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
. 2008 Oct;33(4):136-40.
doi: 10.4103/0971-6203.44472.

Tumor delineation: The weakest link in the search for accuracy in radiotherapy

C F Njeh  1
Affiliations

Tumor delineation: The weakest link in the search for accuracy in radiotherapy

C F Njeh. J Med Phys. 2008 Oct.

Abstract

Radiotherapy is one of the most effective modalities for the treatment of cancer. However, there is a high degree of uncertainty associated with the target volume of most cancer sites. The sources of these uncertainties include, but are not limited to, the motion of the target, patient setup errors, patient movements, and the delineation of the target volume. Recently, many imaging techniques have been introduced to track the motion of tumors. The treatment delivery using these techniques is collectively called image-guided radiation therapy (IGRT). Ultimately, IGRT is only as good as the accuracy with which the target is known. There are reports of interobserver variability in tumor delineation across anatomical sites, but the widest ranges of variations have been reported for the delineation of head and neck tumors as well as esophageal and lung carcinomas. Significant interobserver variability in target delineation can be attributed to many factors including the impact of imaging and the influence of the observer (specialty, training, and personal bias). The visibility of the target can be greatly improved with the use of multimodality imaging by co-registration of CT with a second modality such as magnetic resonance imaging (MRI) and/or positron emission tomography. Also, continuous education, training, and cross-collaboration of the radiation oncologist with other specialties can reduce the degree of variability in tumor delineation.

Keywords: Image-guided therapy; radiation therapy; tumor delineation.

PubMed Disclaimer

Conflict of interest statement

Conflict of Interest: None declared.

Figures

Figure 1
Figure 1
Some of the steps in radiotherapy that can be represented by links in a chain; treatment accuracy will be limited by the weakest link in the chain
Figure 2
Figure 2
Illustration of the difference in precision and accuracy. The center of the circle represents the true value and the black dots represent the measured values (edited from Njeh and Langton with permission)
Figure 3
Figure 3
Illustration of the effect of high conformal radiation therapy and geometric miss due to delineation The shaded circle is the delineated CTV and the open circle is the true CTV. (a) Is the traditional 3D conventional RT with big margin and (b) Is the conformal RT with small margin and shows a portion of the tumor not covered by the prescribed dose
See this image and copyright information in PMC

References

    1. ICRU report 62. International commission on Radiation Units and Measurements. Prescribing, recording and reporting photon beam therapy. 1999. Supplement to ICRU report 5.
    1. Langen KM, Jones TL. Organ motion and its management. Int J Radiat Oncol Biol Physics. 2001;50:265–78. - PubMed
    1. Booth JT, Zavgorodni SF. Set up error and organ motion uncertainty: A review. Australas Phys Eng Sci Med. 1999;22:29–47. - PubMed
    1. Jaffray DA, Yan D, Wong JW. Managing geometric uncertainty in conformal intensity-modulated radiation therapy. Semin Radiat Oncol. 1999;9:4–19. - PubMed
    1. Booth JT, Zavgorodni SF. Modeling the dosimetric consequences of organ motion at CT imaging on radiotherapy treatment planning. Phys Med Biol. 2001;46:1369–77. - PubMed