Radiological changes with magnetic resonance imaging and computed tomography after irradiating minipig mandibles: The role of T2-SPIR mixed signal intensities in the detection of osteoradionecrosis.
OBJECTIVE
Radiotherapy in the head and neck can induce several radiologically detectable changes in bone, osteoradionecrosis (ORN) among them. The purpose is to investigate radiological changes in mandibular bone after irradiation with various doses with and without surgery and to determine imaging characteristics of radiotherapy and ORN in an animal model.


METHODS
Sixteen Göttingen minipigs were divided into groups and were irradiated with two fractions with equivalent doses of 0, 25, 50 and 70 Gray. Thirteen weeks after irradiation, left mandibular teeth were removed and dental implants were placed. CT-scans and MR-imaging were made before irradiation and twenty-six weeks after. Alterations in the bony structures were recorded on CT-scan and MR-imaging and scored by two head-neck radiologists.


RESULTS
Increased signal changes on MR-imaging were associated with higher radiation doses. Two animals developed ORN clinically. Radiologically mixed signal intensities on T2-SPIR were seen. On CT-scans cortical destruction was found in three animals. Based on imaging, three animals were diagnosed with ORN.


CONCLUSIONS
Irradiation of minipig mandibles with various doses induced damages of the mandibular bone. Imaging with CT-scan and MR-imaging showed signal and structural changes that can be interpreted as prolonged and insufficient repair of radiation induced bone damages.
Department of Cranio-Maxillofacial Surgery, Maastricht University Medical Centre, Maastricht, The Netherlands; GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands. Electronic address: l.poort@mumc.nl.
Lucas J
LJ
Poort
Department of Radiology, Maastricht University Medical Centre, Maastricht, The Netherlands.
Alida A
AA
Postma
Department of Radiology, Maastricht University Medical Centre, Maastricht, The Netherlands.
Annika A R
AAR
Stadler
Department of Cranio-Maxillofacial Surgery, Maastricht University Medical Centre, Maastricht, The Netherlands; GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands.
Roland A
RA
Böckmann
GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands; Department of Radiation Oncology (MAASTRO), Maastricht University Medical Centre, Maastricht, The Netherlands.
Frank J
FJ
Hoebers
Department of Cranio-Maxillofacial Surgery, Maastricht University Medical Centre, Maastricht, The Netherlands; GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands.
Peter A W H
PAWH
Kessler
D000818:Animals; D004195:Disease Models, Animal; D004307:Dose-Response Relationship, Radiation; D005260:Female; D008279:Magnetic Resonance Imaging; D008334:Mandible / Q000000981:diagnostic imaging / Q000528:radiation effects*; D008336:Mandibular Diseases / Q000000981:diagnostic imaging*; D010025:Osteoradionecrosis / Q000000981:diagnostic imaging*; D013552:Swine; D013556:Swine, Miniature; D014057:Tomography, X-Ray Computed
Animal experiment; Irradiation; Mandible; Osteoradionecrosis; Radiological changes