Wataru Fukumoto

Radiation dose reduction at coronary artery calcium scoring by using a low tube current technique and hybrid iterative reconstruction.

Purpose The aim of this study was to compare the accuracy of coronary artery calcium scoring (CACS) on cardiac computed tomographic images using hybrid iterative reconstruction (hIR) and a low tube current as well as on images acquired with a filtered back projection (FBP) algorithm and a normal tube current. Subjects and Methods Patients (N = 77) with suspected coronary artery disease were subjected to 2 CACS evaluations based on their Agatston, volume, and mass scores. One CACS evaluation was performed on images obtained with a 364-mA tube current and reconstructed with FBP; the other was performed on images obtained with a 73-mA tube current and reconstructed with hIR at iDose4. All scans were performed with the prospective electrocardiogram-triggered method using a 256-slice computed tomographic scanner (Brilliance iCT; Philips). We assessed agreement between calcium scores obtained with FBP and with IR using the percentage difference and Bland-Altman analysis. Results The effective radiation doses for CACS at 80 mA s with FBP and at 16 mA s with IR were 1.20 and 0.24 mSv, respectively (k = 0.014). The mean Agatston, volume, and mass scores at 80 mA s with FBP as well as at 16 mA s with IR were 390.7, 146.5, and 63.2 as well as 377.7, 142.5, and 62.2, respectively. The percentage difference between FBP and hIR for the Agatston, volume, and mass score was 20.7%, 20.7%, and 27.1%, respectively. Bland-Altman analysis showed that there was no systemic bias. Conclusions The radiation dose for CACS can be reduced at a low tube current and hIR without affecting the calcium score.

Coronary Artery Stent Evaluation with Model-based Iterative Reconstruction at Coronary CT Angiography

RATIONALE AND OBJECTIVES This study aims to compare the image quality of coronary artery stent scans on computed tomography images reconstructed with forward projected model-based iterative reconstruction solution (FIRST) and adaptive iterative dose reduction 3D (AIDR 3D). MATERIALS AND METHODS Coronary computed tomography angiography scans of 23 patients with 32 coronary stents were used. The images were reconstructed with AIDR 3D and FIRST. We generated computed tomography attenuation profiles across the stents and measured the width of the edge rise distance and the edge rise slope (ERS). We also calculated the stent lumen attenuation increase ratio (SAIR) and measured visible stent lumen diameters. Two radiologists visually evaluated the image quality of the stents using a 4-point scale (1 = poor, 4 = excellent). RESULTS There was no significant difference in the edge rise distance between the two reconstruction methods (P = 0.36). The ERS on FIRST images was greater than the ERS on AIDR 3D images (325.2 HU/mm vs 224.4 HU/mm; P <0.01). The rate of the visible stent lumen diameter compared to the true diameter on FIRST images was higher than that on AIDR 3D images (51.4% vs 47.3%, P <0.01). The SAIR on FIRST images was lower than the SAIR on AIDR 3D images (0.19 vs 0.30, P <0.01). The mean image quality scores for AIDR 3D and FIRST images were 3.18 and 3.63, respectively; the difference was also significant (P <0.01). CONCLUSION The image quality of coronary artery stent scans is better on FIRST than on AIDR 3D images.

Transarterial therapy of hepatocellular carcinoma fed by the right renal capsular artery.

PURPOSE To evaluate the characteristics of hepatocellular carcinomas (HCCs) fed by the right renal capsular artery and to assess the tumor response and complications in patients treated with transarterial therapy via the renal capsular arteries with or without other extrahepatic arteries and/or intrahepatic arteries. MATERIALS AND METHODS Between March 2006 and May 2012, 24 lesions in 19 patients were treated by transcatheter arterial chemoembolization (23 sessions), transcatheter arterial embolization (two sessions), or transcatheter arterial infusion (one session), with HCCs fed by the right renal capsular artery with or without intrahepatic arteries and/or other collateral arteries. Other intrahepatic lesions were concurrently treated if needed. RESULTS Tumor size ranged from 10 mm to 107 mm (mean, 30.5 mm). Of the 24 tumors, 12 were located in segment VI, 10 in segment VII, one in the posterior segment, and one in the anterior segment after posterior segment resection. Severe complication occurred in four patients: liver abscess (n = 2), pleural effusion (n = 1), and duodenal ulcer (n = 1). Pleural effusion might be related to chemoembolization via the right renal capsular artery. A complete response was obtained in six sessions and a partial response in eight; 10 sessions were associated with stable disease and two with progressive disease. CONCLUSIONS Precise renal capsular artery knowledge would facilitate successful and safe transarterial therapy for HCCs fed by the renal capsular arteries.

DNA damage in lymphocytes induced by cardiac CT and comparison with physical exposure parameters.

ObjectivesTo investigate whether physical exposure parameters such as the dose index (CTDI), dose length product (DLP), and size-specific dose estimate (SSDE) are predictive of DNA damage.MethodsIn vitro, we scanned a phantom containing blood samples from five volunteers at CTDI 50, 100, and 150 mGy. One sample was not scanned. We also scanned samples in three different-size phantoms at CTDI 100 mGy. In vivo, we enrolled 45 patients and obtained blood samples before and after cardiac CT. The γ-H2AX foci were counted.ResultsIn vitro, in the control and at CTDI 50, 100, and 150 mGy, the number of γ-H2AX was 0.94 ± 0.24 (standard error, SE), 1.28 ± 0.30, 1.91 ± 0.47, and 2.16 ± 0.20. At SSDE 180, 156, and 135 mGy, it was 2.41 ± 0.20, 1.91 ± 0.47, and 1.42 ± 0.20 foci/cell. The γ-H2AX foci were positively correlated with the radiation dose and negatively correlated with the body size. In vivo, the γ-H2AX foci were significantly increased after CT (from 1.21 ± 0.19 to 1.92 ± 0.22 foci/cell) and correlated with CTDI, DLP, and SSDE.ConclusionsDNA damage was induced by cardiac CT. There was a correlation between the physical exposure parameters and γ-H2AX.Key Points• DNA damage was induced by radiation exposure from cardiac CT.• The γ-H2AX foci number was correlated with the CT radiation dose.• Physical exposure parameters reflect the DNA damage by CT radiation exposure.

CT fluoroscopy-guided percutaneous drainage: comparison of the one step and the Seldinger techniques

Abstract Objective: To evaluate the one step technique compared with the Seldinger technique in computed tomography (CT) fluoroscopy-guided percutaneous drainage of abdominal and pelvic abscess. Material and methods: Seventy-six consecutive patients (49 men, 27 women; mean age 63.5 years, range 19–87 years) with abdominal and pelvic abscess were included in this study. Drainages were performed with the one step (n = 46) and with the Seldinger (n = 48) technique between September 2012 and June 2014. Results: The technical success and clinical success rates were 95.8% and 93.5%, respectively, for the one step group, and 97.8% and 95.7%, respectively, for the Seldinger group. The mean procedure time was significantly shorter with the one step than with the Seldinger method (15.0 ± 4.3 min, range 10–29 min vs. 21.0 ± 9.5 min, range 13–54 min, p < .01). The mean abscess size and depth were 73.4 ± 44.0 mm and 42.5 ± 19.3 mm, respectively, in the one step group, and 61.0 ± 22.8 mm and 35.0 ± 20.7 mm in the Seldinger group. Conclusion: The one step technique was easier and faster than the Seldinger technique. The effectiveness of both techniques was similar for the CT fluoroscopy-guided percutaneous drainage of abdominal and pelvic abscess.

Blood Flow Redistribution Using the AMPLATZER Vascular Plug 4 before Distal Pancreatectomy with en Bloc Celiac Axis Resection

eliminated the vessel tortuosity, which may have also facilitated the selection of the target vessels. Differences in the caliber and pressures of the selected arteries were not measured because of their diminutive calibers. The following should be considered while choosing the balloon-assisted flow diversion technique for catheterization. Currently available peripheral balloon catheters are relatively inflexible, increasing risk of vascular spasm or dissection, particularly in patients with tortuous vessels and patients receiving antiangiogenesis therapy. Also, stasis associated with balloon inflation could cause thrombosis in the parent vessel. Intravenous heparin administration and reduction of the balloon inflation time reduce the risk of thrombosis. Finally, the balloon cost may be balanced by the cost of using additional catheters and wires. In conclusion, temporary distal balloon occlusion might be a useful alternative technique for the catheterization and subsequent embolization of small, challenging vessels, making it a potentially valuable tool in cases of challenging selective catheterization.

Neural Network Convolution (NNC) for Converting Ultra-Low-Dose to "Virtual" High-Dose CT Images.

To reduce radiation dose in CT, we developed a novel deep-learning technique, neural network convolution (NNC), for converting ultra-low-dose (ULD) to “virtual” high-dose (HD) CT images with less noise or artifact. NNC is a supervised image-based machine-learning (ML) technique consisting of a neural network regression model. Unlike other typical deep learning, NNC can learn thus output desired images, as opposed to class labels. We trained our NNC with ULDCT (0.1 mSv) and corresponding “teaching” HDCT (5.7 mSv) of an anthropomorphic chest phantom. Once trained, our NNC no longer require HDCT, and it provides “virtual” HDCT where noise and artifact are substantially reduced. To test our NNC, we collected ULDCT (0.1 mSv) of 12 patients with 3 different vendor CT scanners. To determine a dose reduction rate of our NNC, we acquired 6 CT scans of the anthropomorphic chest phantom at 6 different radiation doses (0.1–3.0 mSv). Our NNC reduced noise and streak artifacts in ULDCT substantially, while maintaining anatomic structures and pathologies such as vessels and nodules. With our NNC, the image quality of ULDCT (0.1 mSv) images was improved at the level equivalent to 1.1 mSv CT images, which corresponds to 91% dose reduction.

Chromosomal Abnormalities in Human Lymphocytes after Computed Tomography Scan Procedure

The incidence of chromosomal abnormalities and cancer risk correlates well with the radiation dose after exposure to moderate- to high-dose ionizing radiation. However, the biological effects and health risks at less than 100 mGy, e.g., from computed tomography (CT) have not been ascertained. To investigate the biological effects of low-dose exposure from a CT procedure, we examined chromosomal aberrations, dicentric and ring chromosomes (dic+ring), in peripheral blood lymphocytes (PBLs), using FISH assays with telomere and centromere PNA probes. In 60 non-cancer patients exposed to CT scans, the numbers of dicentric and ring chromosomes were significantly increased with individual variation. The individual variations in the increment of dicentric and ring chromosomes after CT procedures were confirmed using PNA-FISH analysis of PBLs from 15 healthy volunteers after in vitro low-dose exposure using a 137Cs radiation device. These findings strongly suggest that appropriate medical use of low-dose radiation should consider individual differences in radiation sensitivity.

Quantification of the salivary volume flow rate in the parotid duct using the time‐spatial labeling inversion pulse (Time‐SLIP) technique at MRI: A feasibility study

We developed a method to quantify the volume flow rate (VFR) using the time‐spatial labeling inversion pulse (Time‐SLIP) technique to evaluate salivary function.

Hepatocellular carcinoma treated with sorafenib: Arterial tumor perfusion in dynamic contrast-enhanced CT as early imaging biomarkers for survival

OBJECTIVES To investigate whether hepatic perfusion CT yields early imaging biomarkers predictive of the prognosis of hepatocellular carcinoma (HCC) patients treated with sorafenib. METHODS We evaluated 36 HCC patients who underwent hepatic perfusion CT before- and one week after sorafenib therapy. We measured arterial and portal perfusion in the hepatic tumor and liver parenchyma [(AP)(PP)tumor], [(AP)(PP)liver]. The perfusion ratio was calculated by dividing the post- by the pre-sorafenib value. The effect of each value on the overall survival rate was analyzed with the Cox proportional hazards model; statistically significant parameters were subjected to receiver operating characteristic analysis based on median survival after sorafenib administration to determine the overall survival rate with the Kaplan-Meier method. RESULTS Pre-APtumor was significantly associated with the overall survival rate (hazard ratio (HR) and 95% confidence interval (CI), 0.16 and 0.02-0.84, p=0.03). The APtumor ratio tended to be associated with the overall survival rate (HR and 95% CI, 2.94 and 0.94-7.88, p=0.06). The overall survival rate was higher in patients with pre-APtumor>71.7mL/min/100mL, and with APtumor ratio≦1.1 (p<0.01 and 0.03, respectively, in Kaplan-Meier method with log-rank). CONCLUSION Hepatic perfusion CT yields early imaging biomarkers for predicting overall survival in HCC patients treated with sorafenib.