Comparing Radiation Treatments Using Intensity-Modulated Beams, Multiple Arcs, and Single Arcs

Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
International journal of radiation oncology, biology, physics (Impact Factor: 4.26). 04/2010; 76(5):1554-62. DOI: 10.1016/j.ijrobp.2009.04.003
Source: PubMed


A dosimetric comparison of multiple static-field intensity-modulated radiation therapy (IMRT), multiarc intensity-modulated arc therapy (IMAT), and single-arc arc-modulated radiation therapy (AMRT) was performed to evaluate their clinical advantages and shortcomings.
Twelve cases were selected for this study, including three head-and-neck, three brain, three lung, and three prostate cases. An IMRT, IMAT, and AMRT plan was generated for each of the cases, with clinically relevant planning constraints. For a fair comparison, the same parameters were used for the IMRT, IMAT, and AMRT planning for each patient.
Multiarc IMAT provided the best plan quality, while single-arc AMRT achieved dose distributions comparable to those of IMRT, especially in the complicated head-and-neck and brain cases. Both AMRT and IMAT showed effective normal tissue sparing without compromising target coverage and delivered a lower total dose to the surrounding normal tissues in some cases.
IMAT provides the most uniform and conformal dose distributions, especially for the cases with large and complex targets, but with a delivery time similar to that of IMRT; whereas AMRT achieves results comparable to IMRT with significantly faster treatment delivery.

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Available from: Cedric X Yu, Jan 02, 2014
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    • "There has been a hypothesized benefit in reducing secondary malignancies due to the reduction of interleaf scatter [12]. Additionally, arc therapy with multiple arcs allows for flexibility of dosage, increased sparing of normal tissue, and increased conformality [13,14]. VMAT, specifically multiple arcs, has been shown in head and neck cancer to provide better PTV dose homogeneity and similar or better OAR sparing [15,16]. "
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    ABSTRACT: Intensity modulated arc therapy (IMAT) is a form of intensity modulated radiation therapy (IMRT) that delivers dose in single or multiple arcs. We compared IMRT plans versus single-arc field (1ARC) and multi-arc fields (3ARC) IMAT plans in high-risk prostate cancer. Sixteen patients were studied. Prostate (PTV P ), right pelvic (PTV RtLN ) and left pelvic lymph nodes (PTV LtLN ), and organs at risk were contoured. PTV P , PTV RtLN , and PTV LtLN received 50.40 Gy followed by a boost to PTV B of 28.80 Gy. Three plans were per patient generated: IMRT, 1ARC, and 3ARC. We recorded the dose to the PTV, the mean dose (D MEAN ) to the organs at risk, and volume covered by the 50% isodose. Efficiency was evaluated by monitor units (MU) and beam on time (BOT). Conformity index (CI), Paddick gradient index, and homogeneity index (HI) were also calculated. Average Radiation Therapy Oncology Group CI was 1.17, 1.20, and 1.15 for IMRT, 1ARC, and 3ARC, respectively. The plans' HI were within 1% of each other. The D MEAN of bladder was within 2% of each other. The rectum D MEAN in IMRT plans was 10% lower dose than the arc plans (p < 0.0001). The GI of the 3ARC was superior to IMRT by 27.4% (p = 0.006). The average MU was highest in the IMRT plans (1686) versus 1ARC (575) versus 3ARC (1079). The average BOT was 6 minutes for IMRT compared to 1.3 and 2.9 for 1ARC and 3ARC IMAT (p < 0.05). For high-risk prostate cancer, IMAT may offer a favorable dose gradient profile, conformity, MU and BOT compared to IMRT.
    06/2013; 31(2):104-10. DOI:10.3857/roj.2013.31.2.104
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    • "However, both brainstem and spinal cord received lower mean Dmax in IMRT plans. This concurs with results reported by Tang et al. [26]. "
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    ABSTRACT: Dosimetric comparisons between RapidArc (RA) and conventional Intensity-Modulated Radiation Therapy (IMRT) techniques for nasopharyngeal carcinoma (NPC) were performed to address differences in dose coverage of the target, sparing of organs-at-risk (OARs), delivery of monitor units (MUs) and time, to assess whether the RA technique was more beneficial for treatment of NPC. Eight NPC patients (Stages I-IV), who had completed RA treatment, were selected for this study. Computed tomography data sets were re-planned using 7-fields fixed beam IMRT. Quantitative measurements of dose-endpoint values on the dose-volume histograms were carried out for evaluation of: (i) dose homogeneity (D(5%) - D(95%)); (ii) degree of conformity (CI(95%)); (iii) tumor control probability (TCP); (iv) doses to OARs; (v) normal tissue complication probability (NTCP); (vi) treatment time; and (vii) MUs. RA plans achieved better dose conformity and TCP in planning target volumes (PTVs). Target dose homogeneity was not as high as for IMRT plans. Doses to tempero-mandibular joints, clavicles, parotid glands and posterior neck, and their NTCPs were significantly lower in RA plans (P < 0.05). Mean doses to the brainstem and spinal cord were slightly lower in IMRT plans. RA plans allowed for a mean reduction in MUs by 78% (P = 0.006), and a four-fold reduction in treatment delivery times, relative to IMRT plans. RA plans showed superior, or comparable, target coverage and dose conformity in PTVs, but at the expense of inferior dose homogeneity. RA plans also achieved significant improvements in dose reduction to OARs and healthy tissue sparing. A significant reduction in treatment delivery time for RA treatment technique was also noted.
    Journal of Radiation Research 11/2012; 54(3). DOI:10.1093/jrr/rrs111 · 1.80 Impact Factor
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    • "Compared to conventional intensity-modulated radiation therapy (IMRT), where beams are delivered at only a few (e.g. 7) beam angles and a complicated set of beam apertures are designed at each beam angle, VMAT can deliver dose distributions of similar or better quality [6] [7] [8] [9] [10] [11] [12] [13] [14] [15]. In addition, VMAT significantly shortens treatment times, completing treatment in a single rotation of the gantry. "
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    ABSTRACT: Radiation therapy is one of the most commonly used treatment modalities for cancer. Its purpose is to deliver prescribed radiation doses to cancerous targets using high energy radiation beams while sparing nearby healthy organs. The treatment planning process of ra-diotherapy is an optimization problem, where beam parameters, such as directions, shapes, and intensities, can be adjusted in simulations to yield desired dose distributions. This can be applied under the recently developed volumetric modulated arc therapy (VMAT) setup which involves the use of a full-rotation trajectory of the beam about the patient along with a multi-leaf collimator for beam shape sculpt-ing, with notable advantages in shortened treatment time. Treatment plan optimization in this setting, however, can be quite complicated due to constraints arising from the equipment involved. We intro-duce a variational model in the VMAT setup for the optimization of 1 beam shapes and intensities under these constraints. We apply a bi-nary level-set strategy to represent beam shapes and a fast sweeping technique to satisfy beam intensity variation limits. The result is a flow-based shape optimization algorithm that guarantees constraint satisfaction and energy decrease for the generation of improved treat-ment plans in VMAT. Simulations of clinical cases are included to validate our algorithm.
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