Enabling non-isocentric dynamic trajectory radiotherapy by integration of dynamic table translations

Guyer, Gian; Mueller, Silvan; Koechli, Carole; Frei, D.; Volken, W.; Bertholet, Jenny; Mackeprang, Paul-Henry; Loebner, Hannes A; Aebersold, Daniel M.; Manser, Peter; Fix, M.K.

doi:10.1088/1361-6560/ac840d

Cited by 9 publications

(7 citation statements)

References 60 publications

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“…Additional degrees of freedom could be explored with conventional linacs, for example, by enabling dynamic table rotation 6–9,32,34,35 or translations 24 . However, these techniques are more complex than colli‐DTRT or NC‐VMAT and have so far either used geometric heuristics for path determination, 8,9,24,34,35 or they have not been shown to be deliverable 6,7,32 …”

Section: Discussionmentioning

confidence: 99%

“…The final set of arc candidates are then considered as dynamic arcs and subjected to intensity modulation optimization using a hybrid-direct aperture optimization (DAO) combining column generation and simulated annealing. 23,24 Final dose calculation of the optimized apertures is performed in SMCP using VMC++ to simulate the plan-specific part of the treatment head including the secondary collimator jaws and MLC and to calculate dose deposition in the patient, accounting for the continuous motion of all dynamic components between the discrete control points (CP). Finally, monitor unit (MU) weights are re-optimized using a L-BFGS algorithm.…”

Section: Dao and Final Dose Calculationmentioning

confidence: 99%

“…Additional degrees of freedom could be explored with conventional linacs, for example, by enabling dynamic table rotation [6][7][8][9]32,34,35 or translations. 24 However,these techniques are more complex than colli-DTRT or NC-VMAT and have so far either used geometric heuristics for path determination, 8,9,24,34,35 or they have not been shown to be deliverable. 6,7,32 In addition to mechanical degrees of freedom (dynamic table rotation or translation, dynamic collimator rotation), electrons of different energies are also available on conventional linacs.…”

Section: F I G U R Ementioning

confidence: 99%

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Dosimetrically motivated beam‐angle optimization for non‐coplanar arc radiotherapy with and without dynamic collimator rotation

Bertholet,

Zhu,

Guyer

et al. 2023

Medical Physics

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BackgroundNon‐coplanar techniques have shown to improve the achievable dose distribution compared to standard coplanar techniques for multiple treatment sites but finding optimal beam directions is challenging. Dynamic collimator trajectory radiotherapy (colli‐DTRT) is a new intensity modulated radiotherapy technique that uses non‐coplanar partial arcs and dynamic collimator rotation.PurposeTo solve the beam angle optimization (BAO) problem for colli‐DTRT and non‐coplanar VMAT (NC‐VMAT) by determining the table‐angle and the gantry‐angle ranges of the partial arcs through iterative 4π fluence map optimization (FMO) and beam direction elimination.MethodsBAO considers all available beam directions sampled on a gantry‐table map with the collimator angle aligned to the superior‐inferior axis (colli‐DTRT) or static (NC‐VMAT). First, FMO is performed, and beam directions are scored based on their contributions to the objective function. The map is thresholded to remove the least contributing beam directions, and arc candidates are formed by adjacent beam directions with the same table angle. Next, FMO and arc candidate trimming, based on objective function penalty score, is performed iteratively until a desired total gantry angle range is reached. Direct aperture optimization on the final set of colli‐DTRT or NC‐VMAT arcs generates deliverable plans. colli‐DTRT and NC‐VMAT plans were created for seven clinically‐motivated cases with targets in the head and neck (two cases), brain, esophagus, lung, breast, and prostate. colli‐DTRT and NC‐VMAT were compared to coplanar VMAT plans as well as to class‐solution non‐coplanar VMAT plans for the brain and head and neck cases. Dosimetric validation was performed for one colli‐DTRT (head and neck) and one NC‐VMAT (breast) plan using film measurements.ResultsTarget coverage and conformity was similar for all techniques. colli‐DTRT and NC‐VMAT plans had improved dosimetric performance compared to coplanar VMAT for all treatment sites except prostate where all techniques were equivalent. For the head and neck and brain cases, mean dose reduction—in percentage of the prescription dose—to parallel organs was on average 0.7% (colli‐DTRT), 0.8% (NC‐VMAT) and 0.4% (class‐solution) compared to VMAT. The reduction in D2% for the serial organs was on average 1.7% (colli‐DTRT), 2.0% (NC‐VMAT) and 0.9% (class‐solution). For the esophagus, lung, and breast cases, mean dose reduction to parallel organs was on average 0.2% (colli‐DTRT) and 0.3% (NC‐VMAT) compared to VMAT. The reduction in D2% for the serial organs was on average 1.3% (colli‐DTRT) and 0.9% (NC‐VMAT). Estimated delivery times for colli‐DTRT and NC‐VMAT were below 4 min for a full gantry angle range of 720°, including transitions between arcs, except for the brain case where multiple arcs covered the whole table angle range. These times are in the same order as the class‐solution for the head and neck and brain cases. Total optimization times were 25%–107% longer for colli‐DTRT, including BAO, compared to VMAT.ConclusionsWe successfully developed dosimetrically motivated BAO for colli‐DTRT and NC‐VMAT treatment planning. colli‐DTRT and NC‐VMAT are applicable to multiple treatment sites, including body sites, with beneficial or equivalent dosimetric performances compared to coplanar VMAT and reasonable delivery times.

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Section: Discussionmentioning

confidence: 99%

Section: Dao and Final Dose Calculationmentioning

confidence: 99%

Section: F I G U R Ementioning

confidence: 99%

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Dosimetrically motivated beam‐angle optimization for non‐coplanar arc radiotherapy with and without dynamic collimator rotation

Bertholet,

Zhu,

Guyer

et al. 2023

Medical Physics

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“…For demonstration, a dynamic trajectory radiotherapy (DTRT) path with dynamic gantry rotation, table rotation and collimator rotation was created retrospectively for a head and neck (H&N) case using the method described by Fix et al 21 . Additionally, a second path was created with an increased source‐to‐target distance (STD) of 110 cm by translating the table 10 cm away from the gantry in the beam direction along the whole path as described by Guyer et al 22 . The initial table position was set using the relative method with the reference point on the head plate.…”

Section: Methodsmentioning

confidence: 99%

“…described by Guyer et al 22 The initial table position was set using the relative method with the reference point on the head plate. The large male patient model with the arms down was chosen and an additional margin of 3 cm was set for the patient model.…”

Section: Collision Check Of Treatment Plansmentioning

confidence: 99%

Technical note: A collision prediction tool using Blender

Guyer,

Mueller,

Wyss

et al. 2023

J Applied Clin Med Phys

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Non‐coplanar radiotherapy treatment techniques on C‐arm linear accelerators have the potential to reduce dose to organs‐at‐risk in comparison with coplanar treatment techniques. Accurately predicting possible collisions between gantry, table and patient during treatment planning is needed to ensure patient safety. We offer a freely available collision prediction tool using Blender, a free and open‐source 3D computer graphics software toolset. A geometric model of a C‐arm linear accelerator including a library of patient models is created inside Blender. Based on the model, collision predictions can be used both to calculate collision‐free zones and to check treatment plans for collisions. The tool is validated for two setups, once with and once without a full body phantom with the same table position. For this, each gantry‐table angle combination with a 2° resolution is manually checked for collision interlocks at a TrueBeam system and compared to simulated collision predictions. For the collision check of a treatment plan, the tool outputs the minimal distance between the gantry, table and patient model and a video of the movement of the gantry and table, which is demonstrated for one use case. A graphical user interface allows user‐friendly input of the table and patient specification for the collision prediction tool. The validation resulted in a true positive rate of 100%, which is the rate between the number of correctly predicted collision gantry‐table combinations and the number of all measured collision gantry‐table combinations, and a true negative rate of 89%, which is the ratio between the number of correctly predicted collision‐free combinations and the number of all measured collision‐free combinations. A collision prediction tool is successfully created and able to produce maps of collision‐free zones and to test treatment plans for collisions including visualisation of the gantry and table movement.

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Serial and parallel organ‐at‐risk‐specific noncoplanar arc optimization for small versus large target volumes in liver SBRT

Lincoln,

MacDonald,

Ward

et al. 2024

J Applied Clin Med Phys

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Noncoplanar arc optimization has been shown to reduce OAR doses in SRS/SRT and has the potential to reduce doses to OARs in SBRT. Extracranial targets have additional considerations, including large OARs and, in the case of the liver, volume constraints on the healthy liver. Considering pathlengths through OARs that encompass target volumes may lead to specific dose reductions as in the encompassing healthy liver tissue. These optimizations must also leverage delivery efficiency and trajectory sampling to ensure ease of clinical translation. The purpose of this research is to generate optimized static‐couch arcs that separately consider serial and parallel OARs and arc delivery efficiency, with a trajectory sampling metric, towards the aim of reducing dose to OARs and the surrounding healthy liver tissue. Separate BEV cost maps were created for parallel, and serial OARs by means of a fast ray‐triangle intersection algorithm. An additional BEV cost map was created for the liver which, by definition, encompasses the liver tumors. The individual costs of these maps were summed and combined with the sampling metric for 100 000 random combinations of arc trajectories. A search algorithm was applied to find an arc trajectory solution that satisfied BEV cost and sampling optimization, while also ensuring an efficient delivery was possible with a low number of arcs. This method of arc selection was evaluated for 16 liver SBRT patients characterized by small and large target volumes. Comparisons were made with a clinical arc template of coplanar arcs. Dosimetric plan quality was evaluated using published guidelines and metrics from RTOG1112. Four of five plan quality metrics for the liver were significantly reduced when planned with optimized noncoplanar arcs. Median (range) reductions of the volumes receiving 10, 18, and 21 Gy were found of 140.4 (295.8) cc (p = 0.001), 28.2 (230.6) cc (p = 0.002) and 18.5 (155.5) cc (p = 0.04). A significant increase in median (range) dose to the right kidney of 0.2 ± 0.9 Gy (p = 0.03) was also found using optimized noncoplanar arcs, which was below the tolerance of 10 Gy for all cases. The average number of arcs chosen was 4 ± 1. Optimizing serial and parallel OARs separately during static couch noncoplanar arc selection significantly reduced the dose to the liver during SBRT using a moderate number of arcs.

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Enabling non-isocentric dynamic trajectory radiotherapy by integration of dynamic table translations

Cited by 9 publications

References 60 publications

Dosimetrically motivated beam‐angle optimization for non‐coplanar arc radiotherapy with and without dynamic collimator rotation

Dosimetrically motivated beam‐angle optimization for non‐coplanar arc radiotherapy with and without dynamic collimator rotation

Technical note: A collision prediction tool using Blender

Serial and parallel organ‐at‐risk‐specific noncoplanar arc optimization for small versus large target volumes in liver SBRT

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