Endoluminal View

Fig. 7.1a-d. Multi-row CT colonography datasets showing a pedunculated (a, axial b, endoluminal view) and sessile (c, axial d, endoluminal view) polyp, located in the sigmoid colon... 

Fig. 7.2a-c. Multi-row CT angiography of the entire aorta, a MPR with cross sectional measurement of the vessel diameters, b 3D volume rendering and c endoluminal view obtained at the level of the renal arteries. In this latter view the orifi ces of the superior mesenteric artery (SMA), right (RRA) and left (LJiA) renal arteries and the lumen of the abdominal aorta (AA) can be appreciated... 

Fig. 7.3a,b. Endoluminal views ofthe bronchial bifurcation. In athe right and left main bronchi are visible from the trachea. A more caudal view (b) shows even the orifice of the bronchus for the righ upper lobe (red arrow)... 

In the study of the middle and inner ear we have proposed the following single-slice spiral CT protocol axial and coronal acquisitions beam collimation, 1 mm pitch 1 and 0.5 mm reconstructions spacing (see Chap. 10 on temporal bone for details) (Neri et al. 2000b). In this study all components of the middle ear could be visualized, but also endoluminal views of the bone labyrinth were created (Fig. 7.6). 

Endoluminal Views of the Middle Ear Virtual Endoscopy (Technique) 140... 

The knowledge of these segmentation values is extremely important to determine whether or not the reconstructed images correspond to reality. To this end a comparison between real anatomy and 3D reconstructed endoluminal views from seven formalin fixed anatomical specimens was performed by our group (Neri et al. 2000b). We found a 100% agreement between the observations for endoluminal views and anatomical sections, even if in two cases the complete visualization of the middle ear cavity could not initially be obtained for the presence of tissue remnants within the external auditory meatus. However, careful electronic removal of this tissue allowed visualizing the middle ear, while in the case of anatomical specimens, the tissue remnants were manually removed. 

Fig. 14.18. Endoluminal view and cross-sectional correlation of a mucoid obstruction...

Fig. 19.3. The respective images are made with a viewing angle of 60°, 90°, 120° and 160°. The increase of colonic surface is illustrated by a polyp behind a fold (arrow) that can only be detected from this direction with endoluminal views of 120° and 160°, and would otherwise be missed...

Fig. 19.4. Endoluminal view showing uninvestigated areas (indicated pink) that were not previously viewed during conventional fly-through...

Endoluminal views of the pancreatic and bile ducts can be obtained by rendering CT or MR data sets. 

Fortunately, the majority of the CAD false-positives - approximately 80-90% of them - can be dismissed relatively easily based on their characteristic locations and appearance, and thus they are not a productivity hindrance (Okamura et al. 2004 Taylor et al. 2003). For example, a falsepositive detection on a thickened fold can be easily dismissed in a 3D endoluminal view, in which the reader can see the global structure of a fold on which a small bump that CAD points to is located. False-positives due to ileocecal valves and the rectal tube can easily be dismissed based on their anatomic location and shape a semi-automated recognition of ileocecal valves (Summers et al. 2004) and rectal tubes (lORDANESCU and Summers 2004 Suzuki et al. 2006) may make this already easy task even easier (Summers et al. 2004). Solid stool can be difficult false-positives to dismiss however, one may distinguish them from polyps by visual correspondence analysis between prone and supine views this relatively elaborate task can also be facilitated by a computerized correspondence between supine and prone data sets (Nappi et al. 2004c). 

Fig. 27.9.a-d Detection of masses a 50-mm intraluminal circumferential mass with apple-core morphology, and (b) its CTC endoluminal view. cThe entire mass region was extracted in a mass detection method in CAD, as indicated by the white region in the MPR view, and (d) its CTC endoluminal view... 

Fig. 3.1. a Coronal multiplanar reformat demonstrates a well-cleansed transverse colon with no layering fluid or residual solid stool, b Three-dimensional endoluminal view from the same patient showing normal haustral folds which are easily evaluated because of the absence of residual material... 

Fig. 3.2. a Excellent distension of the ascending colon and cecum on a sagittal multiplanar reformat optimizes diagnostic ability, b A well-distended segment in the same patient on the endoluminal view allows easy navigation... 

Fig. 3.3. a Suboptimal bowel preparation due to a large amount of residual fluid layering along the dependent wall of the colon as seen on this sagittal multiplanar reformatted view, b Poor cleansing with a large amount of layering fluid that obscures the colonic wall beneath it on this endoluminal view in the same patient... 

Proper cleansing of the colon is essential if the radiologist is to identify colonic lesions accurately on CT colonography. Remaining pools of fluid in the colon can hide polyps and cancer both on two-dimensional axial and reformatted images and on the three-dimensional endoluminal views (Figs. 3.3,... 

Fig. 3.7. a Collapse of a long length of the sigmoid on coronal multiplanar reformatted view simulating annular carcinoma, b Occlusion of the lumen on endoluminal view due to collapse of the sigmoid in the same patient. This appearance may also be caused by an occluding carcinoma, and proper colonic distension is essential for differentiation... 

Fig. 4.4.a Stalked polyp in the sigmoid (white arrow) with some tagged fluid (black arrowheads), b Corresponding endoluminal view showing the head of the polyp (white arrow)... 

Fig. 4.15.a Ultra low dose scan (64-slice). Supine view of the rectum showing an 8-mm sessile polyp on the anterior border above a small level of tagged fluid, besides the first valve of Houston (black arrows). The valve of Houston is visible in the fluid as a linear Ailing defect. Small non-tagged residue in the fluid (open black arrowhead), c Corresponding endoluminal view. Despite the ultra low dose there are no streak artefacts. The polyp is easy to detect (black arrow) besides the first valve of Houston (black arrowheads)... 

Fig. 4.18.a Polyp with a small stalk in the descending colon (white arrows), b Corresponding endoluminal view showing the stalk (white arrows) and the head (white arrowhead) of the polyp... 

Fig. 6.6a,b. The increase in image noise is perceived more on three-dimensional endoluminal views a, standard dose scan b, low dose scan. Note sharpness of endoluminal surface negatively affected by dose reduction in b... 

Fig. 6.7a-c. Low dose scan of carcinomatous polyp of the right colon. Although a noise clearly degrades image quality, the evaluation using b wide window centre and setting as well as c three-dimensional endoluminal view are not significantly affected... 

Fig. 9.3. Endoluminal view with Missed Region Tool. This feature allows the reader to investigate areas (indicated in pink) that were not previously viewed during conventional fly through. (Figure courtesy of Viatronix, Stony Brook, NY)...

Fig. 9.4. Distortion illustrated of a polyp at four different endoluminal views of 160°, 120°, 90° and 60°...

Fig. 9.11. Screen panel that combines a conventional endoluminal view (bottom left), an unfolded cube display (center), an axial 2D display (top left), a 2D MPR display (top center) and an overview of the colon (top right)...

Unlike polypoid lesions, which are more easily detected on 3D endoluminal views, invasive mass lesions are better depicted on 2D images, which allowmural and extramural evaluation (Pickhardt 2004). 

Polyps maybe sessile, pedunculated, or flat (i.e., with the base measuring more than twice that of the height). Sessile polyps will possess polypoid morphology on axial, 2D multiplanar reformatted, and 3D endoluminal views (Fig. 14.23). When sessile polyps are of sufficient size (generally consid-... 

Fig. 14.2 la-d. Compression by one of the iliac arteries in this case has resulted in a linear extrinsic compression on the sigmoid colon that is well demonstrated on 3 D endoluminal view (a, arrows) and virtual pathology (b, arrow). 2D axial images demonstrates the extrinsic nature of these lesions (c,d, arrows)... 

Fig. 14.23a-c. Sessile polyp a supine 2D axial image and b 3-D endoluminal view demonstrate a polypoid filling defect in the ascending colon c after changing to soft tissue window setting, the homogenous soft tissue attenuation of the lesion is demonstrated. Colonoscopy demonstrated a 1.5 tubulovillous adenoma... 

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