Radiological protection in paediatric diagnostic and interventional radiology

Line

Paragraph

Comment

29-44

1, 2 & 3

These three paragraphs are very generic and relate mainly to studies on adults. As the publication is aimed at paediatrics they should either be deleted or made more specific to paediatrics eg include figures for % increase in paediatric examinations if known.

55

6

It is not clear that the dose quoted relates to paediatric CT. Suggest inserting the word “paediatric” between “from” and “CT”.

59-61

7

Suggest change paragraph to make it more specific for paediatrics to “It is particularly important for paediatric patients that all radiological examinations are justified and optimised with regard to radiological protection”.

63 & 66

8

Suggest change the use of the word “children” to “paediatric patients” so that it includes neonates or alternatively make sure that it is explained that the term children includes infants and neonates. The following is a general comment not specific to this paragraph. There is no definition of “children” or “paediatric” in the document, it is inferred in various places but should perhaps be explicitly defined in the introduction.

14

Care needs to be taken with using effective dose, even when comparing procedures for similar sets of paediatric patients, as the relative tissue weighting factors for children may be very different to those for adults, which may lead to incorrect conclusions regarding dose differences between different radiographic projections, particularly opposing lateral views.

18

The meaning of the last sentence is unclear. It seems to suggest medical doses are high enough that the ‘flattened’ part of the LNT curve is reached, which is obviously not the case. If referring to the possibility of deterministic effects occurring during high dose medical procedures, this should be reworded appropriately

273

21

The term “radiologist” is too specific as there are other healthcare professionals who justify medical exposures both generically and for individuals. Suggest change to “radiologist or authorised imaging healthcare practitioner” or similar.

274

21

The word “that” is missing at the beginning of the bullet point (alternatively “that” could be inserted at the end of line 273 and removed from the star of lines 276 and 279).

281

22

As in comments on paragraph 7 this should be changed to be more specific for paediatric patients. Suggest deleting “for all patients, and particularly” from the sentence.

283

22

See comment on line 273 above, suggest replace radiologist with the more generic term included in that comment.

302

25

See comments above about use of the term “radiologist”

318

26

See comments under paragraph 8 above relating to use of the term “children”.

326-332

27

This paragraph should not be in the document as it does not relate to paediatric exposures. The embryo/fetus is not a paediatric patient (unless your definition, which there does not seem to be one in the document includes it). If you want to include something of this nature that it should be in a footnote not the main text.

328

27

Notwithstanding the above comment it is over prescriptive to state “one should conduct a pregnancy test prior to a procedure that involves higher exposure of the pelvic region through a primary beam such as interventional fluoroscopic examinations”. Other methods may be used to exclude pregnancy. It would be better to say “appropaiate mechanisms are to be used to exclude pregnancy where relevant”

334-339

28

This is over prescriptive as there are other alternatives for ensuring appropriate justification of research exposures for paediatric patients. A more generic paragraph is suggested such as “Institutions are to ensure that there are suitable mechanisms in place eg through the research and development procedures to enable biomedical research exposures to be individually justified.”

30

The wording could perhaps be re-considered to ensure there is no implication that these are the only examinations that are not justified in children.

36 & 37

Greater emphasis could perhaps be made here of the need to involve a qualified medical physicist in equipment QA, and establishment of suitable protocols.

401

37

Suggest replace “hospital” with “institution”

402

37

“IPEM2004” is the wrong reference. It should be “IPEM2005” The full reference is “Institute of Physics and Engineering in Medicine, Recommended Standards for the Routine Performance Testing of Diagnostic X-ray Imaging Systems, IPEM Report 91(Fairmount House, York)”

407

37

“every year” is too prescriptive, the recommended frequency for tests in IPEM2005 varies depending on the equipment and type of test. Suggest change to “appropriate intervals (IPEM2005)”.

523

-

IPEM2005 needs to be added to the references.

568

47

Suggest that an extra sentence is added at the beginning of the paragraph. “In some cases it may be necessary for parents, carers or staff to use physical restraint to immobilise the patient.”

568

47

Suggest rephrase the first sentence to “Only in exceptional circumstances should the patient be held by the radiological staff.”

583

48

The word “a” or “the” is missing between “making” and “child”.

616

51

Suggest “to be” should be inserted between “likely” and “ineffective”.

55

Where possible, CT topograms/scout views should also be performed in PA rather than AP mode.

662

56

Suggest insert “at” between “kept” and “more”

It should be noted that other work has demonstrated that shielding of the thyroid, as well as thorax, during skull CT has demonstrated significant reduction in thyroid dose.

C-L Chapple, Willis J & Shemilt A.  Dose reduction in paediatric head computed tomography examinations. Abstract: Proceedings of the Seventh SRP International Symposium 2005; 187-192

G Groat, W Huda, R Lavalee & K Ogden. Do lead aprons reduce Patient CT doses? Med Phys 33, no 6; 2006.

62

It would be useful to see a reference for work indicating that it is beneficial to use a grid for infant fluoroscopy.

731

64

The words “should patients “ needs to be changed to “patients should”.

933

90

Suggest inserting after “area” before closing brackets “also referred to as Dose Area Product or DAP”.

Reference could also be made to HPA UK publications.

D Hart, MC Hillier & BF Wall, 2007. Doses to patients from radiographic & fluoroscopic X-ray imaging procedures in the UK – 2005 review.

990

91

Suggest replace the term “radioprotective”  with “radiation protection”

994

92

To make it clear that the additional training suggested relates to paediatric imaging I suggest adding “for paediatric imaging” after “protection”

995

92

Suggest adding “general” before “radiology” to fit in with the suggested amendment to line 995.

1003

93

Suggest change “infant” to “child”.

1086

98

Suggest adding a new sentence after “oblique positions.” “Where practicable arm supports should be used to prevent the arm drifting towards the primary beam during long procedures.”

1108-1119

-

It would be easier for users if Table 4 was moved to below the paragraph that it refers to ie line 1018. The usefulness of this table, which refers only to adult exposure, is debatable.

1182

102

There is a full stop missing between “treatment” and “Justification”

1211

Section 6.3

Measurements of CT dose. This whole section could be simplified within the main text and only refer in generic terms to factors that affect dose with the mathematics and derivations of dose quantities moved to an Annex. There is no equivalent in depth section on measurements of dose for radiography and fluoroscopy in the main text.

If retaining detail, it is important to clarify earlier that CTDI is only equivalent to average dose at the centre of a scan volume equivalent in size and attenuating properties to the phantom used in its measurement. For children, the 16cm (adult head) phantom is likely to give more appropriate CTDI values, but even these values will differ substantially from average dose values to actual paediatric patients.

111

Much recent evidence indicates that patient doses tend to be higher with multidetector CT, although this may often be due to choice of protocol rather than intrinsic CTDI values per 100 mAs. However, detector geometry may often mean that for any particular scanner there will be certain acquisition slice width settings that lead to higher CTDI values than others, due to reduced z-axis efficiency. These slice width settings should be avoided for paediatric CT.

The effect of over-ranging (additional rotations at each end of a helical volume) may also be particularly significant for small paediatric patients, as this may result in irradiation of radiosensitive organs outside the area of interest.

113

No mention has been made of DLP (dose length product) which does take the scan length into consideration.

114

Automated tube current modulation must be used with care as, depending on the way it is set up, it can sometimes result in an increase in dose to paediatric patients. It is important to understand how your particular system works, and that an appropriate image quality or other scaling parameter is defined for the examination.

1355

119

The sentence “Keeping the noise level constant requires an increase in mAs, and in consequence in radiation exposure, that is inversely proportional to the square of the slice thickness and, in thus radiation exposure, i.e., a reduction of the thickness to one half requires an increase of the exposure-time product, mAs, by a factor of 4.” The phrase “and, in thus radiation exposure,”. Should be deleted.

120

The first reference given here (Chapple et al) relates to a method for determining effective dose from DLP for any size patient, rather than the efficacy of breast shielding. The reference given for paragraph 56 above relates to the use of shielding for dose reduction.