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
. 2014 Jul;39(3):164-8.
doi: 10.4103/0971-6203.139005.

Impact of repeat computerized tomography replans in the radiation therapy of head and neck cancers

Virendra Bhandari  1 , Prapti Patel  1 , Om Prakash Gurjar  2 , Krishna Lal Gupta  1
Affiliations

Impact of repeat computerized tomography replans in the radiation therapy of head and neck cancers

Virendra Bhandari et al. J Med Phys. 2014 Jul.

Abstract

Anatomical changes can occur during course of head-and-neck (H and N) radiotherapy like tumor shrinkage, decreased edema and/or weight loss. This can lead to discrepancies in planned and delivered dose increasing the dose to organs at risk. A study was conducted to determine the volumetric and dosimetric changes with the help of repeat computed tomography (CT) and replanning for selected H and N cancer patients treated with IMRT plans to see for these effects. In 15 patients with primary H and N cancer, a repeat CT scan after 3(rd) week of radiotherapy was done when it was clinically indicated and then two plans were generated on repeat CT scan, actual plan (AP) planned on repeat CT scan, and hybrid plan (HP), which was generated by applying the first intensity-modulated radiation therapy (IMRT) plan (including monitoring units) to the images of second CT scan. Both plans (AP and HP) on repeat CT scan were compared for volumetric and dosimetric parameter. The mean variation in volumes between CT and repeat CT were 44.32 cc, 82.2 cc, and 149.83 cc for gross tumor volume (GTV), clinical target volumes (CTV), and planning target volume (PTV), respectively. Mean conformity index and homogeneity index was 0.68 and 1.07, respectively for AP and 0.5 and 1.16, respectively for HP. Mean D95 and D99 of PTV was 97.92% (standard deviation, SD 2.32) and 93.4% (SD 3.75), respectively for AP and 92.8% (SD 3.83) and 82.8% (SD 8.0), respectively for HP. Increase in mean doses to right parotid, left parotid, spine, and brainstem were 5.56 Gy (Dmean), 3.28 Gy (Dmean), 1.25 Gy (Dmax), and 3.88 Gy (Dmax), respectively in HP compared to AP. Repeat CT and replanning reduces the chance of discrepancies in delivered dose due to volume changes and also improves coverage to target volume and further reduces dose to organ at risk.

Keywords: Actual plan; homogeneity index; hybrid plan; replanning.

PubMed Disclaimer

Conflict of interest statement

Conflict of Interest: None declared.

Figures

Figure 1
Figure 1
Volume changes between first scan and repeat scan
Figure 2
Figure 2
Comparison of dose distribution in AP and HP
Figure 3
Figure 3
DVH of (a) actual plan and (b) hybrid plan
See this image and copyright information in PMC

References

    1. Ozyigit G, Yang T, Chao KS. Intensity-modulated radiation therapy for head and neck cancer. Curr Treat Options Oncol. 2004;5:3–9. - PubMed
    1. Hansen EK, Bucci MK, Quivey JM, Weinberg V, Xia P. Repeat CT imaging and replanning during the course of IMRT for head-and-neck cancer. Int J Radiat Oncol Biol Phys. 2006;64:355–62. - PubMed
    1. Bhide SA, Davies M, Burke K, McNair HA, Hansen V, Barbachano Y, et al. Weekly volume and dosimetric changes during chemoradiotherapy with intensity-modulated radiation therapy for head and neck cancer: A prospective observational study. Int J Radiat Oncol Biol Phys. 2010;76:1360–8. - PubMed
    1. Nishimura Y, Shibata T, Nakamatsu K, Kanamori S, Koike R, Okubo M, et al. A two-step intensity-modulated radiation therapy method for nasopharyngeal cancer: The Kinki University experience. Jpn J Clin Oncol. 2010;40:130–8. - PubMed
    1. Cannon DM, Lee NY. Recurrence in region of spared parotid gland after definitive intensity-modulated radiotherapy for head and neck cancer. Int J Radiat Oncol Biol Phys. 2008;70:660–5. - PubMed