SCIENTIFIC ADVANCES

Enhancing Treatment Accuracy and Precision

A goal in modern radiotherapy is to shape the radiation field closely to the tumor in 3-dimensions to minimize the risk of radiation damage to the normal tissues surrounding the tumor. In some tumor sites, this is complicated by motion of both the tumor and normal tissue, such as the movement of both normal lung and lung tumors during breathing. Special imaging and computer programs are being developed to accommodate this motion. Paul Keall, Ph.D., and his colleagues at Stanford University have developed a method to obtain 4-dimensional images of the lungs from a spiral computed tomography (CT) imaging scan. It involves assigning each CT “slice” to one of eight phases of the breathing cycle. The distortion of the image is greatly reduced by this process. Most commercial CT machines now incorporate this technique.

Weiss K, Wijesooriya K, Dill SV, Keall PJ. Tumor and normal tissue motion in the thorax during respiration: Analysis of volumetric and positional variations using 4D CT.Int J Radiat Oncol Biol Phys2007:67;296–307.
http://www.ncbi.nlm.nih.gov/pubmed/17189078

Vedam SS, Keall PJ, Kini VR, Mostafavi H, Shukla MP, Mohan R. Acquiring a four-dimensional computed tomography dataset using an external respiratory signal. Phys Med Biol2003:48;45–62.
http://www.ncbi.nlm.nih.gov/pubmed/12564500