Time‐course of effects of external beam radiation on [¹⁸F]FDG uptake in healthy tissue and bone marrow

Abstract

The utility of PET for monitoring responses to radiation therapy have been complicated by metabolically active processes in surrounding normal tissues. We examined the time‐course of [18F]FDG uptake in normal tissues using small animal‐dedicated PET during the 2 month period following external beam radiation. Four mice received 12 Gy of external beam radiation, in a single fraction to the left half of the body. Small animal [18F]FDG‐PET scans were acquired for each mouse at 0 (pre‐radiation), 1, 2, 3, 4, 5, 8, 12, 19, 24, and 38 days following irradiation. [18F]FDG activity in various tissues was compared between irradiated and non‐irradiated body halves before, and at each time point after irradiation. Radiation had a significant impact on [18F]FDG uptake in previously healthy tissues, and time‐course of effects differed in different types of tissues. For example, liver tissue demonstrated increased uptake, particularly over days 3–12, with the mean left to right uptake ratio increasing 52% over mean baseline values false(normalp<0.0001false). In contrast, femoral bone marrow uptake demonstrated decreased uptake, particularly over days 2–8, with the mean left to right uptake ratio decreasing 26% below mean baseline values false(normalp=0.0005false). Significant effects were also seen in lung and brain tissue. Radiation had diverse effects on [18F]FDG uptake in previously healthy tissues. These kinds of data may help lay groundwork for a systematically acquired database of the time‐course of effects of radiation on healthy tissues, useful for animal models of cancer therapy imminently, as well as interspecies extrapolations pertinent to clinical application eventually.PACs Number: 87.50.‐a

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

“…In addition to gastrointestinal tract, 18 F-FDG PET/CT imaging can also be utilized to investigate the effects of radiation on other parts of the body such as bone marrow metabolism [27, 41, 42]. Our results agrees with these findings and further demonstrate that 18 F-FDG PET/CT imaging can detect radiation-induced metabolic changes in the event of accidental exposure, which can be critical for determining survival.…”

Brain

“…A long-term consequence after radiotherapy may be a reduction up to −5% of cerebral metabolic activity in the irradiated brain tissue, as compared to non-irradiated brain tissue 65 .…”

How to Differentiate Benign versus Malignant Cardiac and Paracardiac18F FDG Uptake at Oncologic PET/CT

“…It is generally understood that FDG studies should be performed 2-3 months after radiation therapy to avoid the acute effects of post-radiation therapy inflammation (33). However, the effects of external-beam radiation therapy can be variable and depend on the amount and time course of radiation delivered (34). One review of patients with cancer and pericardial disease found that radiation-induced pericarditis is relatively rare and present in only 10% of patients, compared with benign idiopathic pericarditis in 32% and malignant pericardial disease in 58% (35).…”