Comparison of the effects of varying tube voltage and iodinated concentration on increasing the iodinated radiation dose in computed tomography.

PURPOSE: To compare the effects of tube voltage and iodinated concentration on increasing the iodinated radiation dose in computed tomography (CT). MATERIAL AND METHODS: Water and iodinated materials were inserted in an anthropomorphic thorax phantom. Helical CT scans were performed with tube voltages of 80 and 120 kV. Monte Carlo simulation of radiation doses in CT images was used to study the radiation dose profiles. The radiation doses at different iodine to water ratios in images were calculated from cumulative radiation doses for iodine and water at each iodine concentration, tube voltage, and peripheral/central location. A radiation dose ratio from 80 to 120 kV was calculated from cumulative radiation doses at the same iodine concentration. RESULTS: The iodinated radiation doses with small and large phantoms were 1.56-2.04 and 1.61-1.82 times higher at 80 kV and 1.55-2.23 and 1.22-1.79 times higher at 120 kV than those in water. In the central portion, the iodinated radiation dose ratio decreased by 1.14-0.75 and 1.20-0.93 times at 80 kV and 1.29-1.23 and 1.17-1.23 times at 120 kV with increasing iodinated concentrations. In the peripheral portion, the iodinated radiation dose was slightly higher for 80 kV than for 120 kV. In the central portion, the ratio decreased with increasing iodinated concentration. CONCLUSION: The increase in iodinated radiation dose caused by photoelectric absorption was greater with increased iodine load than with lower tube voltage.

A New Method of Intracranial Aneurysm Modeling for Stereolithography Apparatus 3D Printer: The "Wall-Carving Technique" Using Digital Imaging and Communications in Medicine Data.

OBJECTIVE: To assess the ability of the "wall-carving (WC) image technique", which uses vascular images from 3-dimensional digital subtraction angiograms (3DDSAs). Also, to verify the accuracy of the resulting 3D-printed hollow models of intracranial aneurysms. METHODS: The 3DDSA data from 9 aneurysms were processed to obtain volumetric models suitable for the stereolithography apparatus. The resulting models were filled with iodinated contrast media. 3D rotational angiography of the models was carried out, and the aneurysm geometry was compared with the original patient data. The accuracy of the 3D-printed hollow models' sizes and shapes was evaluated using the nonparametric Wilcoxon signed-rank test and the Dice coefficient index. RESULTS: The aneurysm volumes ranged from 34.1 to 4609.8 mm3 (maximum diameters 5.1-30.1 mm), and no statistically significant differences were noted between the patient data and the 3D-printed models (P = 0.4). Shape analysis of the aneurysms and related arteries indicated a high level of accuracy (Dice coefficient index value: 88.7%-97.3%; mean ± SD: 93.6% ± 2.5%). The vessel wall thickness of the 3D-printed hollow models was 0.4 mm for the parent and 0.2 mm for small branches and aneurysms, almost the same as the patient data. CONCLUSIONS: The WC technique, which involves volume rendering of 3DDSAs, can provide a detailed description of the contrast enhancement of intracranial vessels and aneurysms at arbitrary depths. These models can provide precise anatomic information and be used for simulations of endovascular treatment.

Technical Note: Performance comparison of ultra-high-resolution scan modes of two clinical computed tomography systems.

PURPOSE: Two ultra-high-resolution (UHR) computed tomography (CT) scanners are clinically available. One is achieved by a CT system with a 0.25 mm × 160 row detector (Detector-UHR), whereas the other is with a 0.6 mm × 32 row detector with in-plane comb filtering in a dual source CT (Comb-UHR). We compared radiation dose efficiencies of the two UHR modes to that of a routine scan mode (RS), using physical image quality measures for an assumed condition of abdominal CT angiography (CTA). METHODS: A wire phantom, a 300-mm cylindrical water bath phantom, and a microdisk phantom were used for measuring the modulation transfer function (MTF), noise power spectrum (NPS), and slice sensitivity profiles (SSP), respectively, at CTDIvol of 20 mGy. Images with minimal slice thicknesses were reconstructed by filtered back projection methods. System performance functions (SPF2 ) based on the prewhitening theorem were calculated by dividing MTF2 by NPS measurements. The ideal observer's detectability index (d'2 ) was also estimated for a task corresponding to a 1-mm diameter vessel. Furthermore, a bar-pattern phantom placed in a water phantom resembling an adult abdomen was scanned, and the visibility of the bars was observed. RESULTS: System performance function (SPF2 ) results showed that Comb-UHR has a 70% dose efficiency compared to RS and provides better than twofold SPF2 compared to Detector-UHR. The d'2 values of Detector-UHR, Comb-UHR, and RS were 6.5, 14.7, and 16.0, respectively. Although the bar-pattern phantom images were consistent with the SPF results, bar widths < 1.0 mm for Detector-UHR and < 0.75 mm for Comb-UHR and RS were not resolved. CONCLUSIONS: Though both the UHR modes exhibited system performances extending to 2.6 cycles/mm, they appeared not to be advantageous compared to RS in the conditions applicable to abdominal CTA, because of their insufficient dose efficiencies.

Novel contrast-injection protocol for high-resolution abdominal CT-angiography: vascular visualization improvement with vasodilator.

PURPOSE: To evaluate the usefulness of a novel contrast-injection protocol for high-resolution abdominal computed tomography angiography (CTA) using nitroglycerin (NTG). METHODS: Abdominal CTA was performed in 80 patients using two 64-detector-row CT scanners. Forty patients were examined after administration of sublingual NTG (NTG group), while 40 were examined without NTG administration (non-NTG group). Arterial phase images were acquired with maximum intensity projection and volume rendering. Reduction rates: vessel cross-sectional areas ratio of 10 cm distal to origin at the superior mesenteric artery, contrast enhancements, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were assessed. Three reviewers evaluated degree of depiction of the peripancreatic vasculature using a four-point scale (1 = poor, 4 = excellent). RESULTS: Reduction rates were significantly lower in the NTG group (P < 0.001), while there were no significant differences in contrast enhancements, SNR, or CNR between groups. Visual evaluation results of the NTG group were significantly better than those of the non-NTG group (P < 0.01). CONCLUSION: Abdominal CTA using NTG improved visualization of the abdominal peripheral vessels. This improved arterial view may be beneficial for preoperative evaluation of the arterial anatomy.

Left superior pulmonary venous thrombosis complicated with splenic infarction after video-assisted thoracoscopic left upper lobectomy.

A 72-year-old man underwent video-assisted thoracoscopic left upper lobectomy for small cell lung cancer. After 16 days, he experienced epigastric abdominal pain and vomiting, and was taken by ambulance to our hospital. Contrast-enhanced computed tomography (CT) showed a propagation of thrombus in the stump of the left superior pulmonary vein (LSPV) complicated with splenic infarction. The patient received anticoagulation therapy with heparin and warfarin, and further progression of the thrombus or any systemic embolic event was not observed during hospitalization. Here, we report a patient presenting with LSPV thrombosis complicated with splenic infarction after video-assisted thoracoscopic surgery (VATS), and describe several months follow-up CT imaging results after administration of an oral anticoagulation therapy. .