|Year : 2017 | Volume
| Issue : 2 | Page : 31-36
Comparative Dosimetric Study of Five Field, Seven Field, Nine Field and Eleven Field Intensity-Modulated Radiotherapy for Carcinoma Cervix Treatment Using High Energy Linear Accelerator (Synergy Platform & XIO TPS)
Deepali Bhaskar Patil1, Mukesh Kr Zope2, Rajesh Kumar Singh2
1 Mahavir Cancer Santhan, Phulwarisharif, Patna, Bihar, India
2 Regional Cancer Canter, Indira Gandhi Institute of Medical Sciences, Sheikhpura, Patna - 14, Bihar, India
|Date of Web Publication||11-Dec-2020|
Mukesh Kr Zope
Regional Cancer Center
Source of Support: None, Conflict of Interest: None
Objective: The purpose of this dosimetric study is the targeted dose Homogeneity Index (HI), conformity index (CI) and integral dose comparison of 5. 7, 9 & 11 field Intensity Modulated Radiotherapy (IMRT) for Carcinoma Cervix (Ca Cx) patients.
Material and Methods: Fifteen patients of ca.cx were selected for this study at Radiation Oncology Department, Mahavir Cancer Sansthan, Patna between January 2009 and December 2012. Eight patients had PTV >1500 cc and seven patients had PTV< 1500 cc Dosimetric plans for all 5, 7, 9 & 11-field IMRT plan have been generated for each patient to comparatively evaluate the dosimetric status (HI, CI and Integral Dose) for all the patients.
Results: For PTV (PTV >1500 cc), the three dosimetric parameters had approximate values for all fields (five fields, seven fields and nine fields) IMRT. The CI for the IMRT with nine fields plans was seems to be better than five fields For PTV <1500 cc. The three IMRTs plans were competitive with each other. The nine filed IMRT plans had a CI nearly to 1, better target coverage at the prescription dose, and a better Homogeneity Index.
Conclusion: It can be concluded that IMRT is an effective definitive management tool for Cervical cancer with improved critical organ sparing and excellent dose homogenization in target organs. According to this study as the results from these algorithms differed, significant care should be taken when evaluating treatment plans, as the choice of the beam segment may influence treatment planning as well as clinical results.
Keywords: Intensity-modulated radiotherapy, Cervix Cancer, three-dimensional conformal radiotherapy
|How to cite this article:|
Patil DB, Zope MK, Singh RK. Comparative Dosimetric Study of Five Field, Seven Field, Nine Field and Eleven Field Intensity-Modulated Radiotherapy for Carcinoma Cervix Treatment Using High Energy Linear Accelerator (Synergy Platform & XIO TPS). J Indira Gandhi Inst Med Sci 2017;3:31-6
|How to cite this URL:|
Patil DB, Zope MK, Singh RK. Comparative Dosimetric Study of Five Field, Seven Field, Nine Field and Eleven Field Intensity-Modulated Radiotherapy for Carcinoma Cervix Treatment Using High Energy Linear Accelerator (Synergy Platform & XIO TPS). J Indira Gandhi Inst Med Sci [serial online] 2017 [cited 2021 Dec 7];3:31-6. Available from: http://www.jigims.co.in/text.asp?2017/3/2/31/303143
| Introduction|| |
The purpose of the present study was to investigate the dosimetric differences among equally spaced five fields, seven fields, nine fields & eleven fields intensity- modulated radiotherapy (IMRT, Step & Shoot technique) for the site of Ca Cx. In this study Fast superposition Algorithm was used for all plans.
IMRT is capable of generating complex 3D dose distributions to conform closely to the target volume even in tumors with concave features. With IMRT, the beam intensity (fluence) is optimized using computer algorithms, as it is oriented around the patient. This form of computer algorithm considers not only the target and normal tissue dimensions but also user-defined constraints such as dose limits to targets and critical organs.
Conformity Index, Homogeneity Index, Integral Dose, all have been used to evaluate the external beam plans. Furthermore, Dose Volume Histograms (DVH) for different structures was obtained, to quantify the dose to the other OARs.
| Materials and Method|| |
Fifteen patients of ca.cx were selected for this study at Mahavir Cancer Sansthan, Patna underwent computed tomography simulation, where eight patients had PTV >1500 cc and seven patients had PTV< 1500 cc These patients were immobilized with supine position using thermoplastic mask & CT scan was acquired using 5mm thick contiguous slices, Contrast medium was used for this CT study. CT Images were then transferred to a virtual simulation workstation computer for target contouring.
The contouring of the patient body, target, normal tissue, GTV, CTV and PTV was done as per using RTOG guideline. OAR in this study were Urinary Bladder, Rectum, Right Femoral Head and Left Femoral Head.
For each patients treatment plan were created by using different beam equal space Gantry angles (5, 7, 9, 11 field Gantry angle), 6MV photon energy. Fast superposition algorithm was used for planning with the help of CMS Xio Treatment Planning Systems. For each patients plan isocenter and weight point location were used to centre of Planning Target Volume (PTV). Plan evaluation parameters were used as per the RTOG guidelines:
The Conformity Index (CI) = 1+ Vn/Vt ----------------------
(1) Where Vn & Vt are the volume of normal tissue and target receiving the prescription dose.
Homogeneity Index (HI) = D5% / D95%---------------(2)
Where D5% & D95% are correspond to the dose to 5% and 95% of PTV respectively.
(Note: The CI & HI are ideal when both are numerically equal to one (1))
Integral Dose (ID): defined as the sum of the product of the given dose (Di) and volume of the tissue received the given dose (Vi) and density of that tissue volume (i). This tissue has unit density (equal to water density).
ID = Di * Vi* i-------------------------------------(3)
Where volume of the body exclude the volume (Body-PTV). All the data were taken from differential DVH by using TPS software.
For each patients plan were evaluated with the help of Dose Volume Histogram by using Xio treatment planning system,
| Results|| |
For PTV (PTV >1500 cc), the three dosimetric parameters had approximate values for all fields (five fields, seven fields and nine fields) IMRT. The CI for the IMRT with nine fields plans was seems to be better than five fields
For PTV <1500 cc. The three IMRTs plans were competitive with each other. The nine filed IMRT plans had a CI nearly to 1, better target coverage at the prescription dose, and a better Homogeneity Index. Hence the nine fields IMRT has good target coverage at the prescription dose and Homogeneity Index and approximate CI values as those nearly equal to 1. However the eleven fields IMRT and more have no substantial benefit over nine fields IMRT.
| Conclusion|| |
We compared five filed, seven field, nine field and eleven field (CMS, XiO Planning system) using Conventional, 3DCRT, and IMRT techniques for all cases. Statistical analyses were performed by comparison of mean relative differences with prescribed dose, and Conformity Index and Homogeneity Index for target structures, and are shown in [Table 1], [Table 2] & [Table 3]. CMS, XiO planning system was compared with Direx Accusoft planning system for clinical validation. The fast superposition algorithm showed excellent results for all cases. These tables also show that the fast Fourier algorithm is excellent for all cases. According to this study as the results from these algorithms differed, significant care should be taken when evaluating treatment plans, as the choice of the beam segment may influence treatment planning as well as clinical results.
|Table 1: shows the patient volume selected for this study PTV >1500 CC, PTV<1500cc with help of Dose Volume Histogram|
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|Table 2: shows HI (Homogeneity Index) and Graph (PTV > 1500cc & PTV < 1500cc)|
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- The CI & HI value are almost same for 9 & 11 field IMRT Plan.
- The ID is gradually increasing with increasing fields.
- The results of our study have shown that nine field IMRT is most suitable for large volume tumour like Ca Cx.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3]