The impact of respiratory gating on improving volume measurement of murine lung tumors in micro-CT imaging

Small animal imaging has become essential in evaluating new cancer therapies as they are translated from the preclinical to clinical domain. However, preclinical imaging faces unique challenges that emphasize the gap between mouse and man. One example is the difference in breathing patterns and breath-holding ability, which can dramatically affect tumor burden assessment in lung tissue. As part of a co-clinical trial studying immunotherapy and radiotherapy in sarcomas, we are using micro-CT of the lungs to detect and measure metastases as a metric of disease progression. To effectively utilize metastatic disease detection as a metric of progression, we have addressed the impact of respiratory gating during micro-CT acquisition on improving lung tumor detection and volume quantitation. Accuracy and precision of lung tumor measurements with and without respiratory gating were studied by performing experiments with in vivo images, simulations, and a pocket phantom. When performing test-retest studies in vivo, the variance in volume calculations was 5.9% in gated images and 15.8% in non-gated images, compared to 2.9% in post-mortem images. Sensitivity of detection was examined in images with simulated tumors, demonstrating that reliable sensitivity (true positive rate (TPR) ≥ 90%) was achievable down to 1.0 mm3 lesions with respiratory gating, but was limited to ≥ 8.0 mm3 in non-gated images. Finally, a clinically-inspired "pocket phantom" was used during in vivo mouse scanning to aid in refining and assessing the gating protocols. Application of respiratory gating techniques reduced variance of repeated volume measurements and significantly improved the accuracy of tumor volume quantitation in vivo.

Induction of thrombospondin-1 partially mediates the anti-angiogenic activity of dexrazoxane

Background:

Considerable interest lies in the identification of novel anti-angiogenic compounds for cancer therapy. We have investigated whether dexrazoxane has anti-angiogenic properties and if so, the mechanism of the inhibition.

Methods:

The phenotypic effects of dexrazoxane on endothelial cell behaviour was investigated both in vitro using human umbilical vein endothelial cells (HUVECs) in cell proliferation, migration, cell cycle and aortic ring assays; and in vivo using the mouse angiogenesis subcutaneous sponge assay. Custom angiogenesis pathway microarrays were used to identify differentially expressed genes in endothelial cells after treatment with dexrazoxane vs a control. The differentially expressed genes were validated using real-time RT–PCR and western blotting; and the functional effect of one induced gene was confirmed using siRNA technology.

Results:

Treatment of endothelial cells with dexrazoxane resulted in a dose–response inhibition of cell growth lasting for up to 5 days after a single dose of the drug. Dexrazoxane was inhibitory in the aortic ring tube forming assay and strongly anti-angiogenic in vivo in the rodent subcutaneous sponge model. The anti-angiogenic effect in the sponge was seen after systemic injection into the tail vein as well as after direct injection of dexrazoxane into the sponge. Treatment of microvascular endothelial cells in vitro with subtoxic doses of dexrazoxane stimulated thrombospondin-1 (THBS-1) secretion. Knockdown of THBS-1 with siRNA removed the angiogenesis inhibition effect of dexrazoxane, which is consistent with the anti-angiogenic and vascular normalising properties of the drug being principally mediated by THBS-1.

Conclusion:

We show that dexrazoxane administered in small repeated doses is strongly anti-angiogenic and that this activity is mediated by induction of the anti-angiogenic THBS-1 in endothelial cells.

New molecular pathways in angiogenesis

Angiogenesis has developed into a major area of cancer research. Recently, several newly identified signalling pathways have been shown to play a role in both normal and pathological (including tumour) angiogenesis. Several of the molecules involved in these pathways have potential as novel anti-cancer therapeutic targets including members of the ephrin/Eph receptor, Notch/delta, sprouty, hedgehog and roundabout/slit families. These developments are reviewed.

National Cancer Institute initiative: Lung image database resource for imaging research

Preliminary clinical studies suggest that spiral computed tomography (CT) of the lungs can improve early detection of lung cancer in high-risk individuals. More clinical studies are needed, however, before public health recommendations can be proposed for population-based screening. Spiral CT generates large-volume data sets and thus poses problems in terms of implementation of efficient and cost-effective screening methods. Image processing algorithms such as computer assisted diagnostic (CAD) methods have the potential to assist in lesion (eg, nodule) detection on spiral CT studies. CAD methods may also be used to characterize nodules by either assessing the stability or change in size of lesions based on evaluation of serial CT studies, or quantitatively measuring the temporal parameters related to contrast dynamics when using contrast material-enhanced CT studies. CAD methods therefore have the potential to enhance the sensitivity and specificity of spiral CT lung screening studies. Lung cancer screening studies now under investigation create an opportunity to develop an image database that will allow comparison and optimization of CAD algorithms. This database could serve as an important national resource for the academic and industrial research community that is currently involved in the development of CAD methods. The National Cancer Institute request for applications (RFA) (CA-01-001) has already been announced (April 2000) to establish and support a consortium of academic centers to develop this database, the consortium to be referred to as the Lung Image Database Consortium (LIDC). This RFA is now closed. Five academic sites have been selected to be members of the LIDC, the first meeting of this consortium is planned for spring of 2001, and a public meeting is to be held in 2002. This report is abstracted from the previously published RFA to serve as an example of how an initiative is developed by the National Cancer Institute to support a research resource. For specific details of the RFA, please access the following Internet site: http://www. nci.nih.gov/bip/NCI-DIPinisumm.htm#a11.

A comparison of two oral ketamine-diazepam regimens for the sedation of anxious pediatric dental patients

PURPOSE

This study compared 2 oral ketamine-diazepam regimens (8 mg/kg and 10 mg/kg of ketamine in combination with 0.1 mg/kg diazepam) in preschool age children with respect to physiological, behavioral and amnestic parameters.

METHODS

Twenty-five children completed the double-blind, crossover design. Physiologic, behavioral and amnestic effects were evaluated.

RESULTS

ANOVA demonstrated significant changes in systolic blood pressures and heart rates in both the 8 mg/kg group and 10 mg/kg group (P < 0.05), as well as significant changes in diastolic blood pressures in the 10 mg/kg group (P < 0.05). However, these changes were not clinically significant. Success rates were 28% for the 8 mg/kg dosage and 44% for the 10 mg/kg dosage. There was a cumulative vomiting rate of 50% and a psychic phenomena rate of 10%. There were no statistically significant differences between the two dosages with regard to success rates, postoperative vomiting, or psychic phenomena using McNemar's test.

CONCLUSIONS

There is no advantage of 10 mg/kg dose of ketamine over the 8 mg/kg dose. Ketamine did not demonstrate amnestic effects in this study. There were statistically but no clinically significant changes in physiological parameters in either group. This study does not support the use of either 8 mg/kg or 10 mg/kg oral ketamine for the sedation of uncooperative children.

Conformation spaces of proteins

We report a simple method for measuring the accessible conformational space explored by an ensemble of protein structures. The method is useful for diverse ensembles derived from molecular dynamics trajectories, molecular modeling, and molecular structure determinations. It can be used to examine a wide range of time scales. The central tactic we use, which has been previously employed, is to replace the true mechanical degrees of freedom of a molecular system with the conformationally effective degrees of freedom as measured by the root-mean squared cartesian distances among all pairs of conformations. Each protein conformation is treated as a point in a high dimensional euclidean space. In this article, we model this space in a novel way by representing it as an N-dimensional hypercube, describable with only two parameters: the number of dimensions and the edge length. To validate this approach, we provide a number of elementary test cases and then use the N-cube method for measuring the size and shape of conformational space covered by molecular dynamics trajectories spanning 10 orders of magnitude in time. These calculations were performed on a small protein, the villin headpiece subdomain, exploring both the native state and the misfolded/folding regime. Distinct features include single, vibrationally averaged, substate minima on the 0.1-1-ps time scale, thermally averaged conformational states that persist for 1-100 ps and transitions between these local minima on nanosecond time scales. Large-scale refolding modes appear to become uncorrelated on the microsecond time scale. Associated length scales for these events are 0.2 A for the vibrational minima; 0.5 A for the conformational minima; and 1-2 A for the nanosecond events. We find that the conformational space that is dynamically accessible during folding of villin has enough volume for approximately 10(9) minima of the variety that persist for picoseconds. Molecular dynamics trajectories of the native protein and experimentally derived solution ensembles suggest the native state to be composed of approximately 10(2) of these thermally accessible minima. Thus, based on random exploration of accessible folding space alone, protein folding for a small protein is predicted to be a milliseconds time scale event. This time can be compared with the experimental folding time for villin of 10-100 micros. One possible explanation for the 10-100-fold discrepancy is that the slope of the "folding funnel" increases the rate 1-2 orders of magnitude above random exploration of substates.

In vivo imaging of gene expression

Imaging of gene expression is increasingly essential for cancer diagnosis, prediction of tumor response to various available therapies, and for monitoring response to therapy, whether it is gene or nongene therapy. Most of the work on developing techniques and methodologies for imaging gene expression has been performed in mice. Sophisticated small animal imaging technologies have been developed for this purpose. Imaging of gene expression in humans is still very limited. Nuclear medicine, positron-emission tomography, magnetic resonance imaging, and optical methods are the modalities that have shown preliminary utility in imaging gene expression. Two major imaging strategies have been investigated: using marker genes encoding either intracellular enzymes or cell-surface receptors. The first approach exploits the ability of certain enzymes to modify imaging prodrugs, so that tissue accumulation of such drugs reflects the expression. The second approach uses cell-surface expression of ligand-binding receptors that can be detected using imaging tracers. In this review, we summarize some of the imaging techniques that have been developed to detect gene expression.

How experience and training influence mammography expertise

RATIONALE AND OBJECTIVES

The authors evaluated the influence of perceptual and cognitive skills in mammography detection and interpretation by testing three groups representing different levels of mammography expertise in terms of experience, training, and talent with a mammography screening-diagnostic task.

MATERIALS AND METHODS

One hundred fifty mammograms, composed of unilateral cranial-caudal and mediolateral oblique views, were displayed in pairs on a digital workstation to 19 radiology residents, three experienced mammographers, and nine mammography technologists. One-third of the mammograms showed malignant lesions; two-thirds were malignancy-free. Observers interacted with the display to indicate whether each image contained no malignant lesions or suspicious lesions indicating malignancy. Decision time was measured as the lesions were localized, classified, and rated for decision confidence.

RESULTS

Compared with performance of experts, alternative free response operating characteristic performance for residents was significantly lower and equivalent to that of technologists. Analysis of overall performance showed that, as level of expertise decreased, false-positive results exerted a greater effect on overall decision accuracy over the time course of image perception. This defines the decision speed-accuracy relationship that characterizes mammography expertise.

CONCLUSION

Differences in resident performance resulted primarily from lack of perceptual-learning experience during mammography training, which limited object recognition skills and made it difficult to determine differences between malignant lesions, benign lesions, and normal image perturbations. A proposed solution is systematic mentor-guided training that links image perception to feedback about the reasons underlying decision making.

BI-RADS categorization as a predictor of malignancy

PURPOSE

To determine the positive predictive value (PPV) of the American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) categories 0, 2, 3, 4, and 5 by using BI-RADS terminology and by auditing data on needle localizations.

MATERIALS AND METHODS

Between April 1991 and December 1996, 1,400 mammographically guided needle localizations were performed in 1,109 patients. Information entered into the mammographic database included where the initial mammography was performed (inside vs outside the institution), BI-RADS category, mammographic finding, and histopathologic findings. A recorded recommendation was available for 1,312 localizations in 1,097 patients, who composed the study population.

RESULTS

The 1,312 localizations yielded 449 (34%) cancers (139 [31%] were ductal carcinoma in situ [DCIS]; 310 [69%] were invasive cancers) and 863 (66%) benign lesions. There were 15 (1%) category 0 lesions; the PPV was 13% (two of 15 lesions). There were 50 (4%) category 2 lesions; the PPV was 0% (0 of 40 lesions). There were 141 (11%) category 3 lesions; the PPV was 2% (three of 141 lesions). The three cancers in this group were all non-comedotype DCIS. There were 936 (71%) category 4 lesions; the PPV was 30% (279 of 936 lesions). There were 170 (13%) category 5 lesions; the PPV was 97% (165 of 170 lesions).

CONCLUSION

Placing mammographic lesions into BI-RADS categories is useful for predicting the presence of malignancy. Perhaps, most important, a lesion placed into BI-RADS category 3 is highly predictive of benignity, and short-term interval follow-up as an alternative to biopsy would decrease the number of biopsies performed in benign lesions.

A sequential chart for the audit-based evaluation of screening mammogram interpretation

RATIONALE AND OBJECTIVES

Auditing has received much attention recently as a method for radiologists to use to evaluate their interpretation of screening mammograms. U.S. Food and Drug Administration regulations require that some sort of audit be in place before a mammography screening facility can receive accreditation. Auditing presents a unique opportunity to monitor accuracy continually and identify problems early. Audit data present unique challenges, however, and appropriate methods must be used to control the risk of errors.

MATERIALS AND METHODS

This article introduces a simple method for the task of deciding if a radiologist yields an acceptable positive predictive value based on audit. The method is based on "sequential" decision-making techniques that have found wide application in quality control problems. These techniques are developed for diagnostic radiology and embodied in an easy-to-use decision-making chart.

RESULTS

Several examples, based on audit data from actual mammography facilities, provide insights into the use of these charts and the influence of (a) the selection of standards, (b) the selection of error risks, and (c) radiologist variability. The examples also serve to demonstrate another important property of this method--that is, it specifies the minimum amount of data that has to be collected before any decision can reliably be made.

CONCLUSION

The chart presented in this article provides a method by which audit data can be used objectively to evaluate the accuracy of screening mammogram interpretation. The method controls the risk of either falsely accepting an unqualified radiologist or falsely rejecting a qualified radiologist. It should be a useful tool to radiologists who must evaluate their own practices.

Disparity mapping applied to sonography of the breast: technical note

A two-dimensional sonoelastographic technique called "disparity mapping" was applied to breast sonographic examinations in eight patients to test discrimination between benign and malignant lesions. With probe compression, pairs of gray-scale sonographic scans were obtained about 1 second apart. The disparity mapping procedure calculated the apparent displacement of the speckle pattern about each point in the image and presented that information in the form of a disparity map. Findings were consistent with a firm lesion in two of the three cancers, were indistinguishable from normal tissue in all three fibroadenomas, were indistinguishable from normal findings in one cyst, and showed no disparity in one cyst because it had few internal echoes.

Susceptibilities of clinical and laboratory isolates of Blastomyces dermatitidis to ketoconazole, itraconazole, and fluconazole

Eighteen isolates of Blastomyces dermatitidis were evaluated for their in vitro susceptibilities to ketoconazole, itraconazole, and fluconazole. The MIC ranges were 0.1 to 0.4 microg/ml for ketoconazole, < or =0.018 to 0.07 microg/ml for itraconazole, and 2.5 to 4.0 microg/ml for fluconazole. The ranges for the minimal lethal concentrations were 0.2 to 0.8 microg/ml for ketoconazole, < or =0.018 to 0.07 microg/ml for itraconazole, and 10 to 40 microg/ml for fluconazole. Itraconazole was the most active agent against B. dermatitidis in vitro, while fluconazole was the least active. These results correlate with the clinical efficacies noted to date with doses of these agents used to treat blastomycosis.

Breast carcinoma: MR imaging before re-excisional biopsy

PURPOSE

To investigate the role of magnetic resonance (MR) imaging in the examination of patients after excisional biopsy of breast carcinoma before re-excision.

MATERIALS AND METHODS

Forty-seven patients underwent contrast material-enhanced MR imaging after initial excisional biopsy of breast carcinoma before further surgery.

RESULTS

The positive predictive value of MR imaging for predicting residual disease was 82%; the negative predictive value was 61%. Fourteen patients had multifocal (n = 6) or diffuse (n = 8) carcinoma. The extent of tumor was correctly identified with MR imaging alone in nine of the 14 patients, with both mammography and MR imaging in three patients, with mammography alone in one patient, and with no imaging modality in one patient. In four of the 14 patients, management was altered from re-excision to mastectomy (n = 3) or from breast-conservation therapy to mastectomy (n = 1).

CONCLUSION

MR imaging has a high positive predictive value for predicting residual tumor after excisional biopsy. The identification of mammographically and clinically unsuspected multifocal or extensive residual tumor may lend support for mastectomy rather than re-excision. However, false-negative findings due to postsurgical changes and false-positive findings due to enhancement of granulation tissue and benign breast tissue remain limitations.

MR imaging of ductal carcinoma in situ

PURPOSE

To investigate the ability of magnetic resonance (MR) imaging to depict ductal carcinoma in situ (DCIS).

MATERIALS AND METHODS

Between January 1992 and April 1996, 330 women underwent MR imaging before excisional biopsy. Of these, 101 women had carcinoma, 19 of whom had DCIS. The MR imaging findings in the 19 women were reviewed.

RESULTS

Thirteen of 19 patients had pure DCIS. The mean lesion diameter was 10 mm (range, 2-22 mm). MR imaging enabled identification of DCIS in 10 (77%) of the 13 cases as ductal enhancement (n = 6), regional enhancement (n = 3), or a peripherally enhancing mass (n = 1). The three lesions not identified had a mean diameter of 3.7 mm. Six of 19 patients had both DCIS and an invasive cancer. In four of these patients, DCIS was identified only at MR imaging (mean diameter, 3 mm). In two of six patients, DCIS was not identified at MR imaging.

CONCLUSION

MR imaging can depict mammographically visible and occult foci of DCIS. Some small foci of DCIS detected at mammography and histologic examination, however, may be occult at MR imaging.

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.