Biomedical subjects

Rogier E van Gelder

Publications and source records attributed to Rogier E van Gelder.

8 recordsLinked to original sources

PubMed2006

A comparison of primary two- and three-dimensional methods to review CT colonography.

The aim of our study was to compare primary three-dimensional (3D) and primary two-dimensional (2D) review methods for CT colonography with regard to polyp detection and perceptive errors. CT colonography studies of 77 patients were read twice by three reviewers, first with a primary 3D method and then with a primary 2D method. Mean numbers of true and false positives, patient sensitivity and specificity and perceptive errors were calculated with colonoscopy as a reference standard. A perceptive error was made if a polyp was not detected by all reviewers. Mean sensitivity for large (> or = 10 mm) polyps for primary 3D and 2D review was 81% (14.7/18) and 70%(12.7/18), respectively (p-values > or = 0.25). Mean numbers of large false positives for primary 3D and 2D were 8.3 and 5.3, respectively. With primary 3D and 2D review 1 and 6 perceptive errors, respectively, were made in 18 large polyps (p = 0.06). For medium-sized (6-9 mm) polyps these values were for primary 3D and 2D, respectively: mean sensitivity: 67%(11.3/17) and 61%(10.3/17; p-values > or = 0.45), number of false positives: 33.3 and 15.6, and perceptive errors : 4 and 6 (p = 0.53). No significant differences were found in the detection of large and medium-sized polyps between primary 3D and 2D review.

Adult↗

PubMed2006

Effective radiation doses in CT colonography: results of an inventory among research institutions.

The purpose of this study was to estimate the effective dose that is currently used in CT colonography using scan parameters that were collected for this purpose, and to investigate trends in time. PubMed was systematically searched from 1996 until January 2004 for studies investigating CT colonography. Research institutions were contacted and asked for their current scan protocol. Thirty-six institutions published 74 studies. Twenty-eight of the 36 institutions provided their current protocol. The median effective dose in 2004 was 5.1 mSv (range 1.2-11.7 mSv) per position. Most institutions (93%) scan in both the supine and prone positions. The median mAs value was 67 mAs (range 20-200), median collimation was 2.5 mm (range 0.75-5). From 1996 until 2004 a significant decrease in mAs and collimation (P=0.006, P<0.0001, respectively) was observed, while institutions that used a multislice scanner increased (P<0.0001). The effective dose remained constant (P=0.76). In 2004 the median effective dose for a complete CT colonography was 10.2 mSv. Despite the increasing use of multislice scanners, which are slightly less dose-efficient, the median effective dose remained approximately constant between 1996 and 2004. This is mainly caused by the use of lower mAs settings.

Academies and Institutes↗

PubMed2005

Colonography by computed tomography.

Computed tomographic colonography ('virtual colonoscopy') has shown promising results in the detection of large (> or = 10 mm) polyps in populations with a high prevalence of polyps. Recent studies in low prevalence populations, however, show variable results in sensitivity, ranging from 55% to 94% for the detection of patients with polyps measuring 10 mm or longer. Therefore questions have been raised about computed tomographic colonography as a screening method, probably the most valuable use of this technique. This article describes possible causes of these remarkable differences as well as advances in computed tomographic colonography.

Attitude to Health↗

PubMed2004

CT colonography and colonoscopy: assessment of patient preference in a 5-week follow-up study.

PURPOSE: To prospectively evaluate short- and midterm patient preference of computed tomographic (CT) colonography relative to colonoscopy in patients at increased risk for colorectal cancer and to elucidate determinants of preference. MATERIALS AND METHODS: Consecutive patients at increased risk for colorectal cancer underwent CT colonography prior to scheduled colonoscopy. Patient experience and preference were assessed both directly after the examinations and 5 weeks after the examinations. Differences in pain, embarrassment, discomfort, and preference were assessed with the Wilcoxon signed rank sum test or a binomial test. Potential determinants of preference were investigated with logistic regression analyses. RESULTS: Data for 249 patients were included. Fewer patients experienced severe or extreme pain during CT colonography (seven [3%] of 245) than during colonoscopy (81 [34%] of 241) (P < .001). Directly after both examinations, 168 (71%) of 236 patients preferred CT colonography; 5 weeks later, 141 (61%) of 233 patients preferred CT colonography (P < .001). Initially, a painful colonoscopy examination (odds ratio, 0.17; 95% confidence interval [CI]: 0.08, 0.38) was a determinant of CT colonography preference. Similarly, a painful (odds ratio, 3.70; 95% CI: 1.54, 8.92) or an embarrassing (odds ratio, 4.46; 95% CI: 1.18, 16.88) CT colonography examination was a determinant of colonoscopy preference. After 5 weeks, the presence of polyps emerged as a determinant of colonoscopy preference (odds ratio, 1.94; 95% CI: 1.02, 3.70), while the role of experiences waned. CONCLUSION: Patients preferred CT colonography to colonoscopy; however, this preference decreased in time, while outcome considerations gradually replaced temporary experiences of inconvenience.

Aged↗

PubMed2004

CT colonography: feasibility of substantial dose reduction--comparison of medium to very low doses in identical patients.

In a feasibility study, the authors compared polyp detection and interobserver variability at computed tomographic (CT) colonography in 15 patients with doses ranging from medium to very low (12.00-0.05 mSv). At levels down to 2% of the medium dose, the mean detection of polyps 5 mm or larger remained at least 74%, while the number of false-positive results decreased and the interobserver agreement remained constant. Initial observations indicate that it is feasible to reduce the radiation dose required for CT colonography. Further studies are needed, however, to investigate the clinical value of very low-dose CT colonography.

Adult↗

PubMed2004

Admission blood glucose level as risk indicator of death after myocardial infarction in patients with and without diabetes mellitus.

BACKGROUND: High admission blood glucose levels after acute myocardial infarction (AMI) are common and associated with an increased risk of death in subjects with and without known diabetes. Recent data indicate a high prevalence of abnormal glucose metabolism in patients with unknown diabetes at the time of AMI. We investigated the predictive value of admission blood glucose levels after AMI for long-term prognosis in patients with and without previously diagnosed diabetes mellitus, particularly in those with unknown diabetes but with blood glucose levels in the diabetic range. METHODS: In a retrospective study with prospective follow-up, 846 patients (737 without and 109 with known diabetes) were eligible for follow-up during a median of 50 months (range, 0-93 months). RESULTS: During follow-up, 208 nondiabetic patients (28.2%) and 47 diabetic patients (43.1%) died (P =.002). An increase of 18 mg/dL (1 mmol/L) in glucose level was associated with a 4% increase of mortality risk in nondiabetic patients and 5% in diabetic patients (both P<.05). Of the 737 previously nondiabetic subjects, 101 had admission blood glucose levels of 200 mg/dL (11.1 mmol/L) or more, and mortality in these patients was comparable to that in patients who had established diabetes (42.6% vs 43.1%). CONCLUSIONS: Admission blood glucose level after AMI is an independent predictor of long-term mortality in patients with and without known diabetes. Subjects with unknown diabetes and admission glucose levels of 200 mg/dL (11.1 mmol/L) or more after AMI have mortality rates comparable to those of subjects with established diabetes. Admission blood glucose level may serve to identify subjects at high long-term mortality risk, in particular among those with unknown diabetes.

Aged↗

PubMed2003

Three-dimensional display modes for CT colonography: conventional 3D virtual colonoscopy versus unfolded cube projection.

The authors compared a conventional two-directional three-dimensional (3D) display for computed tomography (CT) colonography with an alternative method they developed on the basis of time efficiency and surface visibility. With the conventional technique, 3D ante- and retrograde cine loops were obtained (hereafter, conventional 3D). With the alternative method, six projections were obtained at 90 degrees viewing angles (unfolded cube display). Mean evaluation time per patient with the conventional 3D display was significantly longer than that with the unfolded cube display. With the conventional 3D method, 93.8% of the colon surface came into view; with the unfolded cube method, 99.5% of the colon surface came into view. Sensitivity and specificity were not significantly different between the two methods. Agreements between observers were kappa = 0.605 for conventional 3D display and kappa = 0.692 for unfolded cube display. Consequently, the latter method enhances the 3D endoluminal display with improved time efficiency and higher surface visibility.

Colonography, Computed Tomographic↗

PubMed2002

CT colonography at different radiation dose levels: feasibility of dose reduction.

PURPOSE: To investigate the sensitivity and specificity of polyp detection and the image quality of computed tomographic (CT) colonography at different radiation dose levels and to study effective doses reported in literature on CT colonography. MATERIALS AND METHODS: CT colonography and colonoscopy were performed with 100 mAs in 50 consecutive patients at high risk for colorectal cancer; 50- and 30-mAs CT colonographic examinations were simulated with controlled addition of noise to raw transmission measurements. One radiologist randomly evaluated all original and simulated images for the presence of polyps and scored image quality. Differences in image quality were assessed with the Wilcoxon rank test. Scan protocols from the literature and recent (unpublished) updates were collected. RESULTS: In nine of 10 patients with polyps 5 mm in diameter or larger (sensitivity, 90%) and in seven of 17 patients with polyps smaller than 5 mm, polyps were correctly identified with CT colonography at all dose levels. Specificity for patients without polyps 5 mm or larger was 53%-60% at all dose levels and for patients without any polyps was 26% (at 100 and 50 mAs) and 48% (at 30 mAs). Image quality decreased significantly as the dose level decreased. The median effective doses (supine and prone positions) calculated from protocols reported in the literature and updates were 7.8 and 8.8 mSv, respectively. CONCLUSION: Although image quality decreases significantly at 30 mAs (3.6 mSv), polyp detection remains unimpaired. The median dose for CT colonography at institutions that perform CT colonographic research is currently 8.8 mSv.

Adult↗