Unanticipated Radiation Replanning for Stage III Non-small Cell Lung Cancer

Purpose

The purpose of this study was to identify factors associated with unanticipated radiation therapy (RT) replanning in stage III non-small cell lung cancer (NSCLC).

Methods and Materials

Patients from a single institution with newly diagnosed stage III NSCLC treated with radical RT from January 1, 2016, to December 31, 2019, were retrospectively analyzed. The frequency and reasons for replanning were determined. Logistic regression analysis was used to identify factors associated with replanning.

Results

Of 144 patients included in this study, 11% (n = 16) required replanning after the start of RT. The reason for replanning in these 16 patients was changes in the target detected by cone beam computed tomography (shift in 10 patients, shrinkage in 5 patients, and growth in 1 patient). Larger planning target volume (primary and nodal) was statistically predictive of replanning (odds ratio, 2.5; 95% CI, 1.2-5.4; P = .02). The actuarial median overall survival was 33.3 months (95% CI, 10.3-43.9) for the 16 patients who were replanned and 36.3 months (95% CI, 27.4-66.5) for the remaining 128 patients (P = .96). The median time to local recurrence was 25.0 months (95% CI, 10.3-41.3) for those patients who underwent replanning, which was similar to those patients who did not undergo replanning (19.5 months; 95% CI, 11.8-23.2; P = .28).

Conclusions

In this study, 11% of patients treated with radical RT for NSCLC required replanning due to changes in the target detected by cone beam computed tomography. A larger planning target volume predicts a higher likelihood of requiring adaptive RT. Overall survival and local control were similar between patients who were replanned compared with those who were not replanned.

A Scale-Adaptive Matching Algorithm for Underwater Acoustic and Optical Images

Underwater acoustic and optical data fusion has been developed in recent decades. Matching of underwater acoustic and optical images is a fundamental and critical problem in underwater exploration because it usually acts as the key step in many applications, such as target detection, ocean observation, and joint positioning. In this study, a method of matching the same underwater object in acoustic and optical images was designed, consisting of two steps. First, an enhancement step is used to enhance the images and ensure the accuracy of the matching results based on iterative processing and estimate similarity. The acoustic and optical images are first pre-processed with the aim of eliminating the influence of contrast degradation, contour blur, and image noise. A method for image enhancement was designed based on iterative processing. In addition, a new similarity estimation method for acoustic and optical images is also proposed to provide the enhancement effect. Second, a matching step is used to accurately find the corresponding object in the acoustic images that appears in the underwater optical images. In the matching process, a correlation filter is applied to determine the correlation for matching between images. Due to the differences of angle and imaging principle between underwater optical and acoustic images, there may be major differences of size between two images of the same object. In order to eliminate the effect of these differences, we introduce the Gaussian scale-space, which is fused with multi-scale detection to determine the matching results. Therefore, the algorithm is insensitive to scale differences. Extensive experiments demonstrate the effectiveness and accuracy of our proposed method in matching acoustic and optical images.

An improved method for analyzing and reporting patterns of in-field recurrence after stereotactic ablative radiotherapy in early-stage non-small cell lung cancer

INTRODUCTION

Patterns of local, regional, and distant failure after stereotactic ablative radiotherapy (SABR) for early-stage non-small cell lung cancer (NSCLC) have been widely reported. However, reliable methods for analyzing causes of local failure are lacking. We describe a method for analyzing and reporting patterns of in-field recurrence after SABR, incorporating dosimetric parameters from initial treatment plan as well as geometric information from diagnostic images at recurrence.

MATERIAL AND METHODS

Diagnostic CT images at recurrence were registered with initial treatment planning images and radiation dose by deformable image registration. Recurrent gross tumor volume (rGTV) and centroid (geometric center of rGTV) were delineated. In-field failure was classified as centroids originating within the original planning target volume. Dose-volume histograms for each rGTV were used to further classify in-field recurrences as central high-dose (dose to 95% of rGTV [rGTVD95%] ≥95% of dose prescribed to PTV) or peripheral high-dose (rGTVD95% <95% of dose prescribed to PTV).

RESULTS

634 patients received SABR from 2004 to 2014 with 48 local recurrences. 35 of these had evaluable images with 16 in-field recurrences: 9 central high-dose, 6 peripheral high-dose, and 1 had both. Time to and volume of recurrence were not statistically different between central versus peripheral high-dose recurrences. However mean rGTV dose, mean centroid dose, and rGTVD95% were higher for central versus peripheral high-dose recurrences.

CONCLUSION

We report a standardized method for analysis and classification of in-field recurrence after SABR. There were more central as opposed to peripheral high-dose recurrences, suggesting biological rather than technical issues underlying majority of in-field failures.

"Dose of the day" based on cone beam computed tomography and deformable image registration for lung cancer radiotherapy

Purpose

Adaptive radiotherapy (ART) has potential to reduce toxicity and facilitate safe dose escalation. Dose calculations with the planning CT deformed to cone beam CT (CBCT) have shown promise for estimating the “dose of the day”. The purpose of this study is to investigate the “dose of the day” calculation accuracy based on CBCT and deformable image registration (DIR) for lung cancer radiotherapy.

Methods

A total of 12 lung cancer patients were identified, for which daily CBCT imaging was performed for treatment positioning. A re‐planning CT (rCT) was acquired after 20 Gy for all patients. A virtual CT (vCT) was created by deforming initial planning CT (pCT) to the simulated CBCT that was generated from deforming CBCT to rCT acquired on the same day. Treatment beams from the initial plan were copied to the vCT and rCT for dose calculation. Dosimetric agreement between vCT‐based and rCT‐based accumulated doses was evaluated using the Bland‐Altman analysis.

Results

Mean differences in dose‐volume metrics between vCT and rCT were smaller than 1.5%, and most discrepancies fell within the range of ± 5% for the target volume, lung, esophagus, and heart. For spinal cord D_max, a large mean difference of −5.55% was observed, which was largely attributed to very limited CBCT image quality (e.g., truncation artifacts).

Conclusion

This study demonstrated a reasonable agreement in dose‐volume metrics between dose accumulation based on vCT and rCT, with the exception for cases with poor CBCT image quality. These findings suggest potential utility of vCT for providing a reasonable estimate of the “dose of the day”, and thus facilitating the process of ART for lung cancer.

Toward adaptive radiotherapy for lung patients: feasibility study on deforming planning CT to CBCT to assess the impact of anatomical changes on dosimetry

Changes in lung architecture during a course of radiotherapy can alter the planned dose distribution to the extent that it becomes clinically unacceptable. This study aims to validate a quantitative method of determining whether a replan is required during the course of conformal radiotherapy. The proposed method uses deformable image registration (DIR) to flexibly map planning CT (pCT) data to the anatomy of online CBCT images. The resulting deformed CT (dCT) images are used as a basis for assessing the effect of anatomical change on dose distributions. The study used retrospective data from a sample of seven replanned lung patients. The settings of an in-house, open-source DIR algorithm were first optimised for CT-to-CBCT registrations of the anatomy of the thorax. Using these optimised parameters, each patient's pCT was deformed to the CBCT acquired immediately before the replan. Registration accuracy was rigorously validated both geometrically and dosimetrically to confirm that the dCTs could reliably be used to inform replan decisions. A retrospective evaluation of the changes in dose delivered over time was then carried out for a single patient to demonstrate the clinical application of the proposed method. The geometric analysis showed good agreement between deformed structures and those same structures manually outlined on the CBCT images. Results were consistently better than those achieved with rigid-only registration. In the dosimetric analysis, dose distributions derived from the dCTs were found to match closely to the 'gold standard' replan CT (rCT) distributions across dose volume histogram and absolute dose difference measures. The retrospective analysis of serial CBCTs of a single patient produced reliable quantitative assessment of the dose delivery. Had the proposed method been available at the time of treatment, it would have enabled a more objective replan decision. DIR is a valuable clinical tool for dose recalculation in adaptive radiotherapy protocols for lung cancer patients.

Cone Beam Computed Tomography: The Challenges and Strategies in Its Application for Dose Accumulation

Online image guidance using cone beam computed tomography (CBCT) has greatly improved the geometric precision of radiotherapy. Changes in anatomy are common during a course of fractionated treatment, resulting in dose deviation from the planned distribution. There is increased interest in performing dose accumulation to compute the actual delivered dose and to adapt the treatment when necessary. This can be achieved by delineating the volume of interest and by generating "dose of the day" through dose computation on the CBCT. However, the image quality and the accuracy of the CT number of CBCT are deemed to be inferior to fan beam CT, which increases the uncertainty associated in this process. A review of literature was conducted to assess the reliability of and to examine strategies for overcoming the challenges in using CBCT for volume delineation and dose computation. The review demonstrates that the uncertainty varies across body sites, and different strategies have been recommended to generate comparable results to images from CT simulators. This facilitates a better understanding of the potential and the limitation of using CBCT for dose accumulation.