MR cholangiopancreatography using HASTE sequences

Imaging of Soft-Tissue Musculoskeletal Masses: Fundamental Concepts

Radiologic evaluation of musculoskeletal soft-tissue masses has changed dramatically with the continued improvements in imaging technology. The integration of advanced imaging has provided the radiologist with a wide range of assessment tools, but as with all powerful arsenals, selection and application of the appropriate imaging method can be problematic. Although the choices available for imaging evaluation of musculoskeletal masses have changed dramatically, the basic objectives of this assessment have remained constant: diagnosis and staging. The basic principles for evaluating musculoskeletal soft-tissue masses and achieving these objectives have not changed. This article addresses application of the current imaging methods to assessment of soft-tissue musculoskeletal masses, emphasizing fundamental concepts. We do not intend to provide a comprehensive review of imaging techniques, but rather to provide a useful review of the concepts needed to select the appropriate initial imaging method, magnetic resonance (MR) imaging field of view, MR imaging sequences, contrast material requirements, and rapid image acquisition techniques. We also address use of the new quantitative techniques of chemical shift and diffusion-weighted imaging. Finally, we review the current uses of computed tomography and ultrasonography. Although the choices available for imaging evaluation of musculoskeletal masses have changed dramatically within the past decade, appropriate application of the fundamental concepts of imaging will maximize the diagnostic utility of imaging examinations. ^©RSNA, 2016.

Accuracy of ultrasonography in the diagnosis of acute calculous cholecystitis: review of the literature

Background

To evaluate the accuracy of ultrasonography in the diagnosis of acute calculous cholecystitis in comparison with other imaging modalities.

Methods

The authors performed a search of the Medline/ PubMed (National Library of Medicine, Bethesda, Maryland) for original research and review publications examining the accuracy of ultrasonography in the diagnosis of acute calculous cholecystitis. The search design utilized a single or combination of the following terms : (1) acute cholecystitis, (2) ultrasonography, (3) computed tomography, (4) magnetic resonance cholangiopancreatography and (5) cholescintigraphy. This review was restricted to human studies and to English-language literature. Four authors reviewed all the titles and subsequent the abstract of 198 articles that appeared appropriate. Other articles were recognized by reviewing the reference lists of significant papers. Finally, the full text of 31 papers was reviewed.

Results

Sonography is still used as the initial imaging technique for evaluating patients with suspected acute calculous cholecystitis because of its high sensitivity at the detection of GB stones, its real-time character, and its speed and portability. Cholescintigraphy still has the highest sensitivity and specificity in patients who are suspected of having acute cholecystitis. However, due to a combination of reasons including logistic drawbacks, broad imaging capability and clinician referral pattern the use of cholescintigraphy is limited in clinical practice. CT is particularly useful for evaluating the many complications of acute calculous cholecystitis. The lack of widespread availability of MRI and the relatively high cost prohibits its primary use in patients with acute calculous cholecystitis.

Conclusions

US is currently considered the preferred initial imaging technique for patients who are clinically suspected of having acute calculous cholecystitis.

Usefulness of a half-fourier acquisition single-shot turbo spin-echo pulse sequence in identifying arachnoid diverticula in dogs

Single-shot turbo spin-echo sequences are heavily T2-weighted sequences that are exceptionally well suited to evaluate the subarachnoid space. In the T2-weighted fast spin-echo sequences that are used routinely in spinal magnetic resonance (MR) imaging, the subarachnoid space is not well differentiated from the surrounding epidural fat, which could lead to decreased detection of lesions of the subarachnoid space such as arachnoid diverticula. Our purpose was to determine the added value of a single-shot turbo spin-echo sequence in identifying cystic lesions of the subarachnoid space in dogs. MR images of six dogs with a confirmed arachnoid diverticulum and 24 dogs with other spinal disease were included. Six observers were asked to interpret only T2-weighted images initially, and in a second session, T2-weighted and half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences. The MR images were anonymized, and no signalment, history, or clinical information was provided. Without the HASTE sequences, 25% of arachnoid diverticula were identified. Adding the HASTE sequence increased the diagnosis of arachnoid diverticulum to 52.8%. The resulting difference, after adding the HASTE sequence, of 27.8% was statistically significant (P = 0.002). No false-positive diagnoses of arachnoid diverticulum were made with either sequence. Although sensitivity in this study was likely artificially low, the significantly increased detection rate of arachnoid diverticula when using HASTE imaging indicates that this sequence is a valuable addition to MR imaging protocols for the canine spine.

Computed tomography and magnetic resonance cholangiography

In patients with biliary obstruction, determining the level and the cause of the obstruction is essential because it can be a key factor for the next step in diagnostic or therapeutic intervention. Noninvasive cholangiography, such as computed tomography (CT) cholangiography or magnetic resonance (MR) cholangiography, allows the diagnosis of cause and level of biliary disease with minimal risk. Traditional magnetic resonance cholangiopancreatography (MRCP) is an established and effective noninvasive diagnostic modality particularly for extrahepatic biliary tract evaluation. Intrahepatic biliary duct evaluation and functional MR, including evaluating for leaks and gallbladder dyskinesia and outlet obstruction, are evolving diagnostic techniques that show promising results. CT cholangiography techniques are especially useful when MRI is not available or contraindicated or when the quality of MRCP images is suboptimal. CT cholangiography is particularly useful as an adjunct to surgery or postsurgical cases. The primary limitation of cholangiographic contrast-enhanced CT cholangiography (the most prevalent type of CT cholangiography) is its hindrance by poor liver function and/or high-grade biliary obstruction. In this setting MRCP is clearly superior. There are different types of CT cholangiography and MRCP. This article discusses the types of CT cholangiography and MRCP techniques and their clinical applications.

MR Imaging of the Gallbladder and Biliary System

MR imaging is an established technique for the diagnosis of a spectrum of biliary and gallbladder pathologies and continues to improve with the advent of technologic advances, including new contrast agents and new sequences that are capable of improving upon the contrast resolution and signal-to-noise that are afforded by conventional MR imaging. These improvements already have shown promise for the increasing role of MRC as the initial modality in assessing living liver donors and evaluating post-operative hepato-biliary complications. Improved spatial resolution and the added functional or physiologic information afforded by MR imaging promise ever expanding clinical applicability and usefulness.

Does intravenous glucagon improve common bile duct visualisation during magnetic resonance cholangiopancreatography? Results in 42 patients

INTRODUCTION

Magnetic resonance cholangiopancreatography (MRCP) has been demonstrated as a reliable, non-invasive means of biliary tract imaging among patients with suspected choledocholithiasis. The aim of this study was to establish the impact of intravenous glucagon administration (IVGA) upon visualisation of the common bile duct (CBD) and ampulla of Vater during MRCP.

MATERIALS AND METHODS

Forty-two consecutive, non-diabetic subjects with a working diagnosis of symptomatic choledocholithiasis were scanned, pre- and post-IVGA using the half-Fourier, single shot, turbo-spin-echo (HASTE) sequence. Maximum intensity projections (optimised for the extra-hepatic biliary tree and ampulla of Vater) were reviewed blindly by three consultant radiologists. The CBD images were graded (0-3) according to the length of duct seen. The ampullary images were graded according to whether to it was visualised clearly (1), or not (0).

RESULTS

Following IVGA the CBD was visualised at grade 3 (75-100% of length seen) in 14 additional patients compared with images prior to IVGA. Furthermore, ampullary visualisation was considered diagnostic in 18 additional patients post-IVGA. No glucagon-associated adverse effects were observed.

CONCLUSION

These results demonstrate that IVGA improved visualisation of the CBD and ampulla of Vater during magnetic resonance cholangiopanctreatography. This may reduce the requirement for repeat investigation or recourse to invasive diagnostic procedures (e.g. endoscopic retrograde cholangiopancreatography (ERCP)).

The utility of MRCP in preoperative mapping of biliary anatomy in adult-to-adult living related liver transplant donors

PURPOSE

To assess the utility of magnetic resonance cholangiopancreatography (MRCP) in preoperative mapping of biliary anatomy in adult-to-adult living related liver transplant (LRLT) donors.

MATERIALS AND METHODS

From 57 potential donors with preoperative MRCP, 27 cases (16 men, 11 women, age range 22-51 years, mean 37.2 years) underwent right lobe resection and had intraoperative cholangiography (IOC) for comparison. The MRCP and IOC reports were retrospectively reviewed in all 27 cases. The MRCP was performed on 1.5 Tesla MR magnets using breath-hold heavily T2-weighted sequences in axial/coronal thin sections, and variable-thickness rotating slabs. The accuracy of preoperative MRCP for biliary mapping in potential LRLT donors was analyzed compared to the IOC findings.

RESULTS

Of 27 donors, 26 (96.3%) had MRCP which showed adequate information of central intrahepatic biliary anatomy. Of these, 19 had normal bifurcation confirmed by IOC, and single biliary anastomosis was created in the recipient at transplantation. MRCP correctly predicted 17 of 19 normal cases (sensitivity for normals: 89.5%). In seven donors with variant biliary anatomy, two separate biliary anastomoses were performed in the recipient. MRCP correctly predicted five of seven variants (sensitivity for variants: 71.4%). Overall, MRCP had an accuracy 84.6% (22/26).

CONCLUSIONS

MRCP has potential in the preoperative assessment of nondilated bile ducts in LRLT donors, however further improvements are desired to increase its quality and accuracy.

MR imaging of the pancreas

Current MR imaging technology offers the surgeon diagnostic information about pancreatic diseases. This article reviews the basics of MR imaging formation and the rationale for the different types of imaging sequences that comprise a comprehensive pancreaticobiliary examination. Clinical examples include evaluation of pancreatic neoplasms, acute and chronic pancreatitis, and congenital abnormalities.