Flipping Book

DMLC Movement simulation

6633 Zhao

et al.

: Dosimetric effect of tumor motion in gated SBRT

6633

Movement tracks from

Cyberknife

Zhao et al,

Medical Physics, Vol. 39, No. 11,

actual dose coverage of smaller target is more susceptible to

tumor motion in lung SBRT.

IV. DISCUSSION

The target motion data used in this study were obtained

from Cyberknife treatment where no coaching was adminis-

formity and increases dose gradient, which indirectly causes

CTV underdose as shown in Fig.

6(a)

. In this study our pre-

scription is to cover 95% PTV. In case of a reduced PTV cov-

erage, motion will easily lead CTV underdose. To raise the

prescribed volume coverage, e.g., 99%, will possibly allevi-

ate the problem, however with a cost of increased organ dose.

Same theory applies to increasing margin size.

. 6. Dose distribution map with and without tumor motion for Patients #3 and #6. Solid curves are delineations of PTV (outer-circle) and CTV (inner-circle).

A margin of 5 mm was applied on CTV to obtain PTV. The dose distribution is color-shaded for 100% isodose and above.

Medical Physics, Vol. 39, No. 11, November 2012

6634 Zhao

et al.

: Dosimetric effect of tumor motion in gated SBRT

•

Target motion converted into leaf motion using

PDF from movement tracks

•

Segment per segment modified

•

Recalculation