SU‐E‐J‐169: 4D‐PET for Abdominal Tumor Target Volume Generation

• Published in: Medical Physics 2012-06, Vol.39 (6), p.3691-3691
• Main Authors: Lamb, J, Lee, P, Jani, S, Dahlbom, M, White, B, Low, D
• Format: Article
• Language: English
• Subjects: Cancer; Computed tomography; Image analysis; Image motion analysis; Medical imaging; Positron emission tomography; Tissues
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.4735008

Purpose: To examine the impact of 4D‐PET on target volume delineation of upper‐abdominal tumors, versus conventional un‐gated PET. Methods: Four patients with upper‐abdominal tumors underwent respiratory‐correlated FDG PET/CT scanning (4D‐PET) as part of a continuing IRB‐approved research protocol. Internal target volumes of FDG‐avid tumors were contoured on the 4D‐PET and conventional un‐gated PET by a radiation oncologist who is a specialist in gastro‐intestinal tumors. To create the 4D‐PET ITV, the end‐inhale and end‐exhale 4D‐PET phases were used. The relative volumes and volumetric overlaps of the 4D and un‐gated target volumes were examined. Additionally, 4D‐PET was used to measure the motion of the tumors. Results: Of the four patients who were imaged, one showed minimal motion (〈 3 mm in any direction) and one showed minimal FDG avidity; these were removed from further analysis. Of the two tumors which showed significant motion and FDG uptake, 4D‐PET volumes were 28% and 21% larger than un‐gated PET volumes. The un‐gated PET volumes were almost entirely contained within the 4D‐PET volumes (95% and 93% for the two tumors). Tumors appeared to deform as well as translate with breathing, although this could be due to varying intra‐gate motion rather than actual physiological deformation. The superior‐inferior borders of the tumors exhibited the most motion, with displacements of 5.6 mm and 6.4 mm. Conclusions: 4D‐PET can be used to estimate the motion of FDG‐avid upper‐abdominal tumors. Use of 4D‐PET increases the size of target volumes compared to un‐gated PET in a subset of upper‐abdominal cancer patients. Direct measurement of tumor motion and deformation by 4D‐PET imaging could allow the use of patient‐specific margins rather than population‐based margins, potentially leading to increased target coverage and reduced normal tissue irradiation.