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Thứ Năm, 1 tháng 11, 2012

RADIOLOGY 11-2012


1.          Abstract 1 of 5 Original Research / Cardiac Imaging

Differentiation of Early from Advanced Coronary Atherosclerotic Lesions: Systematic Comparison of CT, Intravascular US, and Optical Frequency Domain Imaging with Histopathologic Examination in ex Vivo Human Hearts

Purpose: To establish an ex vivo experimental setup for imaging coronary atherosclerosis with coronary computed tomographic (CT) angiography, intravascular ultrasonography (US), and optical frequency domain imaging (OFDI) and to investigate their ability to help differentiate early from advanced coronary plaques.

Materials and Methods: All procedures were performed in accordance with local and federal regulations and the Declaration of Helsinki. Approval of the local Ethics Committee was obtained. Overall, 379 histologic cuts from nine coronary arteries from three donor hearts were acquired, coregistered among modalities, and assessed for the presence and composition of atherosclerotic plaque. To assess the discriminatory capacity of the different modalities in the detection of advanced lesions, c statistic analysis was used. Interobserver agreement was assessed with the Cohen κ statistic.

Results: Cross sections without plaque at coronary CT angiography and with fibrous plaque at OFDI almost never showed advanced lesions at histopathologic examination (odds ratio [OR]: 0.02 and 0.06, respectively; both P < .0001), while mixed plaque at coronary CT angiography, calcified plaque at intravascular US, and lipid-rich plaque at OFDI were associated with advanced lesions (OR: 2.49, P = .0003; OR: 2.60, P = .002; and OR: 31.2, P < .0001, respectively). OFDI had higher accuracy for discriminating early from advanced lesions than intravascular US and coronary CT angiography (area under the receiver operating characteristic curve: 0.858 [95% confidence interval {CI}: 0.802, 0.913], 0.631 [95% CI: 0.554, 0.709], and 0.679 [95% CI: 0.618, 0.740]; respectively, P < .0001). Interobserver agreement was excellent for OFDI and coronary CT angiography (κ = 0.87 and 0.85, respectively) and was good for intravascular US (κ = 0.66).

Conclusion: Systematic and standardized comparison between invasive and noninvasive modalities for coronary plaque characterization in ex vivo specimens demonstrated that coronary CT angiography and intravascular US are reasonably associated with plaque composition and lesion grading according to histopathologic findings, while OFDI was strongly associated. These data may help to develop initial concepts of sequential imaging strategies to identify patients with advanced coronary plaques.

© RSNA, 2012



2.          Abstract 2 of 5 Original Research / Cardiac Imaging

Coronary In-Stent Restenosis: Assessment with CT Coronary Angiography

Purpose: To compare accuracy and radiation exposure of a new computed tomographic (CT) scanner with improved spatial resolution (scanner A) with those of a CT scanner with standard spatial resolution (scanner B) for evaluation of coronary in-stent restenosis (ISR) by using invasive coronary angiography (ICA) and intravascular ultrasonography (US) as reference methods.

Materials and Methods: Written informed consent was obtained and study protocol was approved by institutional ethics committee. A total of 180 consecutive patients (154 men [mean age ± standard deviation, 66 years ± 12; range, 51–79 years] and 36 women [mean age, 70 years ± 12; range, 55–83 years]) scheduled to undergo ICA for suspected ISR were enrolled. Ninety patients were studied with scanner A (group 1: 72 men [mean age, 65 years ± 11; range, 52–79], 18 women [mean age, 68 years ± 12; range, 55–83 years]) and 90 with scanner B (group 2: 74 men [mean age, 64 years ± 10; range, 51–77 years], 16 women [mean age, 68 years ± 11; range, 55–82 years). Examination with the two scanners was compared with ICA and intravascular US. Radiation dose exposure was estimated. To compare stent evaluability between the two groups, χ2 test was used.

Results: Stent evaluability was higher in group 1 than in group 2 (99% vs 92%, P = .0021). A significantly lower rate of beam-hardening artifact was observed in group 1 (two cases) than group 2 (12 cases, P < .05). For stent-based analysis, sensitivity, specificity, and accuracy of multidetector CT for ISR identification were 96%, 95%, and 96% in group 1 and 90%, 91%, and 91% in group 2, respectively, without statistically significant differences. The correlation between percent ISR evaluated at multidetector CT versus intravascular US was higher in group 1 than in group 2 (r = 0.89 vs r = 0.58; P = .019). The correlations of diameter and area measurements at reference site and stent maximal lumen narrowing site between multidetector CT and intravascular US were higher in group 1 than in group 2. Radiation dose was low in both multidetector CT groups (1.9 mSv ± 0.2).

Conclusion: Scanner A, with improved spatial resolution, allowed reliable detection and quantification of coronary ISR with low radiation exposure.

© RSNA, 2012



3.          Abstract 3 of 5 Original Research / Genitourinary Imaging

Angiomyolipoma with Minimal Fat: Can It Be Differentiated from Clear Cell Renal Cell Carcinoma by Using Standard MR Techniques?

Purpose: To retrospectively assess whether magnetic resonance (MR) imaging with opposed-phase and in-phase gradient-echo (GRE) sequences and MR feature analysis can differentiate angiomyolipomas (AMLs) that contain minimal fat from clear cell renal cell carcinomas (RCCs), with particular emphasis on small (<3-cm masses.="masses." o:p="o:p">

Materials and Methods: Institutional review board approval and a waiver of informed consent were obtained for this HIPAA-compliant study. MR images from 108 pathologically proved renal masses (88 clear cell RCCs and 20 minimal fat AMLs from 64 men and 44 women) at two academic institutions were evaluated. The signal intensity (SI) of each renal mass and spleen on opposed-phase and in-phase GRE images was used to calculate an SI index and tumor-to-spleen SI ratio. Two radiologists who were blinded to the pathologic results independently assessed the subjective presence of intravoxel fat (ie, decreased SI on opposed-phase images compared with that on in-phase images), SI on T1-weighted and T2-weighted images, cystic degeneration, necrosis, hemorrhage, retroperitoneal collaterals, and renal vein thrombosis. Results were analyzed by using the Wilcoxon rank sum test, two-tailed Fisher exact test, and multivariate logistic regression analysis for all renal masses and for small masses. A P value of less than .05 was considered to indicate a statistically significant difference.

Results: There were no differences between minimal fat AMLs and clear cell RCCs for the SI index (8.05% ± 14.46 vs 14.99% ± 19.9; P = .146) or tumor-to-spleen ratio (−8.96% ± 16.6 and −15.8% ± 22.4; P = .227) when all masses or small masses were analyzed. Diagnostic accuracy (area under receiver operating characteristic curve) for the SI index and tumor-to-spleen ratio was 0.59. Intratumoral necrosis and larger size were predictive of clear cell RCC (P < .001) for all lesions, whereas low SI (relative to renal parenchyma SI) on T2-weighted images, smaller size, and female sex correlated with minimal fat AML (P < .001) for all lesions.

Conclusion: The diagnostic accuracy of opposed-phase and in-phase GRE MR imaging for the differentiation of minimal fat AML and clear cell RCC is poor. In this cohort, low SI on T2-weighted images relative to renal parenchyma and small size suggested minimal fat AML, whereas intratumoral necrosis and large size argued against this diagnosis.

© RSNA, 2012

4.          Abstract 4 of 5 Original Research / Ultrasonography

Obstruction at Middle Hepatic Venous Tributaries in Modified Right Lobe Grafts after Living-Donor Liver Transplantation: Diagnosis with Contrast-enhanced US

Purpose: To investigate the ability of contrast material–enhanced ultrasonography (US) to help diagnose obstruction of middle hepatic venous (MHV) tributaries soon after living-donor liver transplantation with modified right lobe grafts.

Materials and Methods: The institutional review board approved the study and waived requirement for informed consent. Sixty-five consecutive patients (48 men, 17 women; mean age, 52.8 years; range, 33–69 years) who underwent living-donor liver transplantation with modified right lobe grafts between February and May 2009 were included. All patients underwent contrast-enhanced US and Doppler US on postoperative day 1 and underwent computed tomography (CT) within 7 days after US. At contrast-enhanced US, parenchymal enhancement patterns in the territory of each MHV tributary during arterial and portal venous phases were evaluated. With use of most frequent enhancement patterns in patients with obstruction at MHV tributaries as a criterion, diagnostic performance of contrast-enhanced US was compared with that of Doppler US for diagnosis of obstruction at MHV tributaries; CT was the reference standard. Generalized estimating equations were used to adjust for data clustering.

Results: Of 148 MHV tributaries in 65 patients, 36 (24.3%) in 31 patients were diagnosed as obstructed at CT. With arterial high echogenicity or portal low echogenicity used as a criterion for hepatic venous obstruction, contrast-enhanced US had sensitivity, specificity, and accuracy of 91% (33 of 36), 97% (109 of 112), and 95% (142 of 148), respectively, whereas Doppler US had values of 83% (30 of 36), 86% (97 of 112), and 85% (127 of 148), respectively. Contrast-enhanced US was significantly more specific and accurate than Doppler US for diagnosis of obstruction at MHV tributaries (P = .024 and .01, respectively). Arterial high echogenicity was noted only in the hepatic venous obstruction group.

Conclusion: Contrast-enhanced US can help accurately assess hepatic venous obstruction at MHV tributaries after living-donor liver transplantation with a modified right lobe graft. Contrast-enhanced US was significantly more specific than Doppler US, with arterial hyperenhancement in the affected area being specific to hepatic venous obstruction.

© RSNA, 2012

5.          Abstract 5 of 5 Communications / Letter to the Editor

          
Measurement of Muscle Stiffness in Children with Spastic Cerebral Palsy Radiology November 2012 265:2 647; doi:10.1148/radiol.12121223

Editor:

We read with great interest the article in the June 2012 issue of Radiology by Kwon and colleagues (1), who used sonoelastography to demonstrate a difference in stiffness of the medial gastrocnemius muscle between healthy children and those with spastic cerebral palsy. The authors provided a new insight about biomechanical assessment of spasticity in addition to the neurophysiologic aspect.

 
Measurement of muscle stiffness may be more complicated than measurements of the tendons or the plantar fascia (2) because more factors must be controlled. We note that the authors performed sonoelastography while subjects were in a prone position with feet hanging from the edge, but no information was provided regarding the angle of the ankle when performing the measurement. Stiffness of the biarticular gastrocnemius muscle may be increased …

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