Value of PET/MR Enterography in the Assessment of Crohn's Disease Using a Collagen-binding Radiotracer.

Injection of Gallium-68 labeled collagen binding probe 8 (\[68Ga\]CBP8): All subjects will undergo placement of an intravenous catheter (IV). The catheter will be flushed post-injection of \[68Ga\]CBP8 with 0.9% saline solution. The subjects will be positioned on the scanner table; support devices under the back and/or legs will be used as needed to enable the patient to comfortably maintain his/her position throughout the scan; Up to 15 mCi of \[68Ga\]CBP8 will be administered. The injected dose and the time of injection will be recorded; Post scan: The catheter will be removed. The subject will be asked to void again immediately after the scan and he/she will be counseled on the importance of continuing to drink fluids for several more hours in order to increase urine flow rate and minimize the radiation dose to the bladder wall.

Dotarem 20ml will be injected during acquisition of contrast enhanced T1weighted fat saturated sequences, in keeping with standard of care MR enterography.

All subjects will undergo placement of an intravenous catheter (IV). Through the same catheter, 10 mL of venous blood will be collected to evaluate blood markers for fibrostenosis.

Glucagon will be injected into the subject's indwelling i.v. catheter (0.3-0.5 mg) before imaging acquisition; or intramuscularly (1-2 mg) prior to imaging the abdomen and pelvis. A second administration of IV glucagon (0.3-0.5mg) may take place during image acquisition.

MR and PET images of the abdomen and pelvis will be acquired using the Siemens 3 Tesla Biograph mMR scanner. Multiple anatomical and functional imaging sequences may be run to assess specific image quality measures in addition to those used for anatomical diagnosis. Among the sequences, patients will undergo a full set of standard of care MR enterography sequences to ensure they get at least same quality of study and of clinical information they would gain from a clinical study. Certain MR sequences scans may be repeated after varying a limited range of pulse sequence parameters to assess their effect on the image contrast, image artifacts and signal to noise ratio.

Patients will be invited to drink as much as possible of an oral contrast solution consisting of a mixture of 1500-2000 ml of dilute barium or sorbitol (VoLumen or Breeza) and water. Breeza, and in the past VoLumen, is routine clinical practice at MGH. The solution comes already prepared in bottles, so there is no need to dilute or prepare. The investigators will just hand the bottle to the patient and will ask the patient to start drinking \~1 hour before the scan. By routine practice at MGH, the investigators give 3-4 bottles of Breeza, about 1500-2000ml.