|The following comments regarding the Draft Recommendations of the International Commission on Radiation Protection (02/276/06 - 5 June 2006) were developed by the Medical Internal Radiation Dose (MIRD) Committee of the Society of Nuclear Medicine (SNM)—an international scientific and professional organization of over 16,000 members dedicated to promoting the science, technology, and practical applications of molecular imaging and therapy.
MIRD Committee Specific Recommendations:
1. Give consideration to eventually establishing age and gender-specific weighting factors. Initial consideration should be given to: (1) adult males, (2) adult females, (3) pediatric males, and (4) pediatric females.
There is currently a preponderance of evidence that radiation tissue risks differ between males and females, and as the ICRP has acknowledged in their recommended dose limits, there are even greater differences in radiation risk between adults and children. Age and gender dependent weighting factors (wT) are, therefore, suggested.
Although this would result in an effective dose that is no longer a universal quantity, there is substantial evidence that when the pertinent data are available, radiation risks should be more age and gender-specific.
The ICRP's planned issuance of gender-specific voxel phantoms, and later gender- and age-dependent phantoms will provide an extensive source of gender and age-specific dosimetric data. As these data become available, the ICRP should give serious consideration to adopting weighting factors that are age and gender specific.
Paragraph 22 – Provide a rationale in this paragraph for why retrospective evaluation of radiation-related risks should be gender-specific but not when the purpose is radiological protection.
2. Better amplify in the document that effective dose is not an appropriate quantity for the regulation of medical radiation exposure.
In paragraphs 93, 98, 101, and 112 add text that says that estimation of effective dose for therapy with radiopharmaceuticals is inappropriate. Although this is the case for all radiopharmaceuticals, it is particularly important to make this distinction clear in the case of alpha-emitting radiopharmaceuticals. Application of the tissue and radiation weighting factors could cause more harm than good in this case by inappropriately limiting the use of radiation for therapy. This is because the radiation weighting factor for protection is 20 while the RBE is between 3 and 5.
In paragraph 108 – Mention targeted alpha-particle emitters and highlight that recommendations given here are not appropriate for use in targeted alpha-particle emitter therapy.
Paragraph 132 – Note that such internal exposures are distinct from the application of internally administered radiopharmaceuticals for patient diagnosis and therapy.
Paragraph 143 – Add medical applications of radiation and internally administered radiopharmaceuticals for diagnosis and therapy.
Paragraph 144 – Add examples such as external radiotherapy and targeted radionuclide therapy using beta, auger and alpha-particle emitters.
Paragraph 168 – Indicate where this separate treatment is described and highlight its inappropriateness by adding the specific wording "medical applications of radiation and internally administered radiopharmaceuticals for diagnosis and therapy."
Paragraph 215 – Identify the “corresponding foundation document.”
Table 4 – Include a note to the table indicating that medical uses of radiation are not included because use of effective dose is inappropriate in such circumstances.
Paragraph 239 – Add "with the exception of internally administered radiopharmaceuticals for diagnosis and therapy"
3. Sections pertaining to the use of radiation in medical procedures do not recognize recent advances in this area.
Paragraph 245 – For the language "radiotherapy aims to destroy…" rephrase "external beam radiotherapy and targeted radionuclide therapy aim to destroy…"
Paragraph 247 – Add PET/CT to diagnose and monitor response to therapy to the chest X-ray example
Paragraph 248 – Extend the last sentence to end with "or ensuring that the radionuclide dosimetry and pharmacokinetics of the radiopharmaceutical provide a dose distribution to an individual patient or well-defined patient population that will do more good than harm."
Paragraph 258 – Add "in targeted radionuclide therapy, the dose distribution to an individual patient or well-defined patient population should maximize the tumor to normal organ absorbed dose ratio so as to do more good than harm."
4. Sections pertaining to medical use that require clarification or that may lead to confusion.
Paragraph 243 – "Informed consent" is a term with a specific meaning in the medical field, wherein it refers to a patient's agreement to participate in an experimental trial. Replace with the phrase "understanding of the harm vs good in (accepting the) procedure." In the same paragraph, it is not clear what is meant by: "The degree of informed consent varies based on the exposure level and the possible emergent medical circumstances." This sentence should be rephrased.
Paragraph 251 – Add underlined text "… and consequently somewhat less attention has been given to optimization of protection in medical exposure of patients by the Commission than in other applications of radiation sources. In this regard, depending upon the specific nature of medical use, medical exposure protection can be considered to fall under the guidelines of professional medical bodies. Such delegation of authority is outlined in Sections 6.2.1 and 11.1.3.
Paragraph 254 – The meaning of this paragraph is not clear, in particular: "In practice, this is unrealistically difficult and it is simpler to choose the initial values as a percentile point on the observed distribution of doses to patients." This sentence becomes clear only after reading paragraph 255. The two should be somehow incorporated together.
5. Regarding the role of non-expert stakeholders
The recognition that non-expert stakeholders should be involved in the implementation of recommendations regarding radiological protection is important but must be accompanied by a concerted effort, expressed in the ICRP recommendations by the inclusion of text and illustrative examples, that given limited societal resources, the additional costs involved in coping with more stringent requirements means that other beneficial uses of societal resources will be curtailed. A thoughtful balance needs to be made. It is important that stakeholders and the public understand that the decreased theoretical risk from diminished radiation dose may be offset by the increased risk from new unmet needs that arise as an unintended consequence.