SSM supports the draft ”The Use of Effective Dose as a Radiological Protection Quantity” in general. However, the document would benefit from taking the general and specific comments given below into account.
The title should reflect also the use of equivalent dose and absorbed dose as it is an important part of the document, e.g. “The use of effective dose, equivalent dose and absorbed dose as radiological protection quantities”.
SSM supports the proposal to use of absorbed dose instead of equivalent dose in limits to prevent tissue reactions.
Consider to include a short summary after each main section (2,3 …) with the main message.
In section 3 (dosimetry) there is a subsection on skin dose. To be complete consider to also add a sub-section on dose to lens of the eye. A discussion on the need for dosimetry of hand and feet is maybe also necessary.
In several sections in the report, the effective dose is discussed as a suitable quantity for optimisation, justification and comparison between modalities and techniques in medical applications, including situations with partial body irradiations. Examples are
Line 1609 ”Effective dose can be used to make such comparisons (indication of the associated relative health detriments from alternative techniques that result in different distributions of dose within the body) between doses from medical procedures that expose different regions of the body.”
Section 5.1 that discusses the use of effective dose in medical procedures based on operational quantities, i.e. based on the assumption of whole-body exposures. Table 5.1 gives values on effective dose for a number of examinations of which many do not cover the whole body (disregarding the scattered radiation component).
Line 1696 “Patient imaging procedures typically involve partial body radiation exposures… Since dose distributions from machine-produced x-ray and nuclear medicine procedures are very different, the effective dose is suitable for use in straightforward comparisons of doses from different techniques.”
There are also sections in the report where it is pointed out that the effective dose is not a suitable quantity for certain medical applications. For example in line 1660 (paragraph 98) it is noted that when imaging is limited to one anatomic area, estimates of organ/tissue doses should be used instead. This is also in line with the statement in ICRP report 103 section 7.3 paragraph (341) “The assessment and interpretation of effective dose from medical exposure of patients is problematic when organs and tissues receive only partial exposure or a very heterogeneous exposure, which is the case especially with diagnostic and interventional procedures.”
There seems therefore to be some possible contradictions that might lead to confusion about if effective dose can or cannot be used in partial body examinations. And further, since the effective dose is defined for specific whole-body irradiation geometries, it is not obvious how specific organ doses should be calculated, in cases with partial body irradiations. A guidance on how effective dose should be calculated in partial body irradiations would be of great importance for comparisons of techniques using effective dose for optimisation purposes. In order to be able to perform such comparisons, the methodology on how the effective dose (for the whole body) should be calculated/determined as only parts of the body is exposed, should be unambiguous. Elsewise, situations might occur where the effective dose for different techniques differs due to how the quantity is calculated, rather than due to the different techniques themselves.
The reader would gain from a clarification regarding these points, i.e. when effective dose can be used in partial body irradiations, and how the doses to organs not directly exposed should be taken into account when it is used. There is discussion about this issue starting on line 1728, to which perhaps reference also could be made. However, this discussion does not really give the needed guidance on when the effective dose can be used and not.
Line 195: Suggest to rephrase as "exposure and can be seen as an intermediate …".
Line 224: The use of E up to 1 Sv is said to be reasonable but that the possibility of occurrence of tissue reactions should also be considered at such doses if a significant contribution is made by “non-uniform distribution of external dose or radionuclides concentrated in specific tissues/organs”. It is not obvious why only non-uniform distributions and radionuclide concentrations in specific tissues/organs should be considered. At such dose levels (1 Sv) also exposure in uniform fields would likely increase the probability for certain tissue reactions. A suggestion is to end the sentence after “…the possibility of occurrence of tissue reactions should also be considered at such doses.”.
Lines 281-285: The use of collective effective dose could be expressed even further in this section (as it is in section 3.8): In addition to be a tool in optimization of protection it is also used to provide for comparison of doses from sources of radiation.
Lines 321-323: This sentence, that E does not provide estimates of dose to specific individuals, is important for understanding the concept of E, and should also be made a bullet among the main points, for example a new bullet at line 216.
Line 357: Compare with line 431. Use, if possible, a uniform way of expression.
Lines 454-461: Paragraph 11 contains a discussion on equivalent dose and absorbed dose. The recommendation to use absorbed dose could however be clearer.
Line 461: For clarity, “compared to low LET radiation” could be included at the end of the sentence that ends at line 461.
Line 657: Occasionally questions are raised about how the equivalent dose to the lens of the eye is /is not taken into account in the calculation of the effective dose. Perhaps a clarification that it is not, would be valuable.
Line 671: A minor editorial point for clarification. The meaning of the sentence “Risks for the working age population are somewhat smaller because risks are generally greater at younger ages.” would perhaps be clearer if formulated “Risks for the whole population are somewhat higher than for the working age population because risks are generally greater at younger ages.”
Lines 686 - 689: Definitions of the terms LAR and REIC should be included.
Line 771: It is not obvious why Ra-224 is particularly pointed out as an alpha emitter to be included in the sentence. Perhaps a clarification could be included, or the specific reference to Ra-224 omitted.
Line 830: A ”u” is missing in ”fundamental”.
Line 973: Also local external irradiation, not only local internal irradiation, can give high local absorbed doses. Suggested change “However, if there was a significant contribution to the effective dose from local external irradiation, radionuclides concentrated in particular organs…”
Line 1083: Paragraph 54. When using “The first concern..” one expect a second concern, which is handled in para 56. Consider to instead use “The main concern…”.
Line 1084: Should be "Section 2.2", not "Section 2.1"
Lines 1113-1115: Paragraph 55. Consider to explain the use of average over 1 cm2. Paragraph 54 contains information on the use of different depths but not area.
Lines 1127-1213: Section 3.7. The change in the protection quantities from equivalent dose [Sv] to mean absorbed dose in organs [Gy] is supported. An explanation, however, of how this will affect to operational quantities Hp(0,07) and Hp(0,3) would be appreciatied. Hp(0,3) and Hp(0,07) are today reported in Sievert and may easily be compared with dose limits of the protection quantities, which today also are given in Sievert. There is no discussion about if and how the operational quantities for organs need to be changed in order to report in Gray. Furthermore, if the operational quantities for organs will continue to be reported in Sievert, how will they be used when protection quantities are given in Gray? A short discussion/clarification about this would be useful for the readers.
Line 1199: Unclear what reference values are considered.
Line 1214: Section 3.8 on collective dose. The use of the terms “collective dose” and “collective effective dose” is mixed in the document. Either use the same expression or explain that these have the same meaning.
Line 1305: Replace "above" with "on" (if the "above dosimeter" is not meant to be worn on the neck).
Lines 1425 -1426, 1447: Suggest to rephrase as “Measurements of doses to people and environment…”.
Lines 1553 – 1555: The statement that collective dose could be used to help in selecting from various protection options following a severe nuclear accident or when planning for such events should be supported by references to publications that this indeed has been proven a useful tool. Otherwise, it should be removed.
Line 1677: Deterministic effects (thus absorbed dose values for single organs) are factors to consider in certain applications. For example risk of cognitive impairment resulting from brain CT-scanning of young children, sedated using certain anaesthetic pharmaceuticals.
Lines 1743 – 1752: See comment referring to row 1677.
Lines 1772 – 1780: It should be emphasized in the text that recorded accumulated patient exposure must not influence the justification of further exposures (except in cases where repeated interventional exposures risk inducing acute skin reactions).
Lines 1790 -1936: Section 5.4: A statement on the use of effective dose in risk communication following e.g. a severe nuclear accident should be included. The section discusses the use of effective dose for medical exposures in risk communication. However, the use of effective dose in other situations should be clarified.
Lines 1794 – 1810: See comment referring to row 1677.
Lines 1850- 1936: Section: Age- and sex-specific cancer risks and effective dose in 5.4. In this section ICRP gives a confusing impression. In one hand it is stated in several places, for example lines 1882 and 1935, that there are substantial uncertainties with the risk estimates. On the other hand, lines 1892, these figures can be used for information to clinicians and patients. We do not think table 5.3 and 5.4 gives relevant information in this specific ICRP publication of the use of effective dose. The uncertainties are too big and the figures will likely be used by clinicians and patients for an individual estimate of risk for different X-ray procedures. Also the summary chapter 6, line 2085, indicates that these tables can be used. The tables 2.4, 2.5 and 5.2 sums up the different risks and the age- and sex risk dependence. We would like that it both in Section: Age- and sex-specific cancer risks and effective dose, line 1850- 1936 and Summary chapter 6 lines 2076-2089, is more clearly stated that table 5.3 and 5.4 can not be used for individual risk estimates. The alternative is to remove tables 5.3 and 5.4 and the text referring to them.
Line 2097 and line 2105: The term used on line 2097 is “Collective effective dose” whereas the term used on line 2105 is “Collective dose”.