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Comparison of image reconstruction methods for electron-beam CT coronary angiography
Comparison of I m a g e Reconstruction M e t h o d s for E l e c t r o n - B e a m CT Corona~KAngiography Gautham P. Reddy, MD, MPH, Matthew J. Budoff, MD, Conrad P. Zalace, Bruce H. Brundage, MD, Charles B. Higgins, MD
University of California, San Francisco and Harbor-UCLA Medical Center, Torrance, California Purpose: To compare the usefulness of two different methods of reconstructing images from electron-beam CT coronary angiography. Materials and Methods: Twenty patients underwent conventional coronary angiography and contrast-enhanced electron-beam CT (CTA) for evaluation of coronary artery stenoses. Curved multiplanar reformations (MPR) and sliding thin-slab maximum intensity projections (STS-MIP) were reconstructed from the CTA data. The MPR and STS-MIP images were read independently of each other without knowledge of the results of conventional angiography. Results: Due to motion unsharpness, 9 of 80 vessels could not be evaluated. Using STS-MIP, overall sensitivity for detection of coronary artery stenoses was 80% and specificity was 86%. For the left main (LM) artery, specificity was 100%. For the left anterior descending artery (LAD) sensitivity was 91%, and specificity 75%. For the circumflex artery (LCX), sensitivity was 75% and specificity 77%. For the right coronary artery (RCA), sensitivity was 60% and specificity was 80%. Using MPR, overall sensitivity was 90% and specificity 80%. Specificity in the LM was 100%. For the LAD, sensitivity was 91% and specificity was 63%. For the LCX, sensitivity was 100% and specificity 69%. For the RCA, sensitivity was 80% and specificity was 70%. Overall concordance between STS-MIP and MPR was 79%. Concordance was best in the proximal arterial segments. Conclusions: MPR and STS-MIP reconstructions are useful for evaluation of coronary CTA. For identification of coronary stenoses, the sensitivity of MPR is slightly higher than that of STS-MIP, but the specificity is lower. Electron B e a m T o m o g r a p h y (EBT) - First Clinical Results of a N e w T e c h n i c a l A p p r o a c h to Computerized T o m o g r a p h i c Angiography (CTA) K.J. Lehmann(MD), G. Weisser (MD, MSc), K.W. Neff (MD, MSc), St. Denk (MD), Georgi (MD) Purpose: To evaluate the suitability of computerized tomographic angiography (CTA) using EBT with fast continuous volume scanning. MethodsflVIaterials An EBT scanner ("Evolution XP") with the new software version 12.34 was available since April 1997. With continuous volume scanning 140 images (3mm collimation, overlapping image reconstruction, flexible table movement, 200 msec. exposure time) can be acquired within 17 seconds. After test bolus injection 80 ml contrast material was infused with a flow of 4ml/second. According to different scan ranges 4 protocols for CTA using EBT were established. 105 patients were evaluated for atherosclerotic disease of the thoracic aorta, abdominal aorta, total aorta, renal arteries or carotid arteries. Density values were measured along the vessel course. The quality of MIP and SSD display was scored on a 4 step scale (1 = very good, 4 = insufficient). Results: Very high and homogenous density values above 230 Hus were achieved along the major vessels. Thus, 3D postprocessing could be performed easily using standard software on a Magic View workstation. MIP and SSD presentation demonstrated very good z-axis resolution using 3 m m collimation, 2-4 m m table movement and
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overlapping image reconstruction. The average quality score was 1.22 for the aorta and 1.56 for major visceral arteries. Different table movements up to 7 m m allow a maximum scan range of 42-49 cm (total aorta), 28 cm (thoracic or abdominal aorta), 21 cm (carotid arteries) or 14 cm (renal arteries). In a few cases pulsatile artifacts restrict the quality of 3D presentation, particularly in younger patients.
Conclusion: EBT seems to be a very promising new modality for Cta of several anatomic regions. Fast continuous volume scanning demonstrates high quality of 3D presentation of CTA, especially due to good zaxis resolution. Comparison of Shaded Surface Display and Curved Multiplanar Reconstructions for t h e Evaluation of Electron B e a m C T Angiography of t h e Coronary Arteries S. Achenbach, J. Nossen, W. Moshage, W.G. Daniel
Medizinische Klinik IImit Poliklinik Friedrich-Alexander-Universit~t Erlangen-Niirnberg, Germany The best method for the evaluation of contrast-enhanced electron beam CT (EBCT) data sets of the coronary arteries has not been defined yet. So far, shaded surface display (SSD) reconstructions have been favored, but manual segmentation of the data sets requires a long time. Additionally, information is lost due to thresholding. Curved multiplanar reconstructions (MPR) can be rendered very quickly with dedicated software and do not require thresholding. We directly compared these two methods of image reconstruction concerning the visualization of coronary artery stenoses. The EBCT data sets of 42 patients (40 to 45 axial cross-sections, 3 m m slice thickness, i m m overlap, 120 - 160 ml of contrast agent i.v.) were evaluated by shaded surface reconstructions (threshold: 80 to 100 HU) after manual segmentation of the data set to remove all structures covering parts of the coronary arteries and by curved multiplanar reconstructions (MPR). MPR were rendered by creating secondary images along a curved plane which followed the course of the coronary artery through the volume data set; as a result, the complete length of the coronary artery is visualized in one image. The reconstructions were evaluated as to the presence of high-grade stenoses or occlusions in the proximal 2 / 3 of the major coronary arteries, results were compared to invasive coronary angiography in a blinded fashion. A total of 168 coronary arteries had to be assessed (left main, left anterior descending, left circumflex, and right coronary artery in 42 patients). In the SSD reconstructions, 18 coronary arteries could not be evaluated due to artifacts. In the remaining 150 arteries, 19 out of 20 high-grade stenoses were detected correctly (95% sensitivity), and in 125 out of 130 arteries, absence of stenosis was correctly identified (96% specificity). By curved MPR, 25 arteries could not be evaluated. In the remaining 143 arteries, 19/21 stenoses were detected correctly (90% sensitivity) and in 110 out of 120 arteries, absence of stenosis was correctly identified (90% specificity). In summary, curved multiplanar reconstructions are a valuable alternative to shaded surface display reconstructions for the evaluation of contrast-enhanced EBCT investigations of the coronary arteries.
Visualization of t h e Coronary Arteries by Electron B e a m C o m p u t e d T o m o g r a p h y C o m p a r e d to Conventional Angiography in 17 Patients ML Clouse MD et al.
New England Deaconess Medical Center, Boston, MA We compared contrast-enhanced electron beam computed tomography (EBT) to conventional angiography for the detection of highgrade stenoses and occlusion of native coronary arteries.
University of California, San Francisco and Harbor-UCLA Medical Center, Torrance, California Purpose: To compare the usefulness of two different methods of reconstructing images from electron-beam CT coronary angiography. Materials and Methods: Twenty patients underwent conventional coronary angiography and contrast-enhanced electron-beam CT (CTA) for evaluation of coronary artery stenoses. Curved multiplanar reformations (MPR) and sliding thin-slab maximum intensity projections (STS-MIP) were reconstructed from the CTA data. The MPR and STS-MIP images were read independently of each other without knowledge of the results of conventional angiography. Results: Due to motion unsharpness, 9 of 80 vessels could not be evaluated. Using STS-MIP, overall sensitivity for detection of coronary artery stenoses was 80% and specificity was 86%. For the left main (LM) artery, specificity was 100%. For the left anterior descending artery (LAD) sensitivity was 91%, and specificity 75%. For the circumflex artery (LCX), sensitivity was 75% and specificity 77%. For the right coronary artery (RCA), sensitivity was 60% and specificity was 80%. Using MPR, overall sensitivity was 90% and specificity 80%. Specificity in the LM was 100%. For the LAD, sensitivity was 91% and specificity was 63%. For the LCX, sensitivity was 100% and specificity 69%. For the RCA, sensitivity was 80% and specificity was 70%. Overall concordance between STS-MIP and MPR was 79%. Concordance was best in the proximal arterial segments. Conclusions: MPR and STS-MIP reconstructions are useful for evaluation of coronary CTA. For identification of coronary stenoses, the sensitivity of MPR is slightly higher than that of STS-MIP, but the specificity is lower. Electron B e a m T o m o g r a p h y (EBT) - First Clinical Results of a N e w T e c h n i c a l A p p r o a c h to Computerized T o m o g r a p h i c Angiography (CTA) K.J. Lehmann(MD), G. Weisser (MD, MSc), K.W. Neff (MD, MSc), St. Denk (MD), Georgi (MD) Purpose: To evaluate the suitability of computerized tomographic angiography (CTA) using EBT with fast continuous volume scanning. MethodsflVIaterials An EBT scanner ("Evolution XP") with the new software version 12.34 was available since April 1997. With continuous volume scanning 140 images (3mm collimation, overlapping image reconstruction, flexible table movement, 200 msec. exposure time) can be acquired within 17 seconds. After test bolus injection 80 ml contrast material was infused with a flow of 4ml/second. According to different scan ranges 4 protocols for CTA using EBT were established. 105 patients were evaluated for atherosclerotic disease of the thoracic aorta, abdominal aorta, total aorta, renal arteries or carotid arteries. Density values were measured along the vessel course. The quality of MIP and SSD display was scored on a 4 step scale (1 = very good, 4 = insufficient). Results: Very high and homogenous density values above 230 Hus were achieved along the major vessels. Thus, 3D postprocessing could be performed easily using standard software on a Magic View workstation. MIP and SSD presentation demonstrated very good z-axis resolution using 3 m m collimation, 2-4 m m table movement and
$150
overlapping image reconstruction. The average quality score was 1.22 for the aorta and 1.56 for major visceral arteries. Different table movements up to 7 m m allow a maximum scan range of 42-49 cm (total aorta), 28 cm (thoracic or abdominal aorta), 21 cm (carotid arteries) or 14 cm (renal arteries). In a few cases pulsatile artifacts restrict the quality of 3D presentation, particularly in younger patients.
Conclusion: EBT seems to be a very promising new modality for Cta of several anatomic regions. Fast continuous volume scanning demonstrates high quality of 3D presentation of CTA, especially due to good zaxis resolution. Comparison of Shaded Surface Display and Curved Multiplanar Reconstructions for t h e Evaluation of Electron B e a m C T Angiography of t h e Coronary Arteries S. Achenbach, J. Nossen, W. Moshage, W.G. Daniel
Medizinische Klinik IImit Poliklinik Friedrich-Alexander-Universit~t Erlangen-Niirnberg, Germany The best method for the evaluation of contrast-enhanced electron beam CT (EBCT) data sets of the coronary arteries has not been defined yet. So far, shaded surface display (SSD) reconstructions have been favored, but manual segmentation of the data sets requires a long time. Additionally, information is lost due to thresholding. Curved multiplanar reconstructions (MPR) can be rendered very quickly with dedicated software and do not require thresholding. We directly compared these two methods of image reconstruction concerning the visualization of coronary artery stenoses. The EBCT data sets of 42 patients (40 to 45 axial cross-sections, 3 m m slice thickness, i m m overlap, 120 - 160 ml of contrast agent i.v.) were evaluated by shaded surface reconstructions (threshold: 80 to 100 HU) after manual segmentation of the data set to remove all structures covering parts of the coronary arteries and by curved multiplanar reconstructions (MPR). MPR were rendered by creating secondary images along a curved plane which followed the course of the coronary artery through the volume data set; as a result, the complete length of the coronary artery is visualized in one image. The reconstructions were evaluated as to the presence of high-grade stenoses or occlusions in the proximal 2 / 3 of the major coronary arteries, results were compared to invasive coronary angiography in a blinded fashion. A total of 168 coronary arteries had to be assessed (left main, left anterior descending, left circumflex, and right coronary artery in 42 patients). In the SSD reconstructions, 18 coronary arteries could not be evaluated due to artifacts. In the remaining 150 arteries, 19 out of 20 high-grade stenoses were detected correctly (95% sensitivity), and in 125 out of 130 arteries, absence of stenosis was correctly identified (96% specificity). By curved MPR, 25 arteries could not be evaluated. In the remaining 143 arteries, 19/21 stenoses were detected correctly (90% sensitivity) and in 110 out of 120 arteries, absence of stenosis was correctly identified (90% specificity). In summary, curved multiplanar reconstructions are a valuable alternative to shaded surface display reconstructions for the evaluation of contrast-enhanced EBCT investigations of the coronary arteries.
Visualization of t h e Coronary Arteries by Electron B e a m C o m p u t e d T o m o g r a p h y C o m p a r e d to Conventional Angiography in 17 Patients ML Clouse MD et al.
New England Deaconess Medical Center, Boston, MA We compared contrast-enhanced electron beam computed tomography (EBT) to conventional angiography for the detection of highgrade stenoses and occlusion of native coronary arteries.