Daisuke Hashimoto

A proposed new image display method with high contrast-to-noise ratio using energy resolved photon-counting mammography with a CdTe series detector

In this study, we propose a new image display method to obtain high contrast-to-noise ratio (CNR) using energy resolved photon-counting mammography (ERPCM) with a cadmium telluride (CdTe) series detector manufactured by JOB CORPOLATION. The CdTe series detector can detect high-energy photons with high sensitivity, enabling users to image with high-energy X-rays. Using this detector, it is possible to reduce the dose given to a patient while increasing the CNR. First, the spectrum was divided into three bins and their corresponding linear attenuation coefficients were calculated from input and output photon numbers. Further, absorption vector length (AVL) and average absorption length (AAL) were calculated from the linear attenuation coefficients and from thicknesses of objects after beam-hardening correction. We further compared the CNR between ERPCM and general mammography images under the constant average glandular dose (AGD). We imaged an acrylic plate (1 mm thick) on RMI-156 phantom, determined regions of interest (ROIs) on an acrylic plate and background, and calculated the CNR. Our ERPCM generated two types of images: an AVL image and an AAL image. AMULET Innovality manufactured by FUJIFILM generated an integrated image. MicroDose SI manufactured by Philips generated a count image and removed electrical noise by the photon-counting technique. The four images, in order of decreasing CNR, were the AAL image, AVL image, MicroDose image, and AMULET image. The proposed method using ERPCM generated an image with higher CNR than images using general mammography under the constant AGD.

Identification of breast tissue using the x-ray image measured with an energy-resolved cadmium telluride series detector based on photon-counting technique.

We have been developing a new mammography device with a cadmium-telluride series energy-resolved photon-counting X-ray detector. Using a photon-counting technique, we examined the sensitivity of the system for differentiating the composition of breast tissue and detecting breast tumors. To differentiate breast tissues, we prepared surgically resected specimens fixed in formalin, consisting of adipose, mammary-gland, and tumor tissues. In order to obtain the values of certain effective atomic numbers, we prepared phantoms with 0%, 50% and 100% simulated mammary-gland tissue. In our imaging system, the X-ray spectrum penetrating the object was measured using three energy bins, and the products of linear attenuation coefficients and thicknesses for the three bins were calculated. These linear attenuation coefficients were properly corrected for beam hardening and normalized, to ignore the thickness. These calculations were applied for each pixel, and the gravity point per ROI (region of interest) was plotted on scatterplots to examine their distribution. Adiposetissue values were similar to known values; however, mammary-gland values were distant from expected values. In most specimens, the tumor points were focused; however, in some specimens, it was difficult to distinguish between tumor and mammary-gland tissues given their close linear attenuation coefficients. Mammary-gland tissues may have been influenced by formalin, given its tubular structure.

Development of energy-resolved photon-counting mammography with a cadmium telluride series detector to reduce radiation exposure and increase contrast-to-noise ratio using the high-energy X-rays.

A new energy-resolved photon-counting mammography (ERPCM) device with a cadmium telluride (CdTe) series detector (JOB Corporation, Japan) is currently being developed. The CdTe series detector can detect higher-energy photons with high sensitivity, enabling the use of high-energy X-rays for imaging. Our previous research, in which we compared ERPCM using high-energy X-rays (tube voltage 50 kV) with general mammography using low-energy X-rays (tube voltage about 30 kV), reported that ERPCM had a higher CNR (contrast-to-noise ratio) than general mammography. The purpose of this study was to examine the magnitude of the CNR using a simulation and ERPCM; especially we would like to examine the CNR when the tube voltage of higher than 50 kV was adopted. In the comparison of the CNRs, It was necessary to pay attention to equalizing the average glandular dose (AGD). Using the simulation and ERPCM, we compared the CNR between images taken at 50 kV and 75 kV under a constant AGD. The simulation phantom was composed of 50% mammary gland and 50% adipose tissue, and contained tumor regions. The thickness of the simulation phantom was varied. We put an acrylic plate (1 mm thickness) on an RMI-156 phantom. Furthermore, we placed the thicker acrylic plate (10, 20, 30, 40 mm) on the 156 phantom and 1 mm-thick acrylic plate to simulate thicker breast. Based on the results from the simulation, in the phantom thickness of 80 mm, the CNR of image taken by 75kV got extremely closer to that taken by 50kV. The advantage of the image taken at 75 kV for the thicker breast was also confirmed in ERPCM.