Intraprostatic temperature monitoring during transurethral microwave thermotherapy: status and future developments

Evaluation of three temperature measurement methods used during microwave thermotherapy of prostatic enlargement

Three temperature measurement methods used during microwave thermotherapy of prostatic enlargement are analysed and evaluated using a phantom model. A commercial transurethral microwave thermotherapy (TUMT) system that uses a radiometric thermometer for temperature control was used to heat the phantom. The transient temperature distribution was obtained by using both fibreoptic (which is considered as gold standard) and thermocouple measurements. Both methods are subject to potential measurement errors caused by electromagnetic and/or thermal interference. The error sources are analysed and the measurement methods evaluated. The radiometric temperature and especially its relation to the transient temperature distribution was evaluated based on the fibreoptic and thermocouple measurements. These measurements in principle gave equivalent temperature distributions, and thermal interference was concluded to be the largest source of measurement error. The radiometric measurement method gave qualitative rather than quantitative readings of the temperature, and an underestimation of more than 10 degrees C was obtained for some parts of the heated area. The area that gives most of the radiometric signal was relatively close to the catheter in contrast to previously published results.

Microwave thermotherapy of prostatic enlargement--analysis of radiometric thermometry using a hybrid bio-heat equation

The radiometric temperature measurement included in a commercial device for transurethral microwave thermotherapy (TUMT) of the prostate was investigated utilizing both phantom experiments and computer simulations. Two finite element (FE) models were developed. One is in part based on the experimental results, and serves as a complement to the experiments, while the other describes a perfused tissue situation for which the hybrid bio-heat equation was used to model the thermal effects of blood perfusion. The aim of the study was to investigate how the radiometric thermometer is affected by the temperature close to the antenna, and to analyze the relation between blood perfusion, temperature distribution and radiometric temperature measurement. It was found that the radiometric temperature was affected to a greater extent by the temperature very close to the antenna, in contrast to what has been expected in previous studies. The blood perfusion was found to mainly affect the temperature distribution outside the maximum temperature (located 2-3 mm outside the cooled catheter). Thus, the relation between the radiometric temperature and the temperature in the treated area is relatively weak.

Long-term treatment outcomes of CoreTherm microwave feedback thermotherapy

The gold standard for definitive management of symptomatic benign prostatic hypertrophy is transurethral resection of the prostate (TURP). Despite its efficacy, TURP has significant morbidity/mortality concerns such as hemorrhage and transurethral resection syndrome. This is especially worrisome for the medically high-risk patient, but the high rates of retrograde ejaculation found with TURP also pose a problem for young patients. A minimally invasive, outpatient alternative to TURP that has long-term efficacy, low morbidity/mortality, and provides a cost-effective advantage is in high demand. This review article discusses microwave thermotherapy as such an option and reports the long-term experience with the CoreTherm (CoreTherm Operations AB, Sweden) device.

Transurethral microwave thermotherapy: the gold standard for minimally invasive therapies for patients with benign prostatic hyperplasia?

From all available minimally invasive methods for the treatment of symptomatic benign prostatic hyperplasia (BPH), transurethral microwave thermotherapy (TUMT) has gained a firm position as the most attractive option. Recent research has produced innovations in high-energy TUMT, including new treatment protocols, refined selection criteria, and monitoring of intraprostatic temperature. Furthermore, long-term results from randomized studies comparing TUMT with transurethral resection of the prostate (TURP) or medical treatment are now available. All these data indicate that more durable clinical outcomes and less morbidity can be achieved with TUMT, strengthening its position as a standard treatment for BPH. This paper describes the status of TUMT in the treatment of lower urinary tract symptoms related to BPH, focusing on variations in the outcomes with different devices, the durability of treatment outcomes, morbidity, selection criteria, and cost. The relation of TUMT to medical management and TURP also is addressed.

Quantification of prostate shrinkage after microwave thermotherapy: a comparison of calculated cell-kill versus 3D transrectal ultrasound planimetry

PURPOSE

To compare prostate shrinkage after transurethral microwave thermotherapy (TUMT) with calculated cell-kill.

MATERIALS AND METHODS

The calculated cell-kill from 33 males with benign prostatic hyperplasia (BPH) treated with TUMT according to the ProstaLund Feedback Treatment (PLFT) method was compared to the post-treatment prostate volume change. The prostate volume was estimated with three-dimensional transrectal ultrasound (3D-TRUS) planimetry at baseline, 3, 6, and 12 months follow-up. A paired t-test was used to test the statistical significance of differences between the cell-kill volume and the prostate volume change. Linear regression was used to infer a relationship between the cell-kill and the 3D-TRUS data. The reproducibility of the 3D-TRUS method was assessed in repeated measurements.

RESULTS

The mean prostate volume at baseline (N=33) was 56.1cm(3). After 3 (N=25), 6 (N=29) and 12 months (N=23), it was 45.5 cm(3), 39.7 cm(3), and 45.1cm(3), respectively. The corresponding average cell-kill volume was 16.4 cm(3), 17.1cm(3), and 17.2 cm(3), respectively. Predicted cell-kill volume was significantly larger than prostate shrinkage at 3 (p<0.0001), 6 (p=0.0002), and 12 months (p<0.0001), and showed a strong correlation at 3 and 6 months (r=0.74, p<0.0001). Correlation at 12 months was moderate (r=0.57, p=0.0041). Examination and investigation variability both averaged 2.5%.

CONCLUSIONS

Cell-kill calculations of the PLFT method are proportional to the 3D-TRUS prostate shrinkage by a factor of 0.5 and have a precision of approximately +/-10 cm(3) for 90% of the patients during the first year after treatment.

Heat treatment of the prostate: where do we stand in 2000?

Various minimally invasive modalities that are aimed at alleviating lower urinary tract symptoms employ heat-induced ablation of hyperplastic prostatic tissue. Following extensive studies, most of these modalities were eventually abandoned. High-energy transurethral microwave thermotherapy has survived, however, and has gained a firm position as a therapeutic modality, along with transurethral resection of the prostate. Recent research addressed fundamental issues of mode of action of microwave treatment, and revealed the overall efficacy of this treatment, determined new indications, and rendered high-energy transurethral microwave thermotherapy more acceptable to the patients. Insights into intraprostatic vascularization and treatment monitoring were also gained as a result of these global research efforts.