ESTRO 36 Abstract Book

ESTRO 36 2017

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which a more thorough investigation is probably needed.

For the high contrast detection task, the FOM used for this

task (d’ of a NPWE model) yields results that are way too

sensitive to the NPS, and work on improving the FOM is

currently being performed.

Conclusion

The use of a model observer for objective and clinical

task-based metrics might tackle the current problems

encountered with iterative CT image reconstruction, for

which the classical physical metrics are less pertinent.

However, tuning model observer performance in order to

estimate human observer performance remains

cumbersome, in particular because it relies on the

introduction of internal noise mimicking human

uncertainty in decision taking. One improvement would be

the use of Gabor channels (rather than DDoG), which are

even more anthropomorphic. The CHO model showed that

the majority of units assessed using this method

performed reasonably well when searching focal liver

lesions. However, the limited spread in objective image

quality was associated with a large spread in the chosen

dose indicator. On the other hand, high contrast detection

still suffers from conceptual flaws that will have to be

improved. Ultimately, the goal is to set up an open web

server where users could upload their images, the CHO or

NPWE calculation being performed online, for immediate

objective image quality assessment and thus continuous

immediate dose optimisation.

SP-0024 The potential of new CT technologies for

radiotherapy with photons and protons

W. Van Elmpt

MAASTRO Clinic, Department of Radiation Oncology,

Maastricht, The Netherlands

Computed tomography (CT) imaging is a the core of the

radiotherapy process: diagnosis, delineation, treatment

planning and follow-up imaging. New CT techniques are

introduced at many radiology departments such as Dual

Energy CT (DECT) scanners, iterative CT reconstructions

and automated selection of tube potential and imaging

dose. These techniques are also finding their way towards

radiotherapy departments. In this presentation a focus

will be on the developments in CT imaging that have an

application for radiotherapy purposes. To improve

delineation accuracy, mono-energetic reconstructions

from DECT imaging are being investigated, metal artifact

reduction techniques are employed to reduce scatter from

metal implants and iterative reconstruction improve

image quality that could allow better contouring. For dose

calculation in treatment planning, various options are

becoming available that reconstruct electron or mass

density images directly from the CT scanner or reduce the

uncertainty in stopping power ratios (SPR) for proton

therapy dose calculations by using DECT imaging.

Symposium: High tech or low tech for metastatic

disease, how does one decide and what is the cost-

benefit?

SP-0025 High tech approaches for curative treatment,

when is enough enough?

J. Kazmierska

Greater Poland Cancer Centre, Radiotherapy Dept,

Poznan, Poland

The idea to cure metastatic disease using local ablative

treatment is compelling, especially in an era of fast

technological progress in imaging and radiotherapy

allowing for delivering high radiation doses with high

precision. However, there are still important open

questions regarding the rationale for such treatment,

integration with systemic treatment and toxicity. Results

of ablative treatment of metastatic disease are

encouraging but variable so far, due to heterogeneity of

patients’ group, lack of clear differentiation between

oligometastatic and disseminated disease and different

endpoints of studies: from overall survival to stabilization

of the disease. Nevertheless, SBRT is now accepted,

valuable solution for these patients, despite its limitation.

Yet still there is a need to define, factors that will help

clinicians to keep the balance between the benefit for

patients and overtreatment. Finding biomarkers, patient,

disease and technology related parameters would be of

value for decision-making process and selection those who

benefit most from ablative treatment.

SP-0026 Optimizing the workflow of palliative

treatment using Lean Six Sigma methodology

M. Kamphuis

Academic Medical Center, Department of Radiation

Therapy, Amsterdam, The Netherlands

Introduction

Palliative radiotherapy for painful bony metastases is

mostly performed with a simple one or two field treatment

technique. Nowadays this procedure is performed based

on CT-images and is often time consuming. At the AMC in

Amsterdam the procedure is during working hours

organized in a so called “one stop shop” (OSS). This means

that patients are seen by the radiation oncologist,

simulated and being treated in one day. The processing

time (PT) of the whole procedure is 4:30 hours on average,

but in about 15 % of the cases more than 6 hours is

necessary. The PT was considered undesirable, especially

since patients are often in a poor condition. The aim of

this study was to decrease the average length of the

procedure by at least two hours.

Methods

Lean Six Sigma methodology was used to improve the OSS

protocol. First, a baseline time measurement was

performed in 30 patients to quantify the performance of

the different steps of the procedure. At the same time

factors influencing the length of the procedure were

registered (e.g. the treatment techniques used, the

number of RTTs involved and the number of sites being

treated). Patients were asked to fill in a form measuring

the perceived quality of the OSS.

A multidisciplinary working group created an extensive list

of influencing factors. Different techniques like Failure

Mode and Effect Analysis were used. Most important

influencing factors were identified e.g. using statistical

analyses on the baseline time measurement. Based on

these insights, the process was of the One Stop Shop was

redesigned. The redesigned process was tested in a pilot

study.

Results

In the baseline measurement, the PT ranged from 2:16h to

7:00h. In the analysis of influencing factors, the vital few

could be identified: number of RTTs involved in the whole

procedure, the use of a treatment planning instead of a

manual calculation, as well as the fact that patients were

scheduled of a fixed time slot on the treatment machine.

Different important factors, not foreseen at forehand,

could be identified using the methodology.

The redesigned process consisted of a small team existing

of two RTTs and one or two MDs performing the OSS. Team

composition was determined the day before the OSS

procedure, taking educational level and experience into

account. This team was responsible for the whole process.

The fixed time slot on the treatment was abolished,

patients were being treated as soon as the preparations

were finished and space was available on the treatment

machine. Results of the pilot study will be presented

during the conference.

Conclusion

Lean Six Sigma methodology provided the

tools to quantify, analyze and re-optimize the One Stop

Shop procedure. Furthermore, the methodology provided