radiation protection and dosimetry for the medical...

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

5

2-4

5

3-4

5

4-4

5

6-4

5

7-4

5

8-4

5

9-4

5

10-4

5

11-4

5

12-4

5

13-9

5

14-9

5

15-9

5

16-9

5

17-9

5

18-1

45

19-1

45

20-1

45

21-1

45

22-1

45

23-1

45

26-1

45

27-1

45

28-1

45

29-1

45

30-1

45

31-1

45

32-1

45

33-1

45

34-1

45

C/M: Calculated value/Measured value

11

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

15

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.

16

• 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.

17

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

19

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

0.6

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]

26

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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