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AJNR - American Journal of Neuroradiology

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Bone-Subtraction CT Angiography: Evaluation of Two Different Fully Automated Image-Registration Procedures for Interscan Motion Compensation

M.M. Lell^a, H. Ditt^b, C. Panknin^a,b, J.W. Sayre^a,c, S.G. Ruehm^a, E. Klotz^b, B.F. Tomandl^d and J.P. Villablanca^a

^a Department of Radiological Sciences, David Geffen School of Medicine at the University of California, Los Angeles, Calif
^b Siemens Medical Solutions, Forchheim, Germany
^c Department of Biostatistics, the University of California, Los Angeles School of Public Health, Los Angeles, Calif
^d Department of Neuroradiology, Klinikum Bremen-Mitte, Bremen, Germany

View larger version (132K): [in this window] [in a new window]   Fig 1. Comparison of BSCTA with rigid registration BSCTA, SB-BSCTA, and PR-BSCTA: CTA (MIP) shows a patient with high-grade stenosis of left ICA. Rigid registration leads to insufficient removal of the lower cervical spine (A, Lateral. B, Frontal projection). The edges of the individual registration slabs from SB-BSCTA (C and D) can be identified by the bone remnants from the mandible and cervical spine (arrows). Weighting of total bone mass within each slab is performed in this algorithm, explaining the distribution of the bone remnants. PR-BSCTA (E and F) demonstrates almost complete elimination of the bone pixels from the mandible and cervical spine. The thyroid cartilage remains misregistered with both approaches.

View larger version (78K): [in this window] [in a new window]   Fig 2. CTA (MIP, frontal [A and C] and lateral [B and D] views) shows a patient with atherosclerotic disease at the carotid bifurcation and siphon. Correct registration and successful removal of the calcified plaque at the carotid siphon is obtained with both registration techniques. Pulsation leads to incomplete removal at the left carotid bifurcation, more pronounced with SB-BSCTA (A and B), whereas removal of the calcifications at the right carotid bifurcation is almost perfect with both methods. Removal of the lower cervical spine is more complete with SB-BSCTA compared with PR-BSCTA (C and D). The OA (arrow) can be identified with both approaches. The right ECA is occluded.

View larger version (90K): [in this window] [in a new window]   Fig 3. CTA (MIP, frontal [A and C] and lateral [B and D] views) shows a patient with occlusion of the right carotid artery and steno-occlusive disease at the left carotid bifurcation and right VA. Both registration techniques provide excellent image quality; more bone remnants can be depicted with SB-BSCTA (A and B) in comparison with PR-BSCTA (C and D) in this patient.

View larger version (16K): [in this window] [in a new window]   Fig 4. Graphic representation of the individual motion amplitudes for each patient. Note that the patients are ranked by increasing complexity of motion. Trend lines indicate the displacement of different anatomic landmarks.

View larger version (13K): [in this window] [in a new window]   Fig 5. Graphic representation (and trend lines) of the quality scores achieved with the different techniques for individual vessels (A, VA. B, Cervical ICA. C, PC-ICA). There is a trend toward decreased image quality with increasing complexity of motion, expressed by the SD of the motion amplitudes except for the PC-ICA.