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S603
ESTRO 36 2017
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image fusion and target definition iPlan RT® (BrainLab,
Munich, Germany) and Eclipse® (Varian, Palo Alto, US)
were used.
Results
Median PTV was 192.9 ml (range 10.1-490.8 ml). RecTV
PET
and RecTV
MRI
showed no major differences concerning
recurrence localization: In-field recurrence was detected
in 64% (9/14), field-border in 29% (4/14) and out-field 7%
(1/14). We were not able to evaluate the RecTV
MRI
of one
patient because the MRI showed no enhancement. Since
FET-PET enables differentiation between vital tumor and
therapeutic associated changes, we compared RecTV
PET
to
GTV
MRI
and GTV
PET
. Median IV of GTV
PET
/RecTV
PET
(4.1 ml,
range: 0-20.8 ml) was larger than GTV
MRI
/RecTV
PET
(2.8 ml,
range: 0-18.1 ml). Accordingly, the median CI showed
higher conformity with 0.19 (range: 0-0.63) and 0.07
(range: 0-0.48), respectively. We calculated median ratio
of IV GTV
PET
/RecTV
PET
to GTV
PET
(44.8%, range: 0-100%) and
the median ratio of IV GTV
MRI
/RecTV
PET
to GTV
MRI
(32.2%,
range: 0-96.6%) to show that the proportion of GTV
PET
developing tumor recurrence tended to be higher than the
proportion of GTV
MRI
.
Conclusion
The patterns of recurrence were similar in MRI and FET-
PET concerning localization related to PTV. Only one
patient showed out-field recurrence, all others developed
in-field/field-border recurrence. Therefore, it is indicated
that current margin concepts are a safe way to define PTV.
However, the GTV
PET
displays remaining tumor more
reliable, and it seems to offer a better prediction of the
localization of later tumor growth than the GTV
MRI
. This
leads to the assumption that dose escalation in the GTV
PET
area might be a worthy subject for future trials.
EP-1111 Cyber knife for Idiopathic Trigeminal
Neuralgia – Novel technique to reduce brainstem dose
P.S. Sridhar
1
, N. Madhusudhan
1
, K. Roopesh
1
, H.
Madhusudhan
2
, R. Satish
3
, G. Swaroop
3
, A. Jerrin
1
, A.
Pichandi
1
, J. Vijaykumar
1
, M. Praveen kumar
1
, S.
Shivkumar
4
, M. Arunakumari
1
, G. Monica
5
, B. Ramesh
1
, K.
Gurunath
1
, B. Ajai kumar
1
1
Health Care Global Enterprises Ltd, Cyberknife-
Radiation oncology, Bangalore, India
2
Sagar Hospital, Neurosurgery, Bangalore, India
3
Sakra hospital, Neurosurgery, Bangalore, India
4
Health Care Global Enterprises Ltd, Radiology,
Bangalore, India
5
Health Care Global Enterprises Ltd, Aneasthesia,
Bangalore, India
Purpose or Objective
Idiopathic trigeminal neuralgia is a functional disorder and
most painful condition known to mankind. Diagnosis is
always clinical, no radiological and functional scans will
be helpful. Medical management and Microvascular
decompression of aberrant vessel, Radiofrequency
ablation, alcohol injection are used extensively with
minimal response. Stereotactic radiosurgery is becoming
popular with good results. Most commonly used is
targeting the trigeminal nerve at its root entry zone. Dose
schedule varies from 66-86Gy single fraction. Brainstem
dose is still a concern which is not addressed
Primary objective is to assess the safety and efficacy of
treating Idiopathic Trigeminal Neuralgia by Stereotactic
Robotic Radiosurgery in Meckels cave area to reduce brain
stem dose.
Material and Methods
12 patents of Idiopathic Trigeminal Neuralgia treated with
Stereotactic Robotic Radiosurgery (Cyberknife) between
Jan 2010 to Dec 2015.6 were female,6 male. Age range 34-
75,mean age 46 .6 were on right side,6 left side. Duration
of symptoms before the treatment range from 2 to 25
years. All patients had one or other form of standard
treatment with unsatisfactory response. All patent
undergo MRI based Cyberknife planning. The affected side
trigeminal nerve is identified ,The part of nerve in Meckels
cave and 3 branches are marked ,brain stem and other
critical structures are contoured .
GTV ranged 260-824mm3,mean 500mm3, Dose
prescription ranged from 70-80% mean 76% and peripheral
dose ranged from 56Gy-70Gy,maximum dose 70Gy to 80Gy
mean 75.4Gy.Brain stem maximum dose ranged between
7.6Gy to 18.3Gy mean 12.7Gy.
Results
All 12 patients had complete response at 6 weeks,2 patent
had recurrence of pain at 8 and 10 months ,10 patents has
altered sensation on treated trigeminal area in the form
of loss of sensation,hyperasthesia.None of them had
brainstem symptoms.
Conclusion
Stereotactic Robotic Radiosurgery (Cyberknife) is 76Gy
single fraction is safe and effective in Idiopathic
Trigeminal Neuralgia .Treating trigeminal nerve in Meckels
cave area and 3 branches will give good pain control with
less dose
to
brainstem.
EP-1112 Dosimetric evaluation in tri-cobalt60 viewray
system for hypofractionated imrt in brain metastases
M. Ferro
1
, E. Placidi
2
, S. Chiesa
1
, F. Cellini
1
, M.
Massaccesi
1
, G.C. Mattiucci
1
, V. Frascino
1
, R. Canna
3
, C.
Masciocchi
4
, L. Azario
5
, V. Valentini
6
, M. Balducci
6
1
Fondazione Policlinico A. Gemelli, Gemelli ART -
Radiation Oncology, Rome, Italy
2
Fondazione Policlinico A. Gemelli, UOC Fisica Sanitaria -
Gemelli ART - Radiation Oncology, Rome, Italy
3
Fondazione Policlinico A. Gemelli, TSRM - Gemelli ART -
Radiation Oncology, Rome, Italy
4
Fondazione Policlinico A. Gemelli, KBO Labs - Gemelli
ART - Radiation Oncology, Rome, Italy
5
Università Cattolica del Sacro Cuore, Institute of
Physics- UOC Fisica Sanitaria- Gemelli ART - Radiation
Oncology, Rome, Italy
6
Università Cattolica del Sacro Cuore, Gemelli ART -
Radiation Oncology, Rome, Italy
Purpose or Objective
Meridian is a system equipped with 3 rotating 60Co sources
for IMRT and magnetic resonance imaging (MRI) for real-
time vision of target volume (TV). The aim of this in silico
study was to evaluate the dosimetric impact of this
technology when hypofractionated IMRT is used to treat
brain metastases (BM).
Material and Methods
Treatment plans were performed with a monoisocentric
IMRT technique using different number of beams. Margin
to PTV was 3 millimeters as normally used for LINAC plans.
Total dose prescribed according to ICRU 83 was 25.5 Gy in
3 fractions.
TV coverage, Paddick dose conformity (CI), homogeneity
(HI), dose to organ at risk (OAR) and to normal brain were
analyzed for all plans.
Results
Sixteen brain metastases were evaluated and 80 plans
were analyzed. No significative statistical difference was
observed in HI when beams number was increased (p >
0.5). The CI did not change between different beams
arrangements. No significant statistical difference was
observed when beam's number was correlated with TV or
sparing normal tissues.
Conclusion
IMRT plans using the tri-60Co ViewRay System are feasible
according to ICRU 83. The real-time vision of target
volume by MR could allow to reduce the PTV margin saving
the normal tissue. An ongoing study is comparing ViewRay
plans with 3 millimeters to PTV with plans in which no
margin is added and PTV is the equal to GTV.