Adeel R. Seyal

CT of the Abdomen with Reduced Tube Voltage in Adults: A Practical Approach

Recent innovations in computed tomographic (CT) hardware and software have allowed implementation of low tube voltage imaging into everyday CT scanning protocols in adults. CT at a low tube voltage setting has many benefits, including (a) radiation dose reduction, which is crucial in young patients and those with chronic medical conditions undergoing serial CT examinations for disease management; and (b) higher contrast enhancement. For the latter, increased attenuation of iodinated contrast material improves the evaluation of hypervascular lesions, vascular structures, intestinal mucosa in patients with bowel disease, and CT urographic images. Additionally, the higher contrast enhancement may provide diagnostic images in patients with renal dysfunction receiving a reduced contrast material load and in patients with suboptimal peripheral intravenous access who require a lower contrast material injection rate. One limitation is that noisier images affect image quality at a low tube voltage setting. The development of denoising algorithms such as iterative reconstruction has made it possible to perform CT at a low tube voltage setting without compromising diagnostic confidence. Other potential pitfalls of low tube voltage CT include (a) photon starvation artifact in larger patients, (b) accentuation of streak artifacts, and (c) alteration of the CT attenuation value, which may affect evaluation of lesions on the basis of conventional enhancement thresholds. CT of the abdomen with a low tube voltage setting is an excellent radiation reduction technique when properly applied to imaging of select patients in the appropriate clinical setting.

Reproducibility of mRECIST in assessing response to transarterial radioembolization therapy in hepatocellular carcinoma

The purpose of our study was to evaluate the reproducibility of Modified Response Evaluation Criteria in Solid Tumors (mRECIST) in hepatocellular carcinoma (HCC) lesions undergoing transarterial radioembolization (TARE) therapy and to determine whether mRECIST reproducibility is affected by the enhancement pattern of HCC. One hundred and three HCC lesions from 103 patients treated with TARE were evaluated. The single longest diameter of viable tumor tissue was measured by two radiologists at baseline; response to therapy was evaluated according to mRECIST. The enhancement pattern of HCC lesions was correlated with their mRECIST response. The response rate between mRECIST and RECIST 1.1 was compared. Wilcoxon signed‐rank test, paired t test, Lins concordance correlation coefficient (ρc), Bland‐Altman plot, kappa statistics, and Fishers exact test were used to assess intra‐ and interobserver reproducibilities and to compare response rates. There were better intra‐ than interobserver agreements in the measurement of single longest diameter of viable tumor tissue (bias = 0 cm intraobserver versus bias = 0.3 cm interobserver). For mRECIST, good intraobserver (ĸ = 0.70) and moderate interobserver (ĸ = 0.56) agreements were noted. The mRECIST response for HCC lesions with homogeneous enhancement at both baseline and follow‐up imaging showed better intra‐ and interobserver agreements (ĸ = 0.77 and 0.60, respectively) than lesions with heterogeneous enhancement at both scans (ĸ = 0.54 and 0.40, respectively). In the early follow‐up period mRECIST showed a significantly higher response rate than RECIST (40.8% versus 3.9%; P = 0.025). Conclusions: In HCC patients treated with TARE, mRECIST captures a significantly higher response rate compared with RECIST; it also demonstrates acceptable intra‐ and interobserver reproducibilities for HCC lesions treated with TARE, and mRECIST reproducibility may be lower for HCC lesions with heterogeneous distribution of the viable tumor tissue. (Hepatology 2015;62:1111‐1121)

Current Guidelines for the Diagnosis and Management of Hepatocellular Carcinoma: A Comparative Review

OBJECTIVE The purpose of this article is to review aspects of guidelines pertinent to radiologists involved in the diagnosis or treatment of hepatocellular carcinoma. CONCLUSION Early diagnosis and treatment of hepatocellular carcinoma are important because only 10% of patients meet the criteria for curative therapy at the time of diagnosis. Several organizations have developed guidelines for screening, diagnosis, and treatment of hepatocellular carcinoma. Radiologists play a pivotal role in every aspect of these guidelines.

Pancreatic Mucinous Cystic Neoplasm Size Using CT Volumetry, Spherical and Ellipsoid Formulas: Validation Study

CONTEXT The accuracy for determining pancreatic cyst volume with commonly used spherical and ellipsoid methods is unknown. The role of CT volumetry in volumetric assessment of pancreatic cysts needs to be explored. OBJECTIVES To compare volumes of the pancreatic cysts by CT volumetry, spherical and ellipsoid methods and determine their accuracy by correlating with actual volume as determined by EUS-guided aspiration. Setting This is a retrospective analysis performed at a tertiary care center. Patients Seventy-eight pathologically proven pancreatic cysts evaluated with CT and endoscopic ultrasound (EUS) were included. Design The volume of fourteen cysts that had been fully aspirated by EUS was compared to CT volumetry and the routinely used methods (ellipsoid and spherical volume). Two independent observers measured all cysts using commercially available software to evaluate inter-observer reproducibility for CT volumetry. MAIN OUTCOME MEASURES The volume of pancreatic cysts as determined by various methods was compared using repeated measures analysis of variance. Bland-Altman plot and intraclass correlation coefficient were used to determine mean difference and correlation between observers and methods. The error was calculated as the percentage of the difference between the CT estimated volumes and the aspirated volume divided by the aspirated one. RESULTS CT volumetry was comparable to aspirated volume (P=0.396) with very high intraclass correlation (r=0.891, P<0.001) and small mean difference (0.22 mL) and error (8.1%). Mean difference with aspirated volume and error were larger for ellipsoid (0.89 mL, 30.4%; P=0.024) and spherical (1.73 mL, 55.5%; P=0.004) volumes than CT volumetry. There was excellent inter-observer correlation in volumetry of the entire cohort (r=0.997, P<0.001). CONCLUSIONS CT volumetry is accurate and reproducible. Ellipsoid and spherical volume overestimate the true volume of pancreatic cysts.

Cross-sectional imaging of perforated gallbladder

Gallbladder perforation is a potentially life-threatening condition commonly seen as a complication of acute cholecystitis. Urgent surgical intervention is often needed to reduce serious morbidity and mortality. It presents a diagnostic challenge due to nonspecific symptoms, leading to a delay in diagnosis. Imaging plays a vital role in early identification of this potentially fatal condition and evaluation by more than one imaging modality may be required to make the diagnosis. Knowledge of specific and ancillary imaging findings is crucial to avoid misdiagnosis. In this article, we will review the risk factors, pathophysiology, and surgical classification of gallbladder perforation and discuss the role of multimodality imaging in its diagnosis. Differential diagnoses on imaging will also be discussed.

CT of Atypical and Uncommon Presentations of Hepatocellular Carcinoma

OBJECTIVE The purpose of this article is to familiarize radiologists with uncommon presentations of hepatocellular carcinoma (HCC) with an emphasis on the CT spectrum of atypical appearances. CONCLUSION HCC is the fifth most common neoplasm worldwide and the second most common cause of cancer-related death. In many cases, HCC can be confidently diagnosed with noninvasive imaging. However, there are numerous unusual appearances of HCC with which the radiologist must be familiar.

Sharing a Collection of Radiology Educational Websites as Bookmarks Among Radiologists

a m r t a q c DESCRIPTION OF THE PROBLEM With the explosion of online medical education material, in particular radiology education websites, the majority of medical students and trainees now prefer Googling radiology educational topics for their basic education and quick consults over conventional textbooks [1-5]. Web-based learning is attractive for a variety of reasons: It is widely available, inexpensive, and easily accessible from desktop computers, laptops, and portable devices such as smart phones and tablet computers. This dramatic shift in the learning paradigm is a challenge because the quality of information available at these websites is immensely variable. In a recent survey [2], it was found that 42% of radiologists use the Internet at least once a day and that 97% of radiologists use the Internet for education. Also striking was that 84% of survey respondents reported increasing their use of the Internet for gathering radiology information significantly in the past 3 years. Online resources include teaching files, case collections, web-based lectures, training modules, openaccess electronic journals, traditional journals with online content, and podcasts. With the overwhelming amount of educational content available on the Internet, it is difficult for trainees and practitioners to ascertain which websites have current and trustworthy information. Valuable time may be wasted before this information is reliably obtained [3,6]. Although recent

Threshold for Enhancement in Treated Hepatocellular Carcinoma on MDCT: Effect on Necrosis Quantification.

OBJECTIVE The objective of our study was to determine whether the conventionally used enhancement threshold of 10 HU for assessing tumor viability in treated hepatocellular carcinoma (HCC) lesions is valid. MATERIALS AND METHODS To distinguish pseudoenhancement from enhancement in a tumor, we used an in vivo model: The attenuation of 54 hepatic cysts during the unenhanced and portal venous phases of MDCT, similar to what may be observed in HCC with central necrosis, was used to determine the threshold for pseudoenhancement. To validate this model, we compared the attenuation value of liver parenchyma in this cohort with that of 22 HCCs during the late arterial phase of enhancement. We tested the effect of this pseudoenhancement on quantifying necrosis in HCC compared with the conventionally used threshold of 10 HU. RESULTS Values of enhancing HCC tissue on arterial phase MDCT (mean, 121.3 HU) were comparable with normal liver parenchyma on venous phase MDCT (117.3 HU) (p = 0.27). The threshold of 17.1 HU was the best threshold for the detection of pseudoenhancement in cysts (99% accuracy, 100% sensitivity, and 98% specificity). When this threshold was used instead of the conventional threshold of 10 HU, the mean necrosis proportion of treated HCC increased from 34.0% to 42.6% and the mean viable tumor proportion decreased from 66.0% to 57.4%. The quantification of viable HCC tissue based on 10 HU and the quantification of viable HCC tissue based on 17.1 HU were found to be significantly different (p < 0.0001). CONCLUSION The threshold of 17.1 HU may be the appropriate cutoff for nonenhancement in a necrotic HCC. Use of this threshold may potentially affect how response to therapy is quantified and categorized.

Tricky Findings in Liver Transplant Imaging: A Review of Pitfalls With Solutions

Orthotopic liver transplantation is the preferred treatment for end-stage liver disease. Imaging plays an important role in the follow-up of transplant recipients by identifying a variety of complications. Posttransplant liver imaging can be challenging with altered vascular and nonvascular postoperative findings closely mimicking pathologies. A thorough knowledge of these common imaging findings in a posttransplant liver is essential for the radiologist to avoid erroneous diagnoses and unnecessary workup. We focus on such imaging findings and provide tips to avoid misinterpretation.

The combined effect of multidetector-row computed tomographic tube voltage, tube current, and image reconstruction algorithm on the detection of pneumothorax after intervention.

Objectives The objective of the study was to determine the lowest multidetector-row computed tomographic radiation dose parameters for the detection of pneumothorax after thoracic intervention. Materials and Methods An anthropomorphic chest phantom containing pneumothoraces was imaged with different tube voltages (80, 100, and 120 kV[p]) and tube currents (10, 20, 40, 75, and 110 mAs). The images were reconstructed with both filtered back projection (FBP) and iterative reconstruction (IR) algorithms. Two blinded radiologists scored images independently for the presence or absence of pneumothorax. Effective dose, image noise, contrast-to-noise ratio, and signal-to-noise ratio were recorded. Results At radiation dose below 0.48 mSv, sensitivity for the detection of pneumothorax decreased in both reconstruction algorithms (80% for FBP vs 83% for IR; P > 0.05). Interobserver agreement was good (k = 0.78). The IR data sets showed lower image noise as well as higher signal-to-noise ratio and contrast-to-noise ratio when compared with FBP on all acquisition parameters (P < 0.0001). Conclusions Very low computed tomographic dose parameters may be suitable for confident detection of small pneumothoraces after intervention.