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:EquipmentOperator techniquePatient factors

Collection of KAP data

Collection of KAP data for recent survey from one hospital

Distribution for 120 patient barium enema exams

Patient related factorsExtent and severity of diseaseCondition of patientPatient size

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

Data collection

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

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 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

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 periodsKeep the image receptor close to the

patientKeep the x-ray tube at maximal

distance from patientUse higher kVp / lower dose options

where possible

Hospital SurveysDate Exam Patient

weight (kg)

Operator / Clinician

KAP (cGy cm2)

Screening time (s)

9/2/13 Barium enema 76 Dr A 1699 45

9/2/13 Barium enema 90 Dr B 1201 41

9/2/13 Barium enema 68 Dr B 890 23

9/2/13 Barium enema 85 Dr A 2394 93

9/2/13 Barium enema 70 Dr A 2109 72

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 20-30 hospitals in a country

Summary of Barium Enema Data

Calculate use rounded 3rd Quartile value for DRL

3rd Quartile

Suggested DRL 1600 cGy cm2

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 throughAdditional 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 cm2

KAP Range 4.4 – 30.4 Gy cm2

0

5

10

15

20

25

30

35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Hospital

Mea

n D

AP

(Gy

cm2)

Mean DAP - Decubitus

Mean DAP - Undercouch tube

Mean KAP for 20-50 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 EnemasFactor Median Quartiles RangeScreening time 1.9 1.7-2.6 1.1-4.0Pulse fluoro rates 1-7.5 p/sTotal no. of images 12.2 10.5-14.1 4.1-

23.3Radiographs with

second tube 2.1 2.0-3.0 0-5.3

Large rangesLarge ranges

Survey of Barium Enema Doses in West of Scotland – 20 hospitals

Mean Fluoro KAP 10.1 Gy cm20

5

10

15

20

25

30

35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Hospital

Mea

n D

AP

(Gy

cm2)

Mean DAP - Decubitus

Mean DAP - Undercouch tubeMean KAP for 20-50 patients at each hospital

DRL 25 Gy cm2

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 cm2

KAP Range 4.4 – 30.4 Gy cm2

0

5

10

15

20

25

30

35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Hospital

Mea

n D

AP

(Gy

cm2)

Mean DAP - Decubitus

Mean DAP - Undercouch tube

Mean Decubitus KAP (orange) 5.3 Gy cm2

KAP Range 1.3 – 10.5 Gy cm2

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

0

5

10

15

20

25

30

35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Hospital

Me

an

DA

P p

er

ex

am

(G

y c

m2

))

Yellow Units with copper filter

Another factor

Age of equipmentPerformance of image intensifier

Mean KAPs for barium examinations Equipment age and copper filtration are important factors

0

5

10

15

20

25

30

35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Hospital

Me

an

DA

P p

er

ex

am

(G

y c

m2

))

Yellow Units with copper filter

Brown Units over 8 years old

Interventional Cardiology and Radiology

Complex procedures with high dosesWide variation in complexity of

proceduresOther aspects are life threatening / life

savingRadiation doses are highSkill and training of the operator is of

overriding importance

Interventional CardiologyAngiograms 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 CardiologyDoses will depend on complexity of

procedure and number of vessels investigated numbers of vessels

Coronary Angiogram DRL

Review MeansCalculate 3rd Quartile

3rd Quartile

Suggested DRL 2500 cGy cm2

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 3rd Quartile Comparison with DRL Many equipment and technique factors could

be involved in higher doses