ESTRO 36 Abstract Book

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S81 ESTRO 36 2017
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R. Bakker1, M. Jeulink1 , S. Tetar1, S. Senan1, B. Slotman1,
F. Lagerwaard1, A. Bruynzeel1
1 VU University Medical Center, Radiotherapy,
Amsterdam, The Netherlands
Purpose or Objective
Recently, SMART has been introduced in our center using
the MRIdian (Viewray). One key feature of SMART is
delivery of radiation while patients are positioned for a
prolonged period within the MRI bore, and therefore may
experience procedure-related problems such as anxiety,
noise and other MR-related undesired signals. Briefly,
patients are positioned on the MRIdian with body coils and
headphones, after which 0.35T MR-scans are performed
prior to each fraction. After alignment of the target
volume and re-contouring, re-optimization of the original
treatment plan and patient-specific QA is performed while
patient remains in treatment position. Treatment is
delivered under real-time MR-guidance, with or without
breath-hold, depending on location. On average, the
duration of a single fraction ranges from 45 minutes
(prostate SBRT) up to 75 minutes (breath-hold pancreas
SBRT). To gain insight into patient tolerance and
experiences of SMART delivery, we prospectively collected
patient-reported outcome questionnaires (PRO-Q) in
treated patients since May 2016.
Material and Methods
The intake visit of SMART patients includes providing
procedural information by the radiation oncologist, and in
case of video-feedback for breath-hold, also by
dosimetrists. During the same visit, a MRI-safety
questionnaire is completed. Immediately after the intake,
a simulation MR-scan is performed on the MRIdian. PRO-Q
were collected in 55 patients after the last SMART
fraction. The PRO-Q includes questions on anxiety,
temperature, noise, and other potential MR-related
undesired signals. It also includes a question on the
tolerance of the duration of the SMART procedure. Items
could be scored as: 1) 'not at all”, 2) 'a bit” 3) 'moderate”
and 4) 'considerable”.
Results
Two of 57 patients withdrew from SMART because of
severe claustrophobia during the simulation MRI.
Furthermore, anxiety during treatment was reported by
12/55 patients (22%), with half of these reporting anxiety
to be considerable. A majority of patients (52%) reported
sensations of feeling cold related to the cooling air flow of
the MRIdian. Although the MRIdian combines noise of the
gradient coils of the MR and retraction of the radiation
sources, this sound was experienced to be really disturbing
by two patients only. Troublesome paresthesia was
reported by two patients, mainly related to prolonged
positioning of the arms above the head. Other relevant
MR-related undesired signals such as dizziness, local heat
sensations or metallic taste sensations were only
occasionally reported. Although the total fraction
duration was judged to be long by some extent in 22% of
patients, only a single patient scored this as being
unacceptably long (Fig.1).
Conclusion
Despite standardized information and performing
simulation on the treatment machine, anxiety remains an
item that needs specific attention. Even with fraction
duration times of up to 75 minutes, only a single patient
perceived this as being unacceptably long.
OC-0162 Optimizing sequences for MRI-guided
radiotherapy in cranial and head and neck regions
W.W.K. Fung1, S.Y. Man1, J. Yuan 2, L.H. FUNG2, W.P.
LUK 2, G. Chiu1
1Hong Kong Sanatorium & Hospital, Department of
Radiotherapy, Happy Valley, Hong Kong SAR China
2Hong Kong Sanatorium & Hospital, Medical Physics &
Research Department, Happy Valley, Hong Kong SAR
China
Purpose or Objective
MR sequences using parallel acquisition technique (PAT)
with increasing acceleration factors could reduce the scan
time for treatment verification, but with the cost of losing
image quality that could affect verification accuracy. This
study assessed the effect of different PAT factors on image
quality, scan time and fusion accuracy, thus choosing a
sequence which is clinically suitable for MRI-guided RT in
cranial (C) and HN regions.
Material and Methods
Ten healthy volunteers were set up in treatment position
using headrest and immobilization mask on the flat couch
of a 1.5T MRI-simulator (Siemens MAGNETOM Aera). High
resolution isotropic (1.05mm) 3D TSE T1W and T2W MR
sequences were acquired (MR-ref). Based on MR-ref, 11
low-resolution (isotropic 1.4mm) verification sequences
(MR-Pxys) were acquired with GRAPPA where acceleration
factors x and y were altered in respectively phase
encoding and slice encoding directions. Effective PAT
factor (PAT-f) equals x times y. Four therapists (2 seniors
& 2 juniors) performed two sets of fusions: MR-ref & MR-
Pxy s and MR-ref & duplicated MR-ref (control set) for C and
HN region. Shift results (6DOF) were recorded. Survey was
given to observers for scoring the image quality. Logistic
and linear regression were used.
Results
The scan time for MR-ref were 301s and 330s, and for MR-
Pxy s it ranged from 249s to 49s and 254s to 59s for T1W and
T2W images respectively when PAT-f increased from 3
(MR-P31) to 16 (MR-P 44). Subjective analysis showed that
the scores of all verification series were lower than the
reference and decreased with increasing PAT-f. Image
quality decreased when reducing the scan time (Fig.1).
Significant reduction of image quality (p<0.05) occurred
when PAT-f reached 12 for T1W and 6 for T2W images.
Observers favored T1W over T2W images (p<0.0001).
Scores from senior observers were significantly better
than juniors (p<0.0001).