Time-resolved and bolus-chase MR angiography of the leg: branching pattern analysis and identification of septocutaneous perforators

Variations in the Termination of the Popliteal Artery: A Multidetector Computed Tomography Angiography (CTA)-Based Retrospective Study

BACKGROUND

Comprehension of the intrucate anatomy and variations in the termination of the popliteal artery (PA) is increasingly essential for endovascular interventionists, plastic surgeons, vascular surgeons, and orthopedic surgeons, due to the rise in procedures like embolectomy, vascular grafting, free fibular flap surgery, and high-tibial osteotomy. Few studies from India have reported on the variant anatomy of PA termination, and none have used 128-slice tomography. This study aimed to observe the terminal branching pattern of the PA and the morphology of its terminal branches using 128-slice computed tomography angiography (CTA) and to analyze its relation to gender and laterality.

METHODOLOGY

A retrospective review of CTA images of 181 lower extremities from 100 patients (137 males and 44 females), aged five to 75 years, was conducted.

RESULTS

The usual type I-A pattern was found in 75.69% of cases, while 24.31% exhibited variant patterns. Type III was the most common variation observed (19.34%), with type III-A being the most prevalent (11.05%). Types II-B and II-C were not observed. Among 84 bilaterally examined cases, 19.05% had unilateral variations and 15.48% had bilateral variations, with 8.33% showing bilaterally similar variations and 7.14% dissimilar variations. No significant difference in branching patterns was found between genders or sides. The mean length of the tibial-peroneal trunk (TPT) in the type I-A pattern was 3.00 ± 0.99 cm (right side: 3.21 ± 1.02 cm; left side: 2.82 ± 0.93 cm; males: 2.9 ± 1.00 cm; females: 3.37 ± 0.85 cm), with statistically significant differences between sides and genders. In the type II-A pattern, the mean TPT length was 7.16 ± 3.75 cm. An exceptionally long TPT (12.97 cm) was noted in one case of the III-B pattern.

CONCLUSION

There is a high prevalence of variation in the termination pattern of the PA. Knowledge of these variations is crucial for any interventions in this region to avoid postoperative vascular complications and reduce patient suffering.

Nitroglycerin improves the visibility of fibula-free flap perforators on computed tomography angiography in patients with oral or maxillofacial lesion

PURPOSE

To investigate the improvement of image quality and visualization of fibula-free flap (FFF) perforators on computed tomography angiography (CTA) after administration of sublingual nitroglycerin (NTG) tablets.

METHODS

A total of 60 patients with oral or maxillofacial lesions before CTA of the lower extremity were randomly divided into two groups (NTG group and non-NTG group). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR), overall image quality and grading of vessels were evaluated and compared. The lumen diameters of the major arteries and the proximal and distal peroneal perforators were measured. The number of visible perforators in muscular clearance and muscular layer was also counted and compared between the two groups.

RESULTS

The CNR of posterior tibial artery and overall image quality of CTA images in the NTG group was significantly higher than that in the non-NTG group (p < 0.05), although the SNR and CNR of other arteries did not show significant differences (p > 0.05). The lumen diameters of the peroneal artery and its perforators, anterior tibial artery, and posterior tibial artery were significantly larger in the NTG group (p < 0.001), while no significant difference prevailed in the diameter of the popliteal artery between the two groups (p = 0.298). Compared with the non-NTG group, a significant increase in the number of visible perforators was noted in the NTG group (p < 0.001).

CONCLUSIONS

The administration of sublingual NTG in CTA of the lower extremity can improve the image quality and visualization of perforators, which aids to surgeons select the optimum FFF.

Time-of-Flight Angiography in Ultra-High-Field 7 T MRI for the Evaluation of Peroneal Perforator Arteries Before Osseomyocutaneous Flap Surgery

OBJECTIVES

Presurgical identification and morphologic characterization of the peroneal perforator arteries (PPAs) are essential for osseomyocutaneous flap surgery. The aim of this study was to evaluate PPAs using time-of-flight (TOF) angiography in 7 T magnetic resonance imaging in comparison with dual-energy computed tomographic angiography (CTA).

MATERIALS AND METHODS

In this prospective study, TOF angiography and CTA of both lower legs were acquired before flap surgery from 07/2019 to 02/2020. Magnetic resonance imaging was performed using a dedicated 28-channel knee coil with an acquisition time of 9:55 minutes (voxel size: 0.4 × 0.4 × 0.8 mm). Computed tomographic angiography was acquired with a third-generation dual-source computed tomography on the same day. Virtual monoenergetic reconstructions at 40 keV photon energy served as the standard of reference for PPA identification and subtyping. Two independent readers assessed the image quality, quantity, length assessment, and classification according to surgical considerations of PPAs for TOF angiography and CTA. Both TOF angiography and CTA were used for presurgical flap design and were evaluated by an orofacial surgeon.

RESULTS

Ten patients (mean age, 59.9 ± 14.9 years; 7 men) were included. Time-of-flight angiography and CTA identified 53 and 51 PPAs in total, respectively. Time-of-flight angiography showed superior image quality (both readers, P < 0.05). Time-of-flight angiography enabled specific classification of PPA subtypes more often (53 vs 39; P < 0.05), and both readers reported higher diagnostic confidence for TOF angiography than CTA in all patients (interrater agreement κ = 0.8; P < 0.05). Regarding length assessment, PPAs were significantly more conspicuous with TOF angiography (TOF mean , 50 ± 11 mm; CTA mean , 40 ± 9 mm; P = 0.001). In comparison with CTA, TOF angiography prospectively changed the orofacial surgeon's final decision on the presurgical selected PPAs in 60% of cases.

CONCLUSIONS

Presurgical assessment of PPAs is feasible using TOF in 7 T magnetic resonance imaging. Moreover, TOF angiography was superior to CTA for classifying and identifying PPAs, which may facilitate the planning of reconstructive surgery.

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.

Anatomic study of septocutaneous system of the human fetuses' lower leg: peroneal artery

The septocutaneous system of the lower leg perforating blood vessels consists of a vascular basis of fasciocutaneous flaps. This system is of particular importance when designing distally based fasciocutaneous flaps that are the 'workhorse' in reconstructing the distal third of the lower leg and foot. The aim of this study was to provide a comprehensive, clear and conclusive overview of the lower-leg septocutaneous system of skin blood supply in fetal age. Dissection was conducted on 20 fetuses of both sexes and gestational age from 20 to 28 weeks. The focus was on the vascular anatomy of peroneal artery and its septocutaneous (fasciocutaneous) perforating arterial vessels. Cluster analysis was applied to the obtained data. A total of 212 perforating arterial vessels were identified for peroneal artery. The average number of perforating arterial vessels was 5.32 (ranging from 4 to 7). Based on cluster analysis, perforating blood vessels were more likely to be found at certain lower-leg levels ('safe levels of finding perforators'). The presence of septocutaneous system of perforating blood vessels and reliability of their localization even in the fetal period allows for the application of these findings in the lower leg reconstructions in children of early age.

Computed Tomography Angiography (CTA) before Reconstructive Jaw Surgery Using Fibula Free Flap: Retrospective Analysis of Vascular Architecture

Computed tomography angiography (CTA) is widely used in preoperative evaluation of the lower limbs' vascular system for virtual surgical planning (VSP) of fibula free flap (FFF) for jaw reconstruction. The present retrospective clinical study analysed n = 72 computed tomography angiographies (CTA) of lower limbs for virtual surgical planning (VSP) for jaw reconstruction. The purpose of the investigation was to evaluate the morphology of the fibular bone and its vascular supply in CTA imaging, and further, the amount and distribution of periosteal branches (PB) and septo-cutaneous perforators (SCPs) of the fibular artery. A total of 144 lower limbs was assessed (mean age: 58.5 ± 15.3 years; 28 females, 38.9%; 44 males, 61.1%). The vascular system was categorized as regular (type I-A to II-C) in 140 cases (97.2%) regarding the classification by Kim. Absent anterior tibial artery (type III-A, n = 2) and posterior tibial artery (type III-B, n = 2) were detected in the left leg. Stenoses were observed mostly in the fibular artery (n = 11), once in the anterior tibial artery, and twice in the posterior tibial artery. In total, n = 361 periosteal branches (PBs) and n = 231 septo-cutaneous perforators (SCPs) were recorded. While a distribution pattern for PBs was separated into two clusters, a more tripartite distribution pattern for SCPs was found. We conclude that conventional CTA for VSP of free fibula flap (FFF) is capable of imaging and distinguishing SCPs and PBs.

The congenital popliteal vasculature patterns in fibular free flap reconstruction by means of surgical anatomy in cadavers

Fibular free flap (FFF) is frequently used for reconstruction requiring vascularized bone. Thus, understanding its vasculature variation is crucial. This study investigates the popliteal artery branching variations in Thai cadavers and compares them with previous studies. One hundred and sixty-two legs from 81 formalin-embalmed cadavers were dissected. The popliteal artery branching patterns were classified. The previous data retrieved from cadaveric and angiographic studies were also collected and compared with the current study. The most common pattern is type I-A (90.7%). For the variants, type III-A was the majority among variants (6.2%). Type IV-A, hypoplastic peroneal artery, was found in one limb. A symmetrical branching pattern was found in 74 cadavers. Compared with cadaveric studies, type III-B and III-C are significantly common in angiographic studies (p = 0.015 and p = 0.009, respectively). Type I-A is most common according to previous studies. Apart from this, the prevalence of type III-A variant was higher than in previous studies. Furthermore, type III-B and III-C are more frequent in angiographic studies which might be from atherosclerosis. Thus, if the pre-operative CTA policy is not mandatory, the patients at risk for atherosclerosis and population with high variants prevalence should undergo pre-operative CTA with cost-effectiveness consideration.

Reconstruction of soft tissue defects around the Achilles region with distally based extended peroneal artery perforator flap

INTRODUCTION

Achilles tendon rupture and soft tissue infections with wound dehiscence and tendon exposure following the tendon repair are not infrequent. Various procedures have been described for the reconstruction of soft tissue defects at the Achilles tendon region, yet there is lack of consensus on the ideal method. In this article we report our experience using the distally based peroneal artery perforator flap in reconstruction of combined defects of the Achilles tendon and overlying soft tissue.

METHODS

7 patients with Achilles tendon injury and full-thickness soft tissue defects over the Achilles region underwent tendon repair and soft tissue reconstruction with the distally based peroneal artery perforator flap. Perforator vessels were identified at the septum between the peroneus longus and soleus muscles. After choosing the perforator with the largest diameter, meticulous deep dissection of the perforator was performed and completed 6 cm proximal to the lateral malleolus. The peroneal artery was transected and ligated and transposition of the flap to the defect was performed through a subcutaneous tunnel.

RESULTS

The size of the soft tissue defects and flaps ranged between 2×3 cm to 4×10 cm and 4×5 cm to 5×12 cm, respectively. Six out of 7 flaps survived completely without any complications. Post-operative venous congestion was observed in one patient which resulted in partial tip necrosis of the flap. The resulting wound healed with conservative treatment. Donor sites healed uneventfully in all patients. All flaps had excellent contour and provided stable soft tissue coverage.

CONCLUSION

Distally based peroneal artery perforator flap can be considered as a reliable alternative for the reconstruction of soft tissue defects around the Achilles tendon region. Advantages include (1) extended reach of the flap for the defects around the plantar and dorsal aspects of the foot, provided by the perforator dissection, (2) convenience with footwear and walking, provided by the skin texture similarity with the target region, (3) creating a protective surface to allow tendon gliding and prevent tissue adhesions after the tendon repair, provided by the crural fascia included in the flap, (4) obviating the need for microsurgical anastomosis and associated length of the operation.

Magnetic resonance angiography for free fibula harvest: anatomy and perforator mapping

The purpose of this study was to outline lower leg vessel anatomy and to investigate reliability and limitations of magnetic resonance angiography (MRA) in patients proposed for microvascular fibula transplantation (free fibula flap (FFF)). We retrospectively investigated MRAs of 99 patients considered for FFF. Frontal MRA planes and maximal intensity projections (MIPs) were evaluated for fibula lengths, anatomical branching pattern, arterial stenoses and fibular perforator positions in both legs (n=198). Normal branching patterns were observed in 168 (85.3%) legs. Twenty-nine (14.7%) legs presented abnormal branching patterns. Once (0.5%) the anterior, 19 times (9.6%) the posterior tibial artery were absent or hypoplastic. Nine (4.6%) lower legs presented an arteria peronea magna. Average length of the tibiofibular trunk (TFT) was 3.3±0.15cm. A total of 492 perforators were found with an average of 2.5 (±0.82±0.99) perforators per leg. A mapping of perforator run-offs was illustrated true to scale. Lower limb stenoses were distributed in the anterior tibial artery (14.1%), in the posterior tibial artery (11.1%) and in the fibular artery (8.1%). Smoking (P=0.828), diabetes (P=0.727) and peripheral arterial occlusive disease (P=0.172) did not correlate with presence of stenoses. Preoperative lower limb angiography avoids postoperative complications. MRA reliably and non-invasively identifies anatomical variants and arterial stenoses without radiation. Illustration of perforator run-offs enhances incision planning for fibula harvest.

Interperforator Flow Pattern and Clinical Application of Distal Extended Peroneal Artery Perforator Flaps

Introduction

Peroneal artery perforator flaps are the most widely used pedicled flaps for soft tissue defects of the distal lower extremity. Most research regarding peroneal artery flaps focuses on the location, diameter, and number of peroneal artery perforators. However, there is little literature regarding interperforator flow patterns within the peroneal artery perforator flaps. The aims of the present study were to describe interperforator flow patterns of the distally based extended peroneal artery perforator flaps through digital subtraction angiography and review their clinical application.

Methods

Twelve consecutive patients underwent digital subtraction angiography of the lower-limb arteries. The number and classification of peroneal artery perforators and the interperforator flow patterns were observed. Based on these observations, distally based extended peroneal artery perforator flaps were designed to repair nonhealing wounds located on the ankles and feet of 14 patients.

Results

The peroneal artery gives out grades I to IV perforators in the lateral leg. There were 2 to 7 grade I perforators and true anastomoses between adjacent grade II perforators, which generate directly linked vessels in the middle leg. The grade III or IV perforators form a reticular vascular network through a large number of chock and potential anastomoses. All flaps survived and had excellent appearance and texture.

Conclusions

Distally based extended peroneal artery perforator flaps appear reliable for repairing wounds located on or around the ankle and front foot. However, whether the middle perforator or peroneal artery should be used depends on the condition of the anastomosis between direct linking vessels and the distal perforator.

Reference values of vessel diameters, stenosis prevalence, and arterial variations of the lower limb arteries in a male population sample using contrast-enhanced MR angiography

Introduction

Morphological characterization of leg arteries is of significant importance to detect vascular remodeling triggered by atherosclerotic changes. We determined reference values of vessel diameters and assessed prevalence of stenosis and arterial variations of the lower limb arteries in a healthy male population sample.

Methods

Gadolinium-enhanced magnetic resonance angiography at 1.5 Tesla was performed in 756 male participants (median age = 52 years, range = 21–82 years) of the population-based Study of Health in Pomerania. Vessel diameters were measured in 9 predefined segments of the pelvic and leg arteries and 95th percentiles were used for upper reference values of means of left and right side arteries.

Results

Reference values of vascular diameters decreased from proximal to distal arteries: common iliac = 1.18cm; internal iliac = 0.75cm; external iliac = 1.03cm; proximal femoral = 1.02cm; distal femoral = 0.77cm; popliteal = 0.69cm; anterior tibial = 0.42cm; posterior tibial = 0.38cm; fibular = 0.40cm. Body-surface area indexed reference values increased with age in all segments. A number of 53 subjects (7.0%) had at least one stenosis, mainly in the lower leg arteries anterior tibial (n = 28, 3.7%), posterior tibial (n = 18, 2.4%) and fibular (n = 20, 2.6%). The risk of stenosis increased considerably with age (odds ratio = 1.08; p<0.001). The most common arterial variant was type I-A in both legs (n = 620, 82%).

Conclusion

We present reference values for different pelvic and leg artery segment diameters in men that decrease from proximal to distal and increase with age. Stenoses were most prevalent in lower leg arteries and type I-A was the most common variant in the lower leg.

Advantages of time-resolved contrast-enhanced 4D MR angiography in splenic arterial steal syndrome

Splenic artery steal syndrome (SASS) is a severe complication affecting up to 10% of orthotopic liver transplant (OLT) patients. In this case report, we present a 35-year-old male with OLT secondary to liver failure due to hemochromatosis, who developed SASS. We describe potential application of different imaging techniques for diagnosis of SASS with focus on the value of time-resolved contrast enhanced 4D magnetic resonance angiography (MRA).

Comparison of Time-Resolved and First-Pass Contrast-Enhanced MR Angiography in Pretherapeutic Evaluation of Spinal Dural Arteriovenous Fistulas

BACKGROUND AND PURPOSE

Different MRA techniques used to evaluate spinal dural arteriovenous fistulas offer unique advantages and limitations with regards to temporal and spatial resolution. The purpose of this study was to compare the efficacy and interobserver agreement of 2 commonly used contrast-enhanced spinal MRA techniques, multiphase time-resolved MRA and single-phase first-pass MRA, in assessment of spinal dural arteriovenous fistulas.

MATERIALS AND METHODS

Retrospective review of 15 time-resolved and 31 first-pass MRA studies in patients with clinical suspicion of spinal dural arteriovenous fistula was performed by 2 independent, blinded observers. DSA was used as the reference standard to compare the diagnostic performance of the 2 techniques.

RESULTS

There were 10 cases of spinal dural arteriovenous fistula in the time-resolved MRA group and 20 in the first-pass MRA group. Time-resolved MRA detected spinal dural arteriovenous fistulas with sensitivity and specificity of 100% and 80%, respectively, with 100% correct-level localization rate. First-pass MRA detected spinal dural arteriovenous fistulas with sensitivity and specificity of 100% and 82%, respectively, with 87% correct-level localization rate. Interobserver agreement for localization was excellent for both techniques; however, it was higher for time-resolved MRA. In 5 cases, the site of fistula was not included in the FOV, but a prominent intradural radicular vein was observed at the edge of the FOV.

CONCLUSIONS

Multiphase time-resolved MRA and single-phase first-pass MRA were comparable in diagnosis and localization of spinal dural arteriovenous fistulas and demonstrated excellent interobserver agreement, though there were more instances of ambiguity in fistula localization on first-pass MRA.

High spatial resolution time-resolved magnetic resonance angiography of lower extremity tumors at 3T: Comparison with computed tomography angiography

The aim of this study was to compare diagnostic value of high spatial resolution time-resolved magnetic resonance angiography with interleaved stochastic trajectory (TWIST) using Gadobutrol to Computed tomography angiography (CTA) for preoperative evaluation of lower extremity tumors.This prospective study was approved by the institutional review board. Fifty consecutive patients (31 men, 19 women, age range 18-80 years, average age 42.7 years) with lower extremity tumors underwent TWIST magnetic resonance angiography (MRA) and CTA. Digital subtraction angiography was available for 8 patients. Image quality of MRA was compared with CTA by 2 radiologists according to a 4-point Likert scale. Arterial involvement by tumor was compared using kappa test between MRA and CTA. The ability to identify feeding arteries and arterio-venous fistulae (AVF) was compared using Wilcoxon signed rank test and McNemar test, respectively.Image quality of MRA and CTA was rated without a statistically significant difference (3.88 ± 0.37 vs. 3.97 ± 0.16, P = 0.135). Intramodality agreement was high for the identification of arterial invasion (kappa = 0.806 ± 0.073 for Reader 1, kappa = 0.805 ± 0.073 for Reader 2). Readers found AVF in 27 of 50 MRA cases and 14 of 50 CTA cases (P < 0.001). Mean feeding arteries identified with MRA were significantly more than that with CTA (2.08 ± 1.72 vs. 1.62 ± 1.52, P = .02).TWIST MRA is a reliable imaging modality for the assessment of lower extremity tumors. TWIST MRA is comparable to CTA for the identification of AVF and feeding arteries.

Oromandibular reconstruction with chimeric double-skin paddle flap based on peroneal vessel axis for synchronous opposite double oral cancer

BACKGROUND

Synchronous double oral cancer represents the minority of cases of head and neck cancer. After tumor ablation, 2 separate oromandibular defects, even combined with a through-and-through oral defect, pose a serious reconstructive challenge. The ideal method for reconstruction remains controversial.

AIM AND OBJECTIVES

Based on the peroneal vessel axis, a chimeric double-skin paddle peroneal fasciocutaneous or fibular osteomyocutaneous flap could be designed to accomplish the difficult reconstruction.

MATERIALS AND METHODS

Six male patients, each with 2 separate oromandibular defects after tumor ablation of synchronous double oral cancer, received double-skin paddle flap reconstruction with 3 peroneal fasciocutaneous and 3 fibular osteomyocutaneous flaps.

RESULT

All 6 flaps survived; however, complications included 1 skin paddle lost due to insufficient perfusion of a visible perforator, and 1 superficial necrosis occurring over the tip of a longer skin paddle. One postoperative intraoral infection and 1 donor site infection were also reported. During follow-up, 3 months later, 1 patient succumbed to local recurrence and bony metastasis. One patient developed a new cancer in the maxillary gingiva, and another had osteoradionecrosis 8 months later. Four patients gained acceptable cosmesis with good oral competence.

CONCLUSIONS

A chimeric flap based on the peroneal artery could provide a segment of fibular bone, 1 or 2 skin paddles, and a cuff of the flexor hallucis longus muscle simultaneously. For 1-stage reconstruction of separate oromandibular defects after tumor ablation of synchronous double oral cancer, this design could provide all components at 1 transfer.

RETRACTED: The diagnostic value of time-resolved MR angiography with Gadobutrol at 3T for preoperative evaluation of lower extremity tumors: Comparison with computed tomography angiography

Purpose

To evaluate the diagnostic value of time resolved magnetic resonance angiography with interleaved stochastic trajectory (TWIST) using Gadobutrol for preoperative evaluation of lower extremity tumors.

Materials and methods

This prospective study was approved by the local Institutional Review Board. 50 consecutive patients (31 men, 19 women, age range 18–80 years, average age 42.7 years) with lower extremity tumors underwent TWIST and computed tomography angiography (CTA). Image quality of TWIST and CTA were evaluated by two radiologists according to a 4-point scale. The degree of arterial stenosis caused by tumor was assessed using TWSIT and CTA separately, and the intra-modality agreement was determined using a kappa test. The number of feeding arteries identified by TWIST was compared with that by CTA using Wilcoxon signed rank test. The ability to identify arterio-venous fistulae (AVF) were compared using a chi-square test.

Results

Image quality of TWIST and CTA were rated as 3.88 ± 0.37 and 3.97 ± 0.16, without statistically significant difference (P = 0.135). Intra-modality agreement was excellent for the assessment of arterial stenosis (kappa = 0.806 ± 0.073 for Reader 1, kappa = 0.805 ± 0.073 for Reader 2). Readers identified AVF with TWIST in 27 of 50 cases, and identified AVF with CTA in 14 of 50 (P < 0.001). Mean feeding arteries identified with TWIST was significantly more than that with CTA (2.08 ± 1.72 vs 1.62 ± 1.52, P = 0.02).

Conclusion

TWIST is a reliable imaging modality for the assessment of lower extremity tumors. TWIST is comparable to CTA for the identification of AVF and feeding arteries.

Dynamic MR angiography in acute aortic dissection

BACKGROUND

To evaluate the benefit (additional flow information), image quality, and diagnostic accuracy of a dynamic magnetic resonance angiography (MRA) combining high spatial and temporal resolution for the preinterventional assessment of acute aortic dissection.

METHODS

Nineteen patients (12 men, 7 women; aged 32-78 years) with acute aortic dissection underwent contrast-enhanced four-dimensional (4D) MRA and 3D conventional high-resolution MRA (3D MRA) within one examination on a 1.5 Tesla MR system. Both MRA datasets for each patient were evaluated and compared for image quality and visualization of vascular details on a 5-point scale (5 = excellent image quality, 1 = nondiagnostic image quality). In addition, presence and relevance of additional hemodynamic information (flow direction and organ perfusion delay) gained by dynamic MRA were assessed.

RESULTS

Conventional 3D MRA provided significantly higher values for image quality of the aorta and aortic side branches compared with dynamic MRA (aorta: 4.3 versus 3.3; P = 0.006 side branches: 4.2 versus 3.3; P = 0.02). However, in 10 of the 19 patients (53%) the additionally available information on flow dynamics due to dynamic MRA (e.g., delayed perfusion of parenchymal organs) led to a change in therapy planning and realization.

CONCLUSION

Dynamic MRA is a technique that combines functional flow and morphological information. Thus, the combination of 3D and dynamic MRA provides all requested information for treatment planning in patients suffering from acute aortic dissection.

Evaluation of the lower limb vasculature before free fibula flap transfer. A prospective blinded comparison between magnetic resonance angiography and digital subtraction angiography

Introduction The aim of this study was to compare magnetic resonance angiography (MRA) with digital subtraction angiography (DSA) in the preoperative assessment of crural arteries and their skin perforators prior to free fibular transfer. Patients and methods Fifteen consecutive patients, scheduled for free vascularized fibular flap transfer, were subjected to DSA as well as MRA of the crural arteries of both legs (n = 30). All DSA and MRA images were assessed randomly, blindly, and independently by two radiologists. Each of the assessors scored the degree of stenosis of various segments on a 5 point scale from 0 (occlusive) to 4 (no stenosis). The Cohen's Kappa coefficient was used to assess the agreement between DSA and MRA scores. In addition, the number of cutaneous perforators were scored and the assessors were asked if they would advise against fibula harvest and transplantation based on the images. Results A Cohen's Kappa of 0.64, indicating "substantial agreement of stenosis severity scores" was found between the two imaging techniques. The sensitivity of MRA to detect a stenosis compared with DSA was 79% (CI 95%:60-91), and a specificity of 98% (CI 95%: 97-99). In 53 out of 60 assessments, advice on suitability for transfer were equal between DSA and MRA. The median number of cutaneous perforators that perfuse the skin overlying the fibula per leg was one for DSA as well as MRA (P = 0.142).Conclusions A substantial agreement in the assessment of stenosis severity was found between DSA and MRA. The results suggest that MRA is a good alternative to DSA in the preoperative planning of free fibula flap transplantation.

Simultaneous magnetic resonance angiography and perfusion (MRAP) measurement: initial application in lower extremity skeletal muscle

PURPOSE

To obtain a simultaneous 3D magnetic resonance angiography and perfusion (MRAP) using a single acquisition and to demonstrate MRAP in the lower extremities. A time-resolved contrast-enhanced exam was used in MRAP to simultaneously acquire a contrast-enhanced MR angiography (MRA) and dynamic contrast-enhanced (DCE) perfusion, which currently requires separate acquisitions and thus two contrast doses. MRAP can be used to assess large and small vessels in vascular pathologies such as peripheral arterial disease.

MATERIALS AND METHODS

MRAP was performed on 10 volunteers following unilateral plantar flexion exercise (one leg exercised and one rested) on two separate days. Data were acquired after administration of a single dose of contrast agent using an optimized sampling strategy, parallel imaging, and partial-Fourier acquisition to obtain a high spatial resolution, 3D-MRAP frame every 4 seconds. Two radiologists assessed MRAs for image quality, a signal-to-noise ratio (SNR) analysis was performed, and pharmacokinetic modeling yielded perfusion (K(trans) ).

RESULTS

MRA images had high SNR and radiologist-assessed diagnostic quality. Mean K(trans) ± standard error were 0.136 ± 0.009, 0.146 ± 0.012, and 0.191 ± 0.012 min(-1) in the resting tibialis anterior, gastrocnemius, and soleus, respectively, which significantly increased with exercise to 0.291 ± 0.018, 0.270 ± 0.019, and 0.338 ± 0.022 min(-1) . Bland-Altman analysis showed good repeatability.

CONCLUSION

MRAP provides simultaneous high-resolution MRA and quantitative DCE exams to assess large and small vessels with a single contrast dose. Application in skeletal muscle shows quantitative, repeatable perfusion measurements, and the ability to measure physiological differences.

Non-invasive vascular imaging in perforator flap surgery

Preoperative imaging using a range of imaging modalities has become increasingly popular for preoperative planning in plastic surgery, in particular in perforator flap surgery. Modalities in this role include ultrasound (US), magnetic resonance angiography (MRA), and computed tomographic angiography (CTA). The evidence for the use of these techniques has been reported in only a handful of studies. In this paper we conducted a non-systematic review of the literature to establish the role for each of these modalities. The role of state-of-the-art vascular imaging as an application in perforator flap surgery is thus offered.

Time-resolved MR angiography of the legs at 3 T using a low dose of gadolinium: initial experience and contrast dynamics

OBJECTIVE

This article describes our initial clinical experience with time-resolved MR angiography (MRA) of the legs using the time-resolved imaging with stochastic trajectories (TWIST) technique with a half dose of gadolinium.

MATERIALS AND METHODS

Thirty-four patients underwent a TWIST examination of the legs at 3 T. Thirty-three patients also underwent a bolus-chase MRA examination in the same setting. Times elapsed between the start of contrast injection and the appearance of contrast material (t(A)) and peak enhancement of the arteries in the legs (t(B)) were analyzed. The number of patients with examinations affected by venous contamination was determined. The differences in t(A) and t(B) between cases in which venous contamination was present or absent were evaluated using a two-tailed Student t test.

RESULTS

The TWIST technique using a half dose of gadolinium provided diagnostic-quality images of all patients. The mean t(A) was 35.5 ± 8.8 (SD) seconds (range, 17.8-60.4 seconds), and the mean t(B) was 59.1 ± 15.1 seconds (range, 31-98.8 seconds). Venous contamination was observed in bolus-chase MRA images of 52.9% of patients. The relationship between venous contamination and t(A) was not statistically significant (p = 0.13). The incidence of venous contamination was higher in patients with lower values of t(B) (p = 0.01).

CONCLUSION

The described low-dose clinical experience with TWIST and the contrast dynamics information gained from this study could aid radiologists in planning protocols for leg MRA examinations.

Applications of time-resolved MR angiography

OBJECTIVE

The purpose of this essay is to describe the basic principles behind contrast-enhanced time-resolved MR angiography (MRA) performed with the time-resolved imaging with stochastic trajectories technique and to show examples of the versatile applications of this technique in the evaluation of pathologic conditions throughout the body.

CONCLUSION

Time-resolved MR angiography is a versatile technique for vascular imaging throughout the body. It can be used to answer a variety of clinical questions; to acquire diagnostically useful information, even about complicated vascular lesions; and to overcome many of the limitations of bolus-chase contrast-enhanced MR angiography. The technique is particularly useful when the arterial arrival time is uncertain, the patient is freely breathing, or contrast dynamics are critical to a diagnosis.