14
Fig. 2 Coronal and transaxial view of the intensity modulated radiotherapy (IMRT) dose distribution for same
patient in Fig. 1. Isodose lines in orange: 41.5 Gy, dark green: 30 Gy, light green: 20 Gy, pink: 10 Gy, brown: 5 Gy
the GTV, PTV, and OARs localized for a patient with distal esoph-
ageal cancer planned for neoadjuvant CRT.For 3DCRT, the usual beam arrangement is anterior field with
a left and right posterior oblique pair or opposed right anterior
and left posterior obliques. Beam arrangements that avoid
OARs should be chosen. For intensity modulated radiotherapy
(IMRT), the beam angle is less important and an evenly dis-
tributed 5–9 beam arrangement can be used. Anterior-posterior
opposing pair can be used for palliation if the spinal cord dose
limit is not exceeded.Isodose distribution and dose volume histogram of RT plans
should be examined to ensure adequate coverage of targets and
conforming dose limits to OARs (Figs. 2 and 3 ).
At least 95% of the PTV should receive the prescribed dose,
and maximum total dose to PTV should not exceed the prescrip-
tion dose by more than 7%. Tolerance dose to OARs should not be
exceeded. If OARs constraints cannot be met, alternate beam
arrangement or changing to intensity modulated radiotherapy
(IMRT) may help. Use of image-guided radiotherapy may help to
reduce the margin required for PTV. Verification before RT and
online imaging during RT are desirable to ensure accuracy of
patient positioning and setup.3.5 Beam
Arrangement
3.6 Acceptance
Criteria for RT
Planning
Dora L. W. Kwong and K. O. Lam