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Potential of tomotherapy for total scalp treatment
Jay Locke1, Daniel A Low, Todd Grigireit
1Mallinckrodt Institute of Radiology, St. Louis, MO, USA. locke@radonc.wustl.edu
Purpose:
Total scalp radiotherapy is required in a variety of clinical situations. We compared conventional lateral photon-electron (LPE) technique with tomotherapy (intensity-modulated radiotherapy [IMRT]).
Methods And Materials:
A patient with Merkel cell carcinoma was treated at our institution using conventional treatment techniques. Treatment plans were conducted using conventional three-dimensional treatment planning and IMRT. The clinical target volume included the entire scalp tissue volumes to the surface of underlying cranial bone, as well as superficial and deep neck nodes in the bilateral neck. To provide a consistent comparison between the IMRT and three-dimensional conventional treatment plans, the dose distributions were normalized such that 90% of the target volumes received the prescription dose.
Results:
Examination of our results revealed an acceptable dose-volume histogram and adequate coverage of the clinical target volume using the conventional LPE technique. The IMRT plan provided a more homogeneous dose to the target volume; however, critical structure doses were uniformly higher than for the conventional treatment plan.
Conclusions:
The IMRT plan resulted in a substantial dose to the lens, brain, and orbit, making it clinically unacceptable compared with the LPE technique. Overall, the LPE technique was superior.