Technical considerations: CT and MR imaging in the postoperative orthopedic patient

Cross-sectional imaging utilizing computed tomography (CT) and magnetic resonance (MR) imaging have become routine components in the imaging assessment of patients with musculoskeletal disease. Unfortunately, in the setting of a postoperative orthopedic patient with associated orthopedic metallic instrumentation, these imaging techniques are prone to artifacts resulting in image quality degradation. An understanding of the physical basis of such metal-related artifacts, and their appearance on CT and MR imaging, has led investigators to the implementation of a series of techniques and modifications to imaging protocols to decrease CT and MR imaging artifacts in the vicinity of metallic instrumentation. Utilizing such modified imaging techniques, consistent, improved CT and MR image quality may be achieved in imaging of the postoperative orthopedic patient.     

Detection and characterization of focal hepatic lesions: comparative study of MDCT and gadobenate dimeglumine-enhanced MR imaging

The aim of this study was to compare the diagnostic performance of multidetector row helical CT (MDCT) and gadobenate dimeglumine-enhanced magnetic resonance (MR) imaging (in the detection and characterization of focal liver lesions. Two blind reviewers analyzed the MDCT and MR images of a total of 44 malignant and 85 benign lesions in 46 patients independently. Receiver operating characteristic curves were established to analyze the results for each reviewer and modality.     

Left ventricular function studied with MDCT

Accurate determination of left ventricular (LV) myocardial function is fundamental for clinical diagnosis, risk stratification, and estimation of prognosis in patients with ischemic and nonischemic cardiomyopathy. Primarily, multi-detector-row spiral CT (MDCT) of the heart aimed at detecting coronary artery obstruction and cardiac morphology. Multiple studies have demonstrated that retrospectively, ECG-gated MDCT determination of LV volumes and consequently global LV function parameters is feasible in good agreement with established imaging modalities such as cineventriculography, echocardiography, and cine magnetic resonance imaging (CMR). Post-processing tools allow fast and semi-automatic determination of LV function parameters from MDCT data in analogy to known CMR evaluation approaches. Although MDCT is not considered to be first-line modality for LV function assessment, this technique provides accessory dynamic information in patients undergoing MDCT coronary angiography, contributing to combined assessment of cardiac morphology and function without need of additional radiation exposure. MDCT regional LV wall motion analysis at rest is feasible, but further improvement in temporal resolution seems mandatory to match results obtained from competing modalities. This paper will discuss the diagnostic potential of MDCT for assessment of LV function with regards to accuracy and clinical applications, as well as limitations, particularly in comparison with CMR as modality of reference.     

Prediction of vascular involvement and resectability by multidetector-row CT versus MR imaging with MR angiography in patients who underwent surgery for resection of pancreatic ductal adenocarcinoma

Purpose

To compare the diagnostic value of dual-phase multidetector-row CT (MDCT) and MR imaging with dual-phase three-dimensional MR angiography (MRA) in the prediction of vascular involvement and resectability of pancreatic ductal adenocarcinoma.

Methods and materials

116 patients with proven pancreatic adenocarcinoma underwent both MDCT and combined MR imaging prior to surgery. Of 116 patients, 56 who underwent surgery were included. Two radiologists independently attempt to assess detectability, vascular involvement and resectability of pancreatic adenocarcinoma on both images. Results were compared with surgical findings and statistical analysis was performed.

Results

MDCT detected pancreatic mass in 45 of 56 patients (80.3%) and MR imaging in 44 patients (78.6%). In assessment of vascular involvement, sensitivities and specificities of MDCT were 61% and 96% on a vessel-by-vessel basis, respectively. Those of MR imaging were 57% and 98%, respectively. In determining resectability, sensitivities and specificities of MDCT were 90% and 65%, respectively. Those of MR imaging were 90% and 41%, respectively. There was no statistical difference in detecting tumor, assessing vascular involvement and determining resectability between MDCT and MR imaging (p = 0.5).

Conclusion

MDCT and MR imaging with MRA demonstrated an equal ability in detection, predicting vascular involvement, and determining resectability for a pancreatic ductal adenocarcinoma.     

Marfan syndrome: evaluation with MR imaging versus CT

Twenty-five patients with Marfan syndrome underwent computed tomography (CT) and magnetic resonance (MR) imaging. MR images were interpreted in blinded fashion and then the results were compared with findings from CT scans. MR imaging was found to be equivalent to CT in the depiction of aortic, dural, and hip abnormalities in patients who had not undergone surgery. MR imaging was superior to CT in evaluation of postoperative patients because the artifact produced by Bjork-Shiley or St. Jude valves precludes adequate evaluation of the aortic root on CT scans, while producing only a small inferior field distortion, a "pseudo-ventricular septal defect," on MR images. The absence of radiation exposure is another significant advantage for the relatively young Marfan syndrome population, who require serial studies. MR imaging is the modality of choice for evaluation and follow-up of patients with Marfan syndrome and offers an appropriate means of screening their kindred.     

Detection of hypervascular malignant foci in borderline lesions of hepatocellular carcinoma: comparison of dynamic multi-detector row CT, dynamic MR imaging and superparamagnetic iron oxide-enhanced MR imaging

The study object was to retrospectively compare the detection rate of hypervascular foci visualized by CT during hepatic arteriography (CTHA) in borderline nodules, which was observed upon cirrhotic livers, on dynamic MDCT, dynamic gadolinium-enhanced MR (dynamic MR), and SPIO-enhanced MR imaging. Eighty-five nodules in 49 patients with cirrhosis were evaluated. When a part of the nodule showed hyperdensity relative to the surrounding areas of the nodule on CTHA, it was defined as "hypervascular focus." The relationships between the dynamic MDCT and dynamic MR and SPIO-enhanced MR imaging findings of these foci were analyzed using X(2) test. Hypervascular foci were detected in 17 (53%) of 32 on the arterial dominant phase of dynamic MDCT, in 19 (37%) of 51 on the arterial dominant phase of dynamic MR and in 6 (26%) of 23 on SPIO-enhanced MR imaging. Arterial dominant phase of dynamic MDCT demonstrated a significantly higher detection rate of hypervascular foci less than 5 mm in diameter than did dynamic and SPIO MR imaging (p<0.05). Hypervascular foci in borderline nodules could be better visualized by dynamic MDCT than by gadolinium- and SPIO-enhanced MR imaging. Dynamic MDCT is recommended for the follow-up examination of hypovascular borderline lesions.     

Imaging of diffuse lung diseases. Past, present, and future

For many years the plain chest radiograph was the only imaging modality used in the assessment of patients who had diffuse lung disease. Presently, high resolution computed tomography (CT) and lung scintigraphy play a major role in the assessment of these patients. Use of magnetic resonance (MR) imaging in the assessment of the lung parenchyma has been limited by poor signal-to-noise ratio and physiologic motion. Recent improvements in technique, however, have allowed assessment of patients with diffuse lung disease. It is likely that MR imaging will play an increasing role in the assessment of these patients in the near future.     

Multidetector CT of the spine in multiple myeloma: comparison with MR imaging and radiography

OBJECTIVE: The purpose of this study was to compare multidetector CT (MDCT) of the thoracic and lumbar segments of the spine with MR imaging and conventional radiography for bone lesion detection and for evaluating the risk of vertebral fracture in multiple myeloma. SUBJECTS AND METHODS: Eighteen patients with multiple myeloma stage III (according to the criteria of Durie and Salmon) underwent MDCT, conventional radiography, and MR imaging of the lumbar and thoracic spine. MDCT was performed using a standard protocol with no contrast material. Source images were reconstructed using an effective slice thickness of 3 mm with an overlapping reconstruction increment (0.8 mm). Secondary coronal and sagittal multiplanar reformations were exclusively used for establishing the diagnosis. Findings were compared with those of MR imaging and conventional radiography. RESULTS: In all patients, coronal and sagittal multiplanar reformations depicted the extent of osseous destruction and provided detailed information about osseous infiltration and potential bone instability. Compared with conventional radiography, an additional 24 affected vertebrae, 15 additional vertebral fractures, and six vertebrae at further risk of fracture were detected on MDCT. Compared with MR imaging, three additional endangered vertebrae were detected on MDCT. MR imaging alone would have lead to an understaging of five (27.8%) of 18 patients. Using combined radiography and MR imaging, disease in three (16.7%) of 18 patients would have been understaged. CONCLUSION: MDCT seems to be preferable to conventional radiography in evaluating bone destruction in multiple myeloma. In combination with MR imaging, detailed information for staging these tumors is obtained. For the initial staging in patients with multiple myeloma, MDCT in combination with MR imaging seems to be the method of choice.     

克罗恩病合并泌尿系结石的多层螺旋CT检查价值

目的：比较分析多层螺旋CT对克罗恩病（CD）与非CD病例合并泌尿系结石的检出率及其价值。方法：回顾性分析308例病理证实的CD病例和300例非CD病例的影像学资料,计算多层螺旋CT对CD与非CD病例合并泌尿系结石的检出率,比较两种疾病泌尿系结石发病率的差异。结果：CT对CD与非CD病例的泌尿系结石的检出率分别为13%和1.3%,二者之间差异具有统计学意义（χ2=30.745,P=0.000）。结论：CD病例的泌尿系结石发病率高于一般非CD人群,多层螺旋CT能在显示肠道病变的同时显示泌尿系结石,具有较好的临床价值。     

Multidetector CT evaluation of abdominal trauma

CT is the imaging modality of choice to evaluate blunt abdominal trauma. With the advent of multidetector CT (MDCT), scanning times have progressively decreased while image resolution has increased owing to thinner collimation and reduced partial volume and motion artifacts. MDCT also allows high quality two-dimensional and three-dimensional multiplanar reformatted images to be obtained, which aid in the diagnosis of the complex multisystem injuries seen in the trauma patient. This article describes the authors' current imaging protocol with 16-detector MDCT, the spectrum of CT findings seen in patients with blunt abdominal injuries, and the role MDCT has in guiding injury management.     

Evaluation of cardiac function and myocardial viability with 16- and 64-slice multidetector computed tomography

Retrospectively ECG-gated MDCT shows a high correlation and acceptable agreement of left-ventricular functional parameters compared to MR imaging. Thus, in addition to the non-invasive evaluation of coronary arteries, further important additional information of left-ventricular functional parameters with clinical and prognostic relevance can be achieved by one single MDCT examination. For assessment of myocardial viability, low-dose CT late enhancement scanning is feasible, and preliminary results look promising. CT late enhancement adds valuable diagnostic information on the haemodynamical significance of coronary stenoses or prior to interventional procedures.     

Reperfusion injury components and manifestations determined by cardiovascular MR and MDCT imaging

Advances in magnetic resonance (MR) and computed tomography (CT) imaging have improved visualization of acute and scar infarct. Over the past decade, there have been and continues to be many significant technical advancements in cardiac MR and multi-detector computed tomography (MDCT) technologies. The strength of MR imaging relies on a variety of pulse sequences and the ability to noninvasively provide information on myocardial structure, function and perfusion in a single imaging session. The recent technical developments may also allow CT technologies to rise to the forefront for evaluating clinical ischemic heart disease. Components of reperfusion injury including myocardial edema, hemorrhage, calcium deposition and microvascular obstruction (MO) have been demonstrated using MR and CT technologies. MR imaging can be used serially and noninvasively in assessing acute and chronic consequences of reperfusion injury because there is no radiation exposure or administration of radioactive materials. MDCT is better suited for assessing coronary artery stenosis and as an alternative technique for assessing viability in patients where MR imaging is contraindicated. Changes in left ventricular (LV) volumes and function measured on cine MR are directly related to infarct size measured on delayed contrast enhanced images. Recent MR studies found that transmural infarct, MO and peri-infarct zone are excellent predictors of poor post-infarct recovery and mortality. Recent MR studies provided ample evidence that growth factor genes and stem cells delivered locally have beneficial effects on myocardial viability, perfusion and function. The significance of deposited calcium in acute infarct detected on MDCT requires further studies. Cardiac MR and MDCT imaging have the potential for assessing reperfusion injury components and manifestations.     

Traumatic injuries: imaging of abdominal and pelvic injuries

The availability of new imaging modalities has altered the diagnostic approach to patients with abdominal and pelvic trauma. Computed tomography and ultrasound have largely replaced diagnostic peritoneal lavage. Ultrasound is used in most trauma centers as the initial imaging technique for the detection of hemoperitoneum and helps to determine the need for emergency laparotomy. Computed tomography allows for an accurate diagnosis of a wide range of traumatic abdominal and pelvic conditions. The speed of single-detector helical and multi-detector row CT (MDCT) permits a rapid CT examination of the seriously ill patient in the emergency room. In particular, the technology of MDCT permits multiple, sequential CT scans to be quickly obtained in the same patient, which is a great advance in the rapid assessment of the multiple-injured patient. The evolving concepts in trauma care promoting non-operative management of liver and splenic injuries creates the need for follow-up cross-sectional imaging studies in these patients. Computed tomography and, less frequently, MR or ultrasound, are used for this purpose.     

Evaluation of focal pancreatic masses: comparison of mangafodipir-enhanced MR imaging and contrast-enhanced helical CT

The detection and characterization of pancreatic tumors as well as the reliable staging of pancreatic cancer are important tasks for radiologic evaluation. Contrast-enhanced helical CT has been the standard modality for pancreatic imaging in many institutions, but MR imaging has gained a considerable role in the evaluation of patients with equivocal CT findings. Recently, the first organ-specific MR contrast agent targeted to the liver and pancreas, mangafodipir trisodium, has been registered in the European Union (EU) for use in MR imaging of the pancreas. This paper reviews technical considerations and characteristic imaging findings of mangafodipir-enhanced MR imaging in the assessment of focal pancreatic lesions. Contrast-enhanced MRI has proven to be very helpful in the detection of small tumors or the identification of tumor-simulating lesions in patients with equivocal CT findings. Mangafodopir may improve the staging of pancreatic cancer by increasing the sensitivity of MRI in the detection of liver metastases. This review summarizes the potential of contrast-enhanced MRI and the limitations compared with contrast-enhanced helical CT. Electronic Publication     

Evaluation of cardiac function and myocardial viability with 16- and 64-slice multidetector computed tomography

Retrospectively ECG-gated MDCT shows a high correlation and acceptable agreement of left-ventricular functional parameters compared to MR imaging. Thus, in addition to the non-invasive evaluation of coronary arteries, further important additional information of left-ventricular functional parameters with clinical and prognostic relevance can be achieved by one single MDCT examination. For assessment of myocardial viability, low-dose CT late enhancement scanning is feasible, and preliminary results look promising. CT late enhancement adds valuable diagnostic information on the haemodynamical significance of coronary stenoses or prior to interventional procedures.     

Assessment of ischemic heart disease with electron-beam CT and MR imaging

Anatomical and functional information derived from diagnostic modalities is essential in cardiac imaging. Electron-beam CT and MR imaging have played a role in the assessment of cardiac function, and recent developments in both modalities have permitted non-invasive visualization of coronary artery stenosis, which previously had been demonstrated exclusively by catheter coronary angiography. In this article, coronary artery imaging and cardiac functional imaging were reviewed by focusing on new technical developments in the screening of coronary atherosclerosis leading to acute coronary syndrome. Quantitative assessment of coronary calcifications by electron-beam CT has already become one of the most useful techniques for predicting the degree of coronary atherosclerosis and the risk of coronary events in individual patients. Electron-beam CT and MR imaging have also provided non-invasive clinical tools with which to demonstrate coronary artery stenosis. Visualization and characterization of atheromatous plaque at the coronary artery has recently been attempted with MR imaging, since this might lead to the detection of coronary artery plaque that was likely to rupture, thereby possibly predicting and preventing acute coronary syndrome in asymptomatic individuals. Although electron-beam CT and MR imaging have not been fully incorporated into routine clinical practice, each could serve as a comprehensive modality for the assessment of ischemic heart disease.     

Detection of pelvic lymph node metastases in gynecologic malignancy: a comparison of CT, MR imaging, and positron emission tomography.

OBJECTIVE: Accurate assessment of lymph node status before treatment is critical in the treatment of gynecologic cancers because the 5-year survival and treatment of women is influenced by lymph node involvement. The aims of this study were to investigate the ability of X-ray CT, MR imaging, and (18)F-FDG positron emission tomography (PET) to detect pelvic lymph node metastases by comparing imaging with histopathologic findings after lymph node dissection. MATERIALS AND METHODS: Eighteen patients with gynecologic cancers were studied by all three imaging methods before surgery. The images were initially reviewed with routine diagnostic conditions and then, subsequently, by two observers who were unaware of the clinical and histopathologic findings of the patients. The nodal sites were split into upper (aortic to common iliac bifurcations) and lower (common iliac bifurcations to inguinal ligament) iliac chains. All observers' results were statistically analyzed with specificity, sensitivity, positive and negative predictive values, Fisher's exact test (individual observers) or chi-square test (combined observers), and Cohen's kappa test. RESULTS: Eight of 18 patients had lymph node metastases at histology. Findings of all three modalities agreed in full in only one patient. CT correctly revealed 10 node-negative patients, whereas MR imaging was correct in eight of these patients. (18)F-FDG PET correctly depicted one patient with lymph nodes negative for tumor. CT was the most specific imaging modality (97.0%), with MR imaging and PET rendering values of 90.7% and 77.3%, respectively, but sensitivity of all modalities was low (CT, 48.1%; MR imaging, 53.7%; PET, 24.5%). Observer agreement for each modality was good; kappa values among all observers were 0.88 for CT, 0.85 for MR imaging, and 0.72 for PET. CONCLUSION: CT is the most specific modality for detecting lymph nodes positive for tumor in gynecologic cancers, whereas MR imaging is the most sensitive. The poor results of PET in the pelvis are attributed to urinary (18)F-FDG in the ureters or bladder, which may mask or imitate lymph node metastases.     

Multidetector CT in pre- and post-operative evaluation of living-related liver transplantation

Objective

To assess the role of multi-detector CT (MDCT) in the pre and post operative evaluation of both potential donors and recipients for living related liver transplantation (LRLT).

Material and Methods

This prospective study included 26 patients for LRLT and their corresponding donors. For preoperative assessment, all subjects were evaluated by triphasic CT abdomen. CT angiography (CTA) with 3D reconstruction and CT volumetry was additionally done for donors. CT findings were compared to surgical results as gold standard reference. In post-operative evaluation, CT abdomen was performed at least once after transplantation for all recipients and for indicated donors. CTA was done for indicated recipients when US findings were inconclusive.

Results

No statistically significant difference was found between CT volumetry and intraoperative findings. Compared to surgical findings, MDCT identified hepatic arterial and portal venous anatomy with 100% sensitivity and specificity, while for hepatic venous anatomy; it showed sensitivity and specificity of 85.7% and 84.2%. Biliary complications and fluid collections were the commonest in recipients and donors respectively.

Conclusion

MDCT is a single comprehensive non-invasive and accurate imaging modality for preoperative evaluation of liver parenchyma, hepatic vascular anatomy and graft volume and postoperative complications in donors and recipients of LRLT.     

Pulmonary artery CTA

The latest with the introduction of multidetector row computed tomography (MDCT), CT has been firmly established as the modality of choice for imaging the pulmonary arteries, particularly as the de facto first line test for imaging patients with suspected acute pulmonary embolism (PE). Before the introduction of MDCT, remaining concerns regarding CTs accuracy for diagnosis of isolated peripheral emboli had prevented the unanimous acceptance of this test as the reference standard for imaging PE. After a decade of uncertainty, there is now conclusive evidence that CT, if positive, provides reliable confirmation of the presence of PE and, more importantly, if negative effectively rules out clinically significant PE. Current endeavors to streamline and facilitate workflow for CT diagnosis of PE will further improve the acceptance, utility, and importance of this test. Examples include improvements in workflow, CT derivation of right ventricular function parameters for triage and prognostication of patients with acute PE and the comprehensive assessment of patients with acute chest pain for PE, coronary disease, aortic disease, and pulmonary disease by means of a single, contrast enhanced, ECG-synchronized CT scan. Although the diagnosis or exclusion of acute PE is the most common and important application of CT pulmonary angiography, the ease of scan acquisition and the high spatial resolution of modern CT techniques make this test ideally suited for the greatest majority of congenital and acquired, acute and chronic disorders of the pulmonary arteries.     

Introduction to cardiac imaging in infants and children: techniques, potential, and role in the imaging work-up of various cardiac malformations and other pediatric heart conditions

The increasing prevalence of congenital heart disease (CHD) can be attributed to major improvements in diagnosis and treatment. Although echocardiography is the most commonly used imaging modality for diagnosis and follow-up of subjects with CHD, the evolution of cardiovascular magnetic resonance (MR) imaging and increasingly computed tomography (CT) does offer new ways to visualize the heart and the great vessels. The development of cardiovascular MR techniques allows for a comprehensive assessment of cardiac anatomy and function. This provides information about the long-term sequlae of the underlying complex anatomy, hemodynamic assessment of residual post-operative lesions and complications of surgery. As much of the functional data in CHD patients is usually acquired with invasive X-ray angiography, non-invasive alternatives such as cardiovascular MR (and CT) are desirable. This review evaluates the role of MR imaging in the management of subjects with CHD, particularly detailing recent developments in imaging techniques as they relate to the various CHD diagnoses we commonly encounter in our practice.