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Virtual CT Intravascular Endoscopy of the Aorta: Pierced Surface and Floating Shape Thresholding Artifacts¹

¹ From the Department of Oncology, Diagnostic and Interventional Radiology, University of Pisa, Via Roma 67, I-56100 Pisa, Italy. Received December 15, 1997; revision requested March 2, 1998; final revision received November 6; accepted January 19, 1999. Address reprint requests to E.N. (e-mail: neri@do.med.unipi.it).

View larger version (174K): [in a new window]   Figure 1a. Virtual CT intravascular endoscopic images of the abdominal aorta show the internal surface at the level of the ostium (arrow in a) of the right renal artery. (a) Field of view, 60°; low threshold, 200 HU; high threshold, 500 HU. No artifacts are visible. (b) Low threshold, 120 HU; high threshold, 500 HU. The low-threshold pierced surface artifacts appear as holes through the aortic and renal artery walls (right arrows and left arrow, respectively). (c) Low threshold, 240 HU; high threshold, 500 HU. The low-threshold floating shape artifacts (arrows) appear inside the aortic lumen. The threshold level excludes the ostium of the right renal artery from the rendered data set. (d) Low threshold, 200 HU; high threshold, 350 HU. Low-threshold pierced surface and floating shape artifacts are not present. The ostium of the right renal artery is visible, but high-threshold floating shape artifacts (arrows) are visible inside the lumen.

View larger version (179K): [in a new window]   Figure 1b. Virtual CT intravascular endoscopic images of the abdominal aorta show the internal surface at the level of the ostium (arrow in a) of the right renal artery. (a) Field of view, 60°; low threshold, 200 HU; high threshold, 500 HU. No artifacts are visible. (b) Low threshold, 120 HU; high threshold, 500 HU. The low-threshold pierced surface artifacts appear as holes through the aortic and renal artery walls (right arrows and left arrow, respectively). (c) Low threshold, 240 HU; high threshold, 500 HU. The low-threshold floating shape artifacts (arrows) appear inside the aortic lumen. The threshold level excludes the ostium of the right renal artery from the rendered data set. (d) Low threshold, 200 HU; high threshold, 350 HU. Low-threshold pierced surface and floating shape artifacts are not present. The ostium of the right renal artery is visible, but high-threshold floating shape artifacts (arrows) are visible inside the lumen.

View larger version (165K): [in a new window]   Figure 1c. Virtual CT intravascular endoscopic images of the abdominal aorta show the internal surface at the level of the ostium (arrow in a) of the right renal artery. (a) Field of view, 60°; low threshold, 200 HU; high threshold, 500 HU. No artifacts are visible. (b) Low threshold, 120 HU; high threshold, 500 HU. The low-threshold pierced surface artifacts appear as holes through the aortic and renal artery walls (right arrows and left arrow, respectively). (c) Low threshold, 240 HU; high threshold, 500 HU. The low-threshold floating shape artifacts (arrows) appear inside the aortic lumen. The threshold level excludes the ostium of the right renal artery from the rendered data set. (d) Low threshold, 200 HU; high threshold, 350 HU. Low-threshold pierced surface and floating shape artifacts are not present. The ostium of the right renal artery is visible, but high-threshold floating shape artifacts (arrows) are visible inside the lumen.

View larger version (180K): [in a new window]   Figure 1d. Virtual CT intravascular endoscopic images of the abdominal aorta show the internal surface at the level of the ostium (arrow in a) of the right renal artery. (a) Field of view, 60°; low threshold, 200 HU; high threshold, 500 HU. No artifacts are visible. (b) Low threshold, 120 HU; high threshold, 500 HU. The low-threshold pierced surface artifacts appear as holes through the aortic and renal artery walls (right arrows and left arrow, respectively). (c) Low threshold, 240 HU; high threshold, 500 HU. The low-threshold floating shape artifacts (arrows) appear inside the aortic lumen. The threshold level excludes the ostium of the right renal artery from the rendered data set. (d) Low threshold, 200 HU; high threshold, 350 HU. Low-threshold pierced surface and floating shape artifacts are not present. The ostium of the right renal artery is visible, but high-threshold floating shape artifacts (arrows) are visible inside the lumen.

View larger version (16K): [in a new window]   Figure 2a. Artifacts observed at virtual CT intravascular endoscopy in the abdominal aorta. (a) Box plots compare threshold levels for low-threshold pierced surface (LT-PS) artifacts (range, 40–150 HU; mean, 95.862 ± 32.129), low-threshold floating shape (LT-FS) artifacts (range, 70–300 HU; mean, 191.034 ± 59.121), and high-threshold floating shape (HT-FS) artifacts (range, 145–460 HU; mean, 312.241 ± 69.018). Upper and lower margins of box plots represent the 75th and 25th percentiles, respectively. The median is the line bisecting the box. Error bars represent SD. = outliers. (b) Linear regression analysis shows a not statistically significant correlation between mean attenuation value and low-threshold pierced surface artifact (r = 0.325, P = .086). (c) Scattergram shows a positive and good (r > 0.7) correlation between mean attenuation and low-threshold floating shape artifacts (r = 0.77, P = .001). (d) Scattergram shows the same correlation between mean attenuation and high-threshold floating shape artifacts (r = 0.86, P = .001).

View larger version (17K): [in a new window]   Figure 2b. Artifacts observed at virtual CT intravascular endoscopy in the abdominal aorta. (a) Box plots compare threshold levels for low-threshold pierced surface (LT-PS) artifacts (range, 40–150 HU; mean, 95.862 ± 32.129), low-threshold floating shape (LT-FS) artifacts (range, 70–300 HU; mean, 191.034 ± 59.121), and high-threshold floating shape (HT-FS) artifacts (range, 145–460 HU; mean, 312.241 ± 69.018). Upper and lower margins of box plots represent the 75th and 25th percentiles, respectively. The median is the line bisecting the box. Error bars represent SD. = outliers. (b) Linear regression analysis shows a not statistically significant correlation between mean attenuation value and low-threshold pierced surface artifact (r = 0.325, P = .086). (c) Scattergram shows a positive and good (r > 0.7) correlation between mean attenuation and low-threshold floating shape artifacts (r = 0.77, P = .001). (d) Scattergram shows the same correlation between mean attenuation and high-threshold floating shape artifacts (r = 0.86, P = .001).

View larger version (16K): [in a new window]   Figure 2c. Artifacts observed at virtual CT intravascular endoscopy in the abdominal aorta. (a) Box plots compare threshold levels for low-threshold pierced surface (LT-PS) artifacts (range, 40–150 HU; mean, 95.862 ± 32.129), low-threshold floating shape (LT-FS) artifacts (range, 70–300 HU; mean, 191.034 ± 59.121), and high-threshold floating shape (HT-FS) artifacts (range, 145–460 HU; mean, 312.241 ± 69.018). Upper and lower margins of box plots represent the 75th and 25th percentiles, respectively. The median is the line bisecting the box. Error bars represent SD. = outliers. (b) Linear regression analysis shows a not statistically significant correlation between mean attenuation value and low-threshold pierced surface artifact (r = 0.325, P = .086). (c) Scattergram shows a positive and good (r > 0.7) correlation between mean attenuation and low-threshold floating shape artifacts (r = 0.77, P = .001). (d) Scattergram shows the same correlation between mean attenuation and high-threshold floating shape artifacts (r = 0.86, P = .001).

View larger version (18K): [in a new window]   Figure 2d. Artifacts observed at virtual CT intravascular endoscopy in the abdominal aorta. (a) Box plots compare threshold levels for low-threshold pierced surface (LT-PS) artifacts (range, 40–150 HU; mean, 95.862 ± 32.129), low-threshold floating shape (LT-FS) artifacts (range, 70–300 HU; mean, 191.034 ± 59.121), and high-threshold floating shape (HT-FS) artifacts (range, 145–460 HU; mean, 312.241 ± 69.018). Upper and lower margins of box plots represent the 75th and 25th percentiles, respectively. The median is the line bisecting the box. Error bars represent SD. = outliers. (b) Linear regression analysis shows a not statistically significant correlation between mean attenuation value and low-threshold pierced surface artifact (r = 0.325, P = .086). (c) Scattergram shows a positive and good (r > 0.7) correlation between mean attenuation and low-threshold floating shape artifacts (r = 0.77, P = .001). (d) Scattergram shows the same correlation between mean attenuation and high-threshold floating shape artifacts (r = 0.86, P = .001).