Investigation of a New LiF TLD Individual Dosimeter for

OEFZS--4644

Investigation of a New LiF TLDIndividual Dosimeter for Measuring

Personal Dose Equivalent Hp(d)

on Different Phantoms

Hua Jin, K.E. Duftschmid, Ch. Strachotinsky

OEFZS--4644 . September 1992

F O R S C H U N G S Z E N T R U M S E I B E R S D O R F

OEFZS--4644 September 1992

Investigation of a New LiF TLDIndividual Dosimeter for Measuring

Personal Dose Equivalent Hp(d)on Different Phantoms

Hua Jin *)Klaus E. Duftschmid **)Christian Strachotinsky **)

Institute of Atomic Agency/Peking *)

Hauptabteilung Strahlenschutz **)Bereich Lebenswissenschaften

Arbeitsbericht

F O R S C H U N G S Z E N T R U M S E I B E R S D O R F

INVESTIGATION OF A NEW LiF TLD INDIVIDUAL DOSIMETERFOR MEASURING PERSONAL DOSE EQUIVALENT Hp(d) ON DIFFERENT

PHANTOMS

Jin Hua*, K.E. Duftschmid and C. Strachotinsky*China Institute of Atomic Energy, Beijing

Institute for Radiation Protection , Austrian Research Centre Seibersdorf.Austria

Abstract: The paper describes a new LiF TLD dosimeter designed for measuring personaldose equivalent, Hp(d). Its energy and angular response have been studied in detail on aPMMA slab phantom using the conversion factors for TE slab phantom. According to theresults obtained with four types of different conversion coefficients and phantoms, i.e. aPMMA slab, Water slab, ICRU sphere and Alderson Rando phantom, the conversioncoefficients for the TE slab phantom are suitable for the calibration of TLD individualdosimeters on PMMA slab phantom. In the energy range 17 keV to 1250 keV the energyresponse for Hp(10) and Hp(0.07) is energy independent within -20% to 8.4% for frontalirradiation. For angles within ±60° the new TLD dosimeters indicate Hp(10) within 0 to 22.5%and Hp(0.07) within -11.1% to 1.3%,respectively.

1. INTRODUCTION

The International Commission on Radiation Units and Measurements (ICRU) introducednew quantities in radiation protection from external sources with its Reports 19[1] and 25[2] in1971 and 1976. Subsequently, a series of the comprehensive system of dose limitation wasproposed in the publication 26[3] of the International Commission on Radiation protection(ICRP) in 1977. The effective dose equivalent, HE, and skin dose equivalent, Hs, werestipulated for the basic limits on radiation protection. Unfortunately, all of these quantities arenot directly measurable. In ICRU Report 39[4], a set of measurable quantities, is defined, i.e.four new operational dose equivalent quantities, two of them, ambient dose equivalent H*(10)and directional dose equivalent, H'(0.07), for area monitoring, the other two, individual doseequivalent, penetrating, Hp(10) and individual dose equivalent, superficial, Hs(0.07), forindividual monitoring. These quantities provide an adequate and conservative estimate of HE

and Hs for external ionizing radiation most commonly encountered. In ICRU Report 43 [5], theCommission provided detailed considerations underlying the definition of these operationalquantities. In ICRU Report 47 [6], the Commission also provided guidelines for themeasurement of those quantities, i.e. new definitions of the new operational quantities,guidelines for the design and calibration of instrumentation and physical data for thecalibration of reference beams (conversion factors). The recommendations are limited toroutine radiation protection for photon and electron irradiations.

This paper confines itself to individual monitoring. The new quantity for individualmonitoring is Personal Dose Equivalent, Hp(d)[6]. This quantity is the dose equivalent in softtissue below a specified point on the body at an appropriate depth, (d). For weakly andstrongly penetrating radiation, a depths of 0.07 mm and 10 mm, respectively, is recommended.In the actual practice of individual monitoring, Hp(d) is not the quantity measured when thecalibration of the dosimeter is performed under a standardized set of conditions in a referenceradiation field. During the course of calibration, the new measurands can be linked by meansof conversion factors with the commonly used standards for exposure, X, air kerma, Ka, orphoton dose equivalent, Hx, directly or in intermediate steps. Therefore, an appropriate

phantom and conversion factors play an important role in the calibration of individualdosimeters.

The purpose of this work is the evaluation of the new TLD individual dosimeter developedfor directly measuring Personal Dose Equivalent in routine individual monitoring at AustrianResearch Centre Seibersdorf, using the conversion factors for TE slab as recommended inICRU Report 47 in the routine calibration of individual dosimeters on the surface of PMMAslab phantom. This involved investigation of energy and angular dependence of response onPMMA slab phantom and with the conversion coefficients for TE slab phantom. Thecharacteristic of these TLD dosimeters was checked on the four different phantoms, describedabove. Finally, the results are compared with four types of different conversion coefficients foreach phantom. The results show, that the conversion coefficients for TE slab phantom areappropriate for the calibration of TLD individual dosimeters on PMMA slab phantom.

2. EXPERIMENTAL SET-UP

2.1. New TLD personal dosimeter

The new TLD dosimeter consists of an TLD card and a new dosimeter holder. The TLD cardcarries two LiF chips of Harshaw TLD-100 material with the dimensions 3.2*3.2*0.8 mm3

between Teflon foils. The TLD card is contained in a new dosimeter holder with one 'openwindow' and one 'shielded window' in the front of the two TLD chips. The new holder isshown in Figure 1. It consists of a thin foil bag (Al 2.7 mg/m2, Pet 1.39 mg/m2, Co-polyamid0.94 mg/m2) containing the TLD card, and a plastic holder made of polystyrene. The wallthickness of about 2 mm is nearly the same in front of and behind the detector. When the cardis inside the holder, chip 2 is opposite a hole in the front of the holder. The hole has a brass net(2 mm wire) covering 44% of the detector surface ("open window"). In the front of chip 3 asmall dome of 20 mm diameter, 5.4 mm thickness and 5 mm radius is mounted, made from thesame material as the plastic holder ("shielded window"). On the rear side a 0.25 mm Copperfilter is mounted inside the holder. This way Hp(10) is measured under the "shieldedwindow"and Hp(0.07) under the "open window".

2.2. Calibration facilities

The experiments of energy and angular responses were calibrated for the narrow spectraseries (very heavy filtering) X-ray and for Gamma radiation specified in ISO-standard4037 [7]. The X-ray irradiation were performed by using a very stable X-ray equipment(PHILIPS MG 320). The experimental arrangement for the calibration with X-rays is shown inFigure 2. In practice, for calibration of individual dosimeters, often a broad and approximatelyparallel beam for an X ray tube is used, this may be considered to approximate an expandedand aligned field. In our experiment the distance between the source and reference points ofmeasurement was 2 m. The field diameter irradiating the phantom is about 25 cm. In actualindividual dosimeter calibration only one dosimeter (e.g. new holder of 5 mm * 3.7 mm) wasplaced in the centre on a phantom. In this area the dose rate across the axis was constant within1%. Therefore, this irradiation field can be considered to be homogeneous. The field at thereference point was calibrated with a spherical ionization chamber traceable to a primarystandard ionisation chamber via a monitor chamber to obtain photon dose equivalent, Hx, atthe calibration position. Photon dose equivalent Hx is defined as Hx=0.01(Sv/R)*X. For themeasurement with Gamma radiation from 60Co and 137Cs the irradiation system is a multi-source assembly in which the selected source is raised from an underground storage container

to the irradiation position in a cubic lead shield, with aconical ring-collimator according to ISO4037 and an angular aperture of 15°. The 137 Cs (type CSC, No.212A, 3.88 TBq) and60Co(type COG, No. 11-65, 875 GBq) irradiation were made at a source-to-dosimeter distanceof 3 m. For Gamma irradiation an additional 5 mm PMMA shield was placed in front of thedosimeter to provide secondary electronic equilibrium. The same distance was used for bothfree-air and phantom irradiation.

2.3. Phantom

Individual dosimeter should be calibrated in terms of Hp(d) in a phantom having thecomposition of the ICRU tissue and the same size and shape as the calibration phantom. Fordosimeters worn on the trunk, a suitable phantom is the ICRU sphere. It is evident that thisphantom represents the human body to be simulated as imperfectly as expected of anyhomogeneous geometric type. But the ICRU sphere dose not seem very well suited forpractical calibration for reasons of material and geometry, such as difficulty of fabrication ,lack of an exact substitute for the ICRU tissue composition, and difficulty for routinecalibration where several dosimeters will have to be affixed together on the phantom surface.At present, the calibration phantom proposed in ICRU Report 47 for photons is a 30*30*15cm3 slab phantom made of polymethyl methacrylate (PMMA). Its mass is close to that of theICRU sphere, and its backscatter characteristics are acceptably close to those of the humantrunk for photon irradiation. The PMMA slab phantom was used in the characteristicexperiments of the new TLD dosimeter. The other three types of different phantoms were usedto check its properties related to the limited phantom size and provide optimum conversioncoefficients. All phantoms used in this work are listed inTable 1.

TABLE 1. Phantoms Used for the Experiments

Phantom shapesphereslabslab

Alderson Phantom

Dimensions (cm)30 diam

30*30*1530*30*15

MaterialICRU TE

WaterPMMA

TE

AuthorityICRUIAEAICRU

Alderson res.lab.

3. MEASUREMENT METHODS

3.1. Readout of TL individual dosimeters

For the readout of the TL dosimeters the Harshaw TLD System 8800 Card Reader [8] andthe annealing oven type ULM 400 were used in the experiment. The photon dose equivalentfor each irradiation was 2 mSv corresponding to a exposure time of approx. 200 s. Themeasurement of each point used two TLD cards. Three reference cards were used in the specialcalibration for each readout cartridge. The complete measurement cycle consists of thefollowing steps:

1) X-ray or Gamma irradiation;2) Heating for 20 min at 93 °C;3) Cooling for 1.5 h at room temperature;4) TLD readout at temperature of 25°C/s up to the maximum temperature of 280°C with totalheating time of 13 s.

3.2. Evaluation procedure for obtaining Hp

Before use each card is calibrated in 137Cs irradiation field of 5 mSv photon dose equivalent.With an individual correction factor for each card, obtained by two calibrations for 85 cards areproducibility within less than ±1% can be achieved. The evaluation procedure is based on thefollowing equations:

3.2.1. Personal dose equivalent

where HxHp(d)/Ka

f

3.2.2.Response of TL:

where TL

Hp(d)=Hx*(Hp(d)/Ka)*f

photon dose equivalent in mSvconversion factor for air kerma in mSv/mGyconversion factor for the photon dose equivalent to airkerma in mGy/mSv

RS= TL/Hp(d)

TL reading corrected for backgound and individualsensitivity in mSv

4. PERFORMANCE TESTING OF INDIVIDUAL DOSIMETERS

4.1. Energy response of new TLD dosimeter

According to the defined requirements of the new operational dose equivalent quantitiesbased on ICRU Publication No.39, the main difference between new and old quantities is, thatthe dosimeters are required to have a different energy response. In order to measure newPersonal Dose Equivalent it was necessary to design new individual dosimeters. At present, allTLD materials widely used, provide a reasonably flat energy respose above 200 keV fornormal incidence. At lower energies, the energy response depends not only on the effective Zof the TLD material but also on its dimention and on the thickness and effective Z of thesurrounding material. A new energy compensating holder for the LiF (TLD-100) cards hasbeen optimised experimentally by irradiating the dosimeters on the surface of a 30*30*15 cm3

slab phantom made of polymethyl methacrylate (PMMA) at the position of the dosimeter.The new TLD dosimeters were calibrated in ^Co and 137Cs photon sources, as well as heavilyfiltered Bremsstrahlung of the ISO narrow spectra series in the energy range from 12 keV to1250 keV. By definition, the energy response of a dosimeter is the ratio of the reading TL andthe actual dose equivalent Hp(10) and Hp(0.07) at a certain energy. The relevant conversionfactors Hp(d)/Ka for different directions of radiation incidence have been taken fromGrosswendt, report PTB-DOS-11 and IEC 1066 standard. All of conversion coefficients usedin this work is listed in Table 2.

TABLE 2 Conversion Factors for Energy Dependence, ISO Narrow Spectra Series

Energy,keV

def.phantom

ICRU-sphere

TE-slab

PMMA-slab

Water cube

12.5

0.123

0.069

0.11

0.0565

17

0.355

0.281

0.36

0.254

26

0.818

0.79

0.91

0.762

33

1.189

1.174

1.33

1.143

48

1.58

1.65

1.85

1.625

65

1.741

1.884

2.084

1.887

83

1.704

1.868

2.024

1.883

100

1.635

1.797

1.916

1.815

118

1.573

1.713

1.81

1.735

161

1.457

1.562

1.622

1.578

205

1.393

1.478

1.519

1.488

248

1.357

1.422

1.454

1.428

662

1.196

1.216

1.234

1.227

1250

1.151

1.168

1.148

1.172

reference

[9]

[10]. [11]*

[10], [11]*

[10], [11]*

Hp(0.07)/Ka

Energy.keV

ICRU-sphere

TE-slab

PMMA-slab

Water cube

0

0.957

0.95S

0.964

0.958

15

0.988

0.987

1.005

0.985

30

1.123

1.098

1.164

1.092

45

1.291

1.265

1.37

1.252

60

1.506

1.551

1.681

1.538

65

1.618

1.718

1.841

1.714

83

1.596

1.709

1.808

1.722

100

1.544

1.663

1.739

1.67

118

1.501

1.605

1.67

1.617

161

1.41

1.484

1.533

1.501

205

1.349

1.417

1.451

1.428

248

1.312

1.375

1.402

1.381

662

1.174

1.209

1.228

1.217

1250

1.138

1.168

1.159

1.193

reference

[9]

[10], [11]*

[10]**, [11]*

[10], [11]*

u-j

Note * only for Gamma radiation

** for 0.0Irnrn depth

The conversion coefficients relating to air kerma are converted to that relating photondose equivalent by multiplying by the photon dose equivalent (mSv) to air kerma in air(Gy) conversion factors which varies somewhat (0.87 to 0.96) with photon energy (10 keVto 10 MeV). In order to provide an optimised set of conversion coefficients used on PMMAslab phantom, the other three types of phantoms were used in the calibration of new TLDdosimeters, and four types of different conversion coefficients were used in comparisonwith each other for every phantom. All of graphs show the energy dependence of responsenormalised to that for the 137Cs reference radiation. Figure 3 shows the energy dependenceof two LiF chips of the type TLD-100 card in free air. The difference between two LiFchips response is within ±5%. This is yet the same 5% difference within LiF chips responsegiven by manufacturer. The energy response at lower energies is higher. Figure 4 shows theenergy dependence of the optimised holder in free air. The open window corresponds tochip 2, calculated for Hp(0.07), the shielded window corresponds to chip 3, calculated forHp(10).

Figure 5, 6, 7, 8, 9, 10, 11 and 12 separately show the energy response of new TLDdosimeters used in measuring Hp(10) (shielded window) and Hp(0.07) (open window) usingfour types of different conversion factors for each phantom. For shielded window the resultscompared with four different phantoms showed a large difference below 30 keV. For theconversion factors for TE slab phantom and for the Water cube phantom above 25 keV photonenergy the results for all backscatter phantoms are very close together. Except below 25 keV,the conversion factors for ICRU sphere phantom were the best one for the PMMA slab andWater slab phantom within ±5%, for the Alderson phantom within ±10%, and for itselfphantom within -19% to 23% in the energy range from 17 keV to 1250 keV. The conversionfactors for PMMA slab phantom are obviously to low. For open window, all graphs wereclose. The energy dependence of new TLD dosimeters on four types of different phantoms andusing four different conversion factors were listed in Table 3

TABLE 3 Comparison of Energy Dependence Using DifferentConversion Factors and Phantoms

Shielded window

Conv. factorsEnergy, keVPhantomPMMA-slabWater-slabICRU-sphereAlderson

TE-slab17

-20-19-13-15

to(«totototo

1250J)

8.49.529.513.4

Water-cube17

-10-11-12-13

to(9?totototo

1250,)

13.414.535.418.3

PMMA-slab17

-36-35-17-33

to(*totototo

1250>)

4.16.7141.5

ICRU-sphere17

-37-37-19-34

to(%totototo

1250)4.24.12310.2

Open window

PMMA-slabWater-slabICRU-sphereAlderson

-20-23-17-20

totototo

5.50.35.20

-20-22-16-19

totototo

5.40.33.70

-20-23-17-20

totototo

4.70.87.70

-23-25-20-22

totototo

7.64.94.90

Figure 13 and 14 show the results obtained with the conversion factors for TE slab phantomcompared with the different phantoms in units of personal dose equivalent. For shieldedwindow these graphs give the results for use of the same conversion factors for TE slabphantom for irradiations on PMMA salb, the Water slab and the Alderson Rando phantom,over 17 keV photon energies. Of cause, it can be seen that the conversion factors for that arealso suitable for ICRU sphere phantom above 33 keV photon energy. The difference at lowerenergies is mainly caused by the different material and shape of phantom. We can also see thatthe conversion factors differ slightly with the photon spectrum as well.

The differences among these factors, perhaps due to their steep variation with energy,especially in the low energy, are sometimes even higher than 50%. Measuring Hp(10) in thelower energies is very sensitive to backscatter, and for measuring Hp(0.07) all of them is veryclose together, because for weakly radiation, backscatter for the phantom is not significantlydifferent from backscatter from a sufficiently thick plane slabs, since the range of commonlyencountered weakly radiation in the material of phantoms is small compared with the thicknessof the phantom.

Figure 15 and 16 indicate, that for the shielded window the same results are obtained as forthe conversion factors for Water cube phantom used in Water slab phantom, for ICRU spherephantom used in itself, and for PMMA slab phantom used in itself. For open window there isstill no large difference.

From the above results, it can be seen that the energy dependence of the new TLD individualdosimerters is in agreement within -20% to 23% in the mean photon energy range from 17 keVto 1250 keV for three types of different phantoms.

4.2. Angular response of new TLD dosimeter

Two major sources of inaccuracy in individual dosimetry are the energy response andangular response of individual dosimeter. The angular response performance of the new TLDdosimeter in terms of the Personal Dose Equivalent Hp(d,a) (a defined as incidence angle) isdiscussed.

For the angular response study the new TLD dosimeter was irradiared on the verticalcentreline of a PMMA slab phantom (30*30*15 cm3) at a certain front-incident angle. Forvertical irradiation (see Fig 1, ROT AXIS B) , the top of the dosimeter was toward the top ofphantom. For horizontal irradiation (see Fig 1, ROT AXIS A) the top of the dosimeter wastoward the right side of phantom. For both vertical and horizontal irradiation, clockwiserotation of the phantom about its vertical axis centreline gives negative angle of incidence andcounterclockwise rotation gives positive angles.

The angular response of the new TLD dosimeter was studied by the values calculated byGrosswendt and IEC 1066 standard (listed in Table 4).

TABLE 4 Conversion Factors for Angular Dependence, ISO Narrow Spectra Series

Hp(10, a)/K

a,(°)ICRU-sphcreTE-slabPMMA-slabWater-cube

01.5991.6501.8501.625

151.5801.6241.8321.604

301.5251.5691.7581.555

451.4201.4601.6111.448

601.2641.2391.3581.233

Reference[13][10][10][10]

Hp(0.07, a)/Ka

a,(°)ICRU-sphereTE-slabPMMA-slabWater-cube

01.5511.5381.6811.492

151.5451.5291.6861.482

301.5251.5181.6561.465

451.4801.4831.5921.433

601.4021.3951.4941.372

Reference[13][10][10]*[10]

Note * for 0.01 mm depth

The angles of incidence included -60°,-45°, -30°, -15°, 0°, 15°, 30°, 45°, 60°. Thedistance of the source - to vertical centreline of the phantom was 2000 mm for the X-ray (beamcode A60, average energy 48 keV). The responses at non-perpendicular irradiation werenormalized to the response at perpendicular incidence. The angles of all graphs were limited to±60°.

Figure 17 shows the related angular response of new TLD dosimeter in the verticalirradiation in free air in unit of photon dose equivalent. The mean absolute differences for theshielded window are less than 5% for angles within ±60°. For open window the maximumdifferences are within -23% to 16%.

Figure 18 and 19 show the angular response of new TLD dosimeters in the vertical andhorizontal irradiations on the surface of PMMA slab phantom, respectively .These graphs showthe vertical irradiation better than horizontal that. For shielded window the maximumdifference is within -1.4% to 25%, while, for open window that is within -15% to 2%. Theconversion factors for TE slab phantom were used. Both differences are the reason due to thegeometric shape of dosimeter.

Figure 20, 21, 22, 23, 24, 25, 26 and 27 show the results compared with using four differentconversion factors for each phantoms. We can find the same results for the TE slab and Watercube phantoms conversion factors, meanwhile, also find the best one for using conversionfactors for ICRU sphere phantom. In such situation the angular independent for shieldedwindow and open window for angles within ±60° is listed in Table 5.

Figure 28 and 29 show the results of using conversion factors for TE slab phantom to four

different phantoms. The results for PMMA slab and Water slab phantom are very close forshielded window, and that for ICRU sphere and Alderson Rando phantoms is slightly different.This also present that the phantom shape and the worn on position play an important role. Foropen window it hadn't large difference.

Figure 30 and 31 show the results for three different phantoms and using themselfconversion factors. All of them is within -1.8% to 25% for shielded window and within -16%to 1.5% for open window.

TABLE 5 Comparison of Angular Dependence Using DifferentConversion Factors and Phantoms

Shielded window

Conv. factorsAngular, degreePhantomPMMA-slabWater-slabICRU-sphereAlderson

PMMA-slabWater-slabICRU-sphereAlderson

TE-slab-60

0-1-1.40

-11.1-15.8-11.4-31.7

to(%

totototo

totototo

60)22.520.2223.128.9

1.30.602.5

Water-cube-60

0-1-1.7-0.2

Open

-11.1-16.1-11.7-32.0

to(%

totototo

60)21.21921.827.6

window

totototo

1.50.801.4

PMMA-slab-60

0-1.3-2.00

-9.6-13.4-9.6-30.6

to(%

totototo

totototo

60)25.32325.931.9

0.6003.2

ICRU-sphere-60

0-1.1-1.80

-12.3-16.3-12.9-33.0

to(%

totototo

totototo

60)16.814.216.922.4

1.70.701.8

5. COMPENSATION METHODS DEVELOPED FOR INDIVIDUAL DOSIMETERS

For the development of an individual dosimeter for personal dose equivalent not only theproperties of the detectors , but also the properties of the phantom used for calibration have tobe considered. In developing the new TLD dosimeters we used the compensation methods fordetectors and a PMMA slab phantom and conversion factors for TE slab phantom.

When the compensation methods were used, we considered either front incidence irradiationor the backscatter effect of the phantom. For the front incidence irradiation we mainly changedthe shielding thickness of the front detector, and for the backscatter effect, we used a copperfilter to absorb the backscatter irradiation.

Fig 32 shows the energy dependence of the response of new TLD dosimeters front thedifferent shielded thickness of plastic and behind the different thickness of copper filters forthe shielded window. We can see that the respc.ise doesn't vary with front shield thicknessabove 33 keV, but it varies with the rear shield thickness. Below 33keV energy range we canalso see that the response varies considerably with the front shield thickness. The bestcompensation method was obtained with a front shield of 5.4 mm plastic and a rear shield 0.25

mm copper for the shielded window.

Fig 33 shows the energy response of the new TLD dosimeters with different front shieldingand a rear shield of 0.25mm copper. The best results are obtaines with a copper disc of 32%shielded area and 2mm thickness. But this case is not very suitable for routine individualdosimeter production. Therefore we used a Brass net of 44% shielded area and 2mm wire.

6. CONCLUSION

For individual dosimeters used for routine monitoring not only a good energy and angularresponse is required, but also economy and easy operation are considered. The new LiF TLDdosimeter tested in this work have been proved to be basicaly satisfying.

With the energy compensation holder optimised for Hp(10)and Hp(0.07), the energyresponse of new LiF TLD dosimeter is within -20% to8.4% over an energy range of 17 keV to1250 keV. The angular dependence of the new TLD dosimeters is within 0 to 22.5% forHp(10) and within -11.1% to 1.3% for Hp(0.07) for the incidence angles from -60 to 60degrees.

As Figure 13 and 14 show, the same results of the calibration on the surface of PMMA slabphantom as that of Alderson-Rando phantom and for both using convertion factors for TE slabphantom are obtained. This new TLD dosimeter will closely indicate personal dose equivalent,Hp(10) and Hp(0.07), when worn on the human trunk.

Our experiment showed, that a PMMA slab phantom and the conversion coefficients for TEslab phantom are very suitable for routine calibration Except below 25 keV, the results are thesame using conversion coefficients for TE slab phantom as well as for the Water cubephantom. Above 25 keV the conversion factors for ICRU sphere phantom provided the bestresults for the PMMA slab, water slab and the Alderson Rando phantoms.

7. REFERENCES

1. ICRU Report 19, Dose Equivalent and Unit, 1971.2. ICRU Report 25, Conceptual Basis for the Determination of Dose Equivalent, 1976.3. ICRP Publication 26, Recommendations of the International Commission on Radialogical

Protection, 1977.4. ICRU Report 39, Determination of Dose Equivalent Resulting for External Radiation Sources,

1985.5. ICRU Report 43, Determination of Dose Equivalents from External Radiation Sources-Part 2,

1988.6. ICRU Report 47, Determination of Dose Equivalent from External Photon and Electron

Radiations, 1992.7. ISO, X and Gamma Reference Radiation for Calibrating Dosemeters and Dose Ratermeters

and for Determining their Response as a Function of Energy, ISO 4037,1979.8. HARSHAW/FILTROL TLD System 8800 Card Reader User's Manual, for Use with Radiation

Evaluation and Management System, 1988.9. PTB-Dos-1 le, Conversion Factors for ICRU Dose Equivalent Quantities for the Calibration of

Radiation Protection Dosimeters, 1988.

10

lO.Grosswendt. BM Coefficients for the Conversion of Air Collision Kerma to Dose Equivalentfor the Calibration of Individual Dosemcters in X ray Fields, Radia. Prot. Dl.Grosim. 40, 3,169-184, 1992.

1 l.Gosswendt. B., The Angular Dependence and Irradiation Geometry Factor for the DoseEquivalent for Photon in Slab Phantom of Tissue-Equivalent Material and PMMA, Radia.Prot. Dosim., 35,4, 221-235, 1991.

12.Grosswedt. B., Conversion Factors for the IAEA Cube Phantom for External PhotonIrradiation, Radia. Prot. Dosim., 29, 3, 177-188, 1989.

13.CEI IEC 1066, Thermoluminescence Dosimetiy System for Personal and Environmentalmonitoring,1991.

11

ROT AXIS A

X^^V/////////////^^^^

fig 1 TL-badge

FIG. 2 320-kV X-ray machine Experimental setup

Energy dependenceBacksc. phantom: noneQuantity for: photon dose equivalent, HxHolder: only card

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

Mean values

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

_L10 20 30 40 50 60 70 80 90100

Photon energy ( keV )

200 300 400 500 600 700 800900000

Füg 3 The energy dependence of LiF TLD-100 card in free air

Energy dependenceBacksc. phantom: noneQuantity: photon dose equivalent, HxHolder: final holdei

10

• Open window

V Shielded window

20 30 40 50 60 70 80 90100 200


300 400 500 600 700 800900000

Fig 4 The energy dependence of the optimised holder bagged LiF card in free air

Energy dependenceBacksc. phantom: PMWA slobHolder: final holder

Shielded window

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2i>

£ 1.1oa.S 1.0i_

t 0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

Quantity

v H (10) for water cube phantom

e H (10) for TE slab phantom

D H (10) for ICRU sphere phantom

H (10) for PMMA slab phantomp . . .

I10 20 30 40 50 60 70 80 90100 200


300 400 500 600 700 800900000

Fig 5 The energy response of new TLD dosimeters on the surface of PMMA slab phantom andusing four types of different conversion factors

Energy dependenceBacksc. phantom: Water slabHolder: final holder

Shielded window

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1 -

Quantity


• H (10) for TE slab phantom


• H (10) for PMMA slab, phantom

_L I

10 20 30 40 50 60 70 80 90100 200


300 400 500 600 700 800900000

Fig 6 The energy response of new TLD dosimeters on the surface of water slab phantom andusing four types of different conversion factors

Energy dependenceBacksc. phantom: ICRU sphereHolder: final holder

Shielded window

coa

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2 -

0.1 -

V.

Quantity


O H (10) for TE slab phantom

H (10) for PMMA slab, phantom

_L10 20 30 40 50 60 70 80 90100 200 300 400 500 600 700 800900000


Fig 7 The energy response of new TLD dosimeters on ICRU sphere phantom andusing four types of different conversion factors

Energy dependenceBacksc. phantom: Alderson RandoHolder: final holder

Shielded window

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

& 0.9

0.8

0.7

0.6

0.5 -

0.4

0.3 -

0.2 -

0.1 -

Ouantity


• H (10) for TE slab phantom '


H (10) for PMMA slab phantomp . . .

_L10 20 30 40 50 60 70 80 90100 200 300 400 500 600 700 800900000


Füg 8 The energy response of new TLD dosimeters on Alderson Rando phantom andusing four types of different conversion factors

Energy dependenceBacksc. phantom: PMMA slabHolder: final holder

Open window

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

10 20 30 40 50 60 70 80 90100

Quantity

v H (0.07) for water cube phantom

9 H (0.07) for TE slab phantom • •

D H (0.07) for ICRU sphere phantom

H (0.07) for PMMA slab phantom

=iüf

200 300 400 500 600 700 800900000


Fig 9 The energy response of new TLD dosimeters on PMMA slab phantom andusing four types of different conversion factors

Energy dependenceBacksc. phantom: Water slabHolder: final holder

Open window

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

Quantity


O H (0.07) for TE slab phantom


H (0.07) for PWMA slab phantom

I J_10 20 30 40 50 60 70 80 90100 200 300 400 500 600 700 800900000


Fig 10 The energy response of new TLD dosimeters on Water slab phantom andusing four types of different conversion factors

Energy dependenceBacksc. phantom: ICRU sphereHolder: final holder

Open window

«

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2 -

0.1 -

Quantity


• © H (0.07) for TE slab phantom • •

D H'(0.07)

T H (0.07) for PMMA slab phantom

I I

10 20 30 40 50 60 70 80 90100 200


300 400 500 600 700 800900000

Fig 11 The energy response of new TLD dosimeters on ICRU phantom andusing four types of different conversion factors

Energy dependenceBacksc. phantom: Alderson RandoHolder: final holder

Open window

2.0

1.9

1.8

1.7

1.6

1.5

1.4

Quantity


' O H (0.07) for TE slab phantom " •



coQ.

1.2

1.1

1.0

1 0.9

0.8

0.7

0.6

0.5

0.4

0.3

C.2

0.1

J_10 20 30 40 50 60 70 80 90100


200 300 400 500 600 700 800900000

Fig 12 The energy response of new TLD dosimeters on Alderson Rando phantom andusing four types of different conversion factors

Energy dependenceQuantity for: TE slab phantom, H (10)Holder: final holder

Shielded window

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

02

0.1

Backsc.phantom

v water slab

• e PMMA- slab •

D ICRU sphere

• Alderson Rando

i I , , I10 20 30 40 50 60 70 80 90100 200


300 400 500 600 700 800900000

Fig 13 The energy responses of new TLD dosimeters for four types of different phantomsand using conversion factors for TE slab phantom

Energy dependenceQuantity for: TE slab phantom, H (0.07)Holder: final holder

Open window

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

£ 0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2 -

0.1 -

Backsc.phantom

v water slab

• PMMA slab

a ICRU sphere

T Alderson Rando

L10 20 30 40 50 60 70 80 90100 200


300 400 500 600 700 800900000

Fig 14 The energy responses of new TLD dosimeters for four types of different phantomsand using conversion factors for TE slab phantom

Energy dependenceHolder: final holder Shielded window

a.V)V

a:

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6 -

0.5 -

0.4 -

0.3 -

0.2 -

0.1 -

H (10) for water cube phantom

Backsc.phantom Quantity

• water slab

• tCRU sphere

V PMMA slab H (10) for PMMA slab phantom

10 20 30 40 50 60 70 80 90100 200 300 400 500 600 700 80090Q000


Fig 15 The energy responses of new TLD dosimeters on different phantoms and using themself conversion factors

Energy dependenceHolder: final holder Open window

2.0

1.9

1.8

1.7

1.6

1.5

1.4

Backsc.phantom

C water slab

• ICRU sphere '

v PMMA slab

Quantity

H (0.07) for water cube phantom

H'(0.07)


a>

1.2

1.1

R 1.0a>

K 0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1i i i i i—l—

50 60 70 80 90100_L

10 20 30 40 200 300 400 500 600 700 800900000


Fig 16 The energy responses of Tin '!•>•-. •""•«"•, <"»nl phantoms and using themself conversion factors

Angular dependence

Backsc. phantom: free airQuantity for: photon dose equivalentHolder: final holder

2.6

2.5

2.4

2.3

2.2

2.1

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

1 1

1 1

1

- -

-

l l l

...". —-V--

1 1 1

0 Open window

V Shielded window

~ - - — - - ^ 7

- •

i i i-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fig 17 The a n g u l a r r e s p o n s e of now TIP dn«imr»#T"5 in frro nir

Angular dependenceBacksc. phantom: PMMA slabQuontity for: TE slab phantomHolder: final holder

2.6

2.5

2.4

2.3

2.2

2.1

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7 -

0.6 -

0.5

0.4

0.3

0.2 -

0.1 -

0.0

• Open window (for H (0.07))

V Shielded window (for H (10))

_L _L-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fig 18 The angular response of new TLD dosimeters in the vertical radiation and on PMMA slab phantom

Angular dependenceBacksc. phantom: PMMA slabQuantity for: TE slab phantomHolder: final holder

a>toco

2.6

2.5

2.4

2.3

2.2

2.1

2.0

1.9

1.5

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3 -

0.2

0.1 -

0.0

Open window (for H (0.07))

Shielded window ( for-H (10))p

- V

-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fig 19 The angular response of new TLD dosimeters in the horizontal irradiation on PMMA slab phantom

Angular dependenceBacksc. phantom: PMMA slabHolder: final holder

Shielded window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

Si 1.05

c

| 1 0 °j> 0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50 i I i

Quantity

V Hp (10) for. water cube phantom

• Hp (10) forTE slab phantom

n Hp (10) for. ICRU sphere phantom

'. H (10) for. PMMA slab phantom

-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fie 20 The angular response of new TLD dosimeters on water slab phantom and using four types ofconversion factors

Angular dependenceBacksc. phantom: Water slabHolder: final holder

Shielded window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

S 1-05c

I 10°J5 0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

D

JL _L _L _L

Ouantity

V Hp (10) for water cube phantom

• Hp (10) for'TE slab phantom

o Hp (10) for ICRU sphere phantom

T Hp (10) for. PMMA slab phantom

-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0


Angular dependenceBacksc. phantom: ICRU sphereHolder: final holder

Shielded window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

£ 1.05cI 1-00j> 0.95

0.90

0.85

0.80

0.75

0.70

0.65 --

0.60 -

0.55 -

0.50

Quantity


• H (10) for TE slab phantom

D

H (10) for PMMA slab phantom

_L-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fig 22 The angular response of new TLD dosimeters on ICRU sphere phantom and using four types ofconversion factors

Angular dependenceBacksc. phantom: Alderson RandoHolder: final holder

Shielded window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

1.05

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

Quantity

V H (10) for water cube phantom

O H (10) for TE slab phantom

a H (10) for ICRU sphere phantom

•. H (10) for PMMA slab phantom

_L _L-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fig 23 The angular response of new TLD dosimeters on Alderson Rando phantom and using four types ofconversion factors

Angular dependenceBacksc. phantom: PMMA slabHolder- final holder

Open window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

SS 1.05cI 1-00j> 0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55 -

0.50

Quantity

V Hp (0.07) for water cube phantom

O Hp (0.07) for TE slab phantom

a Hp (0.07) for ICRU sphere phantom

T. Hp (0.07) for PMMA slab phantom

-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fig 24 The angular response of new TLD dosimeters on water slab phantom and using four types ofconversion factors

Angular dependenceSocksc. phantom: Water siobHolder: final holder

Open window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

S 1.05

I 1.00

«>' 0.95

0.90

0.85

0.80 -

0.75 -

0.70

0.65 -

0.60 -

0.55 -

0.50 _L _L

Quantity

v Hp (0.07) for water cube phantom

• Hp (0.07) for TE slab phantom

a Hp (0.07) for ICRU sphere phantom

•. Hp (0.07) for PMMA slab phantom

-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0


Angular dependenceBacksc. phantom: ICRU sphereHolder: final holder

Open window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

1.05

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

Quantity


O H (0.07) for TE slab phantom

D H"(0.07)


_L

-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fig 26 The angular response of new TIT) dos-imHrrs on ICKW sphere phantom and using four types ofconversion factors

Angular dependenceBacksc. phantom: Alderson RandoHolder: final holder

Open window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

£ 1-05

I 1.00

j> 0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50 JL

Quantity

V H (0.07) for wuter cube phantom

• H (0.07) for TE slab phantom


T H (0.07) for.PMMA slab phantom

-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fig 27 The anqular r e s p o n d <•'

movers"")

fnur (ypps of

Angular dependenceQuantity for: TE slab phantom, H (10)Holder: final holder

Shielded window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

S 1.05

S- i.oo

j> 0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

Backsc. phantom

v Water slab

T PMMA slab

• ICRU sphere

• Alderson Rando

- - • < ?

_L-60.0 -45.0 -30.0 -15.0 0.0 15.0

Angular (degree)

30.0 45.0 60.0

Fig 28 The angular response of new TLD dosimeters on four types of different phantoms and using conversionfactors of TE slab phantom

Angular dependenceQuantity for: TE slab phantom. H (0.07)Holder: final holder

Open window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

1-05

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60 -

0.55 -

0.50

Backsc. phantom

V Water slab .

T PMMA slab

a ICRU sphere

• Alderson Rando

J_ _L-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fig 29 The angular response of new TLD dosimeters on four types of different phantoms and using conversionfactors of TE slab phantom

Angular dependenceHoldenfinal holder Shielded window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

1.05

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60 -

0.55 -

0.50

Backsc.phantom

V Water slab

• PMMA slab

v ICRU sphere

Quantity

H (10) for water cube phantom

H (10) for PMMA slab phantom

H (10) for ICRU sphere phantom

_L J_-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fig 30 The angular response of new TLD dosimwters on different phantoms and using itself conversion factors

Angular dependenceHolder.final holder Open window

1.50

1.45

1.40

1.35

1.30

1.25

1.20

1.15

1.10

1.05

1.00

0.95

0.90

0.85

0.80

0.75

0.70

0.65

0.60

0.55

0.50

Backsc. phantom

V Water slob -

• PMMA slab '

T ICRU sphere

Quantity

H (0.07) for water cube phantom


H (0.07) for ICRU sphere phantom

_L J_ _L-60.0 -45.0 -30.0 -15.0 0.0

Angular (degree)

15.0 30.0 45.0 60.0

Fig 31 The angular response of new TLD dosimwters on different phantoms and using itself conversion factors

Phantom: PMMA slabQuantity for: TE slab phantom. Hp(10) Shielded window

ShD

•

A

•O

V

•

•

ielded (plastic)5mm5.3mm.5.3mm5.5mm5.4mm.6mm

6mm

6mm

Backs(copper)0.4mm0.15mm .0.3mm0.2mm

. 0.25mm. .0.3mm0.2mm ' '

50 60 70 80 90100 200 300 400 ?00 600 700 800900000


Fig 32 Relative energy response of LiF (TLD-100) to H (10) front and behind different filters

Phantom: PMMA slobQuantity for: TE slab phantom, Hp(0.07) Open window

2.0

1.9

1.8

1.7

1.6

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2 -

0.1

Front shieldedO 32% copper disc

v 44% Brass net (0.2mm wire)

T 60% copper net (0.1mm wire)

Backs (copper)0.25mm

0.25mm

0.25mm

I I

10 20 30 40 50 60 70 80 90100 200


300 400 500 600 700 800900000

Fig 33 Relative energy response of LiF (TLD—100) to H (0.07) front and behind different filters

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