An arc‐sequencing algorithm for intensity modulated arc therapy

Abstract

Intensity modulated arc therapy (IMAT) is an intensity modulated radiation therapy delivery technique originally proposed as an alternative to tomotherapy. IMAT uses a series of overlapping arcs to deliver optimized intensity patterns from each beam direction. The full potential of IMAT has gone largely unrealized due in part to a lack of robust and commercially available inverse planning tools. To address this, we have implemented an IMAT arc-sequencing algorithm that translates optimized intensity maps into deliverable IMAT plans. The sequencing algorithm uses simulated annealing to simultaneously optimize the aperture shapes and weights throughout each arc. The sequencer enforces the delivery constraints while minimizing the discrepancies between the optimized and sequenced intensity maps. The performance of the algorithm has been tested for ten patient cases (3 prostate, 3 brain, 2 head-and-neck, 1 lung, and 1 pancreas). Seven coplanar IMAT plans were created using an average of 4.6 arcs and 685 monitor units. Additionally, three noncoplanar plans were created using an average of 16 arcs and 498 monitor units. The results demonstrate that the arc sequencer can provide efficient and highly conformal IMAT plans. An average sequencing time of approximately 20 min was observed.

Comparative analysis of SmartArc‐based dual arc volumetric‐modulated arc radiotherapy (VMAT) versus intensity‐modulated radiotherapy (IMRT) for nasopharyngeal carcinoma

“…( 12 , 54 , 57 , 58 ) Recent studies ( 18 , 25 ) on 65 HN cancer patients reported that multiple arcs were needed for such patients. For the more complex HN cancer cases, Shepard et al ( 18 , 19 ) concluded that the use of two arcs was necessary, leading to equivalent results as IMRT. Similar to other IMRT/VMAT planning reports, those found that tumors in HN regions, mainly NPC cases, were the most challenging cases.…”

“…The underlying VMAT planning engine in both SmartArc and Oncentra MasterPlan TPS is the same as that developed by RaySearch, and the dose calculation algorithms of pencil beam (PB) convolution and collapsed cone convolution (CCC) were chosen. ( 18 , 19 ) …”

The effect of gantry spacing resolution on plan quality in a single modulated arc optimization

“…( 1 ) It allows simultaneous variation of dose rate, gantry speed, and multileaf collimator (MLC) segments. ( 2 ) The technique promises some dosimetric benefits ( 3 ) together with reduced treatment times ( 1 , 2 , 4 – 6 ) which, in turn, may have significant radiobiological impact. ( 7 – 9 ) …”

A comprehensive formulation for volumetric modulated arc therapy planning

“…[2][3][4] The theoretical framework of VMAT was originally introduced in 1995 by Yu 5 as intensity modulated arc therapy (IMAT), which generated multiple MLC segments per beam angle and requires multiple arcs to deliver. [6][7][8] More practical single arc VMAT algorithms were subsequently developed 9-11 including a representative publication by Otto. 12 Compared to the static beam IMRT problem, the arc optimization problem was considered significantly more complex, due both to the substantially increased beam orientations and the additional machine mechanical constraints such as gantry and MLC mechanical limits.…”