Imaging of the musculoskeletal system: magnetic resonance imaging,ultrasonography and computed tomography

In the last decade, musculoskeletal imaging has rapidly expanded largely due to the imaging capabilities of magnetic resonance imaging and ultrasound. These modalities have increased the clinical understanding and mechanisms of arthritis and are assuming increasing importance in the diagnosis of arthritis; more recently, they have been used to monitor therapy. This chapter reviews recent imaging studies relevant to rheumatic diseases.     

Vascular imaging with magnetic resonance and computed tomography

Cross-sectional imaging of the cardiovascular system is successfully achieved with computed tomography (CT) and, more recently, magnetic resonance imaging (MRI). Limits of spatial resolution confine the routine application of either device to assessment of larger vessels, such as the aorta, vena cava, and renal veins. The decision to use one modality versus the other is frequently influenced by the clinical status of the patient, as well as the indication for diagnostic imaging. Some of the more common vascular abnormalities are depicted in this article, as imaged by these relatively new and expensive technologies. An explanation of the complex appearance of blood flow on MR is dependent on an understanding of some basic physical principles, such as flow-related enhancement and even-echo rephasing. MRI is presently more suitable than CT for the evaluation of medium-size vessels since the development of effective techniques for magnetic resonance angiography (MRA). Some of the important concepts, along with the terminology of this still-evolving field are presented. The quantification of blood flow by MRI is similarly an area of active research, and may ultimately supplant the existing methods.     

Gd-EOB-DTPA-enhanced magnetic resonance imaging features of hepatic hemangioma compared with enhanced computed tomography

AIM:To clarify features of hepatic hemangiomas on gadolinium-ethoxybenzyl-diethylenetriaminpentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) compared with enhanced computed tomography (CT). METHODS:Twenty-six patients with 61 hepatic hem- angiomas who underwent both Gd-EOB-DTPA-enhanced MRI and enhanced CT were retrospectively reviewed. Hemangioma appearances (presence of peripheral nodular enhancement, central nodular enhancement, diffuse homogenous enhancement, and arterioportal shunt during the arterial phase, fill-in enhancement during the portal venous phase, and prolonged enhancement during the equilibrium phase) on Gd-EOB-DTPA-enhanced MRI and enhanced CT were evaluated.The degree of contrast enhancement at the enhancing portion within the hemangioma was visually assessed using a five-point scale during each phase. For quantitative analysis, the tumor-muscle signal intensity ratio (SIR), the liver-muscle SIR, and the attenuation value of the tumor and liver parenchyma were calculated. The McNemar test and the Wilcoxon's signed rank test were used to assess the significance of differences in the appearances of hemangiomas and in the visual grade of tumor contrast enhancement between Gd-EOB-DTPA-enhanced MRI and enhanced CT. RESULTS:There was no significant difference between Gd-EOB-DTPA-enhanced MRI and enhanced CT in the presence of peripheral nodular enhancement (85% vs 82%), central nodular enhancement (3% vs 3%), diffuse enhancement (11% vs 16%), or arterioportal shunt (23% vs 34%) during arterial phase, or fill-in enhancement (79% vs 80%) during portal venous phase. Prolonged enhancement during equilibrium phase was observed less frequently on Gd-EOB-DTPA-enhanced MRI than on enhanced CT (52% vs 100%, P 0.001). On visual inspection, there was significantly less contrast enhancement of the enhancing portion on Gd-EOB-DTPA-enhanced MRI than on enhanced CT during the arterial (3.94 ± 0.98 vs 4.57 ± 0.64, respectively, P 0.001), portal venous (3.72 ± 0.82 vs 4.36 ± 0.53, respectively, P 0.001), and equilibrium phases (2.01 ± 0.95 vs 4.04 ± 0.51, respectively, P 0.001). In the quantitative analysis, the tumor-muscle SIR and the liver-muscle SIR observed with Gd-EOB-DTPA-enhanced MRI were 0.80 ± 0.24 and 1.28 ± 0.33 precontrast, 1.92 ± 0.58 and 1.57 ± 0.55 during the arterial phase, 1.87 ± 0.44 and 1.73 ± 0.39 during the portal venous phase, 1.63 ± 0.41 and 1.78 ± 0.39 during the equilibrium phase, and 1.10 ± 0.43 and 1.92 ± 0.50 during the hepatobiliary phase, respectively. The attenuation values in the tumor and liver parenchyma observed with enhanced CT were 40.60 ± 8.78 and 53.78 ± 7.37 precontrast, 172.66 ± 73.89 and 92.76 ± 17.92 during the arterial phase, 152.76 ± 35.73 and 120.12 ± 18.02 during the portal venous phase, and 108.74 ± 18.70 and 89.04 ± 7.25 during the equilibrium phase, respectively. Hemangiomas demonstrated peak enhancement during the arterial phase, and both the SIR with Gd-EOB-DTPA-enhanced MRI and the attenuation value with enhanced CT decreased with time. The SIR of hemangiomas was lower than that of liver parenchyma during the equilibrium and hepatobiliary phases on Gd-EOB-DTPA-enhanced MRI. However, the attenuation of hemangiomas after contrast injection was higher than that of liver parenchyma during all phases of enhanced CT. CONCLUSION:Prolonged enhancement during the equilibrium phase was observed less frequently on Gd-EOB-DTPA-enhanced MRI than enhanced CT, which may exacerbate differentiating between hemangiomas and malignant tumors.     

Imaging in early rheumatoid arthritis: roles of magnetic resonance imaging, ultrasonography, conventional radiography and computed tomography

Efficient methods for diagnosis, monitoring and prognostication are essential in early rheumatoid arthritis (RA). While conventional X-rays only visualize the late signs of preceding disease activity, there is evidence for magnetic resonance imaging (MRI) and ultrasonography being highly sensitive for early inflammatory and destructive changes in RA joints, and for MRI findings being sensitive to change and of predictive value for future progressive X-ray damage. Reviewing the data on X-ray, computed tomography, MRI and ultrasonography in RA, this paper discusses current and future roles of these imaging modalities in the management of early RA. The main focus is on recent advances in MRI and ultrasonography. Suggestions on clinical use and research priorities are provided.     

Liver metastases:Contrast-enhanced ultrasound compared with computed tomography and magnetic resonance

The development of ultrasound contrast agents with excellent tolerance and safety profiles has notably improved liver evaluation with ultrasound(US)for several applications,especially for the detection of metastases.In particular,contrast enhanced ultrasonography(CEUS)allows the display of the parenchymal microvasculature,enabling the study and visualization of the enhancement patterns of liver lesions in real time and in a continuous manner in all vascular phases,which is similar to contrast-enhanced computed tomography(CT)and contrast-enhanced magnetic resonance imaging.Clinical studies have reported that the use of a contrast agent enables the visualization of more metastases with significantly improved sensitivity and specificity compared to baseline-US.Furthermore,studies have shown that CEUS yields sensitivities comparable to CT.In this review,we describe the state of the art of CEUS for detecting colorectal liver metastases,the imaging features,the literature reports of metastases in CEUS as well as its technique,its clinical role and its potential applications.Additionally,the updated international consensus panel guidelines are reported in this review with the inherent limitations of this technique and best practice experiences.     

Imaging of liver disease: comparison between quadruple-phase multidetector computed tomography and magnetic resonance imaging

Background and Aim: To compare quadruple‐phase multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) for the assessment of focal and diffuse liver disease. Methods: Quadruple‐phase contrast‐enhanced MDCT and MRI of 37 consecutive patients were retrospectively reviewed by two readers (R1 and R2). In patients with focal liver lesions, the gold standard was histopathology (n = 17) and/or long‐term (>6 months) follow‐up imaging (n = 27) or transarterial chemoembolization (n = 1). Diffuse liver disease was confirmed by histopathology in all patients, when present. Results: Both readers identified 60 focal liver lesions on MDCT and 56 focal liver lesions on MRI. Gold standard diagnoses revealed 48 focal liver lesions in 25 patients. Diagnosis of malignant liver lesions revealed a sensitivity of 88% (R1) and 91% (R2) for MRI; 63% (R1) and 66% (R2) for MDCT; and a specificity of 75% (R1) and 79% (R2) for MRI; 50% (R1) and 64% (R2) for MDCT. MRI was superior to MDCT for the diagnosis of malignant focal liver lesions, when the mean areas under the alternative free‐response receiver operating characteristic curves (A_Z) were compared (MRI = 0.93 vs CT = 0.69), (P < 0.00001). Thirty‐three patients had histopathologically confirmed diffuse liver disease. Overall diagnosis of diffuse liver disease revealed a sensitivity of 88% (R1) and 92% (R2) for MRI; 75% (R1) and 74% (R2) for MDCT; and a specificity of 100% for both modalities by both readers. Conclusions: MRI is superior for the assessment of malignant focal liver lesions and diffuse liver disease compared to quadruple‐phase MDCT, and can be considered as primary diagnostic imaging modality for liver imaging.     

Cardiac magnetic resonance imaging and computed tomography: anatomic fundamentals

Due to lack of appropriate anatomic visualization using fluoroscopy, radiological scans such as computed tomography and magnetic resonance imaging are increasingly used to provide detailed anatomy of cardiac structures. Furthermore, these imaging modalities are now being used to integrate images with other modalities to navigate catheters in real time on the detailed depicted anatomy. This review details the anatomic fundamentals of these modalities.     

Quantitative pulmonary imaging using computed tomography and magnetic resonance imaging

Measurements of lung function, including spirometry and body plethesmography, are easy to perform and are the current clinical standard for assessing disease severity. However, these lung functional techniques do not adequately explain the observed variability in clinical manifestations of disease and offer little insight into the relationship of lung structure and function. Lung imaging and the image-based assessment of lung disease has matured to the extent that it is common for clinical, epidemiologic and genetic investigation to have a component dedicated to image analysis. There are several exciting imaging modalities currently being used for the non-invasive study of lung anatomy and function. In this review, we will focus on two of them; X-ray computed tomography and magnetic resonance imaging. Following a brief introduction of each method, we detail some of the most recent work being done to characterize smoking-related lung disease and the clinical applications of such knowledge.     

Volvulus of the gall bladder diagnosed by ultrasonography, computed tomography, coronal magnetic resonance imaging and magnetic resonance cholangio-pancreatography

A 54-year-old woman was admitted to our hospital with the complaint of right upper quadrant pain. Upon physical examination the vital signs of the patient were within normal ranges. Ultrasonography and computed tomography (CT) examination of the abdomen was obtained, which demonstrated a large dilatated cystic structure, measuring approximately 68.6 mm x 48.6 mm, with marked distension and inflammation. Additionally, the enhanced CT was characterized by the non-enhanced wall of the gallbladder. As the third examination in this study, magnetic resonance imaging (MRI), namely coronal MRI and magnetic resonance cholangio-pancreatography (MRCP), were performed. The MRCP demonstrated a dilatation of the gallbladder but detected no neck of the gallbladder. Simple cholecystectomy was performed. Macroscopic findings included a distended and gangrenous gallbladder, and closer examination revealed a counterclockwise torsion of 360 degrees on the gallbladder mesentery. Coronal MRI and MRCP showing characteristic radiography may be useful in making a definitive diagnosis.     

Imaging of transplanted islets by positron emission tomography,magnetic resonance imaging,and ultrasonography

While islet transplantation is considered a useful therapeutic option for severe diabetes mellitus (DM), the outcome of this treatment remains unsatisfactory. This is largely due to the damage and loss of islets in the early transplant stage. Thus, it is important to monitor the condition of the transplanted islets, so that a treatment can be selected to rescue the islets from damage if needed. Recently, numerous trials have been performed to investigate the efficacy of different imaging modalities for visualizing transplanted islets. Positron emission tomography (PET) and magnetic resonance imaging (MRI) are the most commonly used imaging modalities for this purpose. Some groups, including ours, have also tried to visualize transplanted islets by ultrasonography (US). In this review article, we discuss the recent progress in islet imaging.     

Pulmonary hypertension: role of computed tomography and magnetic resonance imaging.

Multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) have a leading role in the diagnosis and evaluation of pulmonary arterial hypertension. Technical aspects, advantages, limitations and potential contraindications will be considered. MDCT has many advantages: 1) fast examination, 2) good identification of central and peripheral vessels, 3) good characterization of parenchymal findings, and 4) good evaluation of the heart and mediastinal structures. Limitations are: 1) the use of iodinated contrast material, and 2) radiation exposure. MRI allows: 1) cardiac morphological and functional studies, and 2) identification of central pulmonary arteries. Limitations are: 1) long scanning time, 2) poor definition of peripheral arteries, and 3) impossibility of pulmonary evaluation. MDCT and MRI findings allow: 1) quick diagnosis of pulmonary arterial hypertension, 2) differential diagnosis between primary and secondary forms, 3) evaluation of cardiac manifestations, and 4) morphological and functional follow-up studies in surgically treated and untreated patients.     

Cystic pancreatic neoplasms: computed tomography and magnetic resonance imaging findings.

Cystic pancreatic neoplasms include serous cystadenomas (SCA), mucin-producing cystic tumors, cystic islet-cell tumors, and cystic solid and papillary epithelial neoplasms. Imaging techniques are of great value in the demonstration and differential diagnosis of these tumors. In this article we present the computed tomography (CT) and magnetic resonance imaging (MRI) findings of the aforementioned cystic neoplasms. Although the radiological features are in many cases informative, a significant overlap does exist; fine-needle aspiration biopsy and cytology or excisional biopsy and histological examination are necessary to determine a definitive diagnosis.     

Imaging in rheumatoid arthritis – status and recent advances for magnetic resonance imaging, ultrasonography, computed tomography and conventional radiography

Within the field of imaging in RA, large and exciting advances have been made during the last decade. Although X-ray is still the most widely used tool for monitoring disease progression, other methods offer clear advantages through more sensitive depiction of inflammatory and destructive disease manifestations. MRI and US are increasingly used in RA trials and practice. MRI can visualize all the features involved in inflammation and damage in RA patients, and have documented independent prognostic value and superior sensitivity to change compared with conventional methods. US offers sensitive assessment of joint damage and, particularly, inflammation, and can be used by practising rheumatologists as part of the clinical examination. CT provides high-resolution images of erosion, and may have potential for sensitive monitoring of erosive progression.Overall, these new imaging modalities already provide important benefits for the clinician, including: more sensitive detection of early disease manifestations; more sensitive monitoring of responses to therapeutic agents, including improved assessment of whether optimal disease control (remission) has been achieved; and improved prognostication. Many questions concerning the optimal use of these new imaging modalities require further research efforts, but as technical advances are still progressing rapidly, the clinical and research applications of these modern imaging modalities are also expected to increase markedly during the next decade.Imaging could be useful in practice for the following:

A. In routine clinical practice

• to establish a diagnosis of RA (ACR 1987 criteria): X-ray

• to assist with the diagnostic workout in suspected, but not definite, inflammatory joint disease and early, unclassified inflammatory joint disease (by detection of presence/absence of synovitis, enthesitis, bone erosions etc.): MRI, US

• to monitor structural joint damage: X-ray, MRI

• to monitor disease activity: MRI, US

• to assist with the prognostic stratification of patients with early RA: X-ray, MRI

• to help define the presence or absence of true remission: MRI, US

• to guide aspirations and injections in joints, bursae and tendon sheaths: US

B. In research

• to assess structural joint damage in phase III/IV RA trials: X-ray, MRI

• to assess the anti-inflammatory effectiveness of a new compound (‘proof of concept' studies): MRI, US

• for pretrial selection of the patients most likely to progress (‘enrichment'): X-ray, MRI

For the individual imaging modalities, further exploration of:

• clinical value of differential diagnosis in early and in early suspected, but not certain, inflammatory joint disease: MRI, US

• clinical value of monitoring disease activity by imaging: MRI, US

• defining imaging remission and/or an imaging ‘acceptable state’: MRI, US

• clinical value of monitoring joint damage by imaging: MRI, US, CT

• benefit of and optimal methods for using modern imaging in clinical trials: MRI, US, CT

• development and testing of new technical methods: US (e.g. three-dimensional, new transducers), MRI (e.g. 3 Tesla imaging, whole-body MRI), X-ray (e.g. software for automated image interpretation)

Diagnostic imaging for pancreatic cancer: computed tomography, magnetic resonance imaging, and positron emission tomography

Computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) are sophisticated modalities typically used in the second-line diagnosis following routine clinical practice. Among them, CT is regarded as the standard imaging in diagnosing pancreatic cancer at present in Japan due to its popularity and reasonable reliability in wide-ranging diagnostic ability. However, even with multidetector row CT (MDCT), the demonstration of pancreatic cancer less than 1 cm in size remains nearly impossible. CT staging is considered accurate in one-half to two-thirds of patients, but limitations in the imaging of peripancreatic microinvasion and nodal or hepatic micrometastases still have a tendency to underestimate tumor extension. With recent advancement in imaging techniques, MRI has proven to be equal or superior to other imaging modalities in diagnosing pancreatic cancer. Most of all, it is expected that MRCP will become as effective an instrument as ultra-sonography (US) in the screening of pancreatic cancer. Functional imaging with PET using the glucose analog FDG can be used in the diagnosis of pancreatic cancer, but systemic or local disturbance of glucose metabolism may result in an incorrect diagnosis. The usefulness of PET is now considered in assessing tumor viability, monitoring tumor response to treatment, and detecting distant metastases.     

X-ray computed tomography and magnetic resonance imaging of the cardiovascular system

Both electron beam (or ultrafast) x-ray computed tomography and magnetic resonance imaging are developing cardiovascular imaging modalities that can provide high temporal and spatial resolution images of the beating heart and the great vessels in the outpatient setting. The three-dimensional registration of these images has facilitated numerous studies, showing that these devices are capable of quantitating cardiovascular anatomy, function, and blood flow. Continued research employing these methodologies has examined both applications that are complementary to more traditional noninvasive cardiology tools, such as two-dimensional echocardiography and radionuclide and perfusion imaging, as well as applications unique to computed tomography or magnetic resonance imaging. This review discusses progress made in x-ray computed tomography, focusing on the application of electron beam computed tomography and new applications of magnetic resonance imaging within the past 2 years. Specific comments are made regarding these applications, as well as the limitations of both with regard to general clinical applications.