Biomedical Applications of Emission Tomography - Correction Techniques in Emission Tomography - page 25

FIGURE 2.7: (See color insert.) Imaging-guided gene therapy paradigm
of experimental gliomas. Protocol for identification of viable target tissue and
assessment of vector-mediated gene expression in vivo in a mouse model with
three subcutaneous growing gliomas. Row 1: localization of tumors by MRI.
Row 2: the viable target tissue as depicted by [ 18 F]FDG-PET. Note the signs
of necrosis in the lateral portion of the left-sided tumor (arrow). Rows 3{
4: following vector-application into the medial viable portion of the tumor
(arrow) the \tissue-dose" of vector-mediated gene expression is quantied by
[ 18 F]FHBG-PET. Row 3 shows an image acquired early after tracer injection,
which is used for coregistration. Row 4 displays a late image with specific
tracer accumulation in the tumor that is used for quantification.
cially important to guide biopsy, resection and radiation as well as to assess
the effect of therapy and rate of tumor progression.
The same imaging parameters have been used extensively in the past by
our group in experimental glioma models to further develop an imaging-guided
gene therapy paradigm, where vectors are transduced into the viable tumor
parts as identified by PET (Figures 2.7 and 2.8, [10]). The transduced tissue
dose of vector-mediated gene expression can by visualized by PET and can be
correlated to the induced therapeutic effect. We also observed that FLT can
serve as an early (within 4 days after onset of therapy) read-out parameter for