Daisuke Utsunomiya

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.

Initial experience with X-ray CT based attenuation correction in myocardial perfusion SPECT imaging using a combined SPECT/CT system

Objective: Attenuation artifacts adversely affect the diagnostic accuracy of myocardial perfusion imaging. We assessed the clinical usefulness of X-ray CT based attenuation correction (AC) in patients undergoing myocardial perfusion imaging by comparing their myocardial AC- and non-corrected (NC) SPECT images with the coronary angiography (CAG).Methods: We retrospectively reviewed the myocardial SPECT images of 30 patients (18 men, 12 women; mean age 68 years). Thirteen of 30 patients with coronary artery disease (CAD) and 17 without CAD were confirmed by CAG. They underwent sequential CT and myocardial SPECT imaging with thallium-201 (111 MBq) under an exercise or pharmacological stress protocol using our combined SPECT/ CT system. Two readers reviewed the myocardial SPECT images for the presence of CAD on a 4-point scale where 1 = normal, 2 = probably normal, 3 = probably abnormal, and 4 = abnormal. Two reading sessions were held. First, non-corrected (NC)-SPECT and second, AC-SPECT images using X-ray CT images were interpreted. Interobserver variability was assessed with kappa statistics. Diagnostic performance (accuracy) of coronary arterial stenosis was compared between AC- and NC-images.Results: Interobserver agreement for visual assessment was substantial or almost perfect. For AC-images, the observer consensus for analysis was 0.84 for the LAD-, 0.87 for the LCX-, and 0.71 for the RCA-territory. For NC-images, it was 0.91, 0.71, and 0.78. AC resulted in statistically significant improvements in overall diagnostic accuracy (sensitivity/ specificity/accuracy = 76%/93%/89%, 67%/86%/81%, respectively, for AC- and NC-images).Conclusions: Because of an increase in the specificity, diagnostic accuracy was significantly increased on AC-images. These preliminary data suggest that X-ray CT based AC in myocardial SPECT imaging has the potential to develop into a reliable clinical technique.

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.

Pericardial fat inflammation correlates with coronary artery disease

OBJECTIVES We sought to assess the association between inflammation in pericardial fat (PF) and coronary artery disease (CAD) by pathological examination and clinical evaluation with cardiac computed tomography (CT). BACKGROUND Inflammation of adipose tissue is involved in cardio-metabolic disorders and shows high density in CT. METHODS We quantified, by immunohistochemical means, the PF inflammation in 39 autopsy cases by counting leukocyte common antigen (LCA)-positive cells. We then measured the CT density of PF in 39 patients with acute coronary syndromes and 69 patients suspected of CAD. RESULTS Pericoronary PF had significantly more LCA-positive cells in CAD autopsy cases (n=21) than non-CAD cases (n=18) (44 ± 21 vs. 24 ± 22 cells/mm(2), p=0.006). The CT density of PF around culprit lesions was significantly higher than non-culprit lesions in patients with acute coronary syndromes (-72 ± 11 vs. -82 ± 14 HU, p=0.002), which may reflect PF inflammation. Among patients suspected of CAD, the pericardial CT density gradient (PDG; difference in CT density between pericoronary PF and PF apart from coronary arteries) was significantly greater in CAD patients (n=30) than non-CAD patients (n=39) (22 ± 16 vs. 16 ± 10 HU, p=0.046). Multiple logistic regression analysis demonstrated that the PF inflammation index (PFI; PDG × PF volume, which could be the integrated index of inflammatory activity and abundance of PF) was significantly associated with the presence of CAD (odds ratio [95% confidence interval]; 1.234 [1.012-1.503] per 1000 HU cm(3), p=0.037) independent of other metabolic risk factors such as hypertension, dyslipidemia, and diabetes. CONCLUSIONS Active inflammation in PF correlates with CAD. PF inflammation may be involved in pathogenesis of CAD.

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.

Evaluation of diffusion‐weighted imaging for the differential diagnosis of poorly contrast‐enhanced and T2‐prolonged bone masses: Initial experience

To determine whether quantitative diffusion‐weighted imaging (DWI) is useful for characterizing poorly contrast‐enhanced and T2‐prolonged bone masses.

A Low Tube Voltage Technique Reduces the Radiation Dose at Retrospective ECG-gated Cardiac Computed Tomography for Anatomical and Functional Analyses

RATIONALE AND OBJECTIVES To investigate the effect of low-tube-voltage technique on a cardiac computed tomography (CT) for coronary arterial and cardiac functional analyses and radiation dose in slim patients. MATERIALS AND METHODS We enrolled 80 patients (52women, 28 men; mean age, 68.7 ± 8.9 years) undergoing retrospective electrocardiogram-gated 64-slice cardiac CT. Forty were subjected to the low (80-kV) and 40 to the standard (120-kV) tube-voltage protocol. Quantitative parameters of the coronary arteries (ie, CT attenuation, image noise, and the contrast-to-noise ratio [CNR]) were calculated, as were the effective radiation dose and the figure of merit (FOM). Each coronary artery segment was visually evaluated using a 5-point scale. Cardiac function calculated by using low-tube-voltage cardiac CT was compared with that on echocardiographs. RESULTS CT attenuation and image noise were significantly higher at 80- than 120-kV (P < .01). CNR of the left and right coronary artery was 18.4 ± 3.8 and 18.5 ± 3.3, respectively, at 80 kV; these values were 19.7 ± 2.7 and 19.8 ± 2.8 at 120 kV; the difference was not significant. The estimated effective radiation dose was significantly lower at 80 than 120 kV (6.3 ± 0.6 vs. 13.9 ± 1.1 mSv, P < .01) and FOM was significantly higher at 80 than 120 kV (P < .01). At visual assessment, 99% of the coronary segments were diagnostic quality; the two protocols did not differ significantly. We observed a strong correlation and good agreement between low-tube-voltage cardiac CT and echocardiography for cardiac functional analyses. CONCLUSION Low-tube-voltage cardiac CT significantly reduced the radiation dose by approximately 55% in slim patients while maintaining anatomical image quality and accuracy of cardiac functional analysis.

Improvement of image quality at low-radiation dose and low-contrast material dose abdominal CT in patients with cirrhosis: intraindividual comparison of low tube voltage with iterative reconstruction algorithm and standard tube voltage.

Objective To intraindividually compare a low–tube voltage, low–contrast material dose computed tomography (CT) reconstructed with iterative reconstruction (IR) algorithm at standard tube voltage reconstructed with filtered back projection (FBP) and standard–contrast material dose during liver dynamic CT. Materials and Methods Twenty-five patients with liver cirrhosis underwent 64-section multidetector CT. One hundred twenty kilovolt (peak) (kV[p]) with standard contrast material dose of 600 mg of iodine per kilogram (protocol A) and 80 kV(p) with low–contrast material dose of 450 mg of iodine per kilogram (protocol B) CT image sets were reconstructed by using FBP algorithm and that of using IR algorithm with a 60%/40% blend of IR-FBP reconstruction at 80-kV(p) image set (protocol C). Scans obtained during 3 hepatic phases were subjected to quantitative and qualitative analysis. Results The mean radiation dose and the contrast medium dose were significantly lower under protocols B and C than under protocol A. In all hepatic phases, all signal-to-noise and contrast-to-noise ratios were greater under protocol C than under other protocols at all anatomic sites. Qualitative analysis showed that image noise and diagnostic acceptability were significantly higher under protocol C. Conclusion In all hepatic phases, a low–tube voltage, low–contrast material dose CT with IR algorithm yielded better contrast enhancement and image quality than a standard tube voltage, standard contrast material dose CT with FBP in thin adult patients.

Prediction of left main or 3-vessel disease using myocardial perfusion reserve on dynamic thallium-201 single-photon emission computed tomography with a semiconductor gamma camera

BACKGROUND Myocardial perfusion imaging (MPI) may fail to detect balanced ischemia. We evaluated myocardial perfusion reserve (MPR) using Tl dynamic single-photon emission computed tomography (SPECT) and a novel cadmium zinc telluride (CZT) camera for predicting 3-vessel or left main coronary artery disease (CAD). METHODS AND RESULTS: A total of 55 consecutive patients with suspected CAD underwent SPECT-MPI and coronary angiography. The MPR index was calculated using the standard 2-compartment kinetic model. We analyzed the utility of MPR index, other SPECT findings, and various clinical variables. On multivariate analysis, MPR index and history of previous myocardial infarction (MI) predicted left main and 3-vessel disease. The area under the receiver operating characteristic curve was 0.81 for MPR index, 0.699 for history of previous MI, and 0.86 for MPR index plus history of previous MI. MPR index ≤1.5 yielded the highest diagnostic accuracy. Sensitivity, specificity, and accuracy were 86%, 78%, and 80%, respectively, for MPR index, 64%, 76%, 73% for previous MI, and 57%, 93%, and 84% for MPR index plus history of previous MI. CONCLUSIONS Quantification of MPR using dynamic SPECT and a novel CZT camera may identify balanced ischemia in patients with left main or 3-vessel disease.