566 / 1096
S551
ESTRO 36
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reported to increase intestinal motility. DKT is composed
of three medical herbs (ginger, ginseng radix, Japanese
pepper) and maltose powder. The purpose of this study
was to investigate the effect of DKT on rectal volume
during prostate IMRT prospectively.
Material and Methods
The institutional review board approved this study and
written informed consent was obtained from all patients.
We divided consecutive 30 non-metastatic (cT1cN0 to
cT3bN0) prostate cancer patients into two groups. 15
patients were orally administered 15 grams of DKT per day
from one month before IMRT until the last day of the
treatment (DKT group). The remaining 15 were not
administered DKT (non-DKT group). The prescribed
radiation dose was 78 Gy in 39 fractions for 7.5 weeks to
the prostatic gland and proximal one-third or entire
seminal vesicle according to their stratified recurrence
risk. Kilo-voltage computed tomographic image (KV-CT) by
linear accelerator (Trilogy, Varian Co.) was taken for
three-dimensional matching set-up before each treatment
session. Each KV-CT was sent to a radiation treatment
planning workstation (Pinnacle 3, Phillips Medical Systems
Co.) and rectal volume of anal-sided 8cm length was then
measured. Calculated rectal volumes of the DKT group
were compared to those of the non-DKT group.
Administration of laxative agent, tubal gas suction or
colon irrigation was done depending on residual rectal
content before radiation.
Results
Total of 1,170 KV-CT were evaluated. Rectal volumes of
DKT and non-DKT groups were 48.79-63.46 (mean 54.69
+/- 4.00) cm
3
and 52.41-142.57 (mean 81.37 +/- 16.36)
cm
3
, respectively (p < 0.01). Adverse effects associated
with DKT use such as appetite loss, liver dysfunction or
interstitial pneumonia were not noted.
Conclusion
DKT appears to be useful in reducing rectal volume and
intra-fractional volume variance which would help prevent
radiation proctitis or rectal bleeding in prostate curative
radiotherapy. Longer follow-up with a larger patient
population is desired.
PO-1000 Immobilisation systems for brain treatment:
are individual head supports needed for stable fixation?
S. Meessen
1
, F. De Beer
1
, P. Van Haaren
1
, D. Schuring
1
1
Catharina Hospital Eindhoven, Department of Radiation
Oncology, Eindhoven, The Netherlands
Purpose or Objective
For stereotactic treatment of brain metastases, good
fixation of the patient is necessary to enable the use of
small PTV margins and reduce the volume of healthy brain
tissue receiving high doses. These fixations should prevent
significant intrafaction movement, and reduce the
interfraction rotations. The purpose of this study was to
compare three different fixation systems, two with
individual head supports and one with standard head
support, and to evaluate which of these systems was best
suited for stereotactic brain treatments.
Material and Methods
Patients receiving brain RT were treated with either one
of three different fixation systems (Orfit Industries, see
figure 1): a hybrid mask combined with (a) an individual
head support vacuum bag (n=20); (b) a Thermofit
individual head support(n=17); (c) a standard 3D head
support with cranial stop (n=10). All patients received a
correction protocol and were imaged at least 3 times
during the treatment course using an Elekta XVI CBCT,
both before and at the end of the treatment fraction. All
scans were registered on bony anatomy and translations
and rotations were recorded and analysed. For the three
different fixation systems the mean (M), systematic (Σ)
and random (σ) errors were determined over the patient
population for the intrafraction translations and rotations,
and interfraction rotations.
Results
Figure 2 shows the systematic and random errors of the
intrafraction translations (a,b) and interfraction rotations
(c,d) of the three different fixation systems. Intrafraction
translations were small for all systems, with maximum
deviations generally lower than 1 mm for all fractions, and
a systematic and random error both in the order of 0.3
mm. No statistically significant differences were found
between the vacuum bag and Thermofit system, while the
3D head support showed a slight improvement for the
systematic errors compared to the individually moulded
head supports. Intrafraction rotations were typically in
the order of 0.2
⁰
, and no differences were observed
between the three groups. The systematic and random
errors of the interfraction rotations were in the order of
1
⁰
and 0.6
⁰
for all systems, with no significant differences
between the three fixation systems, and maximum
rotations of up to 4
⁰
were observed occasionally.