To evaluate the patient identification ability of radiographers, previous and current chest radiographs were assessed with observer study utilizing a receiver operating characteristics (ROCs) analysis. This study included portable and conventional chest radiographs from 43 same and 43 different patients. The dataset used in this study was divided into the three following groups: (1) a pair of portable radiographs, (2) a pair of conventional radiographs, and (3) a combination of each type of radiograph. Seven observers participated in this ROC study, which aimed to identify same or different patients, using these datasets. ROC analysis was conducted to calculate the average area under ROC curve obtained by each observer (AUCave), and a statistical test was performed using the multi-reader multi-case method. Comparable results were obtained with pairs of portable (AUCave: 0.949) and conventional radiographs (AUCave: 0.951). In a comparison between the same modality, there were no significant differences. In contrast, the ability to identify patients by comparing a portable and conventional radiograph (AUCave: 0.873) was lower than with the matching datasets (p=0.002 and p=0.004, respectively). In conclusion, the use of different imaging modalities reduces radiographers' ability to identify their patients.
Imaging start time of single-photon emission computed tomography (SPECT) scan is recommended between 3 hours and 6 hours after injection of 123I-ioflupane in Ioflupane clinical practice guidelines. But image includes the effect of physiological actions of the human body and the attenuation at 13.27 hours physical half-life of 123I. Therefore, we evaluated the effect of the image by the elapsed time of imaging start time. Optimal cut-off frequency of Butterworth filter were examined phantom by normalized mean square error. Count was reduced by 23.1% in 5 hours, but cut-off frequency of Butterworth filter was 0.11 cycle/pixel in 0-5 hours from phantom data. Ten subjects (age 55-85 years) were injected with 123I-ioflupane of 110-199 MBq into the vein only once. And we examined the specific binding ratio (SBR) in inspection of injection after 5. 5 hours and 3hours. Decrease of counts value increased the coefficient of variance (CV) between 3hours and 5.5 hours after injection, but the improvement of statistical noise by pre-processing filter reduced the CV. No significant difference in the result of SBR was found between 3hours and 5. 5 hours after injection. Our results suggest that imaging start time of SPECT scan is recommended between 3hours and 5.5 hours after injection of 123I-ioflupane.
The most common methods to determine the signal-to-noise ratio (SNR) of magnetic resonance imaging (MRI) are based on the signal statistics in regions of interest (ROIs) in a magnitude image. For this, methods to calculate the ROI have still several discussions; we assumed SNR of a magnitude image could be estimated from standard deviation of a phase image (the phase method). The purpose of this study is to evaluate the validity of the phase method to determine the SNR. The simulation using digital phantom was carried out for evaluation of the effect to measure SNR; fluctuation in the phase image and SNR of the magnitude image. The phantom study was also performed for evaluation of the validity of estimation using the phase method in comparison with the conventional method (the identical ROI method and the subtraction method). The result of the simulation showed that SNR of magnitude image is larger than 4 for the SNR measurement using the phase method and this results reliable. The influence of fluctuation of the phase image should be eliminated for practical purposes. In the phantom study, phase method showed similar results compared to conventional methods in condition with elimination of the fluctuation of the phase image. Though there was a difference in the results of the phase method and the subtraction method according to the position of the ROI, the error was less than 4%. In this study, the method using the phase image to determine the SNR was identified as valuable.
Background: The 320-row area detector computed tomography (ADCT) for the evaluation of left ventricular (LV) systolic function has been reported, but reporting of ADCT for the evaluation of LV diastolic function (LVDF) cannot be found. The purpose of this study was to examine the usefulness of ADCT in the assessment of LV systolic and diastolic function compared to ultrasound echocardiography (Echo) as the standard of reference. Materials and methods: We evaluated 60 consecutive patients (mean age 62.4±13.2 years, male/female 36/24) who underwent ADCT (retrospective electrocardiogram triggered) and Echo. All patients were classified into three groups (A, B, C) according to LVDF evaluated by Echo. We examined peak filling rate (PFR) and time to peak filling (TPF) as indicator of LVDF using ADCT. Results: Good correlations between ADCT and Echo were demonstrated for the assessment of LVSF. PFR of group B (mild diastolic dysfunction) patients (1.92±0.69) and group C (moderate severe diastolic dysfunction) patients (1.90±0.75) were significantly lower than that of group A (normal diastolic function) patients (2.50±0.43). TPF of group B (191.6±54.4 ms) and group C patients (197.5±64.0 ms) were significantly higher than that of group A patients (149.5±34.1 ms). Conclusions: ADCT is useful method for the evaluation of LVSF and LV diastolic dysfunction.
Because of the more advanced and more complex procedures in interventional radiology, longer treatment times have become necessary. Therefore, it is important to determine the exposure doses received by operators and patients. The aim of our study was to evaluate an experimental production wireless dose monitoring system for pulse radiation in diagnostic X-ray. The energy, dose rate, and pulse fluoroscopy dependence were evaluated as the basic characteristics of this system for diagnostic X-ray using a fully digital fluoroscopy system. The error of 1 cm dose equivalent rate was less than 15% from 35.1 keV to 43.2 keV with energy correction using metal filter. It was possible to accurately measure the dose rate dependence of this system, which was highly linear until 100 μSv/h. This system showed a constant response to the pulse fluoroscopy. This system will become useful wireless dosimeter for the individual exposure management by improving the high dose rate and the energy characteristics.