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Evaluating the therapeutic dose distribution of intensity-modulated radiation therapy for head and neck with cone-beam computed tomography image: a methodological study.

Zhang GS, Huang SM, Chen C, Xu SK, Zhang DD, Deng XW - Biomed Res Int (2014)

Bottom Line: Also setup deviations were simulated to evaluate the ability of the CBCT-based calculation for detecting the dose errors caused by positioning deviation.The gamma comparison between CBCT- and FBCT-based dose computations showed that the pass rates of (2%, 2 mm) criteria were better than 97.60 ± 0.83% and 97.74 ± 2.08% in the phantom and 10 NPC cases.When setup deviation was introduced into CBCT-based dose calculation, the gamma pass rate significantly decreased while the volumetric doses of the targets and some normal organs exhibited different changes compared to the original plan.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in Southern China, Collaborative Innovation Center for Cancer Medicine, 651 Dong Feng Road East, Guangzhou 510060, China.

ABSTRACT
An approximate correction method for the CT value-electron density curve of CBCT was established, through comparison and fitting with FBCT images, and applied to evaluate the therapeutic dose of IMRT. The precision of using CBCT for plan calculation was validated by comparing the dose distribution between CBCT- and FBCT-based IMRT plans. Also setup deviations were simulated to evaluate the ability of the CBCT-based calculation for detecting the dose errors caused by positioning deviation. The gamma comparison between CBCT- and FBCT-based dose computations showed that the pass rates of (2%, 2 mm) criteria were better than 97.60 ± 0.83% and 97.74 ± 2.08% in the phantom and 10 NPC cases. When setup deviation was introduced into CBCT-based dose calculation, the gamma pass rate significantly decreased while the volumetric doses of the targets and some normal organs exhibited different changes compared to the original plan. Our results validated the above CT value-electron density correction which reduced the difference between CBCT- and FBCT-based IMRT plan calculation for NPC to less than 2%. Online CBCT-based dose calculation can be used to reflect and evaluate the dose distribution discrepancy caused by setup deviation and structure changes during the treatment, ensuring more effective quality control of IMRT treatment.

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Comparison of dose distribution and gamma values on the transversal plane at the isocenter position between the two plans based on FBCT and CBCT images for three patients (P1–P3). On the right (the third column) are the gamma comparison results (2%, 2 mm) of these two plans. The red areas denote pixels with gamma values greater than 1.
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fig2: Comparison of dose distribution and gamma values on the transversal plane at the isocenter position between the two plans based on FBCT and CBCT images for three patients (P1–P3). On the right (the third column) are the gamma comparison results (2%, 2 mm) of these two plans. The red areas denote pixels with gamma values greater than 1.

Mentions: Figure 2 compared the dose distribution in CBCT- and FBCT-based plans on the transversal plane of three randomly selected patients. The figure shows that the differences in the shape and range of isodose lines between the CBCT-based and FBCT-based plans were extremely slight. The points with a larger deviation were primarily concentrated at the edges of the images and in the vicinity of the air chambers of the nasopharyngeal cavity, with dose differences less than 2%.


Evaluating the therapeutic dose distribution of intensity-modulated radiation therapy for head and neck with cone-beam computed tomography image: a methodological study.

Zhang GS, Huang SM, Chen C, Xu SK, Zhang DD, Deng XW - Biomed Res Int (2014)

Comparison of dose distribution and gamma values on the transversal plane at the isocenter position between the two plans based on FBCT and CBCT images for three patients (P1–P3). On the right (the third column) are the gamma comparison results (2%, 2 mm) of these two plans. The red areas denote pixels with gamma values greater than 1.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4150500&req=5

fig2: Comparison of dose distribution and gamma values on the transversal plane at the isocenter position between the two plans based on FBCT and CBCT images for three patients (P1–P3). On the right (the third column) are the gamma comparison results (2%, 2 mm) of these two plans. The red areas denote pixels with gamma values greater than 1.
Mentions: Figure 2 compared the dose distribution in CBCT- and FBCT-based plans on the transversal plane of three randomly selected patients. The figure shows that the differences in the shape and range of isodose lines between the CBCT-based and FBCT-based plans were extremely slight. The points with a larger deviation were primarily concentrated at the edges of the images and in the vicinity of the air chambers of the nasopharyngeal cavity, with dose differences less than 2%.

Bottom Line: Also setup deviations were simulated to evaluate the ability of the CBCT-based calculation for detecting the dose errors caused by positioning deviation.The gamma comparison between CBCT- and FBCT-based dose computations showed that the pass rates of (2%, 2 mm) criteria were better than 97.60 ± 0.83% and 97.74 ± 2.08% in the phantom and 10 NPC cases.When setup deviation was introduced into CBCT-based dose calculation, the gamma pass rate significantly decreased while the volumetric doses of the targets and some normal organs exhibited different changes compared to the original plan.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in Southern China, Collaborative Innovation Center for Cancer Medicine, 651 Dong Feng Road East, Guangzhou 510060, China.

ABSTRACT
An approximate correction method for the CT value-electron density curve of CBCT was established, through comparison and fitting with FBCT images, and applied to evaluate the therapeutic dose of IMRT. The precision of using CBCT for plan calculation was validated by comparing the dose distribution between CBCT- and FBCT-based IMRT plans. Also setup deviations were simulated to evaluate the ability of the CBCT-based calculation for detecting the dose errors caused by positioning deviation. The gamma comparison between CBCT- and FBCT-based dose computations showed that the pass rates of (2%, 2 mm) criteria were better than 97.60 ± 0.83% and 97.74 ± 2.08% in the phantom and 10 NPC cases. When setup deviation was introduced into CBCT-based dose calculation, the gamma pass rate significantly decreased while the volumetric doses of the targets and some normal organs exhibited different changes compared to the original plan. Our results validated the above CT value-electron density correction which reduced the difference between CBCT- and FBCT-based IMRT plan calculation for NPC to less than 2%. Online CBCT-based dose calculation can be used to reflect and evaluate the dose distribution discrepancy caused by setup deviation and structure changes during the treatment, ensuring more effective quality control of IMRT treatment.

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