Clinical Study Of Histological Grading And Preoperative Staging Of Gastric Cancer With Dual-Energy CT

Gastric cancer is one of the most common cancers, approximately accounting for about8percent of new cancers. Nowaday MDCT has been widely used in preoperativestaging of gastric cancer. However there are still somecontroversial problems. Dual-energy computed tomography (DECT) uses polyenergetic X-rays at100kV and140kV tube energy, and generates120kV composite images that are referred to as polyenergetic images.Moreover, DECT can produce monoenergetic images at any effective energy level. Virtual non-enhanced (VNE) images using DECT have been applied in terms of reducing radiation exposure. To evaluate whether the image quality of gastric cancer is improved by optimizing the energy levels of DECT. And to evaluate the clinical utility in staging gastric cancers.Part One Optimization of energy level and staging for gastric cancer with dual-energy and dual-source computed tomographyObjective:To evaluate whether the image quality of gastric cancer is improved by optimizing the energy levels of DECT. And to evaluate the clinical utility in staging gastric cancers. Methods:55patients(41men,19women; mean age59.38years; range23～81years) suspected gastric cancers were included in the study between December2011and February2013. A week later,43patients(31men,12women; mean age59.05years; range23～78years)was operated. Patients underwent dual-phasic scans (arterial phase and portal venous phase) using DECT at100kV and140kV tube energy with a dual-source scanner, we evaluated the relationships image quality parameters in100kV,120kV and70keV images. Image quality parameters comprised mean density, objective noise and signal-to-noise ratio (SNR). The120kV and70keV images were compared in TNM staging.Results:1. In arterial phase, The mean gastric cancer’s attenuation was significantly higher at100kV (87.28～23.91HU) and70keV (84.86～21.59HU) compared to120kV (73.08～17.49HU) images (P<0.001). In comparison to100kV (23.80～6.53HU), the image noise was lower at70keV (17.3～4.5HU, P<0.01) and120kV(16.67±4.44HU, P<0.01). Likewise, the SNR were higher at120Kv(4.58±1.32HU) and70keV (4.97±1.44HU) in comparison to100kV (3.84±1.29HU, P<0.01). Attenuation was higher and SNR was similar at70keV, compared with120kV composite images.2. In portal phase, The mean gastric cancer’s attenuation was significantly higher at100kV (102.10±21.06HU) and70keV (101.33±18.68HU) compared to120kV (83.70±15.37HU) images (P<0.01). In comparison to100kV (25.53±7.93HU), the image noise was lower at70keV (18.37±5.31HU, P<0.01)and120kV (18.16±5.25HU, P<0.01). Likewise, the SNR were higher at70keV(5.93±2.00HU) in comparison to120kV (5.01±1.91HU) and100kV (4.43±2.03HU, P<0.01). Attenuation and SNR were higher at70keVcompared with120kV composite images.3. Overall accuracy in assessment of tumor invasion of the gastric wall (T stage) was83.7%with70keV images and72.1%with120kV images. This difference was not significant (P=0.25). Accuracy rates for each T stage with120kV and70keV images, respectively, were88.4%and95.3%for T1,81.4%and90.7%for T2-3,83.7%and88.3%for T4a, and95.3%and95.3%for T4b. 4. Overall accuracy for lymph node (N) staging was significantly better with70keV images(74.4%) than with120kV images(83.7%)(P<0.05). Accuracy rates for each N stage with70keV and120kV images, respectively, were86.0%and86.0%for NO,86.0%and76.7%for N1,83.7%and81%for N2, and93.0%and88.4%for N3.Conclusion:The image quality of gastric cancers using DECT can be improved by optimizing the energy level for individual patients. the70keV images may be used to improve the N-staging accuracy. Part Two Dual energy CT in patients with gastric cancer; is it possible for virtual non-enhanced images to replace true non-enhancedimages?Objective:This study aims to determine whether virtual nonenhanced images (VNE) derived from dual-energy computed tomography(CT) can replace true non-enhanced images in patients with gastric cancer. And to evaluate radiation dose reduction by omitting a true non-enhanced (TNE) scan.Methods:55patients(41men,19women; mean age59.38years; range23～81years) suspected gastric cancers were included in the study between December2011and February2013. Patients with gastric cancers underwent multidetector CT including nonenhanced and contrast-enhanced images obtained at the arterial phase and portal phase using the dual-energy technique. CT attenuation values, size and SNR for VNE and TNE images were compared. Image quality, noise, artifacts, and acceptability for virtual non-enhanced images compared to true non-enhanced images were rated. CTDIvol were calculated.Results:1. Mean CT attenuation values, thickness of gastric tumors and enlarged lymph nodes of virtual nonenhanced and true non-enhanced images were simila.(P<0.05). Lower noise was found for virtual nonenhanced images than that for true non-enhanced images images (P<0.05). There was no difference between the VNE images derived from the arterial(VNEA) and VNE images derived from the portal venous phases(VNEP)(P>0.05). Lower SNR was found for TNE than that for VNE images of gastric tumors.And the SNR of enlarged lymph nodes of TNE and VNE were similar.2. Virtual non-enhanced images showed good image quality, mild noise, mild artifacts, and good acceptability compared to true non-enhanced images.3. Small stones were detected better on true non-enhanced images than on virtual non-enhanced images.The other stones were similar.4. There was no difference between TNE and VNE in detectable primary lesions at the stomach wall gross, a blurred fat plane around the lesion, infiltration of adjacent organs, formation of liver or peritoneal metastasis and numbers of enlarged lymph nodes.5. Mean radiation dose reductions by omitting true nonenhanced images were32.41%in the virtual triple protocol.Conclusion:Image qualities of virtual non-enhanced images are comparable to those of true non-enhanced images with consequent saving radiation dose. Part Three Additional value of dual-energy CT in histological grading of gastric cancersObjective:To investigate the feasibility of DECT for gastric cancers with different histological grades.Methods:55patients(41men,19women; mean age59.38years; range23-81years) suspected gastric cancers were included in the study between December2011and February2013. Patients with gastric cancers underwent multidetector CT including nonenhanced and contrast-enhanced images obtained at the arterial phase and portal phase using the dual-energy technique. For the quantitative analysis, two investigators measured the following parameters of the tumors in the nonenhanced arterial phase and portal phase:CT attenuation value in Hounsfield units (HU), iodine concentration (mg/ml) and the iodine concentration aorta of same level. Normalized iodine concentration(NIC) was obtained through counting.Pathological results were used for a final diagnosis.Results:1. CT attenuation value in Hounsfield units (HU), arterial enhanced HU non-enhanced HU and portal enhanced HU-non-enhanced HU were similar.(P>0.05).2. The NIC were significantly different in the portal phase with different histological grades(P=0.009), while the NIC in the arterial phase was not significantly different with different histological grades (P=0.326).3. Significant differences were found for NIC between the metastasis lymph nodes and the non-lymph nodes both in arterial phase and in the portal phase.4. Both of different histological grades gastric cancer spectrum curve were the same in the arterial phase. Both of different histological grades gastric cancer spectrum curve were descent tendency in the portal phase,there are difference between them especially during the40kev to80kev.The poor differentiation gastric cancer spectrum curve were above well differentiation gastric carcinoma.5.The mean slop rates of the poor differentiation gastric cancer was higher than those of well differentiation gastric carcinoma during the portal phase.But there was no difference with different histological grades.Conclusion:Dual-energy CT using a quantitative analytic methodology can be used to differentiate between the poor differentiation gastric cancer and well differentiation gastric carcinoma.