Thermal therapy of pancreatic tumours using endoluminal ultrasound: Parametric and patient-specific modelling.
OBJECTIVE
The aim of this study is to investigate endoluminal ultrasound applicator configurations for volumetric thermal ablation and hyperthermia of pancreatic tumours using 3D acoustic and biothermal finite element models.


METHODS
Parametric studies compared endoluminal heating performance for varying applicator transducer configurations (planar, curvilinear-focused, or radial-diverging), frequencies (1-5 MHz), and anatomical conditions. Patient-specific pancreatic head and body tumour models were used to evaluate feasibility of generating hyperthermia and thermal ablation using an applicator positioned in the duodenal or stomach lumen. Temperature and thermal dose were calculated to define ablation (> 240 EM(43 °C)) and moderate hyperthermia (40-45 °C) boundaries, and to assess sparing of sensitive tissues. Proportional-integral control was incorporated to regulate maximum temperature to 70-80 °C for ablation and 45 °C for hyperthermia in target regions.


RESULTS
Parametric studies indicated that 1-3 MHz planar transducers are the most suitable for volumetric ablation, producing 5-8 cm(3) lesion volumes for a stationary 5-min sonication. Curvilinear-focused geometries produce more localised ablation to 20-45 mm depth from the GI tract and enhance thermal sparing (T(max) < 42 °C) of the luminal wall. Patient anatomy simulations show feasibility in ablating 60.1-92.9% of head/body tumour volumes (4.3-37.2 cm(3)) with dose < 15 EM(43 °C) in the luminal wall for 18-48 min treatment durations, using 1-3 applicator placements in GI lumen. For hyperthermia, planar and radial-diverging transducers could maintain up to 8 cm(3) and 15 cm(3) of tissue, respectively, between 40-45 °C for a single applicator placement.


CONCLUSIONS
Modelling studies indicate the feasibility of endoluminal ultrasound for volumetric thermal ablation or hyperthermia treatment of pancreatic tumour tissue.
a Thermal Therapy Research Group, University of California , San Francisco , California .|b University of California, Berkeley - University of California, San Francisco Graduate Program in Bioengineering , California , and.
Matthew S
MS
Adams
a Thermal Therapy Research Group, University of California , San Francisco , California .
Serena J
SJ
Scott
a Thermal Therapy Research Group, University of California , San Francisco , California .
Vasant A
VA
Salgaonkar
c Stanford Medical Center , Stanford , California , USA.
Graham
G
Sommer
a Thermal Therapy Research Group, University of California , San Francisco , California .|b University of California, Berkeley - University of California, San Francisco Graduate Program in Bioengineering , California , and.
Chris J
CJ
Diederich
D006801:Humans; D008962:Models, Theoretical; D010190:Pancreatic Neoplasms / Q000628:therapy*; D066230:Patient-Specific Modeling; D014159:Transducers; D014464:Ultrasonic Therapy
Catheter-based ultrasound; hyperthermia; pancreatic cancer; thermal ablation; thermal therapy; ultrasound