Imaging Radiation-Induced Gastrointestinal, Bone Marrow Injury and Recovery Kinetics Using 18F-FDG PET

Abstract

Positron emission tomography using 18F-Fluro-deoxy-glucose (18F-FDG) is a useful tool to detect regions of inflammation in patients. We utilized this imaging technique to investigate the kinetics of gastrointestinal recovery after radiation exposure and the role of bone marrow in the recovery process. Male Sprague-Dawley rats were either sham irradiated, irradiated with their upper half body shielded (UHBS) at a dose of 7.5 Gy, or whole body irradiated (WBI) with 4 or 7.5 Gy. Animals were imaged using 18F-FDG PET/CT at 5, 10 and 35 days post-radiation exposure. The gastrointestinal tract and bone marrow were analyzed for 18F-FDG uptake. Tissue was collected at all-time points for histological analysis. Following 7.5 Gy irradiation, there was a significant increase in inflammation in the gastrointestinal tract as indicated by the significantly higher 18F-FDG uptake compared to sham. UHBS animals had a significantly higher activity compared to 7.5 Gy WBI at 5 days post-exposure. Animals that received 4 Gy WBI did not show any significant increase in uptake compared to sham. Analysis of the bone marrow showed a significant decrease of uptake in the 7.5 Gy animals 5 days post-irradiation, albeit not observed in the 4 Gy group. Interestingly, as the metabolic activity of the gastrointestinal tract returned to sham levels in UHBS animals it was accompanied by an increase in metabolic activity in the bone marrow. At 35 days post-exposure both gastrointestinal tract and bone marrow 18F-FDG uptake returned to sham levels. 18F-FDG imaging is a tool that can be used to study the inflammatory response of the gastrointestinal tract and changes in bone marrow metabolism caused by radiation exposure. The recovery of the gastrointestinal tract coincides with an increase in bone marrow metabolism in partially shielded animals. These findings further demonstrate the relationship between the gastrointestinal syndrome and bone marrow recovery, and that this interaction can be studied using non-invasive imaging modalities.

Acute and late effects of combined internal and external radiation exposures on the hematopoietic system

“…Together, these findings confirmed the work of multiple other investigators (e.g. Tang et al 2017;Li et al 2018) who have demonstrated that the irradiated hematopoietic system appears to fully recover within 1-2 months, with circulating blood counts, etc., returning to pre-exposure baseline levels. Nonetheless, some groups have reported delayed defects in the HSC compartment following TBI (e.g.…”

Combined tumor plus nontumor interim FDG‐PET parameters are prognostic for response to chemoradiation in squamous cell esophageal cancer

“…Another limitation of interim PET during CRT is the increased uptake of normal tissue, especially mucosa and gut. Preclinical and clinical studies have shown that there is a correlation between radiation-induced inflammation and FDG uptake [33][34][35] and FDG-PET is also used in several inflammatory diseases. 36 The increased normal tissue uptake hampers evaluation of tumor response and may have led to negative studies on response assessment in interim PET.…”

“…After a radiation dose of 50 Gy to the tumor, affected lymph nodes, safety margins, and elective lymph nodes, a consecutive boost of 4-16 Gy was prescribed to tumor/affected lymph nodes (average total dose: 58.9 Gy) with reduced margins. Concomitant chemotherapy consisted of two cycles of cisplatin (25 mg/m 2 /day, Days 1-3 and Days 29-31) and either paclitaxel (135 mg/m 2 /day, Day 1 and Day 29) or 5-fluorouracil (500 mg/m 2 /day, Days 1-5 and Days [29][30][31][32][33].…”

The Efficacy of Photobiomodulation Therapy in Improving Tissue Resilience and Healing of Radiation Skin Damage

“…Most tumors and inflammatory lesions lesion have increased uptake of 18 F-FDG owing to enhanced glucose utilization [29,37]. More recently, several studies have examined the ability of 18 F-FDG uPET-CT imaging to assess radiation damage [38,39]. This study noted a prominent increase in signal in the radiation-alone group that was dramatically reduced with PBM treatments.…”