Radiation protection of children in radiology

» Which radiology examinations contribute most to individual patient dose and collective population dose in children?

CT and interventional procedures are high dose procedures in radiology and yield higher individual patient doses than other radiological procedures do. The patient dose in CT is an important issue for children as reports suggest that in some centres the exposure factors used for scanning children are the same as for adults. This problem is relatively smaller in interventional procedures as most modern equipment automatically adjusts exposure factors based on the body thickness falling in the X-ray beam, automatically adjusts factors. CT scanning contributes most to collective dose from radiographic exposures due to the increasing use of this modality. It has been reported that, of patients having CT scans, 30% of have three or more scans.

Further reading:
METTLER, F, et al., CT scanning: Patterns, use and dose, J. Radiol. Prot. 20 4 (2000) 353-359.

» Are there special technical considerations required to reduce patient exposure and maintain good image quality in paediatric radiography?

Yes, specific actions include the following:

  • Anti-scatter grids are normally not required in paediatric radiography as the gain in image quality does not justify the increase in patient dose, except in children in their teens and when the body build is such as to increase scatter;
  • Good image detail is achieved by maintaining a balance between the use of a small focal spot size and a short exposure time;
  • High speed screen-film combinations should be used where possible to enable reduction in radiation exposure and exposure time as the reduced resolution obtained is comparatively insignificant for the majority of clinical indications; 
  • The use of Automatic Exposure Control (AEC) is generally not appropriate in children as the sensors (size and geometry) are normally designed for adult patients. Instead, exposure charts corresponding to radiographic technique, patient thickness in the X-ray beam and presence or absence of anti-scatter grid are much safer and easier to use; 
  • The radiation beam should be limited using collimation;
  • Shielding devices should be appropriately positioned to be efficient for protecting the tissues for which they are placed and to avoid unnecessary repeat examinations; 
  • Immobilization, when required, should be provided by specialized devices, if possible. 

Further reading:

EUROPEAN COMMISSION, European Guidelines on Quality Criteria for Diagnostic Radiographic Images in Paediatrics, EUR-16261, Luxembourg (1996).

» How does the radiation dose in screen-film combination imaging compare to digital imaging in paediatric radiography?

In general, digital detectors offer the possibility of dose reduction in a similar way as is done in adult radiography.

While with screen-film combinations overexposure may result in a non-diagnostic image, overexposure using digital detectors may not be as readily recognized because it may result in acceptable quality image. Increased dose in digital imaging can also be caused by re-exposure by technologists not being detected (in most systems currently available), ease and convenience with which images can be taken thus leading to covering a larger area of a patient's body or repeating the examination. Whereas it is possible to have dose reduction, many studies indicate that in actual practice, more so where optimization is lacking, there can be an increase in patient dose.

Further reading:

INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Managing Patient Dose in Digital Radiology, ICRP Publication 93, Pergamon Press, Oxford and New York (2004).

» Can low dose fluoroscopic image replace conventional radiographic examinations?

No.

An image recorded on film with a high-speed cassette provides a permanent record that can cover the necessary area, e.g. leg, spine. However, when high image detail is not required, for example in follow-up examinations in patients with scoliosis, leg length discrepancy, a stored pulsed fluoroscopic image using last-image-hold may be satisfactory. 

» What are the typical dose levels in paediatric radiography and fluoroscopy?

Typical values of Entrance Surface Dose (ESD) per radiograph and Dose Area Product (DAP) for common paediatric fluoroscopy examinations are given in the table below.

Table: Typical dose levels in paediatric radiology

ExaminationEntrance surface dose (µGy)
Age
0151015
Abdomen AP1103405908602010
Chest PA/AP608011070110
Pelvis AP1703505106501300
Skull AP 6001250  
Skull LAT 340580  
 Dose area product (mGy.cm2)
MCU43081094016403410
Barium meal7601610162031905670
Barium swallow5601150101024003170

» What are the most significant things I can do to reduce the child’s dose during fluoroscopic examinations?

Many actions are similar to those recommended in adult procedures:

  • The patient should be positioned as close as possible to the image intensifier;
  • The X-ray tube should be as far away as possible from the patient table in order to avoid excessive skin dose;
  • The lowest frame rate acceptable and last-image-hold facility should be used. Some centres prefer to set a 'floor' (a kVp) below which the system will not go, such as 70 kVp for paediatric patients and 80 kVp for adults; 
  • Additional copper filtration also reduces patient dose. 

» Are there situations in which I should consider reducing the number of radiographic projections?

Yes.

When performing radiographs of long bones in children the opposite limb should be imaged only if needed by the radiologist and only limited views used. In chest radiographic examination a lateral projection may not be required routinely. When a follow-up examination is justified the number of projections should be restricted to evaluate previous findings. Lumbar spine for follow-up and sometimes for regular examination is an example with too many projections like AP, lateral, obliques, and L5-S1 spot film.

» How should one deal with possible pregnancy in adolescent patients?

The necessary information on possible pregnancy should be obtained from the patient herself. 
In female children who are menstruating and are referred for high dose procedures such as CT abdomen or interventional examination, the possibility of pregnancy should be considered.

Read more:

  • NATIONAL RADIOLOGICAL PROTECTION BOARD, Doses to Patient from Medical X-Ray Examinations in the UK: 2000 review, NRPB-W14, Chilton (2002). 

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