Improving Patient Care
CT Dose Reduction through a Collaborative Approach
Mitch Griffith -Radiation Safety- Northern Health Authority
Ken Winnig -Regional Director Diagnostic Services- Northern Health Authority
The Need for Change
The use of Computerized Tomography (CT) in medical imaging has
risen dramatically over the past 3 decades with a 20 fold increase
in the number of scans done annually. In Canada there was a 31.8%
increase in the number of CT scans done between 2003 and 2006, this
coupled with the relatively high level of radiation involved, CT is now
the single greatest source of radiation exposure from medical imaging
Quantifying a link between exposure to “low” levels of radiation
and cancer has been a controversial subject however there are
some general principles that are emerging; the age at exposure to
and the amount of radiation exposure increases the probability of
cancer induction. For an individual patient undergoing a CT scan, the
probability of developing a cancer as a result of radiation exposure
is exceedingly low, when consideration is given to the large number
of scans done nationally, the probability of cancer induction becomes
Across Northern Health 28,000 CT procedures are performed annually
therefore it was concluded that any reduction in patient radiation
dose could have a statistically significant impact on the population as
Where to start
It was determined that Lumbar spine scans would be the procedure by
which the dose optimization (reduction) strategy would be developed
and implemented. Lumbar spine scans are a relatively common exam
type with a high degree of variability in patient dose across the health
authority; therefore significant gains might be realized through a
review of clinical and technical practices.
What we did
Bringing together a project of this scope required the collaborative
efforts of groups across the spectrum of the healthcare team and with
the endorsement of the Regional Director of Diagnostic Imaging and
Diagnostic Imaging Quality Assurance Committee (DIQAC) the work
How we did
In the months following the audit it was evident that radiation dose
awareness was increasing across the region as some sites began
to take an active role in dose optimization steps, regardless of
whether their average doses were above or below the established
DRL’s. Since dose optimization steps were underway in multiple
paths simultaneously we were unable to determine which pathway
contributed the most to the overall reductions realized.
As of December 2013 the results were as follows
Audit Period Avg DLP Regional DRL % reduction
2011 1381 1836 N/A N/A
2012 1199 1565 15 15
1075 1374 12.2 25.2
922 1181 14.1 35.7
A 35.7% reduction in the regional DRL was a remarkable achievement,
considering the scope of the project on so many fronts; numerous
radiologists, multiple sites spread across the health authority and the
wide range of groups involved in implementing the change.
The quality improvement for the patients of Northern Health is an
example of the positive outcomes that can be realized through a
Where are we going from here?
Radiation safety operates on the ALARA principle, (As Low As
Reasonably Achievable) so future reductions may be achievable
within this exam type however the diagnostic quality needs to be
maintained. Dose optimization has been carried over to other exam
categories however the process is ongoing, accurate data collection is
critical and translating the success of the Lumbar spine optimization is
proving to be challenging, however the work continues.
Mr. Mitch Griffith, Radiation Safety Officer
Initial audit 2010-2011.
Note the variability in patient radiation dose.
2012 Audit of patient dose was done following the development
of the automated RIS report. Internal reviews of imaging
protocols begun with DIQAC approved clinical changes adopted.
2013 January to June. Further protocol sharing and
ongoing site participation in adopting changes.
2013 July-December. Technological changes (dose
reduction software) implemented at 2 sites.
Figure 1 - DRL
Measure the outcomes.
Dose reduction would be managed
using the Diagnostic Reference
Level (DRL) concept. Patient data
was analyzed at a regional level
and the DRL calculated as the 75th
percentile of the distribution of
doses. Dose reduction strategies
would be implemented and follow
up audits performed, success would
be measured at the site level (lower
average dose/exam) and regionally
through a reduction of the DRL and
a left shift of the dose distribution
as demonstrated in Figure 1.
Through the efforts of our dedicated staff and
physicians, in partnership with communities and
organizations, we provide exceptional health
services for Northerners.
the northern way of caring