Two-Phase Computerized Planning of Cryosurgery Using Bubble-Packing and Force-Field Analogy

Abstract

Background: Cryosurgery is the destruction of undesired tissues by freezing, as in prostate cryosurgery, for example. Minimally-invasive cryosurgery is currently performed by means of an array of cryoprobes, each in the shape of a long hypodermic needle. The optimal arrangement of the cryoprobes, which is known to have a dramatic effect on the quality of the cryoprocedure, remains an art held by the cryosurgeon, based on the cryosurgeon's experience and "rules of thumb." An automated computerized technique for cryosurgery planning is the subject matter of the current report, in an effort to improve the quality of cryosurgery. Method of Approach:A two-phase optimization method is proposed for this purpose, based on two previous and independent developments by this research team. Phase I is based on a bubblepacking method, previously used as an efficient method for finite elements meshing. Phase II is based on a force-field analogy method, which has proven to be robust at the expense of a typically long runtime. Results:As a proof-of-concept, results are demonstrated on a 2D case of a prostate cross-section. The major contribution of this study is to affirm that in many instances cryosurgery planning can be performed without extremely expensive simulations of bioheat transfer, achieved in Phase I. Conclusions:This new method of planning has proven to reduce planning runtime from hours to minutes, making automated planning practical in a clinical time frame.

Simulation-Based Cryosurgery Intelligent Tutoring System Prototype

“…Each case used a different geometrical model of the prostate and the urethra, which was generated by means of geometrical deformation, based on ultrasound-reconstructed organs (28). All cases were limited to a uniform insertion depth for cryoprobes (29), where the trainee can only select the x and y coordinates for each probe (follow-on studies are planned to address multi-depth configurations, which presents a higher level of planning complexity in 3D).…”

Graphics Processing Unit-Based Bioheat Simulation to Facilitate Rapid Decision Making Associated with Cryosurgery Training

“…Such a short time can be considered instantaneous for the purpose of providing an early prediction of the cryoprocedures outcome when compared with the actual cryosurgical procedure, which is measured in several minutes or longer. This capability of rapid simulations advances the discussion about cryosurgery computation from merely analyzing a special case to analyzing a battery of cases in effort to improve decision making, which would be an integral part of any computerized planning (6,18,32), computerized training (12,16), or an intelligent approach to control of the procedure. Such a battery of cases may contain a varying set of problems in the search for an optimum, or a set of “what-if” scenarios for the benefit of training and medical education.…”

Generating prostate models by means of geometric deformation with application to computerized training of cryosurgery

“…The template for deformation has been developed in a previous study focusing on computerized planning of cryosurgery [8]; these templates have been created from 3D ultrasound data. Figure 7 displays a deformed model with right unilateral ECE.…”

“…While early sporadic studies have been presented to optimize the cryoprobe layout [4–6], those studies have been based on traditional optimization techniques, where the associated computation cost prohibited reduction to clinical practice. More recently, two alternative optimization techniques have been developed, known as force-field analogy [7] and bubble-packing [8–10], which accelerated the optimization process tremendously. Combined with an efficient numerical technique to simulate the bioheat transfer process of tissue freezing [11], computerized planning is closer than ever before to become a clinical reality.…”