National Patient Dose Database (NPDD)

This database was set up in 1992 at the National Radiological Protection Board (NRPB) following publication of the National protocol for patient dose measurements in diagnostic radiology. Patient dose measurements made by hospital x-ray departments throughout the UK according to the national protocol are sent to the HPA Radiation Protection Division for national collation and analysis. The database is reviewed every five years, the latest review being for 2001-2005 and published in HPA-RPD-029.

These five-yearly reviews contain recommendations on national reference doses for common x-ray examinations, which are a useful aid to the optimisation of patient exposures. Analysis of the trends in patient doses seen in the NPDD is used periodically to estimate the collective dose to the population of the UK from medical and dental x-ray examinations. This was last done in 2001 and published in NRPB-W4.

Radiology departments in the UK are encouraged to continue to supply patient dose data to the HPA for national collation. This is usually done by medical physicists or radiographers, after first using the data in local radiology audit and quality assurance programmes as required by British legislation. All data submitted to the HPA will be treated confidentially but, if sufficient hospitals respond, it will allow the regular reviews of the NPDD truly to reflect national practice. The next review is scheduled for the end of 2010.

Guidance for contributors to the NPDD

The original guidance for data contributors was provided in the national protocol in 1992. This is still worth reading for its extensive discussion of the choice of dose quantities to be measured, and the practical techniques of dose measurements. The details requested for the database (on the patient, examination technique, and imaging equipment) were originally specified in the forms in Appendix D of the national protocol. However, in the last ten years there have been many developments in medical imaging equipment and procedures, and there are now new forms which list the data that are currently of interest, including two for dental radiography. Essential items are highlighted on the forms, but contributors are encouraged to provide as much of the other information as possible.

Form 1 Dose per radiograph (PDF, 18 KB)


Form 2 Dose per examination or procedure (PDF, 20 KB)


Form 3 Dental dose per intra-oral mandibular molar radiograph (PDF, 13 KB)


Form 4 Dental dose per panoramic radiograph (PDF, 18 KB)

Data are particularly required for images taken with new technology, such as computed radiography (photostimulable phosphor plates) and flat panel digital detectors, as well as conventional screen/film and image intensifier systems.

Those types of radiograph and examination which are of particular interest are, in order of priority, as follows.

• Radiographs and examinations that already have national reference doses.
• Common radiographs on children.
• Examinations that make a major contribution to collective dose.
• Other common high-dose procedures. (>10,000 per year in the UK, effective dose >4 mSv)
• Rare but very high dose procedures. (effective dose >10 mSv)

Examples of examinations falling into types 2-5 are shown below, in order of priority.

Paediatric radiographs
Chest, abdomen, pelvis, and skull

Adult examinations
PTCA (specify number of artery dilations and stents)
Peripheral arteriography (specify whether one or both legs)
Hip radiography
Angioplasty (specify anatomical location)
Vascular stenting (specify anatomical location)
Renal arteriography
ERCP (separate diagnostic and interventional)
Embolisation (specify anatomical location)
Radiofrequency cardiac catheter ablation
Kidney stenting
Mesenteric angiography
TIPS

(The NPDD does not include information on computed tomography (CT) examinations. These are very important and a separate national database for patient doses from CT examinations has been established. That database is called PREDICT (Patient Radiation Exposure and Dose In CT). It is intended that the data in PREDICT will be reviewed at regular intervals in a similar manner to NPDD.)

Data are best supplied to the HPA in electronic format, for example, as an Excel spreadsheet. They can be e-mailed or sent on a disk to:

Dr David Hart
Health Protection Agency

Centre for Radiation, Chemical and Environmental Hazards
Radiation Protection Division
Chilton, Didcot, Oxon, OX11 0RQ

E-mail: David.hart@hpa.org.uk

Telephone: 01235 822647

Data on paper will also be accepted, but as the risk of transcription errors is greater, electronic formats are preferred.

Last reviewed: 23 November 2009