Radiographics current issue

[Online Only] Abdominal Applications of 3.0-T MR Imaging: Comparative Review versus a 1.5-T System

2008-07-17

With the development of dedicated receiver coils and increased gradient performance, 3.0-T magnetic resonance (MR) systems are gaining wider acceptance in clinical practice. The expected twofold increase in signal-to-noise ratio (SNR) compared with that of 1.5-T MR systems may help improve spatial resolution or increase temporal resolution when used with parallel acquisition techniques. Several issues must be considered when applying 3.0-T MR in the abdomen, including the alteration of the radiofrequency field and relaxation time, increase in energy deposition and susceptibility effects, and problems associated with motion artifacts. For the evaluation of liver lesions, higher SNR and greater resolution achieved with the 3.0-T system could translate into better detection of malignant lesions on T2-weighted images obtained with adjusted imaging parameters. For the evaluation of pancreatic and biliary diseases, high-resolution T2-weighted imaging using single-shot turbo spin-echo sequences is useful; improvement in SNR was noticeable on two-dimensional MR cholangiopancreatographic images. For the preoperative imaging of rectal cancer, a single-shot sequence is useful for dramatically decreasing imaging time while maintaining image quality. Substantial modification of examination protocols, with optimized imaging parameters and sequence designs along with ongoing development of hardware, could contribute to an increased role of the 3.0-T system for abdominal MR examinations.

[Editorial] Editor's Page: RadioGraphics Readership Survey: A Time for Reflection and an Opportunity for Change

Olmsted, W. W. — 2008-08-13

[Quality Initiatives] Quality Initiatives * Respiratory Instructions for CT Examinations of the Lungs: A Hands-on Guide

Bankier, A. A., O'Donnell, C. R., Boiselle, P. M. — 2008-07-17

In computed tomographic (CT) examinations of the lung, accurate visualization of the natural contrast between the low attenuation of air and the relatively higher attenuation of vessels, airways, and interstitial structures requires cooperative and coordinated respiratory maneuvers by the patient. Inadequate respiratory maneuvers can influence differences in lung attenuation and lead to misinterpretation by (a) increasing attenuation to simulate disease in normal patients, (b) decreasing attenuation to simulate normal contrast in patients with disease, or (c) creating motion artifacts. For respiratory maneuvers to be effective, patients have to be instructed before the examination and coached during it. However, comprehensive descriptions of such instructions and coaching are lacking in the radiology literature. Therefore, respiratory instructions specifically for use in thoracic CT examinations have been devised. Along with patient coaching, use of these instructions can improve image quality. With this hands-on guide, both radiologists and technologists can optimize the respiratory instructions given to their patients and thereby improve the quality of thoracic CT examinations.

[Special Communications] Congratulations to the 2007 Outstanding Educator: Robert Novelline, MD

Osborn, A. G., Jost, R. G. — 2008-07-17

[Informatics] Informatics in Radiology: IHE Teaching File and Clinical Trial Export Integration Profile: Functional Examples

2008-07-17

The digital revolution in radiology introduced the need for electronic export of medical images. However, the current export process is complicated and time consuming. In response to this continued difficulty, the Integrating the Healthcare Enterprise (IHE) initiative published the Teaching File and Clinical Trial Export (TCE) integration profile. The IHE TCE profile describes a method for using existing standards to simplify the export of key medical images for education, research, and publication. This article reviews the authors’ experience in implementing the TCE profile in the following three processes: (a) the retrieval of images for a typical teaching file application within a TCE-compliant picture archiving and communication system (PACS); (b) the export of images, independent of TCE compliance of the PACS, to a typical teaching file application; and (c) the TCE-compliant transfer of images for publication. These examples demonstrate methods with which the TCE profile can be implemented to ease the burden of collecting key medical images from the PACS.

[Illuminations] Using Three- dimensional CT to Create Fine Art

Fung, K.-h. — 2008-07-17

[RSNA Education Exhibits] Role of Static and Dynamic MR Imaging in Surgical Pelvic Floor Dysfunction

Boyadzhyan, L., Raman, S. S., Raz, S. — 2008-07-17

Pelvic floor dysfunction (PFD) is a hidden women’s health epidemic in the United States, with over 10% of women having a lifetime risk for undergoing a surgical repair for this problem. Given the paucity of understanding of PFD pathophysiology and the high rate of recurrence and repeat surgery, imaging plays a major role in its clinical management, especially for the preoperative assessment of patients with multicompartment defects and failed surgical repairs. The recent development of fast magnetic resonance (MR) imaging sequences allows noninvasive, radiation-free, rapid, high-resolution evaluation of the entire pelvis in one examination. The H line, M line, organ prolapse (HMO) classification system, which is applied to dynamic MR images, allows consistent standardization and grading of various forms of PFD. In addition, the HMO system clearly defines and differentiates between the two main components of PFD: pelvic floor relaxation and pelvic organ prolapse. In addition to serving as an objective diagnostic tool in patients with surgical PFD, MR imaging has tremendous potential to be used as a research tool in trying to understand the pathophysiology of these complex disorders.

[RSNA Education Exhibits] Imaging Findings of Complications and Unusual Manifestations of Ovarian Teratomas

Park, S. B., Kim, J. K., Kim, K.-R., Cho, K.-S. — 2008-07-17

Ovarian teratomas can be associated with various complications and demonstrate a wide spectrum of clinical and imaging features. The complications include torsion (16% of ovarian teratomas), rupture (1%–4%), malignant transformation (1%–2%), infection (1%), and autoimmune hemolytic anemia (<1%). These complications require different therapeutic strategies; therefore, timely and accurate diagnosis of these complications is important for optimal patient treatment. In cases of complicated ovarian teratomas, the clinical manifestations provide only limited information and often overlap with those of other diseases. Furthermore, ovarian teratomas may have unusual clinical and imaging manifestations, thereby leading to misdiagnosis. These unusual manifestations include immature teratomas, monodermal teratomas (struma ovarii), combination tumors and collision tumors containing teratomas, and mature cystic teratomas without demonstrable fat or with pure fatty components. To provide adequate treatment and prevent misdiagnosis, it is necessary to be familiar with the imaging findings of both the complications and the unusual manifestations of ovarian teratomas.

[RSNA Education Exhibits] MR Imaging of Renal Masses: Correlation with Findings at Surgery and Pathologic Analysis

2008-07-17

Magnetic resonance (MR) imaging is useful in the characterization of renal masses. The MR imaging manifestations and pathologic diagnoses of 82 renal masses were reviewed and correlated. The MR imaging appearance of clear cell type renal cell carcinoma varies depending on the presence of cystic components, hemorrhage, and necrosis. Papillary renal cell carcinomas appear as well-encapsulated masses with homogeneous low signal intensity on T2-weighted images and homogeneous low-level enhancement after the intravenous administration of contrast material, or as cystic hemorrhagic masses with peripheral enhancing papillary projections. Transitional cell carcinoma may be seen as an irregular, enhancing filling defect in the pelvicaliceal system or ureter. Lymphomatous masses are usually hypointense relative to the renal cortex on T2-weighted images and enhance minimally on delayed gadolinium-enhanced images. Bulk fat is a distinguishing feature of angiomyolipoma. Oncocytoma has a variable and nonspecific appearance at MR imaging. MR imaging findings may allow the characterization of various renal masses and can provide valuable information for their clinical management.

[RSNA Education Exhibits] Neoplastic and Non-neoplastic Proliferative Disorders of the Perirenal Space: Cross-sectional Imaging Findings

2008-07-17

The perirenal space, located between the anterior and the posterior renal fasciae, is shaped like an inverted cone with an apex that extends into the iliac fossa. Perirenal tumors and pseudotumors primarily originate either from the kidney or as part of a systemic disease process and have characteristic histopathologic features and biologic behavior. The lesions may be classified on the basis of their distribution and imaging features as solitary soft-tissue masses (renal cell carcinoma, lymphangioma, hemangioma, and leiomyoma), rindlike soft-tissue lesions (lymphoma, retroperitoneal fibrosis, and Erdheim-Chester disease), masses containing macroscopic fat (angiomyolipoma, liposarcoma, myelolipoma, and extramedullary hematopoiesis), and multifocal soft-tissue masses (metastases, plasma cell tumors). Because of overlap in imaging findings among these diverse perirenal lesions, a definitive diagnosis in most cases can be established only at histopathologic analysis. However, an imaging pattern–based approach may facilitate the diagnosis and optimal management of perirenal tumors and pseudotumors.

[RSNA Education Exhibits] Diagnostic Imaging of Solitary Tumors of the Spine: What to Do and Say

2008-07-17

Metastatic disease, myeloma, and lymphoma are the most common malignant spinal tumors. Hemangioma is the most common benign tumor of the spine. Other primary osseous lesions of the spine are more unusual but may exhibit characteristic imaging features that can help the radiologist develop a differential diagnosis. Radiologic evaluation of a patient who presents with osseous vertebral lesions often includes radiography, computed tomography (CT), and magnetic resonance (MR) imaging. Because of the complex anatomy of the vertebrae, CT is more useful than conventional radiography for evaluating lesion location and analyzing bone destruction and condensation. The diagnosis of spinal tumors is based on patient age, topographic features of the tumor, and lesion pattern as seen at CT and MR imaging. A systematic approach is useful for recognizing tumors of the spine with characteristic features such as bone island, osteoid osteoma, osteochondroma, chondrosarcoma, vertebral angioma, and aneurysmal bone cyst. In the remaining cases, the differential diagnosis may include other primary spinal tumors, vertebral metastases and major nontumoral lesions simulating a vertebral tumor, Paget disease, spondylitis, echinococcal infection, and aseptic osteitis. In many cases, vertebral biopsy is warranted to guide treatment.

[Illuminations] The Aging Radiologist: "You Are Old, Dr Williams"

Bachman, D. M. — 2008-07-17

[RSNA Education Exhibits] MR Imaging of Cartilage Repair in the Knee and Ankle

Choi, Y. S., Potter, H. G., Chun, T. J. — 2008-07-17

Because of the relative avascularity of articular cartilage, lesions that are caused by trauma or degeneration of the cartilage do not heal spontaneously and must be repaired surgically. The interventional procedures that have been developed for the repair of such lesions include abrasion, microfracture, autologous osteochondral transplantation, allograft transplantation, and autologous chondrocyte implantation. An accurate imaging assessment of the repair tissue is necessary in order to objectively evaluate the postoperative outcome. Magnetic resonance (MR) imaging and arthroscopy provide complementary information and are especially useful for follow-up evaluation of cartilage repair in the knee and ankle. Standard MR imaging techniques may be used postoperatively to evaluate the success of implantation and the state of cartilage healing. Newer matrix assessment techniques, which include delayed gadolinium-enhanced MR imaging and mapping of T1 and T2 values, may provide useful supplemental information about the histologic and biochemical contents of reparative tissue. The normal postoperative appearance of the joints after cartilage repair varies according to the surgical technique used and the stage of healing. To identify potential complications, it is important to be familiar with the various repair procedures and the characteristic MR imaging features of the repair tissue at various postoperative intervals.

[RSNA Education Exhibits] Fetal Skeletal Dysplasia: An Approach to Diagnosis with Illustrative Cases

Dighe, M., Fligner, C., Cheng, E., Warren, B., Dubinsky, T. — 2008-07-17

Skeletal dysplasias are a heterogeneous group of conditions associated with various abnormalities of the skeleton. These conditions are caused by widespread disturbance of bone growth, beginning during the early stages of fetal development and evolving throughout life. Despite recent advances in imaging, fetal skeletal dysplasias are difficult to diagnose in utero due to a number of factors, including the large number of skeletal dysplasias and their phenotypic variability with overlapping features, lack of precise molecular diagnosis for many disorders, lack of a systematic approach, the inability of ultrasonography (US) to provide an integrated view, and variability in the time at which findings manifest in some skeletal dysplasias. US of suspected skeletal dysplasia involves systematic imaging of the long bones, thorax, hands and feet, skull, spine, and pelvis. Assessment of the fetus with three-dimensional US has been shown to improve diagnostic accuracy, since additional phenotypic features not detectable at two-dimensional US may be identified. The radiologist plays a major role in making an accurate diagnosis; however, representatives of other disciplines, including clinicians, molecular biologists, and pathologists, can also provide important diagnostic information.

[RSNA Education Exhibits] Neuroimaging in Pediatric Epilepsy: A Multimodality Approach

Rastogi, S., Lee, C., Salamon, N. — 2008-07-17

Pediatric patients with intractable epilepsy represent a challenging clinical population. However, recent advances in neuroimaging with a multimodality imaging approach that combines fluorine 18 fluorodeoxyglucose positron emission tomography, magnetoencephalography, diffusion tensor imaging, and magnetic source imaging with conventional magnetic resonance imaging continue to improve diagnosis and treatment in affected patients. These advances are increasing the understanding of the underlying disease process and improving the ability to noninvasively detect epileptogenic foci that in the past went undetected and whose accurate localization is crucial for a good outcome following surgical resection.

[RSNA Education Exhibits] SPECT/CT Imaging: Clinical Utility of an Emerging Technology

2008-07-17

Single-photon emission computed tomography (SPECT) has been a mainstay of nuclear medicine practice for several decades. More recently, combining the functional imaging available with SPECT and the anatomic imaging of computed tomography (CT) has gained more acceptance and proved useful in many clinical situations. Most vendors now offer integrated SPECT/CT systems that can perform both functions on one gantry and provide fused functional and anatomic data in a single imaging session. In addition to allowing anatomic localization of nuclear imaging findings, SPECT/CT also enables accurate and rapid attenuation correction of SPECT studies. These attributes have proved useful in many cardiac, general nuclear medicine, oncologic, and neurologic applications in which the SPECT results alone were inconclusive. Optimal clinical use of this rapidly emerging imaging modality requires an understanding of the fundamental principles of SPECT/CT, including quality control issues as well as potential pitfalls and limitations. The long-term clinical and economic effects of this technology have yet to be established.

[RSNA Education Exhibits] Mimics of Cholangiocarcinoma: Spectrum of Disease

2008-07-17

Cholangiocarcinoma is the second most common primary malignant hepatobiliary neoplasm, accounting for approximately 15% of liver cancers. Diagnosis of cholangiocarcinoma is challenging and the prognosis is uniformly poor, with recurrence rates of 60%–90% after surgical resection. A wide spectrum of neoplastic and nonneoplastic conditions of the biliary tract may masquerade as cholangiocarcinoma, adding to the complexity of management in patients suspected to have cholangiocarcinoma. Mimics of cholangiocarcinoma constitute a heterogeneous group of entities that includes primary sclerosing cholangitis, recurrent pyogenic cholangitis, acquired immunodeficiency syndrome cholangiopathy, autoimmune pancreatitis, inflammatory pseudotumor, Mirizzi syndrome, xanthogranulomatous cholangitis, sarcoidosis, chemotherapy-induced sclerosis, hepatocellular carcinoma, metastases, melanoma, lymphoma, leukemia, and carcinoid tumors. These entities demonstrate characteristic histomorphology and variable clinicobiologic behaviors. The imaging findings of these disparate entities are protean and may be indistinguishable from those of cholangiocarcinoma. In most cases, a definitive diagnosis can be established only with histopathologic examination of a biopsy specimen.

[RSNA Education Exhibits] Neuroendocrine Tumors: Role of Interventional Radiology in Therapy

2008-07-17

The management of neuroendocrine tumors (NETs) is complex. Although NETs can affect a variety of organ systems, hepatic metastatic disease in particular lends itself to a wide range of interventional treatment options. Prior detailed radiologic assessment and careful patient selection are required. Curative surgery should always be considered but is rarely possible. Embolization, radionuclide therapy, or ablative techniques may then be undertaken. Transcatheter arterial embolization (TAE) may be used alone or in combination with transcatheter arterial chemoembolization (TACE). NET type and extent of hepatic involvement are factors that can help predict the success of either TAE or TACE. Embolization techniques can also be useful in patients with nonhepatic NETs. Radionuclide therapy is emerging as a valuable adjunct and is dependent on positive somatostatin receptor status. Therapeutic radiopeptides may be delivered arterially. Ablative techniques have been shown to play a role in the palliation of symptoms and principally involve radiofrequency ablation. Hepatic cryotherapy and percutaneous ethanol injection have also been used. A multidisciplinary approach to treatment and follow-up is important. Imaging should involve dual-phase multidetector computed tomography and contrast material–enhanced magnetic resonance imaging. The role of the interventional radiologist will continue to expand as imaging techniques become more refined.

[RSNA Education Exhibits] Steady-State MR Imaging Sequences: Physics, Classification, and Clinical Applications

Chavhan, G. B., Babyn, P. S., Jankharia, B. G., Cheng, H.-L. M., Shroff, M. M. — 2008-07-17

Steady-state sequences are a class of rapid magnetic resonance (MR) imaging techniques based on fast gradient-echo acquisitions in which both longitudinal magnetization (LM) and transverse magnetization (TM) are kept constant. Both LM and TM reach a nonzero steady state through the use of a repetition time that is shorter than the T2 relaxation time of tissue. When TM is maintained as multiple radiofrequency excitation pulses are applied, two types of signal are formed once steady state is reached: preexcitation signal (S–) from echo reformation; and postexcitation signal (S+), which consists of free induction decay. Depending on the signal sampled and used to form an image, steady-state sequences can be classified as (a) postexcitation refocused (only S+ is sampled), (b) preexcitation refocused (only S– is sampled), and (c) fully refocused (both S+ and S– are sampled) sequences. All tissues with a reasonably long T2 relaxation time will show additional signals due to various refocused echo paths. Steady-state sequences have revolutionized cardiac imaging and have become the standard for anatomic functional cardiac imaging and for the assessment of myocardial viability because of their good signal-to-noise ratio and contrast-to-noise ratio and increased speed of acquisition. They are also useful in abdominal and fetal imaging and hold promise for interventional MR imaging. Because steady-state sequences are now commonly used in MR imaging, radiologists will benefit from understanding the underlying physics, classification, and clinical applications of these sequences.

[RSNA Education Exhibits] Optimizing Cardiac MR Imaging: Practical Remedies for Artifacts

Saremi, F., Grizzard, J. D., Kim, R. J. — 2008-07-17

With ongoing technical advances in magnetic resonance (MR) imaging, the clinical demand for cardiac MR evaluations has been increasing. Cardiac MR imaging techniques have evolved from traditional spin-echo sequences to breath-hold spoiled gradient-echo and balanced steady-state free precession sequences. The most recently developed techniques allow evaluation of myocardial function, perfusion, and viability; coronary angiography; flow quantification; and standard morphologic assessments. However, even with the most sophisticated acquisition techniques, artifacts commonly occur at cardiac MR imaging. Knowledge of the origin, imaging appearance, and significance of these artifacts is essential to avoid misinterpreting them as true lesions. Some artifacts are caused by simple errors in positioning of the patient, coil, or electrocardiographic leads; radiofrequency interference from nearby electronic equipment; or metallic objects within the magnetic field. Others are directly related to a specific MR imaging sequence or technique. Accelerated imaging techniques such as parallel imaging, which are used to shorten acquisition and breath-hold times in cardiac evaluations, are particularly vulnerable to artifacts. If an artifact severely degrades image quality, the acquisition should be repeated with appropriate adjustments to decrease or eliminate the problem.

[Special Exhibits] Scenes from the Past: Nikola Tesla and the Discovery of X-rays

Hrabak, M., Padovan, R. S., Kralik, M., Ozretic, D., Potocki, K. — 2008-07-17

[AFIP Archives] From the Archives of the AFIP * Pediatric Orbit Tumors and Tumorlike Lesions: Osseous Lesions of the Orbit

Chung, E. M., Murphey, M. D., Specht, C. S., Cube, R., Smirniotopoulos, J. — 2008-07-17

Many extraocular masses involving the pediatric orbit have an osseous origin. The most common is the dermoid inclusion cyst; these cystic lesions may contain lipid and are most often found near the zygomaticofrontal suture, adjacent to an indolent-appearing erosion of bone. Some primary bone lesions may involve the orbit, producing a lytic or dense lesion with enlargement of the bone; these lesions include fibrous dysplasia, juvenile ossifying fibroma, and osteosarcoma. Fibrous dysplasia tends to produce a mass of ground-glass appearance with longitudinal osseous expansion, whereas juvenile ossifying fibroma is likely to produce a mixed lytic and sclerotic lesion and focal osseous enlargement. Osteosarcoma causes marked bone destruction and variable osteoid production. Langerhans cell histiocytosis, an idiopathic reticuloendothelial proliferative disorder, tends to involve the bones of the skull, especially the lateral orbital roof; it produces lytic destruction of bone with a sclerotic rim and a large intraorbital soft-tissue mass. Granulocytic sarcoma is a solid tumor that may occur in children with myelogenous leukemia. These tumors tend to arise in the subperiosteum of the lateral orbital wall, although they usually do not disrupt the bone. Finally, the orbit is a common site for bone metastases from neuroblastoma, which cause aggressive periosteal reaction in the orbital roof or lateral wall. The last three conditions are often bilateral. At imaging evaluation, osseous lesions may appear similar to each other and to nonosseous masses of the orbit. Knowledge of the pathologic features of these tumors and how these features are reflected in their imaging appearances may help radiologists differentiate them.

[AFIP Archives] Best Cases from the AFIP: Adamantinoma of the Tibia and Fibula with Cytogenetic Analysis

Camp, M. D., Tompkins, R. K., Spanier, S. S., Bridge, J. A., Bush, C. H. — 2008-07-17

[AFIP Archives] Best Cases from the AFIP: Multilocular Cystic Renal Tumor: Cystic Nephroma

Silver, I. M. F., Boag, A. H., Soboleski, D. A. — 2008-07-17

[AFIP Archives] Invited Commentary

Takahashi, N., Kawashima, A., Lewin, M., King, B. F., Cheville, J. C. — 2008-07-17