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ESTRO 36 2017
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In our regular outcome registration, we score acute
toxicity both by the RO and patient, whereas late toxicity
is mainly scored by the patient. For the PROMs we handout
validated – tumor group specific - questionnaires (QNRs)
at baseline. Subsequently we sent out the QNRs at 3 weeks
after the end of RT, 3, 6 and 12 months after RT, and
thereafter yearly until 5 years after RT. For the current
study we manually selected all QNRs scoring ≥ grade 3
symptoms on any item during 2 months. The selected QNRs
were sent to the responsible RO by e-mail. The RO
reported his/her subsequent actions: 1) Making a note in
the Electronic Patient File (EPF); 2) contacting the patient
to decide whether analysis and/or treatment of the
symptoms was required, or 3) no action. Finally, the RO
reported how much time the actions had taken. The type
of undertaken actions and the required time was analysed
per time-point of the QNR, and per tumor type.
Results
All received QNRs during the set period, in total 459, were
screened; in 137 (30%) ≥ grade 3 symptoms were reported
on any item, which varied between the tumor groups
(figure). In 20% of the cases, spread evenly (relatively)
between short term and later time points, the RO
undertook some additional action, which varied between
discussing the high score in regular follow-up contact with
the patient, to referring the patient to the GP, to making
a note in the EPF. 90 Out of the 137 (66%) QNRs concerned
symptoms between baseline to 3 months after RT; the
other 34% concerned late toxicity. The time used by the
RO to undertake action varied from 1 - 20 minutes, with
an average of 5,8 and a SD of 4 minutes.
Conclusion
We found that re-directing the patient-QNRs to the
responsible RO improved patient related quality of care,
since actions were taken based on information the RO
formerly did not acquire. However, the workload for the
RO can significantly be diminished by only re-directing
QNRs that are returned from 3 months after treatment,
since most patients have their follow-up in the referring
hospitals. Here PROMs have a substantial added value. The
next step is to have the DWH automatically send an alert
to the responsible RO.
Poster: Physics track: Basic dosimetry and phantom and
detector development
PO-0756 Characterizing tissue equivalent materials
used for an end-to-end QA phantom for MR-guided RT
A. Steinmann
1
, D. Followill
1
1
UT MD Anderson Cancer Center Radiation Physics,
Radiation Physics, Houston- TX, USA
Purpose or Objective
Tissue equivalent (TE) materials currently used to
simulate tumor and surround tissues for IROC-Houston’s
anthropomorphic head and thorax QA phantoms cannot be
visualized on MR. The purpose of this study was to
characterize “dual MR/CT compatible” TE materials that
can be used in an end-to-end QA phantom for MR guided
radiotherapy (MRgRT) modalities.
Material and Methods
Four materials were characterized for use as TE materials
in a QA phantom for MRgRT modalities and were examined
based on MR/CT visualization and dosimetric properties.
These materials included soft tissue, lung and two
potential
tumor
substitute
alternatives.
Materials were scanned on Siemens’ 1.5T using four
sequences, which showed the materials visual contrast
between T1 and T2 weighted images. Material’s
attenuation data were collected using GE’s CT Simulator.
Dosimetric properties were examined by constructing a
10x10x20 cm
3
PDD phantom that was divided into three
sections: anterior, middle, and posterior. Anterior and
posterior pieces were composed of polystyrene, whereas
the middle section was substituted with the testing
materials. EBT3 film was inserted into the phantom’s
midline and was irradiated using Elekta’s Versa 6 MV beam
with a prescription of 6 Gy at 1.5 cm and varying field size
of: 10x10 cm
2
, 6x6 cm
2
, and 3x3 cm
2
. Relative film
measurements were compared with a treatment plan.
Two mini-phantoms were constructed out of the four
previously studied materials that represented interfaces
between tumor/soft-tissue and tumor/lung. Theses
phantoms were fabricated into a 15x15x15 cm
3
cube,
where the center-most represented a tumor with
dimensions of 3x3x5 cm
3
. Two TLDS were inserted inside
the tumor and EBT3 was inserted in the sagittal plane.
With a prescription of 6 Gy at 1.5 cm, beam profiles were
collected with and without a magnetic field from a 1.5T
MR-Linac.
Results
The tested TE materials provided great contrasts amongst
T1 and T2 weighted images, additionally, they showed
attenuation comparable to their respective organ sites.
MR/CT compatible lung and soft TE materials had HUs of -
685, and 20, respectively, whereas the two potential
tumor alternatives showed HU values of -160 and 30.
PDD curves were compared with IROC-Houston’s
conventional lung and soft tissue substitutes. Soft
tissue/tumor equivalent materials show greater PDD curve
agreement than lung equivalent materials. While all PDDs
showed expected curve shapes, the smallest field size (3x3
cm
2
) showed a deviation of 11.9% and 4.6%, respectively
for
lung
and
soft
tissue
PDD
curves.
At B=0 and at 6.5cm in depth of the mini phantom, beam
profiles were extracted from the film and were corrected
and normalized to the TLDs. It is expected that beam
profiles will show similar beam profile results with a 1.5T
magnetic field.