Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Stephan W. Anderson is active.

Publication


Featured researches published by Stephan W. Anderson.


JAMA | 2012

Effect of testosterone supplementation with and without a dual 5α-reductase inhibitor on fat-free mass in men with suppressed testosterone production: a randomized controlled trial.

Shalender Bhasin; Thomas G. Travison; Thomas W. Storer; Kishore M. Lakshman; Manas Kaushik; Norman A. Mazer; Ahn Hoa Ngyuen; Maithili N. Davda; Hernan Jara; Adam Aakil; Stephan W. Anderson; Philip E. Knapp; Samson Hanka; Nurahmed Mohammed; Pierre Daou; Renee Miciek; Jagadish Ulloor; Anqi Zhang; Brad Brooks; Katie Orwoll; Leife Hede-Brierley; Richard Eder; Ayan Elmi; Geeta Bhasin; Lauren Collins; Ravinder J. Singh; Shehzad Basaria

CONTEXT Steroid 5α-reductase inhibitors are used to treat benign prostatic hyperplasia and androgenic alopecia, but the role of 5α-dihydrotestosterone (DHT) in mediating testosterones effects on muscle, sexual function, erythropoiesis, and other androgen-dependent processes remains poorly understood. OBJECTIVE To determine whether testosterones effects on muscle mass, strength, sexual function, hematocrit level, prostate volume, sebum production, and lipid levels are attenuated when its conversion to DHT is blocked by dutasteride (an inhibitor of 5α-reductase type 1 and 2). DESIGN, SETTING, AND PATIENTS The 5α-Reductase Trial was a randomized controlled trial of healthy men aged 18 to 50 years comparing placebo plus testosterone enthanate with dutasteride plus testosterone enanthate from May 2005 through June 2010. INTERVENTIONS Eight treatment groups received 50, 125, 300, or 600 mg/wk of testosterone enanthate for 20 weeks plus placebo (4 groups) or 2.5 mg/d of dutasteride (4 groups). MAIN OUTCOME MEASURES The primary outcome was change in fat-free mass; secondary outcomes: changes in fat mass, muscle strength, sexual function, prostate volume, sebum production, and hematocrit and lipid levels. RESULTS A total of 139 men were randomized; 102 completed the 20-week intervention. Men assigned to dutasteride were similar at baseline to those assigned to placebo. The mean fat-free mass gained by the dutasteride groups was 0.6 kg (95% CI, -0.1 to 1.2 kg) when receiving 50 mg/wk of testosterone enanthate, 2.6 kg (95% CI, 0.9 to 4.3 kg) for 125 mg/wk, 5.8 kg (95% CI, 4.8 to 6.9 kg) for 300 mg/wk, and 7.1 kg (95% CI, 6.0 to 8.2 kg) for 600 mg/wk. The mean fat-free mass gained by the placebo groups was 0.8 kg (95% CI, -0.1 to 1.7 kg) when receiving 50 mg/wk of testosterone enanthate, 3.5 kg (95% CI, 2.1 to 4.8 kg) for 125 mg/wk, 5.7 kg (95% CI, 4.8 to 6.5 kg) for 300 mg/wk, and 8.1 kg (95% CI, 6.7 to 9.5 kg) for 600 mg/wk. The dose-adjusted differences between the dutasteride and placebo groups for fat-free mass were not significant (P = .18). Changes in fat mass, muscle strength, sexual function, prostate volume, sebum production, and hematocrit and lipid levels did not differ between groups. CONCLUSION Changes in fat-free mass in response to graded testosterone doses did not differ in men in whom DHT was suppressed by dutasteride from those treated with placebo, indicating that conversion of testosterone to DHT is not essential for mediating its anabolic effects on muscle. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00493987.


American Journal of Roentgenology | 2009

Abdominal 64-MDCT for suspected appendicitis: the use of oral and IV contrast material versus IV contrast material only

Stephan W. Anderson; Jorge A. Soto; Brian C. Lucey; Al Ozonoff; Jacqueline D. Jordan; Jirair Ratevosian; Andrew Ulrich; Niels K. Rathlev; Patricia M. Mitchell; Casey M. Rebholz; James A. Feldman; James T. Rhea

OBJECTIVE The objective of our study was to compare the diagnostic accuracy of IV contrast-enhanced 64-MDCT with and without the use of oral contrast material in diagnosing appendicitis in patients with abdominal pain. MATERIALS AND METHODS We conducted a randomized trial of a convenience sample of adult patients presenting to an urban academic emergency department with acute nontraumatic abdominal pain and clinical suspicion of appendicitis, diverticulitis, or small-bowel obstruction. Patients were enrolled between 8 am and 11 pm when research assistants were present. Consenting subjects were randomized into one of two groups: Group 1 subjects underwent 64-MDCT performed with oral and IV contrast media and group 2 subjects underwent 64-MDCT performed solely with IV contrast material. Three expert radiologists independently reviewed the CT examinations, evaluating for the presence of appendicitis. Each radiologist interpreted 202 examinations, ensuring that each examination was interpreted by two radiologists. Individual reader performance and a combined interpretation performance of the two readers assigned to each case were calculated. In cases of disagreement, the third reader was asked to deliver a tiebreaker interpretation to be used to calculate the combined reader performance. Final outcome was based on operative, clinical, and follow-up data. We compared radiologic diagnoses with clinical outcomes to calculate the diagnostic accuracy of CT in both groups. RESULTS Of the 303 patients enrolled, 151 patients (50%) were randomized to group 1 and the remaining 152 (50%) were randomized to group 2. The combined reader performance for the diagnosis of appendicitis in group 1 was a sensitivity of 100% (95% CI, 76.8-100%) and specificity of 97.1% (95% CI, 92.7-99.2%). The performance in group 2 was a sensitivity of 100% (73.5-100%) and specificity of 97.1% (92.9-99.2%). CONCLUSION Patients presenting with nontraumatic abdominal pain imaged using 64-MDCT with isotropic reformations had similar characteristics for the diagnosis of appendicitis when IV contrast material alone was used and when oral and IV contrast media were used.


Radiographics | 2009

Strategies for Establishing a Comprehensive Quality and Performance Improvement Program in a Radiology Department

Jonathan B. Kruskal; Stephan W. Anderson; Chun S. Yam; Jacob Sosna

To improve the safety and quality of the care that radiologists provide, and to allow radiologists and radiology personnel to remain competitive in an increasingly complex environment, it is essential that all imaging departments establish and maintain managed, comprehensive, and effective performance improvement programs. Although the structure and focus of these programs can vary, a number of common components exist, many of which are now widely mandated by organizations that regulate the field of radiology. Basic components include patient safety, process improvement, customer service, professional staff assessment, and education, each of which requires strategies for implementing continuous programs to monitor performance, analyzing and depicting data, implementing change, and meeting regulatory requirements. All of these components are part of a comprehensive quality management system in a large academic radiology department. For smaller departments or practices, the gradual introduction of one or more of these components is useful in ensuring the safety and quality of their services.


Emergency Radiology | 2007

Spontaneous hemoperitoneum: a bloody mess

Brian C. Lucey; Jose C. Varghese; Stephan W. Anderson; Jorge A. Soto

Spontaneous hemoperitoneum may be a life-threatening occurrence. It most frequently presents with acute abdominal pain. Computed tomography (CT) is the most commonly used modality in the initial work up of these patients, but sonography and magnetic resonance imaging (MRI) play a role in the diagnosis. The etiology is varied, yet may be broadly classified into gynecologic, hepatic, splenic, vascular, and coagulopathic causes. This review will describe the common imaging findings of spontaneous hemoperitoneum, as it presents through the emergency room, and will detail the underlying causes and significance of spontaneous hemoperitoneum.


Radiologic Clinics of North America | 2010

CT Angiography in Trauma

Jennifer W. Uyeda; Stephan W. Anderson; Osamu Sakai; Jorge A. Soto

Rapid assessment and diagnosis of traumatic arterial injuries are critical in the evaluation of acutely injured patients. CT angiograms (CTAs) have become common imaging methods in busy trauma centers. CTA has largely replaced digital subtraction angiography because of its speed, noninvasive nature, accuracy, and widespread availability. This article reviews the current use of multidetector CTA in trauma with attention to technique and protocol considerations, illustrates findings of many commonly encountered injuries, and discusses the clinical implications of vascular trauma throughout the body.


American Journal of Roentgenology | 2006

Accuracy of MDCT in the diagnosis of choledocholithiasis.

Stephan W. Anderson; Brian C. Lucey; Jose C. Varghese; Jorge A. Soto

OBJECTIVE Our purpose was to evaluate the diagnostic performance of contrast-enhanced and unenhanced MDCT, performed for various indications, in detecting choledocholithiasis. CONCLUSION Unenhanced and contrast-enhanced MDCT images, interpreted in PACS workstations with axial images, are moderately sensitive and specific for showing choledocholithiasis.


Radiology | 2008

Detection of biliary duct narrowing and choledocholithiasis: accuracy of portal venous phase multidetector CT.

Stephan W. Anderson; Eunjin Rho; Jorge A. Soto

PURPOSE To retrospectively evaluate the sensitivity and specificity of 64-detector computed tomography (CT) in the portal venous phase by using transverse images and both multiplanar and minimum intensity reformations for the detection of biliary duct narrowing and choledocholithiasis, with magnetic resonance cholangiopancreatography (MRCP) or endoscopic retrograde cholangiopancreatography (ERCP) as the reference standard. MATERIALS AND METHODS Approval from institutional review board was obtained for this HIPAA-compliant retrospective study; informed consent was waived. The study included all patients (42 men, 52 women; mean age, 61 years) who underwent abdominal 64-detector CT within 2 months of MRCP and/or ERCP. All patients underwent portal venous phase intravenous contrast material-enhanced abdominal CT. Sixty-one patients underwent MRCP and 54 patients underwent ERCP (21 patients underwent both). Two radiologists, blinded to the reference standard, independently evaluated the CT images, including multiplanar and minimum intensity reformations, for biliary duct narrowing and choledocholithiasis. Standard of reference examinations were used to calculate sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). RESULTS Twenty-three (24%) of 94 patients had a biliary duct narrowing at reference examinations. For detecting biliary duct narrowing, observer 1 had a sensitivity of 78.2%, specificity of 100%, PPV of 100%, and NPV of 93.4% and observer 2 had a sensitivity of 69.6%, specificity of 100%, PPV of 100%, and NPV of 91.0%. In 18 (19%) of 94 patients, choledocholithiasis was detected at reference examinations. For detecting choledocholithiasis, observer 1 had a sensitivity of 77.8%, specificity of 96.1%, PPV of 82.4%, and NPV of 94.8% and observer 2 had a sensitivity of 72.2%, specificity of 96.1%, PPV of 81.2%, and NPV of 93.6%. CONCLUSION Portal venous phase multidetector CT images are highly specific and moderately sensitive for the detection of biliary duct narrowing and choledocholithiasis.


Radiographics | 2009

Benign Hepatic Tumors and Iatrogenic Pseudotumors

Stephan W. Anderson; Jonathan B. Kruskal; Robert A. Kane

Myriad benign tumors may be found in the liver; they can be classified according to their cell of origin into tumors of hepatocellular, cholangiocellular, or mesenchymal origin. Common benign hepatic tumors may pose a diagnostic dilemma when they manifest with atypical imaging features. Less frequently encountered benign hepatic tumors such as inflammatory pseudotumor or biliary cystadenoma demonstrate less specific imaging features; however, awareness of their findings is useful in narrowing differential diagnostic considerations. In addition, certain iatrogenically induced abnormalities of the liver may be confused with more ominous findings such as infection or neoplasia. However, knowledge of their common imaging appearances, in addition to the clinical history, is critical in correctly diagnosing and characterizing iatrogenic abnormalities of the liver. Familiarity with both expected and unexpected imaging appearances of common benign hepatic tumors, less commonly encountered benign hepatic tumors, and iatrogenic abnormalities potentially masquerading as hepatic tumors allows the radiologist to achieve an informed differential diagnosis.


American Journal of Roentgenology | 2008

MDCT Evaluation of Blunt Abdominal Trauma: Clinical Significance of Free Intraperitoneal Fluid in Males with Absence of Identifiable Injury

T. Eric Drasin; Stephan W. Anderson; Amy Asandra; James T. Rhea; Jorge A. Soto

OBJECTIVE The purpose of our study was to determine the clinical significance of the isolated finding of free intraperitoneal fluid on 64-MDCT in male patients who have undergone blunt trauma. MATERIALS AND METHODS A retrospective study was performed of 669 consecutive male patients, ranging in age from 15 to 85 years, who underwent CT evaluation of the abdomen and pelvis at our level 1 trauma center over a 17-month period. Two radiologists evaluated the images for the presence of free intraperitoneal fluid and for an underlying cause. For patients with free intraperitoneal fluid, the mean attenuation and the size of the largest pocket of fluid on both portal venous and delayed phase images were measured for both those with and those without injury. For the patients who had free intraperitoneal fluid as an isolated finding, the electronic chart was reviewed to determine the clinical outcome, specifically whether these patients were observed, had short-interval follow-up imaging, or underwent exploratory laparotomy. RESULTS Forty-eight of the 669 patients (7.2%) had free intraperitoneal fluid. Twenty-nine (4.3%) of these patients had an identifiable solid organ, bowel, bladder, or pelvic injury to explain the free fluid. In the remaining 19 (2.8%) patients, free fluid was an isolated finding. The size of the largest collection of fluid was smaller for patients without identifiable injury on portal venous phase (1,236 vs 348 mm(2)) and delayed phase (1,325 vs 298 mm(2)) images (p = 0.0015 and p < 0.0001, respectively). Fluid in patients without identifiable injury was also shown to be less dense. A statistically significant difference between the mean attenuation coefficients of the fluid in the patients with and without injury was also found on both the portal venous phase (45.1 vs 13.1 HU, p < 0.0001) and delayed phase (45.6 vs 20.8 HU, p < 0.0001) images. All 19 patients without identifiable injury were admitted for observation and discharged without surgical intervention. CONCLUSION With 64 MDCT, the isolated finding of free intraperitoneal fluid in male patients who have undergone blunt trauma is seen in approximately 3% of patients. The size and mean attenuation coefficient measurements may add useful information regarding the clinical management of these patients, suggesting that small amounts of low-attenuation free fluid, in the absence of identifiable injury, may have no significant clinical implications.


Radiographics | 2010

Ileal Pouch–Anal Anastomosis Surgery: Imaging and Intervention for Post-operative Complications

Jennifer C. Broder; Jaroslaw N. Tkacz; Stephan W. Anderson; Jorge A. Soto; Avneesh Gupta

Ileal pouch-anal anastomosis (IPAA) surgery preserves fecal continence for improved quality of life in patients who require proctocolectomy for treatment of severe bowel diseases such as inflammatory disease and familial adenomatous polyposis. In IPAA surgery, an ileal reservoir, or pouch, is created and anastomosed to the anal canal. Awareness of the surgical technique and the postoperative anatomy of the IPAA is important to identify complications at computed tomography (CT), magnetic resonance (MR) imaging, and fluoroscopy. Complications include anastomotic leak, abscess, pouchitis, venous thrombus, pouch fistula, and stricture. Leaks from the blind end of the pouch and the pouch-anal anastomosis often result in pelvic abscesses, which may require ultrasonography- or CT-guided drainage; judicious catheter management can help improve clinical outcomes and avoid excessive imaging. Pouchitis may be identified by the presence of a thickened enhancing pouch wall and associated inflammatory changes and lymphadenopathy. The venous system must be scrutinized for thrombi secondary to surgical manipulation and sepsis. Fistulas are likely because of the presence of chronic inflammation or infection and may be seen at MR imaging, CT, or fluoroscopy. Strictures appear as areas of focal luminal narrowing with proximal dilatation, which can lead to obstruction. To avoid repeated exposure to radiation, MR imaging may be performed in patients who must undergo frequent imaging.

Collaboration


Dive into the Stephan W. Anderson's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar

Xin Zhang

Hong Kong University of Science and Technology

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Jennifer W. Uyeda

Brigham and Women's Hospital

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Al Ozonoff

Boston Children's Hospital

View shared research outputs
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge