Static and moving phantom studies for radiation treatment planning in a positron emission tomography and computed tomography (PET/CT) system
- 159 Downloads
To determine an appropriate threshold value for delineation of the target in positron emission tomography (PET) and to investigate whether PET can delineate an internal target volume (ITV), a series of phantom studies were performed.
An ellipse phantom (background) was filled with 1028 Bq/ml of [18F] fluoro-2-deoxyglucose (18FDG), and six spheres of 10 mm, 13 mm, 17 mm, 22 mm, 28 mm, and 37 mm in diameter inside it were filled with 18FDG activity to achieve source-to-background (S/B) ratios of 10, 15, and 20. In static phantom experiments, an appropriate threshold value was determined so that the size of PET delineation fits to an actual sphere. In moving phantom experiments with total translations of 10 mm, 20 mm, and 30 mm and a period of oscillation of 4 s, the maximum size of PET delineation with the appropriate threshold value was measured in both the axial and sagittal planes.
In the static phantom experiments, the measured maximum 18FDG activities of spheres of less than 22 mm were lower than 80% of the injected 18FDG activity, and those for the larger spheres ranged from 90% to 110%. Appropriate threshold values determined for the spheres of 22 mm or more ranged from 30% to 40% of the maximum 18FDG activity, independent of the S/B ratio. Therefore, we adopted an appropriate threshold value as 35% of the measured maximum 18FDG activity. In moving phantom experiments, the maximum 18FDG activity of spheres decreased significantly, dependent on the movement distance. Although the sizes of PET delineation with 35% threshold value tended to be slightly smaller (<3 mm) than the actual spheres in the axial plane, the longest sizes in the sagittal plane were larger than the actual spheres.
When a threshold value of 35% of the measured maximum 18FDG activity was adopted, the sizes of PET delineation were almost the same for static and moving phantom spheres of 22 mm or more in the axial plane. In addition, PET images have the potential to provide an individualized ITV.
KeywordsPhantom experiments Appropriate threshold values Positron emission tomography (PET) Radiation treatment planning Internal target volume (ITV)
Unable to display preview. Download preview PDF.
- 1.Mac Manus MP, Wong K, Hicks RJ, Matthews JP, Wirth A, Ball DL. Early mortality after radical radiotherapy for non-small-cell lung cancer: comparison of PET-staged and conventionally staged cohorts treated at a large tertiary referral center. Int J Radiat Oncol Biol Phys 2002;52:351–361.PubMedGoogle Scholar
- 9.Antoch G, Saoudi N, Kuehl H, Dahmen G, Mueller SP, Beyer T, et al. Accuracy of whole-body dual-modality fluorine-18-2-fluoro-2-deoxy-d-glucose positron emission tomography and computed tomography (FDG-PET/CT) for tumor staging in solid tumors: comparison with CT and PET. J Clin Oncol 2004;22:4357–4368.PubMedCrossRefGoogle Scholar
- 11.Faria SL, Menard S, Devic S, Sirois C, Souhami L, Lisbona R, et al. Impact of FDG-PET on radiation therapy volume delineation in non-small-cell lung cancer. Int J Radiat Oncol Biol Phys 2004;59:78–86.Google Scholar
- 13.van Der Wel A, Nijsten S, Hochstenbag M, Lamers R, Boersma L, Wanders R, et al. Increased therapeutic ratio by 18FDG-PET CT planning in patients with clinical CT stage N2-N3M0 non-small-cell lung cancer: a modeling study. Int J Radiat Oncol Biol Phys 2005;61:649–655.Google Scholar
- 20.Mah K, Caldwell CB, Ung YC, Danjoux CE, Balogh JM, Ganguli SN, et al. The impact of 18 FDG-PET on target and critical organs in CT-based treatment planning of patients with poorly defined non-small-cell lung carcinoma: a prospective study. Int J Radiat Oncol Biol Phys 2002;52:339–350.PubMedGoogle Scholar
- 24.Deniaud-Alexandre E, Touboul E, Lerouge D, Grahek D, Foulquier JN, Petegnief Y, et al. Impact of computed tomography and 18F-deoxyglucose coincidence detection emission tomography image fusion for optimization of conformal radiotherapy in non-small-cell lung cancer. Int J Radiat Oncol Biol Phys 2005;63:1432–1441.PubMedCrossRefGoogle Scholar
- 26.Nestle U, Kremp S, Schaefer-Schuler A, Sebastian-Welsch C, Hellwig D, Rübe C, et al. Comparison of different methods for delineation of 18FDG-PET-positive tissue for target volume definition in radiotherapy of patients with non-small cell lung cancer. J Nucl Med 2005;46:1342–1348.PubMedGoogle Scholar
- 37.Sarrut D, Boldea V, Miguet S, Ginestet C. Simulation of 4D CT Images from deformable registration between inhale and exhale breath-hold CT scans. Int J Radiat Oncol Biol Phys 2005;63:S509–S510.Google Scholar
- 39.Britton KR, Starkschall G, Tucker SL, Pan T, Nelson C, Chang JY, et al. Assessment of gross tumor volume regression and motion changes during radiotherapy for non-small-cell lung cancer as measured by four-dimensional computed tomography. Int J Radiat Oncol Biol Phys 2007;68:1036–1046.PubMedGoogle Scholar