Seitaro Oda

Combination of a low-tube-voltage technique with hybrid iterative reconstruction (iDose) algorithm at coronary computed tomographic angiography.

We compare the performance of low tube voltage with the hybrid iterative reconstruction (iDose) with standard and low tube voltage with the filtered backprojection (FBP) using phantoms at computed tomographic coronary angiography. In computed tomographic coronary angiography, application of the combined low tube voltage with iDose resulted in significant image quality improvements compared to the low tube voltage with FBP. Image quality was the same or better despite a reduction in the radiation dose by 76% compared with standard tube voltage with FBP.

Ground-Glass Opacities on Thin-Section Helical CT: Differentiation Between Bronchioloalveolar Carcinoma and Atypical Adenomatous Hyperplasia

OBJECTIVE The purpose of our study was to investigate the differentiation between bronchioloalveolar carcinoma and atypical adenomatous hyperplasia manifesting pure ground-glass opacity (GGO) based on selected features on thin-section helical CT scans. MATERIALS AND METHODS We evaluated 35 bronchioloalveolar carcinomas and 17 atypical adenomatous hyperplasias that were histologically confirmed and that manifested pure GGO on thin-section helical CT scans. We recorded the age, sex, and smoking history (Brinkman index) of the patients. Two board-certified radiologists measured the maximum diameter and mean attenuation value of the nodules; the measured values were averaged for each nodule. Using a 3-point scale, they visually assessed the images for consensus with respect to nodular sphericity, marginal irregularity, vascular convergence, pleural retraction, and findings of an internal air bronchogram. CT findings of atypical adenomatous hyperplasia and bronchioloalveolar carcinoma were compared using univariate and multivariate logistic regression analysis; the odds ratio was computed using the atypical adenomatous hyperplasia group as the reference group. RESULTS By univariate analysis, the patient age, nodular maximum diameter, mean attenuation value, and findings of an internal air bronchogram were statistically significantly associated with bronchioloalveolar carcinoma (odds ratio [OR] = 1.10 [p = 0.012], OR = 1.27 [p < 0.01], OR = 1.01 [p = 0.023], and OR = 25.30 [p < 0.001], respectively), and sphericity was significantly associated with atypical adenomatous hyperplasia (OR = 0.059, p < 0.001). By multivariate analysis, sphericity was significantly associated with atypical adenomatous hyperplasia (OR = 0.125, p = 0.042) and findings of an internal air bronchogram were associated with bronchioloalveolar carcinoma (OR = 16.10, p = 0.007). CONCLUSION Nodular sphericity and an internal air bronchogram were useful at thin-section helical CT performed to differentiate between bronchioloalveolar carcinoma and atypical adenomatous hyperplasia. Interobserver agreement was high for each finding.

Computer-Aided Volumetry of Pulmonary Nodules Exhibiting Ground-Glass Opacity at MDCT

OBJECTIVE The purpose of this study was to investigate the accuracy and reproducibility of results acquired with computer-aided volumetry software during MDCT of pulmonary nodules exhibiting ground-glass opacity. MATERIALS AND METHODS To evaluate the accuracy of computer-aided volumetry software, we performed thin-section helical CT of a chest phantom that included simulated 3-, 5-, 8-, 10-, and 12-mm-diameter ground-glass opacity nodules with attenuation of -800, -630, and -450 HU. Three radiologists measured the volume of the nodules and calculated the relative volume measurement error, which was defined as follows: (measured nodule volume minus assumed nodule volume / assumed nodule volume) x 100. Two radiologists performed two independent measurements of 59 nodules in humans. Intraobserver and interobserver agreement was evaluated with Bland-Altman methods. RESULTS The relative volume measurement error for simulated ground-glass opacity nodules measuring 3 mm ranged from 51.1% to 85.2% and for nodules measuring 5 mm or more in diameter ranged from -4.1% to 7.1%. In the clinical study, for intraobserver agreement, the 95% limits of agreement were -14.9% and -13.7% and -16.6% to 15.7% for observers A and B. For interobserver agreement, these values were -16.3% to 23.7% for nodules 8 mm in diameter or larger. CONCLUSION With computer-aided volumetry of ground-glass opacity nodules, the relative volume measurement error was small for nodules 5 mm in diameter or larger. Intraobserver and interobserver agreement was relatively high for nodules 8 mm in diameter or larger.

Contrast Injection Protocols for Coronary Computed Tomography Angiography Using a 64-Detector Scanner : Comparison Between Patient Weight-Adjusted-and Fixed Iodine-Dose Protocols

Objective:To compare patient-weight-adjusted and fixed iodine-dose protocols at coronary computed tomography angiography (CTA) using a 64-detector scanner and computer-assisted bolus tracking. Materials and Methods:Approval from our institutional review board and patient prior informed consent were obtained before entering 60 patients with suspected coronary disease in this study. The patients were randomly assigned to one of 2 protocols. In the fixed iodine-dose protocol, they received a fixed dose of 80 mL Iopamidol-370; the injection duration was 20 seconds. In the weight-adjusted iodine-dose protocol, the dose was tailored to the patient body weight; this group received 1.0 mL/kg and the injection duration was shorter, ie, 15 seconds. Imaging was on a 64-detector CT scanner using a computer-assisted bolus tracking technique. A radiologist blinded to the protocol used measured the Hounsfield density number of the large vessels and coronary arteries. CT attenuation in the aortic root was compared in patients whose weight was less than 58 kg (group 1) or 58 kg or more (group 2). The standard deviation (SD) of CT attenuation in the aortic root and the myocardium was compared with evaluate image noise. Using a 3-point scale, 2 radiologists independently evaluated beam-hardening artifacts and coronary enhancement. Statistical analysis was with the two-tailed Student t test and the Mann-Whitney U test. Results:There was no significant difference between the protocols with respect to CT attenuation of the ascending aorta and coronary arteries. Under the fixed-iodine-dose protocol, mean CT attenuation in the aortic root was 421.3 ± 51.5 Hounsfield unit (HU) in the lighter-, and 397.2 ± 42.3 HU in the heavier weight group, respectively; the difference was statistically significant (P = 0.03). Under the weight-adjusted iodine-dose protocol, these values were 407.6 ± 85.1 and 409.2 ± 47.9 HU, respectively and the difference was not statistically significant (P = 0.17). The SD of the ascending aorta and myocardium was significantly higher for the fixed- than the weight-adjusted iodine-dose protocol. The mean visual score for beam-hardening artifacts was significantly lower in the weight-adjusted- than the fixed-iodine-dose protocol (P < 0.01), however, there was no significant difference in the enhancement of the coronary arteries (P = 0.82). Conclusion:At 64-detector CTA of the heart, the patient weight-tailored dose protocol with the 15-second injection duration yielded significantly better image quality than the fixed-dose, 20-second injection duration protocol.

A hybrid iterative reconstruction algorithm that improves the image quality of low-tube-voltage coronary CT angiography.

OBJECTIVE We investigated whether a hybrid iterative reconstruction (HIR) algorithm improves image quality at low-tube-voltage coronary CT angiography (CTA) compared with filtered back projection (FBP). SUBJECTS AND METHODS Eighteen patients (seven men, 11 women; mean age, 67.8 years) underwent retrospectively gated coronary CTA at 80 kV with a volume CT dose index (CTDI(vol)) of 18.8 mGy on a 64-MDCT scanner. CT images were reconstructed using only FBP and only HIR. For each patient, CT images subjected to the two different reconstructions were reviewed by two observers. Quantitative image quality parameters-that is, CT attenuation (HU) of the coronary arteries, image noise, and contrast-to-noise ratio (CNR)-were calculated and compared for the two reconstruction methods and the overall image quality for each reconstruction was visually scored on a 5-point scale. RESULTS The mean estimated effective radiation dose for 80-kV coronary CTA was 4.7 ± 0.4 (SD) mSv. The two reconstruction methods did not significantly differ with respect to the CT attenuation of the coronary arteries. The image noise was significantly lower with HIR than with FBP (20.3 ± 5.3 vs 49.4 ± 12.0 HU, respectively; p < 0.01), and the CNR was significantly higher with HIR than with FBP (29.8 ± 7.4 vs 12.7 ± 2.9, p < 0.01). The visual scores for image quality were higher with HIR than with FBP (p < 0.01). CONCLUSION The HIR algorithm can reduce image noise and improve image quality at low-tube-voltage coronary CTA.

Low-kilovoltage, high-tube-current MDCT of liver in thin adults: pilot study evaluating radiation dose, image quality, and display settings.

OBJECTIVE The purpose of our study was to evaluate the effect of a low tube voltage-high tube current-time product technique for portal phase abdominal CT of thin adults. SUBJECTS AND METHODS This study included 25 patients who had undergone portal phase abdominal CT at 120 kVp in the preceding 6 months. All were scanned using 80 kVp and high tube-current time products. We assessed the estimated effective dose (ED), image noise, attenuation, contrast-to-noise ratio (CNR), and figure of merit of the liver and portal vein. Two radiologists evaluated the quality of scans for image contrast and streak artifacts at 80 kVp, 120 kVp, and 80 kVp with wide window width display presets (W-80). RESULTS The estimated ED was 33% lower at 80 than at 120 kVp. CNR of the portal vein was 36.8% higher at 80 than 120 kVp, and for the liver it was 17.7% higher at 80 than 120 kVp. The visual score of image contrast was significantly higher for W-80 than for 120 kVp; however, there was no significant difference in the visual score of streak artifacts. CONCLUSION At portal phase abdominal CT, 80 kVp and a high tube current-time product setting significantly improved image quality and reduced the radiation dose compared with 120 kVp.

Effect of Contrast Injection Protocols with Dose Adjusted to the Estimated Lean Patient Body Weight on Aortic Enhancement at CT Angiography

OBJECTIVE The objective of our study was to investigate the effect on aortic enhancement of iodine doses adjusted for the patient estimated lean body weight (LBW) at CT angiography (CTA). SUBJECTS AND METHODS CTA for the whole aorta using a 64-MDCT scanner was performed in 97 patients (mean age, 67.4 years) with confirmed or suspected aortoiliac disease. The patients were divided into two groups: a total body weight (TBW) group (n = 49) and an estimated LBW group (n = 48). LBW was estimated from the patient weight (TBW) and height. The TBW and estimated LBW groups received 360 mg I/kg of TBW and 450 mg I/kg of estimated LBW of contrast medium, respectively. The relative dose ratio for the estimated LBW group versus the TBW group was based on the fact that the standard percentage of body fat in Japanese adults with an average TBW of 60 kg is 20% (360 = 0.8 x 450). Differences in the degree of aortic enhancement and interpatient variability in aortic enhancement between the estimated LBW and TBW group were evaluated. RESULTS Mean aortic enhancement was 308.9 HU for the estimated LBW group and 314.1 HU for the TBW group, indicating no significant difference in the degree of enhancement (Welchs t test, p = 0.61). The interquartile range was smaller for the LBW group than the TBW group (52.8 vs 79.1 HU, respectively); interpatient variability was lower in the estimated LBW group. The aortic attenuation gradient in the TBW group and estimated LBW group was 20.7 and 25.8 HU, respectively; the difference was not statistically significant. CONCLUSION The CTA protocol using an estimated LBW-tailored dose yielded more consistent aortic enhancement with reduced interpatient variability than the CTA protocol using a TBW-based dose.

Quantitative Blood Flow Measurements in Gliomas Using Arterial Spin-Labeling at 3T: Intermodality Agreement and Inter- and Intraobserver Reproducibility Study

BACKGROUND AND PURPOSE: QUASAR is a particular application of the ASL method and facilitates the user-independent quantification of brain perfusion. The purpose of this study was to assess the intermodality agreement of TBF measurements obtained with ASL and DSC MR imaging and the inter- and intraobserver reproducibility of glioma TBF measurements acquired by ASL at 3T. MATERIALS AND METHODS: Two observers independently measured TBF in 24 patients with histologically proved glioma. ASL MR imaging with QUASAR and DSC MR imaging were performed on 3T scanners. The observers placed 5 regions of interest in the solid tumor on rCBF maps derived from ASL and DSC MR images and 1 region of interest in the contralateral brain and recorded the measured values. Maximum and average sTBF values were calculated. Intermodality and intra- and interobsever agreement were determined by using 95% Bland-Altman limits of agreement and ICCs. RESULTS: The intermodality agreement for maximum sTBF was good to excellent on DSC and ASL images; ICCs ranged from 0.718 to 0.884. The 95% limits of agreement ranged from 59.2% to 65.4% of the mean. ICCs for intra- and interobserver agreement for maximum sTBF ranged from 0.843 to 0.850 and from 0.626 to 0.665, respectively. The reproducibility of maximum sTBF measurements obtained by methods was similar. CONCLUSIONS: In the evaluation of sTBF in gliomas, ASL with QUASAR at 3T yielded measurements and reproducibility similar to those of DSC perfusion MR imaging.

Volume-Doubling Time of Pulmonary Nodules with Ground Glass Opacity at Multidetector CT: Assessment with Computer-Aided Three-Dimensional Volumetry

RATIONALE AND OBJECTIVES To investigate the volume-doubling time (VDT) of histologically proved pulmonary nodules showing ground glass opacity (GGO) at multidetector CT (MDCT) using computer-aided three-dimensional volumetry. MATERIALS AND METHODS We retrospectively evaluated 47 GGO nodules (mixed n = 28, pure n = 19) that had been examined by thin-section helical CT more than once. They were histologically confirmed as atypical adenomatous hyperplasia (AAH, n = 13), bronchioloalveolar carcinoma (BAC, n = 22), and adenocarcinoma (AC, n = 12). Using computer-aided three-dimensional volumetry software, two radiologists independently performed volumetry of GGO nodules and calculated the VDT using data acquired from the initial and final CT study. We compared VDT among the three pathologies and also compared the VDT of mixed and pure GGO nodules. RESULTS The mean VDT of all GGO nodules was 486.4 ± 368.6 days (range 89.0-1583.0 days). The mean VDT for AAH, BAC, and AC was 859.2 ± 428.9, 421.2 ± 228.4, and 202.1 ± 84.3 days, respectively; there were statistically significant differences for all comparative combinations of AAH, BAC, and AC (Steel-Dwass test, P < .01). The mean VDT for pure and mixed GGO nodules was 628.5 ± 404.2 and 276.9 ± 155.9 days, respectively; it was significantly shorter for mixed than pure GGO nodules (Mann-Whitney U-test, P < .01). CONCLUSION The evaluation of VDT using computer-aided volumetry may be helpful in assessing the histological entities of GGO nodules.

Detection of nodules showing ground-glass opacity in the lungs at low-dose multidetector computed tomography: phantom and clinical study.

To investigate the effect of the radiation dose (tube current second product) and the attenuation value of nodules with ground-glass opacity (GGO) on their detectability at multidetector computed tomography (MDCT). Methods: We scanned a chest CT phantom that included simulated GGO nodules with an MDCT scanner. The attenuation value of the simulated lung parenchyma was −900 Hounsfield units (HU); it was −800 and −650 HU for the simulated GGO nodules. We used a tube current second product of 180 mA as the standard and 21, 45, 60, and 90 mAs as the low-dose and performed receiver operating characteristic analysis to compare the performance of 5 radiologists in detecting GGO nodules at each milliampere. To assess the detectability of GGO nodules on human lung images, the observers were presented with 38 GGO nodules from 15 patients. The 5 radiologists independently reviewed chest CT images at 21 and 45 mAs. Results: In the phantom study, the Az value for GGO nodules with a CT number of −800 HU was significantly lower at 21 than 180 effective mA (0.86 vs. 0.96; P < 0.01). There was no statistically significant difference in the Az value of GGO nodules with a CT number of −650 HU, irrespective of milliamperes used (P = 0.165). In the clinical study, 39.5% and 25.8% of GGO were missed at 21 and 45 mAs, respectively. Conclusions: At MDCT, GGO nodules with a CT number of −650 HU or less were difficult to detect at the lower milliampere settings (21 and 45 mAs).