Article

Conformity index: A review

Institut Curie, Orsay, France.
International Journal of Radiation OncologyBiologyPhysics (Impact Factor: 4.26). 03/2006; 64(2):333-42. DOI: 10.1016/j.ijrobp.2005.09.028
Source: PubMed

ABSTRACT

We present a critical analysis of the conformity indices described in the literature and an evaluation of their field of application. Three-dimensional conformal radiotherapy, with or without intensity modulation, is based on medical imaging techniques, three-dimensional dosimetry software, compression accessories, and verification procedures. It consists of delineating target volumes and critical healthy tissues to select the best combination of beams. This approach allows better adaptation of the isodose to the tumor volume, while limiting irradiation of healthy tissues. Tools must be developed to evaluate the quality of proposed treatment plans. Dosimetry software provides the dose distribution in each CT section and dose-volume histograms without really indicating the degree of conformity. The conformity index is a complementary tool that attributes a score to a treatment plan or that can compare several treatment plans for the same patient. The future of conformal index in everyday practice therefore remains unclear.

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Available from: Ge Noël, Jan 27, 2014
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    • "The maximal HD, average Hausdorff Distance, CI pairs and VOI was calculated in a pairwise analysis over all volumes in MilxView (Australian e-Health Research Centre (AEHRC), Australia) [16] [17] (Supplementary Table 2). The JI [18] [19] [20], DICE [4], Hausdorff distance [21] and Kappa (j) statistic [22] [23] outlined in Supplementary Table 1, are metrics commonly used to establish inter-observer variation [6]. JI and DICE values from CERR were verified in 3D Slicer [24] [25] [26] and MILXview and were consistent to within 2 significant figures. "
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    ABSTRACT: In this paper, the highest level of inter- and intra-observer conformity achievable with different treatment planning systems (TPSs), contouring tools, shapes, and sites have been established for metrics including the Dice similarity coefficient (DICE) and Hausdorff Distance. High conformity values, e.g. DICEBreast_Shape=0.99±0.01, were achieved. Decreasing image resolution decreased contouring conformity.
    Full-text · Article · Oct 2015 · Radiotherapy and Oncology
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    • "The reference isodose corresponds to 95% of the prescribed dose. This CN definition was chosen because it simultaneously takes into account irradiation of the target volume and irradiation of healthy tissue [19]. Finally, the homogeneity index (HI) of the PTV was calculated as HI ¼ D2ÀD98 D50 [20]. "
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    ABSTRACT: To determine the optimum combination of treatment parameters between pitch, field width (FW) and modulation factor (MF) for extremity sarcomas in tomotherapy. Six patients previously treated for extremity sarcomas (3 arms and 3 legs) with tomotherapy were included in this study. 288 treatment plans were recalculated, corresponding to all combinations between 2 FW (2.5 and 5 cm), 4 MF (1.5, 2, 2.5 and 3) and 6 pitches (0.215, 0.287, 0.43 and 3 off-axis pitches). The treatment parameters (MF, FW or pitch) are modified between each plan, and the calculation is relaunched for 400 iterations, without modifying the optimisation constraints of the plan under which the patient has been treated. We suggest eliminating the 0.43 pitch and never combining a 0.215 pitch with an MF ≤ 2. We also do not recommend using an MF = 1.5 unless treatment time is an absolute priority over plan quality. We did not see any advantage in using Chen off-axis pitches, except for targets far from the axis (>15 cm) treated with a high pitch. A combination of MF = 2/FW = 5 cm/pitch = 0.287 gives plans of acceptable quality, combined with reduced treatment times. These conclusions are true only for extremity sarcomas treated in 2 Gy/fraction. We have shown that the choice of pitch/MF/FW combination is crucial for the treatment of extremity sarcomas in tomotherapy: some produce good dosimetric quality with a reduced irradiation time, while others may increase the time without improving the quality. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
    Full-text · Article · May 2015 · Physica Medica
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    • "where TV is target volume, ie, PTV, TVRI is the target volume covered by the reference isodose, and VRI is the volume of the reference isodose.28 "
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    ABSTRACT: Background Prone positioning for breast radiotherapy is preferable when the aim is a reduction of the dose to the ipsilateral lung or the heart in certain left-sided cases. Materials and methods In 100 breast cancer cases awaiting postoperative whole-breast radiotherapy, conformal radiotherapy plans were prospectively generated in both prone and supine positions. The axillary nodal region (levels I–III) and internal mammary (IM) lymph-node region in the upper three intercostal spaces were retrospectively contoured. The mean doses to the nodal regions and the volume receiving 25 Gy (V25Gy), V45Gy, and V47.5Gy were compared between the two treatment positions. Results In most cases, the doses to axillary levels I–III and the IM lymph nodes were inadequate, regardless of the treatment position. The nodal doses were significantly lower in the prone than in the supine position. The radiation doses to levels II–III and IM nodes were especially low. The V45Gy and V47.5Gy of the level I axillary lymph nodes were 54.6% and 40.2%, respectively, in the supine, and 3.0% and 1.7%, respectively, in the prone position. In the supine position, only 17 patients (17%) received a mean dose of 45 Gy to the axillary level I nodes. Conclusion The radiation dose to the axillary and IM lymph nodes during breast radiotherapy is therapeutically insufficient in most cases, and is significantly lower in the prone position than in the supine position.
    Full-text · Article · May 2014 · Therapeutics and Clinical Risk Management
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