A preliminary evaluation study of applying a deep learning image reconstruction algorithm in low-kilovolt scanning of upper abdomen.

OBJECTIVE: To investigate feasibility of applying deep learning image reconstruction (DLIR) algorithm in a low-kilovolt enhanced scan of the upper abdomen. METHODS: A total of 64 patients (BMI<28) are selected for the enhanced upper abdomen scan and divided evenly into two groups. The tube voltages in Group A are 100kV in arterial phase and 80kV in venous phase, while tube voltages are 120kV during two phases in Group B. Image reconstruction algorithms used in Group A include the filtered back projection (FBP) algorithm, the adaptive statistical iterative reconstruction-Veo (ASIR-V 40% and 80%) algorithm, and the DLIR algorithm (DL-L, DL-M, DL-H). Image reconstruction algorithm used in Group B is ASIR-V40%. The different reconstruction algorithm images are used to measure the common hepatic artery, liver, renal cortex, erector spinae, and subcutaneous adipose in the arterial phase and the average CT value and standard deviation of the portal vein, liver, spleen, erector spinae, and subcutaneous adipose in the portal phase. The signal-to-noise ratio (SNR) is calculated, and the images are also scored subjectively. RESULTS: In Group A, noise in the aorta, liver, portal vein (the portal phase), spleen (the portal phase), renal cortex, retroperitoneal adipose, and muscle is significantly lower in both the DL-H and ASIR-V80% images, and the SNR is significantly higher than those in the remaining groups (P<0.05). The SNR of each tissue and organ in Group B is not significantly different from that in DL-M, DL-L, and ASIR-V40% in Group A (P>0.05). The subjective image quality scores in the DL-H and B groups are higher than those in the other groups, and the FBP group has significantly lower image quality than the remaining groups (P<0.05). CONCLUSION: For upper abdominal low-kilovolt enhanced scan data, the DLIR-H gear yields a more satisfactory image quality than the FBP and ASIR-V.

[Effect of perfusion CT scan on hepatic hemodynamic changes in rats with liver micrometastases].

BACKGROUND & OBJECTIVE: Hepatic metastases are common for patients with malignant tumors, especially for the gastrointestinal malignancies. Early diagnosis confers better prognosis. This study was designed to investigate the hepatic hemodynamic changes by multi-slice helical perfusion CT in rats with liver micrometastatases of Walker-256 tumor cells. METHODS: Liver micrometastatases were produced in 22 SD rats by injecting 2 x 10(7) Walker-256 cells into the spleens. The ten experimental control rats were injected with normal saline solution. Ten rats were randomized into empty self control group from the experimental group before injecting tumor cells, which were studied by CT perfusion technique before being injected tumor cells. The time-density curves of the aorta, portal vein, and liver were used to calculate liver perfusion parameters by gradient method designed for the dual blood supply. These liver perfusion parameters were hepatic arterial perfusion (HAP), portal vein perfusion (PVP), hepatic perfusion index (HPI) and total hepatic blood flow. All the parameters were compared between the groups. H&E staining method was used to confirm the micrometastases pathologically. RESULTS: In the experimental group, 19 rats were found with micrometastases, of which the diameter was 0.5 mm to 6.6 mm. HAP was (97.67+/-31.42) ml x min(-1) x (100 ml) (-1) in metastasis group, and (43.35+/-17.39)ml x min(-1) x (100 ml) (-1) in control group, and (40.77+/-18.91) ml x min(-1) x (100 ml) (-1) in empty self control group. PVP was (295.49+/-61.85) ml x min(-1) x (100 ml) (-1) in metastasis group, and (385.7+/-71.25) ml x min(-1) x (100 ml) (-1) in control group, and (362.73+/-78.56) ml x min(-1) x (100 ml) (-1) in empty self control group, It was found that the HAP was higher in the rats with micrometastases than in those of the empty control group and also those of control group (F=47.84, P<0.000,1). While the PVP was lower in the rats with micrometastases than in those of the two control groups (F=14.10, P<0.000,1). For the total hepatic blood flow, no significant difference was found among the three groups (F=1.39, P=0.255). CONCLUSION: Higher HAP and lower PVP was noted in the rats with micrometastases. Perfusion CT technique can be used to evaluate the hepatic hemodynamic changes and thus has a potential clinical value for early diagnosis of liver micrometastases.