Investigation of VAP-1 Expression and Tissue Blood Flow by Combined [68Ga]DOTA-Siglec-9 and [15O]H2O PET-MRI in Patients With Small Bowel's Crohn's Disease

Patients with a strong suspicion of small bowel's CD after the colonoscopy and laboratory studies will be recruited to study protocol in the outpatient gastroenterology clinic of Turku University Hospital. After the signed informed consent patients will undergo combined [68Ga]Ga-DOTA-Siglec-9 and [15O]H2O PET/MRE, the MRE being part of their clinical diagnostics. If the MRE shows no signs/or mild inflammation of small intestine CD patients will be directed to small bowel capsule endoscopy (SBCE), which is routine in this clinical suspicion.

The patients will also have routine blood samples taken. A complete blood count (CBC), C-reactive protein (CRP), creatinine, alanine aminotransferase (ALAT), alkaline phosphatase (AFOS) and albumin will be analysed from each patient's blood sample, calprotectin and faecal microbiota will be analysed from stool. The tissue samples for (immuno)histological evaluation, proteome-wide mass spectrometry allowing sensitive site-specific detection of ADP-ribosylation and structural protein analysis will also be obtained in primary ileocolonoscopy (biopsies from the bowel wall).

Before the PET study starts, the patients will undergo screening procedures with physical examination, chemistry panel (electrolytes, creatinine, liver function), and acute phase reactants (ESR, CRP) and urine tests. In addition, serum/plasma biomarker sample, serum sample for soluble VAP-1 analysis, whole blood RNA sample, and whole blood DNA sample for gene variant analyses will be collected.

In the combined PET/MRE scanning the study subjects lay in the prone position on the PET scanner bed, and the area of interest (AOI) is positioned in the gantry and in the field of view.

[68Ga]Ga-DOTA-Siglec-9 and [15O]H2O PET/MRE imaging will be performed in the fasting state (at least 6 hours). The patients will be instructed to avoid caffeinated drinks during the last 24-hours before the study. A catheter will be inserted in an antecubital vein for injection of PET radiopharmaceutical. Another catheter will be inserted in the opposite radial or antecubital vein for blood sampling and the subjects will be placed in supine position in the PET/MRE scanner, arms next to the body. Ideally, urinary bladder should be empty before PET/MRE scan. The uptake of tracer will be measured using PET and MRE will be performed for anatomical reference.