Biomedical subjects

F Leland Thaete

Publications and source records attributed to F Leland Thaete.

7 recordsLinked to original sources

PubMed2006

The effect of image display size on observer performance an assessment of variance components.

RATIONALE AND OBJECTIVE: Our goal was to investigate the effect of the displayed image size on variance components during the performance of an observer performance study to detect masses on abdominal computed tomography (CT) examinations. MATERIALS AND METHODS: A previously performed receiver operating characteristic (ROC) study with eight observers to detect abdominal masses on 166 CT examinations was reanalyzed to assess variance components when comparing two similar modes with displayed image sizes varying by a factor of 2. Case, mode, and reader-related variance components were estimated for the group of eight observers and subsets of readers after excluding each of the participants. RESULTS: There was no significant difference in the average area under the ROC curves between the two modes using the two image sizes (P > .05). Reader and reader-by-case variability were substantially larger for the mode displaying enlarged images for the group and all subsets formed by excluding a single reader. Reader variability was affected by one observer who actually performed better with the enlarged images. CONCLUSION: Sequential viewing of enlarged CT images for the detection of abdominal masses did not improve performance and increased reader variability.

Abdominal Neoplasms↗

PubMed2005

Insulin-like growth factor-I and insulin are associated with the presence and advancement of adenomatous polyps.

BACKGROUND & AIMS: Insulin and insulin-like growth factor-I (IGF-I) affect proliferation, differentiation, and apoptosis and are potential risk factors for colorectal cancer (CRC). Visceral obesity, possibly via hyperinsulinemia, has also been linked to CRC risk. We evaluated the relationship of insulin, IGF-I, insulin-like growth factor binding protein (IGFBP) 3, and visceral adipose tissue (VAT) in subjects with adenomatous polyps, the precursor lesion of colorectal cancer. METHODS: Participants were asymptomatic subjects who underwent screening flexible sigmoidoscopy (FSG) within the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Subjects underwent single-slice, computerized tomography scanning to measure VAT and serum fasting insulin, IGF-I, and IGFBP-3 measurements. RESULTS: Four hundred fifty-eight subjects were enrolled, of which 202 subjects had an adenoma, 70 of which were an advanced adenoma. IGF-I (P = .02), IGF-I/IGFBP-3 ratio (P = .003), and insulin (P = .02) were significantly increased in subjects with adenomas compared with controls. In an unadjusted logistic regression analysis using sex-specific quartile cut points, subjects in quartile 4 in comparison with quartile 1 of IGF-I (odds ratio [OR] = 1.7; [95% CI: 1.0-2.9], Ptrend = .03), IGF-I/IGFBP-3 ratio (OR = 1.9 [95% CI: 1.1-3.3], Ptrend = .01), and insulin (OR = 2.1 [95% CI: 1.2-3.6], Ptrend = .04) were at increased risk of adenoma. When limiting the case group to advanced adenomas, the effect was more pronounced: IGF-I (OR = 2.8 [95% CI: 1.3-6.2], Ptrend = .006), IGF-I/IGFBP-3 ratio (OR = 2.3, [95% CI: 1.0-5.2], Ptrend = .04), and insulin (OR = 2.3 [95% CI: 1.1-4.9], Ptrend = .14). Visceral adipose tissue was not associated with adenoma risk. CONCLUSIONS: Levels of IGF-I, ratio of IGF-I/IGFBP-3, and insulin are associated with adenomas and even more so with advanced adenomas. These data support the hypothesis that insulin and IGF-I may contribute to the development and advancement of adenomatous polyps.

Adenomatous Polyps↗

PubMed2004

Relationship of visceral adipose tissue to recurrence of adenomatous polyps.

OBJECTIVES: Insulin is a growth factor for colorectal cancer. Visceral adipose tissue (VAT) is strongly associated with insulin levels, and insulin and visceral obesity have been associated in cohort studies with colorectal cancer. The aim of this investigation was to determine whether VAT is associated with recurrence of adenomatous polyps, the precursor to colorectal cancer. METHODS: As an ancillary study to the Polyp Prevention Trial, a randomized clinical trial that evaluated the effect of a low-fat, high-fiber, high vegetable and fruit diet on adenomatous polyp recurrence, subjects at one clinical center underwent measurement of VAT with a single-slice CT scan through the L4-L5 interspace. The scan was performed around the time of the subject's year 4 colonoscopy that determined adenoma recurrence. RESULTS: Of 119 subjects, 44 of 84 men (52%) and 16 of 35 women (46%) had a recurrent adenoma (p= 0.51). Body mass index (BMI) and weight at baseline and at year 4 colonoscopy were unrelated to adenoma recurrence. In a multivariate model including visceral fat quartile, remote history of polyps, gender, age, and randomization group, only remote history of polyps was statistically significantly associated with recurrent adenoma with a relative risk of 4.6 (95% CI 1.7, 12.4, p= 0.001). There was no consistent monotonic trend of increased or decreased risk of recurrence as one ascended quartiles of adipose tissue for visceral, subcutaneous, or total abdominal fat. CONCLUSION: In this study, no association between visceral adipose tissue and adenomatous polyp recurrence was observed. Further study and exploration of the role of VAT in adenoma progression is required.

Adenomatous Polyps↗

PubMed2003

Rosai-Dorfman disease of the pleura: a rare extranodal presentation.

We present a case of Rosai-Dorfman disease (sinus histiocytosis with massive lymphadenopathy) manifesting primarily as a pleural disease without involvement of the lung parenchyma. The patient is an 81-year-old man who presented with increasing shortness of breath. Radiographic studies revealed a large loculated left-sided pleural effusion and parietal pleural thickening. Video-assisted thoracoscopic biopsy of the pleura showed the characteristic S100-positive histiocytes exhibiting emperipolesis. In this rare case of pleural Rosai-Dorfman disease, the extensive involvement of the pleural lymphatics by the characteristic histiocytes appears to have been responsible for the pleural effusion.

Aged↗

PubMed2003

Prevalence effect in a laboratory environment.

PURPOSE: To measure observer performance at various levels of prevalence. MATERIALS AND METHODS: A multiobserver multiabnormality receiver operating characteristic (ROC) study to assess the effect of prevalence on observer performance was conducted. Fourteen observers, including eight faculty members, two fellows, and four residents, interpreted 1,632 posteroanterior chest images with five prevalence levels by using a nested study design. Performance comparisons were accomplished by using a multireader multicase approach to assess the effect of prevalence from 28% (69 of 249) to 2% (31 of 1,577) on diagnostic accuracy. The mean times required to review and report a case were analyzed and compared for different levels of prevalence and readers' experience. RESULTS: Area under the ROC curve demonstrated that, with the study experimental conditions, no significant effect could be measured as a function of prevalence (P >.05) for any abnormality, group of cases, or readers. There were no significant differences (P >.05) in the mean times required to review and report cases at different prevalence levels and with different groups of readers. CONCLUSION: The consistency in the results and the size of this study suggest that with laboratory conditions, if a prevalence effect exists, it is quite small in magnitude; hence, it will not likely alter conclusions derived from such studies.

Laboratories↗

PubMed2002

Association of physical activity and visceral adipose tissue in older women and men.

OBJECTIVE: Physical inactivity, abdominal fat, and age are known risk factors for diabetes, cardiovascular disease, and certain cancers. Previous evidence supports an inverse relationship between physical activity (PA) and abdominal fat estimated by waist circumference. However, few investigations used computed tomography (CAT) scanning for precise measures of abdominal fat. RESEARCH METHODS AND PROCEDURES: Sixty-five female and 106 male (age, 64.5 +/- 5.2 years) participants in the Prostate, Lung, Colon and Ovarian Cancer Screening Trial underwent a cross-sectional L4-L5 CAT scan to differentiate visceral adipose tissue (VAT). Subjects were also interviewed by phone to determine PA and physical difficulties (PD). RESULTS: Women had lower VAT (170 +/- 84 vs. 205 +/- 95 cm(2), p = 0.014), lower VAT/total fat (29.9 +/- 7.2% vs. 42.6 +/- 10.2%, p < 0.001), and higher total fat (596 +/- 385 vs. 482 +/- 183 cm(2), p = 0.010) than men. PA was inversely correlated to VAT (r = -0.164, p = 0.034) and total fat (r = -0.231, p = 0.003) in men and women. Those who reported a PD had higher VAT (249 vs. 180 cm(2), p < 0.001) and total fat (652 vs. 500 cm(2), p = 0.008). Multiple regression analysis indicated total PA and PD were independently associated to VAT and total fat. DISCUSSION: This investigation suggests a beneficial effect of PA and a negative influence of PD on abdominal fat accumulation. Although the cross-sectional design limits cause-effect designations, these results are consistent with other studies showing PA/abdominal fat relation.

Abdomen↗

PubMed2002

Lack of association between adipose tissue distribution and IGF-1 and IGFBP-3 in men and women.

Insulin, insulin-like growth factor-1 (IGF-1), IGF binding protein-3 (IGFBP-3), and obesity, and in particular visceral obesity, are putative cancer risk factors. Little is known, however, about the relationship between IGFs and obesity. We investigated the relationship between adipose tissue distribution and IGF-1 and IGFBP-3. Single-slice abdominal computed tomography scanning through the L4-L5 interspace was used to measure visceral adipose tissue (VAT) and subcutaneous adipose tissue (SQAT) in 432 community-based subjects (267 men, 165 women; ages, 55-77), participating in a cancer screening trial. Insulin, IGF-1, IGFBP-3, and the ratio of IGF-1:IGFBP-3, measured by radioimmunoassay, were compared with age, body mass index, absolute and relative VAT and SQAT, and total abdominal fat. We found that men had a higher mean IGF-1 (129.5 versus 108.9 ng/ml; P < 0.0001) and more VAT (201.5 cm(3) versus 166.6 cm(3); P < 0.0001) than women. In men and women, there was no correlation between IGF-1, IGFBP-3, or the ratio of IGF-1:IGFBP-3 with body mass index, total fat, VAT or SQAT, or fasting insulin. In contrast, fasting insulin was highly correlated to all measures of obesity (P = 0.0001). We conclude that obesity, adipose tissue distribution, and in particular VAT are not correlated with IGF-1, IGFBP-3, or the molar ratio of IGF-1:IGFBP-3. The lack of association between obesity and the IGF-1 axis suggests that the IGF-1 axis is not a likely mediator between VAT and disease.

Adipose Tissue↗