Orpheus Kolokythas

High-Intensity Focused Ultrasound : Current Potential and Oncologic Applications

OBJECTIVE The objective of this article is to introduce the reader to the principles and applications of high-intensity focused ultrasound (HIFU). CONCLUSION Although a great deal about HIFU physics is understood, its clinical applications are currently limited, and multiple trials are underway worldwide to determine its efficacy.

Safety and efficacy of video-assisted retroperitoneal debridement for infected pancreatic collections: a multicenter, prospective, single-arm phase 2 study.

BACKGROUND The feasibility of video-assisted retroperitoneal debridement (VARD) for infected pancreatic walled-off necrosis is established. We provide prospective data on the safety and efficacy of VARD. DESIGN Multicenter, prospective, single-arm phase 2 study. SETTING Six academic medical centers. PATIENTS We evaluated 40 patients with pancreatic necrosis who had infection determined using Gram stain or culture. INTERVENTIONS Percutaneous drains were placed at enrollment, and computed tomographic scans were repeated at 10 days. Patients who had more than a 75% reduction in collection size were treated with drains. Other patients were treated with VARD. Crossover to open surgery was performed for technical reasons and/or according to surgeon judgment. MAIN OUTCOME MEASURES Efficacy (ie, successful VARD treatment without crossover to open surgery or death) and safety (based on mortality and complication rates). Patients received follow-up care for 6 months. RESULTS We enrolled 40 patients (24 men and 16 women) during a 51-month period. Median age was 53 years (range, 32-82 years). Mean (SD) Acute Physiology and Chronic Health Evaluation II score at enrollment was 8.0 (5.1), and median computed tomography severity index score was 8. Of the 40 patients, 24 (60%) were treated with minimally invasive intervention (drains with or without VARD). Nine patients (23%) did not require surgery (drains only). For 31 surgical patients, VARD was possible in 60% of patients. Most patients (81%) required 1 operation. In-hospital 30-day mortality was 2.5% (intent-to-treat). Bleeding complications occurred in 7.5% of patients; enteric fistulas occurred in 17.5%. CONCLUSIONS This prospective cohort study supports the safety and efficacy of VARD for infected pancreatic walled-off necrosis. Of the patients, 85% were eligible for a minimally invasive approach. We were able to use VARD in 60% of surgical patients. The low mortality and complication rates compare favorably with open debridement. An unexpected finding was that a reduction in collection size of 75% according to the results of computed tomographic scans at 10 to 14 days predicted the success of percutaneous drainage alone.

Imaging of Uncommon Retroperitoneal Masses

Retroperitoneal masses not arising from major solid organs are uncommon. Although there is no simple method of classifying retroperitoneal masses, a reasonable approach is to consider the masses as predominantly solid or cystic and to subdivide these into neoplastic and nonneoplastic masses. Because the treatment options vary, it is useful to be able to differentiate these masses by using imaging criteria. Although the differential diagnosis of retroperitoneal masses can be narrowed down to a certain extent on the basis of imaging characteristics, patterns of involvement, and demographics, there is still a considerable overlap of imaging findings for these masses, and histologic examination is often required for definitive diagnosis. Computed tomography (CT) and magnetic resonance (MR) imaging play an important role in characterization and in the assessment of the extent of the disease and involvement of adjacent and distant structures. Familiarity with the CT and MR imaging features of various retroperitoneal masses will facilitate accurate diagnosis and staging for aggressive lesions.

Impact of operator-selected image noise index and reconstruction slice thickness on patient radiation dose in 64-MDCT

OBJECTIVE Our objective was to develop a better understanding of the complex interrelationship between image noise, reconstruction slice thickness, and patient radiation dose on a 64-MDCT scanner that uses automated tube current modulation. MATERIALS AND METHODS We reviewed physics theory and performed phantom dose measurements on a 64-MDCT scanner while altering operator-selectable image noise and reconstruction slice thickness. RESULTS Using phantom dose measurements to adjust theoretic predictions, we constructed both a spreadsheet and a graph that visually display the interrelationships between operator-selected image noise and reconstruction slice thickness and the resulting patient dose. CONCLUSION This table and graph may help operators understand the trade-offs when prospectively trying to minimize dose and optimize image noise for selected reconstruction slice thicknesses on this type of 64-MDCT scanner.

Model-Based Iterative Reconstruction Versus Adaptive Statistical Iterative Reconstruction and Filtered Back Projection in Liver 64-MDCT: Focal Lesion Detection, Lesion Conspicuity, and Image Noise

OBJECTIVE The purpose of this study is to compare three CT image reconstruction algorithms for liver lesion detection and appearance, subjective lesion conspicuity, and measured noise. MATERIALS AND METHODS Thirty-six patients with known liver lesions were scanned with a routine clinical three-phase CT protocol using a weight-based noise index of 30 or 36. Image data from each phase were reconstructed with filtered back projection (FBP), adaptive statistical iterative reconstruction (ASIR), and model-based iterative reconstruction (MBIR). Randomized images were presented to two independent blinded reviewers to detect and categorize the appearance of lesions and to score lesion conspicuity. Lesion size, lesion density (in Hounsfield units), adjacent liver density (in Hounsfield units), and image noise were measured. Two different unblinded truth readers established the number, appearance, and location of lesions. RESULTS Fifty-one focal lesions were detected by truth readers. For blinded reviewers compared with truth readers, there was no difference for lesion detection among the reconstruction algorithms. Lesion appearance was statistically the same among the three reconstructions. Although one reviewer scored lesions as being more conspicuous with MBIR, the other scored them the same. There was significantly less background noise in air with MBIR (mean [± SD], 2.1 ± 1.4 HU) than with ASIR (8.9 ± 1.9 HU; p < 0.001) or FBP (10.6 ± 2.6 HU; p < 0.001). Mean lesion contrast-to-noise ratio was statistically significantly higher for MBIR (34.4 ± 29.1) than for ASIR (6.5 ± 4.9; p < 0.001) or FBP (6.3 ± 6.0; p < 0.001). CONCLUSION In routine-dose clinical CT of the liver, MBIR resulted in comparable lesion detection, lesion characterization, and subjective lesion conspicuity, but significantly lower background noise and higher contrast-to-noise ratio compared with ASIR or FBP. This finding suggests that further investigation of the use of MBIR to enable dose reduction in liver CT is warranted.

Ultrasound-Based Elastography: A Novel Approach to Assess Radio Frequency Ablation of Liver Masses Performed With Expandable Ablation Probes A Feasibility Study

Objective. The purpose of this study was to evaluate the technical feasibility of ultrasound‐based elastography as a tool for assessing the size and shape of the coagulation necrosis caused by radio frequency ablation (RFA) probes using expandable electrodes ex vivo as well as in a patient with a liver metastasis. Methods. A commercially available expandable RFA probe was used to create a 3‐cm ablation in a piece of bovine liver. The ablation probe was used in situ to induce tissue deformation for elastography before and after ablation. Ultrasonic radio frequency data were processed to generate elasticity strain images. The appearance of the ablation zone was compared with magnetic resonance imaging and a gross section specimen. One patient with malignant metastatic disease to the liver and a clinical indication for RFA was investigated for the feasibility of percutaneous elastography of RFA using the same technique. Sonographic strain images were compared with the appearance of the nonenhancing ablation zone on contrast‐enhanced computed tomography. Results. Ex vivo, the ablation zone on ultrasound‐based elastography was represented by an area of increased stiffness and was well demarcated from the nonablated surrounding tissue. The size and shape of the ablated zone on the strain image correlated well with the gross specimen and the magnetic resonance imaging appearance. Strain images obtained from the patient showed results similar to those of the ex vivo experiment and correlated well with the nonenhancing area of ablation on contrast‐enhanced computed tomography. Conclusions. Ultrasound‐based elastography may be a promising tool for displaying the ablation zone created by expandable RFA probes.

Hepatocellular carcinoma in the noncirrhotic liver.

OBJECTIVE Hepatocellular carcinomas (HCCs) that arise in noncirrhotic livers have several histologic and biochemical features that distinguish them from HCCs occurring in the setting of cirrhosis. Because the presentation, management, and prognosis of these entities are distinct, the accurate preoperative characterization of these lesions is of great clinical significance. We review the pathogenesis, imaging appearance, and clinical implications of noncirrhotic HCCs as they pertain to the clinical radiologist. CONCLUSION HCCs that develop in noncirrhotic patients have distinct etiologic, cytogenetic, histopathologic, and clinical features. Despite a larger tumor burden at the time of HCC diagnosis, noncirrhotic patients with HCC have better overall survival and disease-free survival than cirrhotic patients with HCC. Knowledge of the precise clinical and imaging features of this entity and of other diagnostic considerations for the noncirrhotic liver is essential for improved patient care.

Ferumoxytol in clinical practice: Implications for MRI

Ferumoxytol is an iron‐containing parenteral treatment for iron deficiency anemia that was recently approved by the Food and Drug Administration. The iron is in the form of a superparamagnetic iron oxide that causes T1, T2, and T2* shortening on magnetic resonance imaging (MRI). Furthermore, the drug has a long intravascular half‐life of 14–15 hours; a standard dose can affect MRI for days to months. We describe a case in which a patient underwent contrast‐enhanced MRI of the liver 2 days after receiving a dose of ferumoxytol, which was unknown to the radiology team. The blood pool and soft tissues were hyperintense on T1‐weighted images, concealing enhancement from the gadolinium‐based contrast agent that was administered during the exam and rendering the exam nondiagnostic. Radiologists must be aware of this potential effect in screening patients for MRI and interpreting exams. J. Magn. Reson. Imaging 2013;37:1476–1479.

Liver transplantation: vascular complications.

Transplantation has become the method of choice for treatment of patients with irreversible severe liver dysfunction. Vascular thrombosis or stenosis, biliary obstruction, hemorrhage, posttransplantation neoplasm, and rejection are some of the most common potential complications. Most complications cause significant morbidity and mortality after liver transplantation. The appearance of vascular complications in posttransplantation patients is illustrated in this article.

Cysts of the Lower Male Genitourinary Tract: Embryologic and Anatomic Considerations and Differential Diagnosis

Cysts of the lower male genitourinary tract are uncommon and usually benign. These cysts have different anatomic origins and may be associated with a variety of genitourinary abnormalities and symptoms. Various complications may be associated with these cysts, such as urinary tract infection, pain, postvoiding incontinence, recurrent epididymitis, prostatitis, and hematospermia, and they may cause infertility. Understanding the embryologic development and normal anatomy of the lower male genitourinary tract can be helpful in evaluating these cysts and in tailoring an approach for developing a differential diagnosis. There are two main groups of cysts of the lower male genitourinary tract: intraprostatic cysts and extraprostatic cysts. Intraprostatic cysts can be further classified into median cysts (prostatic utricle cysts, müllerian duct cysts), paramedian cysts (ejaculatory duct cysts), and lateral cysts (prostatic retention cysts, cystic degeneration of benign prostatic hypertrophy, cysts associated with tumors, prostatic abscess). Extraprostatic cysts include cysts of the seminal vesicle, vas deferens, and Cowper duct. A variety of pathologic conditions can mimic these types of cysts, including ureterocele, defect resulting from transurethral resection of the prostate gland, bladder diverticulum, and hydroureter and ectopic insertion of ureter. Accurate diagnosis depends mainly on the anatomic location of the cyst. Magnetic resonance imaging and transrectal ultrasonography (US) are excellent for detecting and characterizing the nature and exact anatomic origin of these cysts. In addition, transrectal US can play an important therapeutic role in the management of cyst drainage and aspiration, as in cases of prostatic abscess.