Wilfred C.G. Peh

Artifacts in musculoskeletal MR imaging.

MR imaging has become an important diagnostic tool in the evaluation of a vast number of pathologies and is of foremost importance in the evaluation of spine, joints, and soft tissue structures of the musculoskeletal system. MR imaging is susceptible to various artifacts that may affect the image quality or even simulate pathologies. Some of these artifacts have gained special importance with the use of higher field strength magnets and with the increasing need for MR imaging in postoperative patients, especially those with previous joint replacements or metallic implants. Artifacts may arise from patient motion or could be due to periodic motion, such as vascular and cardiac pulsation. Artifacts could also arise from various protocol errors including saturation, wraparound, truncation, shading, partial volume averaging, and radiofrequency interference artifacts. Susceptibility artifact occurs at interfaces with different magnetic susceptibilities and is of special importance with increasing use of metallic joint replacement prostheses. Magic angle phenomenon is a special type of artifact that occurs in musculoskeletal MR imaging. It is essential to recognize these artifacts and to correct them because they may produce pitfalls in image interpretation.

Dual‐energy CT in gout – A review of current concepts and applications

Dual‐energy computed tomography (DECT) is a relatively recent development in the imaging of gouty arthritis. Its availability and usage have become increasingly widespread in recent years. DECT is a non‐invasive method for the visualisation, characterisation and quantification of monosodium urate crystal deposits which aids the clinician in the early diagnosis, treatment and follow‐up of this condition. This article aims to give an up to date review and summary of existing literature on the role and accuracy of DECT in the imaging of gout. Techniques in image acquisition, processing and interpretation will be discussed along with pitfalls, artefacts and clinical applications.

Variants and pitfalls in MR imaging of the spine.

MR imaging is a valuable tool in investigating the spine and is the diagnostic modality of choice in an increasing number of conditions. Advent of newer 3-T machines has taken MR imaging to a different level, with increased image resolution. Higher field strength magnets have also resulted in an increased number of artifacts. A sound knowledge of human anatomy and awareness of the common anatomical variants is an essential prerequisite in MR imaging of the spine because a variety of normal variants and benign conditions may potentially be confused with serious pathologies. This can significantly affect patient management, and it is essential to avoid such misdiagnoses. Identifying and eliminating the common artifacts on MR imaging can result in a significantly improved image quality. Awareness and knowledge of the common variants, common artifacts, and important distinguishing features among similar-appearing pathologies are important in avoiding the various potential pitfalls in spine imaging.

Variants and Pitfalls in MR Imaging of Foot and Ankle Injuries

Foot and ankle injuries are very common, particularly among young active athletic individuals. MR imaging has become one of the modalities of choice in the assessment of foot and ankle injuries. Accurate interpretation of MR images and diagnosis of pathology requires familiarity with normal anatomical variants and common diagnostic pitfalls. This article describes the common anatomical variants and technical pitfalls in MR imaging of the foot and ankle.

Pictorial Essay: Pitfalls in Magnetic Resonance Imaging of the Shoulder

Numerous imaging pitfalls of normal variants due to imaging technique and artifacts can be seen on routine magnetic resonance imaging of the shoulder. Familiarity with these pitfalls is crucial to avoiding diagnostic errors. Understanding of the common causes of shoulder imaging artifacts will enable the radiologist to make rational changes in imaging technique to eliminate or reduce the effects of artifacts on magnetic resonance images. This pictorial essay highlights possible pitfalls that arise from imaging techniques, imaging artifacts, and normal variations, and how they may be recognized.

Magnetic Resonance Imaging Artifacts

Magnetic resonance imaging (MRI) has become a very important diagnostic tool in imaging a large number of musculoskeletal abnormalities. Technological advances have greatly improved the image quality and diagnostic capabilities, with shorter scanning times. Newer high-field-strength magnets have overcome many previous limitations and even made functional assessment possible. Unfortunately, MRI is still prone to a number of well-recognized artifacts, some of which have gained more importance with newer, high-field-strength machines and increasing use of MRI in postoperative patients. There has been a significant increase in number of joint replacement procedures with resultant increase in the demand for MRI. MRI evaluation can be challenging in these cases, on multiple fronts. Susceptibility artifacts can obscure a large portion of the image, and failure of fat suppression can easily mimic pathology. MRI artifacts can result from poor scanning technique and external factors or even may be related to inherent patient factors. Artifacts can be broadly classified into motion, susceptibility, chemical shift, and protocol error artifacts. Magic angle phenomenon is a unique artifact that is most often seen in the tendons and the ligaments. Hyperintense signal from this artifact can be wrongly interpreted as pathology. A radiologist needs to be aware of these artifacts and the various ways to correct or reduce them, in order to avoid possible misinterpretations.

Imaging of Ankle Impingement Syndromes

Ankle impingement syndromes are a commonly encountered clinical entity seen in athletes, secondary to repetitive forceful microtrauma. Symptoms are related to impingement of osseous or soft tissue abnormalities in the ankle joint, in particular the tibiotalar joint, which may result in painful limitation of ankle movements. Imaging modalities, such as radiographs and magnetic resonance imaging, are very useful in diagnosing osseous and soft tissue abnormalities seen in different types of ankle impingement syndromes. This article reviews the classification of ankle impingement syndromes, their etiology, and clinical and radiological findings.

Variants and pitfalls in MR imaging of shoulder injuries.

Shoulder MR imaging and MR arthrography are frequently used to evaluate shoulder pain and instability and to assess different types of shoulder injuries. We review different normal variants that can mimic pathologic conditions and some pitfalls that may be encountered in image interpretation. A proper knowledge of normal anatomy is necessary to prevent or minimize errors in diagnosing shoulder injuries.

Variants and pitfalls in MR imaging of knee injuries.

MR imaging is an established tool for the detection and diagnosis of various injuries and internal derangements of the knee, enabling excellent anatomical visualization and producing good soft tissue contrast and characterization. However, numerous normal variants and potential pitfalls may lead to diagnostic errors. Understanding the basic MR imaging principles, applying the correct technique, knowing the normal anatomy and variants, recognizing artifacts, and assuring good clinical and radiographic correlation helps avoid these potential pitfalls.

Radiography in Osteoporosis

The pathological changes of osteoporosis are due to resorption of the cortical and trabecular bone. The main radiographic findings include changes in the trabecular pattern, cortical thinning, and decreased bone density which are more prominent in the axial skeleton. Although the most common cause is primary osteoporosis, one has to be aware of the secondary causes as well. Conventional radiography helps in evaluating the secondary causes of osteoporosis, to confirm or rule out fractures and to diagnose concomitant or predisposing conditions. However, radiographs have certain limitations. Radiography only helps in qualitative assessment and cannot be considered as a tool for quantitative assessment. This chapter aims to review the radio-pathological changes and various causes of osteoporosis.