RT Journal Article SR Electronic T1 Dual-Isotope SPECT Using 99mTc-Hydroxymethylene Diphosphonate and 201Tl-Chloride to Assess Mandibular Invasion by Intraoral Squamous Cell Carcinoma JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1464 OP 1468 VO 43 IS 11 A1 Yuka Yamamoto A1 Yoshihiro Nishiyama A1 Katashi Satoh A1 Yumiko Ohbayashi A1 Akinori Iwasaki A1 Kazunori Miyabe A1 Motoomi Ohkawa YR 2002 UL http://jnm.snmjournals.org/content/43/11/1464.abstract AB We examined mandibular invasion of intraoral squamous cell carcinoma by simultaneous bone and tumor dual-isotope SPECT using 99mTc-hydroxymethylene diphosphonate (99mTc-HMDP) and 201Tl-chloride (201Tl) and by CT. Methods: Early and delayed simultaneous bone and tumor dual-isotope SPECT and CT were performed on 39 patients suspected of having tumor invasion of the mandible by intraoral squamous cell carcinoma. SPECT images were superimposed to project tumor location from tumor SPECT onto the osseous structures shown by bone SPECT. The CT imaging protocol consisted of 5-mm contiguous axial images. Results: Histopathologic examination revealed invasion of the mandible in 13 patients and no tumor invasion in 26 patients. The results of delayed dual-isotope SPECT were exactly the same as those of early dual-isotope SPECT. On early and delayed dual-isotope SPECT, the sensitivity, specificity, and accuracy in detecting mandibular invasion by intraoral squamous cell carcinoma were 100% (13/13), 88.5% (23/26), and 92.3% (36/39), respectively. The corresponding values using CT were 45.5% (5/11), 94.7% (18/19), and 76.7% (23/30), respectively, when 9 patients were excluded because of dental artifacts. Conclusion: Our results suggest that superimposed early bone and tumor dual-isotope SPECT images alone may be sufficient in the diagnostic evaluation of mandibular invasion by intraoral squamous cell carcinoma.