Validation and Clinical Application of Computer*combined Computed Tomography and Positron Emission Tomography with 2 # [ 1 SF] Fluoro*2 +Deoxy#D#Glucose Head and Neck Images Wai-Lup Wong, MRCP, FRCR, Karim Hussain, MB, BS, FRCS, Elfy Chevretton, MS, FRCS, David J. Hawkes, PhD, Hiram Baddeley, FRACR, FRCR, Michael Maisey, FRCP, FRCR, Mark McGurk, MD, FRCS, London, United Kingdom BACKGROUND: Positron emission tomography with 2-[18F]fluoro-2-deoxy-o-glucose (PET-FDG) improves the detection of head and neck squa- mous cell cancer (HNSCC), but lacks anatomical detail. The accuracy of registered computed to- mography/magnetic resonance (CT/MR) and PET-FDG in delineation of HNSCC at the primary site and its clinical application was investigated. METHOD: Preoperatively 30 patients were staged clinically and each had either CT (23), MR (5), or both CT and MR (2) scans, as well as CT/MR- PET-FDG registration. Tumor margins or infiltra- tion of specific anatomical landmarks on the dif- ferent scans were compared and judged against histology. RESULTS: For primary tumors CT-PET-FDG (97%) and MR-PET-FDG (100%) delineated the tumor more accurately than CT (69%) or MR (40%) alone. Similarly, CT-PET-FDG (98%) and MR-PET- FDG (100%) were better than CT (70%) and MR alone (80%) in identifying tumor invasion of spe- cific anatomical structures. Management was al- tered in 7 of 30 patients. The registered images were particularly useful in delineating tumor ex- tension in the infratemporal fossa, maxilla and mandible, and identifying recurrences obscured by scar tissue. CONCLUSIONS: It is possible to accurately register CT, MR, and PET-FDG data sets in the head and neck. The initial results show that registered CT/ MR-PET-FDG images provide additional clinically relevant information over that obtained from clini- From the Department of Oral and Maxillo-Facial Surgery (KH, MMcG) and Division of Radiological Sciences (DJH, MM), United Medical and Dental Schools; Clinical PET Centre (W-LW) and ENT Department (EC), Guy’s and St Thomas’ Hospitals; and Paul Strickland Scanner Centre (HB), Mount Vernon Hospital, London, United Kingdom. Requests for reprints should be addressed to Mark McGurk, MD, UMDS Department of Maxillo-facial Surgery, Guys Hospital, London SE1 9RT, United Kingdom. Presented at the Fourth International Conference of the Society 3f Head and Neck Surgeons, Toronto, Ontario, Canada, July 28- August 1, 1996. cal evaluation or conventional CT/MR imag- ing. 01996 by Excerpta Medica, Inc. Am J Surg. 1996;172:626-632. P resent cross-sectional imaging techniques such as computed tomography (CT), magnetic resonance (MR), and ultrasound provide unparalleled morpho- logical detail. However, none of these imaging modalities at present can reliably and consistently distinguish tumor from reactive changes, or the sequelae of treatment.‘-’ As a consequence, in some cases it is impossible to precisely delineate extent of local disease. Positron emission tomography (PET) is a new imaging technique that relies on the use of radionuclides, which decay with emission of positively charged particles (posi- trons). These positrons travel short distances in tissue be- fore combining with a negatively charged electron, thus converting mass into energy. When the masses annihilate, two photons (gamma rays) are produced, which are emitted at approximately 180” from each other. The simultaneous detection of two such photons by opposing detectors is then used to reconstruct a three-dimensional representation of these events. Depending on the radionuclide used, different aspects of tissue metabolism and organ function can be mea- sured, such as distribution of blood flow, oxygen utilization, protein synthesis, and glucose consumption. Cancer cells avidly take up glucose, a fact known to biochemists for many years.4 2- [ 18F]fluoro-2-deoxy-n-glucose (FDG), a ra- dionuclide-labeled analogue of glucose, has been shown to be useful in identifying squamous cell carcinoma of the up- per aero-digestive tract. It has the potential to improve de- tection of both primary and recurrent disease at the primary site in patients with head and neck cancer compared with conventional sectional imaging.‘~~” However, PET-FDG im- ages lack anatomical detail, limiting their use in treatment planning. Registration and fusion of CT/MR with PET- FDG data-sets may resolve this problem. The aims of this study were to investigate the accuracy of computer-combined CT/MR and PET-FDG imaging in the delineation of head and neck squamous cell carcinoma at the primary site and to evaluate its clinical application. PATIENTS AND METHODS In the head and neck services of Guy’s and St. Thomas’ Hospitals, 30 patients ( 16 men, 14 women) with squamous J 628 0 1996 by Excerpta Medica, Inc. 0002-961 O/96/$1 5.00 All rights reserved. PII SOOO2-9610(96)00313-3