radiation protection and dosimetry for the medical...
TRANSCRIPT
Radiation protection and
dosimetry for the medical field
Toshioh Fujibuchi, R.T., M.P., Ph.D.
Division of Medical Quantum Science
Department of Health Sciences
Faculty of Medical Sciences
• Development of radiotherapy setup training system
• Radiation protection and dosimetry for the medical
field using Monte Carlo (MC) simulation:
Estimation of dose distribution in the IVR and
CT room
Estimation of the secondary risk of cancer
following radiation therapy
• Development of real-time monitoring devices for
the medical staff
Research subjects in Fujibuchi Laboratory
Development of the training system for patient
set-up technic using Mixed Reality environment
Irradiation of radiotherapy is repeated for about one month.
The skill for patent set-up technic (adjustment of patient
position) in radiotherapy to technologist is important.
However, radiotherapy equipment in hospitals is clinically
used during the day, and students are difficult to use the
equipment for training.
We developed the training
system for patient set-up
technic using Mixed Reality
environment.
Virtual radiotherapy
roomReal patent phantom
< Mixed Reality (MR) >
VirtualReal
Student B moves
the couch
Student A adjusts
the patient
Radiotherapy room
in hospital
The Concept of MR
training system for
patient set-up technic
Control virtual couch using tablet
• Control couch using tablet (lateral, long and vertical
direction)
• Connected Wifi between tablet and host PC
Control patient phantom using smartphone
Pitchroll
Yaw
• Control tilt of patient using Jairo sensor
in smartphone (roll, pitch and yaw)
• Connected Wifi between smartphone
with Host PC
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The MC simulation
• A technique of numerical analysis
• Uses random sampling to construct the solution to a problem
• Allows us to study of how radiation interacts with matter and is transported in a medium in realistic geometry.
血管造影室内の空間線量分布の評価と防護方法の検討Estimation of Dose Distribution in an IVR Room
C-arm
FPD
phantom
X-ray tube
Couch supporter
Couch
Sato N., Fujibuchi T., Radia. Prot. Dosi., 2016
Rel
ativ
e H
*(1
0)
X-ray tube
FPDC-arm
Phantom
Couch
FPD
X-ray tube
10-0
10-1
10-3
10-4
10-5
10-6
10-2
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 80 100 120 140 160 180
Rel
ativ
e H
*(1
0)
Height at the physician’s position (cm)
Nothing
Only curtain
Tungsten sheet on
the side of the
phantom + curtain
Shielding effect of the protection sheet
Protection
curtain
Protection
sheet
Sato N., Fujibuchi T., Radia. Prot. Dosi., 2016
Bed
CT gantry
Estimation of dose distribution in a CT room
CTDI phantom
Bowtie filter
Rel
ativ
e H
*(1
0)
Average: 1.002 ± 0.173
Measurement points
C/M
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
1-4
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2-4
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13-9
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34-1
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C/M: Calculated value/Measured value
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Pb
Polyethylene
H218OTarget
Diffusion pump
Estimation of neutron
fluence distribution
around a compact medical
cyclotron
107
106
Th
erm
al n
eu
tro
n flu
en
ce
ra
te (
1/c
m2/s
ec)
Calculation
Measurements
0
0.2
0.4
0.6
0.8
1
1.2
1 3 5 7 9 11 13 15 17 19
Rela
tive f
luence
Measured points
C/M: 0.80 ± 0.20
Comparison of the measured value
and calculated value of neutron
fluence
Photon and neutron fluence
distribution
Neutron Photon
② 1%
③22%
④ 12%
⑤ 2%
①65%
Structures Ratio
① Primary
collimator0.65
② Flattening
filter0.01
③ Upper jaw 0.22
④ Lower jaw 0.12
⑤ MLC 0.02
The ratio of neutron produced from each
structure
Estimation of the secondary cancer risk
following radiation Therapy
14
ICRP 110 phantom-male
Preliminary
Development of wireless multi-sensor active personal
dosimeter - tablet system
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Background
• Medical staff working in the field of IVR face the risk of exposure to relatively high doses of scattered radiation emitted from patients’ bodies.
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• For example, during
fluoroscopy in
interventional cardiology,
the dose at the location of
the cardiologist
corresponds to a scattered
dose of 1–14 mSv/h.
Background
• To manage occupational exposure, medical staff wear protective aprons and use personal dosimeters.
• When the staff place the TLD or electrical personal dosimeter (EPD) in the garment or the protector, they cannot read the dose in real time.
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EPD-GPDM-107
DOSE i-γ
PDM-127-SZPDM-122B-SHC
Commercial EPDs cannot wirelessly
monitor the exposure doses.
• Individual monitoring in
real time and display of
the dose wirelessly on
the monitor help
determine exposure
doses during IVR.
Purpose• We developed a multi-sensor wireless dosimeter
system called “Pocket Dose,” which provides real-time visualization of the dose levels on an Android tablet screen.
• In this study, we investigated the characteristics of the energy dependence and dose rate of this system.
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A display of tablet
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Pocket Dose• Wireless multi-sensor active personal dosimeter -
tablet system
• The detector transmits information to the tablet using
Bluetooth.
Tablet
Tcransmitter
4 detectors
1 m cable
• The four detectors were designed to measure unequal exposure of the staff.
• The detector contains two kinds of Si-PIN photodiode sensors with low dose rate and high dose rate.
Pocket Dose detectors
2 sensors (different
sizes and sensitivity)
3.5 cm
6 cm
Transmitter
in pocket
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User interface of
the Pocket Dose
application
• Doses
• Counts
• Pulse-height
histograms
• The acquired data
can be transferred via
e-mail from the tablet.
Method 1: Energy correction using pulse-height distribution
• Tube voltage : 60, 80, 100, and 120 kV
Method 2: Evaluation of dose-rate characteristics
• Dose rate: 0.14–1700 mSv/h
Pocket Dose
detector
Reference
dosimeter
1 m
1 m Torso phantom Detector
X-ray tube
Investigation the basic characteristics of the system
Energy correction using pulse-height distribution
0
0.2
0.4
0.6
0.8
1
1.2
0 20 40 60 80 100 120
Rel
ativ
e co
un
t
Energy (keV)
60 kV80 kV100 kV120 kV
0
0.2
0.4
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0.8
1
1.2
0 2 4 6 8 10 12 14 16 18 20 22
Rel
ativ
e co
un
t
Channel (ch)
60 kV80 kV100 kV120 kV
CdTe spectrometer Pocket Dose
C (x) ×F(x) = C’ (x)
・ C’ (x) : corrected Pocket Dose count
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PD PD
PD
0
0.2
0.4
0.6
0.8
1
1.2
1 3 5 7 9 11 13 15 17 19 21
Rel
ativ
e co
un
t
Channel (ch)
Pulse-height histogram of Pocket Dose = (CPD(x))
0
0.2
0.4
0.6
0.8
1
1 3 5 7 9 11 13 15 17 19 21
Rel
ativ
e co
un
t
Channel (ch)
Calibrated pulse-height histogram
Not correctedPocket Dose
CorrectedPocket Dose
0
0.5
1
1.5
2
2.5
3
3.5
1 3 5 7 9 11 13 15 17 19 21Channel (ch)
Correction Coefficient(=F(x))
Method of energy correction
*ICRP 74
F(x) = Hp(10)/Φ * × sensitivity
correction factor of PD
Evaluation of energy characteristics
25*Effective range of relative error recorded at JIS Z4312
0.8
0.9
1
1.1
1.2
1.3
30 31 32 33 34 35 36 37 38 39 40
En
erg
y d
epen
den
ce
Photon energy (keV)
Effective range of relative
error
Normalized at 80 kV
PDM-107
Thermo scientific EPD-G
PDM-127B-SZ
Not corrected Pocket Dose
Corrected Pocket Dose
Evaluation of dose rate characteristics
The linearity was showed until 100 mGy/h.
1
10
100
1000
10000
0.1 1 10 100 1000 10000
Co
un
t ra
te [
cps]
Dose rate [mGy/h]
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Scattered dose
range in IVR
Conclusion
• The system has great potential for energy
correction using the energy-spectra information.
• This system allows easy real-time management
of the radiation exposure of medical staff by
using wireless communication.
• As the system is designed to use a tablet, high
expandability can be achieved.
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Thank you for your attention.
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