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 Wessling, J. Articles by Heindel, W. Search for Related Content PubMed PubMed Citation Articles by Wessling, J. Articles by Heindel, W.

CT Colonography: Protocol Optimization with Multi–Detector Row CT—Study in an Anthropomorphic Colon Phantom¹

¹ From the Department of Clinical Radiology, University of Muenster, Albert-Schweitzer-Strasse 33, 48 149 Muenster, Germany. Received August 1, 2002; revision requested October 1; final revision received December 9; accepted January 2, 2003. Address correspondence to J.W. (e-mail: weslingj@uni-muenster.de).

View larger version (119K): [in a new window]   Figure 1a. (a) Endoluminal view shows five spherical phantom polyps along the xy and the z axis. Polyp size was 2, 4, 6, 8, and 12 mm. (b) Surface view shows colon phantom submerged in fluid-filled acrylic body phantom. (c) Transverse view of body and colon phantom. For objective assessment of image noise, a region of interest was placed at the 3-o’clock position of the water-phantom for each protocol.

View larger version (104K): [in a new window]   Figure 1b. (a) Endoluminal view shows five spherical phantom polyps along the xy and the z axis. Polyp size was 2, 4, 6, 8, and 12 mm. (b) Surface view shows colon phantom submerged in fluid-filled acrylic body phantom. (c) Transverse view of body and colon phantom. For objective assessment of image noise, a region of interest was placed at the 3-o’clock position of the water-phantom for each protocol.

View larger version (101K): [in a new window]   Figure 1c. (a) Endoluminal view shows five spherical phantom polyps along the xy and the z axis. Polyp size was 2, 4, 6, 8, and 12 mm. (b) Surface view shows colon phantom submerged in fluid-filled acrylic body phantom. (c) Transverse view of body and colon phantom. For objective assessment of image noise, a region of interest was placed at the 3-o’clock position of the water-phantom for each protocol.

View larger version (35K): [in a new window]   Figure 2a. (a) Size-dependent polyp depiction compared with section thickness and detector collimation. Protocol numbers are in parentheses at the top: 1-4 = 4 x 1.0-mm detector collimation, 11 = 4 x 2.5-mm detector collimation. Good to excellent depiction of polyps 8 mm or larger was achieved independently of section thickness or detector collimation. Depiction of polyps 6 mm or smaller depended mainly on the reconstructed section thickness. Depiction of small polyps was superior (protocol 3 and 11) when 4 x 1.0-mm detector collimation was used for the same reconstructed section thickness (3 mm). (b) Size-dependent polyp depiction compared with radiation dose. Protocol numbers in parentheses: 1, 5-10 = 4 x 1-mm detector collimation. Depiction of polyps 8mm or larger was not influenced by tube current reduction when 4 x 1.0-mm detector collimation and 1.25-mm section thickness were used for each protocol. Depiction of smaller polyps deteriorates with reduced tube current but remains possible, even for low-dose (10-mAs) protocols. (c) Size-dependent polyp depiction compared with radiation dose. Protocol numbers in parentheses: 11-15 = 4 x 2.5-mm detector collimation. Depiction of polyps 8 mm or larger was not influenced by tube current reduction when 2.5-mm detector collimation and 3-mm section thickness were used. The effects of tube current reduction were more evident when compared with protocols that used 4 x 1.0-mm detector collimation for depiction of smaller polyps. Polyps smaller than 8 mm were not depicted, even by using the lowest (10-mAs) setting possible. (d) Longitudinal distortion of polyps and rippling artifacts depending on section thickness. Longitudinal distortion and rippling artifacts increased with increasing section thickness and use of broader detector collimation. (e) Sum score of all protocols. Protocols that use 4 x 1.0-mm detector collimation were superior to those that use 4 x 2.5-mm collimation. Low-dose thin-section protocols (protocols 5-10) tended to be superior to high-dose protocols with 4 x 2.5-mm detector collimation (protocol 11) and were only slightly different from high-dose thin-section protocols (protocol 1).

View larger version (53K): [in a new window]   Figure 2b. (a) Size-dependent polyp depiction compared with section thickness and detector collimation. Protocol numbers are in parentheses at the top: 1-4 = 4 x 1.0-mm detector collimation, 11 = 4 x 2.5-mm detector collimation. Good to excellent depiction of polyps 8 mm or larger was achieved independently of section thickness or detector collimation. Depiction of polyps 6 mm or smaller depended mainly on the reconstructed section thickness. Depiction of small polyps was superior (protocol 3 and 11) when 4 x 1.0-mm detector collimation was used for the same reconstructed section thickness (3 mm). (b) Size-dependent polyp depiction compared with radiation dose. Protocol numbers in parentheses: 1, 5-10 = 4 x 1-mm detector collimation. Depiction of polyps 8mm or larger was not influenced by tube current reduction when 4 x 1.0-mm detector collimation and 1.25-mm section thickness were used for each protocol. Depiction of smaller polyps deteriorates with reduced tube current but remains possible, even for low-dose (10-mAs) protocols. (c) Size-dependent polyp depiction compared with radiation dose. Protocol numbers in parentheses: 11-15 = 4 x 2.5-mm detector collimation. Depiction of polyps 8 mm or larger was not influenced by tube current reduction when 2.5-mm detector collimation and 3-mm section thickness were used. The effects of tube current reduction were more evident when compared with protocols that used 4 x 1.0-mm detector collimation for depiction of smaller polyps. Polyps smaller than 8 mm were not depicted, even by using the lowest (10-mAs) setting possible. (d) Longitudinal distortion of polyps and rippling artifacts depending on section thickness. Longitudinal distortion and rippling artifacts increased with increasing section thickness and use of broader detector collimation. (e) Sum score of all protocols. Protocols that use 4 x 1.0-mm detector collimation were superior to those that use 4 x 2.5-mm collimation. Low-dose thin-section protocols (protocols 5-10) tended to be superior to high-dose protocols with 4 x 2.5-mm detector collimation (protocol 11) and were only slightly different from high-dose thin-section protocols (protocol 1).

View larger version (32K): [in a new window]   Figure 2c. (a) Size-dependent polyp depiction compared with section thickness and detector collimation. Protocol numbers are in parentheses at the top: 1-4 = 4 x 1.0-mm detector collimation, 11 = 4 x 2.5-mm detector collimation. Good to excellent depiction of polyps 8 mm or larger was achieved independently of section thickness or detector collimation. Depiction of polyps 6 mm or smaller depended mainly on the reconstructed section thickness. Depiction of small polyps was superior (protocol 3 and 11) when 4 x 1.0-mm detector collimation was used for the same reconstructed section thickness (3 mm). (b) Size-dependent polyp depiction compared with radiation dose. Protocol numbers in parentheses: 1, 5-10 = 4 x 1-mm detector collimation. Depiction of polyps 8mm or larger was not influenced by tube current reduction when 4 x 1.0-mm detector collimation and 1.25-mm section thickness were used for each protocol. Depiction of smaller polyps deteriorates with reduced tube current but remains possible, even for low-dose (10-mAs) protocols. (c) Size-dependent polyp depiction compared with radiation dose. Protocol numbers in parentheses: 11-15 = 4 x 2.5-mm detector collimation. Depiction of polyps 8 mm or larger was not influenced by tube current reduction when 2.5-mm detector collimation and 3-mm section thickness were used. The effects of tube current reduction were more evident when compared with protocols that used 4 x 1.0-mm detector collimation for depiction of smaller polyps. Polyps smaller than 8 mm were not depicted, even by using the lowest (10-mAs) setting possible. (d) Longitudinal distortion of polyps and rippling artifacts depending on section thickness. Longitudinal distortion and rippling artifacts increased with increasing section thickness and use of broader detector collimation. (e) Sum score of all protocols. Protocols that use 4 x 1.0-mm detector collimation were superior to those that use 4 x 2.5-mm collimation. Low-dose thin-section protocols (protocols 5-10) tended to be superior to high-dose protocols with 4 x 2.5-mm detector collimation (protocol 11) and were only slightly different from high-dose thin-section protocols (protocol 1).

View larger version (17K): [in a new window]   Figure 2d. (a) Size-dependent polyp depiction compared with section thickness and detector collimation. Protocol numbers are in parentheses at the top: 1-4 = 4 x 1.0-mm detector collimation, 11 = 4 x 2.5-mm detector collimation. Good to excellent depiction of polyps 8 mm or larger was achieved independently of section thickness or detector collimation. Depiction of polyps 6 mm or smaller depended mainly on the reconstructed section thickness. Depiction of small polyps was superior (protocol 3 and 11) when 4 x 1.0-mm detector collimation was used for the same reconstructed section thickness (3 mm). (b) Size-dependent polyp depiction compared with radiation dose. Protocol numbers in parentheses: 1, 5-10 = 4 x 1-mm detector collimation. Depiction of polyps 8mm or larger was not influenced by tube current reduction when 4 x 1.0-mm detector collimation and 1.25-mm section thickness were used for each protocol. Depiction of smaller polyps deteriorates with reduced tube current but remains possible, even for low-dose (10-mAs) protocols. (c) Size-dependent polyp depiction compared with radiation dose. Protocol numbers in parentheses: 11-15 = 4 x 2.5-mm detector collimation. Depiction of polyps 8 mm or larger was not influenced by tube current reduction when 2.5-mm detector collimation and 3-mm section thickness were used. The effects of tube current reduction were more evident when compared with protocols that used 4 x 1.0-mm detector collimation for depiction of smaller polyps. Polyps smaller than 8 mm were not depicted, even by using the lowest (10-mAs) setting possible. (d) Longitudinal distortion of polyps and rippling artifacts depending on section thickness. Longitudinal distortion and rippling artifacts increased with increasing section thickness and use of broader detector collimation. (e) Sum score of all protocols. Protocols that use 4 x 1.0-mm detector collimation were superior to those that use 4 x 2.5-mm collimation. Low-dose thin-section protocols (protocols 5-10) tended to be superior to high-dose protocols with 4 x 2.5-mm detector collimation (protocol 11) and were only slightly different from high-dose thin-section protocols (protocol 1).

View larger version (21K): [in a new window]   Figure 2e. (a) Size-dependent polyp depiction compared with section thickness and detector collimation. Protocol numbers are in parentheses at the top: 1-4 = 4 x 1.0-mm detector collimation, 11 = 4 x 2.5-mm detector collimation. Good to excellent depiction of polyps 8 mm or larger was achieved independently of section thickness or detector collimation. Depiction of polyps 6 mm or smaller depended mainly on the reconstructed section thickness. Depiction of small polyps was superior (protocol 3 and 11) when 4 x 1.0-mm detector collimation was used for the same reconstructed section thickness (3 mm). (b) Size-dependent polyp depiction compared with radiation dose. Protocol numbers in parentheses: 1, 5-10 = 4 x 1-mm detector collimation. Depiction of polyps 8mm or larger was not influenced by tube current reduction when 4 x 1.0-mm detector collimation and 1.25-mm section thickness were used for each protocol. Depiction of smaller polyps deteriorates with reduced tube current but remains possible, even for low-dose (10-mAs) protocols. (c) Size-dependent polyp depiction compared with radiation dose. Protocol numbers in parentheses: 11-15 = 4 x 2.5-mm detector collimation. Depiction of polyps 8 mm or larger was not influenced by tube current reduction when 2.5-mm detector collimation and 3-mm section thickness were used. The effects of tube current reduction were more evident when compared with protocols that used 4 x 1.0-mm detector collimation for depiction of smaller polyps. Polyps smaller than 8 mm were not depicted, even by using the lowest (10-mAs) setting possible. (d) Longitudinal distortion of polyps and rippling artifacts depending on section thickness. Longitudinal distortion and rippling artifacts increased with increasing section thickness and use of broader detector collimation. (e) Sum score of all protocols. Protocols that use 4 x 1.0-mm detector collimation were superior to those that use 4 x 2.5-mm collimation. Low-dose thin-section protocols (protocols 5-10) tended to be superior to high-dose protocols with 4 x 2.5-mm detector collimation (protocol 11) and were only slightly different from high-dose thin-section protocols (protocol 1).

View larger version (45K): [in a new window]   Figure 3a. (a) Endoluminal views of spherical phantom polyps with different section thicknesses: A, 1.25 mm; B, 2 mm; C, 3 mm; and D, 5 mm (4 x 1.0-mm detector collimation). Longitudinal distortion and blurring increase with increasing section thickness. (b) Endoluminal views of polyps at different radiation doses: A, 120 kV and 140 mAs; B, 120 kV and 80 mAs; C, 140 kV and 10 mAs, 4 x 1.0-mm detector collimation; D, 140 kV and 10 mAs, 4 x 2.5-mm detector collimation. Despite substantial dose reduction and increasing image noise, delineation of especially small polyps remains possible for protocols that use 4 x 1.0-mm detector collimation.

View larger version (50K): [in a new window]   Figure 3b. (a) Endoluminal views of spherical phantom polyps with different section thicknesses: A, 1.25 mm; B, 2 mm; C, 3 mm; and D, 5 mm (4 x 1.0-mm detector collimation). Longitudinal distortion and blurring increase with increasing section thickness. (b) Endoluminal views of polyps at different radiation doses: A, 120 kV and 140 mAs; B, 120 kV and 80 mAs; C, 140 kV and 10 mAs, 4 x 1.0-mm detector collimation; D, 140 kV and 10 mAs, 4 x 2.5-mm detector collimation. Despite substantial dose reduction and increasing image noise, delineation of especially small polyps remains possible for protocols that use 4 x 1.0-mm detector collimation.