Limits...
Carbon-ion scanning lung treatment planning with respiratory-gated phase-controlled rescanning: simulation study using 4-dimensional CT data.

Takahashi W, Mori S, Nakajima M, Yamamoto N, Inaniwa T, Furukawa T, Shirai T, Noda K, Nakagawa K, Kamada T - Radiat Oncol (2014)

Bottom Line: The dose assessment metrics were quantified by changing the number of PCR and the results for the ungated and gated scenarios were then compared.Applying respiratory gating, percentage of lung receiving at least 20 Gy(RBE) (lung-V20) and heart maximal dose, averaged over all patients, significantly decreased by 12% (p < 0.05) and 13% (p < 0.05), respectively.The use of a respiratory-gated strategy in combination with PCR reduced excessive doses to OARs.

View Article: PubMed Central - PubMed

Affiliation: Research Center Hospital for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba-shi, Chiba, 263-8555, Japan. wataru.harry1@gmail.com.

ABSTRACT

Background: To moving lung tumors, we applied a respiratory-gated strategy to carbon-ion pencil beam scanning with multiple phase-controlled rescanning (PCR). In this simulation study, we quantitatively evaluated dose distributions based on 4-dimensional CT (4DCT) treatment planning.

Methods: Volumetric 4DCTs were acquired for 14 patients with lung tumors. Gross tumor volume, clinical target volume (CTV) and organs at risk (OARs) were delineated. Field-specific target volumes (FTVs) were calculated, and 48Gy(RBE) in a single fraction was prescribed to the FTVs delivered from four beam angles. The dose assessment metrics were quantified by changing the number of PCR and the results for the ungated and gated scenarios were then compared.

Results: For the ungated strategy, the mean dose delivered to 95% of the volume of the CTV (CTV-D95) was in average 45.3 ± 0.9 Gy(RBE) even with a single rescanning (1 × PCR). Using 4 × PCR or more achieved adequate target coverage (CTV-D95 = 46.6 ± 0.3 Gy(RBE) for ungated 4 × PCR) and excellent dose homogeneity (homogeneity index =1.0 ± 0.2% for ungated 4 × PCR). Applying respiratory gating, percentage of lung receiving at least 20 Gy(RBE) (lung-V20) and heart maximal dose, averaged over all patients, significantly decreased by 12% (p < 0.05) and 13% (p < 0.05), respectively.

Conclusions: Four or more PCR during PBS-CIRT improved dose conformation to moving lung tumors without gating. The use of a respiratory-gated strategy in combination with PCR reduced excessive doses to OARs.

No MeSH data available.


Related in: MedlinePlus

Carbon-ion dose distributions with a single beam angle for (a) ungated and (b) gated irradiation. Planning dose distribution and treatment dose simulations with 1 × PCR, 4 × PCR, and 8 × PCR. In the supine position, the beam angle was set to 340 degrees. The respiratory cycle was 4.2 sec. Yellow lines demonstrate the CTV (patient no. 7). Green arrows show beam direction. In Figure 1(a), white arrow shows the dose degradation in the CTV. Dose assessment metrics for all 14 cases as a function of the number of rescannings. Beam angle was 340 degrees. D95, Dmax, and Dmin for (c) ungated and (d) gated strategies. The homogeneity index (HI) is for (e) ungated and (f) gated strategies.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4230758&req=5

Fig1: Carbon-ion dose distributions with a single beam angle for (a) ungated and (b) gated irradiation. Planning dose distribution and treatment dose simulations with 1 × PCR, 4 × PCR, and 8 × PCR. In the supine position, the beam angle was set to 340 degrees. The respiratory cycle was 4.2 sec. Yellow lines demonstrate the CTV (patient no. 7). Green arrows show beam direction. In Figure 1(a), white arrow shows the dose degradation in the CTV. Dose assessment metrics for all 14 cases as a function of the number of rescannings. Beam angle was 340 degrees. D95, Dmax, and Dmin for (c) ungated and (d) gated strategies. The homogeneity index (HI) is for (e) ungated and (f) gated strategies.

Mentions: The upper panels in Figure 1 give the accumulated dose distributions with a single beam angle when the number of rescannings was varied without respiratory gating (Figure 1a). The treatment dose differed from the planning dose distribution due to intrafractional motion. Target dose conformation improved with an increasing number of PCR. In a typical case, patient no. 7, for example, D95 values were 44.4 Gy(RBE), 46.7 Gy(RBE), and 46.7 Gy(RBE) with 1×, 4× and 8 × PCR, respectively. Furthermore, as shown in the lower panels of Figure 1b, the gating strategy achieved good dose conformation to the target even when the number of PCR was small; D95 with 1 × PCR in the gated plan (45.7 Gy(RBE)), for example, was better than that in the ungated plan (44.4 Gy(RBE)).Figure 1


Carbon-ion scanning lung treatment planning with respiratory-gated phase-controlled rescanning: simulation study using 4-dimensional CT data.

Takahashi W, Mori S, Nakajima M, Yamamoto N, Inaniwa T, Furukawa T, Shirai T, Noda K, Nakagawa K, Kamada T - Radiat Oncol (2014)

Carbon-ion dose distributions with a single beam angle for (a) ungated and (b) gated irradiation. Planning dose distribution and treatment dose simulations with 1 × PCR, 4 × PCR, and 8 × PCR. In the supine position, the beam angle was set to 340 degrees. The respiratory cycle was 4.2 sec. Yellow lines demonstrate the CTV (patient no. 7). Green arrows show beam direction. In Figure 1(a), white arrow shows the dose degradation in the CTV. Dose assessment metrics for all 14 cases as a function of the number of rescannings. Beam angle was 340 degrees. D95, Dmax, and Dmin for (c) ungated and (d) gated strategies. The homogeneity index (HI) is for (e) ungated and (f) gated strategies.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4230758&req=5

Fig1: Carbon-ion dose distributions with a single beam angle for (a) ungated and (b) gated irradiation. Planning dose distribution and treatment dose simulations with 1 × PCR, 4 × PCR, and 8 × PCR. In the supine position, the beam angle was set to 340 degrees. The respiratory cycle was 4.2 sec. Yellow lines demonstrate the CTV (patient no. 7). Green arrows show beam direction. In Figure 1(a), white arrow shows the dose degradation in the CTV. Dose assessment metrics for all 14 cases as a function of the number of rescannings. Beam angle was 340 degrees. D95, Dmax, and Dmin for (c) ungated and (d) gated strategies. The homogeneity index (HI) is for (e) ungated and (f) gated strategies.
Mentions: The upper panels in Figure 1 give the accumulated dose distributions with a single beam angle when the number of rescannings was varied without respiratory gating (Figure 1a). The treatment dose differed from the planning dose distribution due to intrafractional motion. Target dose conformation improved with an increasing number of PCR. In a typical case, patient no. 7, for example, D95 values were 44.4 Gy(RBE), 46.7 Gy(RBE), and 46.7 Gy(RBE) with 1×, 4× and 8 × PCR, respectively. Furthermore, as shown in the lower panels of Figure 1b, the gating strategy achieved good dose conformation to the target even when the number of PCR was small; D95 with 1 × PCR in the gated plan (45.7 Gy(RBE)), for example, was better than that in the ungated plan (44.4 Gy(RBE)).Figure 1

Bottom Line: The dose assessment metrics were quantified by changing the number of PCR and the results for the ungated and gated scenarios were then compared.Applying respiratory gating, percentage of lung receiving at least 20 Gy(RBE) (lung-V20) and heart maximal dose, averaged over all patients, significantly decreased by 12% (p < 0.05) and 13% (p < 0.05), respectively.The use of a respiratory-gated strategy in combination with PCR reduced excessive doses to OARs.

View Article: PubMed Central - PubMed

Affiliation: Research Center Hospital for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1, Anagawa, Inage-ku, Chiba-shi, Chiba, 263-8555, Japan. wataru.harry1@gmail.com.

ABSTRACT

Background: To moving lung tumors, we applied a respiratory-gated strategy to carbon-ion pencil beam scanning with multiple phase-controlled rescanning (PCR). In this simulation study, we quantitatively evaluated dose distributions based on 4-dimensional CT (4DCT) treatment planning.

Methods: Volumetric 4DCTs were acquired for 14 patients with lung tumors. Gross tumor volume, clinical target volume (CTV) and organs at risk (OARs) were delineated. Field-specific target volumes (FTVs) were calculated, and 48Gy(RBE) in a single fraction was prescribed to the FTVs delivered from four beam angles. The dose assessment metrics were quantified by changing the number of PCR and the results for the ungated and gated scenarios were then compared.

Results: For the ungated strategy, the mean dose delivered to 95% of the volume of the CTV (CTV-D95) was in average 45.3 ± 0.9 Gy(RBE) even with a single rescanning (1 × PCR). Using 4 × PCR or more achieved adequate target coverage (CTV-D95 = 46.6 ± 0.3 Gy(RBE) for ungated 4 × PCR) and excellent dose homogeneity (homogeneity index =1.0 ± 0.2% for ungated 4 × PCR). Applying respiratory gating, percentage of lung receiving at least 20 Gy(RBE) (lung-V20) and heart maximal dose, averaged over all patients, significantly decreased by 12% (p < 0.05) and 13% (p < 0.05), respectively.

Conclusions: Four or more PCR during PBS-CIRT improved dose conformation to moving lung tumors without gating. The use of a respiratory-gated strategy in combination with PCR reduced excessive doses to OARs.

No MeSH data available.


Related in: MedlinePlus