Temperature field reconstruction for minimally invasive cryosurgery with application to wireless implantable temperature sensors and/or medical imaging

Abstract

There is an undisputed need for temperature-field reconstruction during minimally invasive cryosurgery. The current line of research focuses on developing miniature, wireless, implantable, temperature sensors to enable temperature-field reconstruction in real time. This project combines two parallel efforts: (i) to develop the hardware necessary for implantable sensors, and (ii) to develop mathematical techniques for temperature-field reconstruction in real time-the subject matter of the current study. In particular, this study proposes an approach for temperature-field reconstruction combining data obtained from medical imaging, cryoprobe-embedded sensors, and miniature, wireless, implantable sensors, the development of which is currently underway. This study discusses possible strategies for laying out implantable sensors and approaches for data integration. In particular, prostate cryosurgery is presented as a developmental model and a two-dimensional proof-of-concept is discussed. It is demonstrated that the lethal temperature can be predicted to a significant degree of certainty with implantable sensors and the technique proposed in the current study, a capability that is yet unavailable.

Figure 1

Temperature field regions resulted from the transient solution of Case A (the benchmark) at the point of optimal match between the freezing-front location and the prostate contour; cryoprobes are illustrated with white dots.

Figure 2

Temperature field regions for Case I: complete freezing front information from medical imaging (Case B) with no temperature sensors; cryoprobes are illustrated with white dots.

Figure 3

Temperature fields difference, ΔT, between the benchmark solution and the solution for Case I: complete freezing front information (Case B) with no temperature sensors; cryoprobes are illustrated with black dots.

Figure 4

Temperature fields difference, ΔT, between the benchmark solution and the solution for Case II: complete freezing front information (Case B) with six sensors implanted along the −22°C isotherm at the locations of maximum temperature difference in Fig. 3; cryoprobes are illustrated with black dots and sensors with white “×”.

Figure 5

Temperature field regions for Case III: partial freezing front information obtained from a transrectal ultrasound transducer (Case C), combined with six sensors implanted along the −22°C isotherm, and six additional sensors equally distributed along the unobservable portion of the prostate contour (upper portion of the figure); α is the field of view of the trans-rectal ultrasound transducer; cryoprobes are illustrated with white dots and sensors with white “×”.

Figure 6

Temperature fields difference, ΔT, between the benchmark solution and the solution for Case III: partial freezing front information obtained from a trans-rectal ultrasound transducer (Case C) combined with six sensors implanted along the −22°C isotherm, and six additional sensors equally distributed along the unobservable portion of the prostate contour (upper portion of the figure); cryoprobes are illustrated with black dots and sensors with white “×”.

Figure 7

Temperature field reconstruction for Case IV (Case D—solely based on temperature sensors with no imaging data): twelve sensors equally distributed along the −22°C isotherm; cryoprobes are illustrated with white dots and sensors with white “×”.

Figure 8

Mismatch in the areas bounded by the lethal isotherm, ΔA_lethal, between the benchmark (Case A) and the Case B, where complete freezing-front data is available from medical imaging, and the temperature sensor are equally distributed along predicted isotherms.

Figure 9

Mismatch in the areas bounded by the lethal isotherm, ΔA_lethal, between the benchmark (Case A) and the case of partial freezing-front data available from medical imaging (Case C), where the temperature sensors are equally distributed along the freezing front, and combined with temperature sensors distributed along the −22°C and −45°C isotherms.

Figure 10

Mismatch in the area bounded by the lethal isotherm, ΔA_lethal, between the benchmark (Case A) and the case where no imaging data is available for the purpose of extracting the location of the freezing front (Case D), where temperature sensors are equally distributed along the −22°C and −45°C isotherms.