ESTRO 36 Abstract Book

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S244 ESTRO 36
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effects of a potential problem and the prioritization of
actions that can reduce this dysfunction. Our Radiation
Therapy Department used the FMECA as a strategy tool to
continuously improve treatment quality and safety. This
FMECA approach was applied to our Cyberknife (CK)
workflow process.
Material and Methods
Using the FMECA methodology, the CK workflow process
was defined with a flow chart and responsibility map
including a description of every step of prescription,
treatment preparation and treatment delivery. The
identification of possible risks was then carried out with
their origins and consequences. The evaluation was based
on 3 criteria: Severity (S), frequency of Occurrence (O)
and probability of Detection (D). Finally, we calculated
the Criticality Index (CI = S x O x D) for each of the
identified risks. The rating for each criterion is based on a
scale from 1 to 4. The Criticality Index can span a range
of 1 to 64.
Results
We defined 10 stages, with corresponding failure modes
presented in a table. At each stage, identified failures
with possible causes and consequences are listed and the
risk level assessed. A detailed scoreboard was obtained
presenting the risks and enabling easier identification of
priority actions to be undertaken. The board showed 66
possible failure modes. 8 of the top-ranked failure modes
were considered for process improvements. We also
crossed the scoreboard obtained with the adverse events
most often reported on 2015. We found 2 correspondences
between failure modes and adverse events reported. We
therefore also considered that in the implementation of
preventive/improvement actions to take. A review of this
analysis was done in September 2016. Therefore, at this
moment, a revaluation of the process, failures, ratings and
implemented actions was performed with each members
of the CK team. The correlation with reported adverse
events was also made. We had one failure mode that has
to be changed from a moderate to an unacceptable level
because an incident was reported following a non-update
procedure. New improvement actions have been
implemented directly. In order to continue our proactive
approach to risk analysis a systematic annual review of this
analysis is now introduced in routine. All this, in relation
to the reported adverse events. The figure shows an
extract of the FMECA scoreboard obtained for CT
simulation and contouring stage.
Conclusion
The analysis of the potential failures, their causes and
effects allowed us to increase the quality and the safety
in the CK workflow process. The FMECA technique provides
a systematic method to target vulnerabilities before they
generate an error. This framework analysis can naturally
incorporate further quantification and monitoring. The
FMECA method is an effective tool for the management of
risks in patient care.
PV-0459 Prostate CBCT dose optimization : from an
iterative mAs reduction to a sytematic exposure
reduction
E. Jaegle1, M.E. Alayrach 1, A. Badey 1, V. Bodez 1, C.
Khamphan1, P. Martinez1, R. Garcia1
1Institut Sainte Catherine, Physique, Avig non, France
Purpose or Objective
A daily repositioning Cone Beam Computed Tomography
image (CBCT) for prostate radiotherapy is realized using
exposure templates (mAs, kV) which affect image quality
and imaging dose. Settings should be optimized to
minimize patient exposure while maintaining sufficient
image quality to register the initial planning CT with CBCT
using soft tissue matching.
Material and Methods
20 prostate patients (without hip prosthesis) with daily
CBCT (40 fractions) acquired on a TrueBeam™ (Varian
Medical Systems) machine were selected. After the first
fraction using the standard pelvis template (125 kV 1080
mAs CTDIw 14 mGy), the therapists manually applied, day
after day, a low mAs reduction and assessed if the CBCT
image quality was good enough for patient repositioning.
The iterative process stopped when image quality was
assessed too bad and the last proper mAs were selected.
The link between the mAs reduction and corpulence
(patient volume inside CBCT FOV) was studied.
For one example patient, 23 therapists registered CBCT
images with CT for 3 fractions : the first fraction (S0% ), a
fraction with 50% mAs reduction (S-50% ) and the fraction
with maximum mAs reduction (S -71%).
Fisher’s test was applied to every direction, to compare
the variance between S0% / S -50% and S0% / S-71% .