Digital tomosynthesis system (DTS), which scans an object in a limited angle, has been considered as an innovative
imaging modality which can present lower patient dose than computed tomography and solve the problem of poor depth
resolution in conventional digital radiography. Although it has many powerful advantages, only breast tomosynthesis
system has been adopted in many hospitals. In order to reduce the patient dose while maintaining image quality, the
acquisition conditions need to be studied. In this study, we analyzed effective dose and image qualities of chest phantom using commercialized universal chest digital tomosynthesis (CDT) R/F system to study the optimized exposure
parameters. We set 10 different acquisition conditions including the default acquisition condition by user manual of Shimadzu (100 kVp with 0.5 mAs). The effective dose was calculated from PCXMC software version 1.5.1 by utilizing
the total X-ray exposure measured by ion chamber. The image quality was evaluated by signal difference to noise ratio (SDNR) in the regions of interest (ROIs) pulmonary arteries at different axial in-plane. We analyzed a figure of merit
(FOM) which considers both the effective dose and the SDNR in order to determine the optimal acquisition condition.
The results indicated that the most suitable acquisition parameters among 10 conditions were condition 7 and 8 (120 kVp
with 0.04 mAs and 0.1 mAs, respectively), which indicated lower effective dose while maintaining reasonable SDNRs and FOMs for three specified regions. Further studies are needed to be conducted for detailed outcomes in CDT acquisition conditions.
Recently, there have been several physics and clinical studies on the use of lower tube potentials in CT imaging, with the purpose of improving image quality or further reducing radiation dose. We investigated an experimental study using a series of different sized, polymethyl methacrylate (PMMA) phantoms, demonstrating the potential strategy for dose reduction and to distinguish component of plaque by imaging their energy responses using CT. We investigated the relationship between different sizes of cylinderic PMMA-equivalent phantoms with diameter of 12, 16, 20, 24, and 32 cm and used contrast at various tube voltages (80, 100, 120, and 140 kVp) using a 16–detector row CT scanner. The contrast represented CT numbers as different materials for the water, calcium chloride, and iodine. Phantom insertions also allow quantitative measures of image noise, contrast, contrast-to-noise ratio (CNR) and figure of merit (FOM). When evaluating FOM, it was found that the lower kVp provided the better CNR. An experimental study was performed to demonstrate reduced dose for both dose efficient and practical feasibility for different patient sizes and diagnostic tasks by relating achievable CNR and the volume CT dose index (CTDIvol). The use of spectra optimized to the specific application could provide further improvements of distinguishing iodine, calcium and plaque component for patient size. The purpose of this study was to evaluate variations in image noise and contrast using different tube potentials in a CTDI phantom on contrast imaging.
In conventional digital radiography (DR) using a dual energy subtraction technique, a significant fraction of the detected
photons are scattered within the body, resulting in the scatter component. Scattered radiation can significantly deteriorate
image quality in diagnostic X-ray imaging systems. Various methods of scatter correction, including both measurement and
non-measurement-based methods have been proposed in the past. Both methods can reduce scatter artifacts in
images. However, non-measurement-based methods require a homogeneous object and have insufficient scatter
component correction. Therefore, we employed a measurement-based method to correct for the scatter component of
inhomogeneous objects from dual energy DR (DEDR) images. We performed a simulation study using a Monte Carlo
simulation with a primary modulator, which is a measurement-based method for the DEDR system. The primary
modulator, which has a checkerboard pattern, was used to modulate primary radiation. Cylindrical phantoms of variable
size were used to quantify imaging performance. For scatter estimation, we used Discrete Fourier Transform filtering.
The primary modulation method was evaluated using a cylindrical phantom in the DEDR system. The scatter
components were accurately removed using a primary modulator. When the results acquired with scatter correction and
without correction were compared, the average contrast-to-noise ratio (CNR) with the correction was 1.35 times higher
than that obtained without correction, and the average root mean square error (RMSE) with the correction was 38.00%
better than that without correction. In the subtraction study, the average CNR with correction was 2.04 (aluminum
subtraction) and 1.38 (polymethyl methacrylate (PMMA) subtraction) times higher than that obtained without the
correction. The analysis demonstrated the accuracy of scatter correction and the improvement of image quality using a
primary modulator and showed the feasibility of introducing the primary modulation technique into dual energy
subtraction. Therefore, we suggest that the scatter correction method with a primary modulator is useful for the DEDR
The quantitative estimation was performed to verify the effect the low dose imaging with fewer projection data using
micro-CT with total variation (TV) minimization method. To assess the image contrast and noise, sparse data were
obtained from the projection data of the phantom and the mouse. Filtered-backprojection (FBP) images of the projection
data of the phantom and the mouse were used as a reference image reconstructed with 400 projection data. Universal
quality index (UQI) was used as an image similarity metric for comparison between TV minimization algorithm and
FBP algorithm for both the phantom and the mouse image. Contrast-to-noise ratio (CNR) values for the image derived
from TV minimization algorithm with 80-view was approximately 45 % higher than FBP with 400-view up to 10 %
iodine solution material. UQI values for the phantom and the mouse images were measured with 0.974 and 0.999,
respectively. Low dose image using TV minimization algorithm was proved to be advantageous for micro-CT system.
Contrast and noise properties on image from TV minimization at few-view were higher than FBP 80-view and full-view
scan. However, CNR from 15 % iodine solution to 20 % iodine solution were lower than FBP due to the lower-intensity
of the x-rays. The reconstructed images for both phantom and mouse from TV minimization algorithm were well
matched to FBP-reference images.