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present in the bladder during treatment, which effectively
blocks the microwave radiation used to warm the bladder.
This may lead to a lower thermal dose to the bladder wall,
which is associated with a lower treatment response. This
study investigates the size of that effect.
Material and Methods
We analysed thirteen NMIBC patients treated at our
institute with mitomycin C (40 mg in 50 ml) plus
hyperthermia (60 min). Hyperthermia was delivered using
our hyperthermia device with four 70 MHz antennas
around the pelvis. A CT scan was made after treatment
and a physician delineated the bladder on the CT scan. On
the same scan, the amount of air present in the bladder
was delineated. Using our in-house developed
hyperthermia treatment planning system, we simulated
the treatment using the clinically applied device settings.
We did this with the air pocket delineated on the CT scan,
and alternatively with the same volume filled with fluid
(urine).
Results
The patients had on average 4.2 ml (range 0.8 – 10.1 ml)
air in the bladder. The bladder volume delineated by the
physician (including air pocket and bladder wall), was on
average 253 ml (range 93 – 452 ml). The average bladder
volume in which changes exceeded 0.25 °C was 22 ml
(range 0 – 108 ml), with the bladder being up to 2 °C cooler
when an air pocket was present. There was no evident
relation between the quantity of air and the difference in
temperature. Although in particular the part of the
bladder close to the air pocket absorbs less energy, the
temperature in the entire bladder is typically lower
because of convective mixing in the bladder contents.
Conclusion
The effect of an air pocket in the bladder during bladder
hyperthermia treatment varies strongly between patients,
and no relation was visible between effect size and air
volume. Generally, this leads to lower temperatures in the
bladder, potentially affecting treatment quality, and
suggesting that care need be taken to minimise the size of
air pockets during hyperthermia treatments.
EP-1730 Opal - The Oncology Portal and Application
J. Kildea
1
, L. Hendren
2
, D. Hererra
3
, A. Joseph
4
, R.
Maglieri
5
, T. Hijal
6
1
McGill University Health Centre, Medical Physics Unit,
Montreal, Canada
2
McGill University, School of Computer Science,
Montreal, Canada
3
University of Waterloo, Computer Science Department,
Waterloo, Canada
4
McGill University, Medical Physics Unit, Montreal,
Canada
5
McGill University Health Centre, Medical Physics, 1001
boul Décarie- Montreal, Canada