Manaaki Tangata Taiao Hokiprotecting people and their environment through science

Specialist Science Solutions

HEAPHY 1 & 2PLENARY

Tony COTTERILL

Fri 30th Aug 2013Session 3 / Talk 4

14:30 – 14:50

ABSTRACTThis presentation will be in two parts:Under the Radiation Protection Act 1965 practitioners require a license to use irradiating apparatus and/or radioactive materials for medical imaging. Through a license condition licensees are required to report to the regulatory authority specified radiation incidents involving the exposure of patients.In diagnostic radiology notified radiation incidents are generally of low dose and consequently minimal risk. However, a significant proportion of notified incidents involve computerized tomography scans where patient doses are more significant. Also, on rare occasions incidents have included procedures involving the injection of patients with contrast media or radiopharmaceuticals. Causes of incidents include clerical errors, failure of staff to follow the so-called three-point check (e.g. name, date of birth and address), and referral errors such as the mislabeling of a request form.This presentation will give a summary of reported incidents in diagnostic radiology between July 2009 and the end of November 2011.The National Radiation Laboratory (NRL) has surveyed the use of conventional plain radiography in New Zealand since 1983. Since NRL's last supplemental survey in 1992 there have been improvements in technology, particularly with the widespread transition from film to digital imaging indicating the need for a new survey. The most recent survey was carried out by NRL in 2010 and involved collecting data nationally. This presentation reports the findings for this latest survey and presents national diagnostic reference levels

Manaaki Tangata Taiao Hokiprotecting people and their environment through science

Specialist Science Solutions

Diagnostic Radiology: 1/ A Summary Of Reported Radiation Incidents2/ The Results of a National Survey Of Patient Doses In Conventional Plain Film Radiography

Tony Cotterill, Glenn StirlingNational Centre for Radiation Science

(formally the National Radiation Laboratory)

© ESR 2012

ESR - a Crown Research Institute

• Established July 1992

• Government owned

• One of eight CRIs

• Covered by CRI Act (1992)

© ESR 2012

NCRS (formally NRL) provision of services• National training centre

- RPS course - RPO course (non-medical)- Regulatory Core of Knowledge- Bespoke training courses

• Radiation Protection Advisor (RPA) - corporate RPA- senior medical/health physicist as the

portfolio manager- simplicity of a single contract for the provision

of all required radiation protection advice and services

- comprehensive and flexible and cost effective

© ESR 2012

Incident reporting• To Ministry of Health’s ORS• A radiation incident involving the exposure of a patient to a

radiation dose much greater than intended

- ‘much greater than intended’ guideline multiplying factors - high dose eg, CT 2- medium dose eg, AP abdomen 10- low dose eg, chest 20

• A radiation exposure of a patient where none was intended, as in the case of mistaken identity

• A radiation exposure of the embryo/foetus where the exposure had not been included in the justification process

• An unexpected skin injury to a patient resulting from a prolonged radiation exposure in an interventional procedure

Tony Cotteril 5

© ESR 2012

Reported main cause of incidents:July 2009 to December 2011

Tony Cotteril 6

Equipment failure Inadequate procedures Human error Clerial error Referrer error Other0

10

20

30

40

50

60

70

No.

of I

ncid

ents

171 reported~ 6 per month63 major centres

© ESR 2012

Analysis of causes (1)Cause Additional details provided on causes Corrective and preventive

actions taken by radiology departments

Equipment failure.

These include: Patients administered radiopharmaceuticals just

prior to imaging equipment failure. Servicing error on fluoroscopy unit. CR cassette failure. Image storage computer failure. Image processor failure.

Limited possible actions as faults were unpredictable.

Inadequate procedures.

Hand-over issues when main ordering system that had been down was restored.

Hand-over issues between ED and Radiology. Incorrect patient identification. Accidental CR cassette erasure. Inadequate training of staff on x-ray equipment.

Process review and staff training.

Human error. Most involved misidentification of the patient.  

Process review and staff training. More consistent application of the

three-point check.

Tony Cotteril 7

© ESR 2012

Analysis of causes (2)Clerical error. Referral incorrectly entered on to RIS.

CT images accidentally deleted. NM images accidentally corrupted while

attempting amendment. Incorrectly booked for an x-ray when only a US

had been requested. Misinterpreted ambiguous exam coding. Patient previously administered with

radiopharmaceutical, mistakenly turned away when returned for scan.

 

Process review and staff training. Computerised referral systems. Computerised post-processing of

images. 

Referrer error. Most involved referral forms with inaccurately completed clinical details (eg, forms where the incorrect pre-printed patient’s details label had been inadvertently attached), or duplicate requests.

Checking of clinical details with patients when presenting.

Computerised referral systems. 

Other. Mostly due to patients not knowing that they were pregnant. 

Staff training. Consideration of the use of

pregnancy tests for the high dose abdominal CT procedures.

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© ESR 2012

Incidents involving: July 2009 to December 2011

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Pregnant patient Skin injury Wrong Patient Other0

20

40

60

80

100

120

No.

of I

ncid

ents

© ESR 2012

Modalities of incidents; July 2009 to December 2011

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Nuclear Medicine CT Fluoroscopy Plain Radiography0

20

40

60

80

100

120

No.

of I

ncid

ents

© ESR 2012

Patient dose of incidents; July 2009 to December 2011

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<1 1 to 10 >100

10

20

30

40

50

60

70

80

90

Effective dose (mSv)

No.

of I

ncid

ents

© ESR 2012

2/ Results of a National Survey Of Patient Doses In Conventional Plain Film Radiography

Tony Cotteril 12

© ESR 2012

Number of conventional radiographyprocedures (excluding theatre mobiles)

• ~ 13% increase per capita• an average a person will be x-rayed once every

two years• Approximately 90% digital

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 Year

1983-84 2010

Population (millions) 3.22 4.23

Number of x-rays per year 1.5 million 2.2 million

Number of x-rays per 1000 of population

470 530

© ESR 2012

Numbers of conventional radiographyprocedures for different age groups

• Marked increase in the number x-rays of older adults with less paediatric x-rays

• Demographics (eg, ageing population) alone doesnot account for this shift.

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0

50

100

150

200

250

300

350

400

450

0-<1 1-4 5-9 10-14 15-19 20-24 25-29 30-39 40-49 50-59 >-59

Age group (years)

Patie

nts

per 1

000

x-ra

ys

1983-84 survey2010 survey

© ESR 2012

Relative frequency of the main types ofconventional radiography procedures

• The contribution of conventional plain radiography procedures to the diagnostic radiology population dose per capita has dropped (243 to 99 µSv per capita per annum)

This is probably because of a shift of higher dose procedures to other modalities such as CT

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Type Year1983-84 (%) 2010 (%)

Limbs & extremities 31 33Pelvic region, lumbo-sacral spine 12 25

Chest, heart, lungs 35 22Ribs & sternum, thoracic spine, shoulder girdle

5 10

Head, neck 10 7Abdominal soft tissue 7 3

© ESR 2012

U.S. population exposure 2006

National Council on Radiation Protection and Measurement. Report No. 160.

62 million CT examinations

~ 6 mSv per person

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© ESR 2012

Diagnostic Reference Levels (DRL) in termsof ESD (mGy) compared with other studies

• Little change in DRL

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Projection(70 kg patient)

British Institute of Radiology (UK) (1986)

(Current values in

CSP5)

HPA (UK) (2005)

AAPM (USA) (2005)

This survey (NZ)

(2010)

Chest PA 0.3 0.2 0.3 0.3Chest LAT 1.5 0.6 - 1.1

Lumbar spine AP 10 5 7 7

Lumbar spine LAT 30 11 - 27

Pelvis AP 10 4 - 5Abdomen AP 10 4 6 7

© ESR 2012

Conclusions

• There has been a small increase in the number of conventional plain radiography procedures being performed compared to 1983/84

• The age distribution of patients undergoing conventional plain radiography procedures, since NRL’s survey in 1983-84, shows a marked increase in the x-raying of older adults withless paediatric x-rays. Demographics alone do not account for this shift

• The contribution of conventional plain radiography procedures to the diagnostic radiology population dose per capita has dropped. This is because of a shift of procedures to modalities such as CT.

• Little change in the DRL

Tony Cotteril 18

© ESR 2012