Detection of Bone Marrow Edema Pattern With Dual-Energy Computed Tomography of the Pig Mandible Treated With Radiotherapy and Surgery Compared With Magnetic Resonance Imaging.

OBJECTIVE: The aim of the study was to investigate the accuracy of dual-energy computed tomography (DECT) compared with magnetic resonance (MR) imaging for the detection of edema of the mandible. MATERIALS AND METHODS: Fifteen adult Göttingen mini pigs received irradiation to the mandible with an equivalent dose of 0, 25, 50, or 70 Gy. Six months after irradiation, all animals underwent DECT and MR imaging of the mandible. Magnetic resonance short tau inversion recovery (STIR) was used for the grading of the bone marrow edema (0-3). Dual-energy CT (80 and 140 kVp) was performed, and virtual noncalcium (VNCa) images were calculated. RESULTS: Increased signal intensity at STIR was found in the higher radiation groups. An increase of signal intensity in MR imaging was accompanied by a significant increase in the Hounsfield unit value of the VNCa images of the bone marrow (STIR: 0, 1, 2, 3; mean Hounsfield unit: -103, -90, -76, -34, respectively; P < 0.05; R = 0.388). CONCLUSIONS: The VNCa images derived from DECT are able to demonstrate bone marrow edema in radiation-induced bone changes in the mandible.

The histological and histomorphometric changes in the mandible after radiotherapy: An animal model.

PURPOSE: Approximately 5% of irradiated head and neck cancer patients develop osteoradionecrosis of the mandible. The current non-surgical treatment options for osteoradionecrosis have limited effects and are based on a small number of studies. Therefore, we aimed to enhance the understanding of the pathophysiology of osteoradionecrosis by investigating changes induced by external irradiation in mini-pigs. METHODS: Sixteen Göttingen mini-pigs were divided into four groups for the application in two fractions with total equivalent radiation dosages of 25, 50, 70 Gray, and one group served as control. Thirteen weeks after irradiation, the left lateral teeth the mandible were removed and implants were placed. The pigs were sacrificed twenty-six weeks after irradiation, and the bone samples were stained with Masson's trichrome. RESULTS: The amount of fibrosis, resorption lacunae, necrosis, and the woven/lamellar bone ratios were increased after higher radiation dosages. The diameter of the lumen of the inferior alveolar artery was reduced depending on the irradiation dosages. The rate of bone remodeling decreased after irradiation. CONCLUSION: Both surgery and increasing irradiation dosages cause architectural bone changes and damage the vascularization. This might result in a chronic hypoxic state of the mandibular bone. In general, the bone formation rate was markedly decreased after radiotherapy.