Abstract
BackgroundThe principal aim of this study was to evaluate the feasibility of incorporating four-dimensional (4D)-computed tomography (CT)-based functional information into treatment planning and to evaluate the potential benefits of individualized beam setups to better protect lung functionality in patients with non-small cell lung cancer (NSCLC).MethodsPeak-exhale and peak-inhale CT scans were carried out in 16 patients with NSCLC treated with intensity-modulated radiotherapy (IMRT). 4D-CT-based ventilation information was generated from the two sets of CT images using deformable image registration. Four kinds of IMRT plans were generated for each patient: two anatomic plans without incorporation of ventilation information, and two functional plans with ventilation information, using either five equally spaced beams (FESB) or five manually optimized beams (FMOB). The dosimetric parameters of the plans were compared in terms of target and normal tissue structures, with special focus on dose delivered to total lung and functional lung.ResultsIn both the anatomic and functional plans, the percentages of both the functional and total lung regions irradiated at V5, V10, and V20 (percentage volume irradiated to >5, >10 and >20 Gy, respectively) were significantly lower for FMOB compared with FESB (P < 0.05), but there was no significant difference for V30 (P > 0.05). Compared with FESB, a greater degree of sparing of the functional lung was achieved in functional IMRT plans with optimal beam arrangement, without compromising target volume coverage or the irradiated volume of organs at risk, such as the spinal cord, esophagus, and heart.ConclusionsPulmonary ventilation image-guided IMRT planning with further optimization of beam arrangements improves the preservation of functional lung in patients with NSCLC.
Highlights
The principal aim of this study was to evaluate the feasibility of incorporating four-dimensional (4D)-computed tomography (CT)-based functional information into treatment planning and to evaluate the potential benefits of individualized beam setups to better protect lung functionality in patients with non-small cell lung cancer (NSCLC)
The dosimetric parameters for the total and functional lung regions between different beam arrangements are shown in Tables 5 and 6. In both the anatomic and functional plans, V5, V10, and volume irradiated to >20 Gy (V20) in the total and functional lung regions were significantly lower in five manually optimized beams (FMOB), compared with five equally spaced beams (FESB) (P < 0.05), though there was no significant difference for V30 (P > 0.05)
The maximum doses delivered to the spinal cord in the anatomic and functional plans were slightly lower for FMOB compared with FESB, but the difference was not significant (P > 0.05)
Summary
The principal aim of this study was to evaluate the feasibility of incorporating four-dimensional (4D)-computed tomography (CT)-based functional information into treatment planning and to evaluate the potential benefits of individualized beam setups to better protect lung functionality in patients with non-small cell lung cancer (NSCLC). Several techniques exist for pulmonary ventilation imaging, including single photon emission computed tomography and X-ray CT (SPECT-CT) [7,8], hyperpolarized helium-3 magnetic resonance imaging (3He-MRI) [9,10], and inert xenon CT (Xe-CT) [11] All these imaging modalities can provide useful ventilation information, each has serious drawbacks, such as high cost, low resolution, long scan time and/or low accessibility [12]. Ding et al [14] explored the changes in lung ventilation after RT, and Yamamoto et al [15] and Yaremko et al [16] discussed the idea of designing treatment plans to avoid high-ventilation areas of the lung Most of these studies considered treatment planning based on fixed-beam arrangements, and to the best of our knowledge, no studies have compared the use of different beam arrangements
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