Radiological protection in medicine

Draft document: Radiological protection in medicine
Submitted by Cindy Flannery, U.S. Nuclear Regulatory Commission
Commenting on behalf of the organisation

The U.S. Nuclear Regulatory Commission (NRC) staff would like to thank the International Commission on Radiological Protection (ICRP) for the opportunity to provide comments on the ICRP Draft Report on Radiological Protection in Medicine. The opportunity to submit and review other stakeholder comments on Commission documents is greatly appreciated. General Comments: 1. The effects of in utero irradiation are discussed in several sections of the draft publication. The Commission should consider discussing those situations whereby the fetus should be treated as a member of the public and radiation exposures limited to 1 mSv or less. In addition, the Commission introduces the topic of termination of pregnancy (page 41, line 31 to page 42, line 5). The amount of information presented is insufficient. The Commission addresses this issue more thoroughly in the draft 2007 Recommendations. Either more information (possibly in the form of a matrix illustrating radiation exposure and associated health effect as a function of fetal age) should be provided so the competent medical provider can assist the patient in making an informed decision or this section should be deleted. 2. While physicians may agree that a dose error in a cancer treatment regimen could lead to inadequate treatment of cancer (underdosing) or to an increased likelihood of complications (overdosing), many physicians may consider the use of 10 percent for a variance threshold to be too low, since such differences are within the range of standard-of-care variations from one practitioner to another (page 16, lines 21 through 22). The Commission should consider a higher variance threshold (e.g., 20 percent). Specific Comments: 1. Page 4: The publication dates for many of the ICRP documents are incorrect. The title of Publication 98 is incorrect. 2. Page 8, line 19: The publication date for the ICRP document is incorrect. 3. Page 9, line 2-3, sentence 1: Replace with the following – “At radiation doses below 100 mSv the increase in incidence of stochastic effects (cancer and/or heritable disease) is assumed by the Commission to occur in a small probability, but radiation exposure will increase the risk of excess stochastic effects in a simple, proportionate manner. The probability of such effects is increased when ionizing radiation is used in medical procedures.” 4. Page 9, lines 7-9: Delete last two sentences. 5. Page 9, lines 23-24: revise to read – “All these circumstances indicate that proper justification and optimization of radiation use in medicine are indispensable principles of radiological protection.” 6. Page 9, line 27: The publication date for the ICRP document is incorrect. 7. Page 9, line 30: change 10 mGy to 100 mGy. The statistical power of epidemiology studies generally is too weak to detect statistically significant changes in cancer mortality or morbidity with exposures less than 100 mGy. 8. Page 12, line 7: Change “radiation weighting factors are between 5 and 20,…” to “radiation weighting factors are between 2 and 21,…” The draft 2007 ICRP recommendations change the weighting factors for neutrons. The current numbers reflect those contained in the 1990 recommendations. This change would be consistent with the text in the following paragraph (lines 12-20) where the new ICRP tissue weighting factors are cited. 9. Page 12, line 20: The publication number and the correct date should be provided for the referenced ICRP document. 10. Page 13, line 14: Change “deliberate” to “planned”. This would be consistent with the new ICRP recommendations. 11. Page 13, lines 14-15, sentence 2: The term “therapy” is used twice in the sentence. The second use of the term “therapy” in this sentence should be replaced with an explanation of the purpose of therapy, such as “killing cells” or “tissue eradication.” 12. Page 13, line 18: Replace “prejudicing” with “jeopardizing” 13. Page 13, line 29: Revise to read – “interventional procedures or diagnostic procedures using radiopharmaceuticals (especially those prescribed to pregnant or potentially pregnant patients), and a high level (typically written) consent is often obtained” 14. Page 14, lines 9-11: A better example of a screening procedure of asymptomatic patients would be annual dental x-rays to detect asymptomatic carries. The radiation doses are very small, yet the clinical benefit of this screening procedure is without controversy. During these screening procedures, radiation exposure to the patient is minimized by using lead aprons and thyroid shields (optimization). 15. Page 14, line 23: Revise to read – “deterministic damage (tissue reactions) and non-cancer disease (e.g., stroke, cardiovascular disease) to surrounding and underlying tissue and some risk of stochastic” There is increasing evidence of non-cancer diseases being attributable to radiation therapy, particularly cardiovascular disease. 16. Page 14, line 30: Insert after “manage” the phrase “(optimized)” 17. Page 15, line 13: Revise “examination” to be plural 18. Page 15, line 14: To provide clarity, revise to read – “higher risk per unit dose may be offset by the reduction in dose relative to the dose received by an adult.” 19. Page 16, lines 20-21: Replace “overdosage” and “Underdosage” with “overdosing” and “Underdosing,” respectively. The term “dosage” is usually used in reference to radiopharmaceuticals administered to patients (e.g., a dosage of a given activity of I-131) 20. Page 16, lines 20-21: Revise last sentence of paragraph to read – “Overdosing has a significant potential to result in severe or fatal consequences.” It may be overstated to state that overdosing “usually” results in “an unacceptably high risk of severe or fatal complications” since overdosing often times does not result in patient harm. 21. Page 16, lines 21-22: Revise last sentence of paragraph to read – “Underdosing may result in not curing the cancer and may cause more than expected deaths from cancer.” 22. Page 16, lines 28-29: Revise last sentence of paragraph to read – “As noted before, medical radiation sources are deliberately used to irradiate patients and they are utilized in a controlled manner.” 23. Page 17, line 23: Revise to read – “from all planned exposure situations other than medical exposure of patients should not exceed the appropriate limits specified by” This is consistent with the new draft ICRP recommendations. 24. Page 17, line 27: Insert after medical purpose “(i.e., optimized)” 25. Page 18, line 1: Remove the second use of the word “of” 26. Page 18, line 28: The term non-professional comforter is used to specifically exclude nurses, physicians, and medical technicians from consideration in this section. With this in mind, how is a member of the clergy classified? They are professional comforters. Rather than non-professional, maybe the term “non-medical” should be used instead. 27. Page 21, lines 20-22: Revise last sentence of paragraph to read – “Unlike ultrasound, the CT results are less dependent on the CT operator, much easier to interpret, and yield more accurate diagnostic information.” 28. Page 23, line 6: Replace “Committee 3” with “The Commission” 29. Page 23, line 20: Insert after “group” the phrase “of individuals” 30. Page 24, lines 3-5: Revise to read – “The justification of the radiological procedure is a matter of national and international professional bodies, in conjunction with national health and radiological protection regulatory authorities and the corresponding international organizations.” This is consistent with the new ICRP recommendations. 31. Page 25, line 6: The phrase “Beyond checking that the required information is not readily available” is unclear and should be reworded. Remove the word “not” for clarity. 32. Page 25, line 18: A statement should be included to discuss what the Commission considers to be unjustified radiological procedures. For example, should radiological procedures be used to deter theft or detect drugs for law enforcement purposes? In the first instance, diamond miners may require daily x-ray screening of miners to deter the thief of diamonds. The only benefit is received by the employer. In the later case, abdominal exposures of 10 to 100 mSv may be delivered if CT is prescribed to detect packets of drugs that may have been swallowed by couriers. The IAEA in its Basic Safety Standards (Annex II) addresses this topic. 33. Page 28, lines 7-9: End the sentence at the end of line 7 and delete lines 8 and 9. 34. Page 28, line 14: The phrase “medical intervention” should be reworded. This same phrase is used in section 17.2 to describe medical interventionists and interventional procedures (e.g., fluoroscopic procedures). 35. Page 30, line 9: A fourth area to be included is the radiopharmaceutical staff of a nuclear medicine department. The monthly exposures to these staff are often around 0.5 mSv. These exposures become significant for the female staff especially if they declare a pregnancy. 36. Page 30, line 30: Revise to read – “Public access to hospitals and to radiology rooms is restricted, but public access is more open” 37. Page 31, line 27: The document should specify the status of the fetus and whether dose limits to members of the public apply. 38. Page 38, line 31: Add to the end of the sentence – “and professional caregivers and comforters (e.g., nurses, orderlies, chaplains) providing care and assistance to patients.” 39. Page 39, lines 26 and 31: Change “Committee 3” to “The Commission” 40. Page 41, line 5: Change “Have” to “have” 41. Page 41, line 23: To provide clarity, insert after “if a woman” the phrase “declares to her employer that she” 42. Page 41, lines 28-29: Last sentence, see comment #37 above. 43. Page 42, lines 23-27: Revise to read – “Acute radiation doses (to patients) may cause cataract at < 1 Gy, erythema at 2 Gy, permanent epilation at 7 Gy, and delayed skin necrosis at 12 Gy. Protracted (occupational) exposures to the eye may cause cataracts at 1 Gy.” The threshold of cataracts is likely lower than those presented here. Worgul et al, Radiation Research, vol 2, 2007 reviewed cataract formation among Chernobyl liquidators and estimates a threshold around 0.34 Gy. Minamoto et al, Int. J. Radiation Biology, 80 (5), 339-45 (2004) observed an increased lens opacities in the posterior subcapsular region of the eye that was attributed to radiation exposures less than 1 Sv. 44. Page 43, line 1: Revise to read – “guided interventional procedure, expected dose rates, a statement on the cumulative skin doses and skin sites” 45. Page 43, line 3: Replace “use” with “record” 46. Page 43, line 22: “Overdosage” and “under dosage” should be replaced with “Overdosing” and “underdosing,” respectively. The term “dosage” is usually used in reference to radiopharmaceuticals administered to patients. 47. Page 43, line 24: Revise to read – “Publication 86 is intended to assist…..” 48. Page 44, line 14-17: a. “over dosages have” “over dosage” and “Under dosage” should be replaced with “overdosing has” “overdosing” and “Underdosing” respectively. The term “dosage” is usually used in reference to radiopharmaceuticals administered to patients. b. many physicians may consider the use of 10 percent for a variance threshold to be too low, since such differences are within the range of standard-of-care variations from one practitioner to another. 49. Page 45, lines 9-10: Revise to read – “The absorbed doses to tissues from computed tomography can often approach or exceed 10 to 100 mGy.” There is limited epidemiological information concerning increased cancer following radiation exposures below 100 mSv. 50. Page 45, lines 17: Replace “patient management” with “management of patient dose” 51. Page 48, line8: The sentence describes to whom the dose limits are applicable. The dose limits for these two groups of individuals should also be provided (e.g., public dose limit of 1 mSv/year, occupational dose limit of 20 mSv/year). 52. Page 48, lines 26-27: Delete last sentence. Unless the Commission wishes to quantify “some time”, this issue is best not addressed. The Commission has already stated that therapy with unsealed radionuclides is contraindicated for pregnant and potentially pregnant patients. 53. Page 50, lines 1: “overdosage” should be replaced with “overdosing”. 54. Pages 52 and 53: The publication dates for many of the ICRP documents are incorrect. The title of Publication 98 is incorrect.