On verification of hyperthermia treatment planning for cervical carcinoma patients.
OBJECTIVE
The aim of this study was to verify hyperthermia treatment planning calculations by means of measurements performed during hyperthermia treatments. The calculated specific absorption rate (SAR(calc)) was compared with clinically measured SAR values, during 11 treatments in seven cervical carcinoma patients.


METHODS
Hyperthermia treatments were performed using the 70 MHz AMC-4 waveguide system. Temperatures were measured using multisensor thermocouple probes. One invasive thermometry catheter in the cervical tumour and two non-invasive catheters in the vagina were used. For optimal tissue contact and fixation of the catheters, a gynaecological tampon was inserted, moisturized with distilled water (4 treatments), or saline (6 treatments) for better thermal contact. During one treatment no tampon was used. At the start of treatment the temperature rise (DeltaT(meas)) after a short power pulse was measured, which is proportional to SAR(meas). The SAR(calc) along the catheter tracks was extracted from the calculated SAR distribution and compared with the DeltaT(meas)-profiles.


RESULTS
The correlation between DeltaT(meas) and SAR(calc) was on average R = 0.56 +/- 0.28, but appeared highly dependent on the wetness of the tampon (preferably with saline) and the tissue contact of the catheters. Correlations were strong (R approximately 0.85-0.93) when thermal contact was good, but much weaker (R approximately 0.14-0.48) for cases with poor thermal contact.


CONCLUSIONS
Good correlations between measurements and calculations were found when tissue contact of the catheters was good. The main difficulties for accurate verification were of clinical nature, arising from improper use of the gynaecological tampon. Poor thermal contact between thermocouples and tissue caused measurement artefacts that were difficult to correlate with calculations.
van Haaren
P M A
PM
Department of Radiation Oncology, Academic Medical Center, University of Amsterdam, The Netherlands. p.m.haaren@amc.uva.nl
Kok
H P
HP
van den Berg
C A T
CA
Zum Vörde Sive Vörding
P J
PJ
Oldenborg
S
S
Stalpers
L J A
LJ
Schilthuis
M S
MS
de Leeuw
A A C
AA
Crezee
J
J
D002404:Catheterization; D005260:Female; D006361:Heating / Q000295:instrumentation / Q000379:methods; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation* / Q000379:methods*; D052576:Menstrual Hygiene Products; D015203:Reproducibility of Results; D013696:Temperature; D013814:Thermal Conductivity; D002583:Uterine Cervical Neoplasms / Q000628:therapy*