Deformable and rigid
registration of MRI and microPET images for
photodynamic therapy of cancer in mice
We are
investigating imaging techniques to study the tumor
response to photodynamic therapy (PDT). Positron
emission tomography (PET) can provide physiological
and functional information. High-resolution magnetic
resonance imaging (MRI) can provide anatomical and
morphological changes. Image registration can
combine MRI and PET images for improved tumor
monitoring. In this study, we acquired
high-resolution MRI and microPET
18F-fluorodeoxyglucose (FDG) images from C3H mice
with RIF-1 tumors that were treated with Pc 4-based
PDT. We developed two registration methods for this
application. For registration of the whole mouse
body, we used an automatic three-dimensional,
normalized mutual information algorithm. For tumor
registration, we developed a finite element model
(FEM)-based deformable registration scheme. To
assess the quality of whole body registration, we
performed slice-by-slice review of both image
volumes; manually segmented feature organs, such as
the left and right kidneys and the bladder, in each
slice; and computed the distance between
corresponding centroids. Over 40 volume registration
experiments were performed with MRI and microPET
images. The distance between corresponding centroids
of organs was 1.5 +/- 0.4 mm which is about 2 pixels
of microPET images. The mean volume overlap ratios
for tumors were 94.7% and 86.3% for the deformable
and rigid registration methods, respectively.
Registration of high-resolution MRI and microPET
images combines anatomical and functional
information of the tumors and provides a useful tool
for evaluating photodynamic therapy.
PMID: 16878577
[PubMed - indexed for MEDLINE]