Comparison of 2D and 3D quiescent-interval slice-selective non-contrast MR angiography in patients with peripheral artery disease

Comparison of two-dimensional imaging to three-dimensional modeling of intrahepatic portosystemic shunts using computed tomography angiography

Computed tomography angiography (CTA) is used for the diagnosis of intrahepatic portosystemic shunts (IHPSS). When planning for transcatheter intervention, caudal vena cava (CVC) measurements are typically obtained from two-dimensional (2D) imaging to aid in stent selection. We hypothesized that clinically applicable three-dimensional (3D) IHPSS models can be generated, and CVC measurements will not differ between 2D images and 3D models. Computed tomography angiography datasets from client-owned dogs with IHPSS at the University of Georgia Veterinary Teaching Hospital from 2016 to 2022 were analyzed. Materialise Mimics 25.0 and 3-matic 17.0 were used for 3D modeling. Caudal vena cava diameters were measured in 2D dorsal and transverse planes 20 mm cranial and caudal from the shunt ostium and were compared with CVC diameters from 3D models. Length was measured in the 2D dorsal plane between midpoints of each diameter and compared to the 3D model length. Data are presented as mean (SD), and intraclass correlation coefficients were performed. Three-dimensional models were generated for 32 IHPSS (15 right-, 12 left-, and five central-divisional). Two-dimensional dorsal and transverse area-associated diameter measurements were 16.7 mm (5.6) and 15.5 mm (4.2) cranial; 14.9 mm (4.2) and 14.3 mm (3.7) caudal. Three-dimensional area-associated diameter measurements were 15.3 mm (4.4) cranial and 14.0 mm (3.6) caudal. The 2D length was 61.5 mm (7.1) compared with 3D 59.9 mm (7.2). Intraclass correlation coefficients comparing 2D and 3D diameters were all >0.80, indicating very good agreement, with good agreement (>0.60) for length. Clinically applicable 3D IHPSS models can be generated using engineering software. Measurements from 3D models are consistent with 2D planar imaging. Both 2D CTA and 3D virtual models can be utilized for preprocedural planning, depending on clinician preference.

Magnetic Resonance Imaging Techniques in Peripheral Arterial Disease

Significance: Peripheral arterial disease (PAD) leads to a significant burden of morbidity and impaired quality of life globally. Diabetes is a significant risk factor accelerating the development of PAD with an associated increase in the risk of chronic wounds, tissue, and limb loss. Various magnetic resonance imaging (MRI) techniques are being increasingly acknowledged as useful methods of accurately assessing PAD. Recent Advances: Conventionally utilized MRI techniques for assessing macrovascular disease have included contrast enhanced magnetic resonance angiography (MRA), noncontrast time of flight MRA, and phase contrast MRI, but have significant limitations. In recent years, novel noncontrast MRI methods assessing skeletal muscle perfusion and metabolism such as arterial spin labeling (ASL), blood-oxygen-level dependent (BOLD) imaging, and chemical exchange saturation transfer (CEST) have emerged. Critical Issues: Conventional non-MRI (such as ankle-brachial index, arterial duplex ultrasonography, and computed tomographic angiography) and MRI based modalities image the macrovasculature. The underlying mechanisms of PAD that result in clinical manifestations are, however, complex, and imaging modalities that can assess the interaction between impaired blood flow, microvascular tissue perfusion, and muscular metabolism are necessary. Future Directions: Further development and clinical validation of noncontrast MRI methods assessing skeletal muscle perfusion and metabolism, such as ASL, BOLD, CEST, intravoxel incoherent motion microperfusion, and techniques that assess plaque composition, are advancing this field. These modalities can provide useful prognostic data and help in reliable surveillance of outcomes after interventions.

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.

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.