The Use of Effective Dose as a Radiological Protection Quantity

Main points / page 8 / first bullet / lines 185-187.

content

It’s incorrect to state that the dosimetric quantities have special names.

The units of these quantities have special names.

274

editorial

In considering doses to..

This sentence probably deserves a bullet of its own. Separate point made here

Section (26) / lines 730-736

content

In general the effect of genetic differences might be unknown. In specific cases these effects are known. For example in breast cancer.

Please describe how to incorporate this knowledge in specific cases for the justification and optimization of medical procedures.

930

editorial

..poviding advantage of providing continuity..

Not changing something for providing continuity with earlier work does not seem the best argument.  A more intellectual / contentual argument against the Thomas and Edwards (line 920) critique?

1084 + 1119 + 1309

content

Equivalent doses of 500 mSv .. 70 micron

In daily practice it is often difficult to relate the yearly 500 mSv equivalent dose limit to hands of workers (e.g. interventional radiologists) to the stochastic effect/chance of inducing skin cancer. Opportune to add information/ current state of affairs into this ICRP report?  

1309

content

Skin dose assessment to improve effective dose estimate seems to challenge the approach as suggested for patients. Different approaches for workers and patients may prove confusing.

In Line 1309 it is suggested to use additional  skin dose assessments based on measurements to provide a better estimate of effective dose. This seems to be contradicting with the remark in line 1660 through 1662 (true.. for medical exposures, but still)

estimates of organ or tissue dose should be used instead of effective dose.

1360

content

Whether effective dose relates to possibility of later tissue reactions will depend on type of radiation/exposure situation during accident.

Role for effective dose, alone,  in context of initial tissue reaction triage? Please clarify, explain in text. Type of radiation and e.g air kerma  as an alternative to effective dose for initial characterizations in accident situations?

Section (94) / line 1595.

content

The recorded quantities do not describe the radiation dose received by patients because these are patient (size) dependent.

Replace by: “The emitted dose delivered by the machine in diagnostic …”

Section (95) / lines 1614-1616

content

It is true that the effective dose is used to aid in justification of medical procedures but in the end it is the associated risk that counts.

Please acknowledge the importance of the associated possible risk when justifying a medical procedure.

Section (96) / lines 1627-1629.

content

It might be true that the approach ignores the uncertainties in associated risks, this does not make the approach incorrect or less correct than the effective dose approach. The effective dose (instead of risk) approach has to deal with the same uncertainties and ignores them as well.

Instead of abandoning the effective risk approach, embrace it and incorporate the known uncertainties.

Section (96) / line 1632

content

Where is the evidence presented exactly?

Add a reference.

Section (96) / line 1636

content

When is a difference ‘not large’?

Put the differences in risk estimates into perspective. How are these estimates used and do these need to be accurate?

Section (97) / line 1640

content

One cannot justify a medical procedure without translating the effective dose into a risk. One can optimize a procedure without the translation to risk.

Acknowledge the need to associate a possible risk with a certain effective dose when justifying a medical procedure.

Section (98) / line 1660-1662

content

In general, every medical procedure is limited to one anatomic area. It is stated that organ or tissue dose should be used instead of effective dose.

This statement is not worked out in much detail and raises the following questions: when should organ dose values be used instead of effective dose (justification, optimization or …); why should organ dose values be used? And how should these be used? Please clarify the rationale of this paragraph.

1686

editorial

…are included in many guidelines for…

Please provide references

Section (101)

content

When using effective dose in children, one must take to effects into account: 1) the change of dose distribution in the body for a given exposure level; 2) the change in risk due to higher radiation sensitivity and/or longer life time. It is often not clear whether both effects have been taken into account.

Please address both effects.

Section (107) / lines 1751 – 1752

And Section (108) / lines 1767 - 1771

content

This means that the quantity of importance is effective risk instead of effective dose.

Please acknowledge the usefulness of effective risk.

Section (109) / lines 1773 - 1777

content

It is not correct to suggest the recording of the patients accumulated dose because the number of patients who receive repeated imaging procedures has risen.

One can suggest considering the information (not the dose) obtained from previously performed procedures when requesting a new procedure.

Section (109) / lines 1777 - 1780

content

One might think that these recorded quantities are of use when justifying a new procedure. This is incorrect: the possible risk of the new procedure does not depend on the dose of previously performed procedures.

It should be noted that for the justification of a new procedure, knowledge on the accumulated radiation exposure is of no use.

1842

editorial

Risk of what exactly? The actual risk communicated through effective dose is unclear in the present text. Risk of cancer vs risk of dying of cancer (cf. table 2.1 line 620)?

Relevant because ICRP report 62 does clarify that point, but presents slightly different numbers. ICRP62 is used by Ethical committees: risk of cancer (concept) should preferentially be the same in the current report.

What risk is actually communicated through effective dose – in the way the present report is doing. Risk of cancer or additional  risk of dying of cancer. Please clarify throughout chapter 5.

ICRP report 62 (p.11 and Table 2) reports ” … be noted that the

risk is the total detriment from the exposure; namely the sum of the probability of fatal cancers, the weighted probability of non-fatal cancers and the probability over all succeeding

generations of serious hereditary disease resulting from the dose.”

ICRP62 is used by Ethical committees: risk of cancer should preferentially be the same in the current report.

Differences in risk numbers between the current report and report 62 should be clarified.

Section (117) / line 1880

content

This statement is valid for a particular age and sex. It seems that this is ignored in Section (96), line 1634.

Please rephrase.

Section (118) / line 1890-1893.

content

Here the uncertainties in associated risk are used to prefer effective dose over effective risk. However, on many places in this report (including sections 107 and 108), one suggests using age and sex specific risks.

Please make clearer when to use effective risk instead of effective dose.

2081-2089

editorial

Related to previous point: Relative risks per age-group are different in this report as compared to ICRP 62, this warrants clarification as ICRP 62 is still actively used in ethical review processes.

ICRP report 62 states: “For investigations involving

children the detriment per unit dose is 2 to 3 times larger than for adults; for people aged 50 years or over when exposed to the radiation sources it is only about l/5th to l/l0th of that for younger adults. Clearly if those to be  exposed are suffering from serious, possibly terminal disease then the likely expressed radiation-induced risk will be even lower.”

This report: “With this important caveat, it can be concluded that when considering most x-ray examinations, lifetime risk of cancer incidence per Sv may be around twice as great for the 0-9 years age at exposure group than for the 30-39 years group. For patients in their 60s, the lifetime risks from most examinations are estimated to be about half those for patients in their 30s, falling to less than one-third for patients in their 70s and about one-tenth for those in their 80s. Used appropriately, such information is of value in helping clinicians understand the possible risks associated with examinations and assist in communication with patients. In considering doses to patients having diseases with poor prognoses, life-expectancy will be a consideration in evaluating radiation risks.