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Is daily CT image guidance necessary for nasal cavity and nasopharyngeal radiotherapy: an investigation based on helical tomotherapy.

ABSTRACT: In order to analyze the magnitude of set up errors corrected by Helical TomoTherapy Mega-Voltage CT on a daily or weekly basis and their impact on the delivered dose to the tumor and organs at risk (OAR), the setup errors of 6 nasal cavity and 4 nasopharyngeal cancer patients who were treated with Helical Tomotherapy for 25-33 fractions were retrospectively analyzed. Each patient had MVCT guided repositioning for all fractions of treatment. The new dose volume histogram (DVH) and equivalent uniform dose (EUD) for planning target volume (PTV) and OARs were calculated for hypothetical situations where no imaging guidance (IG) or once weekly image guidance (WIG) took place. The mean total set up error if treated without daily IG was 3.6+/-1.0 mm, which can be reduced to 1.7+/-0.6 mm if a WIG was performed. The geometrical uncertainties from the absence of image guidance resulted in a reduction of mean PTV EUD dose by 2.1+/-1.0 %, which can be reduced to 1.4+/-1.0 % with WIG. The EUD of OARs increased 1.8+/-2.0 Gy or 0.8+/-1.3 Gy without or with WIG respectively. Without daily IG, the mean patient position uncertainty has relatively small impacts on the mean PTV and OAR dosimetry, which can be further reduced approximately by half using a WIG. On the other hand, because of the large variance, with low probability, substantial deviation from the original planned dosimetry may occur without IG. Therefore, daily MVCT is preferred as an important safety measure in the IMRT.

SUBMITTER: Sheng K

PROVIDER: S-EPMC5721532 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature

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Is daily CT image guidance necessary for nasal cavity and nasopharyngeal radiotherapy: an investigation based on helical tomotherapy.

Sheng Ke K Chow Jennifer J Hunter Grant G Larner James J Read Paul P

Journal of applied clinical medical physics 20080128 1

In order to analyze the magnitude of set up errors corrected by Helical TomoTherapy Mega-Voltage CT on a daily or weekly basis and their impact on the delivered dose to the tumor and organs at risk (OAR), the setup errors of 6 nasal cavity and 4 nasopharyngeal cancer patients who were treated with Helical Tomotherapy for 25-33 fractions were retrospectively analyzed. Each patient had MVCT guided repositioning for all fractions of treatment. The new dose volume histogram (DVH) and equivalent unif ...[more]

PMID: 18449163

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Project description:BackgroundLeft-sided post-mastectomy radiotherapy (PMRT) certainly precedes some radiation dose to the cardiopulmonary organs causing many side effects. To reduce the cardiopulmonary dose, we created a new option of the breathing adapted technique by using abdominal compression applied with a patient in deep inspiration phase utilizing shallow breathing. This study aimed to compare the use of abdominal compression with shallow breathing (ACSB) with the free breathing (FB) technique in the left-sided PMRT.Materials and methodsTwenty left-sided breast cancer patients scheduled for PMRT were enrolled. CT simulation was performed with ACSB and FB technique in each patient. All treatment plans were created on a TomoTherapy planning station. The target volume and dose, cardiopulmonary organ volume and dose were analyzed. A linear correlation between cardiopulmonary organ volumes and doses were also tested.ResultsRegarding the target volumes and dose coverage, there were no significant differences between ACSB and FB technique. For organs at risk, using ACSB resulted in a significant decrease in mean (9.17 vs 9.81 Gy, p<0.0001) and maximum heart dose (43.79 vs 45.45 Gy, p = 0.0144) along with significant reductions in most of the evaluated volumetric parameters. LAD doses were also significantly reduced by ACSB with mean dose 19.24 vs 21.85 Gy (p = 0.0036) and the dose to 2% of the volume (D2%) 34.46 vs 37.33 Gy (p = 0.0174) for ACSB and FB technique, respectively. On the contrary, the lung dose metrics did not show any differences except the mean V5 of ipsilateral lung. The positive correlations were found between increasing the whole lung volume and mean heart dose (p = 0.05) as well as mean LAD dose (p = 0.041) reduction.ConclusionsThe ACSB technique significantly reduced the cardiac dose compared with the FB technique in left-sided PMRT treated by Helical TomoTherapy. Our technique is uncomplicated, well-tolerated, and can be applied in limited resource center.

Project description:Purpose:Because of the poor prognosis for high-grade glioma (HGG) patients, it is important to increase the dose of the tumor to improve the efficacy while minimizing the dose of organs at risk (OARs). Thus, we evaluated the potential dosimetric gains of helical tomotherapy (HT) versus intensity-modulated radiotherapy (IMRT) or volume-modulated arc therapy (VMAT) for high-grade glioma (HGG). Methods:A total of 42 HGG patients were retrospectively selected who had undergone helical tomotherapy; then, IMRT and VMAT plans were generated and optimized for comparison after contouring crucial neuronal structures for neurogenesis and neurocognitive function. IMRT and VMAT were optimized with the Eclipse treatment planning system (TPS) (Version 11.0.31) and HT using TomoTherapy Hi-Art Software (Version 2.0.7) (Accuray, Madison, WI, USA). All three techniques were optimized for simultaneously delivering 60?Gy to planning target volume (PTV) 1 and 50-54?Gy to PTV2. We also analyzed the homogeneity index (HI) and conformity index (CI) of PTVs and organ at risk (OAR) sparing. Results:There was no significant difference in the PTV coverage among IMRT, VMAT, or HT. As for the HI, HT plans (PTV1 HI: 0.09 ± 0.03, PTV2 HI: 0.17 ± 0.05) had the best homogeneity when compared to IMRT plans (PTV1 HI: 0.10 ± 0.04, PTV2 HI: 0.18 ± 0.04) and VMAT plans (PTV1 HI: 0.11 ± 0.03, PTV2 HI: 0.20 ± 0.03). The CI value of HT (PTV1 CI: 0.98 ± 0.03, PTV2: 0.98 ± 0.05) was closest to the optimal value. Except for the IMRT and VMAT groups, there were statistically significant differences between the other two groups of the CI values in both PTV1 and PTV2. The other comparison values were statistically significant except for the optic nerve, and VMAT had the best sparing of the optic chiasm. The mean and max doses of OARs declined significantly in HT. Conclusions:For high-grade glioma patients, HT had superior outcomes in terms of PTV coverage and OAR sparing as compared with IMRT/VMAT.

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Is daily CT image guidance necessary for nasal cavity and nasopharyngeal radiotherapy: an investigation based on helical tomotherapy.

Publications

Is daily CT image guidance necessary for nasal cavity and nasopharyngeal radiotherapy: an investigation based on helical tomotherapy.

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