Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2012 Dec 21;18(2):101-6.
doi: 10.1016/j.rpor.2012.10.003. eCollection 2012.

Treatment planning evaluation of sliding window and multiple static segments technique in intensity modulated radiotherapy

Khalid Iqbal  1 , Muhammad Isa  2 , Saeed Ahmad Buzdar  2 , Kent Aallen Gifford  3 , Muhammad Afzal  2
Affiliations

Treatment planning evaluation of sliding window and multiple static segments technique in intensity modulated radiotherapy

Khalid Iqbal et al. Rep Pract Oncol Radiother. .

Abstract

Background: The demand of improved dose conformity of the tumor has been increased in radiation therapy with the advent of recent imaging facilities and efficient computer technologies.

Aim: We compared the intensity modulated radiotherapy (IMRT) plans delivered with the sliding window (SW IMRT) and step and shoot (SS IMRT) techniques.

Materials and methods: Thirteen patients were planned on 15 MV X-ray for five, seven, nine and thirteen beams direction making the dose constraints analogous. Eclipse treatment planning system with Helios inverse planning software, and Linear Accelerator Varian 2100 C/D with 120 multileaf collimators (MLCs) were used. Gamma analysis was applied to the data acquired with the MapCheck 2™ for different beam directions plan in the sliding window and step and shoot technique to meet the 95% pass criteria at 3%/3 mm. The plans were scrutinized using D mean, D max, D1%, D95%, dose uniformity index (UI), dose conformity index (CI), dose homogeneity index (HI) and monitor units (MUs).

Results: Our data show comparable coverage of the planning target volume (PTV) for both the sliding window and step and shoot techniques. The volume of PTV receiving the prescription dose was 99.8 ± 0.05% and the volume of PTV receiving the maximum dose was 107.6 ± 2.5% in both techniques. Bladder and rectum maximum mean doses for the sliding window and step and shoot plans were 38.1 ± 2.6% and 42.9 ± 10.7%. Homogeneity index (HI) for both techniques was 0.12 ± 0.02 and 0.13 ± 0.02, uniformity index (UI) was 1.07 ± 0.02 and 108 ± 0.01 and conformity index at 98% isodose (CI 98%) was 0.96 ± 0.005 and 0.96 ± 0.005 for the sliding window and step and shoot techniques, respectively, and MUs were 10 ± 12% lower in the step and shoot compared to the sliding window technique.

Conclusion: All these factors indicate that coverage for PTV was nearly identical but dose to organs-at-risk (OARs) was lower in the step and shoot technique.

Keywords: Conformity index; Homogeneity index; Intensity modulated radiation therapy; Organs-at-risk; Uniformity index.

PubMed Disclaimer

Figures

Fig. 1
Fig. 1
MapCHECK 2™ gamma analysis used for both prostate IMRT techniques.
Fig. 2
Fig. 2
Comparison of DVH curves of PTV for all fields using SS IMRT and SW IMRT.
Fig. 3
Fig. 3
Comparison of OAR DVH for all fields using SS IMRT and SW IMRT.
Fig. 4
Fig. 4
Comparison of both techniques for different volume of partial bladder and partial rectum.
Fig. 5
Fig. 5
Average MU assessment of individual patient for different field with SW IMRT and SS IMRT.
See this image and copyright information in PMC

References

    1. Blanco A.I., Chao K.S. vol. 3. Lippincott Williams and Wilkins Healthcare; New York: 2002. (Intensity modulated radiation therapy and protection of normal tissue function in head and neck cancer in principles and practice of radiation oncology).
    1. Hande B.A., Metin G., Cemile C., Nadir K., Kayihan E. Comparsion of dose distribution and organ at risk (OAR) doses in conventional tangential technique (CTT) and IMRT plans with different number of bean in left sides breast cancer. Rep Pract Oncol Radiother. 2011;16:102–197. - PMC - PubMed
    1. Malhotra Harish K., Sanjay R., Avadhani J.S., deBoer S., Podgorsak M.B. Technical and dosimetric considerations in IMRT treatment planning for large target volumes. J Appl Clin Med Phys. 2005;6(4) - PMC - PubMed
    1. Xia P., Ting J.Y., Orton C.G. Segmental MLC is superior to dynamic MLC for IMRT delivery. Med Phys. 2007;26:73–75. - PubMed
    1. Williams P.C. Review article IMRT: delivery techniques and quality assurance. Br J Radiol. 2003;76:766–776. - PubMed

LinkOut - more resources