Dynamic multi-pinhole collimated brain SPECT of Parkinson's disease by [123I]FP-CIT: a feasibility study of fSPECT.

We investigated the feasibility of using a dopamine transporter (DaT) tracer ligand ([123I]FP-CIT) along with novel multi-pinhole brain collimators for dynamic brain single photon emission computed tomography (SPECT) in suspected Parkinson's disease patients. Thirteen patients underwent dynamic tracer acquisitions before standard imaging. Uptake values were corrected for partial volume effects. Specific binding ratio (SBRcalc) was calculated, reflecting binding potential relative to non-displaceable binding (BPND) in the cortex. Additional pharmacokinetic parameters (BPND, R1, k2) were estimated using the simplified reference tissue model, revealing differences between Kahraman low-score (LS) and high-score (HS) groups. Results showed increasing striatal tracer uptake until 100 min post-injection, with consistent values afterward. Uptake and SBRcalc ratios matched visual assessment. LS patients had lower putamen than caudate nucleus tracer uptake, decreased BPND values, while R1 and k2 values were comparable to HS patients. In conclusion, dynamic multi-pinhole SPECT using DaT tracer with the extraction of pharmacokinetic parameters is feasible and could help enable early differentiation of reduced and normal DaT values.

Positron emission tomography/computer tomography in gastrointestinal malignancies: current potential and challenges.

The use of 18F-Fluoro-D-deoxy-glucose -positron emission tomography/computed tomography (FDG-PET/CT) in gastrointestinal (GI)-malignancies may not be as straightforward as in many other cancers, but the potential is clearly there in select clinical settings. The challenges include the relative non-specificity of FDG, the variable degrees of physiologic FDG-uptake, and the heterogeneous FDG-uptake in different cell types within the GI-domain, which all together hamper the use in primary diagnostics. In general, the literature is older, heterogeneous, and based on stand-alone PET, which is now largely considered obsolete. There is emerging evidence for use of hybrid PET/CT, but the literature is still relatively sparse. The main indications are preoperative staging of distant metastases, not only in limited disease but also before curative treatment of limited metastatic disease. Controversies remain concerning liver metastases but improved technology boast well for the future role of FDG-PET/CT not least concerning equivocal findings on conventional imaging. In our opinion, an important upcoming indication is early response assessment, perhaps mostly in the neoadjuvant settings of upper GI-malignancies, but standardization of response assessment criteria is lacking before a more widespread implementation is feasible. Finally, there seems to be a significant role in recurrence detection, especially in CRC.