O-1 Human Radiation Dosimetry Using Electron Paramagnetic

O-1 Human Radiation Dosimetry Using Electron Paramagnetic Resonance in Tooth Enamel Biopsy Samples Barry Pass1), Alexander Romanyukha2), Tania De1), Lyudmila Romanyukha2), Francois Trompier3), Isabelle Clairand3), Prabhakar Misra1), Luis Benevides2), David Schauer4) 1)Howard University, Washington, DC, 2)Uniformed Services University of the Health Sciences, Bethesda, MD, 3)French Institute for Radiological Protection and Nuclear Safety, Fontenay-aux-roses, 4)National Council on Radiation Protection, Washington, DC e-mail: [email protected] Purposes: Dental enamel is the only living tissue that indefinitely maintains a record of its exposure to ionizing radiation. Electron paramagnetic resonance (EPR) dosimetry in tooth enamel has been applied for dose reconstruction for epidemiological studies of dif- ferent cohorts, including Hiroshima atomic bomb survivors, Chernobyl clean-up workers and other victims of unintended exposures to ionizing radiation. Several international inter-comparisons of EPR enamel dosimetry have demonstrated a high accuracy and reli- ability for this method. The main disadvantage of standard EPR enamel radiation dosimetry, however, is the necessity for large, 100 mg, enamel samples to achieve adequate signal-to-noise. This necessitates the use of extracted teeth for dose measurements, making the application of EPR in dental enamel for immediate, after-the-fact dosimetry problematic. The present study endeavored to improve the sensitivity of EPR measurements sufficiently to make the use of minimally-invasive in vivo enamel biopsies feasible for retrospective radiation dosimetry. Materials and methods: Enamel samples were obtained from teeth extracted in the normal course of dental treatment. Enamel biopsy samples of 2-4 mg in weight were obtained using a high-speed dental hand-piece with a tapered fissure or diamond bur, and an enamel chisel. EPR measurements were performed at microwave frequencies in the standard X-band (9 GHz) and at higher frequencies in the Q-band (34GHz). Results: Q-band EPR measurements completely resolved the radiation-induced EPR signal in enamel from the radiation-independent native, background EPR signal--which is the major limiting factor in sensitivity for X-band EPR. A comparative study of electron paramagnetic resonance radiation dosimetry in Q- and X-bands showed that Q-band is able to provide accurate measurements of radiation doses below 0.5 Gy, with tooth enamel samples as small as 2 mg. This sample size is less than 1% of the total amount of tooth enamel in a molar tooth. Conclusion: Q-band EPR in dental enamel significantly increases the sensitivity for detecting absorbed ionizing radiation by completely resolving the radiation-induced EPR signal from the radiation-independent native, background EPR signal. An enamel sample of 2 mg can be easily obtained in an emergency requiring rapid, after-the-fact radiation dose measurements. And, the minimal enamel defect can be rapidly and readily restored using modern, light-cured restorative composites. It is estimated the biopsy and restoration of the enamel defect can be done by a skilled operator in approximately 3 minutes. Separation of the radiation-induced and the radiation-independent native, background EPR signals makes dose response measurements much easier in comparison with conventional X-band measurements in which these signals overlap, necessitating special methods for measuring radiation doses below 0.5 Gy. We also have tested Q-band EPR radiation dosimetry in micro-samples of bone, dentine and fingernails. The overall results are very promising. We believe that application of Q-band measurements could have significant impact on EPR human biodosimetry. One could also envision the development of a fast and less invasive method for collection of small enamel samples for EPR Q-band dose measurements in radiation accident scenarios, and for obtaining enamel samples for randomized clinical studies of radiation exposure in the general population. O-2 Diagnostic image of dental ankylosis by Limited cone beam CT : Two cases reports C Igarashi1), K Kobayashi1), S Shimoda2), M Imanaka1), T Osano1), T Yoshizawa3), H Kashiwabara1), T Komahashi1) 1)Dept. of Oral Radiology, Tsurumi University, School of Dental Medicnie, Kanagawa, 2)First Dept. of Oral Anatomy, Tsurumi University, School of Dental Medicnie, , Kanagawa, 3)Dept. of Orthodontics, Tsurumi University, School of Dental Medicnie, , Kanagawa e-mail: [email protected] Purposes: In the permanent tooth delayed case presented conventional radiographs did not help in the diagnosis. It reports on the dental ankylos is that underwent limited cone beam CT and to assess limited cone beam CT is useful in diagnosis these cases. Materials and methods: Case 1. Eight years old girl was referred by dental office with chief complaint of malocclusion. There fistel formation right upper right central incisor region. Impaction of the tooth , hypoplasia of the root and radiolucent area around the crown were reveled on radiographs. The limited cone beam CT was performed on PSR-9000 (Asahi Roentgen Ind. Co., Ltd. Kyoto Japan). The ill-defined resorpution on the cervical margin of tooth and radiolucent area around the crown recommended on image. In image diagnosis was dentigerous cyst and dental ankylosis. After diagnostic imaging a tooth was extracted. And it was diagnosed by the pathological examination of the dentigerous cyst and the dental ankylosis. Case2. Fourteen years old boy was referred by dental office with chief complaint of malocclusion. There is no change though the orth- odontic therapy is begun for the delay of the upper right central incisor tooth. The limited cone beam CT was performed on PSR-9000 (Asahi Roentgen Ind. Co., Ltd. Kyoto Japan). The ill-defined resorpution on the cervical margin of tooth was recommended on image. In image diagnosis was the adhesion teeth. After diagnostic imaging a tooth was extracted. And it was diagnosed by the pathological examination of the dental ankylosis. A tooth was extracted, and it was diagnosed by the pathol- ogy examination of the dental ankylosis. Result: The ill-defined resorpution on the impacted tooth not admitted on conventional radiography was detected in limited cone beam CT. Conclusion: The limited cone beam CT was very useful in the diagnosis of the dental ankylosis. Therefore the limited cone beam CT scan is the effective imaging methods for diagnosis dental ankylosis and the decision of the treatment methods. 76 O-3 Possible prognostic radiological criteria concerning the bisphosphonate-related- osteonecrosis of the jaw based on CBCT imaging D Schulze, C Alamanos, MC Metzger Albert-Ludwigs-University Freiburg, Freiburg, Germany e-mail: [email protected] Purposes: To assess the morbidity of bisphosphonate-related-Osteonecrosis of the jaw (BRONJ) in accordance to the radiological findings acquired by CBCT-imaging. Materials and methods: This retrospective study involved 50 BRONJ patients who were treated with i.v. bisphosphonates and were examined with the ProMax 3D Unit (Planmeca Oy, Helsinki Finland). The radiological criteria used to evaluate the severity of the disease include: single or multiple irregular radiolucencies or osteolysis showing a moth-eaten appearance, areas of sequestration, ill-defined cortical borders, areas of diffuse radiopacity, bone expansion and periosteal reaction. The radiological findings were correlated to the clinical status-quo and the persistence of the disease. Results: This study shows that recalcitrant cases of BRONJ acquire a complex radiological profile with mixed radiolucencies and radiopacities and regional formation of sequestra. In early stages the disease can be defined by the incipient alterations of the trabecular pattern of the surrounding cancellous bone. Acute phases of the disease appear with a periosteal reaction (osteo- myelitis with periostitis), whereas more asymptomatic cases reveal a more compensatory profile with predominating sclerotis- ing areas. Finally an osteolytic affection of the cortical borders of the mandible leads to a higher possibility of a pathological fracture. Conclusion: CBCT-modality can be used not only to establish the diagnosis of BRONJ, but also to determine the stage and the prognosis, especially in terms of a follow-up examination. O-4 Conversion of Conventional Radiographic Examination of Trabecular Bone Pattern Value into the Value of Density Measurement from Intra Oral Digital Radiography M Priaminiarti1), B Utomo2), R Susworo3), HB Iskandar1) 1)Department of Dental and Maxillofacial Radiology, Faculty of Dentistry University of Indonesia, Jakarta, 2)Department of Biostatistics and Health Information, Faculty of Public Health University of Indonesia, Jakarta, 3)Department of Radiotherapy, Faculty of Medicine University of Indonesia, Jakarta e-mail: [email protected] Purposes: To determine conversion value of gray scale density measurement from intra oral conventional radiographic examination of edentulous maxilla and mandible using intra oral digital radiography, as one effort to increase the value of conventional radiograph in diagnostic procedure. Materials and methods: Periapical radiography examination of pararelling technique both conventional radiography and the digital ones were performed on 18 male and 34 female patients with edentulous maxilla and mandible. The trabecular bone pattern of 42 maxillary region and 61 mandibular region in the region of interest was classified into five

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