Effects of spray parameters on skin tumour ablation volume during cryotherapy.

The main purpose of the study is to establish correlations for the ablation volume and the ice front as a function of the spray parameters. The ablation volume and the ice front depend upon the nozzle diameter, spraying distance and the freeze duration (spray parameters). The estimation of the ablation volume using the spray parameters shall be useful in surgical practice to ablate the different sizes of tumours. Liquid nitrogen spray cooling is carried out with 0.8 mm, 0.6 mm and 0.4 mm nozzle diameters. The spraying distance is maintained at 9 mm, 18 mm and 27 mm. The spray cooling is carried out for a single freeze-thaw cycle where freezing and thawing consist of 120 s and 130 s duration respectively. A two-dimensional heat flow equation with phase change is considered for the numerical study. The numerically calculated transient temperature (2 mm and 5 mm from the gel surface) and ice front values show confirmatory results with the experimentally measured data. Correlations are obtained to determine the ablation volume (- 50 °C and - 25 °C isothermal surfaces) and ice front (axial and lateral) with a goodness of fit [Formula: see text] 95%. The nozzle diameter has a greater impact on the ablation volume as compared to the spraying distance during 120 s of freezing. The nozzle diameter of 0.8 mm, 0.6 mm and 0.4 mm can be effectively used for cryotherapy with spraying distance up to 27 mm, 18 mm and 9 mm respectively.

Utility of squash smear cytology in fiber-optic bronchoscopic biopsies.

BACKGROUND: Fiber-optic bronchoscopic biopsies yield very small bits of tissue, leading to high false negativity in lung cancer diagnosis, after paraffin embedding. AIM: The aim of the present study is to assess the diagnostic efficacy of squash smear cytology of fiber-optic bronchoscopic biopsies and to compare this with standard paraffin embedded sections and sputum cytology. MATERIALS AND METHODS: A total of 100 suspected cases of lung cancer were subjected to fiber-optic bronchoscopic biopsies. Multiple biopsies from each were divided into two portions. One portion was processed routinely and paraffin sections made. Squash smears were made from the other and stained by Papanicolaou method. The diagnostic efficiency of two methods was compared. A positive diagnosis of cancer by any of the diagnostic modalities initially or during 6 months follow-up was taken as the gold standard. RESULTS: Out of 100 cases, 91 cases proved to be cancer. The pick-up rate was 0.77 for squash cytology, 0.55 for tissue sections, and 0.31 for sputum cytology. The pick-up was higher for endo-bronchial tumors by all methods. The agreement between squash cytology and tissue sections was 100% for small cell carcinoma and adenocarcinoma and 88% for squamous cell carcinoma. CONCLUSION: Squash smear cytology has better pick-up rate than paraffin embedding in fiber-optic bronchoscopic biopsies and should be the preferred method when only one or few bits are available.