Doses delivered to normal brain under different treatment protocols at Brookhaven National Laboratory Page: 2 of 10
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Table 1 summarizes the doses delivered to the normal brain of glioblastoma patients treated
at BNL under different protocols. The volume-averaged BNCT dose delivered under protocols from
Group I, II, III and IV ranged from 1.9 to 2.6 Gy-Eq, 2.2 to 2.6 Gy-Eq, 3.3 to 4.1 Gy-Eq and 4.4 to
5.0 Gy-Eq, respectively. Doses to sensitive sites of the brain (e.g. basal ganglia, thalamus, optic
chiazm) outside of the target volume were kept below 7.5 Gy.-Eq.
Isodose contours shown in the left pannel of Figure 1 illustrate the totoal dose distribution
in a patient treated under a protocol from Group I in a lateral position, which resulted in a very high
difference between ipsilateral and contralateral distribution of the dose to the normal structures of
the brain. This patient received the following average doses: ipsilateral hemisphere 4.0 Gy-Eq (2.5
Gy-Eq high-LET, and 1.5 Gy-Eq low-LET); contralateral hemisphere 1.0 Gy-Eq (0.4 Gy-Eq high-
LET, and 0.6 Gy-Eq low-LET dose). Left panel of Figure 2 shows Dose-volume histograms of total
dose and its components in the brain of this patient. It is noteworthy that only small fraction of the
brain received doses close to the prescribed peak dose of 10.5 Gy-Eq.
The dose 'distribubon-ychngs considcrbiy for brains of patients irradiated-bilaterally. The
right panel of Figure 1 illustrates the total dose distribution in a patient treated under Protocol #4b
(Group IV). For this patient the irradiation time of ipsi-/contralateral hemispheres was divided 70/30.
The corresponding dose-volume histograms are shown in the right panel of Figure 2. Although the
average total brain dose increased significantly, only a relatively small fraction of the brain received
doses greater than 6 Gy-Eq. The following volume-averaged doses were delivered to the
hemispheres during this bilateral irradiation: ipsilateral hemisphere 7.0 Gy-Eq (4.8 Gy-Eq high-
LET, and 2.2 Gy-Eq low-LET); contralateral hemisphere 3.9 Gy-Eq.(2.2 Gy-Eq high-LET, and 1.7
Gy-Eq low-LET dose).
During BNCT, the patient's brain is exposed to a complex mixture of radiations. Interactions
between biological effects of different components of this radiation on normal tissues are not known.
Therefore, it is extremely difficult to extrapolate the results of animal experiments to predict safe
doses to the human brain. As discussed by Coderre et. al.  in this volume, because of the great
differences in human versus dog brain volumes and in the gradients in the dose distribution, dose
volume hisotgrams rather than peak doses should be compared. Also, because the contributions of
different types of dose components change with depth in the tissue, use of physical dose alone may
be misleading. Expression of the total dose in weighted units such as Gy-Eq presents a better
alternative in spite of intristic problems with the accuracy of the RBE and CBE factors.
Comparison of the BNCT doses to which our patients have been exposed to considerably
higher doses that were proved to be save in, both dog BNCT studies  and conventional
radiotherapy , as well as the absence of any accute adverse effect of BNCT in our patients so far,
suggest that further dose escalation to improve the outcome of BNCT may be possible.
This work was supported by the U.S. Department of Energy contract # DE-AC02-76CH00016.
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Capala, J.; Coderre, J.A. & Liu, H.B. Doses delivered to normal brain under different treatment protocols at Brookhaven National Laboratory, article, December 31, 1996; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc689797/m1/2/: accessed April 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.