Computer-aided 3-D 99m Tc-DPD-SPECT reconstruction to assess mandibular invasion by intraoral squamous cell carcinoma: diagnostic improvement or not? Ronald Schimming, 1 Freimut D. Juengling, 2 Gu¨nter Lauer, 4 Carsten Alteho¨fer, 3 Rainer Schmelzeisen 1 1 Department of Oral and Maxillofacial Surgery (Head: Prof. Dr. Dr. R. Schmelzeisen); 2 Department of Nuclear Medicine (Head: Prof. Dr. Dr. E. Moser); 3 Department of Diagnostic Radiology (Head: Prof. Dr. M. Langer), University Hospital Freiburg, Hugstetterstr. 55, D-79106 Freiburg, Germany; 4 Department of Oral and Maxillofacial Surgery (Head: Prof. Dr. Dr. U. Eckelt) University Hospital Dresden, Fetscherstr. 74, D-01307 Dresden, Germany SUMMARY. Objective: A prospective study was designed to compare computer-aided 3-D 99m Tc-DPD-SPECT (Technetium-Dicarboxy propan-single photon emission CT) reconstruction with clinical examination, panoramic radiography, CT scan and conventional 99m Tc-DPD-SPECT investigation in the assessment of mandibular bone invasion by squamous cell carcinoma. Patients and Methods: Between October 1997 and December 1999, 88 patients with intraoral squamous cell carcinoma of the regions adjacent to the mandible were enrolled in this study. In 50 cases, mandibular resection (segmental or marginal) was performed based on the pre-treatment diagnostic results. Imaging studies were read independently by four experienced observers. Results: No differences could be found between presurgical 3-D 99m Tc-DPD-SPECT reconstruction and conventional 99m Tc-DPD-SPECT investigation. Both techniques revealed a sensitivity of 100% whereas CT scan showed the greatest specificity (93.8%). SPECT investigation had a specificity of 91.6% and the greatest efficiency (95.4%). The greatest predictive positive value was found for CT scan (92.3%). Clinical examination and panoramic radiography displayed the lowest sensitivity, 82.5% vs. 85.0%, and specificity, 79.2% vs. 89.5% respectively. Conclusion: This investigation does not provide evidence that 3-D 99m Tc-DPD-SPECT reconstruction has any advantages when compared to conventional 99m Tc-DPD-ECT investigation in the assessment of mandibular invasion by squamous cell carcinoma. Despite a sensitivity of 100% the specificity is still in need of improvement. Until newer methods or techniques become available the combination of CT scanning and conventional 99m Tc-DPD-SPECT investigation appears to be the best means of detecting tumour invasion preoperatively and is thus helpful in directing appropriate surgical procedure. # 2000 European Association for Cranio-Maxillofacial Surgery INTRODUCTION In Europe, cancer of the oral cavity is responsible for 2% of all types of carcinoma (Boyle et al., 1993; Hindle et al., 1994). Nearly 90% of all oral carcinomas are of squamous cell type (SCC). SCC in the region of the lower jaw, i.e. the mandibular alveolar ridge, lower buccal sulcus, sublingual sulcus and retromolar trigone usually carry a poor prog- nosis. The incidence of mandibular invasion by SCC depends on the size of the primary tumour and on the proximity of the tumour to the mandible (Hoppe & Donath, 1987; Slootweg & Mueller, 1989; Mueller & Slootweg, 1990; Tsue et al., 1994). If tumour encroaches onto the mandible or is clinically fixed to the mandible, three options have to be considered. The mandible can either be free of tumour, there may be minimal cortical erosion or gross invasion of cancellous bone. To assess the extent of tumour invasion of bone and to help indicate whether a segmental or marginal resection of the mandible should be carried out, clinical assessment by inspection and bimanual palpation and several imaging techniques are used. Although the sensitivity of clinical assessment of mandibular invasion is not high (Gilbert et al., 1986; Shaha, 1991; Weisman et al., 1982), clinical examina- tion is important in assessing the tumour invasion around the mandible. An accuracy of 82% is reported for panoramic radiographs (Ord et al., 1997) but this technique has a low sensitivity in detecting cortical erosion (Gilbert et al., 1986; Shaha, 1991). Accuracy of computed tomography (CT) is de- scribed as being between 68% and 80% (Shaha, 1991; Bahadur, 1990). Despite many artifacts resulting from dental fillings and irregularities of dental sockets, CT scan is superior to other techniques in detecting minimal cortical bone involvement and early invasion (Castelijns & van den Brekel, 1993; Tsue et al., 1994; van den Brekel et al., 1994). The value of MRI for the detection of tumour invasion into the mandible is controversial. Despite its high accuracy in soft tissue and the possibility of detecting perineural invasion without technical 325 Journal of Cranio-Maxillofacial Surgery (2000) 28, 325–330 # 2000 European Association for Cranio-Maxillofacial Surgery doi:10.1054/jcms.2000.0171, available online at http://www.idealibrary.com on