Radiation Dose Reduction in Head and Neck Computed Tomography Angiography.

BACKGROUND AND AIM: The study aims to investigate the feasibility of further radiation dose reduction via the application of a high iodine delivery rate combined with automatic current modulation technology (high noise index) in head and neck computed tomography angiography. METHODS: Sixty-four patients who underwent routine head and neck computed tomographic angiography were randomly divided into two groups: a low-dose group of 32 cases and an ultra-low-dose group of 32 cases. The same image reconstruction technique was applied in both groups using the 50% adaptive statistical iterative reconstruction method. Quantitative and qualitative image quality assessment of the carotid artery, computed tomographic dose index volume, dose length product, and effective dose of the two groups were analyzed. RESULTS: The two groups were not significantly (P>0.05) different in age, gender, and body mass index. Significant (P<0.001) reduction of radiation dose was observed in all the parameters of computed tomographic dose index volume (18.12%), dose length product (19.91%), and effective dose (19.84%) in the ultra-low-dose group. Quantitative and qualitative image assessment produced similar results between the two groups, except for the higher mean vascular computed tomographic values found in the ultra-low dose group. CONCLUSION: Application of a higher iodine delivery rate combined with automatic current modulation technology (high noise index) in an existing low tube voltage protocol can further decrease the radiation dose and the total volume of contrast agent while maintaining similar image quality for patients undergoing computed tomography angiography of the head and neck, which can be recommended as the conventional scanning method.

Perfusion Computer Tomography Assessment of the Effect of Angiotensin II On Blood Flow Distribution in Rabbits with Intrarenal VX2 Tumors.

BACKGROUND/AIMS: Unlike other organs, which only have one set of capillary network, the renal microvasculature consists of two sets of capillary network series connected by efferent arterioles. Angiotensin II constricts the efferent glomerular artery. Hence, renal tumor blood flow (BF) distribution may be different from tumors in other organs. This study aims to investigate the effects of angiotensin II on the hemodynamics of intrarenal VX2 tumors using perfusion computed tomography(CT). METHODS: Twenty-four male New Zealand white rabbits were randomly divided into three groups: groups A (blank controls), group B (negative controls), and group C (angiotensin II-treated animals). Group B and C were established to the model of intrarenal VX2 tumors. Furthermore, perfusion CT of the kidney was performed in each group. Prior to perfusion CT scan in group C, the mean arterial blood was elevated to 150-160 mmHg by angiotensin II. The BF, blood volume (BV), mean transit time (MTT), capillary permeability-surface area product (PS), and relative permeability-surface area product (RPS) of tumors and renal tissues were calculated. RESULTS: Compared with normal renal cortex tissues in group A, the BF, BV and PS values of tumors in group B were significantly lower, MTT was prolonged and RPS increased. Compared with group B, only the RPS of these tumors increased from 83.23 ± 29.17% to 120.94 ± 31.84% by angiotensin II infusion. Angiotensin II significantly increased the RPS value of the renal cortex distant from the tumor (CDT) and the right renal cortex (RRC). CONCLUSIONS: Perfusion CT can accurately observe the influence of angiotensin II on normal and tumor BF in kidneys. This clarifies the effect of angiotensin II on intrarenal tumor hemodynamics.

Automatic spectral imaging protocol selection combined with iterative reconstruction can enhance image quality and decrease radiation and contrast dosage in abdominal CT angiography.

PURPOSE: To investigate the effect of automatic spectral imaging protocol selection (ASIS) and adaptive statistical iterative reconstruction (ASIR) technology in reducing radiation and contrast dosage. METHODS: Sixty-four patients were randomly divided into two groups for abdominal computed tomography (CT): the experiment group with ASIS plus 50% ASIR and the control with 120 kVp voltage. RESULTS: The CT dose-index volume decreased by 23.68 and 23.57% and the dose-length product dropped by 25.59 and 18.45% in the arterial and portal venous phases, respectively, in the experiment than control group. The contrast dose was reduced by 16.86% in the experiment group. In the 55 keV + 50% ASIR group, the arterial contrast-to-noise ratio and scores were significantly (P < 0.05) higher than in the control group in the arterial phase while the portal contrast-to-noise ratio and scores were not significantly different between the two groups (P > 0.05). CONCLUSION: The ASIS technique plus 50% ASIR can enhance image quality of the abdominal structures while decreasing the radiation and contrast dosage compared with the conventional scan mode.

The optimal monochromatic spectral computed tomographic imaging plus adaptive statistical iterative reconstruction algorithm can improve the superior mesenteric vessel image quality.

OBJECTIVE: To investigate the effect of the optimal monochromatic spectral computed tomography (CT) plus adaptive statistical iterative reconstruction on the improvement of the image quality of the superior mesenteric artery and vein. MATERIALS AND METHODS: The gemstone spectral CT angiographic data of 25 patients were reconstructed in the following three groups: 70KeV, the optimal monochromatic imaging, and the optimal monochromatic plus 40%iterative reconstruction mode. The CT value, image noises (IN), background CT value and noises, contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and image scores of the vessels and surrounding tissues were analyzed. RESULTS: In the 70KeV, the optimal monochromatic and the optimal monochromatic images plus 40% iterative reconstruction group, the mean scores of image quality were 3.86, 4.24 and 4.25 for the superior mesenteric artery and 3.46, 3.78 and 3.81 for the superior mesenteric vein, respectively. The image quality scores for the optimal monochromatic and the optimal monochromatic plus 40% iterative reconstruction groups were significantly greater than for the 70KeV group (P<0.05). The vascular CT value, image noise, background noise, CNR and SNR were significantly (P<0.001) greater in the optimal monochromatic and the optimal monochromatic images plus 40% iterative reconstruction group than in the 70KeV group. The optimal monochromatic plus 40% iterative reconstruction group had significantly (P<0.05) lower image and background noise but higher CNR and SNR than the other two groups. CONCLUSION: The optimal monochromatic imaging combined with 40% iterative reconstruction using low-contrast agent dosage and low injection rate can significantly improve the image quality of the superior mesenteric artery and vein.

A Comparison of the Image Quality and Radiation Dose With Routine Computed Tomography and the Latest Gemstone Spectral Imaging Combination of Different Scanning Protocols in Computed Tomography Angiography of the Kidney.

OBJECTIVE: The objective of our study was to compare the image quality and radiation dose of computed tomography angiography (CTA) of the kidney in patients with different body mass indexes using routine CT and the latest gemstone spectral imaging (GSI) combination of different scanning protocols with the adaptive statistical iterative reconstruction 2.0 algorithm. METHODS: A total of 90 patients who had undergone a CTA of the kidney were divided into 3 groups (A, B, and C), with 30 patients in each group. Group A underwent a routine CT examination, whereas groups B and C underwent GSI with different scanning protocols. All images were restructured using the adaptive statistical iterative reconstruction 2.0. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all images were calculated when the kidney CTA was completed. Each subjective image evaluation used a 5-point scoring method and was conducted by 2 independent radiologists. The CT dose index of volume and the dose-length product were recorded, and the mean value was calculated. The dose-length product was converted to the effective dose. All data were compared with a 1-way analysis of variance. RESULTS: The SNR, CNR, and subjective image quality in group A were significantly lower than those in groups B and C (P < 0.01). There were no significant differences in SNR, CNR, and subjective image quality between groups B and C. The effective dose of group C decreased by 46.05% and 15.03% relative to those of groups A and B, respectively (P < 0.01). CONCLUSIONS: The latest GSI with different scanning protocols can more effectively reduce the radiation dose than can the routine CT scan mode for a kidney CTA while still maintaining diagnostic image quality.