Nihon Hoshasen Gijutsu Gakkai zasshi最新文献

Purpose: The objective of this study was to quantitatively evaluate and compare the image contrast and image quality of several recently developed CT-like images (oZTEo, LAVA, MERGE).

Methods: Using a self-made phantom created with a GE Healthcare (Milwaukee, WI, USA) MRI Pioneer 3.0T and pig leg bone, along with four types of tissue-mimicking phantoms, we compared cortical bone, contrast-to-noise ratio (CNR), signal change ratio of the tissue-simulating phantom, and visual evaluation.

Results: CR and CNR were lowest in the order of MERGE, LAVA, and oZTEo. The signal change ratio of background signal and visual evaluation were highest in the order of oZTEo, LAVA, and MERGE.

Conclusion: In comparing CT-like images using MRI, the bone cortex could be visualized in white using black-and-white inversion in all CT-like images, and fracture lines could also be visualized. By capturing CT-like images tailored to the characteristics of each imaging sequence, it is expected that the number of examinations that can be completed using MRI alone will increase, further enhancing the usefulness of MRI.

Purpose: The objective of this study was to determine the standard settings of the angiography system during EVT in Japan.

Methods: Survey requests were mailed to 493 facilities across Japan. The survey items included in the survey were system display dose setting of fluoroscopy dose (FL dose)/digital angiography dose (DA dose)/digital subtraction angiography dose (DSA dose), detector size, fluoroscopy pulse rate, DA/DSA frame rate, and standard additional filter settings. The number of valid responses for each item was system display dose setting: 187 systems (128 institutions), detector size: 187 systems (128 institutions), fluoroscopy pulse rate and DA/DSA frame rate: 185 systems (127 institutions), standard additional filter settings: 182 systems (125 institutions).

Results: Median (interquartile range) of each system display dose setting was FL: 5.9 (4.2-7.8) mGy/min, DA: 0.10 (0.06-0.16) mGy/frame, DSA: 0.82 (0.64-1.40) mGy/frame. The detector size for dose measurements was 103 systems (55%) with a diagonal of 35 cm or less and 84 systems (45%) with a diagonal of more than 35 cm. The most used FL pulse rate was 7.5 pulse/s (132 systems: 71%), DA frame rate was 7.5 frame/s (72 systems: 39%), and DSA frame rate was 3 frame/s (97 systems: 52%). More than 90% of the institutions used some kind of additional filter for imaging.

Conclusion: This survey showed the standard setting of the angiography system during EVT in Japan.

Purpose: To propose a method for generating simulated images that are used to produce a contrast detail (C-D) diagram in X-ray computed tomography (CT).

Methods: We numerically generated object functions assuming ideal spheres of 7 diameters and 9 contrasts between sphere density and background density. Sphere images were calculated from the object functions by the simulation technique of image blurring based on the 3-dimensional spatial resolution measured in the CT system. The calculated sphere images were added in images of the uniform water-equivalent section of a phantom acquired at different tube currents. Obtained images were arranged according to the sphere diameter and contrast and were applied to produce the C-D diagram. For each tube current, the C-D diagram was created by a board-certified diagnostic radiologist.

Results: The calculated sphere images showed good agreements with actually acquired sphere images of the phantom. Standard deviations (SDs) in subtraction images of them were equivalent to the SD in the background region of the actual image, suggesting the accuracy of the calculated sphere images. The obtained C-D diagram showed that smaller spheres and spheres with lower contrast tended to be detected as the tube current increased.

Conclusion: The proposed method was suggested to be feasible for producing the C-D diagram for CT.

Currently, the quality control of digital breast tomosynthesis (DBT) functionality in breast X-ray equipment is not adequately implemented. In particular, DBT involves reconstruction, so depth resolution and distortion need to be evaluated. In this study, we fabricated the air hole phantoms based on the Digital Breast Tomosynthesis Quality Control Manual Ver. 1.0 (hereinafter referred to as the DBT quality control manual) and examined their usefulness as phantoms for measuring Z-resolution and geometric distortion. Using the prototype phantoms, we measured Z-resolution and geometric distortion according to the DBT quality control manual. The results of the aluminum sphere phantoms and the air hole phantoms confirmed that the z-FWHM was within or below the reference value range in the technical evaluation report by the National Coordinating Centre for the Physics of Mammography. The geometric distortion was within the specified range in the DBT quality control manual (within percentage scaling error ±5%). Therefore, it was suggested that the air-hole phantom we developed is useful for measuring the Z-resolution and geometric distortion of DBT.

Purpose: StarGuide (GE HealthCare, Haifa, Israel), a full-ring SPECT/CT system using Cadmium Zinc Telluride (CZT) technology, allows detectors to perform a pendulum motion (sweep) during SPECT acquisition. It offers two sweep modes: continuous and step and shoot, and we investigated the impact of different sweep modes on spatial resolution and image uniformity.

Methods: Spatial resolution was evaluated using the full width half maximum (FWHM) of line source images. Image uniformity was assessed using the root mean square uniformity (%RMSU) of pool phantom images. Image reconstruction was performed using the 3D-OSEM method. Attenuation correction and spatial resolution correction were applied, and no filters were used during the reconstruction process.

Results: FWHM at the center of rotation with update 500 was 5.60±0.13 mm for continuous and 4.40±0.15 mm for step and shoot. %RMSU with update 100 was 8.94±0.38% for continuous and 9.23±0.35% for step and shoot.

Conclusion: Using the step-and-shoot sweep mode can maintain high spatial resolution.