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Six axes robots employed at the Heidelberg Ion beam therapy centre for patient positioning. The laser tracker for monitoring the movements of the couch is located under the false floor beneath the steel grid. The retroreflectors can be seen at the bottom side of the couch (see also small picture on the right).
Source publication
Background
In this study we investigate the accuracy of industrial six axes robots employed for patient positioning at the Heidelberg Ion Beam Therapy Center.
Methods
In total 1018 patient setups were monitored with a laser tracker and subsequently analyzed. The measurements were performed in the two rooms with a fixed horizontal beam line. Both,...
Contexts in source publication
Context 1
... the ion beam therapy center in Heidelberg Siemens Medical Solutions adapted floor mounted KUKA robots (KR 240 L210 MED from KUKA, Augsburg, Germany) to carry the treatment couch (Figures 1 and 2). The two robots investigated are installed in the treatment rooms with fixed horizontal beam lines. ...Context 2
... order to monitor the movements of the couch we used a laser tracker -an optical measuring device, which is able to measure the position of a retroreflector (target) with a precision of typically a few tens of micrometers ( [11]). The laser tracker was mounted under the false floor beneath the isocenter, the targets were located on the bottom side of the couch (Figure 1). A hole in the tiles of the floor was kept open above the laser tracker. ...Similar publications
Background:
The role of postmastectomy radiation therapy (PMRT) after neoadjuvant chemotherapy (NAC) and mastectomy is unclear, especially in patients that have post-treatment tumor negative axillary nodes (ypN0).
Methods:
The National Cancer Data Base was used to identify women that had PMRT after NAC and mastectomy for clinically node positive...
In vivo Cherenkov video imaging visualizes the process of external beam radiotherapy. Patient positioning, treatment verification, quality control, superficial dose and skin reaction estimation were explored for this technique, termed Cherenkoscopy.
Citations
... For both WFs (Fig. 2), the patient was initially moved with the 6 degrees of freedom robotic treatment table 20 from a step-on position to so-called reference point in our WF (isocenter) at a gantry angle of 0°using the handheld control. The skin marks and the IRL are used for patient prepositioning in the WF with skin marks. ...
Purpose
: Surface guided Radiotherapy (SGRT) has been intensively investigated to ensure correct patient positioning during a radiotherapy course. Although the implementation is well defined for photon beam facilities, only a few analyses have been published for ion beam therapy centers. To investigate the accuracy, reliability and efficiency of SGRT used in ion beam treatments against the conventional skin marks, a retrospective study of a unique SGRT installation in an ion gantry treatment room was conducted, where the environment is quite different to conventional Radiotherapy.
Methods and Materials
: Thirty-two patients, divided into three cohorts: pelvis, limb, and chest/spine tumors, and treated with ion beams. Two patient positioning workflows based on 300 fractions were compared: workflow with skin marks, and workflow with SGRT. Position verification was followed by planar kV imaging. After image matching, six-degree corrections were recorded to assess inter-fraction positioning errors. Additionally, the time required for patient positioning, image matching, and the number of repeated kV imaging were also gathered.
Results
: SGRT decreased the translational magnitude shifts significantly (p < 0.05) by 0.5±1.4 mm for pelvis, and 1.9±0.5 mm for limb, whereas for chest/spine increased by 0.7±0.3 mm. Rotational corrections were predominantly lowered with SGRT for all cohorts with significant differences in pitch for pelvis (p = 0.002), and chest/spine (p = 0.009). The patient positioning time reduced by 18 %, 9 %, and 15 % for pelvis, limb, and chest/spine, respectively, compared to skin marks. By using SGRT, 53 % of all studied patients had faster positioning time, and 87.5 % had faster matching time. Re-positioning and consequent re-imaging were dropped from about 7 % to 2 % with statistically significant difference of 0.042.
Conclusions
: The quality of patient positioning prior to ion beam treatments has been optimized by using SGRT without additional imaging dose. SGRT clearly reduced inefficiencies in the patient positioning WF.
... Some others have adopted laser trackers and infrared trackers to verify the movement performance of the 6-DOF robotic couch [13][14] [15][16]. However, no studies have developed the real-time motion management (includes the accuracy, safety, synchronization, and trajectory tracking) for PPS. ...
Background: In proton therapy, robotic couch was used for patient positioning to achieve high precision in cancer treatment. However, no studies have focused on the real-time motion management system (MMS) for the robotic couch. This study was to develop the MMS and verify its feasibility.
Methods: A real-time MMS was set up with a robotic couch, an NDI Vega optical tracking system, a Special Measurement Tool (SMT) and the developed software. A Leica laser tracker was adopted to verify the accuracy of the tests in this study. The stability and accuracy of the SMT in NDI Vega system were verified to guarantee the reliability of the results. The coordinate transformation was used to unify the measurement. 83 points inside the treatment volume were applied to verify the accuracy of the MMS, with the comparison of results measured by the laser tracker. The synchronism of the SMT in the MMS and Patient Positioning System (PPS) based on the reciprocating motion along axis z was tested to obtain the maximum time delay. Trajectory tracking was performed with different payloads on the couch top.
Results: The Means and Standard Deviation (SD) of the stability of the SMT in NDI tracking system on the axis x, y, z, and Rx, Ry, Rz were 0.005 ± 0.004 mm, 0.013 ± 0.005 mm, 0.014 ± 0.005 mm, 0.010 ± 0.003º, 0.013 ± 0.005º, 0.008 ± 0.007º, respectively. For the MMS, the means ± SD along axis x, y, z were 0.24 ± 0.09 mm (0.12 ± 0.03 mm With Laser Tracker (WLT)), 0.31 ± 0.12 mm (0.10 ± 0.03 mm WLT), 0.18 ± 0.06 mm (0.14 ± 0.05 mm WLT), respectively. The max time delay was about 110 ms, with a 60 s of motion tracking. Trajectories tracking showed the real-time graphical traces of the SMT in NDI Vega and Room Coordinate system, and the combined curves by using the coordinate transformation.
Conclusions: A real-time MMS was developed and verified with the accuracy of submillimeter in this study. The results demonstrated the feasibility of potential applications based on real-time motion capturing and monitoring.
... The daily image is used to compare the position of the patient with the CT recorded for the treatment plan by checking, for example, the bony structure position. With this information, the patient can be re-aligned with a precision better than 1 mm [77] compared to the absolute coordinates system of the treatment room, and therefore to the beam axis. ...
In ion-beam therapy, high precision measurements are essential for having robust basic data to deliver the prescribed treatment to the patient. In this study, MIMOSA-28 pixel sensors were used as a tracker system for different medical applications. Several hardware and software improvements were implemented leading to a spatial track resolution < 10 μm. The experiments were conducted with success in different medical and research facilities. In this work, beam profiles were measured along the beam axis and the width of the beam along the axis could be calculated with a transportation code based on multiple Coulomb scattering. Moreover, an online beam monitoring was developed in order to have fast information about the beam profile. In another study, the fluence perturbation of 12C ion beams due to small fiducial markers was investigated. After reconstruction and extrapolation of single track, a 3D fluence distribution could be performed and the maximum perturbation and its position along the beam axis could be quantified. In this work, the measured cold spot varied between less than 3% up to 9.2% for a defined marker and a defined primary energy beam.
... Additionally, force sensors in the robotic couch detect the weight and location of center of gravity of the load on the couch surface since mechanical sag of the carbon fiber couch top must be accounted for to achieve mechanical isocentricity. 3 As in photon radiotherapy, x-ray image guidance systems are used for pretreatment patient localization. Patients are typically setup with the couch longitudinal axis perpendicular to the proton gantry axis of rotation, as shown in Fig. 1 (Couch angle = 270°). ...
Background:
A proton therapy system with 190° gantries uses robotic couch rotations to change the treatment beam laterality. Couch rotations are typically validated clinically with post-rotation radiographic imaging.
Aims:
This study assesses the specificity and sensitivity of a commercial 3D surface imaging system, AlignRT (Vision RT, London UK) for validating couch rotations.
Materials & methods:
In clinical operation, a reference surface image of the patient is acquired after radiographic setup with couch at 270°, perpendicular to the gantry axis of rotation. The couch is then rotated ±90° to a typical treatment angle, and AlignRT reports a 3D displacement vector. Patient motion, changes in patient surface, non-coincidence between AlignRT and couch isocenter, and mechanical couch run-out all contribute to the 3D vector magnitude. To assess AlignRT sensitivity in detecting couch run-out, volunteers were positioned orthogonal to the proton gantry and reference surface images were captured without x-ray localization. Subjects were repeatedly rotated ±90⁰ to typical treatment angles and displacement vectors were recorded. Additionally, measurements were performed in which intentional translations of 2, 4, 6, and 8 mm were combined with the intended isocentric rotations. Data sets were collected using a phantom; subjects with a thoracic isocenter and no immobilization; and subjects with a cranial isocenter and thermoplastic immobilization. A total of 300 rotations were measured.
Results:
During isocentric rotations, the mean AlignRT displacement vectors for the phantom, immobilized, and non-immobilized volunteers were 0.1 ± 0.1 mm, 0.8 ± 0.1 mm, and 1.1 ± 0.2 mm respectively. 95% of the AlignRT measurements for the immobilized and non-immobilized subjects were within 1 mm and 2 mm of the actual displacement respectively.
Discussion:
After characterizing the accuracy using phantoms and volunteers, we have shown that a three-pod surface imaging system can be used to identify gross non-isocentric patient rotations. Significant positional deviations, either due to improper couch rotation or patient motion, should be followed by radiographic imaging and repositioning.
Conculsion:
AlignRT can be used to verify patient positioning following couch rotations that are applied after the initial x-ray guided patient setup. Using a three-pod AlignRt system, positional deviations exceeding 4 mm were flagged with sensitivity and specificity of 90% and 100% respectively.
... An additional translation is offered by the linear axis which facilitates the movement of the patient towards the treatment head, at reduced air gap. The imaging system mounted directly on the couch permits an on-line imaging registration for the fine tuning of the patient positioning [116]. The non-isocentric treatment technique is routinely used at MedAustron and it has to be carefully performed as the PAS accuracy may Figure 3.2: picture of the ceiling-mounted robot used at MedAustron . ...
... Une translation supplémentaire est disponible grâceà l'axe linéaire qui permet de déplacer le patient vers la tête de traitement, avec un débattement de robot réduit. Le système d'imagerie monté sur la table permet de corriger directement et avec finesse l'alignement du patient [116]. La technique de traitement non isocentrique est couramment utiliséè a MedAustron et elle doitêtre exécutée avec soin car la précision du PPS peut etre réduite en s'éloignant de l'isocentre. ...
The goal of this PhD is to develop and validate an independent dose calculation method in order to support the intense commissioning work of a Light Ion Beam Therapy (LIBT) facility, and to validate the Treatment Planning System (TPS) dose calculation. The work focuses on proton therapy treatments and is held as a collaboration between the CREATIS laboratory (Lyon, France) and the MedAustron - Vienna - Austria Ion Therapy Center (Wiener Neustadt, Austria). At MedAustron - Vienna - Austria, in order to exploit a sharp lateral penumbra for the proton beam as well as to improve the accuracy of the TPS dose calculation algorithms, the air gap between the treatment head window and the patient is reduced by moving the patient towards the treatment head. Therefore, non-isocentric treatments have to be accurately taken into consideration during modeling as well as validation phase as moving the target away from the room isocenter may lead to reduced treatment accuracy. In this study, the parametrization of the proton pencil beam follows the recommendations provided in Grevillot et al. (2011), but including a full nozzle description. Special care is taken to model the pencil beam properties in non-isocentric conditions, including the use of a Range Shifter (RaShi). The characterization of the pencil beam is based solely on fluence profiles measured in air and depth dose profile acquired in water. In addition, the presented model is calibrated in absolute dose based on a newly formalism in dose-area-product presented in Palmans and Vatnitsky (2016). Eventually, a detailed validation is performed in water, for three-dimensional regular-shaped dose distributions. Several parameters commonly exploited in proton dosimetry such as range, distal penumbra, modulation, field sizes and lateral penumbra for proton dosimetry are evaluated for validation purposes. The pencil beam optics model reached an accuracy within the clinical requirement of 1mm/10% and it is not affected by the complexity of non-isocentric treatments and the use of a RaShi. Ranges are reproduced within 0.2 and 0.35 mm (max deviation) without and with range shifter, respectively. The dose difference in reference conditions is within 0.5%. The 3D dose delivery validation in water was within 1.2% at maximum. The agreement of distal and longitudinal parameters is mostly better than 1 mm. The obtained results will be used as a reference for the future clinical implementation of the MedAustron - Vienna - Austria independent dose calculation system. As an example of the potential clinical outcome of the presented work, the patient specific quality assurance measurements performed in water have been successfully reproduced within the clinical requirement of 5% accuracy for a few patients.
... Conventional couches only correct for translational errors. Proton therapy PPS is designed to have a higher degree of positioning accuracy and reproducibility by mounting the table top on a high precision robotic arm (Nairz et al. 2013). Since proton dose distributions have sharp dose gradients adjacent to the target volume, the delivered dose is more sensitive to errors in daily patient positioning than photon treatments. ...
Modern radiotherapy is a highly complex process utilizing the accurate application of computerized treatment planning coupled with particle acceleration and photon emitting systems providing precisely positioned and accurate beam delivery. Treatment planning has been transformed over the past couple decades, enhanced by advanced imaging for target and normal structure definition, previously impossible radiation dose sculpting, and highly accurate 3-dimensional (3D) dose calculations that allow the minimization of normal tissue dose while conformally treating the tumor. The radiotherapy community has aggressively employed these normal tissue sparing techniques for pediatric cancer patients as will be shown in this chapter. Therefore, (Marks et al. 2010) late effects outcomes reported in the literature for patients treated decades ago should not be relied upon for formulating expectations of such effects in currently treated patients.
... Commissioning was performed for 3 • pitch and 3 • roll to allow for patient setup correction. In order to assure high positioning accuracy a weight dependent calibration of the system is commonly performed in other facilities [14]. To be independent of the payload, a different solution was implemented at MedAustron, which is based on a floor-mounted photogrammetric tracking camera and reflectors on the bottom side of the table-top. ...
... In total 1020 different positions were measured. position accuracy was found to be comparable to other centers [14] although the maximum possible treatment volume itself is bigger than in other centers and amounts to about 205 l. Independent of the payload, the mean deviation in 3D was found to be smaller than 0.5 mm during commissioning [15,16]. ...
The ratio of patients who need a treatment adaptation due to anatomical variations at least once during the treatment course is significantly higher in light ion beam therapy (LIBT) than in photon therapy. The ballistic behaviour of ion beams makes them more sensitive to changes. Hence, the delivery of LIBT has always been supported by state of art image guidance. On the contrary CBCT technology was adapted for LIBT quite late. Adaptive concepts are being implemented more frequently in photon therapy and also efficient workflows are needed for LIBT. The MedAustron Ion Beam Therapy Centre was designed to allow the clinical implementation of adaptive image-guided concepts. The aim of this paper is to describe the current status and the potential future use of the technology installed at MedAustron. Specifically addressed is the beam delivery system, the patient alignment system, the treatment planning system as well as the Record & Verify system. Finally, an outlook is given on how high quality X-ray imaging, MR image guidance, fast and automated treatment planning as well as in vivo range verification methods could be integrated.
... Our results demonstrate that residual repositioning errors may, in some cases, lead to a significant perturbation of the delivered dose in scanned-beam carbon ion and proton therapy for skull base tumors (by up to 10 pp for carbon ions and up to 12 pp in proton plans, in individual cases), which cannot be completely dealt with by planning target expansion alone. Only rigid setup errors were simulated, as they represent the predominant source of targeting uncertainty in skull base treatments, with magnitudes (1-2 mm) consistent with the precision reported for modern non-invasive cranial immobilization devices and patient positioning systems, in terms of residual setup errors as well as intrafraction motion [2,[26][27][28][29][30]. No rotational errors were simulated, as in comparison to translational displacements, angular deviations cause smaller effects as established in the preliminary work for this study [31] and also observed for other indications [8]. ...
Background
It is expected that physical dose deposition properties render charged particle dose distributions sensitive to targeting uncertainties. Purpose of this work was to investigate the robustness of scanned-beam particle therapy plans against setup errors for different optimization modalities, beam setups and ion species.Material and methodsFor 15 patients with skull base tumors, localized in regions of severe tissue density heterogeneity, scanned lateral-opposed-beam treatment plans were prepared with the treatment planning system TRiP98, employing different optimization settings (single- and multiple-field modulation) and ion species (carbon ions and protons). For 10 of the patients, additional plans were prepared with individually selected beam setups, aiming at avoiding severe tissue heterogeneities. Subsequently, multiple rigid positioning errors of magnitude 1¿2 mm (i.e. within planning target expansion) were simulated by introducing a shift of the irradiation fields with respect to the computed tomography (CT) data and recomputing the plans.ResultsIn presence of shifts, in carbon ion plans using a lateral-opposed beam setup and fulfilling clinical healthy tissue dose constraints, the median reduction in CTV V95% was up to 0.7 percentage points (pp) and 3.5 pp, for shifts of magnitude 1 mm and 2 mm respectively, however, in individual cases, the reduction reached 5.1 pp and 9.7 pp. In the corresponding proton plans similar median CTV V95% reductions of up to 0.9 pp (1 mm error) and 3.4 pp (2 mm error) were observed, with respective individual-case reductions of at most 3.2 pp and 11.7 pp. Unconstrained plans offered slightly higher coverage values, while no relevant differences were observed between different field modulation methods. Individually selected beam setups had a visible dosimetric advantage over lateral-opposed beams, for both particle species. While carbons provided more conformal plans and generally more advantageous absolute dose values, in presence of setup errors, protons showed greater dosimetric stability, in most of the investigated scenarios.Conclusion
Residual patient setup errors may lead to substantial dose perturbation in scanned-beam particle therapy of skull base tumors, which cannot be dealt with by planning target expansion alone. Choice of irradiation directions avoiding extreme density heterogeneities can improve plan stability against such delivery-time uncertainties.
... Moreover, respiration-induced organ motion is tackled through specific mitigation strategies relying on dedicated planning [9] as well as irradiation techniques [10e12] to synchronize beam delivery with the observed patient motion. This is the case of modern particle therapy facilities such as the Heidelberg Ion Therapy Center [13,14], the Paul Scherrer Institute (gantry #2) [15,16], the National Institute of Radiological Sciences [17] and Centro Nazionale di Adroterapia Oncologica [18], implementing in-room imaging solutions and robotic couches for automated patient setup. When anatomical bony features are available, setup is verified by means of image registration between multiple planar kV projections with the planning computed tomography (CT) volume, relying on a 2dimensional (2D) to three-dimensional technique. ...
In this contribution we describe the implementation of a novel solution for image guided particle therapy, designed to ensure the maximal accuracy in patient setup. The presented system is installed in the central treatment room at Centro Nazionale di Adroterapia Oncologica (CNAO, Italy), featuring two fixed beam lines (horizontal and vertical) for proton and carbon ion therapy. Treatment geometry verification is based on robotic in-room imaging acquisitions, allowing for 2D/3D registration from double planar kV-images or 3D/3D alignment from cone beam image reconstruction. The calculated six degrees-of-freedom correction vector is transferred to the robotic patient positioning system, thus yielding automated setup error compensation. Sub-millimetre scale residual errors were measured in absolute positioning of rigid phantoms, in agreement with optical- and laser-based assessment. Sub-millimetre and sub-degree positioning accuracy was achieved when simulating setup errors with anthropomorphic head, thorax and pelvis phantoms. The in-house design and development allowed a high level of system customization, capable of replicating the clinical performance of commercially available products, as reported with preliminary clinical results in 10 patients.
... In the treatment of cranial lesions, the major source of geometrical deviation is the relative motion of skin and bone anatomy, significantly affecting the repositioning accuracy, as assessed for commonly used immobilization devices [4][5][6]. Clinical protocols featuring image guidance and six degrees-of-freedom (DOF) robotic patient alignment [7][8][9] break down systematic geometrical errors to the millimeter scale. In addition the particle range control in typical head&neck tissues is reported to be around 1 mm for both protons [10,11] and carbon ions [12], representing a further source of systematic error throughout a fractionated treatment [2]. ...
Purpose:
To investigate dose distribution variations due to setup errors and range uncertainties in image-guided carbon ion radiotherapy of head chordoma.
Materials and methods:
Ten treatment plans were retrospectively tested with TRiP98 against ±1.0 mm and ±1.0° setup errors, as observed in clinical routine, and 2.6% range uncertainty when 2mm CTV-to-PTV margins were applied. Single-fraction simulations were compared with the total treatment dose in terms of DVH bands, conformity and inhomogeneity. The contribution of image processing artifacts on reported results was also discussed, as a function of the imaging dataset resolution.
Results:
Results showed that safety margins grant the conformal target coverage in presence of setup errors with D95(CTV) variations below 10% in 7 patients out of 10. Instead, the inclusion of range uncertainty yielded to appreciable dose degradation, reporting larger effects for CTV and dose conformity, whereas reduced impact is found on the organ-at-risk. The fractionation scheme positively affects dose conformity and inhomogeneity; conversely its influence on DVH bands is strongly related to the patient anatomy.
Conclusion:
Besides safety margins, setup and range uncertainties lead to non-negligible combined contribution. Systematical treatment plan robustness assessment against expected uncertainties is thus encouraged, selecting beam settings and fractionation schemes where homogeneity is preserved.
