Radiation protection of patients in gastroenterology

» Are there guidelines for radiation protection of patient in gastroenterological procedures using fluoroscopy?

Yes. 

The IAEA in cooperation with World Gastrointestinal Organisation (WGO) and American Society for Gastrointestinal Endoscopy (ASGE) has prepared guidelines that are also available on the WGO website.
The main features of the guidelines

Procedure-related:

  • Minimize fluoroscopy time;
  • Use collimation;
  • Take as few radiographic images as possible;
  • Use magnification appropriately; 
  • Decrease the patient to image receptor (image intensifier or flat panel detector) distance; 
  • Increase the X-ray tube to patient distance; 
  • Be aware of tube angulations. 

Equipment-related:

  • Use the lowest manufacturer’s setting of fluoroscopic dose rates and the highest kVp consistent with maintenance of image quality; 
  • Position the X-ray source relative to the patient and staff so as to deliver the least possible dose; 
  • Use pulsed fluoroscopy rather than continuous, and use the lowest pulse frequency compatible with adequate image quality; 
  • Use last image hold and image capture; 
  • Be aware of alarm levels for time and higher dose rates in fluoroscopy; 
  • Make sure appropriate quality control is performed. 

» What are typical radiation doses associated with gastroenterological procedures?

ProcedureMean
dose
area
product (Gy.cm2)
Mean
effective
dose
(mSv)
Equivalent
number of
PA chest
radiographs
(each 0.02 mSv)
ERCP
(diagnostic) [HA]
153.9195
Percutaneous
transhepatic
cholangiography
(PTC) [HA]
318.1405
Bile duct
drainage [HA]
389.9495
Bile duct
stenting [HA]
5414700
ERCP
(therapeutic) [OL]
90201000

[HA] HART, A., WALL, B.F., Radiation exposure of the UK population from medical and dental X-ray examinations. NRPB-W4 (2002)

[OL] OLGAR, T., BOR, D., BERKMEN, G., et. al. Patient and staff doses for some compelx X-ray examinations, J. Radiol. Prot. 29 (2009) 393-407.

Typical doses from fluoroscopy procedures →


Read more:

  • HART, A., WALL, B.F., Radiation exposure of the UK population from medical and dental X-ray examinations. NRPB-W4 (2002) 
  • OLGAR, T., BOR, D., BERKMEN, G., et. al. Patient and staff doses for some compelx X-ray examinations, J. Radiol. Prot. 29 (2009) 393-407.

 

» Can I be sure that I am delivering the lowest possible dose to my patient if I am using state-of-the art digital equipment?

No. 

Digital equipment including flat panel detectors has the potential to reduce radiation exposure if used properly. But experience shows that lack of understanding of the features of digital imaging systems has resulted in higher radiation exposures to staff and patients. The reason for increased radiation dose from digital equipment stems from the fact that overexposure in digital imaging results in better quality images and can go undetected. Modern equipment provides the facility with storing fluoroscopically generated images, reducing the need to have cine or radiographic images that require much higher exposure than fluoroscopic images. Using this feature can help to reduce dose.

» Why is collimation an important feature of dose reduction?

Reducing the field-of-view is beneficial in

  • reducing the stochastic risk to the patient by reducing the volume of tissue at risk; 
  • reducing scatter radiation to the patient and in-room personnel; 
  • reducing potential overlap of fields when the X-ray beam is reoriented.

» Is risk to patient per procedure the same regardless of the patient?

No. 

Many patient-related factors will affect the dose and the risk. These include:

  • Body mass or body thickness in the beam: larger, thicker patients require higher doses to achieve quality images;
  • Young age: young patients are more sensitive to radiation; 
  • Patient’s disease and indication for procedure: the more difficult the procedure, the higher the dose; 
  • Previous radiation exposure: exposures are cumulative; 
  • Radiosensitivity of some patients (ataxia telangiectasia); connective tissue disease and diabetes mellitus: some conditions increase radiosensitivity. 

» How do I know how much dose I delivered during a procedure?

You must record the dose area product (DAP), currently known as kerma-area-product (KAP), and the fluoroscopy time. This will allow comparison with diagnostic reference levels or guidance levels. 

» Is there a difference in radiation dose between diagnostic and therapeutic procedures?

Yes. 

The screening times and thus the doses will generally be higher for therapeutic procedures like stent insertion, stricture dilatation, stone extraction, lithotripsy, needle knife sphincterotomy, multiple wire use as compared to diagnostic fluoroscopies.

» How to deal with radiation protection of a pregnant patient?

When a pregnant patient has been judged to require endoscopic retrograde cholangiopancreatography (ERCP), then optimization of the procedure should be performed by strict adherence to good techniques. If there is a possibility of the primary X-ray beam intercepting the foetus, placing a lead apron between the X-ray source and the foetus will reduce the radiation exposure, but remember lead aprons are designed to protect against scatter radiation, which is less energetic. 

When the foetus is exposed to radiation scattered internally, protection by a lead apron placed externally is ineffective. The patient’s position (supine, prone, or lateral) should be adjusted to minimize foetal exposure. A posterior-anterior projection of the X-ray beam also results in a foetal dose that is 20% to 30% lower than an antero-posterior projection because of the increased shielding from the mother’s tissues. The lateral projection would also provide increased foetal shielding, but the patient entrance dose rate will generally be 3 to 7 times higher compared with a frontal projection. As a result, the lateral projection will result in higher foetal dose.

An alternative technique to avoid radiation exposure completely is to perform ERCP without fluoroscopy using wire-guided cannulation techniques. After biliary sphincterotomy and balloon sweeping, choledochoscopy can be used to confirm stone clearance. This approach, however, is technically challenging and has been described only by very experienced biliary endoscopists. 

» How to deal with radiation protection of a child?

All guidelines stated above apply with special emphasis on protection of the thyroid and, in addition, the breast in younger females by shielding or beam adjustment (collimation, orientation and exposure factors).