DASSIM-RT is likely to become the method of choice over conventional IMRT and VMAT for delivery of highly conformal radiotherapy.

Department of Radiation Oncology, Stanford University, Stanford, California 94305-5847.
Medical Physics (Impact Factor: 3.01). 02/2013; 40(2):020601. DOI: 10.1118/1.4773025
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Available from: Colin G Orton, Sep 19, 2014
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    ABSTRACT: Purpose: Conventional volumetric modulated arc therapy (VMAT) discretizes the angular space into equally spaced control points during planning and then optimizes the apertures and weights of the control points. The aperture at an angle in between two control points is obtained through interpolation. This approach tacitly ignores the differential need for intensity modulation of different angles. As such, multiple arcs are often required, which may oversample some angle(s) and undersample others. The purpose of this work is to develop a segmentally boosted VMAT scheme to eliminate the need for multiple arcs in VMAT treatment with improved dose distribution and∕or delivery efficiency.Methods: The essence of the new treatment scheme is how to identify the need of individual angles for intensity modulation and to provide the necessary beam intensity modulation for those beam angles that need it. We introduce a "demand metric" at each control point to decide which station or control points need intensity modulation. To boost the modulation at selected stations, additional segments are added in the vicinity of the selected stations. The added segments are then optimized together with the original set of station or control points as a whole. The authors apply the segmentally boosted planning technique to four previously treated clinical cases: two head and neck (HN) cases, one prostate case, and one liver case. The proposed planning technique is compared with conventional one-arc and two-arc VMAT.Results: The proposed segmentally boosted VMAT technique achieves better critical structure sparing than one-arc VMAT with similar or better target coverage in all four clinical cases. The segmentally boosted VMAT also outperforms two-arc VMAT for the two complicated HN cases, yet with ∼30% reduction in the machine monitor units (MUs) relative to two-arc VMAT, which leads to less leakage∕scatter dose to the patient and can potentially translate into faster dose delivery. For the less challenging prostate and liver cases, similar critical structure sparing as the two-arc VMAT plans was obtained using the segmentally boosted VMAT. The benefit for the two simpler cases is the reduction of MUs and improvement of treatment delivery efficiency.Conclusions: Segmentally boosted VMAT achieves better dose conformality and∕or reduced MUs through effective consideration of the need of individual beam angles for intensity modulation. Elimination of the need for multiple arcs in rotational arc therapy while improving the dose distribution should lead to improved workflow and treatment efficacy, thus may have significant implication to radiation oncology practice.
    Medical Physics 05/2013; 40(5):050701. DOI:10.1118/1.4802748 · 3.01 Impact Factor
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    ABSTRACT: Liver stereotactic body radiation therapy (SBRT) is a feasible treatment method for the nonoperable, patient with early-stage liver cancer. Treatment planning for the SBRT is very important and has to consider the simulation accuracy, planning time, treatment efficiency effects etc. The modified dynamic conformal arc (MDCA) technique is a 3-dimensional conformal arc planning method, which has been proposed for liver SBRT planning at our center. In this study, we compared the MDCA technique with the RapidArc technique in terms of planning target volume (PTV) coverage and sparing of organs at risk (OARs). The results show that the MDCA technique has comparable plan quality to RapidArc considering PTV coverage, hot spots, heterogeneity index, and effective liver volume. For the 5 PTVs studied among 4 patients, the MDCA plan, when compared with the RapidArc plan, showed 9% more hot spots, more heterogeneity effect, more sparing of OARs, and lower liver effective volume. The monitor unit (MU) number for the MDCA plan is much lower than for the RapidArc plans. The MDCA plan has the advantages of less planning time, no-collision treatment, and a lower MU number.
    Medical Dosimetry 01/2014; 40(1). DOI:10.1016/j.meddos.2014.07.002 · 0.95 Impact Factor
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    ABSTRACT: Purpose To propose a nonisocentric treatment strategy as a special form of station parameter optimized radiation therapy, to improve sparing of critical structures while preserving target coverage in breast radiation therapy. Methods and Materials To minimize the volume of exposed lung and heart in breast irradiation, we propose a novel nonisocentric treatment scheme by strategically placing nonconverging beams with multiple isocenters. As its name suggests, the central axes of these beams do not intersect at a single isocenter as in conventional breast treatment planning. Rather, the isocenter locations and beam directions are carefully selected, in that each beam is only responsible for a certain subvolume of the target, so as to minimize the volume of irradiated normal tissue. When put together, the beams will provide an adequate coverage of the target and expose only a minimal amount of normal tissue to radiation. We apply the nonisocentric planning technique to 2 previously treated clinical cases (breast and chest wall). Results The proposed nonisocentric technique substantially improved sparing of the ipsilateral lung. Compared with conventional isocentric plans using 2 tangential beams, the mean lung dose was reduced by 38% and 50% using the proposed technique, and the volume of the ipsilateral lung receiving ≥20 Gy was reduced by a factor of approximately 2 and 3 for the breast and chest wall cases, respectively. The improvement in lung sparing is even greater compared with volumetric modulated arc therapy. Conclusions A nonisocentric implementation of station parameter optimized radiation therapy has been proposed for breast radiation therapy. The new treatment scheme overcomes the limitations of existing approaches and affords a useful tool for conformal breast radiation therapy, especially in cases with extreme chest wall curvature.
    International journal of radiation oncology, biology, physics 03/2014; 88(4):920–926. DOI:10.1016/j.ijrobp.2013.12.029 · 4.18 Impact Factor
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