Dual-layer spectral detector computed tomography versus magnetic resonance cholangiopancreatography for biliary stones.

OBJECTIVE: Dual-layer spectral detector computed tomography (DLCT) can detect noncalcified biliary stones. The diagnostic ability of DLCT for detecting biliary stones may be comparable to that of magnetic resonance cholangiopancreatography (MRCP). This study seeks to compare the diagnostic ability for biliary stones between these two imaging modalities. METHODS: This retrospective study included 102 cases with a diagnosis of biliary stones including gallstones (n = 66) and common bile duct (CBD) stones (n = 25) or spontaneously passing CBD stones (n = 11). The reference standard used was operative findings, endoscopic retrograde cholangiopancreatography or follow-up over 6 months. In DLCT, 120-kVp images, 40-keV virtual monoenergetic images and material decomposition images were created. We compared the diagnostic ability of DLCT and MRCP for biliary stones using the McNemar's test. RESULTS: The sensitivity and specificity of DLCT versus MRCP for biliary stones were 91.2% versus 95.6% and 90.9% versus 90.9%. Thus, the sensitivity and specificity were not significantly different (P = 0.25 and P = 1.0). Although in small stones (<9 mm) the sensitivity of calcified stones was not different between DLCT and MRCP (100% versus 92.5%), the sensitivity of noncalcified stones in DLCT was lower than that in MRCP (38.5% versus 100%). CONCLUSION: The diagnostic ability of biliary stones in DLCT appears comparable to that of MRCP in overall cases. However, detecting noncalcified stones less than 9 mm in size is limited in DLCT.

Relationship between Homocysteine, Folate, Vitamin B12 and Physical Performance in the Institutionalized Elderly.

Hyperhomocysteinemia causes various diseases including cardiovascular disease, osteoporotic fracture and dementia. Although there have been reports that hyperhomocysteinemia decreases physical performance, findings are inconsistent on the association of homocysteine, folate, vitamin B12 and physical performance. Considering that lower physical performance increases the risk of fall and fracture in the elderly, the effect of nutritional status on physical function must be clarified. This is a cross-sectional study conducted from April 2015 to November 2016. Eighty-six residents and users in five care facilities were evaluated for their blood homocysteine, folate and vitamin B12 concentrations and indices for physical performance; lower limb muscle strength, handgrip strength and gait speed. Analyses of physical performance were done in women only, considering the high proportion of women in the study population and the muscular gender difference. In the third tertile of plasma homocysteine concentration, handgrip strength was significantly lower than in the first tertile (p=0.027). In the first tertile of serum folate concentration, handgrip strength was significantly lower than in the third tertile (p=0.002). Although not statistically significant, lower limb muscle strength in the third tertile of folate was higher than in the first (p=0.061) and second (p=0.057) tertile. In the multiple regression analysis, however, only serum folate concentration was a significant contributor except for age. In subjects with their serum folate and vitamin B12 concentrations both exceeding the median, lower limb muscle strength was higher. Low serum folate concentration is a risk factor for lower physical performance independent of homocysteine in elderly women.

Low contrast material dose coronary computed tomographic angiography using a dual-layer spectral detector system in patients at risk for contrast-induced nephropathy.

OBJECTIVE:: To evaluate the effects of virtual monochromatic imaging (VMI) using dual-layer spectral detector CT on the image quality of coronary CT angiography (CCTA) acquired by using a low contrast material (CM) dose. METHODS:: We used a VMI 50keV protocol with a 50% CM dose (140 mgI kg-1) to scan 30 patients with renal insufficiency and a 120 kVp with the standard CM dose (280 mgI kg-1) to scan 30 controls without renal insufficiency. Quantitative parameters, including CT attenuation, image noise, and contrast-to-noise ratio (CNR), were measured. The visual image quality factors of contrast enhancement, image noise, beam-hardening artefact, vessel sharpness, and overall image quality were scored on a 4-point scale. RESULTS:: The mean CT attenuation of the ascending aorta was significantly higher for 50 keV VMI than for 120 kVp. Image noise was significantly lower under the 50 keV VMI. CNR and the mean visual score for contrast enhancement were significantly higher for 50 keV VMI. There were no significant differences in the other visual image quality parameters between the two protocols. CONCLUSION:: Dual-layer spectral detector CT using 50 keV VMI enabled reducing the CM dose by 50 % without CCAT image quality degradation in patients with renal insufficiency. ADVANCES IN KNOWLEDGE:: The VMI 50 keV protocol using dual-layer spectral detector CT and a CM dose reduced by 50 % (140 mgI kg-1) can improve the diagnostic image quality of CCTA.

Reduced iodinated contrast media for abdominal imaging by dual-layer spectral detector computed tomography for patients with kidney disease.

Contrast-enhanced computed tomography using iodinated contrast media is useful for diagnosis of gastrointestinal diseases. However, contrast-induced nephropathy remains problematic for kidney diseases patients. Although current guidelines recommended the use of a minimal dose of contrast media necessary to obtain adequate images for diagnosis, obtaining adequate images with sufficient contrast enhancement is difficult with conventional computed tomography using reduced contrast media. Dual-layer spectral detector computed tomography enables the simultaneous acquisition of low- and high-energy data and the reconstruction of virtual monochromatic images ranging from 40 to 200 keV, retrospectively. Low-energy virtual monochromatic images can enhance the contrast of images, thereby facilitating reduced contrast media. In case 1, abdominal computed tomography angiography at 50 keV using 40% of the conventional dose of contrast media revealed the artery that was the source of diverticular bleeding in the ascending colon. In case 2, ischemia of the transverse colon was diagnosed by contrast-enhanced computed tomography and iodine-selective imaging using 40% of the conventional dose of contrast media. In case 3, advanced esophagogastric junctional cancer was staged and preoperative abdominal computed tomography angiography could be obtained with 30% of the conventional dose of contrast media. However, the texture of virtual monochromatic images may be a limitation at low energy.

Usefulness and limitations of dual-layer spectral detector computed tomography for diagnosing biliary stones not detected by conventional computed tomography: a report of three cases.

Computed tomography (CT) is useful for diagnosing biliary stones. However, the presence of stones not detected by conventional CT, such as iso-dense stones with CT numbers similar to those of bile or small stones, is problematic. Although conventional CT provides only 120-kVp images corresponding to CT numbers at approximately 70 keV, dual-layer spectral detector CT uses one X-ray source and dual-layer detectors to collect low- and high-energy data simultaneously; retrospective spectral analysis, including virtual monochromatic images with photon energy levels of 40-200 keV, material decomposition images, and spectral curves, can be immediately performed on demand. This technique can immediately discriminate between materials with similar conventional CT numbers. Therefore, prompt and accurate diagnosis of iso-dense stones can be performed. In two out of three of our cases, iso-dense stones were detected in virtual monochromatic images at 40 keV, but in the remaining case a common 4-mm bile duct stone was not detected on 120-kVp and 40-keV images by retrospective spectral analysis. However, this stone was detected by magnetic resonance cholangiopancreatography. Retrospective spectral analysis using dual-layer spectral detector CT was useful for prompt and accurate diagnosis of iso-dense stones, but detection of <5-mm stones may be a limitation of this technique and of conventional CT.

Comparison of lower leg muscle strength and grip strength for diagnosing slower gait speed in the elderly.

OBJECTIVES: Sarcopenia, decreased muscle volume and muscle weakness in the elderly is a serious risk of various adverse outcomes. Current diagnostic procedure for sarcopenia includes gait speed, grip strength, and percentage of skeletal muscle volume. However, lower leg muscle strength decreases much faster than grasp power, and we have evaluated the usefulness of its measurement using a recently developed instrument (Locomoscan). METHODS: Forty-three institutionalized elderly subjects were evaluated for their anthropometrical parameters, body composition, grasp and lower leg muscle strength, and gait speed. They were categorized into 2 groups; gait speed equal to or higher than 0.8 m/s and that below 0.8 m/s. RESULTS: Leg muscle strength per body weight was significantly greater in those with their gait speed equal to or higher than 0.8 m/s, whereas there was no significant difference in other parameters. Receiver operator characteristics analysis has shown that leg muscle alone significantly predicted the greater gait speed. CONCLUSIONS: Lower leg muscle strength can be useful for predicting gait speed.

The Influence of Iterative Reconstruction on Coronary Artery Calcium Scoring-Phantom and Clinical Studies.

RATIONALE AND OBJECTIVES: We compared the effect of iterative model reconstruction (IMR), filtered back projection (FBP), and hybrid iterative reconstruction (HIR) on coronary artery calcium (CAC) scoring. MATERIALS AND METHODS: CAC scans of 30 consecutive patients (18 men and 12 women, age 70.1 ± 12.2 years) were reconstructed with FBP, HIR, and IMR, and the image noise was measured on all images. Two radiologists independently measured the CAC scores using semiautomated software, and interobserver agreement was evaluated. Statistical analysis included the Spearman correlation coefficient and Bland-Altman analysis. RESULTS: The mean image noise on FBP, HIR, and IMR images was 48.0 ± 7.9, 29.6 ± 4.8, and 9.3 ± 1.3 Hounsfield units, respectively. The difference among all reconstruction combinations was significant (P < .01). The CAC score on HIR and IMR scans was 4.2% and 8.9% lower, respectively, than the CAC score on FBP images. There was no significant difference in the mean CAC score among the three reconstructions. The interobserver correlation was excellent for all three reconstructions (r2 = 0.96 FBP, 0.99 HIR, 0.99 IMR); the best Bland-Altman measure of agreement was with IMR, followed by HIR and FBP. CONCLUSION: For CAC scoring, IMR can reduce the image noise and blooming artifacts, and consequently lowers the measured CAC score. IMR can lessen measurement variability and yield stable, reproducible measurements.

Effect of iterative reconstruction on variability and reproducibility of epicardial fat volume quantification by cardiac CT.

BACKGROUND: The epicardial fat volume (EFV) measured by cardiac CT has emerged as an important parameter for understanding the pathophysiology of coronary atherosclerosis. OBJECTIVE: We investigated the variability and reproducibility of EFV measurements and evaluated the effect of model-based type iterative reconstruction (M-IR) on measurement results. METHODS: Non-contrast cardiac CT data (tube voltage 120-kVp, tube current time product 32 mAs) of 30 consecutive patients were reconstructed with filtered back projection (FBP), hybrid type iterative reconstruction (H-IR), and M-IR using a slice thickness of 3.0 mm. CT attenuation and image noise was measured for all reconstructions. Two observers independently quantified EFV using semi-automated software and interobserver agreement was evaluated. RESULTS: There was no significant difference in the CT attenuation of the ascending aorta among the three reconstructions. The mean image noise on FBP-, H-IR-, and M-IR images was 48.0 ± 7.9 HU, 29.6 ± 4.8 HU, and 9.3 ± 1.3 HU, respectively; there was a significant difference among all comparison combinations for the three reconstructions (p < 0.01). FBP yielded the highest EFV among the three reconstructions (171.0 ± 54.9 cm(3) [FBP], 153.8 ± 53.1 cm(3) [H-IR], and 134.0 ± 46.4 cm(3) [M-IR]). For all three reconstructions, interobserver correlations were excellent (r = 0.91 [FBP], 0.93 [H-IR], and 0.96 [M-IR]). Interobserver comparisons showed that the lowest Bland-Altman limit of agreement was with M-IR (mean difference 2.0 ± 4.9%, 95% limit of agreement, -24.0 to 28.0%) followed by H-IR (-2.6 ± 7.1%, -39.8 to 34.6%) and FBP (-0.2 ± 8.6%, -45.3- to 45.0%). CONCLUSION: For the quantification of epicardial fat by cardiac CT, model-based iterative reconstruction can improve the image quality and lessen measurement variability.

Extracapsular extension of prostate cancer: diagnostic value of combined multiparametric magnetic resonance imaging and isovoxel 3-dimensional T2-weighted imaging at 1.5 T.

OBJECTIVE: The objective of this study was to assess whether adding isovoxel 3-dimensional T2-weighted imaging (volume isotropic T2-weighted acquisition [VISTA]) to multiparametric magnetic resonance imaging (mp-MRI) improves the ability to diagnose the extracapsular extension (ECE) of prostate cancer. METHODS: Two radiologists independently evaluated ECE on images acquired with mp-MRI only (method A) and mp-MRI plus VISTA (method B) in 50 men who had undergone prostatectomy. We also compared the signal-to-noise ratio of the tumor on T2WI and VISTA scans. RESULTS: Sensitivity, specificity, and accuracy were higher with method B. For both readers, specificity, accuracy, and the area under the receiver operating characteristic curve of method B were significantly higher than those of method A (reader 1: P = 0.028, 0.025, and 0.006; reader 2: P = 0.017, 0.0071, and 0.018). The signal-to-noise ratio was significantly higher on T2-weighted imaging than VISTA images (9.21 [SD, 2.46] vs 7.30 [SD, 1.87], P < 0.01). CONCLUSIONS: The addition of VISTA to mp-MRI improves the diagnostic value for ECE significantly.

Improved image quality at 256-slice coronary CT angiography in patients with a high heart rate and coronary artery disease: comparison with 64-slice CT imaging.

BACKGROUND: The 256-slice computed tomography (CT) scanners with wider detector coverage and faster gantry rotation speed are now available. The performance of scanners that feature a rotation speed of 270 ms at coronary CT angiography (CCTA) has not been evaluated in patients with a higher heart rate. PURPOSE: To evaluate the image quality of 256-slice CT with faster gantry rotation speed in patients undergoing CCTA. MATERIAL AND METHODS: We enrolled 886 patients; 357(40.3%) underwent study on a 64-slice CT at a rotation speed of 420 ms, the other 529 (59.7%) were examined using a 256-slice CT scanner at 270 ms. Two observers judged the image quality of 2658 imaged coronary arteries on a 4-point scale. RESULTS: The mean image quality score was significantly higher for the 256 - than the 64-slice CT scans (3.94 ± 0.28 vs. 3.73 ± 0.61; P < 0.01). There was no significant difference in the image quality scores between 64 - and 256-slice scans in patients whose heart rate (HR) was <60 bpm. However, in patients whose HR exceeded 60 bpm these scores were significantly higher for 256-slice CT images (P < 0.01). CONCLUSION: CCTA performed on the 256-slice CT scanner yielded significantly better image quality in patients with an HR exceeding 60 bpm.

Clinical impact of 3-dimensional balanced turbo-field-echo magnetic resonance cholangiopancreatography at 3 T: prospective intraindividual comparison with 3-dimensional turbo-spin-echo magnetic resonance cholangiopancreatography.

OBJECTIVE: The objective of this study was to evaluate the clinical utility of 3-dimensional (3D) balanced turbo-field-echo (BTFE) magnetic resonance cholangiopancreatography (MRCP) with gate and track acquisition at 3 T. METHODS: Using a 3-T unit, we subjected 52 consecutive patients to 3D BTFE MRCP with the navigator-gated technique and 3D turbo-spin-echo volume isotropic T2-weighted acquisition (VISTA) MRCP with the navigator-triggered technique. Two radiologists independently rated the image quality and visibility of the right and left hepatic duct, cystic duct, common bile duct, gallbladder, and main pancreatic duct using a 4-point scale. The signal-to-noise ratio, contrast-to-noise ratio, and the acquisition time were evaluated by quantitative analysis. RESULTS: The visual scores of the cystic duct, common bile duct, gallbladder, and overall image quality were significantly higher for BTFE than VISTA MRCP (P < 0.01). The score for the main pancreatic duct was significantly higher with VISTA MRCP (P < 0.01). The image acquisition time was significantly shorter with BTFE than VISTA MRCP (139.8 ± 45.4 vs 416.9 ± 108.3 seconds, P < 0.01). There was no significant difference in signal-to-noise ratio and contrast-to-noise ratio. CONCLUSIONS: Three-dimensional BTFE MRCP yields significantly better image quality and visibility of large biliary structures than VISTA MRCP at a significantly shorter acquisition time. Volume isotropic T2-weighted acquisition MRCP provides detailed information on the main pancreatic duct that tends to be obscure on the 3D BTFE sequence.

Onset of buccal pumping in catshark embryos: how breathing develops in the egg capsule.

Respiration in fishes involves buccal pumping, which is characterized by the generation of nearly continuous water flow over the gills because of the rhythmic expansion/compression of the pharyngeal cavity. This mechanism is achieved by the functions of the vascular, skeletal, and muscular systems. However, the process by which the embryo establishes the mechanism remains a mystery. Morphological and kinematical observations on captive cloudy catsharks, Scyliorhinus torazame, have suggested that the embryo starts buccal pumping just before the respiratory slits open on the egg capsule. During the pre-opening period, the embryo acquires oxygen mainly via the external gill filaments. After slit opening, respiration of the embryo involves buccal pumping to pass water over the "internal gills." The onset of buccal pumping accompanies four morphological changes: (1) regression of the external gill filaments, (2) development of blood vessels within the "internal gills," (3) completion of the development of hyoid skeletal and muscular elements, and (4) development of the oral valve. A previous study showed that buccal pumping allows the embryo to actively regulate oxygen intake by changing the pumping frequency. Thus, establishment of buccal pumping in the egg capsule is probably important for embryo survival in the unstable oxygen environment of the egg capsule after slit opening.

Improved coronary in-stent visualization using a combined high-resolution kernel and a hybrid iterative reconstruction technique at 256-slice cardiac CT-Pilot study.

OBJECTIVES: To investigate the diagnostic performance of 256-slice cardiac CT for the evaluation of the in-stent lumen by using a hybrid iterative reconstruction (HIR) algorithm combined with a high-resolution kernel. METHODS: This study included 28 patients with 28 stents who underwent cardiac CT. Three different reconstruction images were obtained with: (1) a standard filtered back projection (FBP) algorithm with a standard cardiac kernel (CB), (2) an FBP algorithm with a high-resolution cardiac kernel (CD), and (3) an HIR algorithm with the CD kernel. We measured image noise and kurtosis and used receiver operating characteristics analysis to evaluate observer performance in the detection of in-stent stenosis. RESULTS: Image noise with FBP plus the CD kernel (80.2 ± 15.5 HU) was significantly higher than with FBP plus the CB kernel (28.8 ± 4.6 HU) and HIR plus the CD kernel (36.1 ± 6.4 HU). There was no significant difference in the image noise between FBP plus the CB kernel and HIR plus the CD kernel. Kurtosis was significantly better with the CD- than the CB kernel. The kurtosis values obtained with the CD kernel were not significantly different between the FBP- and HIR reconstruction algorithms. The areas under the receiver operating characteristics curves with HIR plus the CD kernel were significantly higher than with FBP plus the CB- or the CD kernel. The difference between FBP plus the CB- or the CD kernel was not significant. The average sensitivity, specificity, and positive and negative predictive value for the detection of in-stent stenosis were 83.3, 50.0, 33.3, and 91.6% for FBP plus the CB kernel, 100, 29.6, 40.0, and 100% for FBP plus the CD kernel, and 100, 54.5, 40.0, and 100% for HIR plus the CD kernel. CONCLUSIONS: The HIR algorithm combined with the high-resolution kernel significantly improved diagnostic performance in the detection of in-stent stenosis.

Indirect computed tomography venography with a low-tube-voltage technique: reduction in the radiation and contrast material dose--a prospective randomized study.

OBJECTIVE: The objective of the study was to investigate the effects of low-tube-voltage computed tomography (CT) venography on qualitative and quantitative image parameters and the radiation dose. METHODS: Eighty-eight studies on 84 patients underwent pelvic and lower-extremity CT venography under protocol A (standard 120 kV with 150 mL of contrast material, n = 44) or protocol B (80 kV with 100 mL of contrast material, n = 44) on a 64-detector CT scanner. We compared the dose length product in the 2 protocols. Two blinded observers measured CT attenuation in the veins, the image noise, contrast-to-noise ratio, and figure of merit. RESULTS: The mean dose length product was significantly lower under protocol B than A (603.2 [SD, 67.2] vs 1131.7 [SD, 67.0] mGy × cm) (P < 0.01). Mean CT attenuation of the veins was significantly greater with protocol B (125.3 [SD, 16.2] vs 106.1 [SD, 16.0] Hounsfield units) (P < 0.01), and the mean image noise was also significantly higher under protocol B (6.6 [SD, 0.8] vs 4.9 [SD, 0.7] Hounsfield units) (P < 0.01). There was no difference in contrast-to-noise ratio (P = 0.46). Figure of merit was significantly higher under protocol B (P < 0.01). CONCLUSIONS: Computed tomography venography with a low-tube-voltage technique allows reducing the radiation dose and the amount of contrast material without image quality degradation.