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. 2014 May 8;15(3):4661.
doi: 10.1120/jacmp.v15i3.4661.

Optimization strategies for pulsed low-dose-rate IMRT of recurrent lung and head and neck cancers

Shengwei Kang  1 , Jinyi Lang, Pei Wang, Jie Li, Muhan Lin, Xiaoming Chen, Ming Guo, Fu Chen, Lili Chen, Charlie Ming Ma
Affiliations

Optimization strategies for pulsed low-dose-rate IMRT of recurrent lung and head and neck cancers

Shengwei Kang et al. J Appl Clin Med Phys. .

Abstract

Pulsed low-dose-rate radiotherapy (PLDR) has been proven to be a valid method of reirradiation. Previous studies of recurrent cancer radiotherapy were mainly based on conventional 3D CRT and VMAT delivery techniques. There are difficulties in IMRT planning using existing commercial treatment planning systems (TPS) to meet the PLDR protocol. This work focuses on PLDR using ten-field IMRT and a commercial TPS for two specific sites: recurrent lung cancers and head and neck cancers. Our PLDR protocol requires that the maximum dose to the PTV be less than 0.4 Gy and the mean dose to be 0.2 Gy per field. We investigated various planning strategies to meet the PLDR requirements for 20 lung and head and neck patients. The PTV volume for lung cases ranged from 101.7 to 919.4 cm3 and the maximum dose to the PTV ranged from 0.22 to 0.39 Gy. The PTV volume for head and neck cases ranged from 66.2 to 282.1 cm3 and the maximum dose to the PTV ranged from 0.21 to 0.39 Gy. With special beam arrangements and dosimetry parameters, it is feasible to use a commercial TPS to generate quality PLDR IMRT plans for lung and head and neck reirradiation.

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Figures

Figure 1
Figure 1
The minimum dose (a), maximum dose (b), and mean dose (c) of the PTV of each gantry angle/field for ten lung cases, and the distribution (d) of the minimum dose, maximum dose, and mean dose (unit: cGy).
Figure 2
Figure 2
Isodose lines (a) (66 Gy and 70 Gy, respectively) and DVHs (b) of the PTV and critical structures of Patient 3.
Figure 3
Figure 3
The minimum dose (a), maximum dose (b), and mean dose (c) of the PTV of each gantry angle/field for ten head and neck cases, and the distribution (d) of the minimum dose, maximum dose, and mean dose (unit: cGy).
Figure 4
Figure 4
Isodose lines (a) (10 Gy to 65 Gy in 5 Gy steps) and (b) DVHs of the PTV and critical structures of Patient 1.
Figure 5
Figure 5
The reference ring structures that were used to minimize hot spots inside the target volume. The red contour is the PTV. Four reference rings were used in this case.
Figure 6
Figure 6
Example of a particular beam angle that delivers a maximum dose to the PTV between 35 cGy and 40 cGy for Patient 10.
Figure 7
Figure 7
The isodose distributions of a 3D CRT plan (a) and an IMRT plan (b), the corresponding DVHs of the two plans (c) and (d), and the comparison of the DVHs of the two plans (e) for a lung cancer patient.
Figure 8
Figure 8
The isodose distributions of a 3D CRT plan (a) and an IMRT plan (b), the corresponding DVHs of the two plans (c) and (d), and the comparison of the DVHs of the two plans (e) for a head and neck patient.
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