Characterization and elimination of AC noise in electrocardiograms: a comparison of digital filtering methods

Diverse digital methods have been advanced previously to remove power line (AC) interference in the ECG. Representative notch filters, adaptive filters and a globally derived filter are surveyed in this study; their performances are compared on artificial signals as well as actual ECGs. The ECGs, recorded at four European medical centers, are from the Common Standards in Electrocardiography (CSE) ECG tape library. AC interference in these ECGs is shown to exhibit two qualities especially relevant to filter design: considerable deviations from a nominal 50 Hz frequency and substantial noise at higher harmonics. Some criteria and useful quantitative measures are suggested to evaluate AC digital filters.     

Calibration of ion chambers for use in mammography

There is at present no UK calibration service for ion chambers for mammography, where X-ray beams are produced from tubes having molybdenum targets and filters. This paper reports calibrations against a radiotherapy secondary standard (calibrated for beams from tungsten targets with aluminium filters) using beams from both types of target and filter. Two examples of the Radcal mammography dosimeter were found to have calibration factors which varied by less than 1% in molybdenum target beams from 30 to 40 kV. Differences between calibrations using the two types of X-ray beam did not exceed about 2%. All calibration factors were within about +/- 2% of 1.0. Errors are thought to be within +/- 3%. The results of an independent calibration of one of these dosimeters against a similar chamber calibrated by CEC are also reported. Calibrations of this kind can only be temporary expedients until adequate calibration facilities for mammography beams become available, but are nevertheless useful.     

Outcomes of modern screening mammography

The University of California, San Francisco, Mobile Mammography Screening Program is a low-cost, community-based breast cancer screening program that offers mammography to women of diverse ethnic backgrounds (36% nonwhite) in six counties in northern California. Analysis of data collected on approximately 34,000 screening examinations from this program shows that the positive predictive value and sensitivity of modern screening mammography to be lower for women aged 40 to 49 years compared to women aged 50 and older. This lower performance is due to the lower prevalence of invasive breast cancer in younger women and possibly to age differences in breast tumor biology. Because of this lower performance, women in their forties may be subjected to more of the negative consequences of screening, which include additional diagnostic evaluations and the associated morbidity and anxiety, the potential for detecting and surgically treating clinically insignificant breast lesions, and the false reassurance resulting from normal mammographic results. Since the evidence is not compelling that the benefits of mammography screening outweigh the known risks for women aged 40 to 49 years, women considering mammography screening should be informed of the risks, potential benefits, and limitations of screening mammography, so that they can make individualized decisions based on their personal risk status and utility for the associated risks and potential benefits of screening.     

False-positive and false-negative rates in meconium drug testing

To determine the number of false-negative results produced by inefficient extraction of drugs from meconium, three published procedures were compared by using previously confirmed positive and negative meconium specimens. The methods were not equivalent in their ability to extract drugs from the matrix. To determine the number of false positives reported by the use of screen-only (unconfirmed) results, 535 screen-positive meconium specimens were subjects to confirmation by gas chromatography-mass spectrometry. Fifty-seven percent of the samples were confirmed positive for one or more of the drugs under investigation, showing that a false-positive rate as high as 43% may exist when unconfirmed screening results are used.     

Classification of compressed breast shapes for the design of equalization filters in x-ray mammography

We are developing an external filter method for equalizing the x-ray exposure in mammography. Each filter is specially designed to match the shape of the compressed breast border and to preferentially attenuate the x-ray beam in the peripheral region of the breast. To be practical, this method should require the use of only a limited number of custom built filters. It is hypothesized that this would be possible if compressed breasts can be classified into a finite number of shapes. A study was performed to determine the number of shapes. Based on the parabolic appearance of the outer borders of compressed breasts in mammograms, the borders were fit with the polynomial equations y = ax2 + bx3 and y = ax2 + bx3 + cx4. The goodness-of-fit of these equations was compared. The a,b and a,b,c coefficients were employed in a K-Means clustering procedure to classify 470 CC-view and 484 MLO-view borders into 2-10 clusters. The mean coefficients of the borders within a given cluster defined the "filter" shape, and the individual borders were translated and rotated to best match that filter shape. The average rms differences between the individual borders and the "filter" were computed as were the standard deviations of those differences. The optimally shifted and rotated borders were refit with the above polynomial equations, and plotted for visual evaluation of clustering success. Both polynomial fits were adequate with rms errors of about 2 mm for the 2-coefficient equation, and about 1 mm for the 3-coefficient equation. Although the fits to the original borders were superior for the 3-coefficient equation, the matches to the "filter" borders determined by clustering were not significantly improved. A variety of modified clustering methods were developed and utilized, but none produced major improvements in clustering. Results indicate that 3 or 4 filter shapes may be adequate for each mammographic projection (CC- and MLO-view). To account for the wide variations in exposures observed at the peripheral regions of breasts classified to be of a particular shape, it may be necessary to employ different filters for thin, medium and thick breasts. Even with this added requirement, it should be possible to use a small number of filters as desired.     

Visibility of microcalcifications in computed and screen-film mammography

Due to the clinically and technically demanding nature of breast x-ray imaging, mammography still remains one of the few essentially film-based radiological imaging techniques in modern medical imaging. There are a range of possible benefits available if a practical and economical direct digital imaging technique can be introduced to routine clinical practice. There has been much debate regarding the minimum specification required for direct digital acquisition. One such direct digital system available is computed radiography (CR), which has a modest specification when compared with modern screen-film mammography (SFM) systems. This paper details two psychophysical studies in which the detection of simulated microcalcifications with CR has been directly compared to that with SFM. The first study found that under scatter-free conditions the minimum detectable size of microcalcification was approximately 130 microns for both SFM and CR. The second study found that SFM had a 4.6% higher probability of observers being able to correctly identify the shape of 350 microns diameter test details; there was no significant difference for-either larger or smaller test details. From the results of these studies it has been demonstrated that the modest specification of CR, in terms of limiting resolution, does not translate into a dramatic difference in the perception of details at the limit of detectability. When judging the imaging performance of a system it is more important to compare the signal-to-noise ratio transfer spectrum characteristics, rather than simply the modulation transfer function.     

Quantitative evaluation of local drug delivery using the InfusaSleeve catheter

BACKGROUND: Rural women are less likely to receive screening mammography at recommended intervals. This study evaluated efforts to promote screening mammography among women in rural communities through community education interventions and low-cost mobile mammography van services. METHODS: Two matched sets of communities were identified in an isolated rural region. One area received community education programs in addition to the mammography van for 2 years; the second area received only the van services. The educational programs were designed using diagnostic research methods; they included recruitment of opinion leaders to organize small group breast screening education sessions, an information campaign using direct mail, and primary health care provider education. RESULTS: A household telephone survey conducted 6 months after completion of these programs indicated that mammography utilization and perceived mammography norms were higher among women in the Program area than among women in the Comparison area. Process data were consistent with these findings. Clinical examination and self-examination behaviors were not influenced by the programs. CONCLUSIONS: This study showed that well-focused educational interventions for rural women can increase utilization of screening mammography when access and cost barriers also are reduced.     

Diagnostic framework of nonpalpable lesions of the breast

Mammography is the most sensitive test for non-palpable lesions, but its specificity is quite limited. When a decision for biopsy is based only on the mammographic appearance the benign/malignant biopsy ratio (B/M) is around 3:1. The B/M varies according to the radiological pattern being favourable for stellate opacities, high for regular opacities, and intermediate for distortions and microcalcifications. Aspiration cytology of non-palpable lesions, either sonographically or stereotaxically guided, is highly accurate. When the decision for surgical biopsy is taken also on the basis of cytology, B/M may be reduced by up to 0.5:1. As false negatives are expected for cytology, lesions which are strongly suspicious at mammography must be biopsied anyway. Sonography guided aspiration is possible in about a half of mammographically detected non-palpable lesions, particularly for opacities, whereas distortions and microcalcification are seldom visualized at sonography. Cytology should be routinely performed in the presence of questionable non-palpable lesions.     

Report of the Department of Defense, National Cancer Institute, Department of Health and Human Services Office of Women''s Health workshop on the mobile breast care center

The present study examines women's decision making about mammography over a 1-year period, using "decisional balance," a summary of women's positive and negative perceptions about mammography derived from the Transtheoretical Model (TTM). Data were from a survey of women ages 50-74 years who completed both the baseline and 1-year follow-up telephone surveys (n = 1144) for an intervention study to increase the use of mammography screening. A shift toward less favorable perceptions about mammography was related to being a smoker and not having a recent clinical breast examination and Pap test. Change in women's attitudes toward mammography was also related to four dimensions of a woman's information environment. Women who rated the opinions of a physician as somewhat or not important, those who reported that at least one family member or friend discouraged them from having a mammogram, and women who felt they lacked enough people in their social network with whom they could discuss health concerns were less likely to express favorable attitudes about mammography over 1 year. In contrast, women who consistently communicated the value of mammography to others expressed more favorable views of screening over the study period. Interventions designed to promote breast cancer screening must recognize that a woman not only reacts to mammography information provided by significant others in her social network but may proactively reach out to others as an advocate of breast cancer screening, thus reinforcing or changing others' opinions or behavior as well as her own.     

Radiology of nonpalpable breast lesions

The authors reviewed 619 consecutive cases of breast nonpalpable lesions detected with mammography in which wire-directed open biopsy or stereotaxic biopsy was performed from 1984 to 1993. The ratio of benign to malignant biopsy findings was 4:1 for the whole series. The positive predictive value (PPV) of different radiologic pattern was determined. Biopsy is advised in the presence of patterns such as strongly suspect microcalcifications (granular or branching morphologic features), stellate masses, parenchimal distortion, opacities with undefined borders and asymmetric density, which yielded higher PPVs (26%, 93%, 92%, 35%, 42% and 19% respectively). However, follow-up with mammography is advised in probably benign lesions (opacity with regular borders and clusters of round or oval particles of calcifications), which yielded lower PPVs (1.5% and 3%). By decreasing the number of biopsies of probably benign lesions and thereby substantially reducing costs, this approach may help to widespread use of mammographic screening.     

A multiresolution approach for contour extraction from brain images

Many image registration methods use head surface, brain surface, or inner/outer surface of the skull to estimate rotation and translation parameters. The inner surface of the skull is also used for intracranial volume segmentation which is considered the first step in segmentation and analysis of brain images. The surface is usually characterized by a set of edge or contour points extracted from cross-sectional images. Automatic extraction of contour points is complicated by discontinuity of edges in the back of the eyes and ears and sometimes by a previous surgery or an inadequate field of view. We have developed an automated method for contour extraction that connects discontinuities using a multiresolution pyramid. Steps of the method are: (1) Contour points are found by an edge-tracking algorithm; (2) A multiresolution pyramid of contour points is constructed; (3) Contour points of reduced images are found; (4) From the continuous contour found at the lowest resolution, contour points at a higher resolution are found; (5) Step 4 is repeated until contour points at the highest resolution (original image) are found. The method runs fast and has been successful in extracting contours from MRI and CT images. We illustrate the method and its performance using MRI and CT images of the human brain.     

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.     

Method for determination and element analysis of particulate contamination in injectable solutions

A method for sampling and evaluating the chemical and physical composition of particles in injectable solutions was developed. The technique facilitates detection of the particles' sources and possible medical hazards. Particles exceeding 0.2 mum are collected on a membrane filter sized for direct application in a scanning electron microscope (SEM). The sampling device shortens the distance between filter and solution and minimizes contamination from the filter holder. Following coating of the membrane filter with gold, the particles are counted by screening at a magnification of 5,000 x in the SEM. Both unused membrane filters and filters through which a solution of 0.9% sodium chloride had been passed were analyzed. X-ray analysis of particles on the clean filter revealed silicon, aluminum (artifact from the stud) and calcium. X-ray analysis of the filter after passage of 1 liter normal saline revealed chromium, copper, iron, magnesium, manganese, aluminum (from study), calcium chlorine, sodium and silicon. Recommendations for standard procedures for particle detection in large-volume injectables are given.     

Mammographically negative breast cancer at the Strathfield Breast Centre

BACKGROUND: The current diagnostic modalities used to detect breast cancer are mammography, together with clinical examination, ultrasound and fine needle aspiration biopsy (FNAB). The accuracy rates for each modality varies and a combination of the modalities is recommended to detect cancer early. Some authors have suggested that mammography should be used primarily as a screening tool because of the false negative mammography results that have been reported in the past 10 years. The records of patients at the Strathfield Breast Centre were reviewed to determine the accuracy of other modalities. METHODS: The records of 371 breast cancer patients treated at the Strathfield Breast Centre in the 6 years form 1989 to 1994 were reviewed to determine the accuracy of mammography, ultrasound, clinical examination and fine needle aspiration biopsy. Of the 371 women with histopathologically diagnosed breast cancer, 349 had mammography. RESULTS: The accuracy rate of mammography in the present study was 91% with a false negative rate of 9%. It was found that there was no significant delay in treatment of breast cancer in mammogram-negative patients. CONCLUSIONS: Mammographically negative breast cancer was found to be more common in younger women, to be similar in size to mammogram-positive cancer, to occur in all histological types and grades and was usually invasive rather than noninvasive. The rate of lymph node involvement was similar to the mammogram-positive group.     

Management of arthritis

Over the last 25 years the diagnostic approaches and therapeutic strategies of breast cancer have dramatically changed. The relationship between diagnosis and therapy has gradually become more complex due to the ever more sophisticated diagnostic tools (mammographic screening, digital mammography, magnetic resonance, SPECT scan and FDG-PET), which have improved resolution limits and accuracy, and also due to the different therapeutic planning applied to breast cancer in these years (conservative surgery, neo-adjuvant chemotherapy, axillary dissection or not). Thus, in this paper, we have briefly analyzed the many open questions in breast cancer management and the clinical challenges of present diagnostic tools in relation to pre-, peri- and postoperative phases, and to therapeutic strategies in general. The main goal of mammographic screening is to detect early invasive cancers and to treat them at the first useful moment. However, at which age should one begin screening, and what is the impact on overall survival, the cost-effectiveness, and, most of all, the best operative approach to suspect lesions? Can digital mammography give a better quality of imaging with respect to conventional mammography? Does unexpected multicentricity and/or multifocality, which is sometimes showed by magnetic resonance, have any clinical relevance? Is this technique really better than traditional methods for the identification of local recurrence? Is scintimammography able to improve the low diagnostic accuracy of mammography on non-palpable breast lesions? Moreover, at present, the need for axillary dissection and its therapeutic and staging value is deeply debated: however, clinical detection of axillary metastases is not a reliable diagnostic tool and there are no conventional radiologic techniques to be used: recently nuclear medicine imaging has provided various approaches, such as SPECT scan with different tracers, FDG-PET, or lymphoscintigraphy with gamma probe sentinel biopsy: there are not only methodologic but also phylosophic differences in using these techniques. Neo-adjuvant chemotherapy has allowed a dramatic reduction of primary breast cancer with a replanning of the surgical approach to large breast tumours but, at the same time, has posed new questions such as the adequacy of diagnostic pre- and perioperative revaluation. Finally, does postoperative follow-up take advantage of intensive diagnostic programs and are there therapeutic margins which would improve survival of patients with metastatic disease? This paper is an attempt to analyze the answers given in the literature. Nevertheless, at present, this matter is globally in progress and a scientific debate will provide, in the near future, a new promising scenario for breast cancer management.     

Ten-year risk of false positive screening mammograms and clinical breast examinations

BACKGROUND: The cumulative risk of a false positive result from a breast-cancer screening test is unknown. METHODS: We performed a 10-year retrospective cohort study of breast-cancer screening and diagnostic evaluations among 2400 women who were 40 to 69 years old at study entry. Mammograms or clinical breast examinations that were interpreted as indeterminate, aroused a suspicion of cancer, or prompted recommendations for additional workup in women in whom breast cancer was not diagnosed within the next year were considered to be false positive tests. RESULTS: A total of 9762 screening mammograms and 10,905 screening clinical breast examinations were performed, for a median of 4 mammograms and 5 clinical breast examinations per woman over the 10-year period. Of the women who were screened, 23.8 percent had at least one false positive mammogram, 13.4 percent had at least one false positive breast examination, and 31.7 percent had at least one false positive result for either test. The estimated cumulative risk of a false positive result was 49.1 percent (95 percent confidence interval, 40.3 to 64.1 percent) after 10 mammograms and 22.3 percent (95 percent confidence interval, 19.2 to 27.5 percent) after 10 clinical breast examinations. The false positive tests led to 870 outpatient appointments, 539 diagnostic mammograms, 186 ultrasound examinations, 188 biopsies, and 1 hospitalization. We estimate that among women who do not have breast cancer, 18.6 percent (95 percent confidence interval, 9.8 to 41.2 percent) will undergo a biopsy after 10 mammograms, and 6.2 percent (95 percent confidence interval, 3.7 to 11.2 percent) after 10 clinical breast examinations. For every 100 dollars spent for screening, an additional 33 dollars was spent to evaluate the false positive results. CONCLUSIONS: Over 10 years, one third of women screened had an abnormal test result that required additional evaluation, even though no breast cancer was present. Techniques are needed to decrease false positive results while maintaining high sensitivity. Physicians should educate women about the risk of a false positive result from a screening test for breast cancer.     

Mammography versus clinical examination of the breasts

Using published data from screening trials, this article compares two-modality (mammography and clinical examination) and single-modality (clinical examination alone) screening by evaluating cancer detection rates, program sensitivities, mode of cancer detection in two-modality screening, nodal status at time of detection, survival 10 years post-diagnosis, and breast cancer mortality 10 years after entry. Consistently, two-modality screening achieved higher cancer detection rates and program sensitivity estimates than either modality alone; mammography alone achieved higher rates than clinical examination alone; interval cancer detection rates between screening examinations were higher following clinical examination alone than mammography alone; single-modality screening with mammography failed to detect breast cancers identified by clinical examination alone; the sensitivity of mammography was lower in younger than older women, while the reverse was true for clinical examination; and mammography identified a higher proportion of node-negative breast cancer than clinical examination. We conclude that combining clinical breast examination with mammography is desirable for women age 40-49 because mammography is less sensitive in younger than older women. Careful training and monitoring are, however, as essential with clinical examiners as with mammographers.     

Axillary node metastasis from T1N0M0 breast cancer: possible avoidance of dissection in a subgroup

BACKGROUND: Axillary lymph node dissection is now no longer considered to be the standard treatment in all patients with invasive breast cancer. We have attempted to identify a sub-group of patients with invasive breast carcinoma who may not need to undergo axillary lymph node dissection. METHODS: Patients (n = 823) with T1 N0M0 invasive breast cancer treated at our hospital between 1970 and 1994 were studied. We investigated the relationship between positive axillary lymph nodes and the following clinico-pathological factors: patient age, menopausal status, contralateral breast cancer (synchronous or asynchronous), tumor location, tumor size (T:cm), histopathology, histological grade, presence or absence of malignant microcalcification or spiculation on mammography and estrogen receptor status. RESULTS: The incidence of axillary lymph node metastases in patients with T1N0M0 invasive breast cancer was 25% (208/823). The node-negative group was significantly older than the node-positive group. Premenopausal patients had a higher rate of lymph node metastases although this was not significant. The frequency of nodal metastases when related to the tumor size was as follows: T< or =1.0 cm, 17%; T< or =1.5 cm, 25%; T< or =2.0 cm, 29%. Mammography revealed that patients with malignant calcification or spiculation had a significantly higher rate of nodal metastases than those without these findings. Certain tumor types (medullary, mucinous and tubular carcinomas) had lower positive rates for lymph node involvement. With regard to the histological grade, lymph node positivity increased significantly with high-grade tumors. No correlation was observed between any other factors and the presence or absence of lymph node metastases. CONCLUSIONS: It may be possible to avoid axillary lymph node dissection in postmenopausal patients (50 years or older) where the histological type is favorable when the tumor diameter is < or =1.0 cm and when microcalcification or spiculation is absent on mammography.     

Use of Impedance Probe for Estimation of Porosity Changes in Saturated Granular Filters under Cyclic Loading: Calibration and Application

Gravimetric and volumetric sampling techniques are reliable for the measurement of porosity in fully saturated granular filters. However, both methods require a significant effort to gather and prepare samples, are time intensive to process, and do not capture real-time changes. Portable impedance probes serve as a valuable alternative to these destructive and laborious sampling methods. These probes measure the dielectric properties of the soil-water mixtures from which the porosity of filters may be inferred. This study demonstrates that generalized calibrations can result in large errors for porosity estimation when using diverse and small-scale filter types. By comparing with gravimetric and volumetric based porosity measurements for saturated granular filter porosity, impedance probes with filter-specific calibration offer the reliability and confidence owing to its reduced error in a quick, nondestructive fashion. This paper also presents the results of a laboratory investigation using an impedance probe to monitor real-time changes in the porosity of saturated granular filters subjected to cyclic train loading.     

Assessing elements of women's decisions about mammography.

Investigated motivational and cognitive processes of behavior change with respect to mammography screening. 142 women (aged 40–75 yrs) answered a 41-item questionnaire consisting of statements based on constructs from the transtheoretical model of behavior change. Principal-components analysis identified 2 factors: a 6-item component representing positive perceptions of mammography (pros) and a 6-item component representing avoidance of mammography (cons). Pros, cons, and a derived decisional balance measure (pros minus cons) were associated with stage of mammography adoption. The model is discussed as it relates to other theories of behavior change and as a general strategy for analyzing perceptual data pertinent to health-related actions and intentions for behavioral change. (PsycINFO Database Record (c) 2010 APA, all rights reserved)