Practical Aspects in Optimisation of Radiological Protection in Digital Radiography, Fluoroscopy, and CT


Draft document: Practical Aspects in Optimisation of Radiological Protection in Digital Radiography, Fluoroscopy, and CT
Submitted by Helmut Schlattl, Federal Office for Radiation Protection, Germany
Commenting on behalf of the organisation

Name/Institution: Federal Office for Radiation Protection 

Country: Germany

 

Practical Aspects in Optimisation of Radiological Protection in Digital Radiography, Fluoroscopy, and CT

Date: 03/23/2023

 

 

 

 

 

 

 

No.

Page

Line/Table/Fig/Box

Type

Additional information on location

(as appropriate)

Comment or change proposed

1

8

Fig 1.1

Editorial

“The levels represent different stages in achievement moving upwards from D, through B, and C, towards A.”

Proposal for better order:

"upwards from D, through C, and B, towards A"

2

9

291

Editorial

“When new software is added to existing equipment, it is essential that adequate training be provided to end users.”

“[…] it is essential that adequate training is provided to end users.”

3

10

329

Editorial

“There are also approaches for interventional procedures in Section 3, which will be of prime interest to radiologists and other clinicians performing them, but of relevance to other groups.”

Perhaps better: “[…] clinicians performing them, but of relevance to other groups, too.”

4

11

353

Editorial

„The DL methods, are already yielding promising results in medical imaging related to many diagnostic tasks, such as lesion or tissue localisation, segmentation, classification and prediction of clinical outcomes and are being used in CT image reconstruction.“

The comma is obsolete:

“The DL methods are already yielding promising results […]”

5

11

368

Editorial

“This will require not only regulatory approval of algorithms and procedures, but measures in hospitals

to ensure the methods are appropriate for local patient cohorts.“

“[…] procedures, but also measures […]”

6

11

374

Editorial

“In the last two decades, ICRP has prepared publications focussing on the technical requirements for optimisation with regard to the various modalities using ionising radiology, namely radiography, fluoroscopy, and CT.”

“[…] modalities using ionising radiation, namely […]”

7

11

391

Editorial

“ICRP recently provided a detailed report on occupational radiological protection for interventional procedures (ICRP, 2018a) so this report will not deal with occupational exposure issues in any depth, but emphasises that

occupational protection should be managed in an integrated approach with patient protection.“

This sentence contains two phrases that need to be separated.

“[…] procedures (ICRP, 2018a); so this report […]”

8

12

408

Editorial

“(21) The specific needs and challenges in diagnostic and interventional procedures of paediatric patients, for whom the risks of radiation exposure are greater, were addressed in

ICRP (2013b).“

“(21) […] Publication 121 (ICRP, 2013b).”

9

12

423

Editorial

“The tools that accompany digital imaging from Radiology Information Systems (RIS), to Picture Archiving and Communication Systems (PACS), and Dose Management tools facilitate workflow, allowing easier storage and transfer of image data, image manipulation and merging, and recording of exposure details, are described in Annex B.“

“[…] Management tools facilitating workflow, […].”

10

13

463

Comment

“Radiographers, radiologists, and medical physicists should collaborate to identify the most appropriate processing algorithms for reporting radiographs.”

It is not clear what is meant by “appropriate processing algorithms for reporting radiographs” and how this is related to QC/QA.

11

14

481

Comment

“As a result, it is the noise level and image contrast that set the limit on image quality.”

Is the resolution not also affecting image quality?

12

14

494

Editorial

“Full DR systems offer more detailed preinstalled protocols including not only tube kV and mAs selection, but source image-receptor distance (SID), additional filtration, field of view (FOV), position of image receptor, use of radiographic grid, and post processing tools.”

Replace units with quantities:

“[…] not only tube potential and current-time product selection, […].”

Or alternatively: “[…] not only tube potential and mAs selection […].”

There are many further occurrences in the document, which have not all been listed separately here.

13

17

Table 2.1

Note

“Exposure factors and expected dose levels for a range of imaging tasks”

For information: All values for adults below the German DRLs. Upper values for children higher than German DRLs.

14

18

583

Editorial

“Grids are employed to absorb the scattered radiation to improve contrast (Box 2.2) and are used for the majority of adult radiography examinations of the trunk or head, but are not required when imaging thicknesses of soft tissue less than about 12 cm or low attenuation exams with low tube potentials (Table 2.1).

“[…] when imaging thicknesses of soft tissue of less than about 12 cm or at low attenuation exams with low tube potentials […]”

15

18

595

 

“(39) If a mixture of grid and non-grid exposures are carried out on the same unit, there should be a safety check before an image is taken to ensure that the unit is set up correctly.“

“grid” appears to have a different font and font size. Please check.

16

18

607

Comment

“Increasing tube potential without decreasing mAs will result in a higher dose to the patient, as output increases roughly as kV2.”

kV is a unit not a quantity. Better use "tube potential squared."

17

19

637

Editorial

“The variation in sensitivity of a digital detector with photon energy and so tube potential depends on the phosphor material.”

“[…] and thus tube potential depends on the phosphor material.”

18

19

638-639

Editorial

“While the sensitivity of CsI DR systems increase with tube potential, that for CR systems decline, so the relative exposure needs to be increased slightly at higher tube potentials (Doyle and Martin, 2006).“

“[…] systems increases with […] systems declines, so the […]”

19

20

656

Editorial

“(48) Considering quality levels required for different imaging tasks, high might correspond to an air kerma incident on the image receptor of 0.2–0.5 mGy, medium to 0.1–0.25 mGy, and low to 0.05 to 0.12 mGy.“

Are not these exposure levels rather than quality levels?

20

20

678

Editorial

“Images having higher or lower noise levels than is required are not readily recognizable at the time images are taken, so there a risk of dose creep and increases of 40% in dose have been reported (Gibson and Davidson, 2012).“

“[…], so there is a risk of dose creep […]”

21

21

710

Comment

“There have also been vendor specific definitions for EI, so users of older equipment should be aware that factors may be different.”

Elaborated in (56) and can thus be removed here.

22

21

717

Comment

“Analysing the percentage of images that fall outside an acceptable range can be used to educate technologists and decrease the variation while improving image quality goals of the department.”

“technologists” is not defined before.

23

22

731

Comment

“2.3.1. Source to image receptor distance (SID) and focal spot size”

It should be noted in this section that varying the SID should only be done in coordination with the medical physicist. Unexperienced radiographers might not be aware of all the consequences.

24

22

740

Editorial

“As a rule of thumb this involves increasing the exposure by 20% if the SID is lengthened by 10 cm and reducing it by 20% if the SID is shortened.”

It might be beneficial to be explicit here and state the length of shortening.

25

25

830

Comment

“However, consideration should be given to protection of the breast, gonads and thyroid where these organs lie within 5 cm of the primary beam (ICRP, 1982, 2013b) (Table 2.3).”

Could be worthwhile to add here “Since the risk to interfere with AEC gets higher with decreasing distance between FOV and shielding, particular care in the positioning of shielding and FOV is required.”

26

26

868

Editorial

“These actions which can increase or decrease patient dose, are based on Table 2.3 in ICRP (2004) but extended to include a wider range of actions.“

“[…] Table 2.3 in Publication 93 (ICRP, 2004) […]”

27

29

907

 

“Radiographers, radiologists, and medical physicists should work together to identify the most appropriate processing algorithms for reporting when a new radiography system is commissioned.”

See comment 10

28

35

1071

Editorial

“It requires appropriate selection of a complex set of technical parameters, tailored to the clinical task, and should start with the establishment of a core team of radiologist, radiographer, and medical radiation physicist properly trained in fluoroscopy.”

The word “radiation” could be removed: “[…] and medical physicist properly trained in fluoroscopy.”

29

37

1113

Editorial

“(95) Image receptors for both IIs and FPs are available in a range of sizes, varying from about 10–15 cm up to 40 cm depending on the intended clinical application.“

“[…] about 10-15 cm up to 40 cm diameter depending on […]”

30

39

1201

Editorial

“Each configuration comprises of a set of exposure

technique factors and image processing parameters, which are programmable and adjustable to …“

The word “of” between “comprises” and “a set” should be omitted.

“Each configuration comprises a set of exposure […]”

31

40

Box 3.3, Fig

Comment

 

Not possible to distinguish 'low dose' and 'high contrast'.

32

41

1240-1242

Editorial

“(114) Protocol configuration includes proper adjustment of settings customised to the required image quality and dose saving needs for the clinical task. Protocols should be configured to give the required image quality and dose saving needs for the clinical task.“

The meaning of these two consecutive phrases is approximately the same.

33

43

Box 3.4

Editorial

“Other quantities that can possibly be used are reference air kerma (Ka,r) (IEC, 2020) (also referred to as the cumulative air kerma (CAK) at the patient entrance reference point, fluoroscopy time and the number of radiographic images obtained as part of the procedure.”

Closing parenthesis missing:

“[…] (also referred to as the cumulative air kerma (CAK)) at the patient entrance reference point, […]”

34

43

Box 3.4

Editorial

“For further information on DRLs, see ICRP (2017).”

“For further information see Publication 135 (ICRP, 2017).”

35

44

1314

Editorial

“(126) PSD can be measured directly using different types of dosimeters or calculated from measure dose quantities.“

“[…] or calculated from measured dose quantities.”

36

44

1333

Editorial

“(128) Post-procedure dose notification should be provided to the operator in case any of the reported dose values reach the pre-defined trigger levels for patient follow and management of tissue reactions.“

“[…] patient follow up and […]”

37

46

Table 3.2

Editorial

“Reference air kerma (Ka,r)“

“a,r” in Ka,r should be subscript.

38

48

1436

Comment

“Staff needs to apply the basic radiation protection principles and make effective use of protective devices. Measures to protect staff should not impair the clinical outcome, and should not increase patient exposure.”

It could be added that in future, virtual reality may provide effective training of the medical staff for radiation protection in interventional radiology.

39

48

1443

Comment

“Geometric factors include positioning of the x-ray system in relation to the anatomical region, projection, table height, and focus-to-image receptor distance.”

The same conditions are to be considered during the commissioning of the system.

40

49

1458

Editorial

“The use of steep angulations increases patient dose, passing through thicker more lateral sections of the body, should be minimised when possible.“

“[…] angulations increasing patient […].”

Alternatively: “[…] of the body, and should be minimised when possible.”

41

49

1477

Editorial

“(146) The anti-scatter grid should be removed for procedures that result in low levels of scattered radiation, e.g., those involving small children or where body thicknesses is less than 10 cm.“

“[…] where body thickness is less than 10 cm.”

42

51

1529

Comment

“In addition, it is recommended that sites where interventional procedures are performed should establish a team that includes a physician, medical physicist and radiographers to review protocols in cases when the patient skin dose exceeds certain preselected levels.”

What about international error-culture in radiology? Official reports of medical cases where patient doses exceed preselected levels considerably can be collected in national databases, where they can be evaluated statistically (as it is done, e.g., at BfS in Germany)

43

53

Box 3.9 (B)

Editorial

“Requests for fluoroscopy procedures include reason for referral and with clinical history of patient, including pre-procedure diagnostic imaging and information on all previous FGI procedures available in the Electronic Medical Record (EMR).”

“and” superfluous:

“[…] reason for referral with clinical history of patient, […]”

44

56

1629-1630

Editorial

“(162) The next step is protocol optimisation, potential dose reduction, with CT depends on appropriate selection of scanning parameters (both acquisition and reconstruction).“

Phrase not properly structured; please check. Suggestion:

“[…] protocol optimisation; potential dose reduction with CT […]”

45

61

1815

Editorial

“For CT scanners in which the tube current is set manually, increasing the scan pitch could in principle reduce patient dose, if the tube current remained constant, but all modern CT scanners have an ATCM function to give a selected level of image quality (Section 4.4), and when this is used pitch has little effect on patient dose (Ranallo and Szczykutowicz, 2015).”

This sentence could benefit from splitting it into two. At the moment it is pretty long.

46

62

1839

Editorial

“(182) Filtered back projection (FBP) is the analytical method used that has long been used for reconstructing CT images.“

“used” is superfluous.

“[…] analytical method that has long been used […]”

47

63

1866

Editorial

“If a scanner has the facility for IR, it should be used when it can improve radiological optimisation by reducing radiation exposure while maintaining adequate clinical image quality and reducing structured noise artefacts.”

”[…] when it reduces radiation exposure while maintaining […]”

48

64

1908

 

“[…] CTDIvol of 20.7 mGy, […]”

“vol” in “CTDIvol” should be subscript.

49

65

1971

Editorial

“The AAPM CT protocols provide vendor and software specific examples to use for common clinical indications (AAPM, 2022), Steps for translating ATCM settings in clinical protocols between CT scanners have been described in a number of studies (McKenney et al., 2014; Martin and Sookpeng, 2016; Sookpeng et al., 2017).“

Separate this phrase into two:

“[…] common clinical indications (AAPM, 2022). Steps for translating […]”

50

66

1979

Editorial

“[…] allowing the tube current to fall to a level whether the image quality may be compromised […]“

“[…] allowing the tube current to fall to a level where the image quality may be compromised […]“

51

67

2027

 

“These allow the variation in noise level and tube current with phantom dimension, linked to CTDIvol, to be evaluated.“

“vol” in “CTDIvol” should be subscript.

52

67

2031-2032

Editorial

“These options, called variously organ dose modulation, organ-based tube current modulation (DM) or organ effective modulation by different vendors, reduce […]“

What does “DM” stand for? Is it wrongly placed?

“These options, called variously organ dose modulation (DM), organ-based tube current modulation or organ effective modulation by different vendors, reduce […]“

53

68

2055-2059

Editorial

“These include CT angiography with removal of overlying bone which has different energy attenuation characteristics from iodine (Schulz et al., 2012), organ perfusion and blood pool imaging can be carried out (Zhang et al., 2013; Sun et al., 2018), and characterisation of structures such as urinary stones (Qu et al., 2013).“

Phrase not clearly structured. Please check.

54

68

2059

Comment

“There is also the possibility of generating a ‘virtual’ non-contrast set of images (Fig. 4.5) from a single scan with contrast to avoid a pre-contrast scan (Graser et al., 2009; Barrett et al., 2012; George et al., 2017; Rajendran et al., 2021b).”

Fig. 4.5 shows primarily virtual monoenergetic images with no mentioning of virtual non-contrast images. Unclear.

55

70

Fig 4.6

Editorial

“Images derived from the scan data in Fig. 4.5, showing iodine maps with concentration in mg ml-1 and the virtual-non-contrast mages used to visualise calcifications having a similar attenuation to the iodinated blood (white arrow bottom right).”

The word “images” after “non-contrast” was not written correctly.

56

70

2092

Comment

“Studies of the heart and coronary arteries have become common with broader fan beams and faster acquisition times.”

What is meant with broader fan beam? A fan beam with larger cone angle or a larger fan? Should be made clear.

57

71

2128-2129

Editorial

“However, dual source and wide beam techniques that allow cardiac scans to be obtained in sub-second, single rotations can be used for paediatric patients without the need for sedation.”

Phrase not clearly structured. Please check.

58

72

2170

Editorial

“In contrast to conventional, integrated energy detector (IED) CT, PCCT systems use energy-resolving x-ray detectors that register interactions of individual photons, including the energy deposited.”

The more common abbreviation is “energy-integrating-detector (EID)”

59

72

2178

Editorial

“(217) The potential advantages of PCCT imaging include improved SNR, exclusion of electronic noise, improved spatial resolution, lower patient doses, correction of beam-hardening artefacts, and the ability to distinguish multiple contrast medias.“

Incorrect plural form of “medium”.

“[…] multiple contrast media.“

60

73

2202

Comment

“The optimisation of protocols for paediatric and pregnant patients are considered separately in Sections 5 and 6. The AAPM have developed a set of protocols for specified diagnostic tasks that can be accessed via the internet (AAPM, 2022).”

To avoid the impression that only AAPM takes care of patient doses, it should be mentioned that similar documents exist also in other countries, e.g., the German Medical Association just recently updated their guidelines for QA in CT.

61

73

2202

Editorial

“The optimisation of protocols for paediatric and pregnant patients are considered separately in Sections 5 and 6. The AAPM have developed a set of protocols for specified diagnostic tasks that can be accessed via the internet (AAPM, 2022).”

“Optimisation” is singular.

“The optimisation […] is considered separately […]”

62

74

Box 4.3

Editorial

“It is recommended to keep a database with separated files recording the historical changes in the protocols (acquisition and reconstruction parameters for each clinical protocol and for each CT system in the hospital, which should be keep up to date regularly).”

“[…] for each CT system in the hospital, which should be kept up to date regularly).

63

76

Box 4.4

 

“Do not choose too high a mAs image quality reference or too low a noise reference for operation of the ATCM”

“Do not choose a too high mAs image quality reference or a too low noise reference […]”

64

76

2259

Editorial

“(225) Insufficient feedback on dose (and image quality) tracking, may lead to a dose increase over time or leave doses at a high level in order to ensure that image quality is good, despite the potential of reduction using the available CT systems tools.“

Comma is superfluous:

“[…] tracking may lead to […]”

65

77

2300

 

 

“vol” in “CTDIvol” should be subscript.

66

78

2306, 2312, 2313, 2315, 2318, 2324

 

 

“vol” in “CTDIvol” should be subscript.

67

81

Box 4.6

Comment

“In ICRP (2022) and in the introductory section of this document the range in resources and expertise that are available in different facilities is discussed. This presents significant challenges in setting out steps in optimisation that are appropriate for each facility. In order to provide assistance to users in the development of optimisation strategies for their department, the arrangements that should be in place for facilities at different stages of development are listed below for C: Basic; B: Intermediate; and A: Advanced levels. Facility staff and managers should use these lists as a guide to reflect on the arrangements that are already in place and identify those that it would be appropriate to focus on for their next stage of development. Facilities in Level D, still in the very early stages of developing optimisation should consider arrangements within level C: Basic group that they need to put in place.”

Has this not been explained in the introduction and is this not valid throughout the report? It seems to be superfluous here.

68

81

Box 4.6

 

“Regular (daily tube wam-up and air calibration) constancy checks performed by radiographers (QC).”

“Regular (daily tube warm-up […]”

69

86

2529, 2533

Editorial

“This has become a concept called shared-decision making that is a key component of patient-centred healthcare. […] Referrers, children, their parents, and carers should be involved in shared decision-making throughout the process of considering, performing, and reviewing imaging examinations.“

“shared-decision making” or “shared decision-making”? Please harmonise.

70

88

2601

 

“When a fluoroscopy operator performs an upper gastro-intestinal procedure on a neonate and does not use adequate collimation, they will give unnecessary exposure to radiosensitive breast tissue above the region imaged, and the pelvis and ovaries below.”

“upper gastro-intestinal” seems to have a different font size. Please check.

71

88

2618

Comment

5.2. Adjustments in image quality requirements and dose with patient size

The peculiarities of paediatric procedures are not equally deep described for Digital radiography, fluoroscopy and CT. For DR there are a lot of repetitions of the DR chapter, there are less for fluoroscopy and even less for CT. In all cases, it would be good to stress that the fundamentals are to be known, referring to the respective chapter, and then stress just the special issues for children/infants (see also comments 72 & 73).

72

89

2659

Comment

“(262) Understand the basics of digital imaging. Digital […]
(264) Learn exposure terminology standards. Target Exposure Index (EIT), Exposure Index (EI), and Deviation Index (DI) are discussed in Section 2.2.3. The DI indicates by how much the exposure for an imaging study deviates from the target value (see Table 2.2). Understand and pay attention to the kerma-area product (KAP) readings.”

Couldn't this be summarized in "Knowing section 2!", as this is the basis for all radiographs?

73

92

2805

Comment

“The general operation and approach to optimisation is considered in detail in Section 3, but it is critical to understand the justification and optimisation of common procedures in the paediatric community.”

Such a sentence about the fundamentals should also be added to digital radiography (see also comment 71)

74

96

Box 5.1

Editorial

“If a CT procedure is selected, child size the dose by choosing the tube potential and tube current appropriate for the size of the child (2-4 age categories are suggested for the head and 5-7 weight categories for the trunk) (ICRP, 2017).”

 Alternative: “[…] selected, adjust the dose by […]”

75

97

Box 5.2

Editorial

“Methods for dealing with differences in patient size in dose audit to obtain usable data (a size specific dose estimate, SSDE (Box 4.1) (AAPM, 2011a, 2014)”

Closing parenthesis missing.

76

97

2978

Editorial

“Exceptions include infants over 3 months (that cannot be swaddled) to age 4 years and that require intravenous contrast media;“

“and” superfluous

“[…] to age 4 years that require […]”

77

98

2987-2988

Editorial

“The CTDIvol alert level for the paediatric head age<2 years is 50 mGy and for age 2–5 years is 60 mGy; the notification value for the paediatric torso is 10 mGy for age <10 years using the 32 cm CT phantom.”

“[…] for paediatric head examinations (age < 2 years) is 50 mGy […] for paediatric torso examinations is 10 mGy […]”

78

100

3013

Editorial

“Imaging methods based on non-ionising radiations, e.g., ultrasound or MRI that can provide sufficient diagnostic information should always be considered.”

Is a smaller font used for “Imaging methods based on non-ionising radiations”?

79

100

3040

Editorial

“In this section the term ‘conceptus’ is used to describe all prenatal tissues from the moment of conception until birth, thus including both the embryo and fetus.”

The term conceptus is already in use in paragraph (134), but not defined up to this point.

80

101

3056

Editorial

“Publication 84 states that ‘After a type of examination or therapy has been justified generally, each specific instance should be justified’.“

“Publication 84 (ICRP, 2000a) states that […]“

81

102

3105

Comment

“(319) Pregnant patients may be exposed either accidentally early in pregnancy or when emergency imaging is performed prior to pregnancy status being confirmed, and in these cases an accurate estimate of conceptus dose may be required.”

This sounds like there are only two options of exposure of pregnant patients. But as described before, it is also possible to have a planned exposure that was justified (for the mother and the conceptus.)

82

103

3176

Editorial

“A position statement, the AAPM recommended

discontinuation of the use of such shielding (AAPM, 2019c), […]“

This phrase should be revised. Perhaps:

As a position statement, […]”

83

106

3279

Editorial

“[…] and can be lifesaving to both mother and fetus“

Missing full stop at end of paragraph (337)

“[…] and can be lifesaving to both mother and fetus.

84

106

3291

Editorial

“For these reasons and the continued dose lowering CT technology, CTPA is considered by many the test of choice for the diagnosis of pulmonary embolism (Leung et al., 2012; Colak et al., 2021).”

There seems to be a double space between “CTPA is” and “considered by”.

85

126

4197-4198

Editorial

“The notation recommended in ICRU, (2005) on patient dosimetry is given based on the fundamental dose quantities defined in ICRU, (2011).”

“[…] recommended in ICRU Report 74 (ICRU, 2005) […] defined in ICRU Report 85a-Revised (ICRU, 2011).”

86

128

4268

Editorial

“Images are stored and transfer using DICOM format and other data stored in standard formats.”

“Images are stored and transferred using DICOM format […]”

87

128

4290

Editorial

“More extensive and unified coding is evolving and the Radlex Playbook and LOINC radiology codes have now been merged (LOINC, 2022).”

“[…] and the RadLex Playbook […]”

88

130

4363

Editorial

“ATVS Automatic voltage selection”

“ATVS Automatic tube voltage selection”

89

133

4464

Editorial

“SPECT Single photon emission tomography”

“SPECT Single photon emission computed tomography”

90

134

4486

Editorial

“AI methodology has there are sub-domains: machine learning (ML) and deep learning (DL) that are used to create decisions based on analysis of large-scale training data sets.”

This sentence needs to be revised.

91

136

4588

Editorial

“Ka,r is the notation introduced by the National Council on Radiation Protection and Measurements (NCRP) in Report No. 168 (NCRP 2010).”

“a,r” in “Ka,r” should be subscript.

92

137

4612

Editorial

“A common unit is line pairs per millimetre (lp mm-1).”

The exponent should not be split into two lines.


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