David K. Tso

Scanner and kVp dependence of measured CT numbers in the ACR CT phantom

Quality control testing of CT scanners in our region includes a measurement of CT numbers in the American College of Radiology (ACR) CT phantom using a standardized protocol. CT number values are clinically relevant in determining the composition of various tissues in the body. Accuracy is important in the characterization of tumors, assessment of coronary calcium, and identification of urinary stone composition. Effective quality control requires that tolerance ranges of CT number values be defined: a measured value outside the range indicates the need for further investigation and possible recalibration of the scanner. This paper presents the results of CT number measurements on 36 scanners (25 GE, 10 Siemens and 1 Toshiba) at each available kVp. Among the five materials (solid water, air, polyethylene, acrylic, bone‐equivalent) the measured CT numbers exhibit manufacturer and kVp dependence, which should be taken into account when defining tolerances. With this scan protocol, air and solid water values are significantly higher on GE scanners than on Siemens scanners (p‐value<0.01 at each kVp). The CT numbers of polyethylene and acrylic increase with kVp, while the bone‐equivalent CT number decreases. These results are used to define manufacturer‐ and kVp‐specific tolerance ranges for the CT numbers of each material in this phantom, which will be used in our quality control program. PACS numbers: 87.57.qp, 87.57.C‐

Real-World Estimated Effective Radiation Doses From Commonly Used Cardiac Testing and Procedural Modalities

BACKGROUND The volume of cardiac diagnostic tests that are performed has increased significantly in recent years. The benefits of these tests should be weighed against the risks, including exposure to ionizing radiation. We sought to determine the effective radiation doses associated with common cardiac imaging studies performed at a provincial referral heart centre in Vancouver, Canada, between January 1, 2009 and December 31, 2009. METHODS Effective radiation dose was calculated for all patients who underwent clinically indicated cardiac computed tomography angiography (CCTA), myocardial perfusion imaging (MPI), and diagnostic catheter coronary angiography (CCA) in 2009. The dose from CCTA and CCA studies was estimated from dose-length product and dose area product values, respectively. A conversion factor of 0.014 mSv/(mGy × cm) was used for CCTA and MPI CT attenuation correction. The conversion factor for CCA was 0.22 mSv/(Gy × cm(2)). The effective radiation dose for MPI was calculated using: E = (E/A) × A(o) where E = effective dose, E/A is an effective dose coefficient, and A(o) is the radiotracer activity. RESULTS There were 673 CCTA studies and 2306 MPI studies performed with average effective doses of 3.7 mSv and 16.8 mSv, respectively. There were 2628 diagnostic CCA studies performed with an average effective dose of 11.4 mSv. CONCLUSIONS There was a wide range of effective radiation doses between imaging modalities. These tests provide different clinical information and the appropriate test must be chosen with radiation dose in mind. The implementation of dose reduction strategies has the potential to significantly reduce these doses.

Imaging of Blunt Vascular Neck Injuries: A Review of Screening and Imaging Modalities

OBJECTIVE We will review the epidemiology of blunt cerebrovascular injuries (BCVIs) and the rationale for screening. Current imaging modalities used to screen for BCVIs will be discussed with an emphasis on CT angiography. CONCLUSION Screening for BCVIs can decrease rates of postinjury complications, such as stroke. The use of standardized screening criteria and the appropriate imaging modalities can allow early detection of BCVIs and effective intervention.

Extrahepatic Metastases of Hepatocellular Carcinoma: A Spectrum of Imaging Findings

Hepatocellular carcinoma (HCC) is the most common primary tumour of the liver, responsible for significant morbidity and mortality worldwide. In the Western world, it primarily affects patients with cirrhosis, secondary to hepatitis C virus and alcoholism. In the rest of the world, HCC is closely associated with hepatitis B virus infections. Radiologists play a key role in accurately staging HCC, which has important implications for treatment planning. This pictorial review aims to describe the routes of HCC spread and the most frequent sites of metastases, to recognize extrahepatic HCC findings on computed tomography and magnetic resonance imaging, and to understand the implications of HCC staging on treatment planning.

Imaging of Blunt Vascular Neck Injuries: A Clinical Perspective

OBJECTIVE We will review the common injuries and anatomic distributions of blunt cerebrovascular injuries (BCVIs) of the neck, explain the grading criteria, and discuss the corresponding management. Artifacts associated with BCVI on CT will also be examined. CONCLUSION Identifying common injury patterns and anatomic distributions associated with BCVI can help decide the grade and management earlier and reduce the risk for potential complications. Recognizing the common artifacts associated with BCVI helps the reader successfully recognize a true BCVI.

Reducing Blood-borne Exposure in Interventional Radiology: What the IR Should Know

Interventional radiologists are at risk of exposure to blood-borne pathogens in their day-to-day practice. Percutaneous exposure from unsafe sharps handling, mucocutaneous exposure from body fluid splashes, and glove perforation from excessive wear can expose the radiologist to potentially infectious material. The increasing prevalence of blood-borne pathogens, including hepatitis B and C, and human immunodeficiency virus, puts nurses, residents, fellows, and interventional radiologists at risk for occupational exposure. This review outlines suggestions to establish a culture of safety in the interventional suite.

Necrotizing fasciitis of the lower extremity: imaging pearls and pitfalls

OBJECTIVE The purpose of this article is to review the imaging findings of necrotizing fasciitis as seen on radiograph, ultrasound, CT, and MRI, and to recognize the early findings in this potentially fatal disease. CONCLUSION Although classically a clinical diagnosis, imaging is a powerful adjunct to facilitate early diagnosis in equivocal cases. Compared to plain radiography, ultrasound, CT and MR provide higher sensitivity and specificity for the diagnosis of necrotizing fasciitis. Cross-sectional imaging findings include asymmetric thickening of fascia, soft tissue air, blurring of fascial planes, inflammatory fat stranding, reactive lymphadenopathy, and nonenhancement of muscular fascia.

Development of an Undergraduate Radiology Curriculum: Ten-Year Experience From the University of British Columbia

Exposing medical students to the specialty of radiology is essential for recruiting excellent residents and cultivating an early understanding of the value of radiology in clinical practice. Several studies have demonstrated that medical student engagement at the undergraduate leveldthrough teaching, research, and mentorshipdplays an important role in determining students’ choice of residency [1e4]. However, undergraduate medical curriculum development teams across the country often do not include a radiologist. This results in heterogeneous teaching that frustrates students and dampens their enthusiasm for our specialty. The need for a unified undergraduate radiology curriculum was recognized at the University of British Columbia (UBC) over a decade ago. At that time, we conducted a national survey to identify the status of undergraduate radiology teaching in Canada. This survey identified a general lack of a unified syllabus, which resulted in redundant content, gaps in knowledge, and lack of continuity in medical school radiology curricula [5]. We were fortunate that the UBC medical school was undergoing curriculum renewal at that time and we were able to negotiate for lecture and laboratory time to try to address some of these deficits at our institution. Over the last 10 years, the radiology undergraduate curriculum has become an integral aspect of the UBC