Comparison of contrast-enhanced fundamental imaging, second-harmonic imaging, and pulse-inversion harmonic imaging

RATIONALE AND OBJECTIVES: To investigate the feasibility of recent contrast-specific ultrasound techniques in depicting vascular flow and the effects of changing the output power of the transducer and insonation mode on contrast enhancement, the authors performed an experimental study with a flow phantom. METHODS: While changing the mechanical index and the sound insonation mode (continuous and intermittent), images were obtained with three contrast-enhanced ultrasound techniques: fundamental, second-harmonic, and pulse-inversion harmonic imaging (PIHI) after a bolus injection of microbubble contrast agent. The images were compared on a time-intensity curve. RESULTS: In assessing fixed flow (10 cm/s), PIHI showed the best depiction of flow signal. In intermittent scanning, increases in the mechanical index caused stronger flow signals and longer enhancement duration in all techniques. However, continuous scanning revealed poor depiction of flow signal regardless of the technique or changes in the mechanical index because of significant bubble destruction. CONCLUSIONS: Microbubble-enhanced PIHI with intermittent scanning at a high mechanical index can depict vascular flow highly effectively without shortening the duration of enhancement.     

Medical imaging, PACS, and imaging informatics: retrospective

Historical reviews of PACS (picture archiving and communication system) and imaging informatics development from different points of view have been published in the past (Huang in Euro J Radiol 78:163–176, 2011; Lemke in Euro J Radiol 78:177–183, 2011; Inamura and Jong in Euro J Radiol 78:184–189, 2011). This retrospective attempts to look at the topic from a different angle by identifying certain basic medical imaging inventions in the 1960s and 1970s which had conceptually defined basic components of PACS guiding its course of development in the 1980s and 1990s, as well as subsequent imaging informatics research in the 2000s. In medical imaging, the emphasis was on the innovations at Georgetown University in Washington, DC, in the 1960s and 1970s. During the 1980s and 1990s, research and training support from US government agencies and public and private medical imaging manufacturers became available for training of young talents in biomedical physics and for developing the key components required for PACS development. In the 2000s, computer hardware and software as well as communication networks advanced by leaps and bounds, opening the door for medical imaging informatics to flourish. Because many key components required for the PACS operation were developed by the UCLA PACS Team and its collaborative partners in the 1980s, this presentation is centered on that aspect. During this period, substantial collaborative research efforts by many individual teams in the US and in Japan were highlighted. Credits are due particularly to the Pattern Recognition Laboratory at Georgetown University, and the computed radiography (CR) development at the Fuji Electric Corp. in collaboration with Stanford University in the 1970s; the Image Processing Laboratory at UCLA in the 1980s–1990s; as well as the early PACS development at the Hokkaido University, Sapporo, Japan, in the late 1970s, and film scanner and digital radiography developed by Konishiroku Photo Ind. Co. Ltd. (Konica-Minolta), Japan, in the 1980–1990s. Major support from the US National Institutes of Health and other federal agencies and private medical imaging industry are appreciated. The NATO (North Atlantic Treaty Organization) Advanced Study Institute (ASI) sponsored the International PACS Conference at Evian, France, in 1990, the contents and presentations of which convinced a half dozen high-level US military healthcare personnel, including surgeons and radiologists, that PACS was feasible and would greatly streamline the current military healthcare services. The impact of the post-conference summary by these individuals to their superiors opened the doors for long-term support of PACS development by the US Military Healthcare Services. PACS and imaging informatics have thus emerged as a daily clinical necessity.     

Magnetic resonance imaging of articular cartilage of the knee: comparison between fat-suppressed three-dimensional SPGR imaging, fat-suppressed FSE imaging, and fat-suppressed three-dimensional DEFT imaging, and correlation with arthroscopy

PURPOSE: To compare signal-to-noise ratios (S/N) and contrast-to-noise ratios (C/N) in various MR sequences, including fat-suppressed three-dimensional spoiled gradient-echo (SPGR) imaging, fat-suppressed fast spin echo (FSE) imaging, and fat-suppressed three-dimensional driven equilibrium Fourier transform (DEFT) imaging, and to determine the diagnostic accuracy of these imaging sequences for detecting cartilage lesions in osteoarthritic knees, as compared with arthroscopy. MATERIALS AND METHODS: Two sagittal fat-suppressed FSE images (repetition time [TR] / echo time [TE], 4000/13 [FSE short TE] and 4000/39 [FSE long TE]), sagittal fat-suppressed three-dimensional SPGR images (60/5, 40 degrees flip angle), and sagittal fat-suppressed echo-planar three-dimensional DEFT images (400/21.2) were acquired in 35 knees from 28 patients with osteoarthritis of the knee. The S/N efficiencies (S/Neffs) of cartilage, synovial fluid, muscle, meniscus, bone marrow, and fat tissue, and the C/N efficiencies (C/Neffs) of these structures were calculated. Kappa values, exact agreement, sensitivity, specificity, positive predictive value, and negative predictive value were determined by comparison of MR grading with arthroscopic results. RESULTS: The synovial fluid S/Neff on fat-suppressed FSE short TE images, fat-suppressed FSE long TE images, and fat-suppressed three-dimensional DEFT images showed similar values. Fat-suppressed three-dimensional DEFT images showed the highest fluid-cartilage C/Neff of all sequences. All images showed fair to good agreement with arthroscopy (kappa, 0.615 in FSE short TE, 0.601 in FSE long TE, 0.583 in three-dimensional SPGR, and 0.561 in three-dimensional DEFT). Although the sensitivity of all sequences was high (100% in FSE short TE, FSE long TE, and DEFT; 96.7% in SPGR), specificity was relatively low (67.6% in FSE short TE and FSE long TE; 85.3% in SPGR; 58.3% in DEFT). The peripheral area of bone marrow edema or whole area of bone marrow edema on fat-suppressed FSE images was demonstrated as low or iso-signal intensity on fat-suppressed three-dimensional DEFT images. CONCLUSION: Fat-suppressed three-dimensional SPGR imaging and fat-suppressed FSE imaging showed high sensitivity and high negative predictive values, but relatively low specificity. The Kappa value and exact agreement was the highest on fat-suppressed FSE short TE images. Fat-suppressed three-dimensional DEFT images showed results similar to the conventional sequences.     

Lumbar spine imaging. Normal variants, imaging pitfalls, and artifacts

Accurate recognition and reporting of spine abnormalities on MRI requires knowledge of normal anatomy and its variants. This article deals with common normal variants, points out pitfalls which may be sources of errors in interpretation and describes imaging artifacts which are essential to be recognized and not mistaken for true pathologies.     

Schwannoma of the brachial plexus: cross-sectional imaging diagnosis using CT,sonography, and MR imaging

Primary brachial plexus tumors are rare, usually benign, and in general have a good prognosis after surgical excision. We present a case of a schwannoma in which sonography enabled the correct diagnosis of a probably benign brachial plexus tumor. Key to the diagnosis was the demonstration of a smooth-bordered, longish, and well-defined nodule along a brachial plexus nerve root. Cross-sectional imaging modalities that provide a high degree of soft tissue contrast and spatial resolution, such as sonography and MR imaging, were suitable methods to establish the correct preoperative diagnosis. Findings at CT, sonography, MR imaging, and surgery are discussed.     

MR imaging of the thorax: a comparison of axial, coronal, and sagittal imaging planes

We performed direct multisection coronal and sagittal magnetic resonance (MR) images in addition to axial images to determine the value and limitations of coronal and sagittal planes compared with axial planes. Ninety-four MR examinations of the thorax were performed with a 0.3 T permanent magnet system (Fonar) by spin echo technique. The MR axial images were found superior to coronal in demonstrating prevascular adenopathy (one case), pretracheal nodes (nine cases), left paraaortic nodes (three cases), subcarinal nodes (three cases), and small pleural effusions (three cases). The coronal or sagittal planes were better to determine relationship of a mass at the lung apex (five cases) or an abnormality at the lung base (five cases). The anteroposterior displacement or compromise of great vessels and bronchi was best displayed on the axial plane whereas craniocaudal displacement of above structures was best seen on the coronal plane. The axial images were found most informative and we suggest that they be performed routinely. Coronal or sagittal planes may be added in selected cases.     

Breast imaging, standard of care, and the expert

Many radiologists have the opportunity to serve as experts in determining whether a colleague's actions are within standard of care. This is an important responsibility because, in large part, the fairness and success of the judicial system determining whether medical negligence has occurred is dependent on the opinion of the medical expert. Especially in the field of breast imaging, the physician acting as an expert often has to base opinions on judgments rather than incontestable facts. To make judgments of the highest quality, the expert must possess a clear understanding of the concept of standard of care. This article focuses on the role of experts in malpractice cases dealing with mammography and the delay of diagnosis of breast cancer.     

Postoperative imaging of the elbow, wrist, and hand

There are many bone and soft tissue injuries to the elbow, wrist, and hand that are treated surgically. The operative techniques can be complicated and their indications may change. This article reviews the common injuries at the elbow, wrist, and hand, the indications for surgical management, the current and previous operative techniques used, the expected postoperative appearance on different imaging modalities, and the important potential complications of each technique.     

Single-shot, turbo spin-echo, diffusion-weighted imaging versus spin-echo-planar, diffusion-weighted imaging in the detection of acquired middle ear cholesteatoma

Diagnosis of acquired middle ear cholesteatoma on MR imaging is mostly done on late postgadolinium T1-weighted MR images and/or echo-planar (EPI) diffusion-weighted (DWI) MR images. We describe the appearance of a case of a complicated attical middle ear cholesteatoma on single-shot (SS) turbo spin-echo (TSE) DWI compared with EPI-DWI. This case suggests a higher reliability of SS TSE-DWI in the diagnosis of acquired middle ear cholesteatoma.     

Integrated stereotaxic imaging with CT, MR imaging, and digital subtraction angiography

A stereotaxic frame, compatible with digital subtraction angiography, computed tomography, and magnetic resonance imaging, is described along with a set of software programs that run in an independent imaging computer system, as well as in the computers associated with each modality. Plexiglas plates fastened to the sides of the frame contain fiducial markers that can be recognized in the images and from which the section position and in-plane coordinates of any point in the image relative to the frame may be determined. Coordinate measurements of isolated point targets may be made to an accuracy of better than +/- 1 mm within a 15-cm field of view in the plane of the section or projection on all modalities. The stereotaxic system is of sufficiently high accuracy to be used on a routine clinical basis with one or more of the above modalities.     

Gadolinium-enhanced MR imaging, T2-weighted MR imaging, and transurethral ultrasonography

PURPOSE: To assess the value and problems of dynamic gadolinium-enhanced MR imaging, T2-weighted MR imaging, and transurethral ultrasonography(TUUS) in staging of urinary bladder cancer. MATERIALS AND METHODS: Dynamic gadolinium-enhanced MR imaging and FSE T2-weighted MR imaging of 64 patients with urinary bladder cancer who subsequently had surgery were retrospectively reviewed and compared with TUUS findings. RESULTS: Specificity for muscular invasion was 90.5% with TUUS, significantly better than with dynamic MR imaging (64.9%) (p < 0.05). The rates of overestimation of superficial cancer(pT1) with dynamic MRI and T2-weighted MR imaging were 35.1%(13/37) and 24.3%(9/37), respectively. The staging accuracy of invasive cancer(pT2 or over) was 85.2% with dynamic MR imaging, which was better than the rate of 75.0% achieved with T2-weighted MR imaging. CONCLUSION: Although TUUS was a better modality for diagnosing superficial cancer(pT1), dynamic MR imaging was found to be better for diagnosing invasive(pT2 or over) cancer.     

Artifacts, normal variants, and imaging pitfalls of musculoskeletal magnetic resonance imaging

This article is an early attempt to catalogue some of the many artifacts, normal variants, and imaging pitfalls that the authors have seen in musculoskeletal MRI. The study of such phenomena is potentially very rewarding and may help to prevent some cases of misdiagnosis with MRI.     

Classification, diagnostic imaging, and imaging characterization of a lumbar herniated disk

The absence of universal nomenclature standardization with respect to the definition of a disk herniation and its different categories, especially regarding type and location, is still a major problem that will only be overcome when major national or international scientific societies join efforts to support a particular scheme. Meanwhile, it is important to realize that the two models that are currently most used are based on a different [figure: see text] perspective. Trying to straddle the two by opposing, for instance, bulging disk and herniation is doomed to failure because this exercise defies formal logic. MR imaging is currently the most accurate noninvasive imaging modality to diagnose a disk herniation and to determine its exact location. The determination of some pathoanatomic characteristics of herniated disks (type and composition) may require the use of CT, diskography, or CT diskography.     

Tyrosinemia: computed tomography, magnetic resonance imaging, diffusion magnetic resonance imaging, and proton spectroscopy findings in the brain

In a 5-month-old boy with tyrosinemia, computed tomography revealed diffuse hypodensity in the centrum semiovale. Magnetic resonance (MR) imaging revealed partial signal differences in the white matter and perirolandic regions, and the posterior limbs of the internal capsules revealed higher signal compared with the remainder of the white matter. There were high-signal changes (restricted water diffusion) in the corresponding regions on images of diffusion-weighted MR imaging (b = 1000 s/mm). This likely represented the presence of intramyelinic edema attributable to status spongiosus. Proton MR spectroscopy (repetition time = 1500 milliseconds, echo time = 40 milliseconds) from the lesion sites revealed 2 separate prominent peaks spread between 3.4 and 3.9 ppm. These peaks could represent the CH and CH2 aliphatic protons of the tyrosine molecule.     

Cardiac imaging: Part 1, MR pulse sequences, imaging planes, and basic anatomy

OBJECTIVE: MRI is a well-established modality for evaluating congenital and acquired cardiac diseases. This article reviews the latest pulse sequences used for cardiac MRI. In addition, the standard cardiac imaging planes and corresponding anatomy are described and illustrated. CONCLUSION: Familiarity with the basic pulse sequences, imaging planes, and anatomy pertaining to cardiac MRI is essential to formulate optimal protocols and interpretations.     

Imaging the pleura: sonography, CT, and MR imaging

A variety of imaging techniques can be used to evaluate the pleura and the pleural space. Standard radiographs are the most common. In this article, however, we review the use of three other imaging techniques: sonography, CT, and MR imaging. Sonography allows easy identification of pleural fluid and loculation and differentiation from pleural masses; CT is best for characterizing location and composition of pleural masses; MR is somewhat limited, but is best for imaging superior sulcus carcinoma.