Practical Application of
Suspension Criteria Scenarios:
General Radiology and
Fluoroscopy
U O’Connor, A Gallagher, JF Malone
Department of Medical Physics and Bioengineering, St.
James’s Hospital / Trinity College Dublin, Ireland.
Introduction

Revised EC RP-162 specifies minimum standards

Criteria of Acceptability / Suspension Levels

Radiology equipment should be assessed against these
standards


prior to its first clinical use

and regularly throughout its lifetime.
Equipment that does not meet the criteria must be removed
from use… however…
Role of the MPE

May be possible to return equipment to some limited form of
use based on

risk assessment by Medical Physics Expert (MPE)

in conjunction with practitioner

Decisions to suspend equipment will clearly have
consequences for patient access.

May place a financial burden on the institution in terms of
equipment repair or replacement.
Equipment assessed against
criteria of acceptability
Pass
Equipment
returned to
clinical use
Fail
Limit
on
Use
Risk Assessment
by MPE / RPA
Fail
Repair
or
replace
Written recommendation
to suspend equipment
Practitioner
“Half of 13 new systems that
were being commissioned
were defective”
Age is just a number…
…. Just another factor in your decision-making
Overview of Authors


Medical Physics & Bioengineering Dept., St. James’s
Hospital

responsible for commissioning, QA & radiation advice

asset base >100 general X-ray and fluoroscopy systems
Typical arrangement (in Ireland)

assessment carried out by MPE / Radiation Protection
Adviser (RPA) or delegate

decisions signed off by the RPA

MPE role becoming established. Many functioning as MPE.

RPA register well established - formally appointed named
person.
Case 1: General Radiology

Radiographer’s QC testing of
General radiology system at busy
regional hospital

Film/screen image receptor

Non-uniform optical density on all
films taken with vertical bucky.

Noticeable on clinical images.

Radiographer contacted MPE for
advice.

Not evident at previous QA (<3
months)
Case 1: General Radiology

Results exceeded the suspension level from RP-162

Also exceeded levels from RP-91 (1997)
Parameter
Suspension level
Film-Screen contact
Non-uniform density or loss of
sharpness
Visual Check of
Uniformity
Artefacts apparent
Case 1: Risk Assessment

MPE liaised with Radiologist who agreed that non-uniformity
was affecting clinical image quality.

Equipment suppliers: Issue could not be rectified due to age
(25 yrs) of equipment and lack of spare parts.

Other considerations


no AEC – not on a par with modern systems

equipment replacement programme advised previously in
QA reports.
RPA made recommendation (in writing) to the holder

Equipment must be replaced immediately.
Case 1: Limits on Use


Pending replacement of the equipment, Consultant Radiologist
had to advise on scope of practice if vertical bucky was
required clinically.
E.g. Radiologist may consider small field extremity images to
be acceptable if non-uniformity across width of bucky is not
clinically significant.
Case 2: Mobile Radiography




Annual QA testing of General radiology mobile
CR image receptor
MPE identified significant cut-off when measuring the X-ray
field to light field alignment.
Results exceeded suspension level from RP-162 & RP-91
Parameter
X-ray / light
beam
alignment
Setup
1m SID
7cm x 9cm
Result
6% or 6cm
Suspension level
Misalignment in
principle directions
> 3% of focusimage receptor
distance (SID)
Case 2: Risk Assessment




Equipment suppliers: X-ray tube
insert had moved in cathode
direction within tube housing.
Result was image cut-off on anode
side of X-ray system.
MPE carried out a risk assessment
on the unit
Taking into consideration
 no other mobile X-ray system in the Hospital
 mobile required for emergency and ICU exposures
 workload is low & new mobile due in 2 weeks time
 cut-off was less pronounced at clinical setup
Case 2: Limits on Use


RPA advised that mobile X-ray system may be used in
limited circumstances until delivery of new unit in 14 days.

only where absolutely necessary

and at SID of at least 1.8m.
Also advised that alignment must be
checked by radiography staff on a daily
basis to monitor for deterioration

Greater potential for further damage
on mechanical movement
Case 3: DDR AEC



Commissioning of two new General Radiology systems
DDR detectors - identical systems from same supplier
State-of-the-art installations into new Radiology department at
large Irish hospital.
IPEM ASM, 2008
Case 3: DDR AEC




Dose to detector in AEC mode for both systems was
measured to be 38 - 50µGy.
~900% greater than that achieved on other DR systems.
System had been released by suppliers having passed their
recommended tests.
“In the absence of tolerances… significant time liaising with
suppliers to rectify the problems”.
Case 3: Risk Assessment

System would pass RP-91 and IPEM but fail RP-162

MPE made a judgement on detector dose based on local
database from other DR systems.

Equipment engineers adjusted the dose following intense
consultation with MPE


supplier relying on factory settings with little consideration
for clinical setup

lack of understanding regarding what MPE was trying to
achieve.
Following adjustment and retest by MPE, detector dose still
remained higher than acceptable.
Case 3: Outcome

Further adjustment by service engineers.

Dose and image quality found to be acceptable.

Very interesting case which shows difficulty in assessing new
technology for which there is little established criteria.

Similar cases have occurred elsewhere with similar difficulties
and outcomes.

Highlights problem with establishing a reasonable baseline value
at commissioning and relying on that value for future testing.

Equipment supplier-specific training on requirements stemming
from criteria of acceptability would be of benefit.

Image Wisely - Image Gently
Case 4: Fluoroscopy



Annual QA testing of Fluoroscopy system.
II-TV system
8 years old
Parameter
Setup
Result
Suspension level
Air Kerma Rate
at Image
Receptor
1mm Cu
FF
Grid Out
2.6μGy/s
>1μGy/s
Patient
Entrance
Kerma Rate
20cm PMMA
FF
Grid In
18.4mGy/min
- more than
doubled since
previous QA
100mGy/min (RP-91*)
75mGy/min (draft RP-162*)
* 25cm phantom
Case 4: Image Quality


Overall image quality was poor
Failed to meet the criteria recommended in RP91, IPEM and
draft RP-162
Parameter
Setup
Result
Suspension level
Threshold
Contrast
Leeds N3
FF
5.5%
>4% for 3mm targets
Leeds Test Objects N3 – Example of
Good Low Contrast Resolution
Case 4: Risk Assessment

Service engineers were contacted as they had just
completed a routine service.

They noted that there were problems with the
system which were not yet resolved.

Highlights importance of communication between
service engineers, radiographers and physicists

Benefit from using a handover sheet post-service
UK MEDICAL-PHYSICS-ENGINEERING Mailbase July 2011
Case 4: Outcome

Image quality issues combined with obvious system
degradation.

Highlights importance of system performance tests such as
air-kerma at II entrance.

MPE advised that system should not be used until problems
addressed.

Verbal advice given on day of QA testing following
consultation with RPA.

Written memo sent to hospital management, consultant
radiologist and radiographer in charge.
Case 4: Outcome

Limits on Use:


Workload / clinical considerations


System could be operated in radiographic mode if required.
Large regional hospital with a second fluoroscopy system
available.
Hospital acknowledged the problems with system and it was
replaced.
Discussion

Application of suspension criteria in busy diagnostic imaging
facilities requires careful judgement

Decisions to remove equipment from clinical use are not
taken lightly.

In all cases presented here, the MPE carried out a risk
assessment based on


equipment faults

information from supplier

advice from RPA

and input from radiology staff on clinical needs
Where possible, the MPE will advise on continued use of
equipment in limited circumstances.
Note on Scope of RP-162


Authors have experienced numerous other issues which have
resulted in suspension of radiology equipment.
Mainly related to electrical safety, room shielding and
equipment design issues.

Outside scope of report RP-162

However form an important part of the overall assessment of a
diagnostic imaging facility.
Conclusion


Scenarios presented here show the challenges
involved in decision-making on radiological
equipment.
New report EC RP-162 aids the decision-making
process by expanding on EC RP-91 report (1997)
to include
 advice on CR / DDR
 additional criteria for existing technology such
as fluoroscopy.
 guidelines for new technologies for which
criteria are not defined and for implementation
of suspension procedures
Practical Application of
Suspension Criteria Scenarios:
General Radiology and
Fluoroscopy
U O’Connor, A Gallagher, JF Malone
Department of Medical Physics and Bioengineering, St.
James’s Hospital / Trinity College Dublin, Ireland.