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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 four beam angles for (a) ungated and (b) gated irradiation. Planning dose distribution and accumulated dose simulations with 1 × PCR, 4 × PCR, and 8 × PCR. In the supine position, the beam angle was set to 20, 70, 110, and 340 degrees. The respiratory cycle was 4.2 sec. Yellow lines demonstrate the CTV (patient no. 7). Green arrows show beam direction. Dose assessment metrics for all 14 cases as a function of the number of rescannings. D95, Dmax, and Dmin for (c) ungated and (d) gated strategies. The homogeneity index (HI) is for (e) ungated and (f) gated strategies.
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Fig2: Carbon-ion dose distributions with four beam angles for (a) ungated and (b) gated irradiation. Planning dose distribution and accumulated dose simulations with 1 × PCR, 4 × PCR, and 8 × PCR. In the supine position, the beam angle was set to 20, 70, 110, and 340 degrees. The respiratory cycle was 4.2 sec. Yellow lines demonstrate the CTV (patient no. 7). Green arrows show beam direction. Dose assessment metrics for all 14 cases as a function of the number of rescannings. D95, Dmax, and Dmin for (c) ungated and (d) gated strategies. The homogeneity index (HI) is for (e) ungated and (f) gated strategies.

Mentions: Figure 2 gives the dose distributions of a four-field plan for the same case. Without gating and a low number of PCR (e.g. 1 × PCR), the use of multiple coplanar fields reduced hot and cold spots and provided better conformation to the CTV than the single field mentioned above. D95, Dmax and Dmin values of the CTV improved with the use of multiple fields, from 44.4 Gy(RBE), 53.3 Gy(RBE), and 43.7 Gy(RBE) with a single field to 46.2 Gy(RBE), 49.9 Gy(RBE), and 45.1 Gy(RBE) with four fields, respectively. Moreover, the addition of gating provided better dose volume indices for the CTV than with the ungated plans. This tendency was particularly obvious with a single port with 1 × PCR (Figure 1), but the magnitude of improvement in dose uniformity became less prominent with 4× and 8 × PCR (Figure 1) and with four beam angles (Figure 2). With four beam fields using the gated strategy, an increase in PCR frequency provided only a slight improvement in dose metrics, with D95 of the CTV being 46.3 Gy(RBE), 46.4 Gy(RBE), and 46.4 Gy(RBE) for 1×, 4× and 8 × PCR, respectively.Figure 2


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 four beam angles for (a) ungated and (b) gated irradiation. Planning dose distribution and accumulated dose simulations with 1 × PCR, 4 × PCR, and 8 × PCR. In the supine position, the beam angle was set to 20, 70, 110, and 340 degrees. The respiratory cycle was 4.2 sec. Yellow lines demonstrate the CTV (patient no. 7). Green arrows show beam direction. Dose assessment metrics for all 14 cases as a function of the number of rescannings. 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

Fig2: Carbon-ion dose distributions with four beam angles for (a) ungated and (b) gated irradiation. Planning dose distribution and accumulated dose simulations with 1 × PCR, 4 × PCR, and 8 × PCR. In the supine position, the beam angle was set to 20, 70, 110, and 340 degrees. The respiratory cycle was 4.2 sec. Yellow lines demonstrate the CTV (patient no. 7). Green arrows show beam direction. Dose assessment metrics for all 14 cases as a function of the number of rescannings. D95, Dmax, and Dmin for (c) ungated and (d) gated strategies. The homogeneity index (HI) is for (e) ungated and (f) gated strategies.
Mentions: Figure 2 gives the dose distributions of a four-field plan for the same case. Without gating and a low number of PCR (e.g. 1 × PCR), the use of multiple coplanar fields reduced hot and cold spots and provided better conformation to the CTV than the single field mentioned above. D95, Dmax and Dmin values of the CTV improved with the use of multiple fields, from 44.4 Gy(RBE), 53.3 Gy(RBE), and 43.7 Gy(RBE) with a single field to 46.2 Gy(RBE), 49.9 Gy(RBE), and 45.1 Gy(RBE) with four fields, respectively. Moreover, the addition of gating provided better dose volume indices for the CTV than with the ungated plans. This tendency was particularly obvious with a single port with 1 × PCR (Figure 1), but the magnitude of improvement in dose uniformity became less prominent with 4× and 8 × PCR (Figure 1) and with four beam angles (Figure 2). With four beam fields using the gated strategy, an increase in PCR frequency provided only a slight improvement in dose metrics, with D95 of the CTV being 46.3 Gy(RBE), 46.4 Gy(RBE), and 46.4 Gy(RBE) for 1×, 4× and 8 × PCR, respectively.Figure 2

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