Sara Lewis

Diffusion-weighted imaging of the liver: techniques and applications.

Diffusion-weighted imaging (DWI) is a technique that assesses the cellularity, tortuosity of the extracellular/extravascular space, and cell membrane density based on differences in water proton mobility in tissues. The strength of the diffusion weighting is reflected by the b value. DWI using several b values enables the quantification of the apparent diffusion coefficient. DWI is increasingly used in liver imaging for multiple reasons: it can add useful qualitative and quantitative information to conventional imaging sequences; it is acquired relatively quickly; it is easily incorporated into existing clinical protocols; and it is a noncontrast technique.

Hepatocellular Carcinoma in Chronic Hepatitis C in the Absence of Advanced Fibrosis or Cirrhosis

OBJECTIVE The objective of our study was to describe the cross-sectional imaging appearance of hepatocellular carcinoma (HCC) in patients with chronic hepatitis C virus (HCV) infection in the absence of advanced fibrosis and cirrhosis. MATERIALS AND METHODS This study is a retrospective review of our surgical database to identify patients with chronic HCV infection and HCC who underwent hepatectomy and who had undergone preoperative CT or MRI. Only patients with a Metavir fibrosis score of F0, F1, or F2 on pathology were included. Patients with hepatitis B virus coinfection or other causes of chronic liver disease and patients with histopathologic evidence of advanced fibrosis or cirrhosis (Metavir scores F3 and F4) were excluded. Contrast-enhanced CT or MRI examinations performed within 2 months before surgery were reviewed for the number, size, and location of tumors; tumor enhancement characteristics; and presence of macrovascular invasion. RESULTS Two hundred forty-five resections of HCC in patients with HCV were performed in our institution from 1987 to 2012. Of this group, 26 patients (10.6%) had a Metavir fibrosis score of F0, F1, or F2; of those patients, 19 (18 men and one woman; 18 non-Asian patients and one Asian patient; mean age, 64 years) had imaging studies available for review. Twenty-one HCCs (mean size, 4.5 cm; range, 0.9-14.8 cm) were evaluated at imaging. Typical wash-in and washout characteristics were seen in 16 of 19 viable lesions (84.2%). The remaining two HCCs were completely necrotic after transarterial chemoembolization. Eighteen patients had a solitary tumor. Most tumors (15/21, 71.4%) developed in the right hepatic lobe. CONCLUSION HCC can develop in patients with chronic HCV without advanced fibrosis or cirrhosis, most frequently in older non-Asian men, and usually appears as a large solitary tumor with a typical wash-in-washout enhancement pattern.

Quantification of hepatocellular carcinoma heterogeneity with multiparametric magnetic resonance imaging

Tumour heterogeneity poses a significant challenge for treatment stratification. The goals of this study were to quantify heterogeneity in hepatocellular carcinoma (HCC) using multiparametric magnetic resonance imaging (mpMRI), and to report preliminary data correlating quantitative MRI parameters with advanced histopathology and gene expression in a patient subset. Thirty-two HCC patients with 39 HCC lesions underwent mpMRI including diffusion-weighted imaging (DWI), blood-oxygenation-level-dependent (BOLD), tissue-oxygenation-level-dependent (TOLD) and dynamic contrast-enhanced (DCE)-MRI. Histogram characteristics [central tendency (mean, median) and heterogeneity (standard deviation, kurtosis, skewness) MRI parameters] in HCC and liver parenchyma were compared using Wilcoxon signed-rank tests. Histogram data was correlated between MRI methods in all patients and with histopathology and gene expression in 14 patients. HCCs exhibited significantly higher intra-tissue heterogeneity vs. liver with all MRI methods (P < 0.030). Although central tendency parameters showed significant correlations between MRI methods and with each of histopathology and gene expression, heterogeneity parameters exhibited additional complementary correlations between BOLD and DCE-MRI and with histopathologic hypoxia marker HIF1α and gene expression of Wnt target GLUL, pharmacological target FGFR4, stemness markers EPCAM and KRT19 and immune checkpoint PDCD1. Histogram analysis combining central tendency and heterogeneity mpMRI features is promising for non-invasive HCC characterization on the imaging, histologic and genomics levels.

Distal Embolic Protection for Infrainguinal Interventions: How to and When?

Distal embolization is a well-recognized complication during lower extremity revascularization procedures. Preliminary work has shown safety and feasibility of the use of embolic protection devices in this vascular territory. While many interventionalists believe that this technology offers a clear benefit for infrainguinal use based on the clinical safety data seen in other vascular beds, others believe that the exact role is poorly defined. All clinical experience to date has been with devices designed for other vascular territories and this has created a unique set of technical obstacles and potential risks. At present, clinical use is increasing despite a lack of data regarding which patients are at greatest risk for distal embolization, which anatomy is appropriate for the use of this technology, and which device, if any, is ideally suited for the infrainguinal arterial circulation. In addition, the clinical relevance and effect of distal embolization in the lower extremity remains poorly understood. Ultimately, more trial data may be necessary to substantiate the increased use of distal protection devices in infrainguinal interventions to justify the increase in cost, complexity, and potential risks associated with the use of this technology.

Patient-directed Internet-based Medical Image Exchange:

RATIONALE AND OBJECTIVES Inefficient transfer of personal health records among providers negatively impacts quality of health care and increases cost. This multicenter study evaluates the implementation of the first Internet-based image-sharing system that gives patients ownership and control of their imaging exams, including assessment of patient satisfaction. MATERIALS AND METHODS Patients receiving any medical imaging exams in four academic centers were eligible to have images uploaded into an online, Internet-based personal health record. Satisfaction surveys were provided during recruitment with questions on ease of use, privacy and security, and timeliness of access to images. Responses were rated on a five-point scale and compared using logistic regression and McNemars test. RESULTS A total of 2562 patients enrolled from July 2012 to August 2013. The median number of imaging exams uploaded per patient was 5. Most commonly, exams were plain X-rays (34.7%), computed tomography (25.7%), and magnetic resonance imaging (16.1%). Of 502 (19.6%) patient surveys returned, 448 indicated the method of image sharing (Internet, compact discs [CDs], both, other). Nearly all patients (96.5%) responded favorably to having direct access to images, and 78% reported viewing their medical images independently. There was no difference between Internet and CD users in satisfaction with privacy and security and timeliness of access to medical images. A greater percentage of Internet users compared to CD users reported access without difficulty (88.3% vs. 77.5%, P < 0.0001). CONCLUSION A patient-directed, interoperable, Internet-based image-sharing system is feasible and surpasses the use of CDs with respect to accessibility of imaging exams while generating similar satisfaction with respect to privacy.

Multimodality imaging of fibromuscular dysplasia

ObjectiveFibromuscular dysplasia (FMD) is an uncommon non-inflammatory and non-atherosclerotic cause of arterial disease that may result in stenosis, tortuosity, aneurysm, or dissection. The clinical presentation depends on the vascular bed involved and ranges from asymptomatic to multisystem disease and end organ ischemia. The purpose of this article is to review the role of imaging in patients with FMD with an emphasis on renal FMD. The relevant epidemiology, histopathology, imaging techniques, and interpretation of images will be discussed.ConclusionRenal artery FMD requires a high index of suspicion for accurate and prompt diagnosis and implementation of appropriate therapy. The treatment will vary based on clinical presentation and distribution of involvement. Noninvasive imaging with duplex ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) are reasonable alternatives for the depiction of FMD in comparison to catheter-directed angiography (CA). Patients with FMD are often treated by multispecialty practice including the interventional radiologist.

Magnetic resonance imaging of a small vessel hepatic hemangioma in a cirrhotic patient with histopathologic correlation.

The authors report and discuss a rare case of a small vessel hepatic hemangioma in a 59-year-old patient with liver cirrhosis, which was pre-procedurally characterized as indeterminate due to atypical magnetic resonance imaging (MRI) features. This manuscript reviews the MRI features with pathologic correlation, emphasizes the importance of accurate characterization of liver lesions, and discusses the role of biopsy. We believe this is the first reported case of a small vessel hemangioma in liver cirrhosis with imaging and histopathologic correlation.

Locoregional therapies for hepatocellular carcinoma and the new LI-RADS treatment response algorithm

Radiologists play a central role in the assessment of patient response to locoregional therapies for hepatocellular carcinoma (HCC). The identification of viable tumor following treatment guides further management and potentially affects transplantation eligibility. Liver Imaging Reporting and Data Systems (LI-RADS) first introduced the concept of LR-treated in 2014, and a new treatment response algorithm is included in the 2017 update to assist radiologists in image interpretation of HCC after locoregional therapy. In addition to offering imaging criteria for viable and nonviable HCC, new concepts of nonevaluable tumors as well as tumors with equivocal viability are introduced. Existing guidelines provided by response evaluation criteria in solid tumors (RECIST) and modified RECIST address patient-level assessments and are routinely used in clinical trials but do not address the variable appearances following different locoregional therapies. The new LI-RADS treatment response algorithm addresses this gap and offers a comprehensive approach to assess treatment response for individual lesions after a variety of locoregional therapies, using either contrast-enhanced CT or MRI.

Diffusion-Weighted Imaging of the Liver in Patients With Chronic Liver Disease: Comparison of Monopolar and Bipolar Diffusion Gradients for Image Quality and Lesion Detection

OBJECTIVE The objective of our study was to compare diffusion-weighted imaging (DWI) sequences using a bipolar versus a monopolar single-shot echo-planar imaging (EPI) gradient design for image quality and for lesion detection and characterization in patients with liver disease. MATERIALS AND METHODS In this retrospective study, 77 patients with chronic liver disease who underwent MRI including bipolar and monopolar DWI at 1.5 T were assessed. Two independent observers reviewed the DWI studies for image quality and the detection and characterization of liver lesions. The reference standard for diagnosis was established by consensus review of two different observers using imaging characteristics on conventional MRI sequences, lesion stability over time, pathologic correlation, or a combination of these findings. The estimated signal-to-noise ratio (SNR) of liver parenchyma and apparent diffusion coefficients (ADCs) of the liver and lesions were calculated for both sequences. ROC analysis was conducted to evaluate the performance of ADC for the diagnosis of hepatocellular carcinoma (HCC). RESULTS Eighty-five lesions, 50 HCCs and 35 benign lesions, were detected with the reference standard in 38 patients. There was equivalent image quality for the bipolar and monopolar sequences (p = 0.24-0.42). The HCC detection rate for observers 1 and 2 was slightly better with bipolar DWI (50.0% and 52.0%, respectively) compared with monopolar DWI (44.0% and 46.0%); however, this difference did not reach statistical significance. The estimated SNR was higher with the monopolar sequence than with the bipolar sequence (p ≤ 0.001). The AUC for the ROC curve was 0.691 for bipolar DWI and 0.649 for monopolar DWI when ADC was used for the characterization of HCC, which is not a statistically significant difference (p = 0.59). CONCLUSION The higher estimated SNR yielded by the monopolar DWI sequence did not translate into better HCC detection compared with the bipolar DWI sequence. ADC has a limited role for HCC characterization in patients with liver disease.

DCE-MRI of the prostate using shutter-speed vs. Tofts model for tumor characterization and assessment of aggressiveness

To quantify Tofts model (TM) and shutter‐speed model (SSM) perfusion parameters in prostate cancer (PCa) and noncancerous peripheral zone (PZ) and to compare the diagnostic performance of dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) to Prostate Imaging and Reporting and Data System (PI‐RADS) classification for the assessment of PCa aggressiveness.