QISS MR Angiography

Evaluation of Lower Leg Arteries and Fibular Perforators before Microsurgical Fibular Transfer Using Noncontrast-Enhanced Quiescent-Interval Slice-Selective (QISS) Magnetic Resonance Angiography

(1) Background: Preoperative imaging of the lower leg arteries is essential for planning fibular grafting. The aim of this study was to evaluate the feasibility and clinical value of non-contrast-enhanced (CE) Quiescent-Interval Slice-Selective (QISS)-magnetic resonance angiography (MRA) for reliably visualizing the anatomy and patency of the lower leg arteries and for preoperatively determining the presence, number, and location of fibular perforators. (2) Methods: The anatomy and stenoses of the lower leg arteries and the presence, number, and location of fibular perforators were determined in fifty patients with oral and maxillofacial tumors. Postoperative outcomes of patients after fibula grafting were correlated with preoperative imaging, demographic, and clinical parameters. (3) Results: A regular three-vessel supply was present in 87% of the 100 legs. QISS-MRA was able to accurately assign the branching pattern in patients with aberrant anatomy. Fibular perforators were found in 87% of legs. More than 94% of the lower leg arteries had no relevant stenoses. Fibular grafting was performed in 50% of patients with a 92% success rate. (4) Conclusions: QISS-MRA has the potential to be used as a preoperative non-CE MRA technique for the diagnosis and detection of anatomic variants of lower leg arteries and their pathologies, as well as for the assessment of fibular perforators.

Clinical Evaluation of Non-Contrast-Enhanced Radial Quiescent-Interval Slice-Selective (QISS) Magnetic Resonance Angiography in Comparison to Contrast-Enhanced Computed Tomography Angiography for the Evaluation of Endoleaks after Abdominal Endovascular Aneurysm Repair

Purpose. Contrast-enhanced (CE) angiographic techniques, such as computed tomographic angiography (CE-CTA), are most commonly used for follow-up imaging after endovascular aneurysm repair. In this study, CE-CTA and non-CE QISS-MRA were compared for the first time for assessing endoleaks and aneurysms at follow-up after abdominal EVAR. Methods. Our study included 20 patients (17 male, median age 79.8 years) who underwent radial QISS-MRA and CE-CTA after EVAR at their first follow-up examination. Two interventional radiologists evaluated datasets from both techniques in each patient concerning presence of endoleaks, types of endoleaks, aneurysm diameter, and image quality. Interobserver and intermodal agreement were assessed with Cohen’s Kappa. Results. Image quality was rated as excellent or good for both modalities by both observers. Ferromagnetic embolization materials cause hyperdense artifacts in CE-CTA causing aneurysm sac diameter measurements to be inaccurate by up to 1 cm. Type 2 endoleaks with low-flow characteristics in CE-CTA were overlooked compared to radial QISS-MRA. Compared to CE-CTA, all endoleaks after abdominal EVAR were detected and classified correctly on QISS-MRA. The interobserver agreement between CE-CTA and QISS-MRA was almost perfect, except for type 2 endoleaks, where agreement was substantial. Intermodal aneurysm diameter correlate “very strongly” for both observers. Conclusions. Radial QISS-MRA is a contrast agent free technique for diagnosing and monitoring all types of endoleaks and aneurysms in patients after abdominal EVAR. It provides information about specific clinical questions concerning aneurysm diameter and presence and types of endoleaks without radiation exposure and the side effects associated with iodine-based contrast agents.

A meta-analysis of the diagnostic performance of quiescent-interval-single-shot magnetic resonance angiography in peripheral arterial disease

OBJECTIVES

To evaluate by meta-analysis the diagnostic accuracy of non-contrast quiescent-interval-single-shot (QISS) magnetic resonance angiography (MRA) in patients with peripheral arterial disease (PAD) using digital subtraction angiography (DSA) or contrast-enhanced magnetic resonance angiography (CE-MRA) as reference standard.

METHODS

This study was performed and reported according to the Preferred Reporting Items for Systematic reviews and Meta-analysis guidelines. A systematic literature search of MEDLINE, Embase and Scopus was done for studies reporting the diagnostic accuracy of QISS in PAD published up to 31 May 2021. The pooled sensitivity, specificity and diagnostic accuracy of QISS were calculated on a per-segment basis for the entire arterial tree.

RESULTS

Seventeen studies including 459 patients were found eligible for the meta-analysis. There was significant heterogeneity among studies as depicted by chi-square test (p = 0.02) and moderate heterogeneity by I² statistic (I²: 69 [95% CI: 30-100]). The pooled sensitivity and specificity of QISS on a per-segment basis with DSA/CE-MRA as reference standard was 0.88 (95% CI: 0.85-0.91) and 0.94 (95% CI: 0.92-0.96) respectively. The area under hierarchical summary receiver-operating characteristic reflected a high accuracy of 0.96 (95% CI: 0.94-0.98). There was a low likelihood of publication bias as indicated by Deeks' funnel plot.

CONCLUSIONS

The present meta-analysis has consolidated the evidence that QISS has high accuracy for identifying as well as excluding arterial stenosis/occlusions in patients with symptoms of PAD. It can thus be considered the test of choice in patients with renal failure and in "at-risk patients" including pregnant women and patients with contrast allergy.

KEY POINTS

• The pooled sensitivity and specificity of QISS magnetic resonance angiography on a per-segment basis with DSA or contrast-enhanced MRA as reference standard are 88% and 94% respectively. • The diagnostic accuracy of QISS in patients with peripheral arterial disease as reflected by area under hierarchical summary receiver-operating characteristic is high (0.96 (95% CI: 0.94-0.98)). • There is moderate to significant heterogeneity among studies as depicted by I² statistic and chi-square test.

Athletic Injuries of the Thoracic Cage

A variety of sports require exposure to high-impact trauma or characteristic repetitive movements that predispose to injuries around the thorax. Appropriate prognostication and timely management are vital, as untreated or undertreated injuries can lead to pain, disability, loss of playing time, or early termination of sports participation. The authors review common athletic injuries of the thoracic cage, encompassing muscular, osseous, and vascular conditions, with an emphasis on mechanism, imaging features, and management. The authors also review pertinent soft-tissue and bony anatomy, along with relevant sports biomechanics. Generalized muscle trauma and more specific injuries involving the pectoralis major, latissimus dorsi, teres major, pectoralis minor, lateral abdominal wall and intercostals, serratus anterior, and rectus abdominis muscles are discussed. Osseous injuries such as stress fractures, sternoclavicular dislocation, costochondral fractures, and scapular fractures are included. Finally, thoracic conditions such as snapping scapula, thoracic outlet syndrome, and Paget-Schroetter syndrome are also described. Specific MRI protocols are highlighted to address imaging challenges such as the variable anatomic orientation of thoracic structures and artifact from breathing motion. Athletes are susceptible to a wide range of musculoskeletal thoracic trauma. An accurate imaging diagnosis of thoracic cage injury and assessment of injury severity allow development of an adequate treatment plan. This can be facilitated by an understanding of functional anatomy, sports biomechanics, and the unique injuries for which athletes are at risk. ^©RSNA, 2021.

Advances in Biomaterials and Technologies for Vascular Embolization

Minimally invasive transcatheter embolization is a common nonsurgical procedure in interventional radiology used for the deliberate occlusion of blood vessels for the treatment of diseased or injured vasculature. A wide variety of embolic agents including metallic coils, calibrated microspheres, and liquids are available for clinical practice. Additionally, advances in biomaterials, such as shape-memory foams, biodegradable polymers, and in situ gelling solutions have led to the development of novel preclinical embolic agents. The aim here is to provide a comprehensive overview of current and emerging technologies in endovascular embolization with respect to devices, materials, mechanisms, and design guidelines. Limitations and challenges in embolic materials are also discussed to promote advancement in the field.