On the use of VIP Gel dosimetry

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On the use of VIP Gel dosimetry
in HDR brachytherapy

• L Petrokokkinos1,2, A Moutsatsos2, P Karaiskos2,
• V Kouridou3, E Pantelis4, P Papagiannis2 and I
  Seimenis5

1. Nuclear Particle Physics Section, Physics
Department, University of Athens, Greece 2.
Medical Physics Laboratory, Medical School,
University of Athens, Greece 3. Anticancer
Hospital of Athens St. Savvas, Athens,
Greece 4. CyberKnife centre, Iatropolis -
Magnitiki Tomografia, Athens, Greece 5. Medical
Diagnostic Centre Ayios Therissos, Nicosia, Cyprus
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Gel dosimeters an absolute dosimeter?
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Gel preparation irradiation
Irradiation?192Ir Varisource (5 mm)?Sk
12861.42 cGycm2/h (3 unc.)?Varian HDR remote
afterloader?Single dwell position?tir 283.5
s?11.15 Gy _at_ 1 cm
VIP formulation?8 w/v N-Vinylpyrrolidone?7.5
w/v gelatin?4 w/v N,N-methylenebisacrylamide?
0.0008 w/v Copper Sulfate ?0.007 w/v Ascorbic
acid?Hyperpure water (gt18 MO?cm)
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MR readout
Scanning parameters?1.5 T Philips Gyroscan
NT?Quadrature RF receiver coil?3D CPMG
sequence?20 equidistant echoes, 40 ms
step?TE120 ms, TR2000 ms?Axially
reconstructed slices?0.75 mm slice
thickness?(0.73864 mm)2 in-plane pixel
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Calibration procedure
Reference data?MC source dosimetric data ?(lt1
uncertainty)?Source Sk (3 uncertainty)?Irradiat
ion time
Response Ref.Dose matching?3 mm lt
ri lt 22 mm away distances?0.74 mm ri
steps?R2imeanR2mean(ri)
sR2isR2mean(ri)
Weighted least squares regression?wi1/sR2i2?R
2a1D2a2Da3?a1 -(0.000280.00004) Gy-2?s-1
?a2(0.07920.0018) (Gy?s)-1 ?a3(1.3410.011)
s-1
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Calibration procedure induced uncertainty
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Measurement procedure induced uncertainty
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Total experimental uncertainty to dose
13 mm
5.4 mm
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Along dose profile
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On the use of VIP Gel dosimetry
in HDR brachytherapy
?
Questions
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