Review of dose data

Colin Martin and David Sutton

• Colin Martin and David Sutton

Survey of barium enema doses

• Survey of barium enema doses

• Review of dose data

• Factors contributing to higher doses

• Optimising of technique

• Coronary Angiography

• Possible use of screening time for DRLs

The range in doses from fluoroscopy procedures is much larger than for radiography

• The range in doses from fluoroscopy procedures is much larger than for radiography

• Influenced by:

• Equipment

• Operator technique

• Patient factors

Collection of KAP data for recent survey from one hospital

• Collection of KAP data for recent survey from one hospital

• Distribution for 120 patient barium enema exams

Extent and severity of disease

• Extent and severity of disease

• Condition of patient

• Patient size

• It is helpful to record patient weight, as this has a substantial influence on patient dose

Collect data for 20-30 patients at least

• Collect data for 20-30 patients at least

• The spread of data is greater for fluoroscopic procedures,

• Depends on:

• Patient’s condition as well as size

• 0perator skill and technique

Completion of paper forms by operators

• Completion of paper forms by operators

• Advantage - details such as patient weight can be included more readily

• Disadvantage - limited number of patients

• Use data from computer database

• Advantage – information for large numbers of patients

• Disadvantage – Accuracy of data entry

Collect data for 20-30 patients at least

• Collect data for 20-30 patients at least

• If possible choose patients with mean weight of 70 kg

• Pick patients between 50 kg – 90 kg

• Exclude other data, consider validity of outliers – wrong units, unusually heavy patient if no weight data

• Calculate mean KAP value

All radiologists and

• All radiologists and

• radiographers have their

• own techniques

• Some take more images, others use more fluoroscopy

• Radiologists’ practices have evolved from approaches when they were trained

• Techniques have been modified in different ways in order to take account of changes in recommendations

Only screen for short periods

• Only screen for short periods

• Keep the image receptor close to the patient

• Keep the x-ray tube at maximal distance from patient

• Use higher kVp / lower dose options where possible

Collect data for mean results for a representative collection of hospitals

• Collect data for mean results for a representative collection of hospitals

• Ideally all major hospitals

• If not all, then a representative sample which might be 20-30 hospitals in a country

Calculate  use rounded 3rd Quartile value for DRL

• Calculate  use rounded 3rd Quartile value for DRL

DRL can then be used for comparisons by individual hospitals

• DRL can then be used for comparisons by individual hospitals

• Data collection

• Analyse, review and investigate

Investigation of intestinal tract

• Investigation of intestinal tract

• Involves imaging intestine following barium contrast through

• Additional images are recorded to visualise large intestine with higher quality

Pair of images, each showing the whole of the large intestine

• Pair of images, each showing the whole of the large intestine

• Taken with patient lying first on one side and then on the other

• Usually one AP and one PA

Mean KAP

• Mean KAP

• 15.4 Gy cm2

• KAP Range

• 4.4 – 30.4 Gy cm2

Investigation if mean value exceeds DRL

• Investigation if mean value exceeds DRL

• Highlights problems with equipment or technique (or training)

• Aids Optimisation

Equipment

• Equipment

• Dose performance

• Method of image recording

• Operator / procedure factors

• Screening or fluoroscopy time

• No. of images recorded

• Operators in training may give higher doses

• More skilled operators may take on a greater proportion of more complex investigations

Barium Enemas

• Barium Enemas

• Factor Median Quartiles Range

• Screening time 1.9 1.7-2.6 1.1-4.0

• Pulse fluoro rates 1-7.5 p/s

• Total no. of images 12.2 10.5-14.1 4.1-23.3

• Radiographs with second tube 2.1 2.0-3.0 0-5.3

Mean Fluoro KAP

• Mean Fluoro KAP

• 10.1 Gy cm2

Combination of:

• Combination of:

• Moving to lower dose rate option?

• Choosing low dose mA v kV options?

• Reducing fluoroscopy time?

Mean Total KAP

• Mean Total KAP

• 25.4 Gy cm2

• KAP Range

• 4.4 – 30.4 Gy cm2

Use of faster film / screen system?

• Use of faster film / screen system?

• Use of alternative imaging technique?

Hospitals used either 400 speed film/screen or CR

• Hospitals used either 400 speed film/screen or CR

• No link between CR and higher or lower doses

• No relationship to kV

• Two hospitals used C-arm

• units and recorded images

• with image intensifier

• C-arm systems were two of those with lower doses

• C-arm examinations quicker as the patient does not have

• to be moved

Digital equipment with low dose digital fluorography imaging

• Digital equipment with low dose digital fluorography imaging

• Incorporation of copper filters which reduce dose

Age of equipment

• Age of equipment

• Performance of image intensifier

Complex procedures with high doses

• Complex procedures with high doses

• Wide variation in complexity of procedures

• Other aspects are life threatening / life saving

• Radiation doses are high

• Skill and training of the operator is of overriding importance

Angiograms may include a variety of additional procedures on varying numbers of vessels – Typical descriptors

• Angiograms may include a variety of additional procedures on varying numbers of vessels – Typical descriptors

• Angiogram - Coronary

• Angiogram - Coronary & left ventriculogram

• Angiogram - Coronary & PTCA

• Angiogram – Coronary & stent

• Angiogram - Coronary & graft

• Angiogram - Coronary & PTCA & stent

• Angiogram - Radial Coronary

• Radio Frequency Abalation

Doses will depend on complexity of procedure and number of vessels investigated numbers of vessels

• Doses will depend on complexity of procedure and number of vessels investigated numbers of vessels

Review Means

• Review Means

• Calculate 3rd Quartile

Many other factors involved.

• Many other factors involved.

• Equipment – dose rates / options

• Numbers of images recorded

Collect 20 – 30 patient doses for each procedure

• Collect 20 – 30 patient doses for each procedure

• Restrict weight range if possible

• National Registry collates KAP data

• DRL set based on 3rd Quartile

• Comparison with DRL

• Many equipment and technique factors could be involved in higher doses