ABSTRACT
PURPOSE: Cross-modality coregistration of positron emission tomography (PET) and magnetic resonance imaging (MR) could enhance the clinical information. In this study we propose a refined technique to improve the robustness of registration, and to implement more realistic visualization of the coregistered images. MATERIALS AND METHODS: Using the sinogram of PET emission scan, we extracted the robust head boundary and used boundary-enhanced PET to coregister PET with MR. The pixels having 10% of maximum pixel value were considered as the boundary of sinogram. Boundary pixel values were exchanged with maximum value of sinogram. One hundred eighty boundary points were extracted at intervals of about 2 degree using simple threshold method from each slice of MR images. Best affined transformation between the two point sets was performed using least square fitting which should minimize the sum of Euclidean distance between the point sets. We reduced calculation time using pre-defined distance map. Finally we developed an automatic coregistration program using this boundary detection and surface matching technique. We designed a new weighted normalization technique to display the coregistered PET and MR images simultaneously. RESULTS: Using our newly developed method, robust extraction of head boundary was possible and spatial regishation was successfully performed. Mean displacement error was less than 2.0mm. In visualization of coregistered images using weighted normalization method, structures shown in MR image could be realistically represented. CONCLUSION: Our refined technique could practically enhance the performance of automated three dimensional coregistration.
Subject(s)
Brain , Head , Magnetic Resonance Imaging , Positron-Emission TomographyABSTRACT
he purpose of this study was to evaluate the usefulness of whole body F-18 FDG PET scan for deceting postoperative recurrence of cancer. One hundred four cancer patients after operation were enrolled(l4 brain tumor, 15 head and neck cancer, 23 gynecologic cancer). Besides conventional images(CI) including CT and MRI, F-18 FDG PET scan was obtained on ECAT EXACT 47 scanner(Siemens-CTI), beginning 60 minutes after injection of 370MBq(10mCi) of F-18 FDG. Regional scan was also obtained with emission image. Transmission images using Ge-68 were carried out for attenuation correction in both whole body and regional images. Findings of PET and CI were confirmed by pathology or clinical follow up. The sensitivity and specificity of PET for detecting recurrence were 94% and 92%, respectively. Contrarily, the sensitivity and specific it of CI were 78% and 68% CI results were negative and PET results were positive in 11 cases. The biopsy or clinical follow-up of those cases confirmed recurrence of tumor. False negative cases of CI were frequent in patients with gynecologic cancers. Also we measured the Serum concentration of tumor markers in patients with gynecologic cancer(CA125), thyroid cancer(thyroglobulin), and colorectal cancer(CEA). The sensitivity and specificity of tumor markers were 71% and 84%, respectively. We conclude that F-18 FDG PET can be used valuably in detecting recurrent foci of a wide variety of malignancy compared to conventional diagnositic methods.