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anterior descending artery (LAD), and the thyroid, were
compared to those of non-coplanar 3D-CRT and coplanar
VMAT. A p value < 0.05, derived using the paired Student’s
t-test, was considered to reflect a significant difference.
Results
Figure 1-B shows the averaged dose-volume histograms for
all 24 patients in terms of their PTVs and OARs. The Table
summarizes the mean dose volume indices for the targets
and OARs, and the MU for each technique. Significant
difference was not observed in doses to the PTV. When
DWA was employed, the average V
20Gy
, V
10Gy
, and V
5Gy
to
the ipsilateral lung; the average V
10Gy
and V
5Gy
to the heart;
the D
2%
for the planning organ at risk volume of the LAD
(PRV_LAD); and the V
50%
of, and the mean dose to the
ipsilateral breast, were significantly lower than those of
non-coplanar 3D-CRT and coplanar VMAT. The average D
2%
to the contralateral breast and the V
5Gy
to the
contralateral lung did not differ significantly among the
techniques. Furthermore, the mean prescribed MU for
DWA was 486.22 MU, which was only 9.8% higher than that
for non-coplanar 3D-CRT (442.67 MU) (p < 0.05).
Conclusion
The use of DWA for APBI improved the dose distribution
compared to that of non-coplanar 3D-CRT and coplanar
VMAT; this may reduce the risk of toxicity without
prolonging treatment time.
PO-0838 Treatment planning for the MR-linac: plan
quality compared with current clinical practice
A.J.A.J. Van de Schoot
1
, C. Carbaat
1
, B. Van Triest
1
, T.M.
Janssen
1
, J.J. Sonke
1
1
The Netherlands Cancer Institute, Department of
Radiation Oncology, Amsterdam, The Netherlands
Purpose or Objective
Clinical introduction of the MR-linac (MRL) involves
treatment planning using Monaco (Elekta AB, Stockholm,