ESTRO 36 Abstract Book

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S995 ESTRO 36
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To assess the accuracy of the immobilization devices, we
immobilized the CIRS Radiosurgery Head Phantom with
hidden target by BoS cast and headring, respectively. Then
we implemented the imaging guidance by using bony
structure. Compare to the localization method, the CIRS
Radiosurgery Head Phantom with hidden target was
immobilized by headring followed by implementation of
the imaging guided process using bony structure and
fiducial markers, respectively. The overall couch shifts
were performed by the radiation therapists, the deviation
with respect to the proton isocenter was measured by
using the hidden target with paired t-test and 3D vector .
Results
For BoS cast and headring, the deviations (mm) were
0.54±0.68 and 0.48±0.28 (p ＝0.412) in right-left (RL),
0.22±0.28 and -0.11±0.34 (p ＝0.186) in superior-inferior
(SI), -0.30±0.11 and -0.15±0.22 (p ＝0.167) in anterior-
posterior (AP) directions, and 0.85±0.42 and 0.60±0.32 (p
＝0.017) in 3D vector, respectively. For the imaging-
guided localization method, the deviations (mm) of bony
structure and fiducial markers were -0.29±0.65 and
0.19±0.34 (p＝0.002) in RL, -0.14±0.53 and 0.01±0.12 (p＝
0.126) in SI, -0.01±0.42 and 0.10±0.25 (p＝0.219) in AP
directions, and 0.84±0.48 and 0.41±0.23 (p ＝0.004) in 3D
vector, respectively.
Conclusion
Translational deviations were not statistically significant
between the immobilization methods or imaging-guided
landmarks. However, there were significant differences in
3D vector. The results of our study demonstrated that
headring and fiducial markers can achieve good accuracy
for brain cancer in proton stereotactic radiosurgery (P-
SRS).
EP-1814 Is AIO belly board device advantageous in all
irradiated rectal cancer patients?
D. Hempel1, J. Mandrosz1, J. Topczewska-Bruns1, D.
Kazberuk 1, A. Szmigiel-Trzcińska1, R. Maksim1, M.
Konopka-Filippow1, T. Filipowski1, M.Z. Wojtukiewicz 2, E.
Sierko 2
1 Comprehensive Cancer Center, Department of
Radiotherapy, Białystok, Poland
2 Comprehensive Cancer Center, Department of Clinical
Oncology, Białystok, Poland
Purpose or Objective
A prospective study was undertaken to compare prone on
flat table position vs on 'All in one” belly board device (AIO
BBD) by assessment of patients’ preferences, irradiated
small bowel and bladder volume (SB-V, B-V) as well as
setup accuracy in rectal cancer patients (RCPs).
Material and Methods
Material and methods: Fifteen RCPs scheduled to
irradiation on pelvic area (preoperative, n = 11 and
postoperative, n = 4) were scanned twice: in prone on flat
table and prone on AIO BBD position. Patients were asked
to complete an institution-developed questionnaire
concerning their perception of the positioning. Using 3D
planning system the dose-volume histograms (DVHs) for SB
and B were compared in two treatment plans. Setup
accuracy of bony anatomy and pelvic organs were
analyzed in MV-portals and X-ray volume imaging (XVI)
procedures, respectively for on AIO BBD – positioned
patients (n = 14).
Results
AIO BBD was accepted as immobilization method by
majority of RCPs and provided better DVHs for SB than
prone on flat table position. The setup reproducibility was
good, within tolerance limit for patients with BMI ≤ 29
kg/m2 . However, two patients with obesity regarded AIO
BBD as uncomfortable and they presented mean setup
shifts out of tolerance limit in Y axis – 5.9 mm. The another
obese patient was disqualified from irradiation on AIO BBD
due to more beneficial DVH for SB in prone on flat table
position.
Conclusion
The AIO BBD should be recommended as immobilization
method in RCPs with BMI ≤ 29 kg/m2. Immobilization of
obese patients on AIO BBD may be uncomfortable for
them, cause worse dose-volume distribution in SB and /or
result in unacceptable setup shifts.
EP-1815 Technical aspects and setup irradiation of rats
using a clinical accelerator
V. SACCO1, A. Viale1, B. Noris Chiorda1, C. Sini2, G.
Salvadori1, C. Fiorino2, N. Di Muzio 1, C. Cozzarini1
1Nuova Fondazione Centro San Raffaele, Radiotherapy,
Milano, Italy
2Nuova Fondazione Centro San Raffaele, Medical Physics,
Milano, Italy
Purpose or Objective
A preclinical study having the aim to test the possible
hormone protective role on radio-induced inflammation of
the bladder wall has been conceived in our centre using a
rat model.
This kind of application usually requires a dedicated
microlinac to deliver radiotherapy to small animals.
However, this device is not available in our hospital.
The purpose of this study is to set up a system allowing to
irradiate rats by a clinical accelerator, with a positioning
system that ensures the reproducibility of the treatment.
Material and Methods
Eight male rats were surgically catheterized,
anesthetized, immobilized within small containers in
plastic material, and positioned on the clinical accelerator
bed (RapidArc® - Varian Medical Systems). The isocentre
was placed on the abdomen of the animals, with a source-
to-skin distance (SSD) of 100 cm. A kilovoltage cone-beam
CT was acquired in order to image the bladder, previously
filled by injecting Gastrografin. The treatment field was
defined by assigning an expansion of 3 mm to the bladder
on the coronal projection of the cone-beam CT. After
positioning of a bolus of 1 cm on the abdomen of the
animals, a single fraction of 20 Gy was delivered with 6 MV
photons. A single fraction treatment was decided to avoid
the need of repeated irradiations that would complicate
organisation issues.
Results
The animals were successfully treated and well tolerated
radiotherapy, being alive after 6 months of irradiation.
The shift difference between the cone beam CT
reconstruction and the manual correction of the
radiotherapist was calculated. The values measured in the
group of animals were expressed in three dimensional
shifts (along X,Y,Z IEC coordinates, in cm), as mean values
± standard deviations: X = -0.13 ±0.10; Y = 0.13±0.08; Z=
0.13±0.12.