Dose Audit in Fluoroscopy Colin Martin and David Sutton

Surveys of fluoroscopy 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

Fluoroscopy procedure doses The range in doses from fluoroscopy procedures is much larger than for radiography Influenced by:  Equipment  Operator technique  Patient factors

Collection of KAP data  Collection of KAP data for recent survey from one hospital  Distribution for 120 patient barium enema exams

Patient related factors  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

Data collection Collect data for 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

Methods of data collection 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

Method Collect data for 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

Radiological technique  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

Some general rules for improving patient protection  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

Hospital Surveys DateExamPatient weight (kg) Operator / Clinician KAP (cGy cm 2 ) Screening time (s) 9/2/13Barium enema76Dr A /2/13Barium enema90Dr B /2/13Barium enema68Dr B /2/13Barium enema85Dr A /2/13Barium enema70Dr A Calculate mean results for 30 patients for each hospital to submit to National Registry

Collation of hospital data  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 hospitals in a country

Summary of Barium Enema Data Calculate  use rounded 3 rd Quartile value for DRL 3 rd Quartile Suggested DRL 1600 cGy cm 2 Mean KAPs for each hospital

Local comparisons with DRL  DRL can then be used for comparisons by individual hospitals  Data collection  Analyse, review and investigate

Barium enema  Investigation of intestinal tract  Involves imaging intestine following barium contrast through  Additional images are recorded to visualise large intestine with higher quality

Decubitus films in barium enemas  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

Survey of Barium Enema Doses in West of Scotland – 20 hospitals Mean KAP 15.4 Gy cm 2 KAP Range 4.4 – 30.4 Gy cm 2 Mean KAP for patients at each hospital

Use of DRLs  Investigation if mean value exceeds DRL  Highlights problems with equipment or technique (or training)  Aids Optimisation

Equipment and operator factors influencing dose 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

Radiological technique – the data  Barium Enemas FactorMedian Quartiles Range Screening time Pulse fluoro rates p/s Total no. of images Radiographs with second tube Large ranges

Survey of Barium Enema Doses in West of Scotland – 20 hospitals Mean Fluoro KAP 10.1 Gy cm 2 Mean KAP for patients at each hospital DRL 25 Gy cm 2 Higher doses from fluoroscopy

Optimisation of fluoroscopy component Combination of:  Moving to lower dose rate option?  Choosing low dose mA v kV options?  Reducing fluoroscopy time?

Survey of Barium Enema Doses in West of Scotland – 20 hospitals Mean Total KAP 25.4 Gy cm 2 KAP Range 4.4 – 30.4 Gy cm 2 Mean Decubitus KAP (orange) 5.3 Gy cm 2 KAP Range 1.3 – 10.5 Gy cm 2 Higher Decubitus doses

Optimisation of Decubitus component  Use of faster film / screen system?  Use of alternative imaging technique?

Decubitus films in barium enemas  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

Factors contributing to lower dose examinations  Digital equipment with low dose digital fluorography imaging  Incorporation of copper filters which reduce dose

Mean KAPs for barium enemas Copper filtration has a significant influence Yellow Units with copper filter

Another factor  Age of equipment  Performance of image intensifier

Mean KAPs for barium examinations Equipment age and copper filtration are important factors Yellow Units with copper filter Brown Units over 8 years old

Interventional Cardiology and Radiology  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

Interventional Cardiology 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

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

Coronary Angiogram DRL  Review Means  Calculate 3 rd Quartile 3 rd Quartile Suggested DRL 2500 cGy cm 2

Can we use screening time as a dose metric?

Correlation between KAP and screening time (7 hospitals) Many other factors involved.  Equipment – dose rates / options  Numbers of images recorded

Screening time - DRL Dose is a much better variable to use than screening time However, if there is no KAP meter available it will give an indication of practice It can be useful

Conclusions  Collect 20 – 30 patient doses for each procedure  Restrict weight range if possible  National Registry collates KAP data  DRL set based on 3 rd Quartile  Comparison with DRL  Many equipment and technique factors could be involved in higher doses