Positioning accuracy for lung stereotactic body radiotherapy patients determined by on-treatment cone-beam CT imaging

Richmond, Neil D.; Pilling, K.; Peedell, C.; Shakespeare, David; Walker, Christopher

doi:10.1259/bjr/54341099

Cited by 14 publications

(9 citation statements)

References 8 publications

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“…Bengua and colleagues [ 13 ] reported a similar findings with regard to the benefits of abdominal compression in lower lung lesions. Finally, Richmond et al [ 14 ] reported that abdominal compression led to a greater variation in set-up errors and changes in the mean value.…”

Section: Discussionmentioning

confidence: 99%

Comparative analysis of thermoplastic masks versus vacuum cushions in stereotactic body radiotherapy

et al. 2015

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BackgroundTo compare thermoplastic masks (TMP) and vacuum cushion system (VCS) to assess differences in interfraction set up accuracy in patients treated with stereotactic radiotherapy (SBRT) for oligometastatic lung cancer. Secondarily, to survey radiotherapy technologists to assess their satisfaction with the two systems.MethodsRetrospective study of patients treated with lung SBRT between 2008 to 2012 at our institution. Immobilization was performed for 73 treatment sessions (VCS = 40; TMP = 33). A total of 246 cone-beams were analysed. Patients considered ineligible for surgery with a life expectancy ≥6 months and performance status > 1 were included. Target lesion location was verified by cone beam computed tomography (CBCT) prior to each session, with displacements assessed by CBCT simulation prior to each treatment session. Couch shifts were registered prospectively in vertical, longitudinal, and latero-lateral directions to obtain Kernel coordinates (3D representation). Technologists were surveyed to assess their satisfaction with indexing, positioning, and learning curve of the two systems. Setup displacements were obtained in all patients for each treatment plan and for each session. To assess differences between the immobilization systems, a t-test (Welch) was performed.ResultsMean displacements for the TMP and VC systems, respectively, were as follows: session one, 0.64 cm vs 1.05 cm (p = 0.0002); session two, 0.49 cm vs 1.02 cm (p < 0.0001), and session three, 0.56 vs 0.97 cm (p = 0.0011). TMP resulted in significantly smaller shifts vs. VCS in all three treatment sessions. Technologists rated the learning curve, set up, and positioning more highly for TMP versus VCS.ConclusionsDue to the high doses and steep gradients in lung SBRT, accurate and reproducible inter-fraction set up is essential. We found that thermoplastic masks offers better reproducibility with significantly less interfractional set up displacement than vacuum cushions. Moreover, radiotherapy technologists rated the TMP system higher. Taken together, these two findings suggest that TMP may be preferable to VCS. However, more research is needed to determine both inter- and intrafraction error to identify the optimal immobilisation system for use in lung SBRT.

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Section: Discussionmentioning

confidence: 99%

Comparative analysis of thermoplastic masks versus vacuum cushions in stereotactic body radiotherapy

et al. 2015

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“…[8][9][10] Using those techniques, several authors evaluated intra-and interfractional variations in tumor motion in patients treated with SBRT for either lung or liver cancer. 4,[11][12][13] However, although four-dimensional computed tomography (4D CT) or cone beam CT (CBCT) were used in most of those studies, only a few evaluated the difference in the interfraction variation in tumor position between patients with large motion amplitude treated with and without abdominal compression for lung SBRT. Bissonnette et al reported that patients with abdominal compression demonstrated the greatest variability in tumor motion amplitude and in time spent on the treatment couch.…”

Section: Introductionmentioning

confidence: 99%

Interfraction variation in lung tumor position with abdominal compression during stereotactic body radiotherapy

et al. 2013

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Abdominal compression was effective for reducing the amplitude of tumor motion. However, in most of the authors' patients, the use of abdominal compression seemed to increase the interfraction variation in tumor position, despite reducing lung tumor motion. The daily tumor position deviated more systematically from the tumor position in the planning CT scan in the lateral and longitudinal directions in patients treated with abdominal compression compared to those treated without compression. Therefore, target matching is required to correct or minimize the interfraction variation.

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“…The simulated patient motion in the projection plane lowers the phase estimation for both the CRF and the SVM. A deviation of 1 pixel (0.7 mm) is less than the positioning error achieved by image‐guided correction and can therefore be tolerated. It can be expected that it is possible to detect an irregularity in the phase prediction for larger deviations or abnormalities of the breathing rhythm if the node potential

e x p ({normalΣ}_{k = 1}^{K} θ_{k} f_{k} false(y_{t}, y_{t - 1}, {bold-italicx}_{t} false))

falls below a certain threshold.…”

Section: Discussionmentioning

confidence: 99%

Conditional random fields for phase‐based lung feature tracking with ultra‐low‐dose x‐rays

et al. 2019

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Purpose During radiation therapy, a continuous internal tumor monitoring without additional imaging dose is desirable. In this study, a sequential feature‐based position estimation with ultra‐low‐dose (ULD) kV x rays using linear‐chain conditional random fields (CRFs) is performed. Methods Four‐dimensional computed tomography (4D‐CTs) of eight patients serve as a‐priori information from which ULD projections are simulated using a Monte Carlo method. CRFs are trained with Local Energy‐based Shape Histogram features extracted from the ULD images to estimate one out of ten breathing phases from the 4D‐CT associated with the tumor position. Results Compared to a mean accuracy for ±1 breathing phase of 0.867 using a support vector machine (SVM), a mean accuracy of 0.958 results for the CRF with ten incident photons per pixel. This corresponds to a position estimation with a discretization error of 2.4–5.3 mm assuming a linear displacement relation between the breathing phases and a systematic error of 2.0–4.4 mm due to motion underestimation of the 4D‐CT. Conclusions The tumor position estimation is comparable to state‐of‐the‐art methods despite its low imaging dose. Training CRFs further allows a prediction of the following phase and offers a precise post‐treatment evaluation tool when decoding the full image sequence.

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Positioning accuracy for lung stereotactic body radiotherapy patients determined by on-treatment cone-beam CT imaging

Cited by 14 publications

References 8 publications

Comparative analysis of thermoplastic masks versus vacuum cushions in stereotactic body radiotherapy

Comparative analysis of thermoplastic masks versus vacuum cushions in stereotactic body radiotherapy

Interfraction variation in lung tumor position with abdominal compression during stereotactic body radiotherapy

Conditional random fields for phase‐based lung feature tracking with ultra‐low‐dose x‐rays

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