Image guidance for precise conformal radiotherapy.
OBJECTIVE
To review the state of the art in image-guided precision conformal radiotherapy and to describe how helical tomotherapy compares with the image-guided practices being developed for conventional radiotherapy.


METHODS
Image guidance is beginning to be the fundamental basis for radiotherapy planning, delivery, and verification. Radiotherapy planning requires more precision in the extension and localization of disease. When greater precision is not possible, conformal avoidance methodology may be indicated whereby the margin of disease extension is generous, except where sensitive normal tissues exist. Radiotherapy delivery requires better precision in the definition of treatment volume, on a daily basis if necessary. Helical tomotherapy has been designed to use CT imaging technology to plan, deliver, and verify that the delivery has been carried out as planned. The image-guided processes of helical tomotherapy that enable this goal are described.


RESULTS
Examples of the results of helical tomotherapy processes for image-guided intensity-modulated radiotherapy are presented. These processes include megavoltage CT acquisition, automated segmentation of CT images, dose reconstruction using the CT image set, deformable registration of CT images, and reoptimization.


CONCLUSIONS
Image-guided precision conformal radiotherapy can be used as a tool to treat the tumor yet spare critical structures. Helical tomotherapy has been designed from the ground up as an integrated image-guided intensity-modulated radiotherapy system and allows new verification processes based on megavoltage CT images to be implemented.
Mackie
Thomas Rockwell
TR
Department of Human Oncology, University of Wisconsin, Madison, WI, USA.
Kapatoes
Jeff
J
Ruchala
Ken
K
Lu
Weiguo
W
Wu
Chuan
C
Olivera
Gustavo
G
Forrest
Lisa
L
Tome
Wolfgang
W
Welsh
Jim
J
Jeraj
Robert
R
Harari
Paul
P
Reckwerdt
Paul
P
Paliwal
Bhudatt
B
Ritter
Mark
M
Keller
Harry
H
Fowler
Jack
J
Mehta
Minesh
M
D000818:Animals; D004285:Dogs; D004867:Equipment Design; D006801:Humans; D009038:Motion; D009369:Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D010315:Particle Accelerators / Q000295:instrumentation; D011832:Radiation Injuries / Q000517:prevention & control; D011880:Radiotherapy Planning, Computer-Assisted; D011881:Radiotherapy, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000379:methods*; D011882:Radiotherapy, High-Energy / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation; D014463:Ultrasonography