Development of the Split-Bolus Pulmonary Arteriovenous Separating Computed Tomography Angiography Protocol Based on Time Enhancement Curve for Lung Cancer Surgery.

OBJECTIVE: We devised a split-bolus injection and imaging protocol for pulmonary artery and vein separation computed tomography (CT) angiography based on time enhancement curve characterization. Furthermore, we aimed to evaluate the contrast enhancement effect and success rate of blood vessel separation between the pulmonary artery and vein of this proposed protocol. METHODS: In this study, 102 patients (45 patients with the standard protocol and 57 patients with the proposed protocol) who underwent pulmonary arteriovenous computed tomography angiography were included. The CT values of various vessels, CT value difference between the pulmonary trunk and left atrium, and coefficient of variation in pulmonary arteries and veins were obtained from images of the standard and proposed protocols. RESULTS: The CT values in the proposed protocol for the pulmonary trunk were significantly higher than those in the standard protocol (487.3 [415.5-546.9] HU vs. 293.0 [259.0-350.0] HU, P < 0.01). The CT value difference between the pulmonary trunk and left atrium in the proposed protocol was significantly higher than that in the conventional protocol (211.3 [158.0-265.7] HU vs. 32 [-30.0-55.0] HU, P < 0.01). The coefficient of variation in the proposed protocol was 0.08 (0.06-0.10) and 0.09 (0.08-0.11) in pulmonary arteries and 0.08 (0.06-0.09) and 0.09 (0.07-0.12) in pulmonary veins, respectively. CONCLUSIONS: The proposed protocol achieved separation between the pulmonary artery and vein in many patients, making it useful for the preoperative assessment of individual thoracic anatomy.

Can Three-Dimensional T1-weighted MR Imaging Visualize the Vascular Lumen after Carotid Artery Stenting?

PURPOSE: We aimed to evaluate the quality of various 3D T1-weighted images (T1WIs) of the stent lumen using a carotid stent phantom and determine the suitable T1WI sequence for visualization of the stent lumen after carotid artery stenting. METHODS: The carotid stent phantom consisted of polypropylene tubes that mimicked common carotid arteries with and without stenting. On 1.5T and 3.0T MRI scanners, transverse T1WIs of the carotid stent phantom were obtained using 3D turbo spin-echo (TSE), 3D fast field-echo (3D-FFE), and 3D turbo field echo volumetric interpolated breath-hold examination (VIBE) under clinical conditions. The signal intensity ratio (SIR) was determined using the mean signal intensity of the stent lumen (SIstent) divided by the lumen without a stent in each T1WI. The SNR of the stent lumen (SNRstent) was calculated from SIstent divided by the standard deviation of the uniform region near the stent lumen. RESULTS: The 3D-FFE and VIBE had higher SNRstent than other T1WIs and clearly visualized the stent lumen. The 3D-TSE had the lowest SIR and SNRstent, preventing stent lumen visualization. CONCLUSION: T1WIs obtained using 3D-FFE and VIBE allows stent lumen visualization.

Delineation of the internal iliac vein using MRI with true FISP sequence in patients with locally recurrent rectal cancer: A pilot study using CT/MRI fusion.

PURPOSE: This study assessed the feasibility of using three-dimensional (3D) models of intrapelvic vascular patterns constructed using computed tomography (CT) and magnetic resonance imaging (MRI) fusion data for preoperative planning in patients with locally recurrent rectal cancer. METHODS: Eleven patients scheduled for pelvic exenteration were included. The 3D fusion data of the intrapelvic vessels constructed using CT and MRI with true fast imaging with steady-state precession sequence (True FISP) were evaluated preoperatively. Contrast ratios (CR) between the piriformis muscle and the intrapelvic vessels were calculated to identify a valid modality for 3D modeling and creating CT/MRI fusion-reconstructed volume-rendered images. RESULTS: The CR values of the internal and external iliac arteries were significantly higher on CT images than MR images (CT vs. MRI; 0.63 vs. 0.45, p < 0.01). However, the CR value of the internal iliac vein was significantly higher on MR than CT images (CT vs. MRI; 0.23 vs. 0.55, p < 0.01). CONCLUSIONS: MRI with True FISP yielded high signal-to-noise ratios and aided in delineating the internal iliac vein around the piriformis muscle. More precise 3D models can be constructed using this technique in the future to aid in the resection of locally recurrent rectal cancer.

Utility of ultrasonography for predicting indications for tolvaptan in patients with autosomal dominant polycystic kidney disease.

PURPOSE: Tolvaptan is the first approved treatment for autosomal dominant polycystic kidney disease (ADPKD) that targets a mechanism directly contributing to the development and growth of renal cysts. We investigated the ability of ultrasonography to predict total kidney volume (TKV) of 750 mL or more, which is an indication for tolvaptan therapy in patients with ADPKD. METHODS: A total of 46 patients with ADPKD were evaluated. The most statistically appropriate measurement based on ultrasonography for predicting TKV determined by computed tomography (CT) was assessed. RESULTS: TKV determined by CT was 796.8 (508.8-1,560.3) mL. The median length, anteroposterior distance, and mediolateral distance determined using ultrasonography were 15.7 cm, 7.6 cm, and 7.6 cm in the left kidney, and 13.4 cm, 6.9 cm, and 7.2 cm in the right kidney, respectively. Multivariate regression analysis showed that total kidney length (left and right) [variance inflation factor (VIF), 9.349] and total mediolateral distance (left and right) (VIF, 3.988) were independently associated with TKV. The correlation (r) between the logarithm of TKV determined by CT and total mediolateral distance determined using ultrasonography was 0.915 (p < 0.001). The linear regression equation was log (total kidney volume) = 1.833 + 0.075 × total mediolateral distance (left and right) based on ultrasonography. The area under the receiver operating characteristic curve for total mediolateral distance determined using ultrasonography to predict TKV of 750 mL or more was 0.989. Using the total mediolateral distance cut-off value of 14.2 cm, the sensitivity and specificity were 96.0% and 100.0%, respectively. CONCLUSION: Total mediolateral distance determined using ultrasonography can predict TKV in patients with ADPKD.

[Usefulness of Combining Post-processing Scatter Correction and an Anti-scatter Grid in Chest Standing Radiography].

PURPOSE: The aim of this study was to evaluate the usefulness of combining post-processing scatter correction (IG) and an anti-scatter grid (RG) in chest radiography. METHOD: To determine the combination protocol (Hyb) that was closed to RG 12:1 (RG12), we measured the content rate of scattered radiation for each combination (RG12, IG12, RG3-12+IG3-12). Task-based modulation transfer function (MTF_Task) and SDNR were evaluated using RG12, IG12, and Hyb. Additionally, seven radiologists performed visual evaluation by using chest phantom. RESULT: The protocol of Hyb was RG8+IG3. In SDNR, Hyb (RG8+IG3) was equal to or higher than RG12, and MTF_Task was equal in all grid systems. Hyb (RG8+IG3) was significantly superior to RG12 in visual evaluation. CONCLUSION: The combining post-processing scatter correction should be useful for improving inspection throughput and reducing the risk of grid's damage.

[Examination of the Maximum Brightness of the Monitor Suitable for Radiological Technologists' Interpretation Assistance and Image Inspection].

The purpose of this study is to examine the maximum brightness of the monitor, which is suitable for radiological technologists' (hereinafter referred to as technicians) interpretation assistance and image inspection. The signal detection ability was evaluated by receiver operating characteristic (ROC) analysis using a chest X-ray image with a simulated nodule. In order to examine the ease of observation and the effect on the subjective evaluation by changing the maximum brightness, evaluation was performed by the normalized ranking method using chest X-ray images. ROC experiments were performed using images with and without simulated nodules in the chest phantom. There was no significant difference in detectability by changing the maximum brightness (p>0.05), but the average area under the curve (AUC) was higher at 350 cd/m2 than at 100 cd/m2 and 170 cd/m2. A normalized ranking method was performed focusing on simulated nodules on chest X-ray images. In the least significant difference (l.s.d.) method, there was a significant difference between the maximum luminance, and the higher the maximum luminance, the better the evaluation. From these results, the change in the maximum brightness did not significantly affect the signal detection ability of the technician's chest X-ray image, but the higher the maximum brightness, the easier it was to observe and the higher the subjective evaluation. It has been reported that the higher the maximum brightness, the shorter the signal recognition time, and a monitor with a high maximum brightness may lead to more efficient image inspection by a technician. From the results of this study, it is considered appropriate to use a medical liquid crystal display (LCD) monitor with a maximum brightness of 350 cd/m2 for the technician's interpretation assistance and image inspection.

[Effects of Iterative Reconstruction on Image Quality of Pediatric Body Computed Tomography Images].

This study evaluated the effects of three types of hybrid iterative reconstruction (IR) on image quality of pediatric body computed tomography images. The image quality components evaluated were noise power spectrum (NPS), task-based modulation transfer function (TTF), and system performance function (SPF). As the IR strength was increased while reducing the radiation dose, the NPS increased in a low-frequency range and the TTF decreased in low-contrast regions. In the low-contrast regions, the calculated SPF decreased over the entire frequency range. Alternatively, in the high-contrast regions, the SPF decreased in the low-frequency regions and increased in the high-frequency regions. The radiation dose reduction using the hybrid IR resulted in the deterioration of the image quality in the low-contrast regions and changes in the spatial frequency characteristics in the high-contrast regions.

[Comparison of Detectability for the New Image Processing and Conventional Image Processing by ROC Analysis: A Phantom Study of Chest Radiography].

The purpose of this study is to compare the detectability of diseases the new image processing and the conventional image processing by receiver operating characteristic (ROC) analysis and to show the usefulness of the new image processing. Radiographs with and without nodular cancer models in the chest phantom were used for observation samples. Totally 200 radiographs were evaluated by 10 radiological technologists (each readers had over 20 years or under 4 years of experience). The mean area under the curve (AUC) calculated from the over 20 years group was 0.754 for the new processing and 0.771 for the conventional processing (p value=0.651, 95% confidence interval=-0.084/0.049 (lower bound/upper bound)). On the other hand, the average AUC calculated from under 4 years group was 0.819 for the new processing and 0.678 for the conventional processing (p value= 0.041, 95% confidence interval=0.019/0.262 (lower bound/upper bound)). New image processing provides high detectability in less than 4 years group compared to conventional processing.

[Imaging Parameter Optimization of 3D Phase Contrast-MRA to Reduce Susceptibility-artifact and Radiofrequency-shielding around the Intracranial Stent].

The purpose of this study was to evaluate the degree of signal attenuation generated around the stent by the susceptibility artifacts and radiofrequency (RF) shielding in phase contrast-magnetic resonance angiography (PCA) images and construct optimal PCA imaging parameters for intracranial stent lumen images. The two types of PCA images of stents (Neuroform, Enterpraise II) placed in the vascular flow phantom were imaged with different the flip angle (FA) and echo time (TE). Each original image of the vascular flow phantom was reconstructed into a coronal multiplanar reconstruction (MPR) image and a profile curve along the long axis of the stent was calculated. The reduction of in-stent signal was assessed by relative in-stent signal (RIS) calculated by comparing intra-stent signal intensity to the reference tube in the original images. When the TE was 2.3 ms, the profile curve was the highest signal intensity. However, RIS had not changed by the extension of TE. When the FA was high, the RIS showed a high value, but when it exceeded 25 degrees, the signal attenuated in the distal part of the slab.The susceptibility artifacts and RF shielding generated around the stent can be reduced by the shortest TbE (2.3 ms) and 20 degrees of FA in the PCA imaging.