Canon Medical Systems Research Articles

Diagnostic accuracy of 2D-SWE ultrasound for liver fibrosis assessment in MASLD: A multi-level random effects model meta-analysis.

Metabolic dysfunction-associated steatotic liver disease (MASLD) imposes significant healthcare burdens. Early detection of advanced fibrosis and cirrhosis in MASLD is essential due to their unfavourable outcomes. This multi-level random-effects meta-analysis aimed to provide the best evidence for the diagnostic accuracy of two-dimensional shear wave elastography (2D-SWE) in detecting liver fibrosis in biopsy-proven MASLD. Systematic search in PubMed/MEDLINE, Embase, Scopus, Web of Science, LILACS, and Cochrane Library electronic databases for full-text articles published in any language up to the 26th of February 2024. Included studies reported liver stiffness measurement (LSM) by 2D-SWE and used histological diagnosis as gold standard. A linear mixed-effects multiple thresholds model was employed, and summary estimates for sensitivity (Se), specificity (Sp), and summary area under the curve (sAUC) were computed. 20 observational studies (SuperSonic Imagine, General Electric Healthcare, Canon Medical Systems) fulfilled the inclusion criteria, comprising 2223 participants with biopsy-proven MASLD. The prevalence of mild fibrosis (F1), significant fibrosis (F2), advanced fibrosis (F3), and cirrhosis (F4) was 30.0%, 18.5%, 17.9%, and 10.9%, respectively. The sAUCs [95%CI] in detecting ≥F1, ≥F2, ≥F3, and F4 for all ultrasound machines considered together were 0.82 [0.16-0.98], 0.82 [0.76-0.88], 0.86 [0.77-0.93], and 0.89 [0.80-0.95], respectively. The optimal cut-off values were 6.432kPa for ≥F1, 8.174kPa for ≥F2, 9.418kPa for ≥F3, and 11.548kPa for F4, respectively. Our meta-analysis identified optimised cut-offs for fibrosis staging by 2D-SWE in etiology-specific chronic liver diseases (MASLD), with excellent diagnostic performance, underscoring the potential for standardising cut-off values.

Dual Energy Metal Artifact Reduction for Iodine-125 Seed Identification in Postimplant CT after Prostate Brachytherapy.

To assess the metal artifact reductions of dual-energy computed tomography (DECT) high-energy virtual monochromatic images (VMI) combined with the single energy metal artifact reduction (SEMER) (CANON MEDICAL SYSTEMS, Otawara, Japan) processing techniques for iodine (I)-125 seed identification in postimplant computed tomography (CT) after prostate brachytherapy. Dual-energy acquisition with fast tube voltage switching was performed on a prostate phantom with simulated seeds and six clinical cases treated with I-125 prostate brachytherapy. The images were retrospectively reconstructed at VMI energy levels of 65-200 keV and with and without SEMAR (SEMAR and non-SEMAR images). To estimate seed swelling, the caliber of iodine-125 seed was calculated as the full width at half maximum. The metal artifacts were evaluated using the artifact index (AI). The dose distributions were calculated and were compared among the high-energy VMI (SEMAR and non-SEMAR images) and low-energy VMI (SEMAR images). The blooming artifacts decreased at higher energy levels. In addition, the SEMAR process markedly reduced AI, which helped reduce overestimation of high dose ranges in the treatment planning dose map. The locations and number of iodine-125 seed were clearly identified in the dose distribution map of the treatment planning using 200keV VMI with SEMAR. The high-energy VMI of the dual energy CT in combination with SEMAR is appropriate for the postimplant planning process of I-125 prostate brachytherapy.

Intersystem and Interoperator Agreement of US Attenuation Coefficient for Quantifying Liver Steatosis.

Background The extent of liver steatosis can be assessed using US attenuation coefficient (AC) algorithms currently implemented in several US systems. However, little is known about intersystem and interoperator variability in measurements. Purpose To assess intersystem and interoperator agreement in US AC measurements for fat quantification in individuals with varying degrees of liver steatosis and to assess the correlation of each manufacturer's AC algorithm results with MRI proton density fat fraction (PDFF). Materials and Methods This prospective study was conducted at Southwoods Imaging, Youngstown, Ohio, September 30-October 1, 2023. Two operators independently obtained AC measurements using eight US systems equipped with an AC algorithm from different manufacturers. On the same day, MRI PDFF measurement was performed by a different operator. Correlation between US AC and MRI PDFF was assessed using a mixed-effects model. Agreement between systems and operators was evaluated using the intraclass correlation coefficient (ICC). Results Twenty-six individuals (mean age, 55.4 years ± 10.7 [SD]; 16 female participants) were evaluated. The correlation of US AC with MRI PDFF was high for five AC algorithms (r range, 0.70-0.86), moderate for two (r = 0.62 for both), and poor for one (r = 0.47). In pairwise comparisons, none of the pairs of systems achieved excellent agreement (overall ICC = 0.33 [95% CI: 0.15, 0.52]). One pair showed good agreement (ICC = 0.79 [95% CI: 0.66, 0.87]), eight pairs showed moderate agreement (ICC range, 0.50 [95% CI: 0.22, 0.69] to 0.73 [95% CI: 0.49, 0.85]), and 19 pairs showed poor agreement (ICC range, 0.11 [95% CI: -0.06, 0.37] to 0.48 [95% CI: 0.20, 0.67]). Interoperator agreement on AC value was excellent for the Samsung Medison algorithm (ICC = 0.90 [95% CI: 0.80, 0.96]), good for the Siemens Healthineers (ICC = 0.76 [95% CI: 0.54, 0.89]) and Canon Medical Systems (ICC = 0.76 [95% CI: 0.16, 0.92]) algorithms, and moderate for the remaining algorithms (ICC range, 0.50 [95% CI: 0.16, 0.73] to 0.74 [95% CI: 0.51, 0.88]). The mean AC value obtained by the two operators did not differ for any system except the system from Canon Medical Systems. Conclusion There was substantial variability in AC values obtained with different US systems, precluding interchangeability between systems for liver steatosis diagnosis and follow-up imaging. Interoperator agreement ranged from moderate to excellent. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Han in this issue.

Diagnostic Performance and Clinical Impact of Photon-Counting Detector Computed Tomography in Coronary Artery Disease.

Photon-counting detector-computed tomography (PCD-CT) has emerged as a promising technology, offering improved spatial resolution. This study aimed to evaluate the clinical impact and diagnostic performance of PCD-CT vs conventional energy-integrating detector computed tomography (EID-CT) for obstructive coronary artery disease (CAD). From 2022 to 2023, we retrospectively identified 7,833 consecutive patients who underwent clinically indicated coronary computed tomography angiography (CCTA) at a single center, with either PCD-CT (n=3,876; NAEOTOM Alpha [Siemens Healthineers]) or EID-CT (n=3,957; Revolution Apex 256 [GE HealthCare] or Aquilion ONE ViSION 320 [Canon Medical Systems]) scanners. Subsequent invasive coronary angiography (ICA) and percutaneous or surgical revascularization were performed as part of routine clinical care. Among those referred for ICA after coronary CTA, the presence of obstructive CAD in each vessel was determined by coronary CTA (severe stenosis on visual assessment per the Coronary Artery Disease Reporting and Data System) and ICA (≥50% diameter stenosis on quantitative coronary angiography) in a blinded fashion. The diagnostic performance of EID-CT and PCD-CT was compared by using quantitative coronary angiography as the reference standard. Patients who underwent PCD-CT were less frequently referred to subsequent ICA than those undergoing EID-CT (9.9% vs 13.1%; P< 0.001). Among those who underwent ICA, revascularization was more frequently performed in the PCD-CT group than in the EID-CT group (43.4% vs 35.5%; P=0.02). In the vessel-level analysis (n=1,686), specificity (98.0% vs 93.0%; P< 0.001), positive predictive value (83.3% vs 63.0%; P=0.002), and diagnostic accuracy (97.2% vs 92.8%; P< 0.001) were improved by PCD-CT. Sensitivity (90.9% vs 90.7%; P=0.95) and negative predictive value (98.9% vs 98.7%; P=0.83) for obstructive CAD were similar between the PCD-CT and EID-CT groups, respectively. PCD-CT exhibited excellent diagnostic performance for detecting obstructive CAD. Compared with patients undergoing conventional EID-CT, fewer patients were referred to ICA after PCD-CT, but those referred were more likely to undergo revascularization.

Assessing Quality of Ultrasound Attenuation Coefficient Results for Liver Fat Quantification.

Algorithms for quantifying liver fat content based on the ultrasound attenuation coefficient (AC) are currently available; however, little is known about whether their accuracy increases by applying quality criteria such as the interquartile range-to-median ratio (IQR/M) or whether the median or average AC value should be used. AC measurements were performed with the Aplio i800 ultrasound system using the attenuation imaging (ATI) algorithm (Canon Medical Systems, Otawara, Tochigi, Japan). Magnetic resonance imaging proton density fat fraction (MRI-PDFF) was the reference standard. The diagnostic performance of the AC median value of 5 measurements (AC-M) was compared to that of AC average value (AC-A) of 5 or 3 acquisitions and different levels of IQR/M for median values or standard deviation/average (SD/A) for average values were also analyzed. Concordance between AC-5M, AC-5A, and AC3A was evaluated with concordance correlation coefficient (CCC). A total of 182 individuals (94 females; mean age, 51.2y [SD: 15]) were evaluated. A total of 77 (42.3%) individuals had S0 steatosis (MRI-PDFF < 6%), 75 (41.2%) S1 (MRI-PDFF 6-17%), 10 (5.5%) S2 (MRI-PDFF 17.1-22%), and 20 (11%) S3 (MRI-PDFF ≥ 22.1%). Concordance of AC-5A and AC-3A with AC-5M was excellent (CCC: 0.99 and 0.96, respectively). The correlation with MRI-PDFF was almost perfect. Diagnostic accuracy of AC-5M, AC-5A, and AC3A was not significantly affected by different levels of IQR/M or SD/A. The accuracy of AC in quantifying liver fat content was not affected by reducing the number of acquisitions (from five to three), by using the mean instead of the median, or by reducing the IQR/M or SD/A to ≤5%.

Weight-specific normal liver stiffness values in children.

Two-dimensional (2-D) shear wave elastography is a commonly used sonographic elastography method for the noninvasive measurement of liver stiffness. There is little liver stiffness data available in the pediatric population and its association with the child's weight is scarce. The principal aim of our study was to determine weight-specific reference liver stiffness values in a pediatric population free of liver disease. In this retrospective single-center study, 2-D shear wave elastography values were recorded in children with no history of liver disease and with a clinically indicated ultrasound examination, between April 2021 and July 2022. Examinations were performed using an Aplio i800 and two Aplio a450 (Canon Medical Systems), with a convex probe (i8CX1 or 8C1 transducers). This population was divided into ten weight groups. We evaluated the relation between weight and liver elasticity values and compared right and left lobe measurements. During the period of the study, 235 children were included. We then excluded 64 patients (weight not available = 13, interquartile range to median ratio (IQR/M) greater than 30% = 51). On the final sample (171 patients, median age 6.5years [0-18], median weight 22.6kg [2.5-80]), stiffness values showed a global significant trend to increase with weight. In each group, there was no significant difference between right and left liver stiffness values. The mean normal liver stiffness value including all children was 5.3 ± 1.1kPa. Liver stiffness in our pediatric sample with no history of liver disease increases with weight. These data may help to distinguish normal from pathological elastography values.

Utilization of Texture Analysis in Differentiating Benign and Malignant Breast Masses: Comparison of Grayscale Ultrasound, Shear Wave Elastography, and Radiomic Features.

This study aims to determine which qualitative and quantitative US features are independently associated with malignancy, including those derived from grayscale imaging morphology, shear wave elastography (SWE), and texture analysis. This single-center retrospective study was approved by the institutional research ethics board. Consecutive breast US studies performed between January and December 2020 were included. Images were acquired using a Canon Aplio i800 US unit (Canon Medical Systems, Inc., CA) and i18LX5 wideband linear matrix transducer. Grayscale US features, SWE mean, and median elasticity were obtained. Single representative grayscale images were analyzed using dedicated software (LIFEx, version 6.30). First-order and gray-level co-occurrence matrix second-order texture features were extracted. Multivariate logistic regression was performed to assess for predictors of malignancy (STATA v16.1). One hundred forty-seven cases with complete SWE data were selected for analysis (mean age 54.3, range 21-92). The following variables were found to be independently associated with malignancy: age (P <.001), family history (P = .013), irregular mass shape (P = .024), and stiffness on SWE (mean SWE ≥40 kPa; P <.001). Remaining variables (including texture features) were not found to be independently associated with malignancy (P >.05). US texture analysis features were not associated with malignancy independent of other qualitative and quantitative US characteristics currently utilized in clinical practice. This suggests texture analysis may not be warranted when differentiating benign and malignant breast masses on US. In contrast, irregular mass shape on grayscale imaging and increased stiffness on SWE were found to be independent predictors of malignancy.

Comparison of pediatric lens scattered dose measurements between axial 40-mmand helical 160-mmdetector widthcomputed tomographyscan modes.

Reports comparing field lens doses between helical scans with a 40-mm detector width and axial scans with a 160-mm detector width using different computed tomography (CT) scanners are currently scarce. To compare scatter doses for lenses between a helical scan with a 40-mm detector width and an axial scan with a 160-mm detector width when using different CT scanners in the context of pediatric chest examinations. Two different CT machines were used: Revolution CT (GE Healthcare, Waukesha, WI) with a 256-row, 0.625-mm multidetector; and Aquilion ONE GENESIS Edition (Canon Medical Systems, Otawara, Japan) with a 320-row, 0.5-mm multidetector. Three pediatric anthropomorphic phantoms were used, with optically stimulated luminescence dosimeters (OSLDs) placed on the left and right lenses. The scatter dose values measured by the OSLDs were compared between a helical scan with a 40-mm detector width and an axial scan with a 160-mm detector width during pediatric chest CT examinations. Median equivalent doses for the helical and axial scans were 0.12 and 0.12 mSv/mGy for the newborn, 0.17 and 0.16 mSv/mGy for the 1-year-old, and 0.18 and 0.15 mSv/mGy for the 5-year-old, respectively, when using the Revolution CT. With the Revolution CT, no significant differences were observed in the scatter doses between helical and axial scans in the newborn and 1-year-old phantoms. However, the lens scatter dose for the helical scan was approximately 20-35% higher than that for the axial scan in the 5-year-old phantom (P<0.01). The median equivalent doses of eye lenses for the helical and axial scans were 0.12 and 0.07 mSv/mGy for the newborn, 0.07 and 0.05 mSv/mGy for the 1-year-old, and 0.14 and 0.12 mSv/mGy for the 5-year-old, respectively, when using the Aquilion ONE. With the Aquilion ONE, lens scatter doses for the helical scan were approximately 70%, 40%, and 30% higher in the newborn, 1-year-old, and 5-year-old phantoms, respectively, than those for the axial scan (P<0.01). When using the Aquilion ONE, lens scatter doses for the helical scan were significantly higher in all three phantoms than those for the axial scan. In contrast, when using the Revolution CT, the lens scatter dose for the helical scan was significantly higher in the 5-year-old phantom than that for the axial scan. These results suggest that although scattered doses may vary with respect to the CT scanner and body size, they are generally lower in the case of axial scans.

Assessment of quantitative microflow Vascular Index in testicular cancer

PurposeUltrasound (US) is the primary imaging modality when a testicular tumor is suspected. Superb microvascular imaging (SMI) is a novel, highly sensitive Doppler technique that allows quantification of flow signals by determination of the Vascular Index (VI).The aim of the present study is to investigate the diagnostic significance of the SMI-derived VI in normal testicular tissue and testicular cancer. MethodsThis retrospective analysis included patients who underwent testicular US in our department from 2018 to 2022. Inclusion criteria were: i) sufficient image quality of the stored images, ii) US with standardized SMI-default setting (colour gain of 44 ± 5), iii) patient age ≥ 18 years, and iv) normal testicular findings or testicular tumor with histopathological workup. US examinations were performed as part of clinical routine using a high-end ultrasound system (Aplio i800/i900, Canon Medical Systems Corporation, Tochigi, Japan). Statistical analysis included Chi-square test and Mann-Whitney U tests and receiver operating characteristic (ROC) curve analysis. ResultsA total of 62 patients (31 each with normal findings and testicular tumors) were included. The VI differed statistically significantly (p < 0.001) between normal testis (median 2.5 %) and testicular tumors (median 17.4 %). Like vascular patterns (p < 0.001), the VI (p = 0.030) was shown to distinguish seminomas (median 14.8 %), non-seminomas (median 17.6 %) and lymphomas (median 34.5 %). ConclusionsIn conclusion, our study has shown the VI to be a quantitative tool that can add information for differentiating testicular tumor entities. While further confirmation in larger study populations is desirable, our results suggest that the VI may be a useful quantitative parameter.

Pixel-by-pixel correction of beam hardening artifacts by bowtie filter in fan-beam CT

Objective. Beam hardening (BH) artifacts in computed tomography (CT) images originate from the polychromatic nature of x-ray photons. In a CT system with a bowtie filter, residual BH artifacts remain when polynomial fits are used. These artifacts lead to worse visuals, reduced contrast, and inaccurate CT numbers. This work proposes a pixel-by-pixel correction (PPC) method to reduce the residual BH artifacts caused by a bowtie filter. Approach. The energy spectrum for each pixel at the detector after the photons pass through the bowtie filter was calculated. Then, the spectrum was filtered through a series of water slabs with different thicknesses. The polychromatic projection corresponding to the thickness of the water slab for each detector pixel could be obtained. Next, we carried out a water slab experiment with a mono energy E = 69 keV to get the monochromatic projection. The polychromatic and monochromatic projections were then fitted with a 2nd-order polynomial. The proposed method was evaluated on digital phantoms in a virtual CT system and phantoms in a real CT machine. Main results. In the case of a virtual CT system, the standard deviation of the line profile was reduced by 23.8%, 37.3%, and 14.3%, respectively, in the water phantom with different shapes. The difference of the linear attenuation coefficients (LAC) in the central and peripheral areas of an image was reduced from 0.010 to 0.003 cm−1 and 0.007 cm−1 to 0 in the biological tissue phantom and human phantom, respectively. The method was also validated using CT projection data obtained from Activion16 (Canon Medical Systems, Japan). The difference in the LAC in the central and peripheral areas can be reduced by a factor of two. Significance. The proposed PPC method can successfully remove the cupping artifacts in both virtual and authentic CT images. The scanned object’s shapes and materials do not affect the technique.

Does Meal or Water Intake Affect Ultrasound Attenuation Coefficient Estimate?

To assess whether meal or water intake may affect the measurement of the ultrasound (US) attenuation coefficient (AC) imaging, a parameter that is directly related to liver fat content. The study was performed in two centers (Italy and USA). AC was obtained using the ATI algorithm implemented in the Aplio i-series US systems (Canon Medical Systems, Japan) by one operator at each center. Measurements were performed at baseline and 5, 15, 30, 45 minutes after drinking 500 mL of water (group 1), or 30, 45, 60, 90, 120 minutes after eating a meal of about 600 kcal (group 2). Multilevel generalized estimating equations for repeated measures were used for the statistical analysis to consider the clustered nature of the data. Twenty-six individuals were enrolled: 11 (10 females; age, 43.7 ± 12.5 years) in Italy and 15 (10 females; age, 60.7 ± 6.3 years) in USA. At B-mode US, 10 (38.5%) had liver steatosis. The baseline AC values, in decibel/centimeter/megahertz, were 0.64 (0.12) in group 1 and 0.66 (0.13) in group 2. There was not any significant difference in AC values at every time-point after water or meal intake either in group 1 or group 2. This result did not change including sex, age, and skin-to-liver capsule into the models. The measurement of the AC, which is a biomarker of liver steatosis, does not require a fasting state and drinking water does not affect the result.

Investigation of the Effect of Tinnitus and Hearing Loss on Hippocampus Volume

Objective: This study aims to compare hippocampal changes with a correlation of audiological testing results in patients suffering from tinnitus. Methods: Patients diagnosed with tinnitus in the university hospital between February 2021 and March 2022 were prospectively included in the study by performing magnetic resonance imaging. The volume was determined by manually tracing the hippocampus' margins on the images using the Vitrea2® workstation (Canon Medical Systems Vital Images, Minnesota, USA). Statistics were used to assess the correlation between the parameters of the hearing test. Results: The distribution of the patient group (21 males, 19 females) and control group (15 males, 15 females) was uniform, and the mean ages of the two groups were 50.23±12.09 and 32.30±7.97, respectively. Significant statistical differences existed in the mean ages of the groups (p&lt;0.05). Bilateral hippocampal volumes, right bone, and air conduction all differed significantly (p&lt;0.05). The median values in the patient group were as follows: right HC 2620 mm3 (range 1600-3610), left HC 2450 mm3 (range 1610-3990), right air conduction 20 dB (range 10-61), left air 21 dB (range 11-65), and right bone 13.5 dB (range 8-49). Age was positively correlated with bilateral measurements of air and bone hearing levels (p 0.05; right air r=0.513, right bone r=0.438, left air r=0.589, left bone r=0.487). Between the 30-39 and 60-69 age groups, there was a significant difference in bone and air conduction levels (p&lt;0.05). Conclusion: In this study, it was found that the hippocampus volumes of healthy hearing people with tinnitus complaints were significantly higher in MRI examinations compared to the control group. In addition, in cases of tinnitus accompanied by bone conduction hearing loss, hippocampus volumes were found to be less than those of tinnitus alone, but not less than in the control group. It is suggested that chronic acoustic stimulation caused by tinnitus causes an increase in hippocampus volume and that problems in sensorineural integrity prevent this increase.

Noise Characteristics of Summary Maps for Brain CT Perfusion: A Simulation Study Using a Digital Phantom and Clinical Images

Cerebral CT perfusion (CTP) summary maps classify the ischemic core, penumbra, and normal tissue from traditional parametric maps, which is a criterion for indicating thrombectomy. Since perfusion maps change when the CTP radiation dose is reduced, summary maps also might change. This study aimed to assess the noise characteristics of a summary map in simulation experiments. We added various amounts of noise to a digital phantom and clinical CTPs, used Vitrea (Canon Medical Systems, Tochigi, Japan) to perform perfusion analysis, and assessed the relationship between the noise and cerebral blood volume (CBV), time to maximum (Tmax), and ischemic core and penumbra volumes. As the noise increased, the obtained CBV increased, the obtained Tmax shortened, and the obtained ischemic core and penumbra volumes decreased, which depended on the tissue's CBV and Tmax. Under low-dose conditions, the ischemic core and penumbra volumes decreased, so the criteria for thrombectomy may differ from those for standard doses.

The Influence of the Presence or Absence of a Patient Transfer Slide Board on Radiation and Image Quality When Using an Automatic Tube Current Modulation with Bed Height Compensation

The purpose of this study was to evaluate the effect of patient transfer slide boards with automatic couch height positioning compensation (AHC) on image quality and radiation dose during computed tomography (CT) examinations. The chest phantom for Kyoto Kagaku (Kyoto) Type PBU-SS 2 was performed helical scan using a Canon Medical Systems (Tochigi) 80-row CT Aquilion Prime SP/i Edition. Scan parameters were tube voltage: 120 kV, tube current: min 50 mA max 500 mA with AHC for noise index: 15, slice thickness: 5.0 mm, rotation time: 0.35 s/rotation, pitch factor: 0.813, reconstruction kernel: FC03. Filtered back projection was used for image reconstruction. We compared the image noise and volume computed tomography dose index (CTDIvol) displayed on the console with and without the patient transfer slide boards by using or not using the AHC. When using the AHC, CTDIvol was increased (p<0.05), and image noise was decreased (p<0.05). Without the AHC, there was no significant difference in CTDIvol (p=0.11) and image noise (p=0.29). The slide board utilized in this experiment did not have a notable impact on either image quality or exposure dose. Nonetheless, the use of the slide board was found to result in excessive exposure during CT scans that employed AHC.

Evaluation of the Latest Motion Correction Techniques in Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) Imaging across Different Vendors

To evaluate the robustness of the latest periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) technology from each vendor against head movements and to investigate their characteristics for effective clinical use. Using a phantom simulating the T2-weighted image of the human brain, images were acquired with devices from CANON MEDICAL SYSTEMS (Tochigi, Japan; hereinafter "Canon"), GE HealthCare (Chicago, IL, USA; hereinafter "GE"), Philips (Amsterdam, Netherlands), and Siemens Healthineers (Forchheim, Germany; hereinafter "SIEMENS"). The head motion patterns were divided into rotation angle dependency (single rotation and multiple rotations) and rotation frequency dependency and evaluated using structural similarity (SSIM). For rotation angle dependency, Canon was robust against small rotation angles and fine movements. Despite the rotation angle, GE was robust against movements, with deep learning reconstruction (DLR) improving correction functionality. Philips could be used with compressed sensitivity encoding (CS), and robustness varied with blade width. SIEMENS was robust against large movements. For rotation frequency dependency, results were similar across the 4 vendors. The rotation angle and rotation frequency dependencies of the PROPELLER technology from the 4 vendors were quantitatively evaluated. Understanding the characteristics of PROPELLER allows for the possibility of providing diagnostic-quality images even for patients who move during head MRI exams by appropriately using PROPELLER.

Evaluation of Uterine Fibroid Vascularity Using Contrast-Enhanced Ultrasound in Comparison with Contrast-Enhanced Magnetic Resonance Imaging

ObjectiveTo assess uterine fibroid vascularity using contrast-enhanced ultrasound (CEUS) comparing these findings with magnetic resonance imaging (MRI). MethodsForty women diagnosed with symptomatic uterine fibroids scheduled for uterine artery embolization (UAE) were enrolled in this IRB-approved study. Subjects underwent CEUS examination prior to UAE using an Aplio i800 scanner (Canon Medical Systems, Tustin, CA, USA) with curvilinear array (8C1). CEUS was performed using 2.0ml of the ultrasound contrast agent, Lumason (Bracco, Milan, Italy) administered intravenously. Digital CEUS clips were acquired, randomized off-line and fibroids were characterized hyper- or hypovascular. MRI was used as reference standard for fibroid vascularity and compared to CEUS. Results were analyzed using McNemar's test. ResultsForty subjects were enrolled in the trial. One patient did not proceed with the UAE procedure and one patient refused pre-procedure MRI due to claustrophobia. Therefore, 38 subjects underwent CEUS and MRI examinations prior to UAE. Hypervascular fibroids were seen on MRI and CEUS in 24 and 26 subjects, respectively. Hypovascular fibroids were seen with MRI and CEUS in 14 and 12 subjects, respectively. Fibroids characterized as hypovascular in two subjects by MRI were characterized as hypervascular by CEUS. CEUS and MRI findings were similar in 36/38 subjects corresponding to an accuracy of 95% (p = 0.62). ConclusionCEUS can accurately assess uterine fibroid vascularity serving as a potential alternative to MRI to determine vascularity of uterine fibroids.

Fundamental study on diagnostic reference level quantities for endoscopic retrograde cholangiopancreatography using a C-arm fluoroscopy system

The diagnostic reference level (DRL) is an effective tool for optimising protection in medical exposures to patients. However regarding air kerma at the patient entrance reference point (K a,r), one of the DRL quantities for endoscopic retrograde cholangiopancreatography (ERCP), manufacturers use a variety of the International Electrotechnical Commission and their own specific definitions of the reference point. The research question for this study was whether K a,r is appropriate as a DRL quantity for ERCP. The purpose of this study was to evaluate the difference between K a,r and air kerma incident on the patient’s skin surface (K a,e) at the different height of the patient couch for a C-arm system. Fluoroscopy and radiography were performed using a C-arm system (Ultimax-i, Canon Medical Systems, Japan) and a over-couch tube system (CUREVISTA Open, Fujifilm Healthcare, Japan). K a,e was measured by an ion chamber placed on the entrance surface of the phantom. Kerma-area product (P KA) and K a,r were measured by a built-in P KA meter and displayed on the fluoroscopy system. K a,e decreased while K a,r increased as the patient couch moved away from the focal spot. The uncertainty of the K a,e/K a,r ratio due to the different height of the patient couch was estimated to be 75%–94%. K a,r may not accurately represent K a,e. P KA was a robust DRL quantity that was independent of the patient couch height. We cautioned against optimising patient doses in ERCP with DRLs set in terms of K a,r without considering the patient couch height of the C-arm system. Therefore, we recommend that K a,r is an inappropriate DRL quantity in ERCP using the C-arm system.

Stress-only dynamic computed tomography perfusion protocol (CTP) alone without computed tomography coronary angiography (CCTA) has limited specificity to diagnose ischemia: A retrospective two-center study

PurposeTo investigate diagnostic performance of stress-only dynamic myocardial computed tomography perfusion (CTP) without computed tomography coronary angiography (CCTA) to diagnose ischemia with invasive fractional flow reserve (FFR) as a reference standard. Method135 datasets (68 positive for ischemia with invasive FFR < 0.8) acquired with a 256-slice CT system (Revolution, GE Healthcare, Chicago, IL, USA) were retrieved, postprocessed with a deep learning-based algorithm (Advanced intelligent Clear-IQ Engine (AiCE), Canon Medical Systems, Otawara, Japan) (FC03/cardiac kernel, 8 mm slice thickness), analyzed using a dedicated workstation (Vitrea research 7.11.0. Vital Images, Minnetonka, MN, USA), and loaded into a clinical workstation (CardIQ, GE Healthcare, Chicago, IL, USA) for review. Ten observers with various experience from two research sites evaluated the post-processed images, perfusion slices and maps to indicate presence vs absence of perfusion defect and its probability (five-point Likert scale). Binary decisions and probability scores were used to calculate sensitivity and specificity for each reader, and to create receiver operating characteristics (ROC) curves, respectively. Furthermore, the correlation coefficient (ICC) was computed. ROC AUC of a purely quantitative analysis was obtained thanks to a color-coded map with a fixed scale superimposed on myocardial walls displaying myocardial blood flow (MBF) values. ResultsThe overall case-based sensitivity and specificity for the detection of perfusion deficit were 0.79 and 0.30, respectively. No significant differences were detected in the AUC across readers (p value = 0.66). The AUC values were 0.50, 0.58, 0.63, 0.59, 0.45, 0.60, 0.56, 0.61, 0.52, 0.61. Absolute reader agreement ICC was 0.60 (good agreement) for an average case. ConclusionDynamic CTP alone has good sensitivity, but low specificity when analyzed without CCTA. These findings reinforce the need to guide the interpretation functional test with the knowledge of coronary artery anatomy.

Influence of Measurement Depth and Acquisition Parameters on Shear Wave Speed and Shear Wave Dispersion in Certified Phantoms Using a Canon Aplio Clinical Ultrasound Scanner.

The aim of the work described here was to investigate the relative contribution of confounding factors on liver shear wave speed (SWS) and shear wave dispersion slope (SWDS) measurements in three certified phantoms using a Canon Aplio clinical ultrasound scanner. A Canon Aplio i800 i-series ultrasound system (Canon Medical Systems Corporation, Otawara, Tochigi, Japan) with i8CX1 convex array (center frequency=4 MHz) was used to examine dependencies caused by the depth, width and height of the acquisition box (AQB), the depth and size of the region of interest (ROI), the AQB angle and the pressure of the ultrasound probe on the surface of the phantom. Results revealed that depth is the most significant confounder in both SWS and SWDS measurements. AQB angle, height and width and ROI size exhibited minimal confounding effects on measurements. For SWS, the most consistent measurement depth is when the top of the AQB is placed between 2 and 4 cm, and the ROI is located between 3 and 7 cm deep. For SWDS, results indicate that measurement values significantly decrease with depth from the surface of the phantom until approximately 7 cm deep, and consequently no stable area of AQB placement or ROI depth exists. In contrast to SWS, the same ideal acquisition depth range cannot necessarily be applied to SWDS measurements because of a significant depth dependency.

Diagnostic Performance of Quantitative Ultrasound Parameters in Non-alcoholic Fatty Liver Disease

Marked liver steatosis, steatohepatitis, and significant fibrosis are risk factors for unfavorable outcomes in non-alcoholic fatty liver disease (NAFLD). In this study, the diagnostic performance ofattenuation coefficient(AC), liver stiffness(LS), and dispersion slope (DS) was evaluated separately and combined in the diagnosis of liver steatosis and fibrosis in NAFLD suspects using biopsy or magnetic resonance imaging (MRI) as a reference standard. Seventy-four NAFLD suspects were prospectively imaged with an Aplio i800 ultrasound scanner (Canon Medical Systems, Tustin, CA). AC, LS, and DS measurements were obtained from the right liver lobe. Thirty-four patients underwent liver biopsy, and 40 had MRI. There were 32 patients (43%) with liver steatosis and fibrosis (S+F), 22(30%) with steatosis (S), 5 (7%) with fibrosis (F), and 15 (20%) with normal liver (N). Mean ACs were significantly higher in steatotic livers (n=54) than in non-steatotic livers (n=20) (P<0.0001). LS and DS were significantly higher in patients with liver fibrosis (n=37) compared tonon-fibrotic livers (n=37) (P=0.0004 and P=0.0002, respectively). In detecting (S+F), the area under the receiver operating characteristic curve (AUROCC) was 0.87 for combined ultrasound parameters of LS and AC (negative predictive value [NPV]: 75%, positive predictive value [PPV]: 77%, P<0.0001). In detecting patients with liver steatosis and fibrosis stage ≥2, LS had an AUROCC of 0.93 (NPV: 87%, PPV: 82%, P<0.0001). In the biopsy group, 32% (11/34) were diagnosed with non-alcoholic steatohepatitis (NASH). DS values showed a significant difference among patients with (n=23) or without (n=11) hepatocellular ballooning (P=0.02). AUROCC was 0.87 for combined ultrasound parameters of AC, LS, and DS with body mass index (BMI) in detecting NASH (NPV: 80%, PPV: 87%, P=0.0006). AC and LS showed high diagnostic value in detecting liver steatosis and fibrosis, respectively. The combined AC and LS values further improved the diagnostic accuracy in detecting NAFLD and high-risk NAFLD patients.