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

Article (PDF Available)inInternational journal of radiation oncology, biology, physics 76(5):1554-62 · April 2010with30 Reads
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
    • "To our knowledge, a dosimetric study comparing VMAT and proton planning for high-risk prostate cancer had yet to be performed. Recently, the VMAT has become a popular delivery option over IMRT for prostate cancer since VMAT requires a smaller number of monitor units (MUs) and shorter delivery time while providing conformal dose distributions [2, 15, 16]. Since both the proton therapy and VMAT techniques are currently available as treatment options in externalbeam radiation therapy, it is essential to address the dosimetric advantages and disadvantages of one technique over the other. "
    [Show abstract] [Hide abstract] ABSTRACT: Purpose: The main objective of this study was to compare the dosimetric quality of volumetric modulated arc therapy (VMAT) with that of proton therapy for high-risk prostate cancer. Patients and Materials: Twelve patients with high-risk prostate cancer previously treated with uniform scanning proton therapy (USPT) were included in this study. Proton planning was done using the XiO treatment planning system (TPS) with two 1800 parallel-opposed lateral fields. The VMAT planning was done using the RapidArc technique with two arcs in the Eclipse TPS. The VMAT and proton plans were calculated using the anisotropic analytical algorithm and pencil-beam algorithm, respectively. The calculated VMAT and proton plans were then normalized so that at least 95% of the planning target volume (PTV) received the prescription dose. The dosimetric evaluation was performed by comparing the physical dose-volume parameters, which were obtained from the VMAT and proton plans. Results: The average difference in the PTV doses between the VMAT and proton plans was within ±1%. On average, the proton plans produced a lower mean dose to the rectum (18.2 Gy (relative biological effectiveness [RBE]) vs. 40.0 Gy) and bladder (15.8 Gy (RBE) vs. 30.1 Gy), whereas the mean dose to the femoral heads was lower in the VMAT plans (28.3 Gy (RBE) vs. 19.3 Gy). For the rectum and bladder, the proton plans always produced lower (better) results in the low- and medium-dose regions, whereas the results were case-specific in the high-dose region. Conclusion: For the same target coverage, in comparison to the VMAT technique, the USPT is significantly better at sparing the rectum and bladder, especially in the low- and medium-dose regions, but results in a higher femoral head dose.
    Full-text · Article · May 2014
    • "[3] Recently, VMAT has gained widespread acceptance as the technique of choice for prostate cancer patients undergoing EBRT because VMAT can achieve IMRT quality dose distributions with reduction in the treatment delivery time and decrement in the number of monitor units. [3][4][5]Several authors have carried out studies for prostate cancer comparing VMAT versus IMRT planning [6][7][8][9][10][11][12]as well as single arc (SA) versus double arc (DA) [10][11][12]within VMAT planning. Furthermore, the results in previous studies were evaluated mostly in terms of physical volume and physical dose, [6][7][8][9][10][11][12]and there are no radiobiological data available for VMAT planning techniques for prostate cancer. "
    [Show abstract] [Hide abstract] ABSTRACT: The radiobiological models describe the effects of the radiation treatment on cancer and healthy cells, and the radiobiological effects are generally characterized by the tumor control probability (TCP) and normal tissue complication probability (NTCP). The purpose of this study was to assess the radiobiological impact of RapidArc planning techniques for prostate cancer in terms of TCP and normal NTCP. A computed tomography data set of ten cases involving low-risk prostate cancer was selected for this retrospective study. For each case, two RapidArc plans were created in Eclipse treatment planning system. The double arc (DA) plan was created using two full arcs and the single arc (SA) plan was created using one full arc. All treatment plans were calculated with anisotropic analytical algorithm. Radiobiological modeling response evaluation was performed by calculating Niemierko's equivalent uniform dose (EUD)-based Tumor TCP and NTCP values. For prostate tumor, the average EUD in the SA plans was slightly higher than in the DA plans (78.10 Gy vs. 77.77 Gy; P = 0.01), but the average TCP was comparable (98.3% vs. 98.3%; P = 0.01). In comparison to the DA plans, the SA plans produced higher average EUD to bladder (40.71 Gy vs. 40.46 Gy; P = 0.03) and femoral heads (10.39 Gy vs. 9.40 Gy; P = 0.03), whereas both techniques produced NTCP well below 0.1% for bladder (P = 0.14) and femoral heads (P = 0.26). In contrast, the SA plans produced higher average NTCP compared to the DA plans (2.2% vs. 1.9%; P = 0.01). Furthermore, the EUD to rectum was slightly higher in the SA plans (62.88 Gy vs. 62.22 Gy; P = 0.01). The SA and DA techniques produced similar TCP for low-risk prostate cancer. The NTCP for femoral heads and bladder was comparable in the SA and DA plans; however, the SA technique resulted in higher NTCP for rectum in comparison with the DA technique.
    Full-text · Article · Mar 2014
    • "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]. "
    [Show abstract] [Hide abstract] 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.
    Full-text · Article · Jun 2013
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