Overview of Real Time Semiconductor Dosimetry in Radiation

Modeling a Novel Detector Module for Positron Emission Tomography using GATERadiation Therapy
Australia
2nd Workshop Hadron Beam Therapy of Cancer Erice, Italy, 20-27 May, 2011
SSD Summer School 2010 UoW Anatoly B. RosenfeldHadrontherapy Workshop 2011Hadrontherapy Workshop 2011
Outline • Semiconductor Dosimetry in RT
• Diodes Design and its Applications in SRS, IMRT • Dose Magnifying Glass • Magic Plate
• MOSFET, MOSkin Design and its Applications • Skin Dosimetry in Radiotherapy • Brachytherapy Applications • IMRT and 3D CRT Applications
• 2D Si High Spatial Resolution Dosimetry • Medipix-Eye plaque QA
• Electronic Dosimetry in MRT and Hadron Therapy • Semiconductor dosimetry on synchrotron MRT • Si detectors for RBE determination
• Conclusion
much smaller volumes than an ionisation chamber
• 18000 times the sensitivity per unit volume of an ionisation chamber
• 10 times smaller ionisation energy than an ionisation chamber (3.6 eV for silicon, 35 eV for gas)
• Small size enables • Satisfaction of the Bragg-Grey cavity theory • High spatial resolution • Applications in confined spaces • Applications for various radiation fields
The most suitable semiconductor for dosimetry is Silicon
• Possibility to use in active and passive modes • Suitable for electronic signal processing with silicon
chip (microprocessor) build up in the detector • Silicon devices are very technological
Advantages of Semiconductor Dosimetry
SSD Summer School 2010 UoW Anatoly B. RosenfeldHadrontherapy Workshop 2011
Bragg-Gray Cavity Theory
w
g
For a sufficiently small cavity g, within a different medium w and incident flux Φ, the dose to the water, Dw may be determined through use of the mean mass-stopping power ratio:
Dosimetric Ratios of Silicon-to-Water
Mass-Energy Absorption Coefficient Ratio for Silicon to Water
Mass Stopping Power Ratio for Silicon to Water
•The energy response of Si detector which is satisfying B-G cavity theory and placed in water will be relatively flat in a wide energy range
•Silicon is not water equivalent in free air geometry or in case of a range of secondary electrons in Si is smaller than Si cavity
Diode – Principle of Operation
J Shi et al. Med. Phys. 30 (9), 2003, 2509-2519
S =α(Dτ)0.5
=6.72x10-7 C/cGy/cm.
The sensitivity of the diode, S, represents the amount of charge collected without recombination
Application of a 2D Diode Array
http://www.sunnuclear.com
•An array of 445 n-type diodes for independent dose rate measurements (±2%)
•Advantage – The possibility of simultaneous verification of dose at many points
•Disadvantage – Impossible verification for steep dose gradients
Diode based systems for 3D dosimetry QA
James L Bedford, Phys. Med. Biol. 54 (2009) N167–N176
DELTA 4
N-Si Diodes in ArcCHECK
Guanghua Yan , Med. Phys. 37 ,1, Jan, 2010
Relative diode intrinsic sensitivities of the 124 diodes on the diode array normalized to the response of the third diode
ArcCHECK, Sun Nuclear,Angular response of n-Si diodes
Effect of Diode Design and Packging
S-12 P-type, no pre-irradiation, 1.0-mm-diameterx 0.25-mm active volume, PCB, copper 0.0178-mm thick, light-tight epoxy housing of 0.4-mm thickness
SN,P-type, 10 kGy pre-irradiation, 1.6X1.6X0.05 mm3 active volume, 0.051-mm-thick copper, encased in a thin epoxy of 0.11 g/cm2
P.Jurinsic, Medical Physics, Vol. 36, No. 6, June 2009
CMRP Epi-D and Detector-Drop In Design
0.8mm
0.8mm
0.15mm
tracks
layer
solder
CMRP Drop In detector technology, patented
Magic Plate (MP) • 2D 11 x 11 cm Si diode
array, 0.5mm thick • Sensor area: 0.5 x 0.5
mm2
epi-diodes CMRP technology
• New model: 1024 diodes
Magic plate mounting on linac gantry
From in a phantom QA to
In vivo real time fluence verification
in RapidArc RT and IMRT
Percent Depth Dose with Magic Plate
• Depth dose curve for a 10 × 10 cm2 field size of a 6 MV photon energy measured with a CC13 ion chamber and the MP
0
10
20
30
40
50
60
70
80
90
100
110
IMRT
1
2
3
4
5
6
7
8
9
10
Fluence measurement in transmission mode
EBT2Magic Plate
Pass Rate: 95.04% Gamma agreement (3% dose difference, 3 mm DTA)
In phantom dose measurement Setup: • The MP was sandwiched between two pieces of 5 mm solid
water plates machined to fit into the cavity of the I’mRT phantom.
• The MP and the I’mRT phantom were aligned to the isocentre (SDD 100 cm).
100 cm
9 cm
Magic Plate EBT2 Pinnacle
Pass rate: 93.38%
Pass rate: 82.64%
Dose profiles
• Generation of electron-hole pairs in silicon oxide by ionizing radiation
• Trapping of holes on the SiO2-Si interface
• Shift in the IV characteristics leading to a change in the threshold voltage under constant channel current
Advanced MOSFET Dosimetry-Principle of Operation
tox
I
Passive mode - Vth ~ 0.0022 D0.4 tox 2 f
Active mode - Vth ~ 0.04 D tox 2 f
Active mode has a positive bias on the gate during operation
MOSFET Chips
Silicon Chip
MOSFET Structure
RADFET REM Oxford
Real Time MOSFET Dosimetry System
Real Time MOSFET Clinical Dosimetry System with MOSPLOT DAQ: designed and distributed by CMRP
New MOSkin Design • The Centre of Medical Radiation Physics (CMRP) has designed a new
MOSFET-based dosimeter called the MOSkin™.
• The new MOSkin detector 1) Incorporates a single MOSFET sensor. 2) Is temperature independent. 3) Used in either passive or active mode. 4) Has a highly reproducible build-up layer, capable of measuring
skin dose according to the ICRP 1992 recommendations (0.07 mm basal layer depth)
~ 0.8 mm
Build-up layer
MOSkin detector: WED and reproducibility
Monte Carlo vs Experiment
Reproducibility in a batch, 1.5% Measured at Dmax, 10x10 cm2 For 10 MOSkin out of 500MOSkin vs MOSFET and ATTIX
QA in HDR for Nasopharyngeal Carcinoma
• MOSkin detectors are placed inside the left nostril whilst an Ir-192 source is stepped through the right nostril
QA in HDR for Nasopharyngeal Carcinoma • A thermoplastic mask was used for patient
immobilization and was also used to fix the applicator
• A CT scan is used to identify the MOSkin detector locations
• In vivo real time dose measurements were performed using MOSkin detectors during treatment.
nasopharyngeal applicator
QA in HDR for Nasopharyngeal Carcinoma • CT images were acquired with the carriers
inserted -- 3mm slice thickness.
• Point P1 represents the location of the MOSkin, while P2, P3, and P4 are opaque markers. The Ir-192 source is inserted down the carrier and through the other nostril.
• A total of 7 patients were measured using the MOSkin detector. The average deviation was within ±5% of the predicted dose, with the maximum deviation less than 10%.
• The relative deviation (%) of the measured doses from the treatment plan for four fractions is shown for one patient.
0
Fraction N um ber R e la tiv
e D
Real-time comparison of in vivo measurements with TPS in agreement within 5%
MOSkin: Dose verification in serial IMRT treatment (NPC)
The custom-made oral plate produced for each patient to keep MOSkin on a surface of the tongue .
a: top view b: bottom view
Taste dysfunction and oral mucous reaction are major radiation sequel in NPC patients receiving radiotherapy. Clinical trial is ongoing to explore the role of a molded oral plate in sparing the normal oral tissues by pushing tongue away from radiation field during radiotherapy for some NPC cases. Total dose 68Gy, 30 fractions. Real time measurements were carried out of surface dose on a tongue with 2 MOSkins placed on interface tongue -plate, MOSkin dose was readout each second during IMRT delivery with MOSPLOT4.1 software Measurements were usually performed during the first treatment session and once a week thereafter. A total of 8 NPC patients and 48 dose points have been currently measured in vivo.
a b
• A special mouth plate was designed by a dentist to keep the MOSkin detector against the surface of the mouth.
Dosimetry in IMRT • MOSkin has also been used for dose verification
during IMRT
MOSkin: Dose verification in serial IMRT treatment (NPC)
• In vivo MOSkin in differential readout mode provide each second temporary map of IMRT delivery ( 1 cGy is corresponding to 2.45mV)
• In vivo MOSkin in integral mode provide total dose immediately after delivery
• Measured total dose on a surface of the tongue for particular treatment fraction and patient was 48.96 cGy while TPS predicted dose was 47.90 cGy and agreed within 2.2%
Real-time rectal wall measurements CMRP MOSkin – Rectal Balloon
Dual MOSkin + rectal balloon
Angular response
•The MOSkinTM Dosimeter angular response has been greatly improved through the use of a dual FET design
Brachytherapy Phantom Measurement • A gel phantom with rectal cavity was implanted
with 18 catheters to simulate a prostate brachytherapy treatment
• A Radiadyne balloon containing dual MOSkinTM
dosimeters on both the anterior and posterior lumen was inserted into the phantom
Brachytherapy Phantom Measurement
• The phantom was imaged with using CT and a treatment plan about a virtual prostate was generated using PLATO
The anterior (red) and posterior (green) detectors were clearly visible on the CT scan
The planned doses to both the anterior and posterior detectors were 7.18Gy and 2.21Gy respectively
Brachytherapy Phantom Measurement
• The dose to both the anterior and posterior detectors was measured in real time during the delivery of a single fraction
The dose received by both the anterior and posterior detectors after each catheter
MOSkin:HDR Brachytherapy • Balloon with dual MOSkinTM
detectors on both anterior and posterior rectal wall
• Real time in-vivo measurements obtained
• Single MOSkinTM data obtained from detector with face up to the rectal wall
• Single and dual FET measured doses compared to predicted dose
CT showing location of the anterior rectal wall detector
HDR brachytherapy results • Anterior rectal wall • Dual MOSkin
• 351cGy • Single MOSkin
• No discernable difference between single and dual MOSkinTM
Accumulated dose vs time for both dual and single MOSkin measurements during one HDR brachytherapy fraction
Real-time rectal wall dosimetry: dual MOSkin
Prostate
Dual MOSkin - Seven field 3DCRT plan:
Beam 1
Beam 2
Beam 3
Beam 4
Beam 5
Beam 6
Beam 7
Dual MOSkin + rectal balloon - Seven field IMRT (modulated delivery) plan:
Beam 1
Beam 2
Beam 3
Beam 4
Beam 5
Beam 6
Beam 7
the planned dose
Breast Radiotherapy Skin Dosimetry
•Above plan is Hybrid IMRT •Two opposed tangential fields with extra segments to spare “hot spots”
•Breast cancer affects 1 in 11 Australian women •Currently, skin dose is not accurately known and connected to skin toxicity •National Cancer Institute:
Common Toxicity Criteria (CTC) Version 4.02 Sets out broad guidelines for skin toxicity ranging from (roughly):
1:Faint erythema or dry desquamation 2:Moderate erythema, patchy desquamation 3:Moist desquamation, abrasion induced bleeding 4:Skin necrosis 5:Death
Breast Radiotherapy Skin Dosimetry
Dosimetry Study •EBT Gafchromic film strips on phantom in regions of interest •Moskins placed in various positions along film
– ICRP 60 indicates that 70 microns is the depth considered to be radiosensitive
Near-Apex B reas t Dos e Hybrid IMR T
0
10
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30
40
50
60
70
80
90
100
-5 15 35 55 75 95 115 135 155 175
T ime (s)
Moskin E B T film
Moskin EBT film Real-time dosimetry Development period before readout 70 microns W.E.D Symmetric 153 micron W.E.D
Conclusion 1 • While the ionizing chamber is always the gold
standard in radiation therapy, semiconductors diode and MOSkin are the future of online in vivo dosimetry
• MOSFET dosimetry is unique for skin and surface dosimetry
• MOSkin is a new MOSFET suitable for many RT applications where skin dose is an issue
• Design of diodes and its packaging is critical for their response and not trivial
Dose Sensitive to Variations in WEPL
Tumor
Measurement gives water equivalent path length (WEPL) to dosimeter locations
Useful only if …
WEPL
~
LET effect creates the depth dependence!
Can be MOSFET used for WEPL measurements? MOSFET is LET dependent detector
A.Roseneld et al. IEEE TNS, 47, N4, 1386-1394, 2000
Can the Implantable Dosimeter (DVS) Be Used for Measuring
WEPL?
Strip Si detectors: from HEP to Radiation Oncology
Strip detectors are used in HEP in Vertex Detectors for m.i.p. tracking with micron spatial resolution 1D and 2 D.
Charge deposited by particle is shared between strips (p-n junctions) allowing determination “centre of mass” and particle coordinate
Technology exist for Mega-strips readout
Linear Si mini-sensors array for QA in RT
Size 2x25mm , 128 mini sensors 0.02x1mm , pitch 0.2mm
TERA readout and DAQ system 2@64 channels
Dose Magnifying Glass (DMG)
• 128 channel –p-type Si strip detector • Area: 20 x 5000 µm • Thickness: < 0.4 mm • Kapton thickness: 0.1 mm
DMG vs IC PDD
Depth (mm)
PD D
cc13 Ion chamber CMRP SSD
DMG vs cc13 ion chamber
6MV Clinac, 10x10 cm2 field, solid water phantom At the depth of 10 cm, (d10), the difference is 0.1% At the depth of 20 cm, (d20), is 1.2%. The D20/10-- for the DMG is 0.562
--- for the cc13 IC is 0.576
DMG: linearity and penumbra resolution
Dose Linearity
0 100 200 300 400 500 600
-50 50 150 250 350
Dose (cGy)
Co un
ts (x
1 03 )
Penumbra at 1.5 cm depth
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
0.0 5.0 10.0 15.0 20.0 25.0
Distance (mm)
Re no
rm al
iz ed
O AR
CMRP - MLC Rounded Leaf End
Linear within the range of a normal IMRT dose per fraction (not limited)
Table 1: Comparison of the 80-20% penumbra width measurements between the CMRP DMG, Gafchromic EBT films, and other published literatures.
CMRP DMG (mm) EBT film (mm) Others (mm)
X-Jaw (Symmetric) at 1.5 cm depth 2.77 2.71 3.028
X-Jaw (Asymmetric) at 1.5 cm depth 2.93 3.23
MLC (Symmetric) at 1.5 cm depth 3.52 4.629
X-Jaw (Symmetric) at 10.0 cm depth 3.93 4.5 4.23
MLC (Symmetric) at 10.0 cm depth 5.50
A.Application in IMRT fields
Penumbra at1.5 cm depth for the secondary X-jaw and the rounded leaf DMG vs EBT
DMG: Temporal and Spatial dose in IMRT
Single IMRT field (gantry angle 315°) with 10 segments
Temporal and spatial dose distribution for full step and shoot IMRT delivery
DMG: dose rate temporary pattern in IMRT
Cumulative dose profile for full IMRT delivery
Dose rate temporary patterns essentially different for detectors 7 and 128!!!
DMG:SRS cone profile and penumbra measurement
80-20% penumbra width 0.22 ± 0.07 mm
FWHM 0.12 ± 0.09 mm
Custom made SRS phantom with DMG
SRS dose verification in Real Time
Lucy Phantom from Standard Imaging +DMG is an optimal QA for real time dose verification in SRS
Determination of center of rotation (COR) • To measure the
radiation isocenter displacement due to gantry, collimator and, couch rotation of the linear accelerator
Collimator 0.2 ± 0.1 mm Gantry 0.4 ± 0.1 mm Couch 0.1 ± 0.2 mm
Maximum positional error:
Distance (mm)
D et
ec to
x
DMG: SRS delivery verification • 4 SRS arcs of 180o
angles • Couch angles:
270o, 300o, 330o, 360o.
• average difference = 4.1 ± 6.7%.
DMG-fast and accurate QA in SRS with 0.2 mm spatial resolution
DMG will be useful for SPB QA: •Dose profile •Speed of scanning •SRS
Si pixel detectors for dose imaging: eye plaque QA • Melanoma and squamous cell carcinoma are the most
prevalent ocular malignancies in adults • Almost 50% of patients will lose vision or the eye due to the
disease and/or the treatment • Ocular melanoma is typically treated by resection of the
surgical mass, radiotherapy, or via enucleation • Brachytherapy using radioactive eye plaques is the preferred
method of treatment for patients with ocular malignancies
Intraocular melanoma[1]: Iris with nodular melanoma (left)
large choroidal melanoma (right)
[1] Shields, C.L. & Shields, J.A., “Ocular melanoma: relatively rare but requiring respect”, Clinics in Dermatology, 27, 122-133, 2009.
Eye Brachytherapy
• Involves the surgical insertion of a radioactive plaque behind the tumour
• Has been successful in achieving local tumour control for eye melanoma
• Possible vision impairment or loss
Rendition of a seeded plaque irradiating a tumour
Eye Plaques
ROPES I-125 Plaque • Gamma emitter with
max energy 35.5 keV • Individual seeds • Can vary seed no. and
activity
electron energy 3.54 MeV
• Uniform layer • No customisation
Current Brachytherapy Dosimetry
• The BEBIG treatment planning software (TPS) allows the selection of any seed configuration and activity in a selection of plaques, providing depth dose and isodose curves
• Dosimetric measurements have been performed using TLDs and, more recently, plastic scintillators
• 3D fast dosimetry of eye plaques is not available currently
BEBIG plaque simulation
Limitations in Dosimetry • Surrounding vital structures are not accounted for • For a plaque placed against the optical nerve, more
than 100% prescribed dose delivered to optical disc and macula for large tumours[2]
• Sharp decrease in dose-rate distribution along the eye[3] • Current TPS lacks accuracy around the border of the
eye (sclera and surrounding area)[3] • Seeds may be of varying activity, introducing additional
inaccuracy in dose delivery • Inaccuracies introduced through surgical misplacement
of the plaque • Varying tumour shapes demand the development of
customised plaques [2] Wu, A., Krasin, F.,“Film dosimetry analyses on the effect of gold shielding for iodine- 125 eye plaque therapy for choroidal melanoma”, Medical Physics, 17(5), 843-846, 1990.
[3] Granero, D., et al., “Dosimetric studies of the 15 mm ROPES eye plaque”, Med. Phys., 31, 3330-3336, 2004.
Medipix device single particle counting pixel detector
Medipix2 Pixels: 256 x 256 Pixel size: 55 x 55 µm2
Area: 1.5 x 1.5 cm2
Medipix2 Quad Pixels: 512 x 512 Pixel size: 55 x 55 µm2
Area: 3 x 3 cm2
www.cern.ch/medipix
• Bump-bonded to Medipix readout chip containing in each pixel cell:
- amplifier, - double discriminator - Counter or ADC (TimePix)
Detector chip Medipix chip Bump-bonding
α, β, γ
Dosimetry Imaging • A single 6711 brachytherapy seed was
placed on the surface of the Medipix2
• A 2D dose map of the seed was obtained from the pixel values
2D dosimetric image of seed
Single seed on Medipix2 surface
3D Dose Reconstruction • Individual planar dose
maps may be combined to form 3D dose maps such as these isodose surfaces
5 seed 3D isodose surface
10 seed 3D isodose surface
BrachyPix
• BrachyPix will offer • Real time 3D dosimetric imaging of prescribed radioactive
plaques • Verification of treatment dosimetry
• Providing QA for optimised treatment
Seeds loaded Dosimetry obtained
BrachyPix
•4@32 readout channels ASICs HERMES, BNL
•Fast 3D dose reconstruction
Water Phantom Measurements
Conclusion 2 • We are developing a unique system for 3D
dosimetry of eye plaques prior to insertion
• BrachyPix, with it’s fast acquisition time and high resolution output, is designed to overcome current limitations in clinical dosimetry
• BrachyPix allows for the customisation of eye plaques to optimise brachytherapy treatment
• BrachyPix offers a fast, accurate, real time QA system for treatment planning verification
Small Detector (um)
Ionising particle tracks
• Microdosimetry • Assumes the weighting factor is related to the energy deposited in the
cell nucleus: ε • Measure this for each particle that crosses detector • Formulate dose distribution: d(ε) • Integrate with weighting factor to give Equivalent Dose: H = ∫ Q(ε)d(ε)
dε • Equivalent Dose can be used to accurately predict biological effect of
radiation
Microdosimetry and Equivalent Dose
From Garret and Grisham, "Biochemistry" Copyright 1995 by Sauders College Publishing
Microdosimetry and Fluence approach for stochastic events
∫= dyydyQH )()(
ir )()( φσ∑∫=
Fluence based approach Measure types and energy distribution of all particles Integrate product of risk cross section a fluence over energy Sum over all particles to directly obtain risk estimate
Microdosimetry Measure distribution of ionisation events in microscopic volume Derive quality factor and equivalent dose estimate
Q(y), Q(L) and σ(Ε) were modified recently , ICRU 92 and NCRP 137 Quality coefficient for low doses neutrons is still uncertain
All above characteristics are relevant to Radiation Protection only
• Microdosimeter measures the energy deposition events in a small (cell-sized) volume due to radiation interactions.
• Produces spectra of counts versus energy (E). • Divide energy by mean chord length (l) gives lineal energy spectra f(y) • Dose distribution d(y) yf(y) where y=lineal energy=E/l
• Motivation: • Radiobiological effectiveness depends upon LET or lineal energy • Distribution of dose (d(y)) with lineal energy gives dose equivalent (H)
CMRP contribution: Si microdosimetry
0
0
0.1
0.2
0.3
0.4
0.5
0.6
Q (y
0 10000 20000 30000 40000 50000 60000
10 100 1000 10000 Energy(keV)
C ou
Radiation(Alpha) traversal of a cell in BNCT
High LET hits to the nucleus increase probability of multiple DNA breaks
Nucleus of cell
Ideal Charge collection region (Voltage applied across reverse biased depletion region(shaded) separates electron-hole pairs )
Al Contact(0.6µm)
P+(0.4µm)
Al Contact(0.6µm)
Alpha Particle Proton or other ionising charged particle
+ + +
- - -
(Cross-Section of a Single Diode, 4800 diodes connected in parallel)
Radiation Effect on a Biological Cell
New Approach: Silicon Microdosimetry
3D SOI silicon microdosimetry •3D silicon cell array for modeling of energy deposited in biological cells event by event by secondaries •Each Si cell is 6x10 microns
3D SOI silicon microdosimetry:new design, CMRP • 3D Sensitive Volume: cell
representation •IBIC: charge collection in 2µm 3D SV 5 MeV a-beam-100%
UNSW, Sydney nanotechnology facility
SOI Microdosimertry on 100 MeV Proton Therapy
• Microdosimetric spectra from 10 mm SOI micro at consecutive positions in a Bragg Peak
• Possibility to estimate Q of the beam For more details see: A Rosenfeld “Electronic Dosimetry in Radiotherapy”, Rad. Meas., 41, 134-153, 2007
0
5
10
15
20
25
30
35
40
45
0 1 2 3 4 5 6 7 8 9
Depth (cm) C
h a rg
CMRP contribution:Experimental Setup
• The microdosimeter was moved parallel to the central beam axis 5cm from the field edge.
• The device was centred to the height of the central axis
• Incident protons of 225MeV were used.
Measurement Positions
Proton Radiation
CMRP contribution: Proton Therapy- secondary cancer risk estimation
•Invited in phantom experiments were carried out at LLUMC and MGH proton therapy facilities
•All typical cancer treatment scenario with PT were investigated
•Measured dose equivalent was less then predicted that make confirmation of safety of PT
CMRP: Firstly measured dose equivalent with silicon SOI microdosimetry.
Results
• Haperture has a different dependence on depth than Hblock
• Scattered primary protons affects H and the determination of Q up to 22.3 cm depth
• Downstream of the Bragg peak, difference in H is due to n generated in the phantom
Scanning parallel to the beam at 5cm offset
New Si detector technique for RBE measurements • New method recently was proposed at CMRP for RBE
characterization in hadron therapy which is based on microdosimetry and secondary particles identification simultaneously.
• While SOI microdosimetry is accepted for RBE determination,new approach introduce possibility therapeutic RBE determination based on in vitro cell experiments or other radiobiological models and Cancer Risk estimation based on fluence approach.
Note: Reference to RBE is related to theoretical concept rather then real in vivo RBE that impossible to measure with devices
Importance of the Track Structure • Ions with the same LET providuce different
radiobiological effect • Track structure is important • Measurements of
deposited energy on nm scale is required or Position of event on E-E plane
RBE: E-E Si-telescope concept in radiotherapy
α
p
E + E (MeV)
100
50
0
•Possibility to use track structure information for specific ions •Possibility of Monte Carlo verification •Possibility conversion of 2D E-E plot to RBE and/or cancer risk assessment
C-12
3D RBE: Monolithic Silicon Telescope
n+
p+ ring
B implantation to create buried p+ thickness E ~ 2 microns thickness E ~ 500 micron Developed by Tudisco et.al.,
S.Agosteo, A.Fazzi , P.Fallca et.al. (Politecnico di Milano, Italy)
Characterized jointly at CMRP/ANSTO
100 MeV proton beam experimental set up
• 100 MeV beam line (no modification devices
• Beam spot more then 5 cm diameter
• Polystyrene phantom • Mono-energetic and SOBP • (not optimized modulator • wheel ) • Portable DAQ system USB
connected laptop for 2D coincidence (Politec. Milano)
E-E probe assembly in a phantom , LLUMC experiment of CMRP, 2007, A.Wroe,A.Rosenfeld, A.Fazzi, A.Pola, S.Agosteo, R.Schulte, Med. Phys., 36(10):4486-94, 2009
E-E telescope for RBE measurements
Modification of 2D E-E spectra of primary and secondaries with depth along the 100 MeV Bragg Peak
0
5
10
15
20
25
30
35
40
45
0 1 2 3 4 5 6 7 8 9
Depth (cm)
C h
a rg
3D Radiobiological Semiconductor Dosimetry Method: • Collecting data on RBE(10%) and RBE (α) (in vitro)
for different types and energies of charged particles from biological experiments with V79 Chinese Hamster cells (published data were analysed by A.Wroe, during his PhD studies)
• Mapping the position for these charged particles on E-E scatter plot and corresponding RBEα to the same position
• Deriving of “RBE” conversion matrix on a E-E plane
• Radiobiological interpretation of E-E coincidence map
3D “RBE” in hadron therapy
Point “RBE” in a target volume painted by beam can be experimentally derived from 3D E-E map superimposed by Qi,j :
∑= ji
jiji
.
,,
Ei.j is a total energy at i,j point on E-E scatter plot Q i, j –radiobiological matrix derived from radiobiological models, nano-dosimetry, in vivo or in vitro cell experiments.
3D Radiobiological Semiconductor Dosimetry • RBE(10%) versus LET distribution of V79 biology
results used in the radiobiological interpretation of E-E telescope response.
• The correlation method of generating a matrix from a random collection of points is based on the Kringing method.
3D Radiobiological Semiconductor Dosimetry • Alteration of radiobiological matrix to experimental
E-E coincidence map in 10OMeV proton beam experiment
• E-E coincidence map for the pick point on a BP of 100 MeV protons
3D Radiobiological Semiconductor Dosimetry • Experimentally derived RBE along pristine and SOBP
for 100 MeV proton beam • Results: RBE and absorbed dose peaks are shifted
as confirmed earlier in biological experiments • High spatial resolution of semiconductor RBE
dosimetry
Different RBE pattern among BP is due to different neutron spectra
62MeV/u C-12 beam line, INFN
Points of E-E detector measurement along the Bragg peak E-E plot for detector at point I
ΔE/E scatter plots allow particle identification of the light ions, e.g. H, He, Li, Be, and B additionally to C-12 in carbon therapy S Agosteo et al. .
Courtesy of S. Agosteo, Milan Poiltek. Presented at SSD 16
Conclusion
• Semiconductor dosimetry is an important part of radiotherapy quality assurance
• It has many advantages as high spatial and temporal resolution has possiblity of easy integration with multi- channel read-out systems and multifunctional with application for dosimetry and microdosimetry
Acknowledgement :The CMRP –staff
Prof Peter Metcalfe
Dr Michael LerchA/Prof Bill Zealey
Dr George Takacs
Acknowledgement: The CMRP – Research students
Bradley Oborn Stephen Dowdell
Amir Othman Jeannie Wong Lakshal Perera Heidi Nettelbeck
Plus many more ……………. 26 PhD students, 14 Master (Res) 15 Hon students+ Master course work
Cheryl Lian
Acknowledgement
Special acknowledgement to our partners: • SPA BIT CMRP exclusive semiconductor foundry • Ilawarra Cancer Care Centre, Wollongong • St George Cancer Care Centre, Sydney • POWH , Radiation Oncology, Sydney • Liverpool Hospital, Sydney • LLUMC and MGH proton therapy centers, USA • Memorial Sloan Kettering CC, USA • Wisconsin University, Dpt of Medical Physics , USA • Milano Polytechnic, Italy • Prague Technical Uni, Chez This work will be impossible without large number of
PhD students at CMRP who are essentially contributing to all results.
Overview of Real Time Semiconductor Dosimetry in Radiation Therapy
Outline
Diode based systems for 3D dosimetry QA
N-Si Diodes in ArcCHECK
Magic Plate (MP)
IMRT
In phantom dose measurement
MOSFET Chips
Slide Number 37
Dosimetry in IMRT
Real-time rectal wall measurements
Dual MOSkin + rectal balloon
Dual MOSkin
Useful only if …
Can be MOSFET used for WEPL measurements?MOSFET is LET dependent detector
Can the Implantable Dosimeter (DVS) Be Used for Measuring WEPL?
Strip Si detectors: from HEP to Radiation Oncology
Linear Si mini-sensors array for QA in RT
Dose Magnifying Glass (DMG)
DMG vs IC PDD
DMG: Temporal and Spatial dose in IMRT
DMG: dose rate temporary pattern in IMRT
DMG:SRS cone profile and penumbra measurement
Custom made SRS phantom with DMG
Determination of center of rotation (COR)
DMG: SRS delivery verification
Eye Brachytherapy
Eye Plaques
Dosimetry Imaging
CMRP contribution: Si microdosimetry
New Approach: Silicon Microdosimetry
3D SOI silicon microdosimetry
SOI Microdosimertry on 100 MeV Proton Therapy
CMRP contribution:Experimental Setup
Results
Importance of the Track Structure
RBE: DE-E Si-telescope concept in radiotherapy
3D RBE: Monolithic Silicon Telescope
100 MeV proton beam experimental set up
DE-E telescope for RBE measurements
3D Radiobiological Semiconductor Dosimetry
Conclusion
Acknowledgement

Documents

Overview of Real Time Semiconductor Dosimetry in Radiation