Radiation protection of medical staff in interventional fluoroscopy

» Is there a relationship between staff dose and patient dose in fluoroscopy?

Yes. Reducing patient dose will lower staff doses too. However the opposite is not true as staff dose can be reduced by the use of personal protective devices such as lead aprons, which will not reduce patient dose. There are a large number of factors that can reduce patient and staff dose. Remember: Not attempting to minimize patient dose is equivalent to neglecting your own radiation protection.

» Where should I stand in relation to the X-ray tube during a fluoroscopic procedure?

The scattered radiation from the patient comprises the main source of radiation dose to staff. Measurements have shown that scattered radiation from a patient’s body is more intense at the entrance side of X-ray beam, i.e. on the side where the X-ray tube is located. Therefore it is better to stand on the side of the detector, that is the exit side, and not on the X-ray tube side during a fluoroscopic procedure. Typically only around 1% to 5 % of the radiation falling on the patient body comes out on the exit side. So if you stand on the side of transmitted beam you encounter scattered radiation corresponding to only 1% to 5% of the incident beam intensity, whereas you encounter scattered radiation corresponding to 100% of the entrance beam intensity on other side.

» How effective are lead aprons in fluoroscopic work?

Lead aprons are the most effective personal radiation protection means and should be worn by everyone in a fluoroscopy room (except the patient). Lead aprons may reduce the dose received by over 90% (85%-99%) depending on the energy of the X-rays (kV setting) and the lead equivalent thickness of the apron. The thickness of a patient’s body part in the beam determines the kV that the machine uses. The system will select a higher kV than for a thinner one and thus staff will be exposed to more scattered radiation. The same lead apron will provide less protection when the beam is of higher energy (or higher kV). A lead apron with 0.35 mm lead thickness equivalence should be sufficient for most fluoroscopic procedures. For high workload, a wrap-around lead apron with 0.25 mm lead equivalence that overlaps on the front and provides 0.25+0.25=0.5 mm lead equivalence on the front and 0.25 mm on the back would be ideal. For a low work load a 0.25 mm lead equivalence apron should do well.

» Should I use lead impregnated gloves in fluoroscopic work?

Generally not. Leaded gloves may reduce the dose to the hands by 15%-30% as long as the hands remain outside the primary X-ray beam. In contrast, if gloves are worn and the hand is in primary beam, the automatic exposure control system will trigger an increase in exposure (kV) which increases the dose to the hands, as well as patient and staff dose. Furthermore, a false sense of security might increase the time the hands remain inside the primary beam, nullifying the potential of the gloves to protect against radiation.

» Do different views such as posteroanterior, lateral and oblique have an effect on patient dose?

Yes.

Different projections in a fluoroscopic procedure result in different radiation dose to patient and staff. Whenever a projection with high obliquity is used, the photons have to pass through a thicker section of the patient’s body. This results in an increase of the fluoroscopic exposure parameters (mainly kV) in order to maintain image quality. The table below gives the relative exposure rates for different projections. 

Table 1: Skin exposure variation in exposure rate (DAP rate) with projection
(Adapted by Cusma et al., 1999, assuming 1 R~10 mGy)

ProjectionFluoroscopy
entrance
dose rate
(mGy/min)
Cine entrance
dose rate
(mGy/min)
AP31388
RAO 30°19203
LAO 40°20216
LAO 40°, Cranial 30°80991
LAO 40°, Cranial 40°991236
LAO 40°, Caudal 20°29341

Anthropomorphic phantom (average-sized) measurements.

» I do not use fluoroscopy very often. Is there a risk of developing cataract for me?

The ICRP has recently, in April 2011, defined a threshold value of absorbed dose for cataract of 0.5 Gy to lens of the eye. This is almost a tenfold reduction as compared to the previous value of 5 Gy given by the ICRP. This change has been based on recent data that indicate cataract occurrence at doses from 0.1 to 1 Gy. For occupational exposure in planned exposure situations the Commission now recommends an equivalent dose limit for the lens of the eye of 20 mSv in a year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv. Performing a few fluoroscopic procedures per week that require only a few minutes of fluoroscopy time per procedure (i.e. less than 5 min), sufficient protection of the eye lens can be achieved by using a lead screen or wearing lead glass eye wear. But if protection is not used, there can be a risk.

For procedures that require long fluoroscopy times (i.e. more than 10 minutes) per procedure and many procedures per day, such as in busy interventional cardiology or interventional radiology suites, there is a substantial risk of lens opacity. However, even in these situations, one can use effective protection to reduce the probability of cataract to a negligible level.
A dosimeter placed outside the lead apron at neck level should serve well in estimating the dose to the eyes until advanced eye dosimeters are available.

» Do I need special radiation protection training for working with fluoroscopy machines?

Yes. The levels of education and training should be commensurate with the level of usage of radiation. Professionals involved in fluoroscopy should receive special training that meets the needs arising from any procedure one might participate in. The training should be targeted at specific needs in fluoroscopy work and should be provided by an expert in radiation protection, such as a medical physicist knowledgeable in protection aspects in fluoroscopy. If the professional lacks training this could become a radiation safety issue for staff as well as for patients.

» Why is periodic quality control (QC) of fluoroscopic equipment necessary?

Periodic QC is required to ensure the stability and suitability of performance of the fluoroscopic equipment for use in clinical practice. Periodic QC guarantees that the doses delivered to patients and staff will not exceed acceptable values if all procedures are carried out appropriately. It also provides confidence about the safety of the equipment. Most professional societies recommend testing at least annually and whenever the equipment is repaired. Some old equipment may require more frequent testing. Overexposures may be caused if quality control is not applied.

» Should I use a protective screen, as I am not used to it and I find it a hindrance in my work?

Yes. A protective screen is a very effective means of radiation protection. It can attenuate the scattered radiation used in fluoroscopy settings by more than 90%. The benefits regarding personal eye protection (e.g. to the eyes) is much more than the small inconvenience at the initial stage. Most interventionists now find it acceptable to use the screen keeping in mind the associated benefits. Cooperation with the manufacturers of such systems may improve the usability of protective devices by tailoring them to the needs of practitioners.

» To whom should I address my concerns about radiation protection?

Concerns about radiation protection should be addressed to the local medical physicist or radiation protection officer knowledgeable in protection aspects in fluoroscopy. Where specialists in radiation protection issues are not accessible, concerns could be addressed to practitioners involved regularly in radiation related procedures such as radiologists. However, caution should be used since radiologists and radiographers are not necessarily experts in radiation protection. These days it is much more convenient to get easy access to relevant information from websites such as this one and this helps in dealing with situations of lack of local expertise that is very common.

» How should I monitor my radiation exposure?

The best way to monitor staff doses is the comprehensive utilization of personal dosimetry as available in your country. This is a legal requirement in most countries. In addition one may use newer electronic means of monitoring. These normally do not replace the dosimetry that is legally required, but they do provide quick information about the dose simultaneously with each procedure. Where personal dosimetry is not available, a dosimeter attached to the C-arm may provide an estimate of the dose received by medical personnel.

» What is the magnitude of staff doses associated with fluoroscopically guided surgical procedures?

Table 2: Mean doses to staff from procedures involving the use of fluoroscopy

SpecialityProcedureEffective
dose
per
procedure
(mSv)
Eyes
dose
per
procedure
(mSv)
Hands
dose
per
procedure
(mSv)
Ref.
Vascular
surgery
EVAR10.00770.00970.0343[Ho
et al.,
2007]
UrologyPCNL20.01270.0260.0335[Safak
et al.,
2009]
OrthopaedicsHand surgeryN/AN/A0.01-0.32*[Giordano
et al.,
2007]
,

[Singer
et al.,
2005]
Intramedullary
nailing of
femoral and
tibial fractures
N/AN/A1.27[Müller
et al.,
1998]
Arthroscopy0.016N/AN/A[Theo-
charopoulos
et al.,
2003]

 

 

 

Hip0.0024N/AN/A
Spine0.0084N/AN/A
Kyphoplasty0.096N/AN/A

EVAR: Endovascular aneurysm repair.
PCNL: Percutaneous nephrolithotomy.
* Mini C-arm fluoroscopy.
N/A: Not available.

» Key points to remember for staff dose management in fluroscopy.

Be aware that by using radiation protection principles and tools it is possible for staff in most situations to carry out the full work load typical in a busy facility still keeping the annual radiation dose in the range of 0 to 5 mSv (against 20 mSv that is the dose limit). Some tips are:

  • Know your equipment;
  • Use a lead apron that provides at least 0.25 mm lead equivalence on the back and with overlapping 0.25 mm on the front (0.25 mm + 0.25 mm = 0.5 mm);
  • Use lead glass eye wear; 
  • Use protective shields (mounted shields/flaps, ceiling suspended screens as applicable); 
  • Keep hands out of the primary beam unless unavoidable for clinical reasons commensurate with good practice;
  • Stand in the correct place: whenever possible on the side of the detector and opposite the X-ray tube rather than near the X-ray tube; 
  • Keep your knowledge of radiation protection issues up-to-date; 
  • Address your questions to appropriate radiation protection specialists; 
  • Always wear your personal radiation monitoring badge(s) and use them in the right manner; 
  • Make sure that fluoroscopy equipment is properly functioning and periodically tested and maintained; 
  • All actions to reduce patient dose will also reduce staff dose. 

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