Investigating the cryoablative efficacy of a hybrid cryoprobe operating under freeze–thaw cycles

Three-dimensional numerical evaluation of skin surface thermal contrast by application of hypothermia at different depths and sizes of the breast tumor

BACKGROUND AND OBJECTIVE

Thermal procedures can provide improvements in the thermal contrast of thermographic images in an attempt to diagnose early cases of breast cancer. This work aims to analyze the thermal contrast of different stages and depths of breast tumors from hypothermia treatment using an active thermography analysis. The influence of variation in metabolic heat generation and adipose tissue composition on thermal contrasts is also analyzed.

METHODS

The proposed methodology was based on the solution of the Pennes equation for a three-dimensional model similar to the real anatomy of the breast by commercial software COMSOL Multiphysics. The thermal procedure consists of three steps: Stationary, hypothermia and thermal recovery. During hypothermia, the boundary condition of the external surface was replaced by a constant temperature of 0, 5, 10, and 15 ^∘C, simulating a gel pack, for cooling times of up to 20 min. In the thermal recovery, after the removal of the cooling, the breast was submitted again to the condition of natural convection on the external surface.

RESULTS

Thermal contrasts in superficial tumors, for all hypothermia resulted in improvements in thermographs. For smallest tumor, the use of high resolution and sensitive thermal imaging cameras to acquire this thermal change may be necessary. For tumor of diameter of 10 cm, cooling from 0 ^∘C can increase the thermal contrast by up to 136% compared to the passive thermography. Analyzes with deeper tumors showed very small temperature variations. Even so, the thermal contrast gain in cooling at 0 ^∘C for the tumor with a diameter of 1 cm reached 37% in relation to passive thermography.

CONCLUSIONS

Thus, this work contributes as an important tool in the analysis of the appropriate use of hypothermia for different cases in early stages of breast cancer, considering that long times are needed to obtain the best thermal contrast.

An efficient thermal evolution model for cryoablation with arbitrary multi-cryoprobe configuration

Cryoablation has been demonstrated powerful in treating of a variety of diseases, especially for the tumor ablation, which destroys the target tissue through the controlled freezing of cryoprobe. The prediction of temperature evolution during cryoablation is of great importance for developing and improving clinical procedure. This paper presented an efficient thermal model to characterize the freezing effect of cryoprobe with arbitrary layout including its size, orientation and number. The key step of the presented model is to establish a boundary heat source method to implicitly characterize the heat transfer from cryoprobe with fixed temperature or convective heat transfer boundary condition, which is furthermore incorporated to a fast parallel alternating direction explicit (PADE) finite difference method for computation acceleration. A novel dynamical and conformal computational region is designed through the shortest distance definition to balance the thermal effect of tissue and computational efficiency. The detailed test cases including a real head tissue demonstrated that the current model can accurately predict the temperature field evolution induced by arbitrary multi-cryoprobe configuration, and achieve significant computational ability due to allowable large time step (100-fold compared with the explicit finite difference method), compact computational region (at least reducing 40% number of voxels) and high parallel efficiency (speedup ratio about 8 for 12 threads) for complex tissue structure.

Resection or cryosurgery relates with pancreatic tumor type: primary pancreatic cancer with previous non-pancreatic cancer or secondary metastatic cancer within the pancreas

OBJECTIVES

We investigated the incidence of primary pancreatic cancer with previous non-pancreatic cancer (PPC) and secondary metastatic cancer within the pancreas (SMC) to elucidate the differential diagnosis and treatment of these lesions.

METHODS

The clinical data of 2539 patients with pancreatic mass in Tianjin Cancer Hospital from January 2000 to December 2012 were retrospectively analyzed. All of the 66 patients who showed double or multiple primary cancers or metastatic pancreatic malignancies were included into the PPC group or SMC group, respectively. In addition, PPC patients were compared with 570 patients suffering from pancreatic cancer (PC) alone.

RESULTS

For the PPC group (n = 34), the most common previous non-pancreatic cancers were gastric cancer, breast cancer, and thyroid cancer. For the SMC group (n = 32), the most common metastatic tumors were lung cancer, renal cell carcinoma (RCC), and gastric cancer. Multivariate analysis identified age (OR = 1.099; 95% CI, 1.007-1.199), previous tumor type (OR = 1.164; 95% CI, 1.046-1.296), and time interval between two tumors (OR = 1.021; 95% CI, 1.003-1.039) as significant indicators. Significantly better survival times were observed after resection than after cryosurgery in the PPC group (p < 0.001) but not in the SMC group (p = 0.670).

CONCLUSIONS

Overall, primary pancreatic cancers are as common as metastasis to the pancreas in patients with a previous cancer. A longer time interval between two tumors indicates a higher possibility that a new pancreatic cancer will occur. Some cancers (particularly RCC) are more likely to metastasize to the pancreas than other cancers. For metastatic cancers, cryosurgery is as effective as resection as a treatment option.