Page 66 - ARNM-2-4

Advances in Radiotherapy
& Nuclear Medicine Different approaches for the computation of BED

Table 1. Tumor locations, target volumes, and corresponding equivalent sphere diameters (d ) for the considered stereotactic
es
body radiation therapy cases
Tumor location Number of cases V (cm ) V (cm ) V (cm ) d (cm) d (cm) d (cm)
3
3
3
PTV,min PTV,max PTV,aver es,min es,max es,aver
LLL 11 16.2 55.8 33.1 3.1 4.7 3.9
LUL 7 16.6 58.5 27.4 3.2 4.8 3.7
RLL 6 34.5 101.7 67.4 4.0 5.8 5.0
RML 3 10.7 21.1 14.9 2.7 3.4 3.0
RUL 24 7.0 58.4 28.6 2.4 4.8 3.7
Note that des denotes the diameter of a sphere with volume VPTV.
Abbreviations: LLL: Left lower lobe; LUL: Left upper lobe; RLL: Right lower lobe; RML: Right middle lobe; RUL: Right upper lobe.

A B

Figure 2. Computed D mean and σ in (A) and (B), respectively. The presented plots indicate that the D mean and σ of the studied DCA plans exceeded those of
the VMAT plans.
Abbreviations: DCA: Dynamic conformal arc; VMAT: Volumetric modulated arc therapy.

A B

Figure 3. BED mean in (A) and BED nud in (B) for the considered SBRT cases. The displayed BEDs were computed for α = 0.35 Gy and alpha/beta ratio of
−1
10 Gy. Although the DCA plans were characterized by greater values of BED mean , the corresponding VMAT plans had a larger average BED nud.
Abbreviation: BED: Biologically effective dose; DCA: Dynamic conformal arc; SBRT: Stereotactic body radiation therapy.

the VMAT plans, the sample mean of BED was only According to the approach realized in Velocity
nud
2% and 5% smaller than that of BED mean for α = 0.15 Gy and RaySearch, the DCA plans should be preferred in
−1
and α = 0.35 Gy , respectively (Figure 3 and Table 2). The terms of their higher BED mean than the VMAT plans.
−1
observed smaller difference between BED mean and BED Conversely, if the BED is computed by averaging the
nud
for the studied VMAT plans was due to the smaller variance survival probabilities in different voxels, the resulting
of the target dose compared with that in the DCA plans. BED for the studied VMAT plans was on average higher
nud
than that for the corresponding DCA plans (for α = 0.35
4.4. Clinical implications of the results Gy ). Fourteen DCA plans (27% of all plans) had BED
−1
nud
The clinical ramifications of this work can be elucidated < 100 Gy. Conversely, all the studied VMAT plans were
with the help of Figure 3 and Table 2. characterized by BED nud ≥100 Gy. The differences between
Volume 2 Issue 4 (2024) 6 doi: 10.36922/arnm.4826