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Biomedical subjects

G S Shaber

Publications and source records attributed to G S Shaber.

15 recordsLinked to original sources
PubMed1993

Cost containment in the use of low-osmolar contrast agents: effect of guidelines, monitoring, and feedback mechanisms.

PURPOSE: To describe a program for controlling intravenous use of low-osmolar contrast agents (LOCAs). MATERIALS AND METHODS: The department of radiology at the authors' institution adopted a policy of selective use of intravenously administered LOCAs. Clinical indications for LOCA use were specified after consultation with the administration, risk managers, legal department, and ethics committee of the hospital. The guidelines were then publicized throughout the department and hospital, and a contrast agent data form was developed to collect data on all cases. Monitoring mechanisms were instituted. RESULTS: Over the next 23 months, 11,373 patients received intravenous iodinated contrast agents, of whom 28.1% were deemed to be at high risk and were given LOCAs. Monthly tracking showed no evidence of a trend toward increasing use of LOCAs. CONCLUSION: Clear definition of use guidelines, close monitoring, and feedback can stabilize LOCA use at acceptably low levels.

Adult↗
PubMed1984

Localization and significance of clinically occult breast lesions: experience with 469 needle-guided biopsies.

Experience with 469 clinically occult breast lesions is presented. The overall incidence of malignancy observed was 32%, just about one in three. The technique of needle-guided biopsy is described, insuring precise localization and excision of minute radiographic findings, yet without leaving a conspicuous scar to remind the patient of her experience. Although it is too early to speculate about a possible increase in survival of these "earliest" breast cancers, the observed decreased incidence of axillary node metastasis implies a lowered death rate from breast cancer in these patients. It is not unreasonable to extrapolate the extent of patient salvage from axillary node status. Many of these cancers were uncovered in the course of screening asymptomatic patients, and this further implies the efficacy of such screening programs in the early detection of breast cancer. The surprisingly high incidence of multicentricity in these tiny cancers must not be ignored when recommending adequate and appropriate therapy for these impalpable malignancies.

Adult↗
PubMed1982

Clinical experience with a prototype real-time dedicated breast scanner.

The evaluation of 1,003 sonomammographic examinations on a predominantly symptomatic population using a prototype real-time dedicated breast scanner is presented. Interpretations were initially made by one of four experienced radiologists without knowledge of clinical data (i.e., symptoms, age, physical findings, or other imaging modality interpretations). A second interpretation was subsequently made with this information. Pathologic confirmation was available on 262 lesions, including 71 carcinomas and 191 benign biopsies. Of the carcinomas, 19 were smaller than 2.0 cm in diameter. The sensitivity of sonographic detection of breast cancer on initial readings was 0.76 and on second readings with clinical data was 0.85. The specificity for a benign reading on sonography was 0.80 on initial interpretation and 0.81 on the second interpretation.

Adolescent↗
PubMed1981

Ultrasound mammography: a comparison with radiographic mammography.

The results of 1,029 ultrasound B-scan examinations of the breast using two automated water-path scanners were correlated with histopathology data in 278 patients who had undergone biopsy. Of the 1,029 patients, a subgroup of 709 patients had both ultrasound mammograms (USM) and radiographic mammograms (XRM) obtained. A sensitivity for breast cancer of 69% was found for USM and 74% for XRM on initial independent readings when there was no knowledge of clinical data. These are not statistically different using the McNemar test for paired comparisons. When the USM were reinterpreted with the knowledge of the patient's age, history, physical examination, and, when available, the XRM interpretation, the USM sensitivity for breast cancer was 79%.

Adolescent↗
PubMed1980

Multicentricity of non-palpable breast cancer.

One hundred eighty-nine biopsies have been performed for clinically occult mammary lesions, detectable by mammography but not clinically apparent. Fifty-two cancers were demonstrated within this group, including 26 invasive ductal cancers, seven micro-invasive ductal cancers, 14 non-invasive ductal cancers, and five lobular carcinomas in situ. All mastectomy specimens were examined for multicentric foci of breast cancer in quadrants other than that in which the primary lesion was located. Of the invasive ductal cancers, 40% were multicentric. Of the micro-invasive ductal cancers, 57.1% were multicentric. Of the non-invasive ductal cancers, 45.5% were multicentric. The one mastectomy specimen from a patient with lobular carcinoma in situ did not have evidence of residual disease. The overall incidence of multicentricity in the 43 specimens examined was 44.2%. These findings suggested that any therapeutic procedure for either invasive or non-invasive ductal carcinoma that does not include total mastectomy may leave behind foci of cancer, which are a threat to the patient.

Breast Neoplasms↗
PubMed1980

Clinically occult breast cancer. Multicentricity and implications for treatment.

Two hundred thirty-two biopsies have been performed for nonpalpable mammary lesions, detectable by mammography, but not clinically apparent. Sixty-two malignancies were demonstrated within this group, including thirty invasive ductal cancers, seven minimally invasive ductal cancers, 20 noninvasive ductal cancers, and five lobular carcinomas-in situ. When mastectomy specimens were examined for evidence of multifocal cancer in quadrants other than that in which the primary was located, 39.6% of the breasts examined demonstrated evidence of multifocal cancer ductal or lobular, invasive or non-invasive. These findings suggest that any therapeutic procedure for invasive or noninvasive ductal cancer which does not include total mastectomy may leave behind foci of cancer which may be a threat to the patient.

Adult↗
PubMed1978

Tubular carcinoma of the breast. Mammographic appearance and pathological correlation.

Xeromammographic and pathological findings in 17 cases of tubular carcinoma of the breast are presented. No patients had axillary lymph node involvement. The mean lesion size was 0.95 cm. Thirteen lesions (76%) were clinically occult. Because of the characteristic histological pattern of infiltrative growth and marked desmoplasia, 81% (13/16) were seen on xeromammography as scirrhous masses, 19% (3/16) only as microcalcifications. None appeared as a well-circumscribed mass or poorly defined density.

Aged↗
PubMed1977

The pathology of breast cancer detected by mass population screening.

Breast cancer was detected in 156 of 17,526 asymptomatic women, (8.9/1000), aged 45-64 years, screened by mammography, thermography, and physical examination, Twenty-six percent of 149 pathologically reviewed cases metastasized to axillary nodes. Thirty-six percent of tumors were in situ, minimally invasive, or low grade tubular carcinomas, none of which metastasized. Increased rates of detection were shown for intraductal and tubular types. Frankly invasive ductal and lobular carcinomas had a mean diameter of 2.3 cm., 46% of which had axillary lymph node metastases. Seventy-percent of these were to only one to three nodes, however. Multicentricity with intraductal and lobular carcinoma in situ was frequently observed. Metastatic potential was related to tumor size, degree of stromal invasion, lymphatic permeation, and histologic grade. Few histological parameters other than size could be considered favorable. Forty-two percent of tumors were not palpable, the majority being in situ, minimally invasive, and tubular types. Only five nonpalpable invasive carcinomas metastasized. While the initial results of mass screening appear favorable, prolonged follow-up is needed to determine its impact on the population at risk.

Adult↗
PubMed1977

Thermography, mammography, and clinical examination in breast cancer screening. Review of 16,000 studies.

Breast cancer screening detected 139 biopsy-proved malignancies in 16,000 slef-selected women (8.7/1,000). In these, xeroradiography detected 78% (109), clinical examination 55% (76), and thermography 39% (54). In all 16,000 women, the thermogram was interpreted as positive in 17.9% (2,864). The greatest effectiveness of mammography vs. clinical examination was seen in detection of early breast cancers (small lesions with negative axillary lymph nodes). In this group, thermography was less effective than it was in patients with larger lesions and lymph node metastases.

Breast Neoplasms↗
PubMed1977

Analysis of clinically occult and mammographically occult breast tumors.

Findings by xeromammography and clinical examination were compared in 16,000 self-selected women aged 45-64 who participated in a voluntary breast cancer screening program. A total of 138 malignancies were detected: 108 (78%) by mammography and 78 (57%) by clinical examination. Mammography was more effective for large breasts, fatty breasts, and in older women. Conversely, clinical examination was more effective for small breasts, dense breasts, and retroareolar lesions. Clinical detection decreased strikingly for lesions with negative lymph nodes, in situ and microinvasive lesions, deeply situated lesions, and lesions where microcalcifications were the sole mammographic finding.

Age Factors↗
PubMedDate not supplied

Neural networks in radiology: an introduction and evaluation in a signal detection task.

Neural networks are a computer architecture, implementable in software or hardware, that allow an entirely new approach to the computerized perception of data. These so-called connectionist models are inspired by what is known about the architecture of biological neurons, in which the "intelligence" or processing capability of the network is a result of the interconnection strengths between large arrays of nonlinear processing nodes. Neural networks are described and then are used to analyze the common radiological problem of pattern recognition on a noisy background. Classical signal detection theory is used to compare network performance against that of human observers, using computer-generated sets of very simple "nodules." The neural network performed with better accuracy, relative to human observer performance, in the detection of this elementary test object. Although these results may not scale up with more complex images, the favorable performance of neural networks at this level suggests that further investigation is warranted.

Artificial Intelligence↗
PubMedDate not supplied

Dual-energy mammography: a detector analysis.

Dual-energy mammography acquisition scenarios employing single-shot techniques are examined using computer simulation. A figure of merit of the signal-to-noise ratio squared over the glandular dose was chosen for the optimization task due to its exposure independence. Doses were evaluated using Monte Carlo techniques. The effects of kilovoltage, prepatient filtration, front detector thickness, mid-detector filtration thickness and composition were studied. Of the six detector pairs studied (Y2O2S/Gd2O2S, SrFBr/BaFBr, Y2O2S/LaOBr, Y2O2S/CaWO4, Y2O2S/YTaO4, and Y2O2S/LuTaO4), Y2O2S/Gd2O2S and SrFBr/BaFBr were found to be the best combinations. The effects of scatter and signal quantization were also examined. An alternative display technique whereby the tissue-subtracted (i.e., calcium) image is colorized and overlaid onto the conventional mammogram is introduced.

Color↗