PET scan with 6 hotspots, questions

I was diagnosed with a "working" diagnosis of Carcinoid Syndrome about 6 years ago. I get the flushing and the diarrhea, sandostatin makes things manageable. We have never been able to image a tumor, but I do have blood markers that have trended 3-4 times the high limit with pancreastatin, pancreatic polypeptide, norepinephrine, catchecholamine and PTH. The 24 hours urines have always been negative, but then I have never been symptomatic during the 24 hour urine. I also get a hypoglycemic type of attack that seems to occur randomly and for no reason. Blood sugar only goes down to mid 50's but i almost pass out and my vision is completely blocked by bright lights in my eyes for about 15 minutes when bs recovers to normal 100-120. I recently had a PET scan, keep in mind I have had numerous CT scans with and without contrast and they have all been completely negative. The PET scan showed 6 areas of high activity. 3 in my liver, one in my lung, one in my kidney and one in my large bowel. The SUV's were from 3.0 to 4.8. We are wondering why we cant image the tumor in any of these cases so that we can biopsy them and find out for sure what kind of tumor and how malignant they might be. Is it at all normal not to be able to image the tumor with such a high SUV? I have a lot of titanium fixation in my S1 to L3 vert as they are all fused. This causes a lot of artifacts in the imaging at those levels. But why can we image the one in the lung or the ones in my liver?? We are now stuck. They wont biopsy without an image, and wont plan treatment without biopsy. I am really worried since the SUV's are so high the doc is pretty sure of malignancy and that it has already metastisized due to the locations all over the proverbial map on the PET scan. Any ideas for further study or something would be a god send to me thank you all ahead of time, I am obviously a new poster here. jack