Monitoring the eye lens

Transcription

1 Funding TS7e.3 Rolf Behrens Physikalisch-Technische Bundesanstalt

2 Introduction April 2011: Limit of H lens : 150 msv 20 msv per year Protecting and monitoring may be necessary! Main question: Which quantity / kind of dosemeter is suitable? (0.07), (3) or (10)? (3) should work well, BUT: not used in the past, Method: only few dosemeters available. Compare indication of ideal dosemeters and H lens, i.e. compare conversion coefficients for (d) and H lens Only valid for dosemeters worn near the eye and below eye protection equipment when used! 2

3 Data base Operational quantity (Dose equivalent)? > Organ dose to the lens (Equivalent dose)? = ICRU / ISO ORAMED hp Radiation Quantity Data source ( d; E) h lens Quantity ( E) Data source Electrons (0.07) slab (3) slab (10) slab (3) cyl } ICRP74 + ICRU57 Ferarri and Gualdrini H lens ICRP116 (Rev. ICRP74); Behrens Photons (0.07) slab (10) slab (0.07) rod (3) slab (3) cyl } ICRP74 + ICRU57 Grosswendt Till et al. Vanhavere et al. H lens ICRP116 (Rev. ICRP74); Behrens and Dietze 3

4 Data base Biology Organ dose to the lens Simulation Complete lens: ICRP state of art 4

5 Data base Biology Organ dose to the lens Simulation R. Behrens et al. in Phys. Med. Biol. (PMB): PMB 54 (2009) PMB 55 (2010) 3937, PMB 56 (2011) 415 and PMB 57 (2012) submitted Sensitive cells: In ICRP discussion 5

6 Photon radiation: (d) / H lens (based on complete lens) (d) / H lens (0.07) slab (10) slab rod slab ICRU / ISO (3) cyl (3) slab (0.07) rod = kev 1000 E ph cyl ORAMED ICRP state of art Conservative Not conservative Lack of backscatter Too much absorption Only valid for dosemeters worn near the eye and below eye protection equipment when used! 6

7 Photon radiation: (d) / H lens (based on complete lens) (d) / H lens (0.07) slab (10) slab rod slab ICRU / ISO (3) cyl (3) slab (0.07) rod = kev 1000 E ph cyl ORAMED ICRP state of art Conservative Not conservative Lack of backscatter Too much absorption Only valid for dosemeters worn near the eye and below eye protection equipment when used! 7

8 Photon radiation: (d) / H lens (based on complete lens) (d) / H lens (10) slab rod slab ICRU / ISO (3) cyl = 90 (0.07) rod (0.07) slab (3) slab kev 1000 E ph cyl ORAMED ICRP state of art Conservative Not conservative Only cyl.-ph. suited Absorption in edge of slab phantom Only valid for dosemeters worn near the eye and below eye protection equipment when used! 8

9 Electron radiation: (d) / H lens (based on complete lens) (0.07) slab = 0 (d) / H lens (3) slab (3) cyl (10) slab MeV 10 E el ICRP state of art Conservative Not conservative Lack of dose build-up Too much absorption Only valid for dosemeters worn near the eye and below eye protection equipment when used! 9

10 Electron radiation: (d) / H lens (based on complete lens) (0.07) slab = (3) cyl ICRP state of art (d) / H lens MeV 10 E el (3) slab (10) slab Conservative Not conservative Too much absorption Only valid for dosemeters worn near the eye and below eye protection equipment when used! 10

11 Electron radiation: (d) / H lens (based on complete lens) (0.07) slab = (3) cyl ICRP state of art (d) / H lens (3) slab (10) slab MeV 10 E el Conservative Not conservative Too much absorption Too much absorption Only valid for dosemeters worn near the eye and below eye protection equipment when used! 11

12 Electron radiation: (d) / H lens,s (based on sensitive cells) (0.07) slab,s = 0 (d) / H lens,s (3) slab,s (3) cyl,s (10) slab,s MeV 10 E el In ICRP discussion Conservative Not conservative Lack of dose build-up Too much absorption Only valid for dosemeters worn near the eye and below eye protection equipment when used! 12

13 Electron radiation: (d) / H lens,s (based on sensitive cells) (0.07) slab,s = 60 (d) / H lens,s MeV 10 E el (3) cyl,s (3) slab,s (10) slab,s In ICRP discussion Conservative Not conservative Too much absorption Too much absorption Only valid for dosemeters worn near the eye and below eye protection equipment when used! 13

14 Electron radiation: (d) / H lens,s (based on sensitive part) (0.07) slab,s = (3) cyl,s In ICRP discussion (d) / H lens,s (3) slab,s (10) slab,s MeV 10 E el Conservative Not conservative Too much absorption Too much absorption Only valid for dosemeters worn near the eye and below eye protection equipment when used! 14

15 Conclusions Operational quantity (Dose equivalent)? = ICRU / ISO ORAMED Radiation Quantity Good to estimate H lens? Good to estimate H lens,s? Photons Electrons equal for realistic radiation fields (0.07) rod (10) slab (0.07) slab (3) slab (3) cyl (0.07) slab (3) slab (3) cyl (10) slab } }? > ICRP state of art: Complete lens: H lens Underestimating Underest. up to 40 kev Up to 75 appropriate Up to 90 appropriate Extrem. overestimating Up to 60 appropriate Underestimating Organ dose to the lens (Equivalent dose) In ICRP discussion: Sensitive cells : H lens,s As for H lens Extremely overestimating Underestimating, (d<3) necessary? Underestimating 15

16 Same conclusions for realistic radiation fields (0.07) rod, i.e. ring dosemeters worn near the eye, suitable for photons? Radiation field (0.07) rod / H lens (0.07) slab / H lens (3) slab / H lens (10) slab / H lens Photons < 30 kev Photons > 30 kev Electrons < 0.6 MeV and photons see above Electrons < 0.6 MeV and photon x R. Behrens and G. Dietze: Phys. Med. Biol. 55 (2010) and Phys. Med. Biol. 56 (2011) 511 (0.07) slab is ONLY adequate for photon radiation. (3) is NECESSARY for beta radiation. (10) for e - & E ph 40 kev NOT adequate! 16

17 Extremity dosemeters suitable for the eye lens? Are extremity dosemeters (for (0.07)) appropriate? Is a calibration on a rod phantom (as usual) appropriate? Rod phantom Slab phantom R. Behrens et al.: Rad. Prot. Dosim. 148 (2012)

18 Extremity dosemeters suitable for the eye lens? R. Behrens et al.: Rad. Prot. Dosim. 148 (2012)

19 Extremity dosemeters suitable for the eye lens? Extremity dosemeters (for (0.07)) estimate the lens dose in pure photon radiation fields! 1.05 R rod / R slab R. Behrens et al.: Rad. Prot. Dosim. 148 (2012) MPA-TKD-01 LPS-TLD-TK 03 LPS-TLD-TK 07 LPS-TLD-TK 08 GSF-TL-TD-60 GSF-TL-TD-70 BE-TLD-TD-PHOTONEN 01 BE-TLD-TD-Brille Energy / kev 19

20 Photon ring dosemeters for (0.07) are available as eye lens dosemeters in Germany: MPA-TKD-01 with headband BE-TLD-TD-Brille GSF-TL-TD-60 also with headband LPS TLD-TK 07 20

21 Practice: Choice of dosemeters Whole body dosemeters measure (10): - must be worn on the trunk (far from the eyes); - underestimate at E ph <40 kev (too thick cover) - under the lead apron if in use; danger for the eyes! Extremity dosemeters measure (0.07): - must be worn facing the beam / source; - can be worn near the eye, then it - correctly estimate the lens dose in photon fields but - overestimates the lens dose in beta fields (too thin cover) work may be changed although not necessary! Eye dosemeters measure (3): - must be worn facing the beam / source; - must be worn near the eye; - is the only type of dosemeter that correctly estimate H lens (not H lens,s ) in beta and photon fields! Only valid for dosemeters worn near the eye and below eye protection equipment when used! 21

22 Funding TS7e.3 Rolf Behrens Physikalisch-Technische Bundesanstalt

23 Some additional material for meeting: October 2-4, 2012 Rolf Behrens Physikalisch-Technische Bundesanstalt

24 IEC standard (draft) on Protective Eyewear: (only for purposes on the basis of the liaison of and IEC TC62 / SC62B) 24

25 Irradiations and type tests in (3) Photon spectra: Conversion coefficients for K a (3) slab : Rad. Prot. Dosim. 147, 373 (2011) Conversion coefficients for K a (3) cyl : Rad. Prot. Dosim. doi: /rpd/ncs032 (2012) Beta radiation: Extension to the Beta Secondary Standard BSS 2: Incl. conversion factors for (0.07) (3): J. Instrum. 6, P11007 (2011) Available for old instruments via SW update Details: Poster P ICE 62387: Passive dosimetry systems (Final draft FIDS 2012) (3) implemented for both photons and betas 25

26 Early draft of ISO standard on lens, skin, extr. dosimetry: May be significantly changed in future versions! (only for purposes on the basis of the liaison of and ISO TC85 / SC2) From draft ISO From the contents: Current target date:

27 Early draft of ISO standard on lens, skin, extr. dosimetry: May be significantly changed in future versions! (only for purposes on the basis of the liaison of and ISO TC85 / SC2) From the contents: From draft ISO No conversion coefficients from K a to H (3) available! 27

28 Early draft of ISO standard on lens, skin, extr. dosimetry: May be significantly changed in future versions! (only for purposes on the basis of the liaison of and ISO TC85 / SC2) From the contents: From draft ISO

29 Early draft of ISO standard on lens, skin, extr. dosimetry: May be significantly changed in future versions! (only for purposes on the basis of the liaison of and ISO TC85 / SC2) From the contents: From draft ISO

30 Early draft of ISO standard on lens, skin, extr. dosimetry: May be significantly changed in future versions! (only for purposes on the basis of the liaison of and ISO TC85 / SC2) From the contents: From draft ISO for photons and betas - for (0.07) and (10) but NOT yet for (3) - for photons and betas - for (0.07), (3) and (10) 30

31 Literature : Which dose quantity is adequate? Phys. Med. Biol. 55, 4047 (2010) and Phys. Med. Biol. 56, 511 (2011) Conversion coefficients for mono-energetic electrons: H eye : Phys. Med. Biol. 54, 4069 (2009) and Phys. Med. Biol. 55, 3937 (2010) and J. Rad. Prot., to be published (including a whole body phantom) Conversion coefficients for mono-energetic photons: H eye : Phys. Med. Biol. 56, 415 (2011) (including a whole body phantom) Conversion coefficients for photon spectra: K a (3) slab : Rad. Prot. Dosim. 147, 373 (2011) Conversion coefficients for photon spectra: K a (3) cyl : Rad. Prot. Dosim. doi: /rpd/ncs032 (2012) (0.07) photon dosemeters: Calibration on a rod vs. a slab phantom: Rad. Prot. Dosim. 148 (2012) Extensions to the Beta Secondary Standard BSS 2: J. Instrum. 6, P11007 (2011) and Erratum and Addendum 31

32 Rolf Behrens Physikalisch-Technische Bundesanstalt