title: Postacquisition detection of tumor motion in the lung and upper abdomen using list-mode PET data: a feasibility study.
abstract: One of the main degrading factors in the quality of oncologic PET images of the thorax and upper abdomen is respiratory motion of tumors. One method to reduce this effect is the acquisition of PET data in gated mode. A second method is the correction of studies for motion. Motion registration is essential in both cases. We report a method using list-mode data to detect the craniocaudal (z) movement of thoracic and abdominal lesions without using any external gating device. The aim of this study was to show the feasibility of applying this method to patient data.
  
  
  METHODS
  For 10 patients with lesions in the lung or upper abdominal organs, images for short time bins of 250, 500, and 750 ms were reconstructed. A volume of interest, which was manually defined in a summed image around the structure of interest, was projected to each time bin. The center of mass of the activity distribution in this volume of interest was determined for each case. The curves of the z-coordinate of the center of mass (z(COM)) over the time were analyzed and compared with respiration curves obtained by a pressure-sensitive belt.
  
  
  RESULTS
  In 7 of the 10 patients, movement of the lesion was registered in good accordance with the pressure belt. In the 3 remaining patients, no changes in the center of mass due to respiration could be detected, most likely because of minimal respiratory motion. The maximal difference in z(COM) for a lesion that was detected within the 10-min acquisition was 18.5 mm. For 7 of the 10 patients, the mean value for each respiration amplitude was between 11.0 and 2.0 mm.
  
  
  CONCLUSIONS
  We have shown the feasibility of registering movement of high-uptake lesions without the use of any external device that may restrain the patient. Furthermore, unlike external sensors, this method quantifies internal motion and, thus, is a promising base for correction methods.
authors.affiliation: Nuklearmedizinische Klinik und Poliklinik, Klinikum rechts der Isar der Technischen Universität München, Munich, Germany. ralph.bundschuh@ph.tum.de
authors.forename: Ralph A
authors.initials: RA
authors.lastname: Bundschuh
authors.forename: Axel
authors.initials: A
authors.lastname: Martínez-Moeller
authors.forename: Markus
authors.initials: M
authors.lastname: Essler
authors.forename: María-José
authors.initials: MJ
authors.lastname: Martínez
authors.forename: Stephan G
authors.initials: SG
authors.lastname: Nekolla
authors.forename: Sibylle I
authors.initials: SI
authors.lastname: Ziegler
authors.forename: Markus
authors.initials: M
authors.lastname: Schwaiger
mesh_terms: D000008:Abdominal Neoplasms / Q000000981:diagnostic imaging*; D000465:Algorithms; D016477:Artifacts; D005240:Feasibility Studies; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D009068:Movement; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18