DOI: 10.1148/rg.26si065508
New Techniques in CT Angiography1
Michael M. Lell, MD,
Katharina Anders, MD,
Michael Uder, MD,
Ernst Klotz,
Hendrik Ditt,
Fernando Vega-Higuera, PhD,
Tobias Boskamp, PhD,
Werner A. Bautz, MD and
Bernd F. Tomandl, MD
1 From the Department of Radiological Sciences, David Geffen School of Medicine, University of California, Los Angeles (M.M.L.); the Department of Radiology (M.M.L., K.A., M.U., W.A.B.) and Computer Graphics Group (F.V.H.), University of Erlangen-Nuremberg, Maximiliansplatz 1, 91054 Erlangen, Germany; Siemens Medical Solutions, Forchheim, Germany (E.K., H.D.); the MeVis Center for Medical Diagnostic Systems and Visualization, Bremen, Germany (T.B.); and the Department of Neuroradiology, Klinikum-Bremen-Mitte, Bremen, Germany (B.F.T.). Presented as an education exhibit at the 2005 RSNA Annual Meeting. Received February 7, 2006; revision requested April 13 and received May 8; accepted May 17. E.K., H.D., and F.V.H. are employees of Siemens Medical Solutions; T.B. receives research support from Siemens Medical Solutions; all other authors have no financial relationships to disclose.
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Figure 1a. Test bolus method. (a) Axial image shows the right internal carotid artery (ICA) (1), left ICA (2), and left internal jugular vein (3). (b) Diagram shows the enhancement curves for the right ICA (1), left ICA (2), and left internal jugular vein (3) after injection of 10 mL of contrast material and a saline solution bolus. The individual start delay can be set between the arterial peak and the venous upslope. ROI = region of interest.
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Figure 1b. Test bolus method. (a) Axial image shows the right internal carotid artery (ICA) (1), left ICA (2), and left internal jugular vein (3). (b) Diagram shows the enhancement curves for the right ICA (1), left ICA (2), and left internal jugular vein (3) after injection of 10 mL of contrast material and a saline solution bolus. The individual start delay can be set between the arterial peak and the venous upslope. ROI = region of interest.
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Figure 2a. Moderate stenosis of the left ICA. (a) Axial source image. (b) Sagittal MPR image. (c) MPR image aligned perpendicular to the vessel optimally depicts the residual lumen (solid arrow) and plaque calcification (dotted arrow).
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Figure 2b. Moderate stenosis of the left ICA. (a) Axial source image. (b) Sagittal MPR image. (c) MPR image aligned perpendicular to the vessel optimally depicts the residual lumen (solid arrow) and plaque calcification (dotted arrow).
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Figure 2c. Moderate stenosis of the left ICA. (a) Axial source image. (b) Sagittal MPR image. (c) MPR image aligned perpendicular to the vessel optimally depicts the residual lumen (solid arrow) and plaque calcification (dotted arrow).
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Figure 3. Thin-slab MIP image (slab thickness = 15 mm) shows the cervical part of the carotid artery. Superimposition of vessels or calcified structures alter lumen visualization (arrow).
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Figure 4. Shaded surface display image shows bone and contrast-enhanced vessels as well as calcified plaque. All voxels above the threshold are represented equally. Parts of the jaw were manually removed from the image to exempt the left ICA. The right carotid artery is partly visualized; an occlusion of the right ICA is evident.
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Figure 5a. Different transfer function settings alter the representation of the lumen. (a, b) Volume-rendered images created without shading at low opacity (a) and high opacity (b) show accentuated vessel boundaries. (c) On a volume-rendered image created with shading, the 3D impression is improved but edge definition is reduced. (The transfer functions in b and c are identical.) (d) Volume-rendered image created with the transfer function shifted toward higher Hounsfield unit values results in reduced caliber of the visualized vessels.
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Figure 5b. Different transfer function settings alter the representation of the lumen. (a, b) Volume-rendered images created without shading at low opacity (a) and high opacity (b) show accentuated vessel boundaries. (c) On a volume-rendered image created with shading, the 3D impression is improved but edge definition is reduced. (The transfer functions in b and c are identical.) (d) Volume-rendered image created with the transfer function shifted toward higher Hounsfield unit values results in reduced caliber of the visualized vessels.
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Figure 5c. Different transfer function settings alter the representation of the lumen. (a, b) Volume-rendered images created without shading at low opacity (a) and high opacity (b) show accentuated vessel boundaries. (c) On a volume-rendered image created with shading, the 3D impression is improved but edge definition is reduced. (The transfer functions in b and c are identical.) (d) Volume-rendered image created with the transfer function shifted toward higher Hounsfield unit values results in reduced caliber of the visualized vessels.
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Figure 5d. Different transfer function settings alter the representation of the lumen. (a, b) Volume-rendered images created without shading at low opacity (a) and high opacity (b) show accentuated vessel boundaries. (c) On a volume-rendered image created with shading, the 3D impression is improved but edge definition is reduced. (The transfer functions in b and c are identical.) (d) Volume-rendered image created with the transfer function shifted toward higher Hounsfield unit values results in reduced caliber of the visualized vessels.
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Figure 6. Image created with segmentation shows punched-out defects (arrows) at vessel-bone contact areas. The brachiocephalic vein was removed from the image with additional segmentation; artificial "erosion" of the aortic arch and truncus communis (black patches) resulted from this procedure.
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Figure 7. Analysis on the basis of a centerline determined with segmentation and skeletonization. Top left: On a 3D display image, the segmented part of the left carotid artery is colored red. This subvolume was used to create a stretched vessel image (middle) and a cross-sectional diagram of vessel diameter (right). On the stretched vessel image, the horizontal structure (arrow) is the external carotid artery; the center of the purple crosshairs is located in the stenosis and indicates the position of the cross-sectional image (bottom left).
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Figure 8a. Effect of various threshold values on threshold-based definition of the lumen boundary. Threshold values of 150 HU (a), 200 HU (b), and 250 HU (c) result in calculated stenosis values of 35%, 55%, and 65%, respectively.
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Figure 8b. Effect of various threshold values on threshold-based definition of the lumen boundary. Threshold values of 150 HU (a), 200 HU (b), and 250 HU (c) result in calculated stenosis values of 35%, 55%, and 65%, respectively.
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Figure 8c. Effect of various threshold values on threshold-based definition of the lumen boundary. Threshold values of 150 HU (a), 200 HU (b), and 250 HU (c) result in calculated stenosis values of 35%, 55%, and 65%, respectively.
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Figure 9. Profile of the ideal tissue boundary and the corresponding result at CT angiographic reformation. Reformation of CT angiographic data smoothes boundaries to an erf function. The corresponding gradient magnitude reaches its peak at the center of the boundary and decreases at both sides until becoming zero in areas corresponding to uniform tissues.
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Figure 10a. (a) Two-dimensional histogram based on intensities (x axis) and gradient magnitudes (y axis) obtained from CT angiographic data. This structure clearly demonstrates tissue boundaries as parabolic arcs. Voxels lying close to tissue boundaries or inside uniform tissue produce histogram "hits" along the upper or lower regions of the parabolas. Open arrow = air, open arrowhead = soft tissue, solid arrowhead = vessels, solid arrow = osseous tissue. (b) Voxels corresponding to osseous tissue (arrow) and vessels enhanced with contrast medium (arrowhead) are easily identifiable in the 2D transfer function editor. Predefined tissue boundary templates can be interactively placed and adjusted over the corresponding 2D histogram with immediate feedback on volume-rendered images.
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Figure 10b. (a) Two-dimensional histogram based on intensities (x axis) and gradient magnitudes (y axis) obtained from CT angiographic data. This structure clearly demonstrates tissue boundaries as parabolic arcs. Voxels lying close to tissue boundaries or inside uniform tissue produce histogram "hits" along the upper or lower regions of the parabolas. Open arrow = air, open arrowhead = soft tissue, solid arrowhead = vessels, solid arrow = osseous tissue. (b) Voxels corresponding to osseous tissue (arrow) and vessels enhanced with contrast medium (arrowhead) are easily identifiable in the 2D transfer function editor. Predefined tissue boundary templates can be interactively placed and adjusted over the corresponding 2D histogram with immediate feedback on volume-rendered images.
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Figure 11. Volume-rendered image obtained after fitting the parabolic arc object to the area representing contrast-enhanced vessels in the 2D histogram. Without further interaction, bone and plaque calcifications are removed from the image.
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Figure 12. MIP image created after bone subtraction CT angiography shows complete elimination of bone; only small calcifications of the hyoid and laryngeal cartilage remain because of swallowing between the non-enhanced and contrast-enhanced acquisitions. The vertebral arteries are clearly demonstrated without artificial lumen reduction at the vertebral foramen. A large lymph node metastasis displaces the left carotid artery; there is mild stenosis of the right ICA.
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Figure 13. Volume-rendered (top right) and MIP (bottom right) images show incomplete bone removal due to severe movement between the two acquisitions. Volume-rendered (top left) and MIP (bottom left) images created after repetitive registration of subvolumes (28) show optimized bone removal.
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Figure 14a. CT angiographic images obtained before (a) and after (b) bone subtraction show successful bone removal. However, plaque calcifications (arrow in b) remain in the bone subtraction image because of misregistration due to arterial pulsation.
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Figure 14b. CT angiographic images obtained before (a) and after (b) bone subtraction show successful bone removal. However, plaque calcifications (arrow in b) remain in the bone subtraction image because of misregistration due to arterial pulsation.
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Figure 15. High-grade stenosis with circular calcification of the right ICA. Top left: Three-dimensional rendered image highlights the segmented part of the right carotid artery. Cross-sectional MPR image (bottom left) obtained at the current path location, which is indicated by the purple crosshairs on the stretched MPR image (middle), shows the residual lumen surrounded by dense calcification. Right: Cross-sectional diagram shows the results of automatic measurement of area or diameter along the analysis path. The ICA calcification complicates analysis of the residual lumen with automatic and manual procedures.
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Figure 16a. Bilateral stenoses of the distal ICA. (a) MIP image from bone subtraction CT angiography shows the full extents of the stenoses. (b) On a volume-rendered image from CT angiography, parts of the ICAs are hidden. (c) Image from selective catheter angiography shows the same findings as CT angiography. (The image was created from two digital subtraction angiographic series.)
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Figure 16b. Bilateral stenoses of the distal ICA. (a) MIP image from bone subtraction CT angiography shows the full extents of the stenoses. (b) On a volume-rendered image from CT angiography, parts of the ICAs are hidden. (c) Image from selective catheter angiography shows the same findings as CT angiography. (The image was created from two digital subtraction angiographic series.)
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Figure 16c. Bilateral stenoses of the distal ICA. (a) MIP image from bone subtraction CT angiography shows the full extents of the stenoses. (b) On a volume-rendered image from CT angiography, parts of the ICAs are hidden. (c) Image from selective catheter angiography shows the same findings as CT angiography. (The image was created from two digital subtraction angiographic series.)
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Figure 17. Tumor invasion of the right transverse sinus. MIP image from bone subtraction CT venography shows the large cerebral veins and sinuses. Because only the voxels representing bone are removed from the image, the soft tissues remain for further evaluation.
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Figure 18a. Large vascular malformation with significant arteriovenous shunting. (a, b) Coronal MPR (a) and thin-slab MIP (b) images show the internal structure of the lesion and thinning of the skull in detail. (c, d) Volume-rendered images created with the one-dimensional transfer function technique (c) and from segmented data with a high-opacity setting (d) provide the best 3D representation but do not show the thrombosed parts of the lesion. (e, f) Volume-rendered image from bone subtraction CT angiography (e) and image from digital subtraction angiography (f) show that the lesion has no feeding vessels from the ICA (inset).
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Figure 18b. Large vascular malformation with significant arteriovenous shunting. (a, b) Coronal MPR (a) and thin-slab MIP (b) images show the internal structure of the lesion and thinning of the skull in detail. (c, d) Volume-rendered images created with the one-dimensional transfer function technique (c) and from segmented data with a high-opacity setting (d) provide the best 3D representation but do not show the thrombosed parts of the lesion. (e, f) Volume-rendered image from bone subtraction CT angiography (e) and image from digital subtraction angiography (f) show that the lesion has no feeding vessels from the ICA (inset).
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Figure 18c. Large vascular malformation with significant arteriovenous shunting. (a, b) Coronal MPR (a) and thin-slab MIP (b) images show the internal structure of the lesion and thinning of the skull in detail. (c, d) Volume-rendered images created with the one-dimensional transfer function technique (c) and from segmented data with a high-opacity setting (d) provide the best 3D representation but do not show the thrombosed parts of the lesion. (e, f) Volume-rendered image from bone subtraction CT angiography (e) and image from digital subtraction angiography (f) show that the lesion has no feeding vessels from the ICA (inset).
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Figure 18d. Large vascular malformation with significant arteriovenous shunting. (a, b) Coronal MPR (a) and thin-slab MIP (b) images show the internal structure of the lesion and thinning of the skull in detail. (c, d) Volume-rendered images created with the one-dimensional transfer function technique (c) and from segmented data with a high-opacity setting (d) provide the best 3D representation but do not show the thrombosed parts of the lesion. (e, f) Volume-rendered image from bone subtraction CT angiography (e) and image from digital subtraction angiography (f) show that the lesion has no feeding vessels from the ICA (inset).
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Figure 18e. Large vascular malformation with significant arteriovenous shunting. (a, b) Coronal MPR (a) and thin-slab MIP (b) images show the internal structure of the lesion and thinning of the skull in detail. (c, d) Volume-rendered images created with the one-dimensional transfer function technique (c) and from segmented data with a high-opacity setting (d) provide the best 3D representation but do not show the thrombosed parts of the lesion. (e, f) Volume-rendered image from bone subtraction CT angiography (e) and image from digital subtraction angiography (f) show that the lesion has no feeding vessels from the ICA (inset).
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Figure 18f. Large vascular malformation with significant arteriovenous shunting. (a, b) Coronal MPR (a) and thin-slab MIP (b) images show the internal structure of the lesion and thinning of the skull in detail. (c, d) Volume-rendered images created with the one-dimensional transfer function technique (c) and from segmented data with a high-opacity setting (d) provide the best 3D representation but do not show the thrombosed parts of the lesion. (e, f) Volume-rendered image from bone subtraction CT angiography (e) and image from digital subtraction angiography (f) show that the lesion has no feeding vessels from the ICA (inset).
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Figure 19a. Aneurysms of the right ICA and left posterior cerebral artery. (a) On an image created with one-dimensional transfer functions, vessels and bone cannot be well differentiated because of an overlap in the attenuations of these structures. (b) Volume-rendered image from bone subtraction CT angiography shows the vessels clearly. Use of a high-opacity setting improves the 3D representation; however, the enhanced cavernous sinus hides small portions of the ICA. (c) On an image created with a low-opacity setting, the sinus is transparent, thus allowing visualization of the vessel boundary. (d) Volume-rendered image created with 2D transfer functions shows similar results.
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Figure 19b. Aneurysms of the right ICA and left posterior cerebral artery. (a) On an image created with one-dimensional transfer functions, vessels and bone cannot be well differentiated because of an overlap in the attenuations of these structures. (b) Volume-rendered image from bone subtraction CT angiography shows the vessels clearly. Use of a high-opacity setting improves the 3D representation; however, the enhanced cavernous sinus hides small portions of the ICA. (c) On an image created with a low-opacity setting, the sinus is transparent, thus allowing visualization of the vessel boundary. (d) Volume-rendered image created with 2D transfer functions shows similar results.
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Figure 19c. Aneurysms of the right ICA and left posterior cerebral artery. (a) On an image created with one-dimensional transfer functions, vessels and bone cannot be well differentiated because of an overlap in the attenuations of these structures. (b) Volume-rendered image from bone subtraction CT angiography shows the vessels clearly. Use of a high-opacity setting improves the 3D representation; however, the enhanced cavernous sinus hides small portions of the ICA. (c) On an image created with a low-opacity setting, the sinus is transparent, thus allowing visualization of the vessel boundary. (d) Volume-rendered image created with 2D transfer functions shows similar results.
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Figure 19d. Aneurysms of the right ICA and left posterior cerebral artery. (a) On an image created with one-dimensional transfer functions, vessels and bone cannot be well differentiated because of an overlap in the attenuations of these structures. (b) Volume-rendered image from bone subtraction CT angiography shows the vessels clearly. Use of a high-opacity setting improves the 3D representation; however, the enhanced cavernous sinus hides small portions of the ICA. (c) On an image created with a low-opacity setting, the sinus is transparent, thus allowing visualization of the vessel boundary. (d) Volume-rendered image created with 2D transfer functions shows similar results.
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Figure 20a. Follow-up after clipping of an aneurysm. (a) Volume-rendered image from bone subtraction CT angiography (view from above) shows a simulated occlusion of the right distal ICA (C7) and proximal anterior (A1) and medial (M1) cerebral arteries. (b) Image created from the original CT angiographic data shows the location of the aneurysm clip, which was completely removed from the image. (c) Thin-slab MIP image shows the clip and beam-hardening artifacts.
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Figure 20b. Follow-up after clipping of an aneurysm. (a) Volume-rendered image from bone subtraction CT angiography (view from above) shows a simulated occlusion of the right distal ICA (C7) and proximal anterior (A1) and medial (M1) cerebral arteries. (b) Image created from the original CT angiographic data shows the location of the aneurysm clip, which was completely removed from the image. (c) Thin-slab MIP image shows the clip and beam-hardening artifacts.
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Figure 20c. Follow-up after clipping of an aneurysm. (a) Volume-rendered image from bone subtraction CT angiography (view from above) shows a simulated occlusion of the right distal ICA (C7) and proximal anterior (A1) and medial (M1) cerebral arteries. (b) Image created from the original CT angiographic data shows the location of the aneurysm clip, which was completely removed from the image. (c) Thin-slab MIP image shows the clip and beam-hardening artifacts.
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Copyright © 2006 by the Radiological Society of North America.
