Monocular Stereo Measurement Using High-Speed Catadioptric Tracking.

This paper presents a novel concept of real-time catadioptric stereo tracking using a single ultrafast mirror-drive pan-tilt active vision system that can simultaneously switch between hundreds of different views in a second. By accelerating video-shooting, computation, and actuation at the millisecond-granularity level for time-division multithreaded processing in ultrafast gaze control, the active vision system can function virtually as two or more tracking cameras with different views. It enables a single active vision system to act as virtual left and right pan-tilt cameras that can simultaneously shoot a pair of stereo images for the same object to be observed at arbitrary viewpoints by switching the direction of the mirrors of the active vision system frame by frame. We developed a monocular galvano-mirror-based stereo tracking system that can switch between 500 different views in a second, and it functions as a catadioptric active stereo with left and right pan-tilt tracking cameras that can virtually capture 8-bit color 512 × 512 images each operating at 250 fps to mechanically track a fast-moving object with a sufficient parallax for accurate 3D measurement. Several tracking experiments for moving objects in 3D space are described to demonstrate the performance of our monocular stereo tracking system.

Motion-Blur-Free High-Speed Video Shooting Using a Resonant Mirror.

This study proposes a novel concept of actuator-driven frame-by-frame intermittent tracking for motion-blur-free video shooting of fast-moving objects. The camera frame and shutter timings are controlled for motion blur reduction in synchronization with a free-vibration-type actuator vibrating with a large amplitude at hundreds of hertz so that motion blur can be significantly reduced in free-viewpoint high-frame-rate video shooting for fast-moving objects by deriving the maximum performance of the actuator. We develop a prototype of a motion-blur-free video shooting system by implementing our frame-by-frame intermittent tracking algorithm on a high-speed video camera system with a resonant mirror vibrating at 750 Hz. It can capture 1024 × 1024 images of fast-moving objects at 750 fps with an exposure time of 0.33 ms without motion blur. Several experimental results for fast-moving objects verify that our proposed method can reduce image degradation from motion blur without decreasing the camera exposure time.

Pixel-Level and Robust Vibration Source Sensing in High-Frame-Rate Video Analysis.

We investigate the effect of appearance variations on the detectability of vibration feature extraction with pixel-level digital filters for high-frame-rate videos. In particular, we consider robust vibrating object tracking, which is clearly different from conventional appearance-based object tracking with spatial pattern recognition in a high-quality image region of a certain size. For 512 × 512 videos of a rotating fan located at different positions and orientations and captured at 2000 frames per second with different lens settings, we verify how many pixels are extracted as vibrating regions with pixel-level digital filters. The effectiveness of dynamics-based vibration features is demonstrated by examining the robustness against changes in aperture size and the focal condition of the camera lens, the apparent size and orientation of the object being tracked, and its rotational frequency, as well as complexities and movements of background scenes. Tracking experiments for a flying multicopter with rotating propellers are also described to verify the robustness of localization under complex imaging conditions in outside scenarios.

Evaluation of the clinical utility of temporal subtraction using bone suppression processing in digital chest radiography.

Rationale and objectives: To evaluate the usefulness of temporal subtraction using the bone suppression method in digital chest radiography for the detection of pulmonary lesions. Materials and methods: The images of 31 patients with pulmonary lesions and 19 normal cases were included in the study. Conventional and bone suppression temporal subtraction were performed in the 50 cases selected and used for an observer performance study. Five radiologists participated in the study, and the differences between using conventional and bone suppression temporal subtraction were assessed using jackknife free-response receiver operating characteristic analysis. Results: The average figure-of-merit values for all radiologists increased significantly using the bone suppression method, from 0.619 (conventional) to 0.696 (p = 0.032). The average sensitivity for detecting pulmonary lesions improved from 67.9% to 75.4%, and the average number of false-positive per case decreased from 0.336 to 0.252 using bone suppression temporal subtraction. Conclusion: Bone suppression temporal subtraction processing can assist with the detection of subtle pulmonary lesions in digital chest radiographs.

Calculating the target exposure index using a deep convolutional neural network and a rule base.

PURPOSE: The objective of this study is to determine the quality of chest X-ray images using a deep convolutional neural network (DCNN) and a rule base without performing any visual assessment. A method is proposed for determining the minimum diagnosable exposure index (EI) and the target exposure index (EIt). METHODS: The proposed method involves transfer learning to assess the lung fields, mediastinum, and spine using GoogLeNet, which is a type of DCNN that has been trained using conventional images. Three detectors were created, and the image quality of local regions was rated. Subsequently, the results were used to determine the overall quality of chest X-ray images using a rule-based technique that was in turn based on expert assessment. The minimum EI required for diagnosis was calculated based on the distribution of the EI values, which were classified as either suitable or non-suitable and then used to ascertain the EIt. RESULTS: The accuracy rate using the DCNN and the rule base was 81%. The minimum EI required for diagnosis was 230, and the EIt was 288. CONCLUSION: The results indicated that the proposed method using the DCNN and the rule base could discriminate different image qualities without any visual assessment; moreover, it could determine both the minimum EI required for diagnosis and the EIt.

The clinical significance of modifying X-ray tube current-time product based on prior image deviation index for digital radiography.

PURPOSE: The absorbed dose at the image receptor in digital X-ray systems increases with an incorrect adjustment of the X-ray tube current-time product (mAs). Accordingly, the exposure index, target exposure index, and deviation index (DI) are proposed as absorbed dose optimization tools. We aimed at reducing the variation of DI in a short period by employing the mAs value determined by previously used mAs and DI. METHODS: We developed software that automatically calculates mAs for subsequent X-ray examinations based on mAs and DI values from prior examinations. Portable chest X-ray examinations in an intensive care unit (ICU) were performed for 16 weeks. The software was not used for the first 10 weeks in 406 cases and was used for the remaining 6 weeks in 216 cases. The changes in the non-conformance rate of DI for 16 weeks were evaluated using the p-chart used for quality control. The effect of the software on image noise was also evaluated. RESULTS: In total, 42% of cases had a DI range of -1 to 1 without using the software; this increased to 81% when using the software. Averages and variances of DI in cases with and without the software demonstrated statistically significant differences. From the p-chart, the non-conformance rate of DI was shown to decrease when using software. The software also worked for reducing the variation in image noise. CONCLUSIONS: Our method reduced the variation in DI in a short period of time.

Additive value of split-bolus single-phase CT scan protocol for preoperative assessment of lung cancer patients referred for video-assisted thoracic surgery.

We aimed to assess the additive value of the split-bolus single-phase computed tomography (CT) scan protocol to preoperatively assess patients with lung cancer, who were referred for video-assisted thoracic surgery, when compared to a standard staging CT protocol. We included 160 patients with lung cancer who underwent a split-bolus single-phase CT scan protocol (split-bolus protocol), which can acquire whole-body staging CT and pulmonary artery-vein separation CT angiography (PA-PV CTA) in a single acquisition and 160 patients who underwent whole-body staging CT (standard protocol). We compared the quality of the staging CT images of hepatic parenchyma, portal vein, and hepatic vein between both protocols. We also investigated image quality on PA-PV CTA images in the split-bolus protocol and recorded the number of patients that underwent the 3D PA-PV CTA imaging process. The split-bolus protocol for staging CT images demonstrated a slightly higher enhancement with regard to the hepatic parenchyma (p = 0.007) and hepatic vein (p = 0.006) than the standard protocol. There was no significant difference in the quality of the staging CT images between both protocols (p = 0.067). The mean CT number for the main pulmonary artery and the left atrium for the PA-PV CTA images in the split-bolus protocol were 289.1 HU and 172.8 HU, respectively. Among the images associated with the split-bolus protocol, 98.1% were of appropriate quality for 3D PA-PV CTA imaging. The split-bolus protocol is a dose-efficient protocol to acquire the staging CT and PA-PV CTA images in a single session and provides sufficient image quality for preoperative assessment in patients with lung cancer.

Evaluation of the effects of subject thickness on the exposure index in digital radiography.

The exposure index (EI) was proposed as a new X-ray dose index by the International Electrotechnical Commission (IEC) and has since been implemented as an international standard. The EI is calculated by use of an approximation equation under IEC-specified calibration conditions. However, several factors encountered in clinical practice, including the patient's body thickness and the tube voltage, differ with regard to these calibration conditions. We, therefore, require a solid water phantom-based function that can incorporate the IEC-specified conditions and different subject thicknesses to evaluate the effects of subject thickness on the EI. Here, we assumed average thicknesses of 10 cm for a child, 15 cm for slender patients, and 21 cm for an average adult abdomen and we evaluated errors, that are included in the EI, which were calculated by use of the function. Our results suggested that the EI depends on the subject thickness. At the 21-cm thickness (average adult abdomen), the display EI exhibited a small error level. In contrast, EI values calculated from the calibration conditions exhibited maximum errors that were as high as 34 % at the lower subject thicknesses (10 and 15 cm), suggesting a significant influence of the subject thickness on the EI. In conclusion, the EI should be used cautiously during the examination of children and thin patients, with a complete understanding of the discrepancy revealed by our study results.

Real-time laryngoscopic measurements of vocal-fold vibrations.

We have developed a high-frame-rate laryngoscope that can measure the vibration distribution of a human vocal fold in real time at hundreds of hertz. Our laryngoscope can extract a vocal-fold contour at 4000 fps as 20 pairs of its left and right border points from 256 × 512-pixel images to quantify left-right asymmetry of vocal-fold vibrations. Experiments on artificial vocal-fold-like vibrations of a silicon rubber membrane were performed to confirm the laryngoscope's effectiveness, and the vocal folds of human subjects, including patients with laryngeal diseases, were examined under clinical conditions.

Development of broad-view camera unit for laparoscopic surgery.

A disadvantage of laparoscopic surgery is the narrow operative field provided by the endoscope camera. This paper describes a newly developed broad-view camera unit for use with the Broad-View Camera System, which is capable of providing a wider view of the internal organs during laparoscopic surgery. The developed camera unit is composed of a miniature color CMOS camera, an indwelling needle, and an extra-thin connector. The specific design of the camera unit and the method for positioning it are shown. The performance of the camera unit has been confirmed through basic and animal experiments.