Improving Intra-Fractional Target Position Accuracy Using a 3D Surface Surrogate for Left Breast Irradiation Using the Respiratory-Gated Deep-Inspiration Breath-Hold Technique

Abstract

PurposeTo evaluate the use of 3D optical surface imaging as a surrogate for respiratory gated deep-inspiration breath-hold (DIBH) for left breast irradiation.Material and MethodsPatients with left-sided breast cancer treated with lumpectomy or mastectomy were selected as candidates for DIBH treatment for their external beam radiation therapy. Treatment plans were created on both free breathing (FB) and DIBH computed tomography (CT) simulation scans to determine dosimetric benefits from DIBH. The Real-time Position Management (RPM) system was used to acquire patient's breathing trace during DIBH CT acquisition and treatment delivery. The reference 3D surface models from FB and DIBH CT scans were generated and transferred to the “AlignRT” system for patient positioning and real-time treatment monitoring. MV Cine images were acquired during treatment for each beam as quality assurance for intra-fractional position verification. The chest wall excursions measured on these images were used to define the actual target position during treatment, and to investigate the accuracy and reproducibility of RPM and AlignRT.ResultsReduction in heart dose can be achieved using DIBH for left breast/chest wall radiation. RPM was shown to have inferior correlation with the actual target position, as determined by the MV Cine imaging. Therefore, RPM alone may not be an adequate surrogate in defining the breath-hold level. Alternatively, the AlignRT surface imaging demonstrated a superior correlation with the actual target positioning during DIBH. Both the vertical and magnitude real-time deltas (RTDs) reported by AlignRT can be used as the gating parameter, with a recommended threshold of ±3 mm and 5 mm, respectively.ConclusionThe RPM system alone may not be sufficient for the required level of accuracy in left-sided breast/CW DIBH treatments. The 3D surface imaging can be used to ensure patient setup and monitor inter- and intra- fractional motions. Furthermore, the target position accuracy during DIBH treatment can be improved by AlignRT as a superior surrogate, in addition to the RPM system.

Dosimetric Considerations in Respiratory-Gated Deep Inspiration Breath-Hold for Left Breast Irradiation

“…Enhanced patient comfort likely results in more reliable positioning and reproducibility of treatment leading to decreased chances of marginal misses, which are possible as determined by our previous work and the verification CT in our current study. 25 The large variation in dose coverage in the verification plans in Table 3 demonstrates this reduced dose coverage and emphasizes the benefit of using AlignRT for target setup and monitoring during DIBH treatments. The most apparent limitation of our work is that we had reduced power to detect any reliable correlation between CW excursion and dosimetric advantage, and even very few outliers could affect our results.…”

“…24 We recently published our data suggesting that AlignRT can result in more accurate treatment delivery than RPM alone during DIBH. 25 In the current study, we hypothesized that the CW excursion from DIBH would be quantitatively associated with reductions in cardiac and lung doses, and the use of AlignRT would help ensure treatment accuracy. The detailed clinical protocol of incorporating AlignRT for left breast DIBH treatments and the dosimetric considerations with the DIBH protocol are presented in this study.…”

Improving the reproducibility of voluntary deep inspiration breath hold technique during adjuvant left-sided breast cancer radiotherapy

“…Rong et al found that the RPM system alone is not sufficient to verify the BHL [18] and used three-dimensional (3D) surface imaging as a second method. Likewise, 3D surface imaging was used by Betgen et al [9] to quantify the intra-and inter-fraction differences and found that the interfraction variability was particularly significant.…”

Prospective assessment of deep inspiration breath-hold using 3-dimensional surface tracking for irradiation of left-sided breast cancer

“…Tools for real-time motion assessment, including surface-tracking systems (AlignRT; Vision RT, Ltd, London, United Kingdom) and patient-centered techniques like active coaching and real-time patient feedback devices, have been implemented to ensure consistent inspiration during treatment. 18 The efficacy and feasibility of voluntary DIBH, however, depend on a variety of patient-and tumorspecific factors, including individual anatomy, patient compliance, tumor location, and duration of treatment. We sought to understand the feasibility, dosimetric efficacy, and practical implications (treatment time and variability) of DIBH in a prospectively enrolled registry of patients scanned with free-breathing (FB) or DIBH but ultimately treated with either technique based on physician assessment.…”