Novel multisensor probe for monitoring bladder temperature during locoregional chemohyperthermia for nonmuscle-invasive bladder cancer: technical feasibility study

Abstract

Background and purpose: The effectiveness of locoregional hyperthermia combined with intravesical instillation of mitomycin C to reduce the risk of recurrence and progression of intermediate- and high-risk nonmuscle-invasive bladder cancer is currently investigated in clinical trials. Clinically effective locoregional hyperthermia delivery necessitates adequate thermal dosimetry; thus, optimal thermometry methods are needed to monitor accurately the temperature distribution throughout the bladder wall. The aim of the study was to evaluate the technical feasibility of a novel intravesical device (multi-sensor probe) developed to monitor the local bladder wall temperatures during loco-regional C-HT.

Materials and methods: A multisensor thermocouple probe was designed for deployment in the human bladder, using special sensors to cover the bladder wall in different directions. The deployment of the thermocouples against the bladder wall was evaluated with visual, endoscopic, and CT imaging in bladder phantoms, porcine models, and human bladders obtained from obduction for bladder volumes and different deployment sizes of the probe. Finally, porcine bladders were embedded in a phantom and subjected to locoregional heating to compare probe temperatures with additional thermometry inside and outside the bladder wall.

Results: The 7.5 cm thermocouple probe yielded optimal bladder wall contact, adapting to different bladder volumes. Temperature monitoring was shown to be accurate and representative for the actual bladder wall temperature.

Conclusions: Use of this novel multisensor probe could yield a more accurate monitoring of the bladder wall temperature during locoregional chemohyperthermia.

FIG. 1.

Umbrella-like (deployed) multisensor probe integrated in an 18F open-end catheter. Multisensor probes were of different sizes (5, 7.5 and 10 cm) according to the deployment radius of thermocouples.

FIG. 2.

Deployment of 5 cm radius thermocouples in a bladder phantom.

FIG. 3.

Endoscopic vision shows deployment of thermocouples into the human bladder cavity. (a) 5 cm radius thermocouples; (b) 7.5 cm radius thermocouples.

FIG. 4.

Porcine bladder embedded in a saline-filled phantom (40×35×27 cm) (top). Detail of the components and placement of the phantom on the CT scan (bottom).

FIG. 5.

CT scan of the deployed 7.5 cm probe in the bladder filled with 180 mL in saline-filled phantom. Transversal slice along dotted line showing thermocouple sensors PW1–PW5 and E1–E2 (see also Fig. 6). Note small air pocket in the top of the bladder. PW=probe thermocouple at wall; E1=thermocouple outside bladder; E2=thermocouple outside bladder.

FIG. 6.

Schematic drawing of the phantom's setup and the position of thermometry probes.

FIG. 7.

This graph shows identical measurements between the PW1 and PW2 (internal bladder wall) and E1 and E2 (external) thermocouples. Bladder filled with 180 mL saline. Heating with AMC locoregional hyperthermia device between t=3 and t=18 minutes (400 W). The probe thermocouples in the lumen (PL) show a much higher temperature rise because more power is dissipated inside the bladder than in the surrounding phantom.