Optical Surface Monitoring System Research Articles

Clinical Implementation of Optical Surface Imaging Systems in Vulvar Cancer to Reduce Setup Error

Optical surface monitoring system (OSMS) could achieve continuous monitoring of patient position through a nonradiographic and noninvasive technology, which has been widely applied to many sites of radiation therapy including breast, intracranial, head and neck, abdomen, and the extremities. However, no study has investigated the application of OSMS in radiation therapy of vulvar cancer. In this study, we hypothesized using OSMS would reduce setup error in the vulvar cancer compared to standard laser-based setup (SLS). A single-center prospective trial included 10 patients with vulvar cancer treated with intensity modulated radiation therapy (IMRT) for a total of 250 fractions. Every patient was immobilized with Styrofoam in a frog-leg position and used marks on the patient's skin to align to the room lasers for pre-setup. The treatment couch values of lateral (Lat), longitudinal (Lng), vertical (Vrt) in three translation directions and Rtn (the rotation along the z axis), Pitch (the rotation along the x axis), Roll (the rotation along the y axis) in three rotations directions were recorded. Then completed the setup of patient with information from a surface imaging system and obtained deviation values. Setup is followed by pretreatment cone-beam computed tomography (CBCT) to further verify patient and target position by registering to the planning CT with respect to bony anatomy. With CBCT as a gold standard for patient setup, the absolute values of setup error and error distribution of SLS method and OSMS method from the same patient in above six directions were compared. The mean of absolute values of setup errors in the SLS method were significantly higher than those of OSMS method in Lat (0.34cm vs 0.20cm), Lng (0.42cm vs 0.29cm), Vrt (0.43cm vs 0.28cm) and Rtn (0.90° vs 0.67°) directions (P<0.05). The mean errors in SLS and OSMS methods in Pitch and Roll directions were 0.93° and 1.02° (P = 0.16), 0.42° and 0.45° (P = 0.48), respectively, with no significant difference. In the OSMS method, the distribution rates of the setup errors within 0.5cm in three translation directions and within 1.5° in three rotations directions were significantly higher in Lat (90.8% vs 80.4%), Lng (82.0% vs 68.8%), Vrt (83.2% vs 65.6%), and Rtn (91.2% vs 80.4%) directions than those of SLS method (P<0.05). In the Pitch (79.2% vs 80.4%) and Roll (97.2% vs 98.0%) directions, the distribution rates of the OSMS method were slightly lower than those of the SLS method, with no significant difference (P = 0.738 and P = 0.559). The implementation of OSMS in IMRT for vulvar cancer could reduce setup error and increase precision of setup, especially for the directions of Lat, Lng, Vrt and Rtn.

Variation in Left Anterior Descending Coronary Artery Accumulated Dose Estimates during Breast Cancer Radiotherapy

Left anterior descending (LAD) coronary artery RT dose has been associated with the risk of coronary ischemic events in patients with breast cancer treated with radiotherapy (RT). However, consensus dose constraints commonly utilize mean heart dose, which has been shown to be an inadequate surrogate for LAD dose. Given the LAD is adjacent to the steep dose gradients of the left breast/chest wall, we hypothesize that variations in patient positioning or depth of breath hold may contribute to significant deviations in daily LAD dose exposure compared to predicted. Our objective was to investigate variations in accumulated LAD dose in patients with left-sided breast cancer treated with RT. Retrospective analysis of 10 consecutive patients with left-sided breast cancer treated between 2019-2022 with volumetric modulated arc therapy (VMAT) in the supine position. RT was delivered using daily cone beam computed tomography (CBCT) image guidance with deep-inspiratory breath hold technique and an optical surface monitoring system. Daily CBCT scans were individually registered to each planning CT based on daily positional changes. The LAD was manually segmented and transformed to each CBCT. Daily fractional dose was calculated (mean, volume receiving 15 Gy [V15 Gy], V30 Gy, and max) and summed to produce an accumulated dose which was compared to the predicted dose. Significant deviations in accumulated dose were defined as at least ±15% from predicted. The RT targets included breast/chest wall only (n = 1), supraclavicular nodes (n = 8), and/or internal mammary chain (n = 5). All plans were prescribed to 50 Gy in 25 fractions. The median predicted mean heart dose was 5.1 Gy. Overall, there were no significant differences between the median predicted vs. accumulated LAD doses: mean 10.4 vs. 10.2 Gy, V15 Gy 21% vs. 25%, V30 Gy 0% vs. 1%, max 24.5 vs 25.7 Gy (all p>.05). However, there was a subset of patients (n = 5, 50%) with significant deviations in accumulated vs. predicted dose (at least ±15%). For LAD mean, n = 2 had higher accumulated vs. predicted doses (16.6 vs. 11.6 Gy; 14.6 vs. 12.8 Gy), while n = 3 had lower (21.8 vs. 26.5 Gy; 2.7 vs. 4.2 Gy; 13.9 vs. 16.5 Gy). For LAD V15 Gy, n = 3 had higher accumulated vs. predicted doses (43 vs. 35%; 51% vs. 25%; 14% vs. 9%), while n = 2 had lower (49% vs. 61%; 37% vs. 56%). For LAD V30 Gy, n = 4 had higher accumulated vs. predicted doses (12% vs. 5%; 5% vs. 0%; 4% vs. 0%; 4% vs. 2%), while n = 1 had lower (32% vs. 44%). Daily setup differences, including the extent of inspiratory breath hold, may contribute to deviations in accumulated LAD dose (more than 15% of predicted) in approximately half of patients and were more pronounced in V15 and V30 Gy metrics. The potential for significant LAD dose uncertainty in a clinically meaningful subset of patients should be recognized and warrants further analysis in an expanded cohort.

Development of a new coordinate calibration phantom for a light-section-based optical surface monitoring system.

A calibration phantom made of Derlin requires manual translational and rotational adjustments when calibrating a light-section-based optical surface monitoring system (VOXELAN) with a phantom material that insufficiently reflects the red-slit laser of the system. This study aimed to develop a new calibration phantom using different materials and to propose a procedure that minimizes setup errors. The new phantom, primarily made of PET100, which exhibits good reflectivity without scattering or attenuating the red-slit laser at the phantom surface, was shaped in a manner similar to that of previous designs. The detection accuracy and stability were evaluated using six different regions of interest (ROIs) and compared with previous phantom designs. The coordinate coincidence between the machine and VOXELAN was compared for both phantom designs. The detection accuracy and stability of the new phantom in the reference ROI setting were found to be better than those of previous phantoms. In the lateral, longitudinal, and vertical directions, the coordinate coincidences in translational directions for the previous phantom were obtained at 1.07 ± 0.66, 1.46 ± 0.47, and 0.26 ± 0.83mm, whereas those for the new phantom were obtained at 0.28 ± 0.21, 0.18 ± 0.30, and -0.30 ± 0.29mm, respectively. The rotational errors of the two phantoms were identical. The new phantom exhibited improved detection stability because of its good reflectivity. Additionally, the new placement procedure was linked to the six-degrees-of-freedom couch. A combination of the new phantom and its new placement procedure is suitable for coordinate calibration of VOXELAN.

Reproducibility and stability of spirometer-guided deep inspiration breath-hold in left-breast treatments using an optical surface monitoring system.

The aim of this study was to evaluate the reproducibility and stability of left breast positioning during spirometer-guided deep-inspiration breath-hold (DIBH) radiotherapy using an optical surface imaging system (AlignRT). The AlignRT optical tracking system was used to monitor five left-sided breast cancer patients treated using the Active Breathing Coordinator spirometer with DIBH technique. Treatment plans were created using an automated hybrid-VMAT technique on DIBH CTs. A prescribed dose of 60Gy to the tumor bed and 50Gy to the breast in 25 fractions was planned. During each treatment session, the antero-posterior (VRT), superior-inferior (LNG), and lateral (LAT) motion of patients was continuously recorded by AlignRT. The intra-breath-hold stability and the intra- and inter-fraction reproducibility were analyzed for all breath-holds and treatment fractions. The dosimetric impact of the residual motion during DIBH was evaluated from the isocenter shifts amplitudes obtained from the 50%, 90%, and 100% cumulative distribution functions of intra-fractional reproducibility. The positional variations of 590 breath-holds as measured by AlignRT were evaluated. The mean intra-breath-hold stability during DIBH was 1.0±0.4mm, 2.1±1.9mm, and 0.7±0.5mm in the VRT, LNG, and LAT directions, with a maximal value of 8.8mm in LNG direction. Similarly, the mean intra-breath-hold reproducibility was 1.4±0.8mm, 1.7±1.0mm, and 0.8±0.5mm in the VRT, LNG, and LAT directions, with a maximal value of 4.1mm in LNG direction. Inter-fractional reproducibility showed better reliability, with difference in breathing levels in all fractions of 0.3mm on average. Based on tolerance limits corresponding to the 90% cumulative distribution level, gating window widths of 1mm, 2mm, and 5mm in the LAT, VRT, and LNG directions were considered an appropriate choice. In conclusion, despite the use of a dedicated spirometer at constant tidal volume, a non-negligible variability of the breast surface position has been reported during breath-holds. The real-time monitoring of breast surface using surface-guided optical technology is strongly recommended.

WASPE Sleep Deprivation, Paired with an Optical Surface Monitoring System, Can Provide Accurate Radiation Therapy to Pediatric Patients Without the Need for Sedation

This study aimed to explore the use of a protocol for sleep deprivation, combined with a surface optical monitoring system (OSMS)-guided radiation therapy (RT) to eliminate the need for pharmaceutical sedation of pediatric patients with cancer. The study subjects were 28 children aged 0 to 3 years undergoing intensity modulated RT. Parents used the WASPE method to keep the children awake from 6:00 am to 2:00 pm on each day of RT. To compare the potential effects of sleep deprivation versus sedation on treatment, the first 16 patients tested were alternately sleep deprived 1 day and given sedatives the next day for the duration of the RT. In all cases, RT was delivered under the real-time guidance of an OSMS. Twenty-seven of 28 children successfully completed 343 fractions of OSMS-guided RT. The 5-mm threshold for intrafractional motion was exceeded, and treatment was interrupted for patient repositioning during 13 sessions (sleep deprivation: 10 of 253 fractions; sedation: 3 of 90 fractions). Among the first 16 patients, no significant differences in inter- or intrafractional errors were noted on cone beam computed tomography scanning, except for an intrafractional error in the vertical direction for the 8th patient (P=.046). No significant difference in intrafractional errors measured by OSMS was found between the sleep-deprivation and sedation groups, except for 1 in the lateral direction for the 4th patient (P=.042) and 1 in the vertical direction for the 7th patient (P=.05). No differences were found in complete blood counts between the sleep-deprivation and sedation groups. In all, 36 of 52 parents surveyed (69%) preferred sleep deprivation, and only 3 parents (6%) preferred sedatives. The use of a sleep-deprivation protocol with OSMS guidance allows for accurate delivery of RT to children aged 0 to 3 years without the need for sedation and without jeopardizing target coverage. This approach may be useful for children who are resistant to or cannot tolerate sedatives.

Application of Optical Surface Monitoring System in Stereotactic Body Radiation Therapy for Liver Metastases Patient

<h3>Purpose/Objective(s)</h3> Stereotactic body radiotherapy (SBRT) in liver tumors has been a challenging treatment due to the diaphragm-induced motion. Optical surface monitoring system (OSMS) provides the functions of positioning and motion management, which has been widely used in recent years because it is non-ionizing, non-invasive and contactless. The purpose of this study was to explore the application of OSMS in liver metastasis patients. <h3>Materials/Methods</h3> 33 liver metastasis SBRT patients, who were treated between August 2019 to September 2021, were divided into two groups. 14 patients in Group A were aligned using skin marking (1 anterior and 2 laterals). 19 patients in Group B were aligned near to the skin marking at the initial step. Next, the ‘move couch' function on OSMS was applied if the patient's body rotations were less than 1 degrees according to the OSMS deltas value. The setup errors and setup time were recorded in both groups. <h3>Results</h3> Total of 88 and 106 CBCT images in group A and B were analyzed. The absolute setup errors for Groups A and B were (0.21 ± 0.15) cm, (0.37 ± 0.38) cm, (0.35 ± 0.33) cm, (0.8 ± 0.3), (1.2±0.5), (1.8 ± 0.7), and (0.04 ± 0.02) cm, (0.28 ± 0.13) cm, (0.03 ± 0.02) cm, (0.1 ± 0.2), (0.1 ± 0.2), and (0.3 ± 0.4) in vertical, longitudinal, lateral, rotation, pitch and roll directions respectively. Positioning accuracy in Group B is far superior to Group A especially in rotational directions. The difference was statistically significant (p<0.05). The average setup time was 2.8 minutes and 3.0 minutes for Group A and B. There was no significant difference in mean setup time. Setup time using OSMS was gradually improved as more experiences gained by the therapist. <h3>Conclusion</h3> The study has proven that OSMS is an effective and efficient tool for liver metastasis patients. It can increase the setup accuracy and reduce repeated setup. Continuous real time monitoring is of high clinical value for liver tumor motion management.

Geometric and Dosimetric Evaluation of Deep Learning-Based Automatic Delineation on CBCT-Synthesized CT and Planning CT for Breast Cancer Adaptive Radiotherapy: A Multi-Institutional Study.

PurposeWe developed a deep learning model to achieve automatic multitarget delineation on planning CT (pCT) and synthetic CT (sCT) images generated from cone-beam CT (CBCT) images. The geometric and dosimetric impact of the model was evaluated for breast cancer adaptive radiation therapy.MethodsWe retrospectively analyzed 1,127 patients treated with radiotherapy after breast-conserving surgery from two medical institutions. The CBCT images for patient setup acquired utilizing breath-hold guided by optical surface monitoring system were used to generate sCT with a generative adversarial network. Organs at risk (OARs), clinical target volume (CTV), and tumor bed (TB) were delineated automatically with a 3D U-Net model on pCT and sCT images. The geometric accuracy of the model was evaluated with metrics, including Dice similarity coefficient (DSC) and 95% Hausdorff distance (HD95). Dosimetric evaluation was performed by quick dose recalculation on sCT images relying on gamma analysis and dose-volume histogram (DVH) parameters. The relationship between ΔD95, ΔV95 and DSC-CTV was assessed to quantify the clinical impact of the geometric changes of CTV.ResultsThe ranges of DSC and HD95 were 0.73–0.97 and 2.22–9.36 mm for pCT, 0.63–0.95 and 2.30–19.57 mm for sCT from institution A, 0.70–0.97 and 2.10–11.43 mm for pCT from institution B, respectively. The quality of sCT was excellent with an average mean absolute error (MAE) of 71.58 ± 8.78 HU. The mean gamma pass rate (3%/3 mm criterion) was 91.46 ± 4.63%. DSC-CTV down to 0.65 accounted for a variation of more than 6% of V95 and 3 Gy of D95. DSC-CTV up to 0.80 accounted for a variation of less than 4% of V95 and 2 Gy of D95. The mean ΔD90/ΔD95 of CTV and TB were less than 2Gy/4Gy, 4Gy/5Gy for all the patients. The cardiac dose difference in left breast cancer cases was larger than that in right breast cancer cases.ConclusionsThe accurate multitarget delineation is achievable on pCT and sCT via deep learning. The results show that dose distribution needs to be considered to evaluate the clinical impact of geometric variations during breast cancer radiotherapy.

Deep Learning-Based Automatic Delineation of Target Volumes and Organs at Risk of Breast Cancer for On-Line Dosimetric Evaluation

In this study, we developed a deep learning model to achieve automatic multi-target delineation on planning CT (pCT) and daily Cone-Beam CT (CBCT). To improve the image quality of the CBCT for accurate target delineation and dose calculation, we introduce an unsupervised learning model to generate the artifact-free synthetic CT (sCT) from the CBCT. The geometric and dosimetric impact of the model on planning CT (pCT) and synthetic CT (sCT) was evaluated for breast cancer adaptive radiation therapy.We retrospectively analyzed 1127 patients treated with radiotherapy after breast-conserving surgery from two medical institutions. The CBCT for patient setup acquired utilizing breath-hold guided by optical surface monitoring system was used to generate sCT with the generative adversarial network. Organs at risk (OARs) and target volumes including tumor bed (TB) and clinical target volume (CTV) for breast cancer were delineated automatically with 3D U-Net model on pCT and sCT. The automatic delineation was compared with manually delineated contours to evaluate the performance with geometric metrics, including Dice similarity coefficient (DSC) and 95% Hausdorff Distance (HD95). The treatment plan which was transferred to the sCT from the pCT was generated with the same planning parameters as the original pCT-based plan. The dosimetric evaluation was performed by a quick dose recalculation on sCT relying on gamma analysis and the dose-volume histogram (DVH) parameters. The automatically delineating CTV on sCT which was rigidly registered to pCT was compared with manually delineating CTV on pCT to obtain DSC-CTV. The relationship between the ∆D95, ∆V95 and DSC-CTV was assessed to quantify the clinical impact of the geometric changes of CTV.The range of the DSC and HD95 were 0.73-0.97, 2.22-9.36mm for pCT, 0.63-0.95, 2.30-19.57mm for sCT from institution A, 0.70-0.97, 2.10-11.43mm for pCT from institution B respectively. The quality of sCT was excellent with an average mean absolute error (MAE) of 71.58 ± 8.78HU. The mean gamma pass rate (3%/3 mm criterion) by comparing the dose on sCT with that on original pCT was 91.46 ± 4.63%. DSC-CTV down to 0.65 accounted for a variation of more than 6% of V95 and 3Gy of D95. DSC-CTV up to 0.80 accounted for a variation of less than 4% of V95 and 2Gy of D95. The mean ∆V95 of CTV was less than 6%. The mean ∆V95 of TB was more than 8%. The mean ∆D90/∆D95 of CTV and TB were less than 2Gy/4Gy, 4Gy/5Gy for all the patients. The cardiac dose difference in left breast cancer was bigger than that in right breast cancer.This study demonstrates that highly accurate multi-target delineation and dose calculation are achievable using the daily CBCT image via deep learning. The results show that dose distribution needs to be considered to evaluate the clinical impact of geometric variations to decide whether to re-plan during breast cancer radiotherapy.

Innovative Non-Irradiating and Non-Invasive Per Fraction Control System in Radiotherapy: Surface-Guided Radiation Therapy Experience of Casablanca Cancer Center

Purpose: Evaluation of the added value of radiotherapy guided by the cutaneous&#x0D; &#x0D; surface in the positioning and monitoring of the radiotherapy&#x0D; &#x0D; Patients and Methods: This study included 21 consecutive patients treated with an&#x0D; &#x0D; accelerator dedicated to "True Beam®" stereotactic radiotherapy whose sessions were&#x0D; &#x0D; monitored by an Optical Surface Monitoring System: "OSMS®". Excluded from our&#x0D; &#x0D; study were treatments controlled exclusively by radiological imaging (IGRT).&#x0D; &#x0D; Positioning variabilities were compared between conventional imaging and skin&#x0D; &#x0D; surface infrared (OSMS) monitoring. Conventional imaging was in the form of&#x0D; &#x0D; standard radiography (KV) performed during the treatment session or three-&#x0D; &#x0D; dimensional by a series of Cone Beam computerized tomography (CBCT) scanned&#x0D; &#x0D; images made at the beginning and end of The total time of the session and&#x0D; &#x0D; the positioning variability’s in the 3 planes were&#x0D; &#x0D; 14&#x0D; &#x0D; Results: The results of our study show that the cutaneous surface monitoring allowed&#x0D; &#x0D; to obtain a faster alignment of the patient with an improvement in the overall time of&#x0D; &#x0D; the session with a mean at 32% [14.5-49.27%], likewise a sub-millimeter positioning&#x0D; &#x0D; quality for all locations with a median longitudinal distance of 0.02 cm [0-0.66], 01&#x0D; &#x0D; cm verticality [0-0.32] and laterality 0.02 cm [0-0.77] This benefit is significantly&#x0D; &#x0D; greater for cerebral and Head and neck’s localizations&#x0D; &#x0D; 21&#x0D; &#x0D; Conclusion: Optical Surface Monitoring System (OSMS®) is a non-invasive and non-&#x0D; &#x0D; irradiating means that allows reliable and fast&#x0D;

Performance assessment of two motion management systems for frameless stereotactic radiosurgery

Background/PurposeFrameless stereotactic radiosurgery (SRS) requires dedicated systems to monitor patient motion in order to avoid inaccurate radiation delivery due to involuntary shifts. The purpose of this study is to assess the accuracy and sensitivity of two distinct motion monitoring systems used for frameless SRS.MethodsA surface image-guided system known as optical surface monitoring system (OSMS), and a fiducial marker-based system known as high definition motion management (HDMM) as part of the latest Gamma Knife Icon® were compared. A 3D printer-based cranial motion phantom was developed to evaluate the accuracy and sensitivity of these two systems in terms of: (1) the capability to recognize predefined shifts up to 3 cm, and (2) the capability to recognize predefined speeds up to 3 cm/s. The performance of OSMS, in terms of different reference surfaces, was also evaluated.ResultsTranslational motion could be accurately detected by both systems, with an accuracy of 0.3 mm for displacement up to 1 cm, and 0.5 mm for larger displacements. The reference surface selection had an impact on OSMS performance, with flat surface resulting in less accuracy. HDMM was in general more sensitive when compared with OSMS in capturing the motion, due to its faster frame rate, but a delay in response was observed with faster speeds. Both systems were less sensitive in detection of superior-inferior motion when compared to lateral or vertical displacement directions.ConclusionTranslational motion can be accurately and sensitively detected by OSMS and HDMM real-time monitoring systems. However, performance variations were observed along different motion directions, as well as amongst the selection of reference images. Caution is needed when using real-time monitoring systems for frameless SRS treatment.

Comparison of the performance of two methods to determine set-up errors for DIBH patients with left sided breast cancer in radiotherapy

Objective To establish the basic procedures of the application of optical surface monitoring system (OSMS) in the deep inspiration breath hold (DIBH) radiotherapy for patients with left sided breast cancer and compare the performance of OSMS and cone-beam CT (CBCT) in the determination of the set-up errors of DIBH radiotherapy for patients with left sided breast cancer. Methods Twenty patients with left sided breast cancer received DIBH radiotherapy. Through the registration of CBCT images with the planning CT images, and the registration of OSMS radiography images with the outer contour of the body surface, translational set-up errors and rotational errors were determined along the lateral-medial (Rx), superior-inferior (Ry) and anterior-posterior (Rz) directions. Pearson correlation analysis was performed to evaluate the correlation of the set-up errors determined by two methods, and Bland-Altman plot analysis was used to assess the coincidence of these two methods. Results Two methods were positively correlated. The Rz volume was 0.84, 0.74 and 0.84 in the x, y and z directions, and 0.65, 0.41 and 0.54 in the Rx, Ry and Rz directions, respectively (all P<0.01). The 95%CI of agreement were within preset 5 mm tolerance (-0.37-0.42cm, -0.39-0.41cm, -0.29-0.49cm ) in x, y and z directions for two methods. The 95%CI of agreement were within preset 3 ° tolerance -2.9°-1.4°, -2.6°-1.4°, -2.4°-2.5°in Rx, Ry and Rz directions for two methods. The system errors of 20 patients with left sided breast cancer receiving DIBH radiotherapy were <0.18cm and the random errors were <0.24cm. Conclusions OSMS is equivalent to CBCT in the determination and stimulation of set-up errors for patients with left sided breast cancer receiving DIBH radiotherapy. The combination of CBCT and OSMS is a safe and reliable method. Key words: Optical surface monitoring system; Deep inspiration breath hold; Image registration

Patient motion tracking for non-isocentric and non-coplanar treatments via fixed frame-of-reference 3D camera.

PurposeAs C‐arm linac radiation therapy evolves toward faster, more efficient delivery, and more conformal dosimetry, treatments with increasingly complex couch motions are emerging. Monitoring the patient motion independently of the couch motion during non‐coplanar, non‐isocentric, or dynamic couch treatments is a key bottleneck to their clinical implementation. The goal of this study is to develop a prototype real‐time monitoring system for unconventional beam trajectories to ensure a safe and accurate treatment delivery.MethodsAn in‐house algorithm was developed for tracking using a couch‐mounted three‐dimensional (3D) depth camera. The accuracy of patient motion detection on the couch was tested on a 3D printed phantom created from the body surface contour exported from the treatment planning system. The technique was evaluated against a commercial optical surface monitoring system with known phantom displacements of 3, 5, and 7 mm in lateral, longitudinal, and vertical directions by placing a head phantom on a dynamic platform on the treatment couch. The stability of the monitoring system was evaluated during dynamic couch trajectories, at speeds between 10.6 and 65 cm/min.ResultsThe proposed monitoring system agreed with the ceiling mounted optical surface monitoring system in longitudinal, lateral, and vertical directions within 0.5 mm. The uncertainty caused by couch vibration increased with couch speed but remained sub‐millimeter for speeds up to 32 cm/min. For couch speeds of 10.6, 32.2, and 65 cm/min, the uncertainty ranges were 0.27– 0.73 mm, 0.15–0.87 mm, and 0.28–1.29 mm, respectively.ConclusionBy mounting a 3D camera in the same frame‐of‐reference as the patient and eliminating dead spots, this proof of concept demonstrates real‐time patient monitoring during couch motion. For treatments with non‐coplanar beams, multiple isocenters, or dynamic couch motion, this provides additional safety without additional radiation dose and avoids some of the complexity and limitations of room mounted systems.

Efficient quality assurance method with automated data acquisition of a single phantom setup to determine radiation and imaging isocenter congruence.

We developed a quality assurance (QA) method to determine the isocenter congruence of Optical Surface Monitoring System (OSMS, Varian, CA, USA), kilovoltage (kV), and megavoltage (MV) imaging, and the radiation isocenter using a single setup of the OSMS phantom for frameless Stereotactic Radiosurgery (SRS) treatment. After aligning the phantom to the OSMS isocenter, a cone‐beam computed tomography (CBCT) of the phantom was acquired and registered to a computed tomography (CT) scan of the phantom to determine the CBCT isocenter. Without moving the phantom, MV and kV images were simultaneously acquired at four gantry angles to localize MV and kV isocenters. Then, Winston‐Lutz (W‐L) test images of the central BB in the phantom were acquired to analyze the radiation isocenter. The gantry and couch were automatically controlled using the TrueBeam Developer Mode during MV, kV, and W‐L image acquisition. All the images were acquired weekly for 17 weeks to track the congruence of all the imaging modalities' isocenter in six‐dimensional (6D) translations and rotations, and the radiation isocenter in three‐dimensional (3D) translations. The shifts of isocenters of all imaging modalities and the radiation isocenter from the OSMS isocenter were within 0.2 mm and 0.2° on average over 17 weeks. The maximum discrepancy between OSMS and other imaging modalities or radiation isocenters was 0.8 mm and 0.3°. However, systematic shifts of radiation isocenter anteriorly and laterally relative to the OSMS isocenter were observed. The measured discrepancies were consistent from week‐to‐week except for two weeks when the isocenter discrepancies of 0.8 mm were noted due to drifts of the OSMS isocenter. Once recalibration was performed on OSMS, the discrepancy was reduced to 0.3 mm and 0.2°.By performing the proposed QA on a weekly basis, the isocenter congruencies of multiple imaging systems and radiation isocenter were validated for a linear accelerator.

Deep Inspiration Breath-Hold Irradiation for Left Side Breast Cancer Using a New Combination of Respiration Monitoring Device and Optical Body Surface Monitoring System

Deep Inspiration Breath-Hold Irradiation for Left Side Breast Cancer Using a New Combination of Respiration Monitoring Device and Optical Body Surface Monitoring System

Intra-Fraction Motion Analysis for Frameless Linac-Based Stereotactic Radiosurgery with Three-Dimension (3D) Optical Surface Imaging for Intra-Fractional Motion Management

There has been a rapid increase in the use of frameless SRS in place of the frame-based SRS for treatment of brain metastases (BM). Compared to the frame-based SRS, intra-fraction motion management is a major challenge for the frameless SRS. With advanced immobilization and patient monitoring technologies, intra-fraction motion can be reduced. The purpose of this study is to analyze intra-fraction motion with LINAC-based SRS using a frameless radiosurgery platform that uses an integrated 3D optical surface monitoring system for intra-fraction motion management. This retrospective study includes 97 LINAC-SRS treatments delivered to 60 patients of BM with an integrated 3D surface imaging software for intra-fraction monitoring. Every treatment was delivered with a 6MV FFF beam at a dose-rate of 1400MU/min. Each treatment had at least 3 non-coplanar arcs with a minimum of 3 couch rotations. The patients were immobilized using an open-faced rigid SRS-thermoplastic mask with an opening encompassing the eyes, nose, and part of their forehead. Each patient was first aligned using a high-quality cone-beam CT (CBCT) with 1mm slice thickness and positioned using a 6 degrees of freedom couch. The patient’s face was monitored during treatment delivery through the surface monitoring system. During delivery, beam holds occurred if patient motion exceeded pre-defined tolerance (1mm translation/1° rotation) for > 5 seconds. An additional CBCT was performed following the delivering of two arcs to assess for any intra-fraction motion. Each CBCT was then registered to the planning CT using the automated intensity-based registration algorithm, followed by confirmation with a manual check. The intra-fraction shifts (RL, AP, and SI) and rotation (yaw, roll, and pitch) data were retrospectively recorded and analyzed. The total magnitude of the patient intra-fraction motion for all ninety-seven SRS treatments as recorded through shifts were 0.4 mm (mean) ± 0.3 mm (stv). Translational shifts were 0.0±0.3 mm in RL, 0.0±0.3 mm in AP, 0.0±0.3 mm in SI, while the rotational variations were 0.0±0.4° in yaw, 0.0±0.2° in roll, and 0.0±0.2° in pitch. In total, 93.8%(n=91/97) delivered treatments had intra-fraction motion that was ≤1mm and ≤1 degree. Minimal intra-fraction motion was observed during frameless-based LINAC-SRS treatments when using an integrated 3D surface image tracking; Only 6% percent of treatments experienced motion that was >1mm or >1 degree. A planning target margin of ≤1 mm may be considered adequate during the planning process to account for intra-fraction motion in the majority of all cases.

Assessment of Voluntary Deep Inspiration Breath-holding Technique Using Optical Surface Monitoring System for Breast Radiotherapy: A Prospective Phase 2 Study of 20 Cases

Assessment of Voluntary Deep Inspiration Breath-holding Technique Using Optical Surface Monitoring System for Breast Radiotherapy: A Prospective Phase 2 Study of 20 Cases

Optical surface guidance for submillimeter monitoring of patient position during frameless stereotactic radiotherapy.

PurposeTo evaluate the accuracy of monitoring intrafraction motion during stereotactic radiotherapy with the optical surface monitoring system. Prior studies showing a false increase in the magnitude of translational offsets at non‐coplanar couch positions prompted the vendor to implement software changes. This study evaluated two software improvements intended to address false offsets.MethodsThe vendor implemented two software improvements: a volumetric (ACO) rather than planar calibration and, approximately 6 months later, an improved calibration workflow (CIB) designed to better compensate for thermal drift. Offsets relative to the reference position, obtained at table angle 0 following image‐guided setup, were recorded before beam‐on at each table position and at the end of treatment the table returned to 0° for patients receiving SRT.ResultsPrior to ACO, between ACO and CIB, and after CIB, 223, 155, and 436 fractions were observed respectively. The median magnitude of translational offsets at the end of treatment was similar for all three intervals: 0.29, 0.33, and 0.27 mm. Prior to ACO, the offset magnitude for non‐zero table positions had a median of 0.79 mm and was found to increase with increasing distance from isocenter to the anterior patient surface. After ACO, the median magnitude was 0.74 mm, but the dependence on surface‐to‐isocenter distance was eliminated. After CIB, the median magnitude for non‐zero table positions was reduced to 0.57 mm.ConclusionOngoing improvements in software and calibration procedures have decreased reporting of false offsets at non‐zero table angles. However, the median magnitude for non‐zero table angles is larger than that observed at the end of treatment, indicating that accuracy remains better when the table is not rotated.

A novel-integrated quality assurance phantom for radiographic and nonradiographic radiotherapy localization and positioning systems.

Various localization and positioning systems utilizing radiographic or nonradiographic methods have been developed to improve the accuracy of radiation treatment. Each quality assurance (QA) procedure requires its own phantom and is independent from each other, so the deviation between each system is unavailable. The purpose of this work is to develop and evaluate a single-integrated QA phantom for different localization and positioning systems. The integrated phantom was designed in three-dimensional (3D) CAD software and 3D printed. The phantom was designed with laser alignment marks, a raised letter "S" on the anterior surface for optical surface monitoring system registration, a core for radiofrequency (RF) tracking system alignment, eight internal fiducials for image alignment, and an isocentric bearing for Winston-Lutz test. Tilt legs and rotational stage were designed for rotational verification of optical surface mapping system and RF tracking system, respectively. The phantom was scanned using a CT scanner and a QA plan was created. This prototype phantom was evaluated against established QA techniques. The QA result between the proposed procedure and established QA technique are 1.12 ± 0.31 and 1.14 ± 0.31 mm, respectively, for RF tracking system and 0.18 ± 0.06 and 0.18 ± 0.05 mm for Winston-Lutz test. There is no significant difference for the QA results between the established QA and proposed procedure (P > 0.05, t test). The accuracy of rotational verification for surface mapping system and RF tracking system are less than 0.5 and 1° compared the predefined value. The isocenter deviation of each location system is around l mm. We have designed and evaluated a novel-integrated phantom for radiographic and nonradiographic localization and positioning systems for radiotherapy. With this phantom, we will reduce the variation in measurements and simplify the QA procedures.

OC-0194: Evaluation of an optical surface monitoring system for intrafractional movement during SABR

OC-0194: Evaluation of an optical surface monitoring system for intrafractional movement during SABR

A Strategy to Generate a Reference Surface for Optical Surface Monitoring System for Volumetric Modulated Arc Therapy

Optical Surface Monitoring System (OSMS) is being utilized in radiation therapy (RT) for patient setup, second check verification for localization, beam gating for respiratory motion, and prevention of intra-fractional dose delivery beyond a threshold displacement of the patient’s body surface to ensure precise RT delivery. The optimal application of OSMS is affected by the region of surface being selected and surface characteristics such as shape, location, area, and surface materials. In this study, a strategy to select an optimal reference surface was developed for stereotactic body radiation therapy with RapidArc delivery technique. A mannequin body surface was used for this study. Three priority variables were selected for optimization, including the surface location, area of surface, and materials on the surface. Mathematically, the reference surface selection function is represented by S (L, A, M, s(x, y, z), t). In this formula, L is location of RT isocenter, A is the avoided area, M is surface material, s(x, y, z) is the unit area variable, and t represents time. A total of five surface regions were analyzed. The surface locations of interest from superior to inferior were 1) vertex to neck, 2) between neck and nipple, 3) between nipple and umbilicus, 4) pelvis and 5) below pelvis to feet. Materials used included mannequin body surface, towel, pillow, paper, and plastic sheet from the BodyFIX (Elekta) immobilization system. The study also compared the static and motion status of the surface. An optimal empirical reference surface was attained so that the RapidArc RT delivery was functioning appropriately. In this simulation, the most sensitive gantry angle affected in selecting a reference surface is 30-60 and 330-300 degree. And the reference surface area in the axial regions is best to be avoided as about a 10 cm width strip along the 45 degree direction could not be visualized by the camera. The maximum benefit of OSMS to ensure accurate RT delivery can be achieved by selecting the optimal sensitive area for clinical application. Further study is needed to find an optimal quantitative function to auto process the surface selection procedure. Clinically, more information needs to be collected from other treatment techniques at different sensitivity requirements.