ABSTRACT
A silicon nanowire field-effect transistor (SiNW-FET) coated with a polyvinyl chloride (PVC) membrane containing valinomycin (VAL) was employed as a biosensor (referred to as VAL-PVC/SiNW-FET) to detect the K(+)-efflux from live chromaffin cells. The detection sensitivity of K(+) with the VAL-PVC/SiNW-FET covers a broad range of concentrations from 10(-6) to 10(-2) M. The apparent association constants between VAL and Li(+), Na(+), K(+), and Cs(+) in Tris buffer solution were determined to be 67±42, 120±23, 5974±115, and 4121±140 M(-1), respectively. By culturing chromaffin cells on the VAL-PVC/SiNW-FET, the conductance was significantly increased by nicotine stimulation in a bath buffer without Na(+). The K(+) concentration at the cell surface was determined to be ~20 µM under the stimulation of 5 mM nicotine. These results demonstrate that the VAL-PVC/SiNW-FET is sensitive and selective to detect the released K(+) from cells and is suitable for applications in cellular recording investigations.
Subject(s)
Biosensing Techniques/instrumentation , Chromaffin Cells/metabolism , Flow Cytometry/instrumentation , Microfluidic Analytical Techniques/instrumentation , Potassium/metabolism , Transistors, Electronic , Valinomycin/chemistry , Animals , Cattle , Cells, Cultured , Chromaffin Cells/drug effects , Coated Materials, Biocompatible/chemistry , Conductometry/instrumentation , Equipment Design , Equipment Failure Analysis , Nanostructures/chemistry , Nicotine/pharmacology , Potassium/chemistry , Reproducibility of Results , Sensitivity and Specificity , Silicon/chemistryABSTRACT
PURPOSE: Polymethylmethacrylate (PMMA) slab is one of the mostly used phantoms for studying breast dosimetry in mammography. The purpose of this study was to evaluate the equivalence between exposure factors acquired from PMMA slabs and patient cases of different age groups of Taiwanese women in mammography. METHODS: This study included 3910 craniocaudal screen/film mammograms on Taiwanese women acquired on one mammographic unit. The tube loading, compressed breast thickness (CBT), compression force, tube voltage, and target/filter combination for each mammogram were collected for all patients. The glandularity and the equivalent thickness of PMMA were determined for each breast using the exposure factors of the breast in combination with experimental measurements from breast-tissue-equivalent attenuation slabs. Equivalent thicknesses of PMMA to the breasts of Taiwanese women were then estimated. RESULTS: The average +/- standard deviation CBT and breast glandularity in this study were 4.2 +/- 1.0 cm and 54% +/- 23%, respectively. The average equivalent PMMA thickness was 4.0 +/- 0.7 cm. PMMA slabs producing equivalent exposure factors as in the breasts of Taiwanese women were determined for the age groups 30-49 yr and 50-69 yr. For the 4-cm PMMA slab, the CBT and glandularity values of the equivalent breast were 4.1 cm and 65%, respectively, for the age group 30-49 yr and 4.4 cm and 44%, respectively, for the age group 50-69 yr. CONCLUSIONS: The average thickness of PMMA slabs producing the same exposure factors as observed in a large group of Taiwanese women is less than that reported for American women. The results from this study can provide useful information for determining a suitable thickness of PMMA for mammographic dose survey in Taiwan. The equivalence of PMMA slabs and the breasts of Taiwanese women is provided to allow average glandular dose assessment in clinical practice.
Subject(s)
Aging , Biomimetic Materials , Breast Neoplasms/diagnostic imaging , Breast Neoplasms/physiopathology , Phantoms, Imaging , Polymethyl Methacrylate/chemistry , Radiographic Image Interpretation, Computer-Assisted/instrumentation , Adult , Age Distribution , Aged , Aged, 80 and over , Equipment Design , Equipment Failure Analysis , Female , Humans , Middle Aged , Reproducibility of Results , Sensitivity and Specificity , Taiwan/epidemiology , Young AdultABSTRACT
OBJECTIVE: The currently used model breast for mammographic dosimetry assessment lacks the flexibility to change dimensions. The aim of this study was to develop an adjustable model breast for mammographic dosimetry assessment of Taiwanese women. MATERIALS AND METHODS: A retrospective review of 4226 craniocaudal (CC) views was conducted. The geometry of the model breast was defined as a semielliptical cylinder. Breast parameters, including compressed breast thickness, chest wall-to-nipple distance, compressed breast width, and percentage glandular content, were measured and analyzed. To validate the adjustable model breast, 44 mammograms were obtained. The expected values from the adjustable model breast were compared with the measured values. RESULTS: The average values of compressed breast thickness, chest wall-to-nipple distance, compressed breast width, and percentage glandular content of the women studied were 4.1 cm, 6.9 cm, 16.9 cm, and 54%, respectively. Variations of chest wall-to-nipple distance, compressed breast width, and percentage glandular content can be expressed as functions of compressed breast thickness, and the adjustable model breast developed was based on compressed breast thickness. The average area of the CC view obtained is a factor of 0.81 lower than that defined by the American College of Radiology protocol. For validation, the difference in average values between the expected and measured did not exceed 0.5 cm in breast dimensions and 6% in percentage glandular content. CONCLUSION: Compressed breast thickness is useful for quantifying dimensions and percentage glandular content of a model breast. The adjustable model breast developed in this study can offer greater flexibility in the determination of breast dimensions for mammographic dosimetry assessment of Taiwanese women.