Energy Calibration of a CdTe Photon Counting Spectral Detector with Consideration of its Non-Convergent Behavior.

Fast and accurate energy calibration of photon counting spectral detectors (PCSDs) is essential for their biomedical applications to identify and characterize bio-components or contrast agents in tissues. Using the x-ray tube voltage as a reference for energy calibration is known to be an efficient method, but there has been no consideration in the energy calibration of non-convergent behavior of PCSDs. We observed that a single pixel mode (SPM) CdTe PCSD based on Medipix-2 shows some non-convergent behaviors in turning off the detector elements when a high enough threshold is applied to the comparator that produces a binary photon count pulse. More specifically, the detector elements are supposed to stop producing photon count pulses once the threshold reaches a point of the highest photon energy determined by the tube voltage. However, as the x-ray exposure time increases, the threshold giving 50% of off pixels also increases without converging to a point. We established a method to take account of the non-convergent behavior in the energy calibration. With the threshold-to-photon energy mapping function established by the proposed method, we could better identify iodine component in a phantom consisting of iodine and other components.

New pulse wave measurement method using different hold-down wrist pressures according to individual patient characteristics.

In traditional Chinese and Korean medicine, doctors first observe a patient's pulse by gently and strongly pressing their fingers onto the wrist, and then make a diagnosis based on the observed pulse waves. The most common method to implement this diagnostic technique is to mechanically extract the pulse waves by applying a fixed range of pressures for all patients. However, this method does not consider the patients individual characteristics such as age, sex, and skin thickness. In the present study, we propose a new method of pulse wave extraction that incorporates the personal characteristics of the patients. This method measures the pulse wave signal at varying hold-down pressures, rather than applying a fixed hold-down pressure for all patients. To compare this new technique with existing methods, we extracted pulse waves from 20 subjects, and then determined the actual applied pressure at each step, the coefficient of floating and sinking pulse (CFS), and the distinction of floating/sinking pulse for each group. Consequently, each subject had a different pressure range in our proposed method, whereas all subjects had a similar pressure range in the existing method. Four of 20 subjects exhibited different floating/sinking pulse patterns due to the value of the first pressure step and the range of hold-down pressures. These four subjects were categorized as overweight based on BMI. In addition, the moving distance of the proposed method was longer than the existing method (p = 0.003, paired t-test), and the correlation coefficient between CFS values of two different methods was 0.321, indicating that there was no correlation.

New computerized indices for quantitative evaluation of depression and asymmetry in patients with chest wall deformities.

An evaluation index that can quantitatively assess the severity of chest wall deformities is essential to prepare and assess corrective surgical operations for patients with these deformities, including funnel chest patients. In previous studies, our group proposed several automatically calculated indices that represent the severity of depression and asymmetry in the chest wall. These indices showed sufficient performance in most cases of deformities, including those involving asymmetric and symmetric depression; however, their linearity declined when assessing complex deformities. The purpose of this study is to propose two automated indices that provide linear evaluation output for all types of chest wall deformities, including complex deformities, and to evaluate their performance and clinical feasibility. Six reference chest wall boundary curves were obtained from 60 computed tomography (CT) images of a normal chest. Next, an active contour model-based image processing technique was used to extract boundary curves from images of patients with real chest wall deformities. Third, the required parameters were extracted from the boundary curves and the targeted indices were calculated. Finally, the performance of the proposed indices was evaluated using 33 synthetic images and 60 real chest CT images of patients with chest wall deformities. The newly proposed indices can be automatically calculated from the original CT images and showed sufficient performance for all types of chest wall deformities. We believe that the newly proposed indices can facilitate pre- and postoperative evaluation of chest wall deformities in clinical practice.

Development of a radial pulse tonometric (RPT) sensor with a temperature compensation mechanism.

Several RPT sensors have been developed to acquire objective and quantitative pulse waves. These sensors offer improved performance with respect to pressure calibration, size and sensor deployment, but not temperature. Since most pressure sensors are sensitive to temperature, various temperature compensation techniques have been developed, but these techniques are largely inapplicable to RPT sensors due to the size restrictions of the sensor, and incompatibility between the compensation techniques and the RPT sensor. Consequently, in this paper a new RPT sensor comprising six piezoresistive pressure sensors and one thermistor has been developed through finite element analysis and then a suitable temperature compensation technique has been proposed. This technique compensates for temperature variations by using the thermistor and simple compensation equations. As verification of the proposed compensation technique, pulse waves of all types were successfully compensated for temperature changes.

Bone-induced streak artifact suppression in sparse-view CT image reconstruction.

BACKGROUND: In sparse-view CT imaging, strong streak artifacts may appear around bony structures and they often compromise the image readability. Compressed sensing (CS) or total variation (TV) minimization-based image reconstruction method has reduced the streak artifacts to a great extent, but, sparse-view CT imaging still suffers from residual streak artifacts. We introduce a new bone-induced streak artifact reduction method in the CS-based image reconstruction. METHODS: We firstly identify the high-intensity bony regions from the image reconstructed by the filtered backprojection (FBP) method, and we calculate the sinogram stemming from the bony regions only. Then, we subtract the calculated sinogram, which stands for the bony regions, from the measured sinogram before performing the CS-based image reconstruction. The image reconstructed from the subtracted sinogram will stand for the soft tissues with little streak artifacts on it. To restore the original image intensity in the bony regions, we add the bony region image, which has been identified from the FBP image, to the soft tissue image to form a combined image. Then, we perform the CS-based image reconstruction again on the measured sinogram using the combined image as the initial condition of the iteration. For experimental validation of the proposed method, we take images of a contrast phantom and a rat using a micro-CT and we evaluate the reconstructed images based on two figures of merit, relative mean square error and total variation caused by the streak artifacts. RESULTS: The images reconstructed by the proposed method have been found to have smaller streak artifacts than the ones reconstructed by the original CS-based method when visually inspected. The quantitative image evaluation studies have also shown that the proposed method outperforms the conventional CS-based method. CONCLUSIONS: The proposed method can effectively suppress streak artifacts stemming from bony structures in sparse-view CT imaging.

A pulse wave simulator for palpation in the oriental medicine.

Pulse diagnosis, which is one of methods of diagnosis, is an important factor in oriental medicine. However, a problem in diagnosis with the pulse is that there is no objective standard. Therefore, the practitioners pass on the skill and students learn about pulse diagnosis as a method that depends on speech. In this study, the electronic pulse wave reproduction apparatus, which is an objective and accurate means for measuring the pulse, was developed. The previous model reproduced the pulse wave in one part of the point, but it was made by using three pairs of voice coil motors (VCM) in order to similarly express the three parts of the pulse: Cun, Guan and Chi. To evaluate this system, the output of the pulse wave was confirmed in order to reproduce the pulse wave with these settings. Consequently, the targets for slow pulse and rapid pulse have a 7 ms standard deviation, which is within the error tolerance. A voltage value of H(1), utilized to verify vacuous pulse and the replete pulse, has a standard deviation range of 4.7-5.4 mV. This system, which is similar to a person's pulse diagnosis, can be used to educate others in pulse diagnosis both quantitatively and scientifically.

Spectrofluorimetric determination of vitamin B(1) using horseradish peroxidase as catalyst in the presence of hydrogen peroxide.

In this work a new spectrofluorimetric method for the determination of vitamin B(1), based on the catalytic activity of horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H2O2), has been developed. Non-fluorescent vitamin B(1) was easily converted through catalytic oxidation in alkaline medium into a fluorescent compound, even without exposure to light. The linear range for vitamin B(1) observed was 0.026-16.83 microg/mL (RSD = 1.75%). The correlation coefficient for the calibration curve and limit of detection were found to be 0.9964 and 0.015 microg/mL, respectively. The developed method is practical, simple, sensitive and relatively free from interference by coexisting substances and has been successfully applied for the determination of vitamin B(1) in pharmaceutical preparations.

Simultaneous determination of acetylsalicylic acid and caffeine in pharmaceutical formulation by first derivative synchronous fluorimetric method.

A sensitive, rapid, and specific assay has been developed for the simultaneous determination of acetylsalicylic acid and caffeine in commercial tablets based on their natural fluorescence. The mixture of these drugs was resolved by first derivative synchronous fluorimetric technique using two scans. At Deltalambda=106 nm, using first derivative synchronous scanning, only acetylsalicylic acid yields a detectable signal at 316 nm (peak to zero method) which is unaffected by caffeine. At Deltalambda=30 nm, the signal of caffeine at 288 nm (peak to zero method) is not affected by acetylsalicylic acid. The range of application is between 0.021 and 41.62 microg ml(-1) (correlation coefficient, R=0.9995) for acetylsalicylic acid and between 0.4486 and 44.86 microg ml(-1) (correlation coefficient, R=0.99786) for caffeine. The recovery range of 98.40-102% for acetylsalicylic acid and 90-100.5% for caffeine from their synthetic mixture was reported. Overall recovery of both compounds about 97-99% for acetylsalicylic acid and 97-98% for caffeine was obtained from real sample analysis. The detection limits are 0.0013 microg ml(-1) and 0.0306 microg ml(-1) for acetylsalicylic acid and caffeine, respectively. The relative standard deviation (n=10) for 20 microg ml(-1) of acetylsalicylic acid is 2.75% and for 2.2 microg ml(-1)of caffeine is 1.7%.