Two-phase computerized planning of cryosurgery using bubble-packing and force-field analogy.
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 paper, in an effort to improve the quality of cryosurgery.


METHODS
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 bubble-packing method, previously used as an efficient method for finite element 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 two-dimensional 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.
Department of Biomedical Engineering, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213, USA.
Daigo
D
Tanaka
Kenji
K
Shimada
Yoed
Y
Rabin
D003198:Computer Simulation; D003452:Cryosurgery / Q000379:methods*; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D008954:Models, Biological; D011300:Preoperative Care / Q000379:methods*; D011467:Prostate / Q000503:physiopathology* / Q000601:surgery*; D013314:Stress, Mechanical; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome