the skin of the breast may be mistakenly thought to be intraparenchymal on mammograms if they are projected over breast tissue in two views. A simple, reliable technique was developed to determine calcification location. It uses a commercially available stereotactic localization device and has been used successfully in six patients.

Nonpalpable breast lesions at biopsy. A detailed analysis of radiographic features

Several studies have demonstrated that mammographic screening of asymptomatic women results in a lower mortality rate where breast cancer is concerned. Often, screening mammograms reveal a nonpalpable radiographic abnormality and the diagnosis must be determined by an excisional biopsy after radiographic needle localization. The mammographic features associated with 179 nonpalpable breast abnormalities biopsied after radiographic needle localization were carefully characterized. There were 41 carcinomas (23%) in the series. The aim of this study was to determine which radiographic findings, if any, strongly portend the presence of either a malignant or benign lesion. Mammographic features that were commonly associated with malignancy include a change from a previous mammogram, a distortion of the surrounding architecture, the association of a soft tissue density and calcifications, and the presence of more than ten calcifications in the lesion. The radiographic abnormalities which were more commonly associated with benign disease include well-defined densities without calcifications, asymmetric densities without calcifications, and abnormalities consisting solely of a focus of mammographic calcifications that have fewer than ten concretions. The incidence of malignancy in lesions having these mammographic characteristics was only 5.5%. On the basis of these results alone, no firm threshold for biopsy can be recommended. The risks of deferring biopsy until there is worsening of the mammographic image remains to be determined.

Effects of ECT on brain structure: a pilot prospective magnetic resonance imaging study

The authors describe a pilot prospective investigation of the effects of ECT on brain structure using magnetic resonance imaging (MRI). In nine patients with major depression, a course of ECT produced no acute changes in brain structure according to blind raters' assessments of cortical atrophy and global comparison of pre- and post-ECT studies. There were also no significant changes in the ventricle-brain ratios. Pre-ECT brain abnormalities were common in these patients yet were also unaffected by ECT. Future MRI studies of ECT should include more subjects and should address long-term changes and subtle brain abnormalities.