Nihon Hoshasen Gijutsu Gakkai zasshi最新文献

Purpose: The measurement of slice sensitivity profile (SSP) in non-helical CT is conventionally performed by repeated scans with moving a micro-coin phantom little by little in the longitudinal direction at a small interval, which is reliable but laborious and time-consuming. The purpose of this study was to propose a simple method for measuring the SSP in non-helical CT based on a previous method that measured the slice thickness using a tilted metal wire.

Methods: In the proposed method, a CT image was obtained by scanning a wire tilted at an angle θ=30° to the scan plane. By deconvolving the image with the point spread function (PSF) measured at the scanner, we obtained an image that was not affected by the PSF blurring. The CT value profile along the wire was acquired on the obtained image. The SSP was determined by multiplying the profile by tan θ. In addition, the SSP was measured by the conventional method using a micro-coin phantom and compared with the SSP obtained by the proposed method.

Results: The SSP measured by the proposed method agreed well with that measured by the conventional method. The full-width at half-maximum values of these SSPs were the same.

Conclusion: The proposed method was demonstrated to easily and accurately measure the SSP in non-helical CT.

Purpose: In this study, we aimed to develop an application that computes dose values resembling diagnostic reference level (DRL) conditions when disparity prevents direct dose comparisons between the national diagnostic reference levels in Japan 2020 (Japan DRLs_2020) and facility-specific computed tomography (CT) protocols.

Methods: We developed an application using the R programming language and RStudio software that computes dose values and median values based on Japan DRLs_2020 imaging conditions following extraction of necessary information for dose calculations from the Radiation Dose Structured Report (RDSR) and Digital Imaging and Communications in Medicine (DICOM) tags. To ensure a user-friendly experience, we used the Shiny package to develop a graphical user interface that enables the application to operate seamlessly in web browsers.

Results: The developed application successfully facilitated the calculation of dose and median values that aligned with the Japan DRLs_2020 for protocols whose imaging range and acquisition timing differed from those of the Japan DRLs_2020.

Conclusion: By calculating dose values that align with DRL conditions, our application contributes to the implementation and optimization of dose management in CT for facilities that use diverse imaging protocols.

Purpose: This study proposes a system that can simulate head radiography by combining a technique for estimating human posture from moving images (hereafter referred to as "pose estimation technique") and use of two cameras capable of acquiring RGB images to determine body position during positioning.

Methods: The angles of the median sagittal plane (MS), axial plane (AX), and orbitomeatal baseline (OM) were obtained using the pose estimation technique from frontal and lateral images captured after positioning. The resulting radiographs were displayed according to the results.

Results: The head tilt during positioning could be determined based on the coordinate data of feature points acquired using the pose estimation technique. In an imaging experiment using a simulated human patient, errors increased as head tilt increased; however, the mean error values in each axis were 0.9° for MS, 0.8° for AX, and 1.5°for OM, when the patient was correctly positioned.

Conclusion: The pose estimation technique can assist in evaluating positioning accuracy in radiography and is expected to be used as a potential simulator system.

Purpose: The aim of this study was to evaluate artifacts in the skull base region of head computed tomography (CT) images with various tilt angles relative to the orbitomeatal line.

Methods: CT images of a head phantom acquired by helical and non-helical scanning with the tilt angles set from 0 to 20 degrees in 5-degree increments were evaluated in this study. Regions of interest (ROIs) were set at the cerebellum, temporal lobe, frontal lobe, and basal ganglia in the phantom images. Artifacts were evaluated by the coefficient of variation (CV) of the mean CT value between ROIs and the location parameter (β) of the Gumbel method.

Results: The CV and β values increased with increasing tilt angle for both helical and nonhelical images in the frontal lobes, but both decreased in the cerebellar region. In the temporal lobe and basal ganglia, there was no trend of change with tilt angle.

Conclusion: Increasing the tilt angle relative to the OM line increased artifacts at the frontal lobes and decreased artifacts at the cerebellar region.

A diffusion-weighted whole body imaging with background body signal suppression (DWIBS) is usually imaged as a whole body with Transverse (Tra). However, Tra has a large number of stations and a larger number than Coronal (Cor), so the scan time is longer. There are also drawbacks, such as signal unevenness between series. It is known that the effect of distortion is large in Cor. There is no report on it in Sagittal (Sag). Therefore, in this study, we focused on Sag and examined the imaging time, image distortion, fat suppression effect, and continuity between stations. In the examination by the phantom, the scan time was the shortest for Cor and the longest for Sag. In the strain evaluation, the effect of strain could be suppressed compared to Cor by using a rectangle field of view (FOV) in the anterior to posterior (AP) direction in Tra and Sag. There was no difference in the fat suppression effect depending on the imaging direction. Similar results were obtained in a study of 10 healthy volunteers, with Sag having the best continuity between stations.

Purpose: We evaluated the measurement accuracy of the CubeScan BioCon-900 (here after BioCon-900), a portable ultrasound imaging diagnostic device capable of measuring bladder volume, to determine if it can accurately assess bladder volume before intensity-modulated radiation therapy (IMRT) for prostate cancer.

Methods: Bladder volume was measured from kV-Cone Beam computed tomography (CBCT) images obtained immediately before the administration of IMRT for prostate cancer using Halcyon. The bladder volume measured from kV-CBCT images (23 patients, total number of scans: 139) immediately before the IMRT procedure was used as the reference value. The difference between the bladder volume measured by the BioCon-900 was then calculated.

Results: The bladder volume measured from kV-CBCT images was 117.5±49.4 cc. In contrast, the bladder volume obtained with BioCon-900 was 104.1±48.6 ml, resulting in an absolute mean difference of 18.4% and a correlation coefficient of 0.881. The measurements by BioCon-900 tended to be, on average, 11% smaller than the bladder volume measured by kV-CBCT imaging.

Conclusion: kV-CBCT images demonstrated a strong positive correlation between bladder volume and bladder urine output obtained with BioCon-900. BioCon-900 can be used before kV-CBCT imaging to accurately and conveniently assess bladder volume.

Purpose: Osteosclerotic images are known as an image appearance of occult femoral neck fractures in X-ray images. The aim of this study is to investigate frequency enhancement processing that improves the visibility of the osteosclerotic image.

Methods: We acquired three sclerotic bone images with different thicknesses, and self-made bone equivalent phantoms were set up on a pelvic phantom. The frequency processing type and high-density enhancement coefficients were applied to the X-ray images taken at RF-A(1.0, 2.0), C(2.0, 4.0), D(1.0), and H(2.0, 4.0). For the physical index, we compared the difference in signal values between the sclerotic and background normal bone. We evaluated the preference using Scheffé's paired comparison methods for the visual index.

Results: For the physical index, RF-C(4.0) had the most significant signal value difference for all 3 bone stiffness images. For the visual index, RF-C(4.0) showed the highest preference.

Conclusion: Using frequency-enhanced processing, RF-C(4.0) was suggested to improve the visibility of the osteosclerosis image.

【Purpose】 Accurate control of X-ray units and dosimeters and analysis of the uncertainties associated with the accurate measurement of radiation doses are essential for the effective establishment and application of diagnostic reference levels. In this study, the uncertainty of the average glandular dose (AGD) in the quality control of mammography equipment was evaluated in detail, and recommendations were provided to improve the accuracy and safety of radiological practice. 【Methods】 In the uncertainty analysis of the AGD, the relative standard uncertainties in the measurements of the half-value layer, the incident air kerma, and the conversion factor were considered and finally expressed as expanded uncertainties, the intervals of which were clearly defined. 【Results】 From the AGD measurements using two types of dosimeters, it was found that the primary sources of uncertainty are the uncertainty of the calibration factors of the dosimeters and the uncertainty of the conversion factors.【Conclusion】 To reduce uncertainty, the use of regularly calibrated dosimeters is effective and reliable. Two types of dosimeters are commonly used; the results of this study may serve as a reference value for the uncertainty of AGD in quality control in medical facilities.

Purpose: To verify the usefulness of a deep learning model for determining the presence or absence of contrast-enhanced myocardium in late gadolinium-enhancement images in cardiac MRI.

Methods: We used 174 late gadolinium-enhancement myocardial short-axis images obtained from contrast-enhanced cardiac MRI performed using a 3.0T MRI system at the University of Tokyo Hospital. Of these, 144 images were used for training, extracting a region of interest targeting the heart, scaling signal intensity, and data augmentation were performed to obtain 3312 training images. The interpretation report of two cardiology specialists of our hospital was used as the correct label. A learning model was constructed using a convolutional neural network and applied to 30 test data. In all cases, the acquired mean age was 56.4±12.1 years, and the male-to-female ratio was 1 : 0.82.

Results: Before and after data augmentation, sensitivity remained consistent at 93.3%, specificity improved from 0.0% to 100.0%, and accuracy improved from 46.7% to 96.7%.

Conclusion: The prediction accuracy of the deep learning model developed in this research is high, suggesting its high usefulness.

In this study, we investigated the effects of various disinfectants used to prevent infectious diseases on medical images and medical equipment. First, we investigated the effect of residual disinfectant on medical images in CT, mammography (MMG), and general imaging systems. Acrylic discs with various disinfectants attached were photographed using each imaging device, and visual evaluation and changes in image signal values were evaluated. We also conducted a questionnaire survey of each manufacturer regarding cleaning methods for medical devices. With CT/MMG, residual disinfectant could be visually confirmed on the image. Although this could not be confirmed with the general imaging system, a significant difference was confirmed in the image signal values of the general imaging system through statistical analysis. This is thought to be largely due to the influence of nonlinearity in the short-time imaging range of general imaging equipment. In addition, from the responses to a questionnaire survey of each medical device manufacturer, we were able to understand detailed cleaning methods that are not covered in medical device instruction manuals.