A Comparison of Amplitude-Based and Phase-Based Positron Emission Tomography Gating Algorithms for Segmentation of Internal Target Volumes of Tumors Subject to Respiratory Motion

• Published in: International journal of radiation oncology, biology, physics Vol. 87; no. 3; pp. 562 - 569
• Main Authors: Jani, Shyam S., Robinson, Clifford G., Dahlbom, Magnus, White, Benjamin M., Thomas, David H., Gaudio, Sergio, Low, Daniel A., Lamb, James M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2013
• Subjects: ACCURACY; Algorithms; AMPLITUDES; Analysis of Variance; FLUORODEOXYGLUCOSE; Fluorodeoxyglucose F18 - pharmacokinetics; Hematology, Oncology and Palliative Medicine; Lung Neoplasms - diagnostic imaging; Lung Neoplasms - metabolism; Lung Neoplasms - pathology; Lymph Nodes - diagnostic imaging; Lymph Nodes - metabolism; Lymph Nodes - pathology; Mediastinum; Movement; Multimodal Imaging - instrumentation; Multimodal Imaging - methods; NEOPLASMS; PATIENTS; PHANTOMS; Phantoms, Imaging; POSITRON COMPUTED TOMOGRAPHY; Positron-Emission Tomography - methods; Radiology; RADIOLOGY AND NUCLEAR MEDICINE; Radiopharmaceuticals - pharmacokinetics; RESPIRATION; Statistics, Nonparametric; Tomography, X-Ray Computed; Tumor Burden
• ISSN: 0360-3016; 1879-355X; 1879-355X
• DOI: 10.1016/j.ijrobp.2013.06.2042

To quantitatively compare the accuracy of tumor volume segmentation in amplitude-based and phase-based respiratory gating algorithms in respiratory-correlated positron emission tomography (PET). List-mode fluorodeoxyglucose-PET data was acquired for 10 patients with a total of 12 fluorodeoxyglucose-avid tumors and 9 lymph nodes. Additionally, a phantom experiment was performed in which 4 plastic butyrate spheres with inner diameters ranging from 1 to 4 cm were imaged as they underwent 1-dimensional motion based on 2 measured patient breathing trajectories. PET list-mode data were gated into 8 bins using 2 amplitude-based (equal amplitude bins [A1] and equal counts per bin [A2]) and 2 temporal phase-based gating algorithms. Gated images were segmented using a commercially available gradient-based technique and a fixed 40% threshold of maximum uptake. Internal target volumes (ITVs) were generated by taking the union of all 8 contours per gated image. Segmented phantom ITVs were compared with their respective ground-truth ITVs, defined as the volume subtended by the tumor model positions covering 99% of breathing amplitude. Superior-inferior distances between sphere centroids in the end-inhale and end-exhale phases were also calculated. Tumor ITVs from amplitude-based methods were significantly larger than those from temporal-based techniques (P=.002). For lymph nodes, A2 resulted in ITVs that were significantly larger than either of the temporal-based techniques (P<.0323). A1 produced the largest and most accurate ITVs for spheres with diameters of ≥2 cm (P=.002). No significant difference was shown between algorithms in the 1-cm sphere data set. For phantom spheres, amplitude-based methods recovered an average of 9.5% more motion displacement than temporal-based methods under regular breathing conditions and an average of 45.7% more in the presence of baseline drift (P<.001). Target volumes in images generated from amplitude-based gating are larger and more accurate, at levels that are potentially clinically significant, compared with those from temporal phase-based gating.