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Alec J Megibow

Publications and source records attributed to Alec J Megibow.

4 recordsLinked to original sources
PubMed2002

Computed tomography diagnosis utilizing compressed image data: an ROC analysis using acute appendicitis as a model.

Using receiver-operating characteristic (ROC) methodology, the ability to diagnose acute appendicitis with computed tomography (CT) images displayed at varying levels of lossy compression was evaluated. Nine sequential images over the ileocecal region were obtained from 53 consecutive patients with right lower quadrant pain who were clinically suspected to have acute appendicitis. Thirty were proven surgically to have acute appendicitis, alternative diagnoses confirmed in 23. The image sets were subjected to a lossy wavelet-based compression algorithm "Embedded Predictive Wavelet Image Coder" (EPWIC). Compression levels were: none, 8:1, 16:1, and 24:1, resulting in 4 sets of images per patient. Image sets were randomized and evaluated separately by 4 body radiologists on a 1,024 x 768-pixel SVGA color PC monitor in 512 x 512 format. The readers were aware of the clinical suspicion of appendicitis but were unaware of the positive fraction of cases. Individual and combined reader ROC and c2 analyses of sensitivity, specificity, and accuracy were determined. For all readers, sensitivity decreases at 16:1 and 24:1 levels (P <0.01, P <0.001, respectively). Accuracy decreased at 24:1 levels (P <0.01). Specificity was unaffected. By ROC analysis there was statistically significantly decreased area under the curve at 24:1 levels (P <0.02) as compared with uncompressed images. Finite levels of lossy wavelet compression may be applied to CT images without compromising diagnostic performance.

Acute Disease↗
PubMed2002

Colorectal neoplasms: prospective comparison of thin-section low-dose multi-detector row CT colonography and conventional colonoscopy for detection.

PURPOSE: To prospectively compare thin-section low-dose multi-detector row computed tomographic (CT) colonography with conventional colonoscopy for the detection of colorectal neoplasms. MATERIALS AND METHODS: One hundred five patients underwent CT colonography immediately before colonoscopy. Supine and prone CT colonographic acquisitions to image the region during a 30-second breath hold were performed. CT colonographic images were prospectively interpreted for the presence, location, size, and morphologic features of polyps. The time of image interpretation was noted. Sensitivity, specificity, and positive and negative predictive values of CT colonography were calculated, with 95% CIs, by using colonoscopic findings as the reference standard. The weighted CT dose index was calculated on the basis of measurements in a standard body phantom. Effective dose was calculated by using commercially available software. RESULTS: Median CT data interpretation time was 12 minutes. One hundred thirty-two polyps in 59 patients were identified at colonoscopy; no polyps were detected in 46 patients. Sensitivities for detection of polyps smaller than 5 mm, 6-9 mm, and larger than 10 mm in diameter were 12% (11 of 91 polyps), 70% (19 of 27 polyps), and 93% (13 of 14 polyps), respectively. Estimated overall specificity was 97.7% (515 of 527 imaging results). The total weighted CT dose index for combined supine and prone CT colonography was 11.4 mGy. The effective doses for combined CT colonography were 5.0 mSv and 7.8 mSv for men and women, respectively. CONCLUSION: Low-dose multi-detector row CT colonography has excellent sensitivity and specificity for detection of colorectal neoplasms 10 mm and larger.

Aged↗
PubMed2002

Dual-phase versus single-phase helical CT to detect and assess resectability of pancreatic carcinoma.

OBJECTIVE: The aim of this study was to compare dual-phase and single-phase helical CT for the detection and assessment of resectability of pancreatic adenocarcinoma. SUBJECTS AND METHODS: We studied 60 patients (31 men, 29 women; age range, 31-84 years; mean age, 62 years) with suspected pancreatic malignancy. Patients were randomly assigned to one of two groups. For group A (n = 30), unenhanced scans through the liver and pancreas were followed by two separate acquisitions (dual-phase) at 20-25 and at 60-80 sec after IV contrast administration. For group B (n = 30), unenhanced scans were followed by one set of scans (single-phase) acquired caudocranially (from the inferior hepatic margin to the diaphragm) starting 50 sec after IV contrast administration. Two observers independently scored images for the presence of tumor and for assessment of tumor resectability. RESULTS: Comparison of dual-phase versus single-phase helical CT for tumor detection showed a diagnostic accuracy for observer 1 of 87% and 90%, respectively, and for observer 2, of 90% and 87%, respectively. For both helical CT techniques, the overall agreement between the two observers was 83% (kappa = 0.73 +/- 0.03) for single-phase helical CT and 90% (kappa = 0.89 +/- 0.03) for dual-phase helical CT. The assessment of resectability was affected by the low number of resectable tumors (n = 8). CONCLUSION: Single-phase helical CT is effective for the diagnosis and assessment of resectability of patients with suspected pancreatic carcinoma. Advantages are the lower radiation dose and fewer images to film and store.

Adenocarcinoma↗