Dosimetric comparison between coplanar and non coplanar field radiotherapy for ethmoid sinus cancer

<p>Abstract</p> <p>Background</p> <p>To compare non coplanar field (NCF) with coplanar field (CF) -intensity-modulated radiotherapy (IMRT) planning for ethmoid cancer.</p> <p>Methods</p> <p>Seven patients treated with NCF IMRT for ethmoid cancer were studied. A CF IMRT optimization was prepared with the same constraints as for the NCF treatment. The maximum point doses (D max) obtained for the different optic pathway structures (OPS) should differ no more than 3% from those achieved with the NCF IMRT plan. The distribution of the dose in the target volume and in the critical structures was compared between the two techniques, as well as the Conformity (CI) and the Homogeneity Indexes (HI) in the target volume.</p> <p>Results</p> <p>We noted no difference between the two techniques in the OPS for the D1, D2, and D5%, in the inner ear and controlateral lens for the average Dmax, in the temporo-mandibular joints for the average mean dose, in the cord and brainstem for the average D1%. The dose-volume histograms were slightly better with the NCF treatment plan for the planning target volume (PTV) with a marginally better HI but no impact on CI. We found a great improvement in the PTV coverage with the CF treatment plan for two patients with T4 tumors.</p> <p>Conclusion</p> <p>IMRT is one of the treatment options for ethmoid cancer. The PTV coverage is optimal without compromising the protection of the OPS. The impact of non coplanar versus coplanar set up is very slight.</p

Développement d'un système de cartographie par luminescence stimulée optiquement (applications aux contrôles des traitements en radiothérapie avec modulation d'intensité et aux contrôles des faisceaux de protons de haute énergie)

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Mean dose volume histogram in the planning target volume for the coplanar field CF (grey) and non coplanar field technique NCF (black)

<p><b>Copyright information:</b></p><p>Taken from "Dosimetric comparison between coplanar and non coplanar field radiotherapy for ethmoid sinus cancer"</p><p>http://www.ro-journal.com/content/2/1/35</p><p>Radiation Oncology (London, England) 2007;2():35-35.</p><p>Published online 18 Sep 2007</p><p>PMCID:PMC2072954.</p><p></p> Minimum and maximum doses of the study group are represented by dotted lines

Maximum doses in optic pathways, respectively optic chiasma (a), ipsilateral optic nerve (b) and controlateral optic nerve (c)

<p><b>Copyright information:</b></p><p>Taken from "Dosimetric comparison between coplanar and non coplanar field radiotherapy for ethmoid sinus cancer"</p><p>http://www.ro-journal.com/content/2/1/35</p><p>Radiation Oncology (London, England) 2007;2():35-35.</p><p>Published online 18 Sep 2007</p><p>PMCID:PMC2072954.</p><p></p> For each patient (Px), the maximum dose for coplanar field CF (grey) and for non coplanar field NCF (black) is represented

Conformal index CI for each patient in the coplanar field CF (grey) and non coplanar field NCF (black) technique

<p><b>Copyright information:</b></p><p>Taken from "Dosimetric comparison between coplanar and non coplanar field radiotherapy for ethmoid sinus cancer"</p><p>http://www.ro-journal.com/content/2/1/35</p><p>Radiation Oncology (London, England) 2007;2():35-35.</p><p>Published online 18 Sep 2007</p><p>PMCID:PMC2072954.</p><p></p> CI is defined as follows: CI = (TV/V) × (TV/V) TV: Treated Volume is the volume of PTV1 receiving the prescribed dose (95%); Vis the volume of PTV; Vis the volume enclosed in the isodose 95

Homogeneity index (HI) for each patient in the coplanar field CF (grey) and non coplanar field NCF (black) technique

<p><b>Copyright information:</b></p><p>Taken from "Dosimetric comparison between coplanar and non coplanar field radiotherapy for ethmoid sinus cancer"</p><p>http://www.ro-journal.com/content/2/1/35</p><p>Radiation Oncology (London, England) 2007;2():35-35.</p><p>Published online 18 Sep 2007</p><p>PMCID:PMC2072954.</p><p></p> HI is defined as the difference between D1 and D99% divided by the prescribed dose. A perfect homogeneity would be reached with a zero index

PTV mean dose volume histogram in the T4 subgroup for the coplanar field CF (grey) and non coplanar field technique NCF (black)

<p><b>Copyright information:</b></p><p>Taken from "Dosimetric comparison between coplanar and non coplanar field radiotherapy for ethmoid sinus cancer"</p><p>http://www.ro-journal.com/content/2/1/35</p><p>Radiation Oncology (London, England) 2007;2():35-35.</p><p>Published online 18 Sep 2007</p><p>PMCID:PMC2072954.</p><p></p> Minimum and maximum doses of the study group are represented by dotted lines

Dose distribution in optic pathways for each patient (Px); optic chiasma (a), ipsilateral optic nerve (b) and controlateral optic nerve (c) respectively

<p><b>Copyright information:</b></p><p>Taken from "Dosimetric comparison between coplanar and non coplanar field radiotherapy for ethmoid sinus cancer"</p><p>http://www.ro-journal.com/content/2/1/35</p><p>Radiation Oncology (London, England) 2007;2():35-35.</p><p>Published online 18 Sep 2007</p><p>PMCID:PMC2072954.</p><p></p> The dose difference in Gy between non coplanar field NCF and coplanar field CF (D NCF – D CF) is represented in terms of D1%, D2%, and D5% corresponding to the doses in 1, 2 and 5 % of the volumes respectively. This means that when the difference is negative, the dose to optic pathways is higher when using coplanar field technique