MRI of the Acute Injured Knee

Magnetic Resonance Imaging (MRI) has become a mainstay in the assessment of internal derangement of the knee. MRI prior to surgery increases diagnostic confidence. It also influences clinical practice by identifying alternative diagnoses, e.g., for an osteochondral injury that clinically may mimic meniscal tears, different surgical approaches exist for many cases. This unit presents the standard protocol for imaging injured knees in a clinical setting. The parameters given in this unit are derived from a 1.5 T machine and may need to be altered slightly depending on the main magnetic field strength and the equipment manufacturer.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/145407/1/cpmia2301.pd

Mineralisation patterns in the subchondral bone plate of the humeral head

Purpose: Pathologic changes of the glenohumeral joint, like a long-standing overloading or an accident often lead to severe glenohumeral osteoarthritis, and a glenohumeral joint replacement could be necessary. Joint instability and glenoid loosening are the most common post-operative complications, which can be caused by eccentric loading of the glenoid, if the humeral head is malcentered. If these malcentered cases could be identified pre-operatively, the pathologic position of the humeral head could be fixed intra-operatively and complication may be prevented. Computed tomography osteoabsorptiometry (CT-OAM) is a useful method to determine the distribution of mineralisation in the subchondral bone as a marker for the long-term loading history of a joint. The objective of this study was to gain information about the mineralisation distribution in the subchondral bone plate of the humeral head. Methods: By the use of CT-OAM, the distribution of the subchondral mineralisation of 69 humeral heads was investigated and groups of mineralisation patterns were built. To evaluate if differences in age exist, the mean values of the two groups were compared using t test. Results: 49 humeral heads (71% of 69 specimens) showed bicentric subchondral mineralisation patterns with ventral and dorsal maxima, 20 humeral heads (29% of 69 specimens) could be classified as monocentric with a centro-dorsal maximum. We found no statistical significant difference between the age of the monocentric and the bicentric group on a significance level of 95%. Conclusion: We could show that stress distribution at the humeral head is typically bicentric with a ventral and dorsal maximum. However, other mineralisation patterns may occur under pathologic circumstances. The pre-operative identification of such cases by the use of CT-OAM could help to improve the post-operative results in shoulder surger

MR-guided endovascular interventions: a comprehensive review on techniques and applications

The magnetic resonance (MR) guidance of endovascular interventions is probably one of the greatest challenges of clinical MR research. MR angiography is not only an imaging tool for the vasculature but can also simultaneously depict high tissue contrast, including the differentiation of the vascular wall and perivascular tissues, as well as vascular function. Several hurdles had to be overcome to allow MR guidance for endovascular interventions. MR hardware and sequence design had to be developed to achieve acceptable patient access and to allow real-time or near real-time imaging. The development of interventional devices, both applicable and safe for MR imaging (MRI), was also mandatory. The subject of this review is to summarize the latest developments in real-time MRI hardware, MRI, visualization tools, interventional devices, endovascular tracking techniques, actual applications and safety issue

Use of the modified three-point Dixon technique in obtaining T1-weighted contrast-enhanced fat-saturated images on an open magnet

The purpose of this study was to investigate the modified three-point Dixon technique as a method for obtaining fat-saturated T1-weighted sequences before and after intravenous gadolinium administration using an open MR imaging scanner. A preliminary experiment using an oil/gadolinium phantom was performed on a 0.35-T open magnet and an advanced 1.5-T unit. Fat saturation was achieved at 1.5T using a frequency selective presaturation technique and a modified three-point Dixon technique on the low-field scanner. The modified three-point Dixon sequence was then evaluated in ten patients undergoing MRI examinations of the spine with gadolinium enhancement to determine image characteristics and diagnostic potential. The phantom study demonstrated a homogenous suppression of signal from oil and a good distinction between fat and a gadolinium chelate on the 0.35-T unit comparable to that on the 1.5-T scanner. By applying the modified three-point Dixon technique on the open-magnet, the distinction between fat and gadolinium dimeglumine was rated as very good in 139 and good in 17 axial slices in a total of 156 images. No image was rated as difficult or not possible. Motion artifacts that hampered the reading were detected in the lower cervical spine due to respiratory movement in four (3% of all) images. The modified three-point Dixon technique provides the combination of gadolinium enhancement with fat saturation on an open magnet. Early clinical applications appear promisin

Effects of percutaneous transluminal angioplasty on muscle BOLD-MRI in patients with peripheral arterial occlusive disease: preliminary results

The purpose was to evaluate the effect of percutaneous transluminal angioplasty (PTA) of the superficial femoral artery (SFA) on the blood oxygenation level-dependent (BOLD) signal change in the calf musculature of patients with intermittent claudication. Ten patients (mean age, 63.4 ± 11.6years) with symptomatic peripheral arterial occlusive disease (PAOD) caused by SFA stenoses were investigated before and after PTA. Patients underwent BOLD-MRI 1 day before and 6 weeks after PTA. A T2*-weighted single-shot multi-echo echo-planar MR-imaging technique was applied. The BOLD measurements were acquired at mid-calf level during reactive hyperaemia at 1.5 T. This transient hyperperfusion of the muscle tissue was provoked by suprasystolic cuff compression. Key parameters describing the BOLD signal curve included maximum T2* (T2*max), time-to-peak to reach T2*max (TTP) and T2* end value (EV) after 600 s of hyperemia. Paired t-tests were applied for statistic comparison. Between baseline and post-PTA, T2*max increased from 11.1 ± 3.6% to 12.3 ± 3.8% (p = 0.51), TTP decreased from 48.5 ± 20.8 s to 35.3 ± 11.6s (p = 0.11) and EV decreased from 6.1 ± 6.4% to 5.0 ± 4.2% (p = 0.69). In conclusion, BOLD-MRI reveals changes of the key parameters T2*max, TTP, and EV after successful PTA of the calf muscles during reactive hyperaemi

First Magnetic Resonance Imaging-Guided Aortic Stenting and Cava Filter Placement Using a Polyetheretherketone-Based Magnetic Resonance Imaging-Compatible Guidewire in Swine: Proof of Concept

The purpose of this study was to demonstrate feasibility of percutaneous transluminal aortic stenting and cava filter placement under magnetic resonance imaging (MRI) guidance exclusively using a polyetheretherketone (PEEK)-based MRI-compatible guidewire. Percutaneous transluminal aortic stenting and cava filter placement were performed in 3 domestic swine. Procedures were performed under MRI-guidance in an open-bore 1.5-T scanner. The applied 0.035-inch guidewire has a PEEK core reinforced by fibres, floppy tip, hydrophilic coating, and paramagnetic markings for passive visualization. Through an 11F sheath, the guidewire was advanced into the abdominal (swine 1) or thoracic aorta (swine 2), and the stents were deployed. The guidewire was advanced into the inferior vena cava (swine 3), and the cava filter was deployed. Postmortem autopsy was performed. Procedural success, guidewire visibility, pushability, and stent support were qualitatively assessed by consensus. Procedure times were documented. Guidewire guidance into the abdominal and thoracic aortas and the inferior vena cava was successful. Stent deployments were successful in the abdominal (swine 1) and thoracic (swine 2) segments of the descending aorta. Cava filter positioning and deployment was successful. Autopsy documented good stent and filter positioning. Guidewire visibility through applied markers was rated acceptable for aortic stenting and good for venous filter placement. Steerability, pushability, and device support were good. The PEEK-based guidewire allows either percutaneous MRI-guided aortic stenting in the thoracic and abdominal segments of the descending aorta and filter placement in the inferior vena cava with acceptable to good device visibility and offers good steerability, pushability, and device suppor

Clinical implications of skeletal muscle blood-oxygenation-level-dependent (BOLD) MRI

Blood-oxygenation-level-dependent (BOLD) contrast in magnetic resonance (MR) imaging of skeletal muscle mainly depends on changes of oxygen saturation in the microcirculation. In recent years, an increasing number of studies have evaluated the clinical relevance of skeletal muscle BOLD MR imaging in vascular diseases, such as peripheral arterial occlusive disease, diabetes mellitus, and chronic compartment syndrome. BOLD imaging combines the advantages of MR imaging, i.e., high spatial resolution, no exposure to ionizing radiation, with functional information of local microvascular perfusion. Due to intrinsic contrast provoked via changes in hemoglobin oxygen saturation, it is a safe and easy applicable procedure on standard whole-body MR devices. Therefore, BOLD MR imaging of skeletal muscle is a potential new diagnostic tool in the clinical evaluation of vascular, inflammatory, and muscular pathologies. Our review focuses on the current evidence concerning the use of BOLD MR imaging of skeletal muscle under pathological conditions and highlights ways for future clinical and scientific application

Factors associated with reduced longer-term capacity to work in patients after polytrauma : a Swiss trauma center experience

Knowledge of the factors associated with longer-term reduced capacity to work (RCW) is lacking in patients after polytrauma