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146. Conformal cryosurgery assisted by laser heating: feasibility study
Abstracts / Cryobiology 55 (2007) 324–378 substances (TBARS) chromophore that has maximum absorption at 532 nm. A method to measure MDAs in fresh RBC specimens was originally described by Stocks et al., [Stocks, J. and T.L. Dormandy, The autoxidation of human red cell lipids induced by hydrogen peroxide. British Journal of Haematology, 1971. 20(1): p. 95-111]. However, this technique, as well as other commercial assays, has not been applied to lyophilized RBC specimens, mainly due to hemoglobin interference. The proposed method has modified the MDA extraction process to ensure that there are no hemoglobin residues in the sample extracts. The ability to measure MDAs in dried RBC specimens was verified by examining the recovery of MDA standards added to fresh RBCs (control), and RBCs that were later lyophilized. The recovery rates of MDA standards in lyophilized RBCs were reasonable (>80 %), considering the fact that drying and rehydration are accompanied with sample loss. The formation of MDAs in lyophilized RBC specimens was also examined over time. Lyophilized RBCs had higher levels of MDAs than fresh RBCs (22.9 ± 2.64 nmol/g hemoglobin versus 5.8 ± 0.38 nmol/g hemoglobin, respectively). Storage of dried RBC specimens at room temperature increased the MDA levels from 22.9 ± 2.64 nmol/g hemoglobin to 76 ± 9.03 nmol/g hemoglobin and 92 ± 4.66 nmol/g hemoglobin after 24 and 72 h storage (n = 4). This data provides first evidence regarding the relationship between oxidative damage and desiccation. The modification of the MDA assay to dried cells will contribute to understanding the mechanism of damage that occurs during dehydration, dry storage and rehydration of dry biomaterials. (Conflicts of interest: None declared. Source of funding: None declared). doi:10.1016/j.cryobiol.2007.10.148
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147. The pattern of the ice ball formed during freezing of a phantom gel embedded with simulated blood vessels. Jing-Fu Yan, Yi-Xin Zhou, Jing Liu, Zhong-Shan Deng, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China It is becoming clear that warm blood flowing through large vessels surrounding a target tumor means that the freezing power applied by an external applicator is to some extent reduced, and this generally results in insufficient cooling and thus incomplete destruction of tumor cells close to the vessel. There is currently a major lack of understanding of this important issue, for example the dynamic effect of vascular structures on the formation of the ice ball when biological tissues with embedded blood vessels is subjected to various patterns of freezing. In this report, several typical vascular models, which have been widely used in simulations of tissue temperature during tumor hyperthermia, are constructed in order to visualize the effects of large blood vessels on transient ice-ball formation during freezing of the phantom gel. The gel was embedded with simulated blood vessels in a given cryosurgical treatment pattern consisting of two cryoprobes combined in different configurations and applied by subjecting them to 5mins 0 freezing and 5mins 0 heating. Various diameters of vessel, as well as the flow velocity of blood in the vessels, and different spatial distributions between probes and blood vessels were all studied visually. The pictures of the ice ball were taken from different orientations by a digital camera and then quantitatively evaluated. The results obtained could serve as a valuable guide for the optimal placement of cryoprobes when performing cryosurgical treatments in the vicinity of blood vessels. (Conflicts of interest: None declared. Source of funding: None declared). doi:10.1016/j.cryobiol.2007.10.150
Cryosurgery 146. Conformal cryosurgery assisted by laser heating: feasibility study. Zhong-Shan Deng, Jing Liu, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China Cryosurgery, as an important minimally invasive surgical method for the treatment of tumors, has been receiving more and more attention in the biomedical field. To obtain an optimal cryosurgical result , total and exact destruction of tumor tissues is very important. Failure to do so can lead either to insufficient or excessive freezing, and consequently result in tumor recurrence or destruction of healthy tissue. Therefore, adequate treatment of tumors has been a major concern in cryosurgery. Total destruction of tumors can be achieved by appropriately arranging multiple cryoprobes. However, it is still an unsolved problem to exactly kill tumor tissues by the current cryosurgical techniques. This is particularly important for cryosurgical treatment of tumors situated at or surrounding important organs, where the destruction of healthy tissue may result in serious complications. In this study, an effective approach for preventing freezing injury to tumor-peripheral healthy tissues with important function was proposed. It uses controlled laser heating to maintain the healthy tissue above the pre-specified threshold temperature of freezing injury while multiple cryoprobes freeze the tumor tissues, and thus possibly perform more optimal cryosurgical treatment. The feasibility of the present method was demonstrated through numerical simulation. The three-dimensional complex phase change processes in biological tissues subjected to freezing by multiple cryoprobes, assisted or not assisted by laser heating, were compared numerically. It was shown that controlled laser heating can confine the intended freezing-destroyed region more accurately than the current cryosurgical techniques and that the adjuvant use of laser heating is expected to serve as a promising method to perform optimal cryosurgery in future oncological clinics. (Conflicts of interest: None declared. Source of funding: In part by the National Science Foundation of China under Grants 50576104 & 50325622.) doi:10.1016/j.cryobiol.2007.10.149
148. Characterization of cell death and survival within cryogenic lesions using a tissue engineered human prostate cancer model. Anthony T. Robilotto a,b, Dominic Clarke a,b, John M. Baust a,b, Robert G. Van Buskirk a,b, Andrew A. Gage b, John G. Baust a, a Binghamton University, Binghamton, NY, USA; b Cell Preservation Services, Inc., Owego, NY, USA Since its inception, a major limiting factor for cryosurgical ablation has been determining the extent of cell death within the generated cryogenic lesion. Although great strides have been taking in modeling the thermal profile of the freeze zone, and in aiding proper probe placement and freeze duration, much remains to be accomplished in determining the percentage of cells that survive or perish given a specific isotherm within the lesion. To that end, we have employed a recently developed tissue engineered human prostate cancer model for use in mapping the levels of cell death to specific temperatures within the cryogenic lesion. Human prostate cancer cells (PC3) were suspended in collagen matrices 30 mm in diameter and 3 mm thick at a density of 2 · 106 cells/mL. Just prior to freezing, matrices were stacked ten high (30 mm), placed in a 37 C saline bath, and then frozen using an Oncura SeedNet Gold cryosurgical device with 17-guage cryoneedles in various configurations. Temperatures were monitored throughout the cryogenic lesion using an array of type T thermocouples. At 24 hr post-thaw, matrices were assessed using membrane integrity assays to visualize the zone of complete, partial, and minimal cell destruction. Results show that, after 10 min of freezing, a single 17-guage cryoneedle generated an egg shaped freeze zone of 32 mm in length with a diameter of 26 mm at its widest point. Additionally, by utilizing our engineered model, cell death/survival was visualized within the lesion and mapped to specific thermal zones. At temperatures below 60 C no cell survival was observed, at 40 C approximately 5% of cells survive, at 20 C there was approximately 75% survival, and at temperatures above 20 C cell survival was at or above 85%. We have shown that by employing our engineered human prostate model we can begin to correlate levels of cell death/survival to specific thermal zones within the cryogenic lesion. Ultimately, such data may provide physicians with additional parameters for the optimization of cryosurgical procedures by ensuring proper exposure
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147. The pattern of the ice ball formed during freezing of a phantom gel embedded with simulated blood vessels. Jing-Fu Yan, Yi-Xin Zhou, Jing Liu, Zhong-Shan Deng, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China It is becoming clear that warm blood flowing through large vessels surrounding a target tumor means that the freezing power applied by an external applicator is to some extent reduced, and this generally results in insufficient cooling and thus incomplete destruction of tumor cells close to the vessel. There is currently a major lack of understanding of this important issue, for example the dynamic effect of vascular structures on the formation of the ice ball when biological tissues with embedded blood vessels is subjected to various patterns of freezing. In this report, several typical vascular models, which have been widely used in simulations of tissue temperature during tumor hyperthermia, are constructed in order to visualize the effects of large blood vessels on transient ice-ball formation during freezing of the phantom gel. The gel was embedded with simulated blood vessels in a given cryosurgical treatment pattern consisting of two cryoprobes combined in different configurations and applied by subjecting them to 5mins 0 freezing and 5mins 0 heating. Various diameters of vessel, as well as the flow velocity of blood in the vessels, and different spatial distributions between probes and blood vessels were all studied visually. The pictures of the ice ball were taken from different orientations by a digital camera and then quantitatively evaluated. The results obtained could serve as a valuable guide for the optimal placement of cryoprobes when performing cryosurgical treatments in the vicinity of blood vessels. (Conflicts of interest: None declared. Source of funding: None declared). doi:10.1016/j.cryobiol.2007.10.150
Cryosurgery 146. Conformal cryosurgery assisted by laser heating: feasibility study. Zhong-Shan Deng, Jing Liu, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing, China Cryosurgery, as an important minimally invasive surgical method for the treatment of tumors, has been receiving more and more attention in the biomedical field. To obtain an optimal cryosurgical result , total and exact destruction of tumor tissues is very important. Failure to do so can lead either to insufficient or excessive freezing, and consequently result in tumor recurrence or destruction of healthy tissue. Therefore, adequate treatment of tumors has been a major concern in cryosurgery. Total destruction of tumors can be achieved by appropriately arranging multiple cryoprobes. However, it is still an unsolved problem to exactly kill tumor tissues by the current cryosurgical techniques. This is particularly important for cryosurgical treatment of tumors situated at or surrounding important organs, where the destruction of healthy tissue may result in serious complications. In this study, an effective approach for preventing freezing injury to tumor-peripheral healthy tissues with important function was proposed. It uses controlled laser heating to maintain the healthy tissue above the pre-specified threshold temperature of freezing injury while multiple cryoprobes freeze the tumor tissues, and thus possibly perform more optimal cryosurgical treatment. The feasibility of the present method was demonstrated through numerical simulation. The three-dimensional complex phase change processes in biological tissues subjected to freezing by multiple cryoprobes, assisted or not assisted by laser heating, were compared numerically. It was shown that controlled laser heating can confine the intended freezing-destroyed region more accurately than the current cryosurgical techniques and that the adjuvant use of laser heating is expected to serve as a promising method to perform optimal cryosurgery in future oncological clinics. (Conflicts of interest: None declared. Source of funding: In part by the National Science Foundation of China under Grants 50576104 & 50325622.) doi:10.1016/j.cryobiol.2007.10.149
148. Characterization of cell death and survival within cryogenic lesions using a tissue engineered human prostate cancer model. Anthony T. Robilotto a,b, Dominic Clarke a,b, John M. Baust a,b, Robert G. Van Buskirk a,b, Andrew A. Gage b, John G. Baust a, a Binghamton University, Binghamton, NY, USA; b Cell Preservation Services, Inc., Owego, NY, USA Since its inception, a major limiting factor for cryosurgical ablation has been determining the extent of cell death within the generated cryogenic lesion. Although great strides have been taking in modeling the thermal profile of the freeze zone, and in aiding proper probe placement and freeze duration, much remains to be accomplished in determining the percentage of cells that survive or perish given a specific isotherm within the lesion. To that end, we have employed a recently developed tissue engineered human prostate cancer model for use in mapping the levels of cell death to specific temperatures within the cryogenic lesion. Human prostate cancer cells (PC3) were suspended in collagen matrices 30 mm in diameter and 3 mm thick at a density of 2 · 106 cells/mL. Just prior to freezing, matrices were stacked ten high (30 mm), placed in a 37 C saline bath, and then frozen using an Oncura SeedNet Gold cryosurgical device with 17-guage cryoneedles in various configurations. Temperatures were monitored throughout the cryogenic lesion using an array of type T thermocouples. At 24 hr post-thaw, matrices were assessed using membrane integrity assays to visualize the zone of complete, partial, and minimal cell destruction. Results show that, after 10 min of freezing, a single 17-guage cryoneedle generated an egg shaped freeze zone of 32 mm in length with a diameter of 26 mm at its widest point. Additionally, by utilizing our engineered model, cell death/survival was visualized within the lesion and mapped to specific thermal zones. At temperatures below 60 C no cell survival was observed, at 40 C approximately 5% of cells survive, at 20 C there was approximately 75% survival, and at temperatures above 20 C cell survival was at or above 85%. We have shown that by employing our engineered human prostate model we can begin to correlate levels of cell death/survival to specific thermal zones within the cryogenic lesion. Ultimately, such data may provide physicians with additional parameters for the optimization of cryosurgical procedures by ensuring proper exposure