HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Arac, M. Articles by Isik, S. Search for Related Content PubMed PubMed Citation Articles by Arac, M. Articles by Isik, S.

Lung at Thin-Section CT: Influence of Multiple-Segment Reconstruction on Image Quality¹

¹ From the Department of Radiology, Gazi University School of Medicine, Kat, Besevler, Ankara, Turkey. Received May 29, 2002; revision requested July 30; final revision received January 31, 2003; accepted May 14. Address correspondence to M.A. (e-mail: meharac@yahoo.com).

View larger version (29K): [in a new window]   Figure 1a. Diagrams show relationship between cardiac cycle and image reconstruction in a 1-second clockwise rotation. Inner circles represent the scanning period; the starting points (S1-S6) of data acquisition for each segment image are marked. Outer circles represent the two phases of cardiac cycle for heart rate of 83 beats per minute (220-msec systole and 500-msec diastole per cycle). D1 = first diastole, D2 = second diastole. (a) Best case scenario: Scanning is started simultaneously with cardiac diastole (D1). In this case, one systole occurs during the 1-second scan time. The sixth segment is free of systole; therefore, cardiac-motion artifacts are reduced. (b) Worst case scenario: Scanning is started simultaneously with cardiac systole (SY1). In this case, two systoles (SY1 and SY2) occur during the 1-second scan time. There is no way to reconstruct a segment image that is completely free of systole. Even in this case, however, the second segment contains a smaller part of systole than is depicted on the 1-second scan, Therefore, the resultant image is less affected by cardiac-motion artifacts.

View larger version (30K): [in a new window]   Figure 1b. Diagrams show relationship between cardiac cycle and image reconstruction in a 1-second clockwise rotation. Inner circles represent the scanning period; the starting points (S1-S6) of data acquisition for each segment image are marked. Outer circles represent the two phases of cardiac cycle for heart rate of 83 beats per minute (220-msec systole and 500-msec diastole per cycle). D1 = first diastole, D2 = second diastole. (a) Best case scenario: Scanning is started simultaneously with cardiac diastole (D1). In this case, one systole occurs during the 1-second scan time. The sixth segment is free of systole; therefore, cardiac-motion artifacts are reduced. (b) Worst case scenario: Scanning is started simultaneously with cardiac systole (SY1). In this case, two systoles (SY1 and SY2) occur during the 1-second scan time. There is no way to reconstruct a segment image that is completely free of systole. Even in this case, however, the second segment contains a smaller part of systole than is depicted on the 1-second scan, Therefore, the resultant image is less affected by cardiac-motion artifacts.

View larger version (53K): [in a new window]   Figure 2. In a 38-year-old female patient with known bronchiectasis, images were obtained at anatomic plane where inferior vena cava opens to right atrium. Top: On transverse 360° thin-section CT scan reconstructed with bone algorithm, blurred cardiac margin, double-line artifacts of fissure (curved arrow) and vessels, and distortion of bronchi (straight arrow) mimic appearance of bronchiectasis. Bottom: On segment image reconstructed with lung algorithm, cardiac border is delineated clearly and outline of fissure is sharp, but star artifacts as a result of cardiac pulsatility are not totally eliminated.

View larger version (90K): [in a new window]   Figure 3. Images in a 37-year-old male patient with cystic bronchiectasis. Imaging level is cardiac "four-chamber" plane. Left: On transverse 360° thin-section CT image reconstructed with bone algorithm, outlines of cystic bronchiectasis are relatively sharp in peripheral lung parenchyma but are severely distorted in paracardiac region (arrow). Right: On segment image reconstructed with lung algorithm, outlines of cystic bronchiectatic changes are delineated clearly in paracardiac region, as well as in peripheral lung parenchyma. Note that cardiac margin is sharper on the right image than on the left.

View larger version (29K): [in a new window]   Figure 4. Bar graph shows mean image quality scores assigned by different observers to thin-section CT images reconstructed with the three algorithms. Black bars = 360° thin-section CT images reconstructed with bone algorithm. Gray bars = 360° thin-section CT images reconstructed with lung algorithm. White bars = multiple-segment reconstructed images.

View larger version (56K): [in a new window]   Figure 5. Images in a 35-year-old female patient suspected of having bronchiectasis but without radiologic findings in the left paracardiac region. Imaging plane is cardiac four-chamber level. Left: A 360° image reconstructed with bone algorithm. Middle: A 360° image reconstructed with lung algorithm. Right: Segment image reconstructed with lung algorithm. Note clear delineation of cardiac border (black arrow) on right image compared with that on left and middle images. Double-image artifacts due to distorted pulmonary fissure and vessels in left and middle images were eliminated (white arrow) with segment reconstruction.

View larger version (116K): [in a new window]   Figure 6. (A-F) Six segment reconstructions obtained in the same patient and at the same level as in Figure 5. Note that not all images are free of cardiac-motion artifacts. A is the best image in terms of reduction of cardiac-motion artifacts, whereas C and D are the worst images, with blurred cardiac margins and distorted pulmonary vessels.