Biomedical Engineering Reference
In-Depth Information
FIGURE 11.11: (A) Maximum Likelihood (ML) PET reconstruction that
only used the PET raw data, (B) MAP-Reconstruction that used a joint en-
tropy prior based on an MRI image of the same patient, (C) MRI, (D) Stan-
dard Filtered Back Projection Reconstruction. Image with permission from
Nuyts et al. [28]
is not as straightforward as CT-AC that allows the estimation of 511 keV
attenuation maps from CT transmission images. In the absence of CT-like
transmission sources in PET/MR, alternative solutions to MR-AC include
the use of complex segmentation tools that were shown to work for brain
applications. In extra-cranial PET/MR the percentage of bone voxels is sig-
nificantly smaller and an accuracy sucient for many applications might be
achieved by simply \ignoring" bone, provided that the algorithm does not
falsely predict air at bone locations. If higher accuracy is required, other ap-
proaches that include atlas-based methods and simultaneous reconstruction
of attenuation and activity distributions allow predicition of bone attenuation
and appear more promising. While MR-AC is work-in-progress, further advan-
tages of MR-AC over CT-AC become apparent, which include the additional
use of MR for retrospective motion correction or partial volume correction of
the PET.
References
[1] T. Beyer, P.E. Kinahan, D.W. Townsend, and D. Sashin. The use of
x-ray CT for attenuation correction of PET data. In IEEE Conference
Record of the Nuclear Science Symposium and Medical Imaging Confer-
ence, volume 4, page 1573, 1994.
[2] T. Beyer, M. Weigert, C. Palm, H. Quick, S. Muller, U. Pietrzyk, F. Vogt,
M.J. Martinez, and A. Bockisch. Towards MR-based attenuation correc-
tion for whole-body PET/MR imaging. In Society of Nuclear Medicine
Annual Meeting Abstracts, volume 47, Supplement 1, page 384, 2006.
Search WWH ::
Custom Search