Does MR imaging give us advantage in contouring thoracic structures for Cardiac SABR?
Fuertes, L. Dubec, Michael Anjanappa, M. Rodgers, John Hales, Rosie Clough, A. Aznar, Marianne Camille Choudhury, Ananya
Fuertes, L.
Dubec, Michael
Anjanappa, M.
Rodgers, John
Hales, Rosie
Clough, A.
Aznar, Marianne Camille
Choudhury, Ananya
Citations
Altmetric:
Abstract
Purpose or Objective
Cardiac magnetic resonance is the gold-standard imaging
technology for identifying scars, the most common cause
of ventricular tachycardia (VT) in patients with previous
history of myocardial infarction. Recent studies have
shown promising results for cardiac SABR ablation of
refractory VT. As MR-guided RT (e.g. as delivered on an
MR-linac) develops, daily full online replanning guided by
MR is becoming a reality. Here, we analyze differences between CT and MR contouring of thoracic structures
routinely contoured for cardiac SABR.
Material and Methods
We chose three patients from an institutional lung cancer
database. Each patient had a set of diagnostic MR images
(T1 with fat saturation, a sequence we can acquire with
the MR-linac), a planning CT and a CBCT. We ask five
observers (three radiographers and two clinicians) to
contour two thoracic structures (heart and esophagus) on
the three sets of images of the three patients (figure 1).
The volunteers used a five-point visual grading scale (1 =
very unconfident, 2 = unconfident; 3 = confident with
reservations, 4 = confident, 5 = very confident) to indicate
their confidence when contouring Results
The mean confidence for the heart contours (n=15) in the
MR, planning CT and CBCT images was 4.33±0.49,
4.27±0.59 and 2,33±0.46, respectively, and for the
esophagus contours (n=15) was 4.07±0.8, 3.8±0.68 and
1.33±0.49, respectively. The grade of confidence in
contouring heart and esophagus was significatively higher
with MR than with CBCT (p<0.01 in both cases). No statistically significant differences were observed
between MR and planning CT contours.
Conclusion
These results highlight the limitation of CBCT images for
daily online replanning in thoracic tumours. Though our
results need to be validated with on-board MR-images,
they suggest that there could be clear advantages to using
daily MR-guided radiotherapy for cardiac SABR, where
precise delivery of radiotherapy would result in optimal
dose whilst minimising risk of complications. Further
investigation is needed to determine the best MR
sequences required for daily MR-based adaptive replanning
for cardiac SABR.
Description
Date
2020
Publisher
Collections
Keywords
Type
Meetings and Proceedings
Citation
Fuertes L, Dubec M, Anjanappa M, Rodgers J, Hales R, Clough A, et al. PO-1020: Does MR imaging give us advantage in contouring thoracic structures for Cardiac SABR? Radiotherapy and Oncology . 2020 Nov;152:S544–5.