Photon-counting CT: technical features and clinical impact on abdominal imaging.

Photon-counting CT has a completely different detector mechanism than conventional energy-integrating CT. In the photon-counting detector, X-rays are directly converted into electrons and received as electrical signals. Photon-counting CT provides virtual monochromatic images with a high contrast-to-noise ratio for abdominal CT imaging and may improve the ability to visualize small or low-contrast lesions. In addition, photon-counting CT may offer the possibility of reducing radiation dose. This review provides an overview of the actual clinical operation of photon-counting CT and its diagnostic utility in abdominal imaging. We also describe the clinical implications of photon-counting CT including imaging of hepatocellular carcinoma, liver metastases, hepatic steatosis, pancreatic cancer, intraductal mucinous neoplasm of the pancreas, and thrombus.

Comparison between manual and automatic image registration in image-guided radiation therapy using megavoltage cone-beam computed tomography with an imaging beam line for prostate cancer.

This study aimed to compare and assess the compatibility of the bone-structure-based manual and maximization of mutual information (MMI)-algorithm-based automatic image registration using megavoltage cone-beam computed tomography (MV-CBCT) images acquired with an imaging beam line. A total of 1163 MV-CBCT images from 30 prostate cancer patients were retrospectively analyzed. The differences between setup errors in three directions (left-right, LR; superior-inferior, SI; anterior-posterior, AP) of both registration methods were investigated. Pearson's correlation coefficients (r) and Bland-Altman agreements were evaluated. Agreements were defined by a bias close to zero and 95% limits of agreement (LoA) less than ± 3 mm. The cumulative frequencies of the absolute differences between the two registration methods were calculated to assess the distributions of the setup error differences. There were significant differences (p < 0.001) in the setup errors between both registration methods. There were moderate (SI, r = 0.45) and strong positive correlation coefficients (LR, r = 0.74; AP, r = 0.72), whereas the 95% LoA (bias ± 1.96 × standard deviation of the setup error differences) were - 1.61 ± 4.29 mm (LR), - 0.41 ± 5.45 mm (SI), and 0.67 ± 4.29 mm (AP), revealing no agreements in all directions. The cumulative frequencies (%) of the cases with absolute setup error differences within 3 mm in each direction were 80.83% (LR), 81.86% (SI), and 90.71% (AP), with all directions having large proportions of > 3-mm differences. The MMI-algorithm-based automatic registration is not compatible with the bone-structure-based manual registration and should not be used alone for prostate cancer.

Expression of mRNA for growth factors and extracellular matrix proteins after injury to cultured peritoneal cells: does the healing process contribute to peritoneal ultrastructural alteration?

The purpose of this study was to investigate the possibility that healing processes following repeated injury by nonphysiological dialysate play a significant role in the pathogenesis of peritoneal ultrastructural alteration, mediated by the production of growth factors and extracellular matrix proteins (ECM). To test a possible mechanism for peritoneal membrane alteration, we investigated whether chemically injured peritoneal mesothelial cells and fibroblasts upregulate their production of growth factors and ECM as a consequence of the healing process. Using 1 N NaOH, circular wounds of uniform surface area were made in monolayers of subconfluent rat peritoneal mesothelial cells (RPMC) and peritoneal fibroblasts (RPFB). At 0, 24, and 72 h after wounding, changes in mRNA expression of transforming growth factor-beta 1 (TGF-Beta1), b-FGF, HGF, VEGF, and FN were semiquantified by reverse transcription-polymerase chain reaction. Nonwounded monolayers of RPMC and RPFB were used as controls with mRNA expression being determined at the same times. For RPMC, TGF-Beta1, HGF, b-FGF, and FN mRNA gradually increased up to 72 h postwounding to 1.5-fold, 1.6-fold, 1.3-fold, and 2.1-fold of the control levels, respectively. A significant increase was only observed for TGF-Beta1, while VEGF showed the least change with time. For RPFB, HGF, b-FGF, VEGF, and FN mRNA expression were slightly suppressed compared to control levels up to 72 h postwounding. TGF-Beta1, however, increased markedly above control expression levels by the end of the wound healing process. The production of profibrotic growth factors by mesothelial cells in response to injury may represent a mechanism whereby fibroblast activation, resulting in fibroblast hyperplasia and excessive extracellular matrix accumulation, culminates in alteration of the peritoneal membrane ultrastructure.