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Fundamental elements for successful performance of CT colonography (virtual colonoscopy).

Park SH, Yee J, Kim SH, Kim YH - Korean J Radiol (2007 Jul-Aug)

Bottom Line: Fecal and fluid tagging may improve the diagnostic accuracy and allow for reduced bowel preparation.Polyps detected at CTC should be measured accurately and reported following the "polyp size-based" patient management system.The time-intensive nature of CTC and the limited resources for training radiologists appear to be the major barriers for implementing CTC in Korea.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and the Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 388-1 Poongnap-2dong, Songpa-gu, 138-736 Seoul, Korea. seongho@amc.seoul.kr

ABSTRACT
There are many factors affecting the successful performance of CT colonography (CTC). Adequate colonic cleansing and distention, the optimal CT technique and interpretation with using the newest CTC software by a trained reader will help ensure high accuracy for lesion detection. Fecal and fluid tagging may improve the diagnostic accuracy and allow for reduced bowel preparation. Automated carbon dioxide insufflation is more efficient and may be safer for colonic distention as compared to manual room air insufflation. CT scanning should use thin collimation of < or =3 mm with a reconstruction interval of < or =1.5 mm and a low radiation dose. There is not any one correct method for the interpretation of CTC; therefore, readers should be well-versed with both the primary 3D and 2D reviews. Polyps detected at CTC should be measured accurately and reported following the "polyp size-based" patient management system. The time-intensive nature of CTC and the limited resources for training radiologists appear to be the major barriers for implementing CTC in Korea.

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Related in: MedlinePlus

A 54-year-old female with a large amount of tagged fecal residue in the sigmoid colon.A. The 3D endoluminal view shows many polypoid and mass-like structures in the sigmoid colon. Examining each polypoid or mass-like structure to distinguish a true polyp/mass from fecal residue is tiresome. Additionally, lesions buried under fecal material are not detected at all during the 3D fly-through.B. Using a wide-window setting (width: 1500 HU, level: -400 HU) for the 2D transverse image, all the pseudolesions (i.e. tagged fecal residue) are easily recognized.
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Figure 5: A 54-year-old female with a large amount of tagged fecal residue in the sigmoid colon.A. The 3D endoluminal view shows many polypoid and mass-like structures in the sigmoid colon. Examining each polypoid or mass-like structure to distinguish a true polyp/mass from fecal residue is tiresome. Additionally, lesions buried under fecal material are not detected at all during the 3D fly-through.B. Using a wide-window setting (width: 1500 HU, level: -400 HU) for the 2D transverse image, all the pseudolesions (i.e. tagged fecal residue) are easily recognized.

Mentions: Primary 2D interpretation refers to review of the colon from the rectum to cecum by scrolling through serial transverse images in a stack mode. Wide display window width and level settings such as 2000 HU/0 HU, 1500 HU/-400 HU or 1500 HU/-200 HU are used to maximize visualization of polyp. Primary 3D review typically refers to an optical colonoscopy-like endoluminal fly-through of a 3D reconstructed colon. This type of review consists of four different fly-throughs: antegrade and retrograde in both the supine and prone positions. The primary 2D review, which requires rapid tracing of the colonic outline on each image to find small contour abnormalities, is generally more reader-intensive (i.e. a higher level of reader concentration and experience is required) than is the primary 3D review. Although it was not proven, a higher sensitivity of the primary 3D review compared to the primary 2D review for polyp detection was also suggested (1). A primary 3D review, on the other hand, has some disadvantages. The primary 3D review is less time-efficient than the 2D review (46-49), and it may not work well with a protocol of reduced preparation and fecal tagging that leaves a large amount of fecal residue in the colon (Fig. 5). Although a 3D fly-through may be capable of detecting all polyp-like structures in a colon, in cases of excess luminal protrusions, differentiation of a true polyp from polyp-like stool by repeated reference to the 2D images or to a translucency map based on lesion density would render the interpretation exhausting. Moreover, those lesions buried under fecal material would not be detectable at all during the 3D fly-through. Unless robust electronic cleansing is available (i.e. digital subtraction of the tagged feces and fluid) (50, 51) with the capability of removing the majority of pseudopolyps (i.e. feces) before the 3D review, primary 3D review of CTC that's performed with reduced preparation, and especially laxative-free CTC, is not likely to be feasible. In contrast, the 2D interpretation of tagged cases is still effective without digital subtraction (Fig. 5B). There is not any one correct method for performing interpretation of CTC. Almost all cases will require a combination of both the 3D and 2D review methods. Therefore, readers should be well-versed with both methods.


Fundamental elements for successful performance of CT colonography (virtual colonoscopy).

Park SH, Yee J, Kim SH, Kim YH - Korean J Radiol (2007 Jul-Aug)

A 54-year-old female with a large amount of tagged fecal residue in the sigmoid colon.A. The 3D endoluminal view shows many polypoid and mass-like structures in the sigmoid colon. Examining each polypoid or mass-like structure to distinguish a true polyp/mass from fecal residue is tiresome. Additionally, lesions buried under fecal material are not detected at all during the 3D fly-through.B. Using a wide-window setting (width: 1500 HU, level: -400 HU) for the 2D transverse image, all the pseudolesions (i.e. tagged fecal residue) are easily recognized.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2627155&req=5

Figure 5: A 54-year-old female with a large amount of tagged fecal residue in the sigmoid colon.A. The 3D endoluminal view shows many polypoid and mass-like structures in the sigmoid colon. Examining each polypoid or mass-like structure to distinguish a true polyp/mass from fecal residue is tiresome. Additionally, lesions buried under fecal material are not detected at all during the 3D fly-through.B. Using a wide-window setting (width: 1500 HU, level: -400 HU) for the 2D transverse image, all the pseudolesions (i.e. tagged fecal residue) are easily recognized.
Mentions: Primary 2D interpretation refers to review of the colon from the rectum to cecum by scrolling through serial transverse images in a stack mode. Wide display window width and level settings such as 2000 HU/0 HU, 1500 HU/-400 HU or 1500 HU/-200 HU are used to maximize visualization of polyp. Primary 3D review typically refers to an optical colonoscopy-like endoluminal fly-through of a 3D reconstructed colon. This type of review consists of four different fly-throughs: antegrade and retrograde in both the supine and prone positions. The primary 2D review, which requires rapid tracing of the colonic outline on each image to find small contour abnormalities, is generally more reader-intensive (i.e. a higher level of reader concentration and experience is required) than is the primary 3D review. Although it was not proven, a higher sensitivity of the primary 3D review compared to the primary 2D review for polyp detection was also suggested (1). A primary 3D review, on the other hand, has some disadvantages. The primary 3D review is less time-efficient than the 2D review (46-49), and it may not work well with a protocol of reduced preparation and fecal tagging that leaves a large amount of fecal residue in the colon (Fig. 5). Although a 3D fly-through may be capable of detecting all polyp-like structures in a colon, in cases of excess luminal protrusions, differentiation of a true polyp from polyp-like stool by repeated reference to the 2D images or to a translucency map based on lesion density would render the interpretation exhausting. Moreover, those lesions buried under fecal material would not be detectable at all during the 3D fly-through. Unless robust electronic cleansing is available (i.e. digital subtraction of the tagged feces and fluid) (50, 51) with the capability of removing the majority of pseudopolyps (i.e. feces) before the 3D review, primary 3D review of CTC that's performed with reduced preparation, and especially laxative-free CTC, is not likely to be feasible. In contrast, the 2D interpretation of tagged cases is still effective without digital subtraction (Fig. 5B). There is not any one correct method for performing interpretation of CTC. Almost all cases will require a combination of both the 3D and 2D review methods. Therefore, readers should be well-versed with both methods.

Bottom Line: Fecal and fluid tagging may improve the diagnostic accuracy and allow for reduced bowel preparation.Polyps detected at CTC should be measured accurately and reported following the "polyp size-based" patient management system.The time-intensive nature of CTC and the limited resources for training radiologists appear to be the major barriers for implementing CTC in Korea.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and the Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 388-1 Poongnap-2dong, Songpa-gu, 138-736 Seoul, Korea. seongho@amc.seoul.kr

ABSTRACT
There are many factors affecting the successful performance of CT colonography (CTC). Adequate colonic cleansing and distention, the optimal CT technique and interpretation with using the newest CTC software by a trained reader will help ensure high accuracy for lesion detection. Fecal and fluid tagging may improve the diagnostic accuracy and allow for reduced bowel preparation. Automated carbon dioxide insufflation is more efficient and may be safer for colonic distention as compared to manual room air insufflation. CT scanning should use thin collimation of < or =3 mm with a reconstruction interval of < or =1.5 mm and a low radiation dose. There is not any one correct method for the interpretation of CTC; therefore, readers should be well-versed with both the primary 3D and 2D reviews. Polyps detected at CTC should be measured accurately and reported following the "polyp size-based" patient management system. The time-intensive nature of CTC and the limited resources for training radiologists appear to be the major barriers for implementing CTC in Korea.

Show MeSH
Related in: MedlinePlus