Gamma camera-based PET inverse treatment planning for head and neck cancer using hybrid imaging instrumentation and IMRT

Abstract Purpose : To demonstrate the feasibility of incorporating gamma camera-based positron emission tomography (GC-PET) nuclear medicine molecular imaging into inverse conformal radiotherapy treatment planning using commercially available hardware and software. Materials and methods : Anatomical X-ray computed tomography (X-ray CT) and GC-PET imaging of the base of the tongue region were performed on a hybrid nuclear medicine—X-ray CT scanner (General Electric Millennium VG Hawkeye, Milwaukee, WI). Patient positioning included a carbon composite flat-table insert and Aquaplast™ U-frame head immobilization mask. Both anatomical and molecular images were acquired and then transferred to the treatment planning and dose calculation workstations via a Local Area Network (LAN). GC-PET molecular information was registered with the anatomy using a four-point external registration technique. A five-field conformal inverse treatment plan, which targets radiation dose to the GC-PET-defined lesion, was then developed using the Varian SomaVision™, CadPlan™ and Helios™ treatment planning modules. Results : The radiation dose distribution was made to conform to the tumor region, as indicated by the area of increased flouro-2-deoxyglucose (FDG) uptake in the GC-PET image, using the inverse treatment planning technique. Conclusions : Information from molecular imaging techniques such as GC-PET may be incorporated into the inverse treatment planning process using the combined molecular and anatomical imaging methods, and commercially available hardware and software.