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The effect of photon energy on intensity-modulated radiation therapy (IMRT) plans for prostate cancer.

Sung W, Park JM, Choi CH, Ha SW, Ye SJ - Radiat Oncol J (2012)

Bottom Line: However, there was a significant dose increase in rectal wall and femoral heads for 6-MV compared to those for 10-MV and 15-MV.Integral doses to the normal tissues in higher energy (10-MV and 15-MV) plans were reduced by about 7%.The biological and clinical significance of this finding remains to be determined afterward, considering neutron dose contribution.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Korea. ; Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.

ABSTRACT

Purpose: To evaluate the effect of common three photon energies (6-MV, 10-MV, and 15-MV) on intensity-modulated radiation therapy (IMRT) plans to treat prostate cancer patients.

Materials and methods: Twenty patients with prostate cancer treated locally to 81.0 Gy were retrospectively studied. 6-MV, 10-MV, and 15-MV IMRT plans for each patient were generated using suitable planning objectives, dose constraints, and 8-field setting. The plans were analyzed in terms of dose-volume histogram for the target coverage, dose conformity, organs at risk (OAR) sparing, and normal tissue integral dose.

Results: Regardless of the energies chosen at the plans, the target coverage, conformity, and homogeneity of the plans were similar. However, there was a significant dose increase in rectal wall and femoral heads for 6-MV compared to those for 10-MV and 15-MV. The V(20 Gy) of rectal wall with 6-MV, 10-MV, and 15-MV were 95.6%, 88.4%, and 89.4% while the mean dose to femoral heads were 31.7, 25.9, and 26.3 Gy, respectively. Integral doses to the normal tissues in higher energy (10-MV and 15-MV) plans were reduced by about 7%. Overall, integral doses in mid and low dose regions in 6-MV plans were increased by up to 13%.

Conclusion: In this study, 10-MV prostate IMRT plans showed better OAR sparing and less integral doses than the 6-MV. The biological and clinical significance of this finding remains to be determined afterward, considering neutron dose contribution.

No MeSH data available.


Related in: MedlinePlus

Dose volume histograms (DVHs) for the primary and boost planning target volumes (PTVs) from sum plans are shown. The solid lines indicate DVHs of intensity-modulated radiation therapy with 6-MV photon beams. Between two solid lines of DVHs, one which receives higher dose is DVH for the boost PTV and the other is DVH for the primary PTV. Dashed lines and dotted lines indicate DVHs from 10-MV and 15-MV, respectively. No clear differences are observed among three types of plans.
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Figure 1: Dose volume histograms (DVHs) for the primary and boost planning target volumes (PTVs) from sum plans are shown. The solid lines indicate DVHs of intensity-modulated radiation therapy with 6-MV photon beams. Between two solid lines of DVHs, one which receives higher dose is DVH for the boost PTV and the other is DVH for the primary PTV. Dashed lines and dotted lines indicate DVHs from 10-MV and 15-MV, respectively. No clear differences are observed among three types of plans.

Mentions: A quantitative analysis was carried out to compare DVH, homogeneity index and the target coverage parameter such as Dmax and Dmean (Table 3, Fig. 1). Homogeneity indices were similar in primary plans (1.05, 1.05, and 1.06 for HI of 6-MV, 10-MV, and 15-MV, respectively). The boost plans of 6-MV beams showed a slightly better target dose homogeneity than both 10-MV and 15-MV beams, but the HI value were similar in the three groups (1.04, 1.05, and 1.06 for HI of 6-MV, 10-MV, and 15-MV, respectively). No clear differences of maximal and mean dose to target were observed among 6-MV, 10-MV, and 15-MV plans. The mean doses to PTVB in higher energy tend to be more or less higher but it is negligible (29.83, 30.01, and 30.14 for Dmean of 6-MV, 10-MV, and 15-MV, respectively). The mean doses to PTVp and PTVB in 6-MV sum plans were slightly lower than the others but the differences were not large.


The effect of photon energy on intensity-modulated radiation therapy (IMRT) plans for prostate cancer.

Sung W, Park JM, Choi CH, Ha SW, Ye SJ - Radiat Oncol J (2012)

Dose volume histograms (DVHs) for the primary and boost planning target volumes (PTVs) from sum plans are shown. The solid lines indicate DVHs of intensity-modulated radiation therapy with 6-MV photon beams. Between two solid lines of DVHs, one which receives higher dose is DVH for the boost PTV and the other is DVH for the primary PTV. Dashed lines and dotted lines indicate DVHs from 10-MV and 15-MV, respectively. No clear differences are observed among three types of plans.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3475960&req=5

Figure 1: Dose volume histograms (DVHs) for the primary and boost planning target volumes (PTVs) from sum plans are shown. The solid lines indicate DVHs of intensity-modulated radiation therapy with 6-MV photon beams. Between two solid lines of DVHs, one which receives higher dose is DVH for the boost PTV and the other is DVH for the primary PTV. Dashed lines and dotted lines indicate DVHs from 10-MV and 15-MV, respectively. No clear differences are observed among three types of plans.
Mentions: A quantitative analysis was carried out to compare DVH, homogeneity index and the target coverage parameter such as Dmax and Dmean (Table 3, Fig. 1). Homogeneity indices were similar in primary plans (1.05, 1.05, and 1.06 for HI of 6-MV, 10-MV, and 15-MV, respectively). The boost plans of 6-MV beams showed a slightly better target dose homogeneity than both 10-MV and 15-MV beams, but the HI value were similar in the three groups (1.04, 1.05, and 1.06 for HI of 6-MV, 10-MV, and 15-MV, respectively). No clear differences of maximal and mean dose to target were observed among 6-MV, 10-MV, and 15-MV plans. The mean doses to PTVB in higher energy tend to be more or less higher but it is negligible (29.83, 30.01, and 30.14 for Dmean of 6-MV, 10-MV, and 15-MV, respectively). The mean doses to PTVp and PTVB in 6-MV sum plans were slightly lower than the others but the differences were not large.

Bottom Line: However, there was a significant dose increase in rectal wall and femoral heads for 6-MV compared to those for 10-MV and 15-MV.Integral doses to the normal tissues in higher energy (10-MV and 15-MV) plans were reduced by about 7%.The biological and clinical significance of this finding remains to be determined afterward, considering neutron dose contribution.

View Article: PubMed Central - PubMed

Affiliation: Interdisciplinary Program in Radiation Applied Life Science, Seoul National University College of Medicine, Seoul, Korea. ; Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea.

ABSTRACT

Purpose: To evaluate the effect of common three photon energies (6-MV, 10-MV, and 15-MV) on intensity-modulated radiation therapy (IMRT) plans to treat prostate cancer patients.

Materials and methods: Twenty patients with prostate cancer treated locally to 81.0 Gy were retrospectively studied. 6-MV, 10-MV, and 15-MV IMRT plans for each patient were generated using suitable planning objectives, dose constraints, and 8-field setting. The plans were analyzed in terms of dose-volume histogram for the target coverage, dose conformity, organs at risk (OAR) sparing, and normal tissue integral dose.

Results: Regardless of the energies chosen at the plans, the target coverage, conformity, and homogeneity of the plans were similar. However, there was a significant dose increase in rectal wall and femoral heads for 6-MV compared to those for 10-MV and 15-MV. The V(20 Gy) of rectal wall with 6-MV, 10-MV, and 15-MV were 95.6%, 88.4%, and 89.4% while the mean dose to femoral heads were 31.7, 25.9, and 26.3 Gy, respectively. Integral doses to the normal tissues in higher energy (10-MV and 15-MV) plans were reduced by about 7%. Overall, integral doses in mid and low dose regions in 6-MV plans were increased by up to 13%.

Conclusion: In this study, 10-MV prostate IMRT plans showed better OAR sparing and less integral doses than the 6-MV. The biological and clinical significance of this finding remains to be determined afterward, considering neutron dose contribution.

No MeSH data available.


Related in: MedlinePlus