Showing papers in "Radiographics in 2009"

Principles, Techniques, and Applications of T2*-based MR Imaging and Its Special Applications

Abstract: T2* relaxation refers to decay of transverse magnetization caused by a combination of spin-spin relaxation and magnetic fi eld inhomogeneity. T2* relaxation is seen only with gradient-echo (GRE) imaging because transverse relaxation caused by magnetic fi eld inhomogeneities is eliminated by the 180° pulse at spin-echo imaging. T2* relaxation is one of the main determinants of image contrast with GRE sequences and forms the basis for many magnetic resonance (MR) applications, such as susceptibility-weighted (SW) imaging, perfusion MR imaging, and functional MR imaging. GRE sequences can be made predominantly T2* weighted by using a low fl ip angle, long echo time, and long repetition time. GRE sequences with T2*-based contrast are used to depict hemorrhage, calcifi cation, and iron deposition in various tissues and lesions. SW imaging uses phase information in addition to T2*-based contrast to exploit the magnetic susceptibility differences of the blood and of iron and calcifi cation in various tissues. Perfusion MR imaging exploits the signal intensity decrease that occurs with the passage of a high concentration of gadopentetate dimeglumine through the microvasculature. Change in oxygen saturation during specifi c tasks changes the local T2*, which leads to the blood oxygen level–dependent effect seen at functional MR imaging. The basics of T2* relaxation, T2*-weighted sequences, and their clinical applications are presented, followed by the principles, techniques, and clinical uses of four T2*-based applications, including SW imaging, perfusion MR imaging, functional MR imaging, and iron overload imaging.

Hepatobiliary-specific MR Contrast Agents: Role in Imaging the Liver and Biliary Tree

Abstract: Hepatobiliary-specific contrast agents are one of several classes of contrast agents available for magnetic resonance (MR) imaging of the liver. These agents are taken up by functioning hepatocytes and excreted in the bile, and their paramagnetic properties cause shortening of the longitudinal relaxation time (T1) of the liver and biliary tree. The three contrast agents that have been developed are mangafodipir trisodium (Mn-DPDP), gadobenate dimeglumine (Gd-BOPTA), and gadoxetic acid (Gd-EOB-DTPA). These three MR contrast agents vary in mode of administration and dose, mechanism of cellular uptake, degree of excretion through the biliary pathway, and imaging characteristics. In the liver, hepatobiliary-specific agents can be used to improve lesion detection, to characterize lesions as hepatocellular or nonhepatocellular, and to specifically characterize some hepatocellular lesions, notably focal nodular hyperplasia. Biliary excretion of these agents can be used to evaluate the anatomic structure and function of the biliary tree. In the future, hepatobiliary-specific contrast agents may have wider applications, such as grading of cirrhosis and quantification of liver function.

Varying appearances of cholangiocarcinoma: radiologic-pathologic correlation.

Abstract: Intrahepatic cholangiocarcinoma is the second most common primary hepatic tumor. Various risk factors have been reported for intrahepatic cholangiocarcinoma, and the radiologic and pathologic findings of this disease entity may differ depending on the underlying risk factors. Intrahepatic cholangiocarcinoma can be classified into three types on the basis of gross morphologic features: mass-forming (the most common), periductal infiltrating, and intraductal growth. At computed tomography (CT), mass-forming intrahepatic cholangiocarcinoma usually appears as a homogeneous low-attenuation mass with irregular peripheral enhancement and can be accompanied by capsular retraction, satellite nodules, and peripheral intrahepatic duct dilatation. Periductal infiltrating cholangiocarcinoma is characterized by growth along the dilated or narrowed bile duct without mass formation. At CT and magnetic resonance imaging, diffuse periductal thickening and increased enhancement can be seen with a dilated or irregularly narrowed intrahepatic duct. Intraductal cholangiocarcinoma may manifest with various imaging patterns, including diffuse and marked ductectasia either with or without a grossly visible papillary mass, an intraductal polypoid mass within localized ductal dilatation, intraductal castlike lesions within a mildly dilated duct, and a focal stricture-like lesion with mild proximal ductal dilatation. Awareness of the underlying risk factors and morphologic characteristics of intrahepatic cholangiocarcinoma is important for accurate diagnosis and for differentiation from other hepatic tumorous and nontumorous lesions.

Imaging of Chronic Recurrent Multifocal Osteomyelitis

Abstract: Chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory disorder of children and young adults that is characterized by nonbacterial osteomyelitis. Patients typically present with multifocal bone pain secondary to sterile osseous inflammation, and the disease has a relapsing and remitting course. The cause of CRMO remains unclear, although the results of several studies have suggested a genetic component. The typical imaging findings of CRMO include lytic and sclerotic lesions in the metaphyses of long bones and the medial clavicles. Other common sites of disease are the vertebral bodies, pelvis, ribs, and mandible. CRMO is often bilateral and multifocal at presentation. Owing to the lack of a diagnostic test, CRMO remains a diagnosis of exclusion. Although generally a self-limiting disease, CRMO can have a prolonged course and result in significant morbidity. Radiologists can be the first to suggest this diagnosis given its characteristic radiographic appearance and distribution of disease. Radiologists should be familiar with the typical imaging findings of CRMO to prevent unnecessary multiple biopsies and long-term antibiotic treatment in children with CRMO.

Diffusion-weighted Imaging in the Abdomen and Pelvis: Concepts and Applications

Abstract: Diffusion-weighted magnetic resonance (MR) imaging allows the detection of focal solid and cystic lesions in the abdomen and pelvis and, if pitfalls are to be avoided, is most effectively used in conjunction with other imaging sequences. It is important to recognize that the strength of the diffusion sensitizing gradient (b value) can and should be adjusted to ensure optimal evaluation of the body region or organ being imaged, and that more than one b value is necessary for tissue characterization. The success of lesion detection and characterization largely depends on the extent of tissue cellularity because increased cellularity is associated with impeded diffusion, as indicated by a reduction in the apparent diffusion coefficient. It is also important to recognize that certain normal tissues such as the endometrium are highly cellular and as such demonstrate restricted diffusion, which should not be misinterpreted as disease. Impeded diffusion can also be seen in highly viscous cystic lesions such as abscesses. Diffusion-weighted imaging is an evolving technology with the potential to improve tissue characterization when findings are interpreted in conjunction with findings obtained with other conventional MR imaging sequences.

Imaging-based Quantification of Hepatic Fat: Methods and Clinical Applications

Abstract: Fatty liver disease comprises a spectrum of conditions (simple hepatic steatosis, steatohepatitis with inflammatory changes, and end-stage liver disease with fibrosis and cirrhosis). Hepatic steatosis is often associated with diabetes and obesity and may be secondary to alcohol and drug use, toxins, viral infections, and metabolic diseases. Detection and quantification of liver fat have many clinical applications, and early recognition is crucial to institute appropriate management and prevent progression. Histopathologic analysis is the reference standard to detect and quantify fat in the liver, but results are vulnerable to sampling error. Moreover, it can cause morbidity and complications and cannot be repeated often enough to monitor treatment response. Imaging can be repeated regularly and allows assessment of the entire liver, thus avoiding sampling error. Selection of appropriate imaging methods demands understanding of their advantages and limitations and the suitable clinical setting. Ultrasonography is effective for detecting moderate or severe fatty infiltration but is limited by lack of interobserver reliability and intraobserver reproducibility. Computed tomography allows quantitative and qualitative evaluation and is generally highly accurate and reliable; however, the results may be confounded by hepatic parenchymal changes due to cirrhosis or depositional diseases. Magnetic resonance (MR) imaging with appropriate sequences (eg, chemical shift techniques) has similarly high sensitivity, and MR spectroscopy provides unique advantages for some applications. However, both are expensive and too complex to be used to monitor steatosis.

MR imaging of the small bowel

Abstract: Cross-sectional imaging techniques are playing an increasing role in the evaluation of suspected small-bowel disorders, and a growing awareness of the risks of ionizing radiation exposure has prompted the exploration of alternative imaging techniques. Advantages of magnetic resonance (MR) imaging include a lack of ionizing radiation, the ability to provide dynamic information regarding bowel distention and motility, improved soft-tissue contrast, and a relatively safe intravenous contrast agent profile. Limitations of MR imaging include cost, imager access, variability in examination quality, and lower spatial and temporal resolution compared with those of computed tomography (CT). MR imaging of the small bowel is indicated for patients with Crohn disease, those for whom exposure to radiation is a concern, those with contraindications to CT, and those with low-grade small-bowel obstruction. MR imaging may be performed with enterography or enteroclysis. In enterography, large volumes of fluid are ingested. Several different contrast agents may be used. These agents are classified according to their signal intensity on T1- and T2-weighted images. In enteroclysis, enteric contrast material is administered through a nasoenteric tube. Crohn disease is the primary indication for MR imaging of the small bowel because many patients require multiple follow-up examinations. Findings suggestive of active inflammation include bowel wall thickening and hyperenhancement, ulcerations, increased mesenteric vascularity, and perienteric inflammation. Complications are well depicted and may include penetrating disease and small-bowel obstruction.

Fatty Liver Disease: MR Imaging Techniques for the Detection and Quantification of Liver Steatosis

Abstract: Fatty liver disease is the most common cause of chronic liver disease in the United States. Noninvasive detection and quantification of fat is becoming more and more important clinically, due in large part to the growing prevalence of nonalcoholic fatty liver disease. Steatosis, the accumulation of fat-containing vacuoles within hepatocytes, is a key histologic feature of fatty liver disease. Liver biopsy, the current standard of reference for the assessment of steatosis, is invasive, has sampling errors, and is not appropriate in some settings. Several magnetic resonance (MR) imaging–based techniques—including chemical shift imaging, frequency-selective imaging, and MR spectroscopy—are currently in clinical use for the detection and quantification of fat-water admixtures, with each technique having important advantages, disadvantages, and limitations. These techniques permit the breakdown of the net MR signal into fat and water signal components, allowing the quantification of fat in liver tissue, and ar...

ALCAPA Syndrome: Not Just a Pediatric Disease

Abstract: Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) syndrome is a rare congenital coronary artery anomaly. There are two types of ALCAPA syndrome: the infant type and the adult type, each of which has different manifestations and outcomes. Infants experience myocardial infarction and congestive heart failure, and approximately 90% die within the 1st year of life. Rarely, ALCAPA syndrome manifests in adults; it may be an important cause of sudden cardiac death. Historically, ALCAPA syndrome was diagnosed at conventional angiography. However, the development of electrogardiographically gated multidetector computed tomographic (CT) angiography and magnetic resonance (MR) imaging enables accurate noninvasive imaging. At MR imaging and multidetector CT angiography, findings include direct visualization of the left coronary artery arising from the main pulmonary artery. Reversed flow from the left coronary artery into the main pulmonary artery may be seen at steady-state free-precession cine and fast cine phase-contrast MR imaging. Because of its ability to assess myocardial viability, which can be used as a prognostic factor to direct the need for surgical repair, MR imaging plays an important role in patient treatment. Restoration of a dual-coronary-artery system is the ideal surgical treatment for ALCAPA syndrome.

Small bowel obstruction: what to look for.

Abstract: Small bowel obstruction (SBO) is a common clinical syndrome for which effective treatment depends on a rapid and accurate diagnosis. Despite advances in imaging and a better understanding of small bowel pathophysiology, SBO is often diagnosed late or misdiagnosed, resulting in significant morbidity and mortality. A comprehensive approach that includes clinical findings, patient history, and triage examinations such as plain abdominal radiography will help the clinician develop an individualized treatment plan. When an SBO is accompanied by signs of strangulation, emergent surgical treatment is advised. If surgery cannot be performed immediately or if a partial obstruction is suspected, then a more detailed radiologic work-up is needed. The imaging techniques used subsequently vary according to the initial findings. If a low-grade partial obstruction is suspected, volume-challenge enteral examinations such as enteroclysis and computed tomographic (CT) enteroclysis are preferred. If a complete or high-grade obstruction is suspected, cross-sectional studies such as ultrasonography or multidetector CT are used to exclude strangulation. An algorithmic approach to imaging is proposed for the management of SBO to achieve accurate diagnosis of the obstruction; determine its severity, site, and cause; and assess the presence of strangulation. Radiologists have a pivotal role in clinical decision making in cases of SBO by providing answers to specific questions that significantly affect management.

MR imaging of liver fibrosis: current state of the art

Abstract: Chronic liver disease is a major public health problem worldwide. Liver fibrosis, a common feature of almost all causes of chronic liver disease, involves the accumulation of collagen, proteoglycans, and other macromolecules within the extracellular matrix. Fibrosis tends to progress, leading to hepatic dysfunction, portal hypertension, and ultimately cirrhosis. Liver biopsy, the standard of reference for diagnosing liver fibrosis, is invasive, costly, and subject to complications and sampling variability. These limitations make it unsuitable for diagnosis and longitudinal monitoring in the general population. Thus, development of a noninvasive, accurate, and reproducible test for diagnosis and monitoring of liver fibrosis would be of great value. Conventional cross-sectional imaging techniques have limited capability to demonstrate liver fibrosis. In clinical practice, imaging studies are usually reserved for evaluation of the presence of portal hypertension or hepatocellular carcinoma in cases that have progressed to cirrhosis. In response to the rising prevalence of chronic liver diseases in Western nations, a number of imaging-based methods including ultrasonography-based transient elastography, computed tomography-based texture analysis, and diverse magnetic resonance (MR) imaging-based techniques have been proposed for noninvasive diagnosis and grading of hepatic fibrosis across its entire spectrum of severity. State-of-the-art MR imaging-based techniques in current practice and in development for noninvasive assessment of liver fibrosis include conventional contrast material-enhanced MR imaging, double contrast-enhanced MR imaging, MR elastography, diffusion-weighted imaging, and MR perfusion imaging.

Secondary Tumors and Tumorlike Lesions of the Peritoneal Cavity: Imaging Features with Pathologic Correlation

Abstract: Tumors and tumorlike lesions that secondarily involve the mesothelial or submesothelial layers of the peritoneum are a diverse group of disorders that range in biologic behavior from benign to highly malignant. The anatomy of peritoneal ligaments and mesenteries and the normal circulation of peritoneal fluid dictate location and distribution of these diseases within the peritoneal cavity. Peritoneal carcinomatosis is the most common secondary tumor to affect the peritoneal cavity. When it arises from carcinomas of the gastrointestinal tract or ovary, the prognosis is grave. However, when low-grade mucinous adenocarcinoma of the appendix spreads to the peritoneal cavity, the consequence is typically pseudomyxoma peritonei, which is a clinical syndrome, characterized by recurrent and recalcitrant voluminous mucinous ascites due to surface growth on the peritoneum without significant invasion of underlying tissues. Carcinomas from elsewhere in the body, as well as lymphomas and sarcomas, may also produce diffuse peritoneal metastasis. Granulomatous peritonitis is the consequence of disseminated infection such as tuberculosis or histoplasmosis, foreign materials, or rupture of a tumor or hollow viscus. Finally, a group of benign miscellaneous conditions that range from common disorders such as endometriosis and splenosis to very rare conditions such as gliomatosis peritonei and melanosis may also affect the peritoneum diffusely. Secondary tumors and tumorlike lesions of the peritoneum have overlapping imaging features when compared with each other and primary peritoneal tumors. Knowledge of peritoneal anatomy, normal fluid circulation within the peritoneal cavity, and clinical and pathologic features of secondary peritoneal lesions is essential for identification of these lesions.

Normal Variants of the Cerebral Circulation at Multidetector CT Angiography

Abstract: Multidetector computed tomographic (CT) angiography is used in many institutions for initial evaluation of the cerebral circulation for acute stroke and subarachnoid hemorrhage as well as in various preoperative settings. A comprehensive CT examination that includes a review of three-dimensional and maximum intensity projection images of the intra- and extracranial arteries and axial images of the skull base (obtained with bone window settings) allows identification of most abnormalities and normal variants. Knowledge of the presence and clinical relevance of normal variants such as fenestrations, duplications, and persistent fetal arteries plays a crucial role in the diagnosis and management of acute stroke and subarachnoid hemorrhage and may aid in surgical planning. For example, the preoperative detection of a medial or intrasellar persistent trigeminal artery may help surgeons avoid a potentially life-threatening hemorrhage in a patient undergoing transsphenoidal surgery for pituitary adenoma. However, the significance of normal variants diverges widely: A clinically important association has been observed between fenestration and intracranial aneurysm formation, whereas early branching of the middle cerebral artery is not associated with an increased risk of aneurysm formation and has little clinical significance. Supplemental material available at http://radiographics.rsnajnls.org/cgi/content/full/29/4/1027/DC1.

Biliary MR Imaging with Gd-EOB-DTPA and Its Clinical Applications

Abstract: The clinical applications of Gd-EOB-DTPA–enhanced MR imaging combined with conventional T2-weighted MR cholangiography are reviewed, with emphasis on the potential of this technique to allow morphologic and functional assessment of the biliary system.

Diffusion-weighted MR Imaging of Female Pelvic Tumors: A Pictorial Review

Abstract: Functional imaging is becoming increasingly important in the evaluation of cancer patients because of the limitations of morphologic imaging, particularly in the assessment of response to therapy. Diffusion-weighted magnetic resonance (MR) imaging has been established as a useful functional imaging tool in neurologic applications for a number of years, but recent technical advances now allow its use in abdominal and pelvic applications. Diffusion-weighted MR imaging studies of female pelvic tumors have shown reduced apparent diffusion coefficient (ADC) values within cervical and endometrial tumors. In addition, this unique noninvasive modality has demonstrated the capacity to help discriminate between benign and malignant uterine lesions and to help assess the extent of peritoneal spread from gynecologic malignancies. Potential pitfalls can be avoided by reviewing diffusion-weighted MR imaging findings in conjunction with anatomic imaging findings. Increasing familiarity with ADC calculation and manipulation software will allow radiologists to provide new information for the care of patients with known or suspected gynecologic malignancies.

From the archives of the AFIP: musculoskeletal fibromatoses: radiologic-pathologic correlation.

Abstract: Musculoskeletal fibromatoses represent a wide spectrum of fibroblastic and myofibroblastic neoplasms with similar pathologic appearances and variable clinical behavior. These lesions can be categorized by location (superficial or deep) or by the age group predominantly affected. Superficial fibromatoses in adults (palmar and plantar) and children (calcifying aponeurotic fibroma, lipofibromatosis, and inclusion body fibromatosis) are often small slow-growing lesions; their diagnosis is suggested by location. Deep fibromatoses in adults (desmoid type and abdominal wall) and children (fibromatosis colli and myofibroma and myofibromatosis) are frequently large and more rapidly enlarging; location of these lesions may be nonspecific. Radiographic findings typically are nonspecific. Cross-sectional imaging (ultrasonography, computed tomography, or magnetic resonance [MR] imaging) reveals lesion location, extent, and involvement of adjacent structures for staging and evaluation of local recurrence. MR imaging findings of predominantly low to intermediate signal intensity, nonenhancing bands of low signal intensity on long repetition time MR images that represent collagenized regions, and extension along fascial planes ("fascial tail" sign) add specificity for diagnosis. Additional features that aid in diagnostic specificity include an abdominal wall location related to pregnancy (abdominal wall fibromatosis), a lower neck location in a young child (fibromatosis colli), an adipose component (lipofibromatosis), or multiple lesions in young children (myofibromatosis). Treatment may be conservative or surgical resection, depending on the specific diagnosis. Local recurrence is common after surgical resection owing to the infiltrative growth of these lesions. Recognition that the appearances of the various types of musculoskeletal fibromatoses reflect their pathologic characteristics improves radiologic assessment and helps optimize patient management.

A Pattern-based Approach to Assessment of Delayed Enhancement in Nonischemic Cardiomyopathy at MR Imaging

Abstract: Although delayed contrast material-enhanced cardiac magnetic resonance (MR) imaging has traditionally been used to evaluate ischemic disease and myocardial viability, it is increasingly being used in the evaluation of nonischemic cardiomyopathies. Unlike myocardial infarction, which demonstrates subendocardial or transmural delayed contrast enhancement in a vascular distribution, nonischemic cardiomyopathies demonstrate enhancement that is not limited to a vascular territory. In combination with other cardiac MR imaging features, the location (subendocardial, transmural, subepicardial, or mesocardial) and pattern (patchy or diffuse) of abnormal delayed myocardial enhancement allow differentiation between ischemic (infarct-related) and nonischemic cardiomyopathies and, in cases of nonischemic cardiomyopathy, narrowing of the differential diagnosis. With use of a structured approach, delayed contrast-enhanced cardiac MR imaging can be helpful in the early detection and appropriate treatment of nonischemic cardiomyopathies.

Adrenal Mass Imaging with Multidetector CT: Pathologic Conditions, Pearls, and Pitfalls

Abstract: The adrenal gland is involved by a range of neoplasms, including primary and metastatic malignant tumors; however, the most common tumor detected is the incidental benign adenoma. Although computed tomographic (CT) findings will not always yield a definitive diagnosis, attention to these findings provides a road map to guide image interpretation. Adenomas typically demonstrate rapid washout, which is defined as an absolute percentage washout (APW) of more than 60% and a relative percentage washout (RPW) of more than 40% on delayed images. Adrenocortical carcinoma typically has an RPW of less than 40%; however, large size and heterogeneity are more reliable indicators of the diagnosis than are washout values. Washout characteristics of pheochromocytoma are variable; in conjunction with high levels of dynamic enhancement, pheochromocytomas may mimic adenoma (ie, APW > 60%, RPW > 40%). Myelolipomas appear as well-defined masses with variable quantities of fat and soft tissue. After contrast material administration, metastases usually demonstrate slower washout on delayed images (APW < 60%, RPW < 40%) than do adenomas, although hypervascular metastases may enhance similarly to pheochromocytoma. Finally, a number of nonadrenal pathologic conditions have been reported to mimic adrenal masses at CT.

MR Imaging Assessment of the Spine: Infection or an Imitation?

Abstract: Magnetic resonance (MR) imaging is a powerful diagnostic tool that can be used to help evaluate spinal infection and to help distinguish between an infection and other clinical conditions. In most cases of spinal infection, MR images show typical findings such as vertebral endplate destruction, bone marrow and disk signal abnormalities, and paravertebral or epidural abscesses. However, it is not always easy to diagnose a spinal infection, particularly when some of the classic MR imaging features are absent or when there are unusual patterns of infectious spondylitis. Furthermore, noninfectious inflammatory diseases and degenerative disease may simulate spinal infection. It is necessary to be familiar with atypical MR imaging findings of spinal infection and features that may mimic spinal infection to avoid misdiagnosis and inappropriate treatment. © RSNA, 2009

Schatzker Classification of Tibial Plateau Fractures: Use of CT and MR Imaging Improves Assessment

Abstract: The Schatzker classification system for tibial plateau fractures is widely used by orthopedic surgeons to assess the initial injury, plan management, and predict prognosis. Many investigators have found that surgical plans based on plain radiographic findings were modified after preoperative computed tomography (CT) or magnetic resonance (MR) imaging. The Schatzker classification divides tibial plateau fractures into six types: lateral plateau fracture without depression (type I), lateral plateau fracture with depression (type II), compression fracture of the lateral (type IIIA) or central (type IIIB) plateau, medial plateau fracture (type IV), bicondylar plateau fracture (type V), and plateau fracture with diaphyseal discontinuity (type VI). Management of type I, II, and III fractures centers on evaluating and repairing the articular cartilage. The fracture-dislocation mechanism of type IV fractures increases the likelihood of injury to the peroneal nerve or popliteal vessels. In type V and VI fractures,...

Volvulus of the gastrointestinal tract: appearances at multimodality imaging.

Abstract: Volvulus of the gastrointestinal tract, a clinically relevant cause of acute or recurring abdominal pain in adults, remains a diagnostic dilemma for radiologists in a large number of cases. The clinical symptoms associated with volvulus are often nonspecific and include pain and nausea with vomiting. Yet referring clinicians often rely on radiologists to make the diagnosis; volvulus is rarely diagnosed clinically. Radiography, fluoroscopy, and computed tomography are the imaging methods most often used for this purpose. Prompt diagnosis is critical to avoid life-threatening complications such as bowel ischemia and infarction. Thus, it is useful for radiologists to be familiar with the various appearances of volvulus throughout the gastrointestinal tract.

Imaging of the placenta: a multimodality pictorial review.

Abstract: The placenta is often overlooked in the routine evaluation of a normal gestation, receiving attention only when an abnormality is detected. Although uncommon, abnormalities of the placenta are important to recognize owing to the potential for maternal and fetal morbidity and mortality. Pathologic conditions of the placenta include placental causes of hemorrhage, gestational trophoblastic disease, retained products of conception, nontrophoblastic placental tumors, metastases, and cystic lesions. Sonography remains the imaging modality of choice for evaluation of the placenta. Magnetic resonance (MR) imaging can be of added diagnostic value when further characterization is required, particularly in the setting of invasive placental processes such as placenta accreta and gestational trophoblastic disease. Computed tomography (CT) has a limited role in the evaluation of placental disease owing to limited tissue characterization, compared with that of MR imaging, and the radiation risk to the fetus; this risk often outweighs the benefit. The primary role for CT is in the evaluation of trauma and gestational trophoblastic disease, for which it allows characterization of the primary lesion and distant metastases.

Invasive Lobular Carcinoma of the Breast: Spectrum of Mammographic, US, and MR Imaging Findings

Abstract: The reported prevalence of invasive lobular carcinoma (ILC) is variable, with more recent studies indicating that ILC accounts for 10%-15% of all invasive breast carcinomas. However, the radiologic diagnosis and management of ILC can be uniquely challenging. Current imaging modalities are not very specific for differentiating ILC from other invasive breast cancers, and ILC has a tendency to have appearances at mammography that are atypical for invasive ductal carcinomas, resulting in higher false-negative rates. The clinical detection of ILC can also be difficult, since ILC frequently fails to form a palpable lesion. This tendency of ILC to have atypical imaging and clinical appearances is related to its histopathologic features and its failure to elicit a desmoplastic response. Despite these diagnostic challenges, however, imaging remains crucial in the detection and management of ILC. Mammography, ultrasonography (US), and magnetic resonance (MR) imaging all play important roles, with each modality having its own advantages and limitations. The use of US and MR imaging as adjuncts to mammography increases sensitivity in the detection of ILC and provides useful information for further management and presurgical planning. Familiarity with the spectrum of imaging appearances of ILC is essential.

CT Diagnosis of Chronic Pulmonary Thromboembolism

Abstract: Chronic pulmonary thromboembolism is mainly a consequence of incomplete resolution of pulmonary thromboembolism. Increased vascular resistance due to obstruction of the vascular bed leads to pulmonary hypertension. Chronic thromboembolic pulmonary hypertension is clearly more common than previously was thought, and misdiagnosis is common because patients often present with nonspecific symptoms related to pulmonary hypertension. Computed tomography (CT) is a useful alternative to conventional angiography not only for diagnosing chronic pulmonary thromboembolism but also for determining which cases are treatable with surgery and confirming technical success postoperatively. The vascular CT signs include direct pulmonary artery signs (complete obstruction, partial obstruction, eccentric thrombus, calcified thrombus, bands, webs, poststenotic dilatation), signs related to pulmonary hypertension (enlargement of main pulmonary arteries, atherosclerotic calcification, tortuous vessels, right ventricular enlargement, hypertrophy), and signs of systemic collateral supply (enlargement of bronchial and nonbronchial systemic arteries). The parenchymal signs include scars, a mosaic perfusion pattern, focal ground-glass opacities, and bronchial anomalies. The presence of one or more of these radiologic signs arouses suspicion and allows diagnosis of this entity. Early recognition of chronic pulmonary thromboembolism may help improve the outcome, since the condition is potentially curable with pulmonary thromboendarterectomy.

Pediatric soft-tissue tumors and pseudo-tumors: MR imaging features with pathologic correlation: part 1. Imaging approach, pseudotumors, vascular lesions, and adipocytic tumors.

Abstract: A wide spectrum of entities may give rise to soft-tissue masses in children, including benign and malignant tumors, pseudotumors, and both neoplastic and nonneoplastic vascular lesions. Because of its excellent tissue contrast, multiplanar capability, and lack of ionizing radiation, magnetic resonance (MR) imaging has become the modality of choice in the evaluation of deep and large soft-tissue masses in children. In the vast majority of cases, however, accurate interpretation of the MR imaging findings requires correlation with the clinical findings. For example, in most posttraumatic and inflammatory pseudotumors, the clinical history is fundamental to establishing the diagnosis. In the evaluation of periarticular cysts, the location of the mass and its relationship to a joint are crucial for diagnosis, whereas in the evaluation of vascular lesions, including hemangiomas and vascular malformations, clinical findings combined with MR imaging findings are needed for accurate diagnosis in most cases. The i...

Multimodality Assessment of Esophageal Cancer: Preoperative Staging and Monitoring of Response to Therapy

Abstract: Esophageal cancer is a leading cause of cancer mortality worldwide. Complete resection of esophageal cancer and adjacent malignant lymph nodes is the only potentially curative treatment. Accurate preoperative staging and assessment of therapeutic response after neoadjuvant therapy are crucial in determining the most suitable therapy and avoiding inappropriate attempts at curative surgery. Computed tomography (CT) is recommended for initial imaging following confirmation of malignancy at pathologic analysis, primarily to rule out unresectable or distant metastatic disease. With the advent of multidetector CT, use of thin sections and multiplanar reformation allows more accurate staging of esophageal cancer. Endoscopic ultrasonography (US) is the best modality for determining the depth of tumor invasion and presence of regional lymph node involvement. Combined use of fine-needle aspiration and endoscopic US can improve assessment of lymph node involvement. Positron emission tomography (PET) is useful for assessment of distant metastases but is not appropriate for detecting and staging primary tumors. PET may also be helpful in restaging after neoadjuvant therapy, since it allows identification of early response to treatment and detection of interval distant metastases. Each imaging modality has its advantages and disadvantages; therefore, CT, endoscopic US, and PET should be considered complementary modalities for preoperative staging and therapeutic monitoring of patients with esophageal cancer.

MR Imaging and CT of the Biliary Tract

Abstract: Magnetic resonance (MR) imaging and computed tomography (CT) can be useful in the diagnosis of biliary disease, with both modalities allowing detailed evaluation of the biliary tract. Careful interrogation of the images is critical, regardless of modality. The identification of dilated bile ducts necessitates evaluation for strictures or filling defects, which is best performed with thin-section imaging. Smooth, concentric short-segment strictures favor a benign cause, whereas abrupt, eccentric long-segment strictures favor a malignancy. At MR imaging, extrabiliary entities such as crossing vessels or metallic clip artifact may mimic strictures and should not be mistaken for disease. A stone is the most common biliary filling defect and may occur in the absence of dilated ducts. Stones commonly have a lamellated, geometric shape and are found in a dependent portion of the duct. Identification of bile duct wall thickening raises concern for cholangitis or malignancy. Improved diagnosis of biliary disease can be achieved with a knowledge of the benefits and limitations of modern MR and CT cholangiographic techniques, including the use of biliary-excreted contrast material and of various postprocessing techniques. Familiarity with the radiologic appearances of the duct lumen, wall, and surrounding structures is also important for accurate image interpretation. The rapidly evolving technology for both MR imaging and CT of the biliary tract will continue to present radiologists with opportunities as well as challenges.

Coronary artery aneurysms and ectasia: role of coronary CT angiography.

Abstract: Coronary artery dilatations-aneurysms and ectasia-are an uncommon and frequently unrecognized incidental finding in patients with coronary artery disease. Aneurysms and ectasia are associated with a vast group of disorders, and the evaluation and characterization of coronary aneurysms and ectasia represent a great diagnostic task with clinical and therapeutic implications. The underlying etiology is variable and includes degenerative, congenital, inflammatory, infectious, toxic, and traumatic causes. Unlike aneurysms, ectasia is more frequently seen in association with atherosclerosis or as a compensatory mechanism in those cases in which a proximal stenosis is noted in the opposite coronary artery; ectasia is also seen in some coronary artery anomalies, such as anomalous origin from the pulmonary artery, or as a result of a high-flow state, as seen in coronary artery fistulas. The diagnostic approach depends on the clinical scenario, and nowadays, noninvasive evaluation with multidetector computed tomography is possible. Imaging assessment should include evaluation of (a) the distribution, (b) maximal diameter, (c) presence or absence of intraluminal thrombi, (d) number, (e) extension, and (f) associated complications such as myocardial infarction. This article presents an overview of the definition, classification, etiology, clinical manifestations, and potential complications of coronary artery aneurysms and ectasia.

From the archives of the AFIP: breast masses in children and adolescents: radiologic-pathologic correlation.

Abstract: The spectrum of breast lesions in children and adolescents varies markedly from that for adults, with the former lesions being overwhelmingly benign. A breast mass in a young boy or girl may arise from normal and abnormal breast development. Other causes of masses include infection, trauma, and cyst formation. After onset of puberty, most cases of breast enlargement arise from benign fibroadenoma in girls and gynecomastia in boys. These conditions have specific imaging appearances, although juvenile (often giant) fibroadenoma cannot be distinguished from phyllodes tumor, which can be benign or malignant. In children, both conditions usually appear as well-circumscribed, hypoechoic masses at sonography and show diffuse enhancement except for nonenhancing septations at magnetic resonance imaging. A diagnosis of juvenile papillomatosis (a benign lesion) portends later development of breast cancer, and patients with this condition should be closely monitored. Malignant lesions of the breast in children are rare. The most common malignant lesions are metastases and are usually associated with widespread disease. The most common primary breast malignancy is malignant phyllodes tumor. Primary breast carcinoma is exceedingly rare in the pediatric age group, but its imaging appearance in children is the same as seen in adults and is different from that of almost all benign lesions. In girls, diagnostic interventions may injure the developing breast and cause subsequent disfigurement. Given this risk and the low prevalence of malignant disease in this population, a prudent course should be followed in the diagnosis of breast lesions. Imaging findings are very helpful for selecting patients for further diagnostic procedures. Although malignancy is rare, lesions with suspicious imaging findings or progressive growth should be subjected to cytologic or histologic examination.

Pigmented Lesions of the Central Nervous System: Radiologic-Pathologic Correlation

Abstract: Pigmented lesions of the central nervous system (CNS) are a diverse group of entities that run the gamut from benign to malignant. These lesions may be well circumscribed or diffuse, and their imaging appearances are influenced by the degree of melanin content as well as the presence or absence of hemorrhage. Pigmented lesions include primary melanocytic lesions of the CNS and metastatic melanoma, as well as other CNS neoplasms that may undergo melanization, including schwannoma, medulloblastoma, and some gliomas. Primary melanocytic lesions of the CNS arise from melanocytes located within the leptomeninges, and this group includes diffuse melanocytosis and meningeal melanomatosis (seen in neurocutaneous melanosis), melanocytoma, and malignant melanoma. Primary melanin-containing lesions of the CNS must be differentiated from metastatic melanoma because these lesions require different patient workup and therapy. Absence of a known primary malignant melanoma helps in the differential diagnosis, but an occult primary lesion outside the CNS must be sought and excluded. Pigmented lesions of the CNS are uncommon, and knowledge of their imaging characteristics and pathologic features is essential for their identification.