Volumetric multiphase ventilation imaging based on four‐dimensional computed tomography for functional lung avoidance radiotherapy

Abstract

Purpose Current computed tomography (CT)‐based lung ventilation imaging (CTVI) techniques derive a static ventilation image without temporal information. This research aims to develop a four‐dimensional CT (4DCT)‐based multiphase dynamic ventilation imaging framework capable of recovering the entire ventilation process throughout the breathing cycle for functional lung avoidance radiotherapy (FLART). Methods A total of 15 free‐breathing thoracic 4DCT scans of lung or esophageal cancer patients were collected from the public datasets. The lung region of each phase image was first delineated, and then the mask‐free isotropic total variation image registration algorithm was used to derive the deformation vector fields between the end‐expiration (EE) phase and other phases. As a surrogate of ventilation, the voxel‐wise local expansion ratio of each phase relative to the EE phase was estimated using the parameterized Integrated Jacobian Formulation method in the EE phase coordinate. Lastly, the dynamic ventilation images were generated by warping these phase‐specific local expansion distributions with a same geometry into their respective breathing phases. Quantitative analysis, including interphase Spearman correlation coefficients, voxel‐wise, and regional‐wise expansion/contraction tracking, were performed to indirectly validate the proposed method. Results The proposed method maintains the physiological meaning of ventilation on each phase and enables to recover the dynamic lung ventilation process. The mean interphase Spearman correlations ranged between 0.23 ± 0.20 and 0.93 ± 0.04 and decreased near the EE phase. Only 26.2% (2.59E + 6 out of 9.89E + 6) of lung voxels exhibited the same expansion/contraction pattern as the global lung. Qualitative and quantitative evaluations of the interphase ventilation distribution difference show that ventilation spatiotemporal heterogeneities generally exist during respiration. Conclusions In contrast to conventional CTVI metrics, our method enables to extract additional phase‐resolved respiration‐correlated information and reflects the generally existed ventilation spatiotemporal heterogeneities. Subsequent studies with quantitative phase‐by‐phase cross‐modality evaluations will further explore its potential to deepen our understanding of lung function and respiration mechanics and also to facilitate more accurate implementation of FLART.

Establishing a 4D-CT lung function related volumetric dose model to reduce radiation pneumonia

“…At present, many examinations can provide detailed distribution information of lung function, including proton lung MRI 9 , phase-cycled balanced SSFP (bSSFP) acquisition MRI 10 – 12 , hyperpolarized gas (HPG) MRI 13 , Electrical impedance tomography (EIT) 14 , 15 . Fourier decomposition magnetic resonance imaging (FD-MRI) 16 – 18 , SPECT/CT 2 , 18 – 21 , 4D-CT 22 – 27 , multimodal imaging 28 , and it is applied in radiotherapy planning to avoid higher damage to high-function organs 29 – 32 . Among these examinations, 4D-CT is the most popular 33 , 34 , the operation is the simplest, and the radiation needed to be received is low.…”

Automatic planning for functional lung avoidance radiotherapy based on function-guided beam angle selection and plan optimization

“…However, recent studies revealed that temporary lung function defects exist and their function may recover after or during treatment (Yuan et al 2012), necessitating future investigations to identify such temporary defects pretreatment and protect them when making treatment plans. Additionally, the use of free-breathing images fails to fully capture the influence of respiratory motion on the derived lung function maps (Huang et al 2022b), and the imperfect registration between SPECT and planning CT images may result in inconsistencies between the generated and actual lung function maps (Yin et al 2010). However, the proposed AP-FLART is also applicable to other lung function mapping techniques that may mitigate these challenges.…”

Functional imaging for assessing regional lung ventilation in preclinical and clinical research

“…One ongoing phase 2 trial demonstrates 4D CT-guided ventilation as a useful clinical application in functional avoidance in patients with at least grade 2 radiation pneumonitis ( 59 ). Similar clinical trials are being conducted globally to optimize radiation therapy in lung cancer patients, like understanding lung ventilation physiology in chest radiation treatment, while still decreasing radiation dose administration, reducing tumor burden, and preserving ventilation ( 60 , 61 ).…”