Biomedical subjects

Pamela Schraedley-Desmond

Publications and source records attributed to Pamela Schraedley-Desmond.

10 recordsLinked to original sources

PubMed2006

Coverage of emergency after-hours ultrasound cases: survey of practices at U.S. Teaching hospitals.

RATIONALE AND OBJECTIVES: Diagnostic ultrasound examinations may be performed after-hours by physicians if technologists are not available or cases are complex. Our experience suggested there is wide variability in how ultrasound coverage is provided after-hours, which motivated us to conduct a formal survey of teaching programs around the country. METHODS: Four hundred five members of the Association of Program Directors in Radiology were contacted by e-mail and sent a link to a five-part questionnaire posted on the Web. Respondents were asked whether ultrasound cases after-hours are performed in their institutions by radiology residents, technologists on the premises after-hours, technologists on-call, or some combination. Data on the type of program, number of beds in the primary hospital, number of residents in the program, and geographic location of the program were recorded. Responses were automatically written to a data file stored on a Web server and the imported into an Excel spreadsheet for data analysis. A chi(2) analysis was performed to assess associations among the variables and statistical significance. RESULTS: A total of 79 programs responded to the survey. Of those, 32% provided coverage with ultrasound technologists on call, 24% by ultrasound technologists on the premises, 13% provided combination coverage, and 10% provided coverage solely with residents on call. There was no association among number of residents in the program, location of the program, or type of program (university, community, or affiliated) and type of coverage provided. CONCLUSION: There is wide variability in methods for providing coverage of after-hours ultrasound cases. However, on-site or on-call coverage of emergency cases by technologists did not appear to depend significantly on program location, program type, or program size.

After-Hours Care↗

PubMed2006

CT colonography: influence of 3D viewing and polyp candidate features on interpretation with computer-aided detection.

PURPOSE: To retrospectively determine if three-dimensional (3D) viewing improves radiologists' accuracy in classifying true-positive (TP) and false-positive (FP) polyp candidates identified with computer-aided detection (CAD) and to determine candidate polyp features that are associated with classification accuracy, with known polyps serving as the reference standard. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained; this study was HIPAA compliant. Forty-seven computed tomographic (CT) colonography data sets were obtained in 26 men and 10 women (age range, 42-76 years). Four radiologists classified 705 polyp candidates (53 TP candidates, 652 FP candidates) identified with CAD; initially, only two-dimensional images were used, but these were later supplemented with 3D rendering. Another radiologist unblinded to colonoscopy findings characterized the features of each candidate, assessed colon distention and preparation, and defined the true nature of FP candidates. Receiver operating characteristic curves were used to compare readers' performance, and repeated-measures analysis of variance was used to test features that affect interpretation. RESULTS: Use of 3D viewing improved classification accuracy for three readers and increased the area under the receiver operating characteristic curve to 0.96-0.97 (P<.001). For TP candidates, maximum polyp width (P=.038), polyp height (P=.019), and preparation (P=.004) significantly affected accuracy. For FP candidates, colonic segment (P=.007), attenuation (P<.001), surface smoothness (P<.001), distention (P=.034), preparation (P<.001), and true nature of candidate lesions (P<.001) significantly affected accuracy. CONCLUSION: Use of 3D viewing increases reader accuracy in the classification of polyp candidates identified with CAD. Polyp size and examination quality are significantly associated with accuracy.

Adult↗

PubMed2005

Hyped biomedical science or uncritical reporting? Press coverage of genomics (1992-2001) in Québec.

Genomics integrates the promises and perils of modern biomedical science. Canada and the province of Québec embarked late but aggressively in genomics research based on the 'discourse of promise' in which genomics is embedded. This did not prevent the emergence of a 'discourse of concerns', and debates on the wider meaning of genomics and on the risks related to genomics applications such as gene therapy and gene testing. Given this context, this study aims to understand the evolution of genomics press coverage from the early days up to the publication of the draft sequence of the human genome. Accordingly, we performed a press content analysis on 749 articles reporting genomics research in Québec from 1992 to 2001. We focused on coverage of benefits and ethical issues, tone, and differences in reporting practices between press agencies and journalists. Results show an increasing number of articles, a general decline in the proportion of articles featuring ethical issues, an increased focus on the economy, and greater optimism from 1992 to 2001. In comparison to articles written by journalists, articles signed by press agencies are more optimistic and less often feature ethical issues. Results are discussed following two non-exclusive interpretations: (1) the successes of genomics and its institutionalization in Québec and Canada brought hype and greater social acceptance, and (2) uncritical reporting practices have emerged under pressures for expedient and consumable writing. We are left with two concerns: given worldwide media concentration movements, what are the challenges for the dissemination of diversified and critical information in print media? And, given limited coverage of ethical issues, and concerns about bioethics being too narrowly focused, should public debates on frontier biomedical science be promoted to broaden the scope of biomedical ethics?

Bibliometrics↗

PubMed2005

Measurement of renal extraction fraction with contrast-enhanced CT.

Study was approved by the institutional review board, and informed patient consent was waived. A method for minimization of sources of variability in measuring single-kidney extraction fraction (EF) was determined retrospectively with contrast material-enhanced computed tomography (CT). Ten adults underwent CT of the kidneys; precontrast scans were obtained, followed by postcontrast scanning 2 minutes after contrast material injection. Single-kidney EF was then calculated for each patient with the formula EF = (CT(A) - CT(V))/(CT(A) - CT(PRE)), where CT(A) and CT(V) are the postcontrast CT values (in Hounsfield units) of the systemic blood and renal venous blood, respectively, and CT(PRE) is the precontrast CT value of the blood. Both conventional two-dimensional and volumetric three-dimensional regions of interest were used for determining mean CT values of the blood. By using the volumetric regions of interest, left and right renal EF values averaged 17.3% and 18.0%, respectively, for two observers, compared with the accepted value of 15%-20%. This latter technique also minimized right-left kidney and interobserver variability in the measurement of EF.

Adult↗

PubMed2005

Load- and practice-dependent increases in cerebro-cerebellar activation in verbal working memory: an fMRI study.

Load-dependent and practice-related changes in neocortical and cerebellar structures involved in verbal working memory (VWM) were investigated using functional MRI (fMRI) and a two alternative forced choice Sternberg paradigm. Using working memory loads ranging from 2 to 6 letters, regions exhibiting linear and quadratic trends in load-dependent activations were identified. Behaviorally, reaction time measurements revealed significant linear increases with increasing memory load, and significant decreases with increased task practice. Brain activations indicated a preponderance of linear load-dependent responses in both superior (lobule VI/Crus I) and inferior (lobule VIIB/VIIIA) cerebellar hemispheres, as well as in areas of neocortex including left precentral (BA 6), inferior frontal (BA 47), parahippocampal (BA 35), inferior parietal (BA 40), cingulate (BA 32), and right inferior and middle frontal (BA 46/47) regions. Fewer voxels exhibited quadratic without linear trends with the most prominent of these activations located in left inferior parietal (BA 40), precuneus, and parahippocampal regions. Analysis of load x session interactions revealed that right inferior cerebellar and left inferior parietal activations increased with practice, as did the correlations between activation in each region with reaction time, suggesting that changes in this cerebro-cerebellar network underlie practice-related increases in efficiency of VWM performance. These results replicate and extend our previous findings of fMRI activation in the cerebellum during VWM, and demonstrate predominately linear increases in cerebro-cerebellar activation with increasing memory load as well as changes in network function with increased task proficiency.

Adult↗

PubMed2005

Rates of reexcision for breast cancer after magnetic resonance imaging-guided bracket wire localization.

BACKGROUND: We performed this study to determine rates of close or transected cancer margins after magnetic resonance imaging-guided bracket wire localization for nonpalpable breast lesions. STUDY DESIGN: Of 243 women undergoing MRI-guided wire localizations, 26 had MRI bracket wire localization to excise either a known cancer (n = 19) or a suspicious MRI-detected lesion (n = 7). We reviewed patient age, preoperative diagnosis, operative intent, mammographic breast density, MRI lesion size, MRI enhancement curve and morphology, MRI Breast Imaging Reporting and Data System (BI-RADS) assessment code, number of bracket wires, and pathology size. We analyzed these findings for their relationship to obtaining clear margins at first operative excision. RESULTS: Twenty-one of 26 (81%) patients had cancer. Of 21 patients with cancer, 12 (57%) had negative margins at first excision and 9 (43%) had close/transected margins. MRI size > or = 4 cm was associated with a higher reexcision rate (7 of 9, 78%) than those < 4 cm (2 of 12, 17%) (p = 0.009). MRI BI-RADS score, enhancement curve, morphology, and preoperative core biopsy demonstrating ductal carcinoma in situ (DCIS) were not predictive of reexcision. The average number of wires used for bracketing increased with lesion size, but was not associated with improved outcomes. On pathology, cancer size was smaller in patients with negative margins (12 patients, 1.2 cm) than in those with close/transected margins (9 patients, 4.6 cm) (p < 0.001). Reexcision was based on close/transected margins involving DCIS alone (6, 67%), infiltrating ductal carcinoma and DCIS (2, 22%), or infiltrating ductal carcinoma alone (1, 11%). Reexcision pathology demonstrated DCIS (3, 33%), no residual cancer (5, 55%), and 1 patient was lost to followup (1, 11%). Interestingly, cancer patients who required reexcision were younger (p = 0.022), but breast density was not associated with reexcision. CONCLUSIONS: To our knowledge, this is the first report of MRI-guided bracket wire localization. Patients with MRI-detected lesions less than 4 cm had clear margins at first excision; larger MRI-detected lesions were more likely to have close/transected margins. Reexcision was often because of DCIS and was the only pathology found at reexcision, perhaps because MRI is more sensitive for detecting invasive carcinoma than DCIS.

Adult↗

PubMed2003

CT colonography: does improved z resolution help computer-aided polyp detection?

Multislice helical CT offers several retrospective choices of longitudinal (z) resolution at a given detector collimation setting. We sought to determine the effect of z resolution on the performance of a computer-aided colonic polyp detector, since a human reader and a computer-aided polyp detector may have optimal performances at different z resolutions. We ran a computer-aided polyp detection algorithm on phantom data sets as well as data obtained from a single patient. All data were reconstructed at various slice thicknesses ranging from 1.25 to 10 mm. We studied the performance of the detector at various ranges of polyp sizes using free-response receiver-operating characteristic analyses. We also studied contrast-to-noise ratios (CNR) as a function of slice thickness and polyp size. For the phantom data, reducing the slice thickness from 5 to 1.25 mm improves sensitivity from 84.5% to 98.3% (all polyps), from 61.4% to 95.5% (polyps in the range [0, 5) mm) and from 97.7% to 100% (polyps in the range [5, 10) mm) at a false positive rate of 20 per data set. For polyps larger than 10 mm, there is no significant improvement in detection sensitivity when slice thickness is reduced. CNRs showed expected behavior with slice thickness and polyp size, but in all cases remained high (> 4). The results for the patient data followed similar patterns to that of the phantom case. Thus we conclude that for this detector, the optimal slice thickness is dependent upon the size of the smallest polyps to be detected. For detection of polyps 10 mm and larger, reconstruction of 5 mm sections may be sufficient. Further study is required to generalize these results to a broader population of patients scanned on different scanners.

Colon↗

PubMed2003

Semiautomated segmentation of blood vessels using ellipse-overlap criteria: method and comparison to manual editing.

Two-dimensional intensity-based methods for the segmentation of blood vessels from computed-tomography-angiography data often result in spurious segments that originate from other objects whose intensity distributions overlap with those of the vessels. When segmented images include spurious segments, additional methods are required to select segments that belong to the target vessels. We describe a method that allows experts to select vessel segments from sequences of segmented images with little effort. Our method uses ellipse-overlap criteria to differentiate between segments that belong to different objects and are separated in plane but are connected in the through-plane direction. To validate our method, we used it to extract vessel regions from volumes that were segmented via analysis of isolabel-contour maps, and showed that the difference between the results of our method and manually-edited results was within inter-expert variability. Although the total editing duration for our method, which included user-interaction and computer processing, exceeded that of manual editing, the extent of user interaction required for our method was about a fifth of that required for manual editing.

Aneurysm↗

PubMedDate not supplied

Advertising, patient decision making, and self-referral for computed tomographic and magnetic resonance imaging.

BACKGROUND: Self-referred imaging is one of the latest health care services to be marketed directly to consumers. Most aspects of these services are unregulated, and little is known about the messages in advertising used to attract potential consumers. We conducted a detailed analysis of print advertisements and informational brochures for self-referred imaging with respect to themes, content, accuracy, and emotional valence. METHODS: Forty print advertisements from US newspapers around the country and 20 informational brochures were analyzed by 2 independent raters according to 7 major themes: health care technology; emotion, empowerment, and assurance; incentives; limited supporting evidence; popular appeal; statistics; and images. The Fisher exact test was used to identify significant differences in information content. RESULTS: Both the advertisements and the brochures emphasized health care and technology information and provided assurances of good health and incentives to self-refer. These materials also encouraged consumers to seek further information from company resources; virtually none referred to noncomplying sources of information or to the risks of having a scan. Images of people commonly portrayed European Americans. We found statistical differences between newspaper advertisements and mailed brochures for references to "prevalence of disease" (P<.001), "death" (P<.003), and "radiation" (P<.001). Statements lacking clear scientific evidence were identified in 38% of the advertisements (n = 15) and 25% of the brochures (n = 5). CONCLUSIONS: Direct-to-consumer marketing of self-referred imaging services, in both print advertisements and informational brochures, fails to provide prospective consumers with comprehensive balanced information vital to informed autonomous decision making. Professional guidelines and oversight for advertising and promotion of these services are needed.

Advertising↗

PubMedDate not supplied

Computed tomography colonography: feasibility of computer-aided polyp detection in a "first reader" paradigm.

OBJECTIVE: : To determine the feasibility of a computer-aided detection (CAD) algorithm as the "first reader" in computed tomography colonography (CTC). METHODS: : In phase 1 of a 2-part blind trial, we measured the performance of 3 radiologists reading 41 CTC studies without CAD. In phase 2, readers interpreted the same cases using a CAD list of 30 potential polyps. RESULTS: : Unassisted readers detected, on average, 63% of polyps > or =10 mm in diameter. Using CAD, the sensitivity was 74% (not statistically different). Per-patient analysis showed a trend toward increased sensitivity for polyps > or =10 mm in diameter, from 73% to 90% with CAD (not significant) without decreasing specificity. Computer-aided detection significantly decreased interobserver variability (P = 0.017). Average time to detection of the first polyp decreased significantly with CAD, whereas total reading case reading time was unchanged. CONCLUSION: : Computer-aided detection as a first reader in CTC was associated with similar per-polyp and per-patient detection sensitivity to unassisted reading. Computer-aided detection decreased interobserver variability and reduced the time required to detect the first polyp.

Adult↗