WO2008130634A1 - Peinture à dose à arc unique pour une radiothérapie de précision - Google Patents

Peinture à dose à arc unique pour une radiothérapie de précision Download PDF

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Publication number
WO2008130634A1
WO2008130634A1 PCT/US2008/005028 US2008005028W WO2008130634A1 WO 2008130634 A1 WO2008130634 A1 WO 2008130634A1 US 2008005028 W US2008005028 W US 2008005028W WO 2008130634 A1 WO2008130634 A1 WO 2008130634A1
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Prior art keywords
leaf
single arc
radiation
aperture
dose
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PCT/US2008/005028
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English (en)
Inventor
Xinsheng Cedric Yu
Shuang Luan
Danny Z. Chen
Matthew A. Earl
Chao Wang
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The University Of Maryland, Baltimore
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Publication of WO2008130634A1 publication Critical patent/WO2008130634A1/fr
Priority to US14/020,500 priority Critical patent/USRE46953E1/en

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N5/00—Radiation therapy
    • A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
    • A61N5/103—Treatment planning systems
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N5/00—Radiation therapy
    • A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
    • A61N5/1042—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy with spatial modulation of the radiation beam within the treatment head
    • A61N5/1045—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy with spatial modulation of the radiation beam within the treatment head using a multi-leaf collimator, e.g. for intensity modulated radiation therapy or IMRT
    • A61N5/1047—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy with spatial modulation of the radiation beam within the treatment head using a multi-leaf collimator, e.g. for intensity modulated radiation therapy or IMRT with movement of the radiation head during application of radiation, e.g. for intensity modulated arc therapy or IMAT
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N5/00—Radiation therapy
    • A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
    • A61N5/103—Treatment planning systems
    • A61N5/1036—Leaf sequencing algorithms
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N5/00—Radiation therapy
    • A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
    • A61N5/1042—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy with spatial modulation of the radiation beam within the treatment head

Definitions

  • the present invention relates to the field of radiation oncology for malignant tumors and the like. Specifically, the present invention provides methods and systems for planning delivery of radiation therapy by means of a single-arc dose of radiation.
  • Conformal radiation therapy is an important procedure available to the physician for the treatment of malignant tumors. Such therapy is used for eradicating or shrinking tumors that are relatively inaccessible to other modes of treatment such as surgical excision.
  • ionizing radiation that is administered is damaging to both healthy and malignant tissue, it is important to confine the effect of the irradiation to the target tissue, to the extent possible, while sparing the adjacent tissue by minimizing irradiation thereto.
  • various techniques of irradiating a target tumor with a defined beam of ionizing radiation have been devised.
  • Such beams are often provided from a radiation source, e.g., x-ray photons or high- energy electrons, mounted on a rotating gantry, that allows the radiation source to be revolved in a generally circular path while providing a beam of radiation directed generally at the isocenter of such a path.
  • a radiation source e.g., x-ray photons or high- energy electrons
  • a patient is positioned within the circular path, preferably with the tumor located, to the extent possible, at the isocenter for receiving the maximum dose of radiation as the source is revolved.
  • the cross-sectional shape and size of the radiation beam is typically varied as the source is positioned at different angles by rotation of the gantry in order to assure, to the extent possible, that the radiation is incident on the tumor itself and not on adjacent healthy tissue.
  • the intensity of the beam can be varied within the cross-sectional area in order to optimize the distribution of absorbed radiation within the tumor.
  • IMR Intensity-modulated radiation therapy
  • intensity-modulated radiation therapy has been widely adopted as a new tool in radiation therapy to deliver high doses of radiation to the tumor while providing maximal sparing of surrounding critical structures.
  • IMRT intensity-modulated radiation therapy
  • Both rotational and gantry-fixed IMRT techniques have been implemented clinically using dynamic multileaf collimation (DMLC) (1-6).
  • IMRT In gantry-fixed IMRT, multiple radiation beams at different orientations, each with spatially modulated beam intensities, are used (1-2, 4).
  • the beams may be administered to the patient in a single transverse plane as the source revolves around the patient (coplanar) or may be shifted axially with respect to the patient (non-coplanar).
  • Rotational IMRT typically administered by a continuously revolving source that is also moved axially along the patient, as it is currently practiced, mainly employs temporally modulated fan beams (3).
  • U.S. Patent 5,818,902 to Yu teaches the use of overlapping multiple arcs to deliver modulated beam intensities around the patient which is called intensity-modulated arc therapy (IMAT). Delivery of the radiation during overlapping multiple arcs achieves modulated beam intensities at all angles around the patient (5-6).
  • IMAT has not been widely adopted for clinical use.
  • the intensity distributions are first optimized using a treatment planning system for tightly-spaced beam angles every 5-10 degrees all around the tumor. These intensity distributions are then approximated by a stack of uniform intensity segments with different cross sectional shapes.
  • the present invention is directed to a method for designing a radiation treatment for a subject using single arc dose painting.
  • the method comprises providing an unconstrained optimization map which supplies intensity profiles of densely-spaced radiation beams and aligning each intensity profile to a pair of multiple leaf collimation (MLC) leaves.
  • MLC multiple leaf collimation
  • a shortest path algorithm is applied to convert each pair of MLC leaves to a set of leaf aperture sequences, where each set of leaf aperture sequences forms a shortest path single arc thereof andeach single arc of leaf apertures is connected to form a final treatment single arc, thereby designing the single arc dose painting radiation treatment.
  • the present invention is directed to a related method further comprising delivering a continuous dose of radiation to the subject through each aperture during a single rotation along one or more final treatment single arc paths.
  • the present invention is directed to another related method further comprising adjusting a shape of the aperture as a radiation dose delivery angle changes along the final treatment single arc to keep the dose constant.
  • the present invention also is directed to a method for irradiating a tumor in a subject.
  • the method comprises delivering a continuous dose of radiation to the tumor through sets of multiple leaf collimation (MLC) aperture sequences during a single rotation along one or more treatment single arc paths.
  • MLC leaf collimation
  • the present invention is directed a related method comprising further adjusting the aperture shape as described supra.
  • the present invention is directed to another related method where, prior to delivering the radiation dose, the method further comprises steps of providing an unconstrained optimization map which supplies intensity profiles of densely-spaced radiation beams and aligning each intensity profile to a pair of multiple leaf collimation (MLC) leaves, applying a shortest path algorithm to convert each pair of MLC leaves to the set of leaf aperture sequences and connecting each single arc of leaf apertures to form the final treatment single arc.
  • MLC multiple leaf collimation
  • the present invention is directed further to a system for delivering radiation treatment using single arc dose painting.
  • the system comprises a radiation source for generating a radiation beam, a multiple leaf collimator having a plurality of leafs for shaping the radiation beam, a structure for generating an unconstrained optimization map of intensity profiles of densely-spaced radiation beams, a structure for aligning each intensity profile to a pair of multiple leaf collimation (MLC) leaves, and a structure for applying a shortest path algorithm, said shortest path algorithm converting each pair of MLC leaves to a set of leaf aperture sequences forming a shortest path single arc thereof, such that the shortest path algorithm further connects each single arc of leaf apertures to form a final treatment single arc effective for single arc dose painting.
  • MLC multiple leaf collimation
  • the present invention is directed a related system where the shortest path algorithm further comprises adjusting the aperture shape as described supra.
  • the present invention is directed further still to a computer-readable medium tangibly storing an algorithm to determine a final single arc path for a single arc dose painting radiation treatment.
  • the algorithm enables instructions to convert pairs of multiple leaf collimation (MLC) leaves to sets of leaf aperture sequences that form a shortest path single arc thereof, where the pairs of MLC leaves each are aligned to an intensity profile of densely-spaced radiation beams, and to connect each single arc of leaf apertures to form a final treatment single arc.
  • the present invention is directed a related computer-readable medium where the shortest path algorithm further enables adjusting the aperture shape as described supra.
  • Figures 1A-1C illustrate how to flip the monotone decreasing path p r to a monotone increasing path p ' r ( Figure 1 A), how to flip two monotone decreasing paths p, and p r to two monotone increasing paths p ' 7 and p ' r ( Figure 1B) and how the xy-monotone region enclosed by the two paths p ' 7 and p ⁇ in Figure 1B corresponds to a sequence of n vertical bars 8 1 ,6 2 , ⁇ ⁇ ⁇ ,S n ( Figure 1C).
  • Figures 2A-2D illustrate the transformation of G ' into " 6 ( Figures 2A- 2B) and the layered DAGs G ;1 ; i +1 , G /1
  • Figures 3A-3C illustrate the geometry of the vertex layer U 1 of the DAG G ' for l start ⁇ i ⁇ r start , r staft ⁇ i ⁇ / ⁇ , and I ⁇ ⁇ i ⁇ r ⁇ .
  • all vertices in the vertex layer L 1 are mapped to circled points on the 2-D plane; these points form all the lattice points in a convex polygon (possibly degenerated to a line segment) marked by the shaded area.
  • Figures 4A-4B illustrates sliding window leaf sequencing.
  • the desired intensity profile is aligned with a leaf pair.
  • Figure 4B shows separated intensity profiles to be conformed by the leading (right) and training
  • Figure 4C shows adjusted leaf traveling trajectories after considering the physical constraints of leaf travel.
  • Figures 5A-5D illustrate steps of the shortest path graph algorithm for converting an intensity profile into k MLC leaf openings with the minimum error.
  • Figures 6A-6C illustrate a step of the shortest path graph algorithm for adjusting a one-dimensional IMAT arc.
  • Figures 7A-7B illustrate the planning of a single arc dose painting.
  • Figures 8A-8 B illustrate leaf position and aperture weight optimization using the shortest path graph algorithm.
  • Figures b illustrate field width adjustment on the right side (b) and on the left side ( Figures 9C-9D).
  • Figures 10A-10C illustrate a planned ( Figures 10A-10B) and delivered ( Figure 10C) dose distribution for a complicated head and neck case with single arc dose painting.
  • the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.”
  • “about” refers to numeric values, including whole numbers, fractions, percentages, etc., whether or not explicitly indicated.
  • the term “about” generally refers to a range of numerical values, e.g., +/- 5-10% of the recited value, that one would consider equivalent to the recited value, e.g., having the same function or result. In some instances, the term “about” may include numerical values that are rounded to the nearest significant figure.
  • the term "subject" refers to any recipient of single arc dose painting radiation treatment
  • the present invention there is provided method for designing a radiation treatment for a subject using single arc dose painting, comprising providing an unconstrained optimization map which supplies intensity profiles of densely-spaced radiation beams; aligning each intensity profile to a pair of multiple leaf collimation (MLC) leaves; applying a shortest path algorithm to convert each pair of MLC leaves to a set of leaf aperture sequences, where the set of leaf aperture sequences form a shortest path single arc thereof; and connecting each single arc of leaf apertures to form a final treatment single arc, thereby designing the single arc dose painting radiation treatment.
  • the method comprises delivering a continuous dose of radiation to the subject through each aperture during a single rotation along one or more final treatment single arc paths.
  • the method comprises adjusting a shape of the aperture as a radiation dose delivery angle changes along the final treatment single arc to keep the dose constant.
  • the paths of more than one single arc may be non-coplanar.
  • the apertures may sweep back and forth along the single arc path during delivery of the radiation dose.
  • multiple leaf collimation may be dynamic.
  • sequencing leaf apertures may comprise one or more of a line segment approximation on component intensity profiles leaf position, weight optimization of apertures or optimization of leaf position and aperture weight.
  • the leaf aperture sequences in each set may have one or both of a different starting or ending leaf aperture.
  • starting and ending positions of a leaf aperture trajectory may be fixed.
  • a method for irradiating a tumor in a subject comprising delivering a continuous dose of radiation to the tumor through sets of multiple leaf collimation (MLC) aperture sequences during a single rotation along one or more treatment single arc paths.
  • MLC leaf collimation
  • the method may comprise adjusting a shape of the aperture as a radiation dose delivery angle changes along the treatment single arc to keep the dose constant.
  • the method may comprise providing an unconstrained optimization map which supplies intensity profiles of densely- spaced radiation beams; aligning each intensity profile to a pair of multiple leaf collimation (MLC) leaves; applying a shortest path algorithm to convert each pair of MLC leaves to the set of leaf aperture sequences; and connecting each single arc of leaf apertures to form the final treatment single arc.
  • sequencing leaf apertures may comprise one or more of a line segment approximation on component intensity profiles leaf position, weight optimization of apertures or optimization of leaf position and aperture weight.
  • each set of MLC aperture sequences may form a shortest path single arc thereof, where the sets are connected to form a shortest path treatment single arc.
  • the paths of more than one single arc may be non-coplanar.
  • the apertures may slide back and forth along the single arc path during delivery of the radiation dose.
  • multiple leaf collimation may be dynamic.
  • a system for delivering radiation treatment using single arc dose painting comprising a radiation source for generating a radiation beam; a multiple leaf collimator having a plurality of leafs for shaping the radiation beam; a structure for generating an unconstrained optimization map of intensity profiles of densely- spaced radiation beams; a structure for aligning each intensity profile to a pair of multiple leaf collimation (MLC) leaves; and a structure for applying a shortest path algorithm, where the shortest path algorithm converts each pair of MLC leaves to a set of leaf aperture sequences forming a shortest path single arc thereof and where the shortest path algorithm further connects each single arc of leaf apertures to form a final treatment single arc effective for single arc dose painting.
  • MLC multiple leaf collimator
  • the shortest path algorithm may adjust a shape of the leaf aperture as a radiation dose delivery angle changes along the final treatment single arc thereby keeping the dose constant.
  • the shortest path algorithm may sequence leaf apertures via one or more of a line segment approximation on component intensity profiles leaf position, weight optimization of apertures or optimization of leaf position and aperture weight.
  • multiple leaf collimation may be dynamic.
  • a computer-readable medium tangibly storing an algorithm to determine a final single arc path for a single arc dose painting radiation treatment, said algorithm enabling instructions to convert pairs of multiple leaf collimation (MLC) leaves to sets of leaf aperture sequences that form a shortest path single arc thereof, said pairs of MLC leaves each aligned to an intensity profile of densely-spaced radiation beams; and connect each single arc of leaf apertures to form a final treatment single arc.
  • MLC multiple leaf collimation
  • the algorithm may enable instructions to adjust a shape of the leaf aperture as a radiation dose delivery angle changes along the final treatment single arc thereby keeping the dose constant.
  • the algorithm amy sequence leaf apertures via one or more of a line segment approximation on component intensity profiles leaf position, weight optimization of apertures or optimization of leaf position and aperture weight.
  • SADP single arc dose painting
  • Planning a single arc capable of delivering the ultimately optimal radiation treatment is based on the recognition that the same intended dose to the tumor delivered by an aperture at a planned angle can be delivered by a slightly modified aperture from a slightly different angle. Consequently, a single rotation with dynamically varying apertures can achieve the same results as a procedure that delivers a plurality of intensity modulated fixed beams.
  • inventive leaf sequencing method of the invention achieves an interconnected relationship of multiple leaf collimator (MLC) apertures so that the MLC leaves are not required to move large distances between adjacent angles of the planned treatment.
  • MLC leaf collimator
  • the dose rate can change among the angular intervals.
  • the aperture size and shape can be optimized to maintain a substantially constant dose rate throughout the entire treatment arc.
  • the apertures can have different weights, delivered either through dose rate variation with all apertures occupying the same angular range or delivered without dose rate variation by allowing the aperture with higher weights to be delivered over a larger angular range. That is, the method is applicable to machines with and without the ability to change dose rates during delivery.
  • multiple non-coplanar arcs can be planned according to the methods of the invention.
  • the dose overlap in the tumor is considered, rather than beam overlap in each beam direction as with current IMRT planning. This relies on the recognition that the same dose can be delivered to the tumor by two beam apertures of slightly different shapes directed at the tumor from two angular directions a few degrees apart.
  • Planning starts with an unconstrained optimization with a large number of beams evenly spaced, for example, every 5-10 degrees.
  • different number of apertures and weights are initialized using a "sliding window" line-segment approximation.
  • the apertures are interconnected.
  • the shape and weights of these apertures are further optimized (fine-tuned) to improve the plan quality.
  • To deliver these apertures in one arc they are spaced within their own planning angular interval by moving the overlapping apertures to other beam angles within the interval.
  • the aperture shapes are varied, depending on how many degrees they are moved from the planned angle.
  • Intensity modulation is allowed during intensity optimization and more than one aperture shapes is allowed within each planning angular interval.
  • the apertures are spaced and adjusted within the planning angular interval rather than overlapped to be delivered by using multiple arcs. Because, as described herein, an entire treatment dose is delivered in a single rotation, the number of different apertures per planning angular interval can vary according to the complexity of the required intensity distribution.
  • systems effective to deliver radiation to a tumor using single arc dose painting comprise those radiation delivery devices having suitable structures for radiation therapy of malignant tumors or other conditions responsvie to such treatment.
  • such devices comprise at least a source of radiation, amoveable, rotatable gantriy, a multiple leaf collimator, e.g., a dynamic multiple leaf collimater, a platform for a subject receiving radiation therapy, and the necessary computer hardware and software, processor, memory and connections necessary to run the device.
  • system comprises a module or structure, such as, but not limited to, a computer memory, a computer-readable memory or computer program storage device which is suitable to tangibly store and execute the algorithms described herein, such as, standard algorithms for intensity profile optimization and the novel short path algorithms provided herein.
  • a module or structure such as, but not limited to, a computer memory, a computer-readable memory or computer program storage device which is suitable to tangibly store and execute the algorithms described herein, such as, standard algorithms for intensity profile optimization and the novel short path algorithms provided herein.
  • CCPP Constrained Coupled Path Planning
  • CCPP constrained coupled path planning
  • the algorithm can be adapted easily to handle the other case in which I 6n ⁇ ⁇ r start .
  • the region P(p h p r ) is a rectilinear xy-monotone polygon in R 9 and consists of a sequence of n vertical bars.
  • the CCPP problem can be solved by transforming it to computing a shortest path in a directed acyclic graph, DAG G ' .
  • a shortest s-to-t path in G ' corresponds to an optimal solution for the CCPP problem and, further, the vertices and edges of GO have geometric properties similar to those of dominated sets (Figs. 3A-3C).
  • Such similar dominated sets may be D(H 1 H), D( ⁇ ,H) (0 ⁇ ⁇ ⁇ H), D(O 1 H), D( ⁇ , ⁇ ) (0 ⁇ ⁇ ⁇ ⁇ ⁇ H), O ⁇ Q, ⁇ ) (0 ⁇ ⁇ ⁇ H), and D(O, 0).
  • the shortest path computation can be sped up and the CCPP algorithm takes O( ⁇ H ⁇ ) time.
  • CCPP problem instances are solved on f, n, H, ⁇ , C 1 Istar t , r stan , len d , and r ⁇ for all possible combinations of l start , r sm , / ⁇ , and r ⁇ .
  • S 1 and S 2 with S 1 (resp., S 2 ) containing those with I 6 ⁇ ⁇ r start (resp., I ⁇ ⁇ r start ).
  • An instance I k (1 ⁇ k ⁇ N) corresponds to a shortest path problem on a vertex-weighted DAG, denoted by G ⁇ , of O(nHA) vertices and O(nH 2 A 2 ) edges.
  • G ⁇ vertex-weighted DAG
  • the key observation is that G ' k can be transformed into an edge-weighted DAG, denoted by " G ⁇ 1 with only O( ⁇ ) vertices and 0(A 2 ) edges.
  • the algorithm consists of two main steps. First, prepare the weights of all edges in ' G 1 , ' G 2 and ' G N (0(A 2 ) edges for each " G*). The weights of all the O(n 4 A 2 ) edges are implicitly computed and stored in a batch fashion, in totally O(n 2 H 2 ) time, such that for any edge, its weight can be reported in 0(1) time. Second, a shortest path is computed in ' G 1 , ' G 2 , . . . , and ' G N , respectively. It is shown that each " G k (1 ⁇ k ⁇ N) is a DAG satisfying the Monge property (1-2,4).
  • a shortest path in ⁇ G k takes only 0(A) time to compute.
  • v is an element of V(G ' ), denote by ⁇ ' ( ⁇ , v) a shortest u-to- ⁇ / path in G ' .
  • An edge-weighted directed graph " G (V( ' G),E( ' G)) is constructed from G ' as follows (Figs. 2A-2B).
  • the vertex set VfG) is a subset of V(G " ), and consists of two dummy vertices s and f and four vertex layers:
  • the edge set E( " G) is simply U6- 1 & * XH-O U (W X ZI) u [U * ⁇ * ⁇ ).
  • the subgraph of "G between any two consecutive vertex layers is a complete bipartite graph.
  • ⁇ (u, v) +°° if there is no path from u to v in G ' .
  • G is an edge-weighted DAG and has O( ⁇ ) vertices and O(A 2 ) edges (by the definition of L ' j in Example 1).
  • ⁇ (p) ⁇ e is an elemen t o f p * ⁇ ( ⁇ )•
  • a shortest s-to-f path in G ' is closely related to a shortest s-to-t path in " G.
  • Equation (1) Before explaining why the vertex layers L ' , stali , L ' rstart , L ' /e/7dt1 , and /_ ' re ⁇ d+ i from G ' for the construction of " G were chosen, Equation (1) must be reviewed.
  • Equation (1) implies that the /-th vertex layer in any G' k (1 ⁇ k ⁇ N) is in exactly one of five possible states, denoted by ⁇ j (l) , ⁇ j (ll) , ⁇ i (lll) , ⁇ i (IV) , and ⁇ i (V) , e.g., ⁇ i (l) if 1 ⁇ / ⁇ l start ).
  • the type II, III, IV, and V vertex layers are defined similarly.
  • ⁇ ' lend * ⁇ and ⁇ ' re ⁇ d+i. and I ' re ⁇ d+1 and f are of type I, II, III, IV, and V, respectively (Fig. 2A).
  • O(n 4 ⁇ 2 ) edges actually correspond to only O(n 2 A 2 ) distinct one-pair shortest path problem instances.
  • SP(u, v, k) the corresponding one-pair shortest path instance, i.e., finding a shortest w-to-v path in G ' k .
  • G i1ii2 be a layered DAG whose vertices consist of the vertex layers A 11 Z1 , A 11 Vi +1 , A 111 Z1+2 , . . . , A 1 Vi, and A ⁇ z 2 . in this order, and whose edges are defined based on the same domination relation D(-, ⁇ ).
  • SP(u, v, k) is equivalent to finding a shortest u-to-v path in Gj 1 J2 . Since I 1 (resp., i2) ranges from 1 to n, G 11 J2 has O(n 2 ) possible choices. Note that u (resp., v) belongs to the layer A 11 Z1 (resp., A 17 Z2 ), which contains O( ⁇ ) vertices for any Z 1 (resp., / 2 ). It follows that SP(u, v, k) has O(n 4 A 2 ) possible choices for the case where u (resp., v) lies in the 2nd (resp., 3rd) layer of " G k .
  • Each instance is specified by a source vertex u is an element of ⁇ ⁇ / i and a destination vertex v is an element of A 17 Z2 -
  • Gj 1 J2 contains the vertex layers A 11 Z1 , A 111 ZH i, A 111 Z i +2 , • ⁇ • .
  • the algorithm for computing a shortest path in the DAG " G as defined as defined above is presented.
  • the key idea is to show that " G satisfies the Monge property [1 , 2, 4], and thus a shortest path in " G can be computed by examining only a small portion of its edges.
  • the first planning step for single arc dose painting is unconstrained intensity optimization. Different algorithms can be used for achieving this step (11-13). Suitable algorithms are available in the relevant literature (8,10). As with IMAT 1 an arc is approximated with multiple fixed radiation beams evenly spaced every 5-10 degrees (5).
  • Step two in single-arc dose painting is the conversion of the optimized beam intensities into connected field apertures.
  • the goal is to find a set of connected field shapes that when delivered dynamically based on linear interpolation between the apertures, will result in minimum discrepancy to the optimized intensity profile.
  • leaf sequencing a hybrid approach has been developed. For simple cases the method called line segment approximation on component intensity profiles is appropriate. For more complicated cases, leaf position and aperture weight optimization and leaf position and aperture weight optimization may be used.
  • This method is based on a "sliding window” technique. Recognizing that any intensity pattern can be delivered by sliding a varying aperture in either direction, each of the intensity patterns can be converted into “sliding window” dynamic control points. The only constraint to ensure the interconnectedness of the intensity patterns is that in the next interval, the direction of the "sliding window" has to be in the opposite direction. Accordingly, the apertures defined by the multi-leaf collimator (MLC) sweep back and forth, completing one cycle in every two intervals.
  • MLC multi-leaf collimator
  • the separated profiles become the leading and trailing leaf positions as functions of time. If both leaves are moved according to Figure 1B, the desired intensity profile will be created. Inspection of Figure 4B 1 reveals that for both leaves, there will be sections where the leaves are required to change positions with no elapsed time (the flat portions of the profiles). Accordingly, in order to make the dose delivery physically achievable, the minimum gradient required for leaf travel (governed by the maximum leaf traveling speed) is added to the flat portions, while the same amount is added to the other profile so that the difference between the two profiles is kept substantially constant (Fig. 4C). When this intensity profile is delivered, the apertures of varying width formed by both leaves will move smoothly from the left to the right. Such smooth motion is the origin of the term "sliding window technique". The left leaf can alternatively be considered to be the leading leaf and the right leaf to be the trailing leaf, thereby delivering the same intensity distribution by sliding the "window" from the right to the left.
  • the control- points are generated by evenly dividing the total monitor units (MUs) required by the number of segments, which is normally relatively large ( ⁇ 50).
  • MUs monitor units
  • ⁇ 50 the number of segments
  • the treatment apparatus, linac and MLC performs the linear interpolation automatically, accurate delivery is ensured if the vertices that join two lines of different slopes are used as control points. Therefore, the gradient turning positions of the original intensity profile (the intercepts of the vertical lines with the profiles) are used as the initial estimations of the control points. In essence, the original component intensity profiles are approximated with connected line segments.
  • the apertures selected from the sliding window leaf sequence are naturally interconnected within each planning interval.
  • the apertures within each interval will move either left to right or right to left.
  • the apertures are sequenced in such a way that: 1) the MLC leaves move in opposite directions in any two neighboring angular intervals; and 2) the two aperture shapes connecting any two angular intervals do not violate the physical constraints of the MLC (i.e., the shapes are not so drastically different as to require large MLC movements).
  • any intensity map can be delivered dynamically in either left-to-right or right-to-left leaf motion, the direction of MLC motion alternates between neighboring beams and the aperture shape connectivity is considered throughout the arc.
  • the shape-varying beam aperture (or "dynamic window”) slides back and forth while the gantry rotates around the patient.
  • Leaf position and aperture weight optimization One of the concerns presented by method using line segment approximation to component intensity profiles is that for complex intensity distributions, using this method alone may result in a plan with very high machine beam-on times and may requires too many control points to maintain a very close dose conformity. Thus for more complicated cases, two alternative, and somewhat more complex, methods can be used, as described below.
  • each pair of MLC leaves will deliver a set of densely-spaced intensity profiles that are aligned with this leaf pair.
  • the method comprises the following key steps: First, for every pair of MLC leaves, each of its aligned intensity profiles is converted into a set of k leaf openings using a geometric k-link shortest path algorithm with equal beam-on times that incurs the minimum error. Second, the leaf openings for the same pair of MLC leaves are connected together to form a single-arc of leaf openings using a geometric shortest path algorithm that ensures a smooth transition between adjacent leaf openings while minimizing the error incurred. Third, the single-arcs for each pair of MLC leaves are then combined to form the final single-arc treatment plan.
  • FIG. 5A-5D illustrate the key idea of this step.
  • the error here is the integral of the absolute difference between the two functions, shaded area in Fig. 5C).
  • each leaf opening is represented by a rectangle whose left and right ends are the positions of the MLC leaf pair and whose height is its beam-on time.
  • the simplified intensity profile is created by "stacking up" these rectangles.
  • the resulting profile g(x) can have up to k upward edges and k downward edges, if we traverse the profile curve from left to right (Fig. 5B).
  • This problem can be solved by searching for an optimal /c-weight path in a graph capturing the geometry of the problem; the total cost of the path represents the error between the simplified profile and the input profile, and its weight indicates how many leaf openings are needed to create the simplified profile.
  • Fig. 5C illustrates such a /(-weight path, where the k upward edges are highlighted in red (solid if black and white) and the error is the area sum of the shaded regions.
  • a directed graph G is constructed as in Fig. 5D. Specifically, for each possible height h of the rectangles, a grid structure is imposed, whose vertical edge lengths are h and horizontal edge lengths are of the resolution size of the given intensity patterns. Each grid node is a vertex of the graph G . The lower leftmost grid node is the source vertex s of G, and the lower rightmost node is the sink vertex t. For any horizontal grid edge, we put an edge in G from left to right with a zero weight and a cost that is the error incurred when this edge is used by the resulting profile (Fig. 5D) for a horizontal edge and its cost, i.e., the shaded area).
  • each intensity profile into a simplified profile that can be deliverable by k leaf openings.
  • break each simplified intensity profile is broken into a set of canonical leaf openings.
  • a set of leaf openings is called canonical if only if for any two leaf openings [/,, r] and [I j , ⁇ (where /, and / y denote the left leaf positions, and r, and ⁇ denote the right leaf positions), either l, ⁇ l h ⁇ - ⁇ , or l, ⁇ l,, ⁇ .
  • a set of canonical leaf openings can be sorted from left to right.
  • Figures 6A-6C illustrate the key concept for the second step, i.e., for combining the canonical leaf openings into arcs.
  • its single-arc can be viewed as two curves, each representing the leaf trajectory as a function of the leaf position with respect to the gantry angles.
  • the solid curves in Fig. 6B show the corresponding leaf trajectories of the single-arc illustrated in Fig. 6A. If this single-arc is not deliverable under the maximum leaf speed constraint, the arc has to be adjusted to make it deliverable while minimizing the error incurred by the adjustment.
  • each leaf trajectory is a function of the leaf position with respect to the gantry angles, it can be viewed as a path of leaf positions along the gantry angle direction. This implies that the above adjustment problem can be solved by modeling it as a shortest path problem, in which the cost of a path is the error of the adjustment.
  • Figure 6C shows the graph construction. Each possible leaf position is a vertex, and two vertices for adjacent gantry angles are connected by an edge if they satisfy the maximum leaf speed constraint.
  • Each vertex has a cost for the error incurred when adjusting the corresponding original leaf position for its gantry angle using that vertex. Geometrically, this error corresponds to a shaded region in Figure 6B. Hence, the problem of adjusting a single arc as originally planned into a deliverable arc becomes a shortest path problem.
  • the spacing of the apertures within each interval is also straightforward. This is because the apertures obtained for each angular interval can sorted from left to right.
  • the angular interval can be evenly divided the by the number of apertures used to reproduce the intensity distribution.
  • the apertures can be sequenced in such a way that: 1) the MLC leaves move in opposite directions in any two neighboring angular intervals; and 2) the two aperture shapes connecting any two angular intervals do not violate the physical constraints of the MLC, i.e., they are not so drastically different as to require large MLC movements.
  • the shape-varying beam aperture slides back and forth while the gantry rotates around the patient. Since the apertures for different angular intervals are obtained with different dose rates, this single arc plan may require dose rate changes during the delivery.
  • Figure 7A shows a sample single-arc plan, where the red curve represents the left leaf trajectory and the blue curve represents the right leaf trajectory. Note that, since, in a single-arc plan, the MLC keeps moving as the gantry rotates 360° around the patient at constant speed, the leaf trajectory is actually a functional curve between gantry angle and MLC leaf positions. For each small angular interval ⁇ (typically 5°-10°), the portions of the leaf trajectories deliver a fluence profile (Fig. 7B).
  • ⁇ typically 5°-10°
  • the intensity profile in every planning beam interval for each pair of MLC leaves is converted to a set of candidate sequences of leaf openings using a shortest path algorithm with minimized error subject to the error bound.
  • These candidate sequences may differ from each other in the starting and/or ending leaf openings.
  • Figure 8B shows a candidate sequence for the intensity profile as shown in Fig. 8A with certain starting and ending leaf trajectory positions.
  • the goal here is to construct a graph whose nodes are the candidate leaf trajectories. Each node will have a cost associated with it, which is the error of the trajectory when delivering its own profile. Two nodes from adjacent angular intervals are connected together if their transitions are smooth.
  • a shortest path here yields an optimal single-arc plan. To improve the running time, one limits the number of candidate trajectories, e.g., by restricting the trajectories to be monotonic.
  • sequences computed in the first step are connected together to form a single arc of leaf openings using a shortest path to ensure a smooth transition of the leaf positions between adjacent planning beam intervals while minimizing the total error incurred.
  • MLC leaves are then combined to form the final single-arc treatment plan.
  • the method can compute a tradeoff between error and number of control points, or error and machine beam-on times.
  • the apertures are all at the designated planning angle at the center of the planning interval. When we move the aperture to another angle a few degrees away, the dose will change slightly. To maintain the dose delivered to the target, the apertures are adjusted as follows:
  • AB is the radiation source to rotational center i.e. isocenter, distance
  • Figure 9B omits DABC for clarity. From Figs. 9A-9B, the following equation may be written:
  • the new aperture widths can be set to provide the same coverage at the new angle as the original aperture provided at the planned angle.
  • a simple aperture weight and shape optimization can be performed to further refine the single arc to deplete any potential rooms of improvement of the treatment plan quality.
  • FIG. 10A One plan is for a larynx case with 3 targets, each with different dose specifications (Fig. 10A).
  • Figure 10B shows the dose distribution on a transverse slice at neck level resulting from the single-arc plan and
  • Figure 1OC is the result of dose verification by delivering the single-arc plan to a phantom. Note that the phantom is different in size and shape from the patient and the calculated dose from the same plan is therefore also different.
  • the following references are cited herein.

Abstract

L'invention porte sur des procédés et des systèmes pour mettre au point une radiothérapie pour un sujet à l'aide d'une peinture de dose à arc unique. Les procédés et systèmes comprennent un algorithme ou un produit pouvant être lu par ordinateur ayant celui-ci, pour planifier la radiothérapie. L'algorithme convertit des paires de lames de collimation multilames (MLC) en ensemble de séquences d'ouverture de lame qui forment un arc unique à trajet le plus court de celui-ci où les paires de lames MLC sont chacune alignées à un profil d'intensité des faisceaux de rayonnement espacés de façon dense, et connecte chaque arc simple d'ouvertures de lame pour former un arc unique de traitement final. L'invention porte également sur un procédé pour irradier une tumeur dans un sujet à l'aide d'une peinture de dose à arc unique.
PCT/US2008/005028 2007-04-20 2008-04-18 Peinture à dose à arc unique pour une radiothérapie de précision WO2008130634A1 (fr)

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US7894574B1 (en) 2009-09-22 2011-02-22 Varian Medical Systems International Ag Apparatus and method pertaining to dynamic use of a radiation therapy collimator
WO2011041500A2 (fr) * 2009-09-30 2011-04-07 Stc. Unm Système et procédés d'application de radiochirurgie et de radiothérapie photonique
US7986768B2 (en) 2009-02-19 2011-07-26 Varian Medical Systems International Ag Apparatus and method to facilitate generating a treatment plan for irradiating a patient's treatment volume
US8009802B2 (en) 2009-09-22 2011-08-30 Varian Medical Systems International Ag Method and apparatus to facilitate supplementing a dose-volume histogram constraint using an adaptive dose-volume histogram constraint
WO2012010215A1 (fr) * 2010-07-23 2012-01-26 Brainlab Ag Commande non planaire d'un faisceau de traitement
US9907979B2 (en) 2008-09-09 2018-03-06 Varian Medical Systems International Ag Apparatus and method to facilitate adapting a radiation treatment plan

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US5189687A (en) * 1987-12-03 1993-02-23 University Of Florida Research Foundation, Inc. Apparatus for stereotactic radiosurgery
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Cited By (15)

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US9907979B2 (en) 2008-09-09 2018-03-06 Varian Medical Systems International Ag Apparatus and method to facilitate adapting a radiation treatment plan
US8363785B2 (en) 2009-02-19 2013-01-29 Varian Medical Systems International Ag Apparatus and method to facilitate generating a treatment plan for irradiating a patient's treatment volume
US7986768B2 (en) 2009-02-19 2011-07-26 Varian Medical Systems International Ag Apparatus and method to facilitate generating a treatment plan for irradiating a patient's treatment volume
US7831018B1 (en) 2009-06-04 2010-11-09 Varian Medical Systems International Ag Method and apparatus to facilitate optimizing a radiation-treatment leaf-sequence plan
US7894574B1 (en) 2009-09-22 2011-02-22 Varian Medical Systems International Ag Apparatus and method pertaining to dynamic use of a radiation therapy collimator
US8009802B2 (en) 2009-09-22 2011-08-30 Varian Medical Systems International Ag Method and apparatus to facilitate supplementing a dose-volume histogram constraint using an adaptive dose-volume histogram constraint
US9387348B2 (en) 2009-09-30 2016-07-12 Stc.Unm System and methods of photon-based radiotherapy and radiosurgery delivery
US8835877B2 (en) 2009-09-30 2014-09-16 Stc.Unm System and methods of photon-based radiotherapy and radiosurgery delivery
WO2011041500A3 (fr) * 2009-09-30 2011-08-18 Stc. Unm Système et procédés d'application de radiochirurgie et de radiothérapie photonique
US9561389B2 (en) 2009-09-30 2017-02-07 Stc.Unm System and methods of photon-based radiotherapy and radiosurgery delivery
US9827446B2 (en) 2009-09-30 2017-11-28 Stc.Unm System and methods of photon-based radiotherapy and radiosurgery delivery
WO2011041500A2 (fr) * 2009-09-30 2011-04-07 Stc. Unm Système et procédés d'application de radiochirurgie et de radiothérapie photonique
WO2012010215A1 (fr) * 2010-07-23 2012-01-26 Brainlab Ag Commande non planaire d'un faisceau de traitement
US9630026B2 (en) 2010-07-23 2017-04-25 Brainlab Ag Non-planar treatment beam control
US10052501B2 (en) 2010-07-23 2018-08-21 Brainlab Ag Treatment beam control

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