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

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Correction Needed

Suggested edit

83

2414-5

Delete:

“Use of weight is a better alternative to age that can be measured relatively easily.

Insert:

“While the use of the patient’s current weight is a better alternative than the patient’s age to select necessary radiographic techniques, the body part thickness should be measured with calipers prior to exposure and used by the radiographer to more accurately set the required technique factors.”

83

2418

Replace this text with text in box to the right.

Insert:  “. . . reduced pulse rates during pulsed fluoroscopy to the lowest setting that provides adequate temporal resolution in the image.”

83

2418

Incomplete

Include: “increase SID and position the patient as close to the imaging receptor as possible”

88

2629

Delete

“children under the age of 4 years (or <12 cm in AP diameter)

Correct reference already in “reference list”

Replace with:

children under the age of 3 years (or <12 cm in AP diameter)(Kleinman et.al, 2010)”

88

2632-3

Delete “When high image resolution is necessary in interventional procedures, the use of copper filtration with a grid is useful.

Use of a grid and copper filtration does not affect resolution.

Replace with:  “When a higher contrast image at a well-managed dose is desired during interventional procedures, the use of copper filtration with a grid is useful.”

88-9

2636-7

Replace: 

“(259) The use of pulsed fluoroscopy, at the lowest rate tolerated by the operators at the facility, 2636 reduces the radiation dose significantly below the continuous fluoroscopy setting (Box 3.2).”

Insert:

“(259) Reducing the pulse rate during  pulsed fluoroscopy, to the lowest setting that still provides acceptable temporal resolution for the operator substantially reduces the patient’s radiation dose below that of  the continuous fluoroscopy setting (Box 3.2).”

89

2638-40

Replace:

“Experienced practitioners use 7.5 or lower frames per second for routine general fluoroscopy, but interventional cases require faster rates for cine acquisition mode; higher frame rates are often used for video modified barium swallow studies.”

Insert:

“Experienced practitioners typically use the following pulses per second respectively for pic lines, GI or VCUG examinations, barium video swallow studies, abdominal or neuro FGI studies, and cardiac FGI studies: 1 – 2, 2 - 4, or 10 – 15, 3.75 – 7.5, and 3.75 - 15 pulses per second. Typically, practitioners are able to reduce the pulses per second they use as more experience is gained.”

89

2647

5-7 weight categories is too much for pediatric CT optimization of the body, and there should be a minimum of 3 for the head.

Suggest using “4-5”; Head CT protocols should be a minimum of 3 for peds

89

2648

Add additional reference to existing list for another source of CT paediatric protocols.

Insert inside the parenthesis at end of citation listings: “ . . . Image Gently, 2023)”

Citation for Reference List:

 Image Gently, 2023. Image Gently Development of Pediatric CT Protocols 2014. Available at https://www.imagegently.org/Portals/6/Procedures/IG%20CT%20Protocols%20111714.pdf (last accessed 6 Mar 2023).

89

2654

Is there a newer citation than Don, 2004? 

Here is an example study published in 2021 for ped chest CXR: doi: 10.1097/MD.0000000000024760

90

2686

Replace “. . .techniques may be more appropriate. Focused …”

Insert:  “. . .techniques are required. Focused …”

90

2699

The initial sentence of this paragraph contradicts the thickness appropriate for grids in the listed reference.

Interestingly, I believe the initial sentence is more correct than the values quoted in the reference!

90

2719

Move: “Wide open collimators may affect EI, giving a false indication of the exposure.”

This belongs with Section 2.2.3. Overall, Section 2.2.3 may benefit from a paragraph describing factors that influence EI calculations.

21

Table 2.2

Remove, old data.

Section 2.2.3 generally relies on dated information. The updated report AAPM TG232 (Current state of practice regarding digital radiography exposure indicators and deviation indices) found that often DI values exceed a value of +/-3 and that variance is highly dependent on the type of exam performed. I believe that most readers will fail at adhering to the recommendations in Table 2.2 and ultimately ignore it or dishearten the technologists.

90

2720-27

This entire paragraph needs to be rewritten. It is poorly focused and most of its content has little to do with “additional filtration”. For example if you want a paragraph on mobile radiography equipment limitations that is fine, but it should not be in a paragraph about additional filtration. The next few rows contains some suggested content for a paragraph on “additional filtration”.

90

2720-21

Replace:

In the paediatric patient, total radiation must be kept low. This is the case with digital radiography or when high speed radiography systems are used.

Insert:

“In the paediatric patient, total radiation dose should be carefully managed to provide image quality appropriate to type of clinical examination. While reducing the radiation dose is a desired objective, this objective cannot be at the expense of appropriate image quality.”

90

2721-27

Replace:

Not all generators (particularly mobile radiography units) are capable of delivering the short exposure times that are required for these higher tube potential techniques. Consequently, lower tube voltages are often used for paediatric patients and these result in higher patient doses. The insertion of additional filtration will reduce the incident air kerma rate and allow delivery of lower doses with higher tube voltages within the range of exposure times available on such equipment. The benefit of copper filtration is discussed in Box 2.3 and Section 2.2.2.

Insert:

“The insertion of additional copper filtration in the x-ray beam is an effective method of reducing the incident air kerma to the patient while delivering the incident air kerma to the image receptor necessary to provide the desired image quality. While 0.2 mm copper reduces the patient air kerma more than 0.1 mm copper, tradeoffs exist.  The 0.2 mm filter reduces contrast in the image more than the 0.1 mm filter. Since more x-ray photons are attenuated in the 0.2 mm filter, more photons must be generated which requires more high voltage, tube current and/or exposure time. Increasing the voltage reduces contrast in the image.  Increasing the exposure time may result in more motion unsharpness in the image. Increasing the tube current time product may also result in a switch from the small focal spot to the large focal spot size, also resulting in reduced image sharpness. As the size of the paediatric patient increases, the choice of 0.2 mm of copper may may sacrifice too much image quality for a limited reduction in patient dose. The benefit of copper filtration is discussed in Box 2.3 and Section 2.2.2.

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2741

It may be distracting to display EI/DI/KAP on all radiographs.

Insert:

“When these values are not displayed, consult with the manufacturer to ensure that members of the imaging team can identify these values within the DICOM metadata.”

91

2784-89

Delete all original text:

“In general, a small focal spot can be used in imaging the trunk for neonates and infants whereas a larger one is used for children and adults. A nominal focal spot value between 0.6 2785 and 1.3 mm is usually suitable for paediatric patients. When a bifocal tube is used for 2786 radiography, the nominal focal spot value should be used, allowing for the most appropriate 2787 setting of exposure time and tube voltage at the chosen SID. This may not always be the smaller 2788 one (ICRP, 2013b). “

Insert:

“The small focal spot of a bifocal x-ray tube (nominal focal spot sizes of 0.6 and 1.2 mm typically) should be used for neonates, infants and children. This choice includes any examination using 100 cm source to image receptor distance (SID) and no grid.  As the patient increases in size, the large focal spot should be selected when the maximum rated tube current for the small focal spot and a 20 millisecond exposure do not provide enough mAs to properly expose the image receptor.  Exposure times greater than 20 milliseconds with the small focal spot, on larger children should be avoided to prevent motion unsharpness in the image. When the SID exceeds 100 cm, use of the large focal spot is necessary for smaller patients to avoid exceeding exposure times greater than 20 milliseconds (ICRP, 2013b).”

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2797-8

Delete: “. . . performed with <60 kV and approximately 1 mAs.”

Insert:

“. . . performed with 70 kV and less than 1 mAs. In this case, all the reduction should come from reduced mAs, not voltage. The voltage should not be reduced below 70 kV unless the minimum mAs setting of the unit exceeds the required technique at 70 kV.  Voltages less than 70 kV provide little improvement in contrast in the image, but substantially increase the radiation dose to the patient compared to 70 kV.”

92

2801-03

Title of section non descript

Fluoroscopic Imaging:  mobile C-arm and tilt table units

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2810

Remove “. . . safe and quality imaging . . .”

Replace with “. . . required image quality at properly managed radiation dose levels

92

2811

Remove “. . .far fewer x-rays should be. . .”

Replace with “. . .  less x-ray photons are . . .”

92

2818

Providing the original reference to the reader is more helpful than a general IG website location.  Replace (IG, 2022b)

The original reference is (Ward, 2008):   Ward VL, Strauss KJ, Barnewolt CE, et.al. Paediatric radiation exposure and effective dose reduction during voiding cystourethrography.  Radiology 249(3) pp 1002-9.

93

2828

A recent (2022) important publication has become available.  Delete “. . . Few have as yet been established for fluoroscopy, but the European union . . .

Add the following:  ”. . . While few paediatric DRLs have as yet been published for general fluoroscopy, a few publications provide important information.  A recent publication (Somasundaram, 2022) allows any site, paediatric or adult, to estimate exposure levels as a function of patient thickness at the 75^th percentile for examinations conducted at their site in the operating room with mobile c-arm units, or the four general paediatric examinations performed in Radiology of gastro-intestinal, voiding cystourethrogram, video swallow, or tube placement provided the site can determine the average exposure level for a handful of patients of the most common size imaged for each of the types of studies. The European . . .”

Somasundaram E, Brady SL, Strauss KJ.  Application of reference air kerma alert levels for paediatric fluoroscopic examinations.  J Appl Clin Med Phys 23(9) e13721.

93

2835

Delete “. . . dose from patients should be lower. . .

Insert:  “. . . dose rate from patients is lower. . .

93

2843

Delete “ . . . large relative size and noise of an image intensifier can . . .

Image intensifiers are silent in their operation!

Insert “. . . large size of the image intensifier and typical noises of the fluoroscopic unit can . . .

93

2848-49

Delete “. . . 

(the default setting is grid out where children are 2848 imaged primarily), . . .”

This clause is deleted here because it is confusing and contradictory with other statements about the use of the grid elsewhere in the document.

93

2850-51

Delete “. . .  fluoroscopy on the lowest possible setting.

. . .” and insert information in the box to the right.

Add  “. . . fluoroscopy on the lowest pulse rate setting that provides adequate temporal resolution.”

93

2851

Add at the end of the sentence the statement to the right

Add  “. . . If possible, any dose reduction feature of the fluoroscope should be set as the automatic default value at the beginning of an examination. The operator can quickly make changes to the controls if the image quality is not adequate.  This avoids patient dose rates higher than necessary that may result from the settings used for the previous patient.”

93

2852-54

Delete “(288) Pulsed  . . . The use of . . .”

Add:  (288) The selected  pulse rate of the pulsed fluoroscopy settings should be on the lowest setting that provides the operator with adequate temporal resolution, which is determined by the type of procedure being performed. This setting may be as low as 1 – 2, 2 -4, or 10 – 15 pulses per second respectively for placement of pic lines, VCUG or GI studies, or video swallow studies. The use of . . .”

93

2861

65 kV provides negligible improvement to image quality, but needlessly increases patient dose.

.Change “65” to “70”.

93

2862

Delete  “. . .The tube current usually. . .”

Insert “. . . The root mean tube current for either continuous or pulsed fluororscopy usually. . .”

93

2863-66

Delete the last sentence of the paragraph beginning on line 286.

The automatic brightness control system will select the kV for an infant.  It will be higher if Copper filter is added compared to standard filtration.  The deleted information is confusing as written and not something that is easily configured in the field so it is best left unsaid.

94

2867-70

The first and last sentences should be struck. The first sentence is not true. The last sentence contradicts statement in lines 2858-9. The middle sentence should be rewritten; see box to righ. 

Insert: 

“During fluoroscopy with a mobile C-arm, the patient should remain as far from the x-ray tube (at least 30 cm) and as close to the flat panel detector or image intensifier as is comfortable to reduce dose. When a tilt table is used with adjustable source to image receptor distance, the tower holding the image receptor should be positioned as close to the exit plane of the patient as is comfortable to reduce dose to the patient. If the distance of the focal spot to the table top is adjustable (under table x-ray units). the maximum allowed distance should be used for children to reduce patient dose.

94

2872

Delete :”. . . time). Although . . .”

The reader needs to be alerted that the display of  P_KA may have a large error if not properly calibrated.

The reference may be found at:

Lin PJP, Schueler BA, Balter S, et.al.  Accuracy and calibration of integrated radiation output indicators in diagnostic radiology: a report of thee AAPM Imaging Physics Committee Task Group 190. Medical Physics 42(12) pp 6815-6829

Insert:

“. . . tune). The displayed values of P_KA or K_a,I on the fluoroscope may have errors of + 30%.  This relatively large error can lead to misinterpretation of actual doses to the patienst especially if the facility has more than one fluoroscope, e.g., one unit could be 25% high while another is 25% low. This error can and should be eliminated by measuring the magnitude of the errors of the displayed values annually and developing calibration factors as needed. A protocol for making these measurements has been published (AAPM, 2015).  Although. . .”

94

2876-78

Move the follow information to Section 5.2.3

“. . .however, when using cine mode, this is not true. Therefore, for safety reasons, it is suggested that cine mode be turned off when imaging infants and children unless required for interventional procedures.

Mobile C-arms in the OR and general fluoroscopic units in the Radiology Department typically do not have a cine mode.

94

2879-81

This paragraph as written is more applicable to a radiographic as opposed to a fluoroscopic application.  Most grids in fluoroscopic applications are stationary and do not move during the exposure.  While 8 to 1 grid ratios are good for small children, many fluoroscopic units do not allow any access to the grid.  All manufacturers use fluoroscopic grids with higher grid ratios because it is assumed adult sized patients will be imaged.

94

2882-4

ADRC may routinely be switched off in Europe for the example given, but this is not routinely done in the US.

94

2885-8

Information in this paragraph should be placed in Section 5.2.3

94

2882

Add the text in box to the right at end of paragraph

“. . . (ICRP, 2013b).  However, while a unit may have the ability to insert additional copper filtration into the x-ray beam, this may not be the default setting out of the factory.  A configuration change in the field may be necessary to utilize the additional filtration.”

94

2894-98

Delete original text and replace it with text in box to the right.

Insert the following:

(297) C-arm (portable) units for intra-operative use are typically configured for adult patients, which results in higher doses to paediatric patients and higher scatter radiation to the operator than necessary during paediatric imaging. Mini C-arm units are FDA approved for orthopaedic fluoroscopy of extremities; but are unfortunately sometimes used for other applications. C-arm units configured for paediatric imaging should be considered for use at child-based facilities.”

95

2918-22

Delete the two sentences beginning on line 2918 and replace with edited version in box to the right.

Insert:

Substantial radiation dose reduction can be achieved by reducing the pulse rate. Cardiac procedures may require up to 30 pulses per second to capture the rapid beat of the paediatric heart, while most other interventional paediatric procedures can use pulse rates as low as 3.75 - 7.5 pulses per second (ICRP, 2013b; Image Gently, 2020b).

96

Box 5.1

Change: “2-4 age categories are suggested for the head and 5-7 weight categories for the trunk”

Suggested: “3 or more age categories are suggested for the head and 4-5 weight categories for the trunk”