Aortoiliac and lower extremity arteries: comparison of three-dimensional dynamic contrast-enhanced subtraction MR angiography and conventional angiography

Time-Resolved Contrast-Enhanced Magnetic Resonance Angiography of the Lower Extremity

The aim of this prospective study was to evaluate the feasibility and clinical use of time-resolved magnetic resonance angiography (MRA) of the lower extremity compared to intraarterial digital subtraction angiography (IA-DSA). Twenty-two patients suffering from peripheral arterial occlusive disease underwent MRA and IA-DSA. MRA examinations were performed on a 1.5 T system equipped with a 4-element-array coil. The area from the distal abdominal aorta to the distal lower limb was covered by 2-3 examination steps. A T1-weighted gradient echo sequence with a temporal resolution of 7-10 s was used. Single-dose contrast material (0.1 mm/kg) was injected with a flow rate of 2 mL/s, followed by a 40 mL saline flush. Pre and post contrast images were subtracted, and the subtracted data set was postprocessed with maximum intensity projection (MIP). In all patients diagnostic images could be obtained. Problems with venous overlay or incomplete arterial filling were not present. Sensitivity for the detection of relevant stenoses (>50%) was 96.7%, specificity was 97%. Concerning the detection of occlusions, sensitivity was 97.8%, specificity was 99.2%. Time-resolved contrast-enhanced MRA of the lower extremity is a robust procedure with high accuracy in the detection of relevant stenoses and occlusions.

Posttraumatic pseudoaneurysm of medial plantar artery in a child: treatment with percutaneous thrombin injection

Pseudoaneurysms of the medial plantar artery are rare. The authors describe a case of a pseudoaneurysm of the medial plantar artery of a child who had suffered a penetrating laceration injury. Diagnosis can be confirmed using Doppler ultrasound and magnetic resonance angiography. As an alternative to the conventional surgery technique, percutaneous Doppler ultrasound-guided thrombin injection is a safe and effective treatment.

[Importance of donor site vascular imaging in free fibula flap reconstruction]

INTRODUCTION

Free fibula flap is widely used in head and neck reconstruction. Imaging studies of the donor site can reveal vascular abnormalities and therefore prevent acute leg ischemia.

AIM

Evaluation of the role of donor site vascular imaging studies for free fibula flap planing.

MATERIAL AND METHODS

Out of 35 free flap reconstructions performed in Otolaryngology Head and Neck Surgery Department in Medical University in Lublin in 2011-2012, there were 10 fibula flaps. Each patient had preoperative lower leg subtraction angiography performed.

RESULTS

Lower leg angiography revealed vascular abnormalities in two out of 10 patients scheduled for free fibula flap transfer. One had dominant peroneal artery and second occlusion of anterior tibial artery. In both cases fibula was harvested from the other leg.

CONCLUSIONS

Imaging studies reveal lower leg vascular abnormalities in 20% of cases thus facilitate surgical plans alternations and prevent serious complications in free fibula flap patients.

Dual-Source CT Angiography of Peripheral Arterial Stents: In Vitro Evaluation of 22 Different Stent Types

Purpose. To test different peripheral arterial stents using four image reconstruction approaches with respect to lumen visualization, lumen attenuation and image noise in dual-source multidetector row CT (DSCT) in vitro. Methods and Materials. 22 stents (nitinol, steel, cobalt-alloy, tantalum, platinum alloy) were examined in a vessel phantom. All stents were imaged in axial orientation with standard parameters. Image reconstructions were obtained with four different convolution kernels. To evaluate visualization characteristics of the stent, the lumen diameter, intraluminal density and noise were measured. Results. The mean percentage of the visible stent lumen diameter from the nominal stent diameter was 74.5% ± 5.7 for the medium-sharp kernel, 72.8% ± 6.4 for the medium, 70.8% ± 6.4 for the medium-smooth and 67.6% ± 6.6 for the smooth kernel. Mean values of lumen attenuation were 299.7HU ± 127 (medium-sharp), 273.9HU ± 68 (medium), 270.7HU ± 53 (medium-smooth) and 265.8HU ± 43. Mean image noise was: 54.6 ± 6.3, 20.5 ± 1.7, 16.3 ± 1.7, 14.0 ± 2 respectively. Conclusion. Visible stent lumen diameter varies depending on stent type and scan parameters. Lumen diameter visibility increases with the sharpness of the reconstruction kernel. Smoother kernels provide more realistic density measurements inside the stent lumen and less image noise.

Graph-matching-based computed tomography angiography in peripheral arterial occlusive disease

The objective of this study is to compare a graph-matching-based software and a conventional tool for postprocessing of computed tomography angiography (CTA) in correlation with the gold standard digital subtraction angiography. Sensitivity, specificity, accuracy, and interobserver agreement increased from 80.3% to 92.9%, from 69.1% to 92.4%, from 73.5% to 92.8%, and from 0.45 to 0.96, respectively, using the graph-matching-based technique. Graph-matching-based CTA increases sensitivity, specificity, accuracy, and interobserver agreement in comparison to a conventional bone elimination tool in the assessment of peripheral arterial occlusive disease.

Traumatic Lateral Plantar Artery Pseudoaneurysm and the Use of Time-Resolved MR Angiography

Vascular injury resulting in pseudoaneurysm formation in the plantar aspect of the foot is an uncommon injury after trauma. Such injuries are more often reported in the lateral plantar artery rather than the medial plantar artery, most likely because of its more superficial location. Traditional modalities in diagnosis have included ultrasound and digital subtraction angiography. We present a case of traumatic pseudoaneurysm of the lateral plantar artery following a foot laceration. Diagnosis was made by the use of high-resolution, time-resolved contrast-enhanced 3D magnetic resonance angiography, also referred to as "TRICKS" (time-resolved imaging of contrast kinetics). This technique provided high spatial resolution for the arterial anatomy as well as temporal resolution which allowed better delineation of the hemodynamic characteristics of the pseudoaneurysm.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (doi:10.1007/s11420-010-9170-3) contains supplementary material, which is available to authorized users.

MR Angiography of Peripheral Arterial Stents: In Vitro Evaluation of 22 Different Stent Types

Purpose. To evaluate stent lumen visibility of a large sample of different peripheral arterial (iliac, renal, carotid) stents using magnetic resonance angiography in vitro. Materials and Methods. 21 different stents and one stentgraft (10 nitinol, 7 316L, 2 tantalum, 1 cobalt superalloy, 1 PET + cobalt superalloy, and 1 platinum alloy) were examined in a vessel phantom (vessel diameters ranging from 5 to 13 mm) filled with a solution of Gd-DTPA. Stents were imaged at 1.5 Tesla using a T1-weighted 3D spoiled gradient-echo sequence. Image analysis was performed measuring three categories: Signal intensity in the stent lumen, lumen visibility of the stented lumen, and homogeneity of the stented lumen. The results were classified using a 3-point scale (good, intermediate, and poor results). Results. 7 stents showed good MR lumen visibility (4x nitinol, 2x tantalum, and 1x cobalt superalloy). 9 stents showed intermediate results (5x nitinol, 2x 316L, 1x PET + cobalt superalloy, and 1x platinum alloy) and 6 stents showed poor results (1x nitinol, and 5x 316L). Conclusion. Stent lumen visibility varies depending on the stent material and type. Some products show good lumen visibility which may allow the detection of stenoses inside the lumen, while other products cause artifacts which prevent reliable evaluation of the stent lumen with this technique.

Time-resolved lower extremity MRA with temporal interpolation and stochastic spiral trajectories: preliminary clinical experience

PURPOSE

To assess added value of a new time-resolved technique with temporal interpolation and stochastic spiral trajectory through k-space and parallel imaging (TR-MRA) to conventional bolus chase MRA (BC-MRA) for infragenual peripheral artery evaluation.

MATERIALS AND METHODS

An institutional review board-approved retrospective review of peripheral arterial disease patients was performed. Infragenual TR-MRA and BC-MRA were performed in 26 patients over four months. Two readers individually assessed image quality, diagnostic confidence, and stenosis severity and length in 13 defined below knee segments, first with BC-MRA alone, and then with a combined BC-MRA and TR-MRA reading (BC+TR-MRA). Perceived contribution of TR-MRA was rated by each reader. The reference standard was a consensus reading of both sequences. Catheter angiographic (CA) correlation was available in 6 patients.

RESULTS

A total of 646 infragenual segments in 51 extremities were evaluated. Image quality and diagnostic confidence were superior for BC+TR-MRA compared with BC-MRA alone (P < 0.001). Adding TR-MRA improved sensitivity (85.7% versus 80.7%; P < 0.05) and diagnostic accuracy (88.1% versus 85.4%; P < 0.05) for hemodynamically significant stenosis. Venous contamination (0% versus 13.1% segments) and motion (0.9% versus 8.0%) were decreased for BC+TR-MRA versus BC-MRA alone, P < 0.01. For BC+TR-MRA, TR-MRA was rated more useful than BC-MRA in 30/51 legs (58.8%). TR-MRA identified retrograde flow in 5 segments. Where available, there was high concordance between CA and BC+TR-MRA (91.6%) for stenosis.

CONCLUSION

Adding TR-MRA with temporal interpolation and stochastic spiral trajectories to bolus chase MRA improves image quality, diagnostic confidence and accuracy. It provides hemodynamic information and minimizes venous contamination and patient motion.

Magnetic resonance angiography: current status in the planning and follow-up of endovascular treatment in lower-limb arterial disease

Magnetic resonance angiography (MRA) has become an established imaging modality in the management of lower-limb arterial disease, with emerging roles in treatment planning and follow-up. Contrast-enhanced MRA is now the most widely used technique with clinically acceptable results in the majority of patients. Difficulties in imaging and image interpretation are recognised in certain subgroups, including patients with critical limb ischaemia as well as patients with stents. Although newer contrast agents and refined imaging protocols may offer some solutions to these problems, this optimism is balanced by concerns about the toxicity of certain gadolinium chelates. Further development of interventional MRA remains one of the most significant challenges in the development of magnetic resonance imaging-guided peripheral vascular intervention. The status of MRA in managing patients with lower-limb arterial disease in current clinical practice is reviewed.

Limitations of and Lessons Learned from Clinical Experience of 1,020 Duplex Arteriography

Objective: Due to the inherent risks, deficiencies and cost associated with contrast arteriography (CA), our group has been utitilizing duplex arteriography (DA) for evaluating the arteries of the lower extremity for patients undergoing lower extremity revascularization. In an effort to further explore the strengths and weaknesses of DA, we reviewed our evolving experience with DA from January 1, 1998, to January 1, 2005.

Patients and Methods: The arterial segments starting from mid-abdominal aorta to the pedal arteries were studied in cross-sectional and longitudinal planes using a variety of scanheads of 7–4, 10–5, 12–5, 5–2 and 3–2 MHz extended operative frequency range to obtain high-quality B-mode, color and power Doppler images as well as velocity spectra. In 906 patients, 1,020 duplex arteriograms were obtained. The ages ranged from 30–98 years old with a mean of 73±11 (SD) years. Fifty percent of the patients were diabetics. Indications for the examination included: tissue loss (409), rest pain (221), claudication (310), acute ischemia (74), popliteal aneurysm (45), SFA aneurysm (2), abdominal aortic aneurysms (AAA) (10) and failing bypass (55). Prior procedures had been performed in 262. DA was performed by six technologists (4 of whom are MDs). In all, 207 DA were performed intraoperatively and the remainder, preoperatively.

Results: The resultant procedures based upon DA included: bypass to the popliteal artery (262) and bypass to an infrapopliteal artery (325), endovascular procedures (363), thrombectomy (11), embolectomy (9), inflow bypass procedures to the femoral arteries (46), débridment (4), amputation (8) and no intervention (75). The areas not visualized well included: iliac (73), femoral (26), popliteal (17), and infrapopliteal (221). Additional imaging after DA was deemed necessary in 102 cases to obtain enough information to plan lower extremity revascularization. Factors associated with increased need to obtain CA included: DM ( p<.001), infrapopliteal calcification ( p<.001), older age ( p = .01) and limb threatening ischemia ( p<.001). Factors not associated with the need to obtain CA included: which technologist performed the exam, whether the technologist has a medical degree and whether the patient underwent prior revascularization.

Conclusions: In 90% of patients reviewed, DA is able to obtain the needed information to plan lower extremity revascularization. Severe tibial vessel calcification is the most common cause of an incomplete DA exam and determines when alternative imaging modalities need to be obtained.

Preprocedural imaging: new options to reduce need for contrast angiography

In vascular surgery, the gold standard for evaluation of the lower-extremity arterial tree has long been contrast arteriography (CA). Associated risks of CA are well-documented and include severe allergic reactions, arterial injury and/or hemorrhage, and contrast-induced nephropathy. Increasingly, less-invasive techniques, with fewer inherent risks for complication, are being explored as diagnostic alternatives. Magnetic resonance angiography, computed tomography angiography, and duplex arteriography, each offer distinct advantages, though are not without limitation. This review explores the indications, advantages, and disadvantages of these newer technologies and provides a comparison to CA as a means for defining the anatomic features of patients undergoing lower-extremity revascularization. This data suggests that noninvasive imaging technologies may, in the future, play an increasingly important role in the surgical evaluation of the patient with lower-extremity ischemia.

Clinical utility of time-resolved imaging of contrast kinetics (TRICKS) magnetic resonance angiography for infrageniculate arterial occlusive disease

OBJECTIVE

The diagnostic accuracy of magnetic resonance angiography (MRA) in the infrapopliteal arterial segment is not well defined. This study evaluated the clinical utility and diagnostic accuracy of time-resolved imaging of contrast kinetics (TRICKS) MRA compared with digital subtraction contrast angiography (DSA) in planning for percutaneous interventions of popliteal and infrapopliteal arterial occlusive disease.

METHODS

Patients who underwent percutaneous lower extremity interventions for popliteal or tibial occlusive disease were identified for this study. Preprocedural TRICKS MRA was performed with 1.5 Tesla (GE Healthcare, Waukesha, Wis) magnetic resonance imaging scanners with a flexible peripheral vascular coil, using the TRICKS technique with gadodiamide injection. DSA was performed using standard techniques in angiography suite with a 15-inch image intensifier. DSA was considered the gold standard. The MRA and DSA were then evaluated in a blinded fashion by a radiologist and a vascular surgeon. The popliteal artery and tibioperoneal trunk were evaluated separately, and the tibial arteries were divided into proximal, mid, and distal segments. Each segment was interpreted as normal (0% to 49% stenosis), stenotic (50% to 99% stenosis), or occluded (100%). Lesion morphology was classified according to the TransAtlantic Inter-Society Consensus (TASC). We calculated concordance between the imaging studies and the sensitivity and specificity of MRA. The clinical utility of MRA was also assessed in terms of identifying arterial access site as well as predicting technical success of the percutaneous treatment.

RESULTS

Comparisons were done on 150 arterial segments in 30 limbs of 27 patients. When evaluated by TASC classification, TRICKS MRA correlated with DSA in 83% of the popliteal and in 88% of the infrapopliteal segments. MRA correctly identified significant disease of the popliteal artery with a sensitivity of 94% and a specificity of 92%, and of the tibial arteries with a sensitivity of 100% and specificity of 84%. When used to evaluate for stenosis vs occlusion, MRA interpretation agreed with DSA 90% of the time. Disagreement occurred in 15 arterial segments, most commonly in distal tibioperoneal arteries. MRA misdiagnosed occlusion for stenosis in 11 of 15 segments, and stenosis for occlusion in four of 15 segments. Arterial access was accurately planned based on preprocedural MRA findings in 29 of 30 patients. MRA predicted technical success 83% of the time. Five technical failures were due to inability to cross arterial occlusions, all accurately identified by MRA.

CONCLUSION

TRICKS MRA is an accurate method of evaluating patients for popliteal and infrapopliteal arterial occlusive disease and can be used for planning percutaneous interventions.

Value of single-dose contrast-enhanced magnetic resonance angiography versus intraarterial digital subtraction angiography in therapy indications in abdominal and iliac arteries

The objective of the study was to prove the value of single-dose contrast-enhanced magnetic resonance angiography [three-dimensional (3D) ceMRA] in abdominal and iliac arteries versus the reference standard intra-arterial digital subtraction angiography (i.a.DSA) when indicating a therapy. Patients suspected of having abdominal or iliac artery stenosis were included in this study. A positive vote of the local Ethics Committe was given. After written informed consent was obtained, 37 patients were enrolled, of which 34 were available for image evaluation. Both 3D ceMRA and i.a. DSA were performed for each patient. The dosage for 3D ceMRA was 0.1 mmol/kg body weight in a 1.5-T scanner with a phased-array coil. The parameters of the 3D-FLASH sequence were as follows: TR/TE 4.6/1.8 ms, effective thickness 3.5 mm, matrix 512 x 200, flip angle 30 degrees , field of view 420 mm, TA 23 s, coronal scan orientation. Totally, 476 vessel segments were evaluated for stenosis degree by two radiologists in a consensus fashion in a blinded read. For each patient, a therapy was proposed, if clinically indicated. Sensitivity, specificity, positive and negative predictive values, and accuracy for stenoses > or = 50% were 68%, 92%, 44%, 97%, and 90%, respectively. In 13/34 patients, a discrepancy was found concerning therapy decisions based on MRA findings versus therapy decisions based on the reference standard DSA. The results showed that the used MRA imaging technique of abdominal and iliac arteries is not competitive to i.a. DSA, with a high rate of misinterpretation of the MRAs resulting in incorrect therapies.

A multicenter, site-independent, blinded study to compare the diagnostic accuracy of contrast-enhanced magnetic resonance angiography using 1.0M gadobutrol (Gadovist™) to intraarterial digital subtraction angiography in body arteries

PURPOSE

Prospective evaluation of diagnostic accuracy of single field-of-view contrast-enhanced MR Angiography (ceMRA) with 1.0M gadobutrol compared to intraarterial DSA in body arteries.

MATERIALS AND METHODS

In an European multicenter study 179 patients underwent ceMRA and DSA. For each indication five prospectively defined vessel segments were evaluated by local investigators onsite and by three site-independent blinded readers (BR) independently.

RESULTS

The agreement between ceMRA and DSA diagnosis was statistically significant in the onsite (96.6%) and blinded reader (86.6-90.2%) evaluation. Sensitivity, specificity, accuracy, positive (PPV) and negative predictive values (NPV) for detection of relevant stenosis (>50%) were calculated for the right and left internal carotid arteries, and common and external iliac arteries: Sensitivity was 95-98% (onsite) and 76-96% (BR), specificity 94-96% (onsite) and 86-94% (BR), accuracy 96% (onsite) and 87-93% (BR), NPV 98-99% (onsite) and 84-98% (BR), and PPV 79-93% (onsite) and 44-91% (BR), respectively.

CONCLUSION

CeMRA of body arteries using 1.0M gadobutrol provides diagnostic information comparable to intraarterial DSA.

Preoperative MR Angiography in Free Fibula Flap Transfer for Head and Neck Cancer: Clinical Application and Influence on Surgical Decision Making

OBJECTIVE

We review the fibular free flap surgical procedure to illustrate the usefulness of preoperative lower limb MR angiography and to show how calf vascular anatomy on MR angiography affects patient surgical management.

CONCLUSION

With its high positive predictive value and sensitivity, preoperative MR angiography can improve the chances of a successful outcome at the recipient mandibular site. It provides the reconstructive surgeon with a road map, revealing vascular anomalies or disease that could alter or contraindicate surgery.

Computed tomography aortic three-dimensional reconstruction: An invaluable tool for diagnosis of juxtarenal abdominal aortic aneurysm

Accurate mapping of the aortic aneurysm in relation to the renal artery is pivotal in the success of abdominal aortic aneurysm repair. Currently, contrast computed tomography (CT), a method of combining both angiography and CT scan, is being used in the evaluation and diagnosis of abdominal aortic aneurysm. We report a series of cases in which contrast CT alone gave us misleading information on the true nature of the aneurysm in relation to the renal arteries. We conclude that the three-dimensional spiral CT reconstructed model provides better morphologic information for clinical decision-making than contrast CT alone.

Accelerated time-resolved 3D contrast-enhanced MR angiography at 3T: clinical experience in 31 patients

PURPOSE

To evaluate whether time-resolved 3D MR-angiography at 3T with a net acceleration factor of eight is applicable in clinical routine and to evaluate whether good image quality and a low artifact level can be achieved with a temporal update rate that allows for additional information on pathologies.

MATERIALS AND METHODS

Thirty-one consecutive patients underwent time-resolved 3D contrast-enhanced MR-angiography on a 3T system. Imaging consisted of accelerated 3D gradient echo sequences combining parallel imaging with an acceleration factor of four, partial Fourier acquisition along phase and slice encoding direction, and twofold temporal acceleration using view sharing. Data volumes representing the arterial and venous contrast phases were independently evaluated by two experienced radiologists by grading of image quality and artifact level on a 0-3 scale.

RESULTS

Time-resolved MR-angiography was successfully performed in all subjects without the need for contrast agent bolus timing. Excellent arterial (average score = 2.65 +/- 0.32) and good venous (average score = 2.56 +/- 0.28) diagnostic image quality and little image degrading due to artifacts (average score = 2.20 +/- 0.16) were confirmed by both independent readers (agreement in 65.2% of all evaluations). In 14 patients vascular pathologies were identified in the arterial phases. In eight examinations temporal resolution and depiction of contrast agent dynamics provided additional information about pathology.

DISCUSSION

Without the necessity for additional bolus timing, time-resolved 3D contrast-enhanced MR-angiography with imaging acceleration along both the spatial encoding direction and temporal domain revealed excellent diagnostic image quality in neurovascular and thoracic imaging. Despite the limited spatial resolution as compared to high-resolution imaging of the carotid artery bifurcation, the results demonstrate the applicability of contrast-enhanced MR-angiography in thoracic and abdominal MRA as well as cervical imaging with a temporal update rate allowing for additional information on pathologies. Future studies may include an evaluation of optimal trade-offs between spatial and temporal resolution, different acceleration factors and a comparison to the gold-standard for accuracy.

In vitroevaluation of stent patency and in-stent stenoses in 10 metallic stents using MR angiography

In vitro study to investigate the suitability of contrast enhanced magnetic resonance angiography (CEMRA) for determination of stent patency and grading of in-stent stenoses in 10 metallic stents. The Acculink carotid, DynaLink, Easy Wallstent, JostentSelfX XF, Luminexx, Omnilink, sinus-SuperFlex, SMART, Symphony and ZA stent were separately placed in a vascular phantom. Dedicated stenoses inside the stents generated a concentric lumen narrowing of 50%. CEMRA was performed for each stent. Signal loss inside the stents and artificial lumen narrowing were assessed objectively using the evaluation software of the MR imager. Moreover, three blinded observers determined visibility of stent patency and in-stent stenoses subjectively on a 3-point scale and graded in-stent stenoses. Loss of signal intensity within the stent lumen ranged between 90% (Wallstent) and 5% (ZA), artificial lumen narrowing between 56% (Symphony) and 22% (ZA). For the Symphony and Wallstent, visibility of patency and in-stent stenoses was impaired and the observers' grading exaggerated the degree of stenoses (by 23% and 33%, respectively). For the remainder of stents, patency and stenoses were visible and stenoses were graded accurately (less than 10% discrepancy from reference standard). In this in vitro study, eight of 10 stents presented with MRI characteristics which enabled determination of stent patency and accurate grading of clinically relevant in-stent stenoses.

Evaluation of various image reconstruction parameters in lower extremity stents using multidetector-row CT angiography: initial findings

Image quality, visible lumen and patency of lower limb stents was assessed by multidetector-row computed tomography (MDCT) angiography using various reconstruction parameters and the results compared with conventional angiography. Fourteen patients (25 stents) were evaluated. From MDCT datasets, axial and coronal oblique reformations were reconstructed using differing reconstruction parameters (slice thickness, kernel, views). Artifacts and image quality were assessed using a five-degree scale (1=excellent, 5=poor). Visible stent diameter was measured. Stenosis severity was compared with calibrated catheter angiography. The image quality of medium and sharp image kernels were good/fair (1.9-2.4), while smooth kernel provided only acceptable/poor image quality (3.9-4.4). Coronal oblique images were rated superior to assess in-stent lumen rather than axial. Using medium and sharp kernels, the visible stent lumen was significantly greater than using smooth kernel (P<0.001). thirteen out of fourteen patients (24/25 stents) were correctly classified as patent. In one patient, in-stent stenosis (> or =50%) was falsely diagnosed using CT angiography (CTA) with smooth kernel and was, therefore, rated as false positive. Coronal oblique views, as well as medium and sharp kernels, have shown the best results regarding image quality to assess stent patency in the lower limb. Therefore, MDCT could be a valuable non-invasive modality for stent imaging in the peripheral vasculature.

Intra-arterial MR angiography in the iliac system: initial clinical experience with 25 patients

The aim of this study was to evaluate intra-arterial magnetic resonance angiography (MRA) of the iliac arteries. Therefore, 25 consecutive patients (17 male, 8 female) suffering from symptomatic occlusive disease of the lower limbs were investigated prospectively. Catheter angiography was performed before MRA and served as the standard of reference. Contrast-enhanced intra-arterial MRA was performed using a 1.5 Tesla MRI system. Contrast agent (gadodiamide) was injected by a conventional pigtail-shaped angiography catheter placed in the abdominal aorta. Vascular lesions were assessed by four investigators. The degree of stenosis was compared with the findings of conventional catheter angiography. Additionally, the diagnostic quality of the MR angiograms was assessed by the investigators using a semi quantitative five-point scale. All lesions shown by catheter angiography were detected and correctly localized by intra-arterial MRA. MR angiograms exhibit a specificity of 95% and a sensitivity of 96% for stenoses of 50% or more. The diagnostic quality of the images was judged from good to excellent, on average. Intra-arterial MRA exhibits a specificity and sensitivity comparable with intravenous angiography. The image quality appears to be adequate for supporting MR-guided vascular intervention.

Abdominal and iliac arterial stenoses: comparative double-blinded randomized study of diagnostic accuracy of 3D MR angiography with gadodiamide or gadopentetate dimeglumine

PURPOSE

To prospectively evaluate accuracy of gadolinium-enhanced three-dimensional (3D) magnetic resonance (MR) angiography with gadodiamide and gadopentetate dimeglumine (0.1 mmol/kg), with intraarterial DSA as reference standard, for imaging abdominal and iliac arterial stenoses.

MATERIALS AND METHODS

The study was approved by all institutional review boards; informed consent was obtained from each subject before procedures. Two hundred forty-seven subjects were included; 240 received either contrast agent and were available for safety analysis; 222 were available for accuracy analysis. Enhanced 3D MR angiography and DSA were performed; image data were evaluated in a double-blinded randomized study. Stenoses were classified as not relevant (<50% stenosis) or relevant (> or =50%). For detection of main stenosis, accuracy with enhanced 3D MR angiography compared with that with DSA was determined.

RESULTS

The difference in accuracy for imaging with gadodiamide and gadopentetate was 3.6%. Noninferiority was inferred because the lower bound of the exact two-sided 95% confidence interval was -10.1 and was above the noninferiority margin (-15%). Accuracy for detection of the main stenosis was low, 56.4% for gadodiamide and 52.8% for gadopentetate group. Subgroup analysis with exclusion of inferior mesenteric artery and internal iliac arteries and the most false-positive stenosis classifications yielded better results: 76.6% and 71.6%, respectively. Sensitivity, specificity, and negative and positive predictive values did not differ substantially between study groups. In the main analysis, values were 44%, 96%, 35%, and 97% for gadodiamide and 44%, 83%, 30%, and 90% for gadopentetate, respectively. In the subgroup analysis, values were 66%, 95%, 61%, and 96% for gadodiamide and 63%, 86%, 58%, and 88% for gadopentetate, respectively.

CONCLUSION

Noninferiority of gadodiamide versus gadopentetate was verified based on the primary end point, which was accuracy for detection of the main stenosis with enhanced 3D MR angiography compared with DSA.

Superficial femoral artery occlusive disease severity correlates with MR cine phase-contrast flow measurements

PURPOSE

To evaluate how cine phase-contrast (PC) flow data correlate with the severity of peripheral vascular disease (PVD).

MATERIALS AND METHODS

Flow waveforms were obtained in 48 patients proximal and distal to superficial femoral artery (SFA) disease using the 2D cine PC technique with velocity encoding (venc) = 100 cm/second. Flow data were correlated with SFA disease severity and compared with data from nine healthy volunteers.

RESULTS

Of 96 arterial segments in 48 patients, 26 were patent or only mildly stenotic, 35 had moderate-to-severe stenosis, and 35 were occluded. The flow patterns tended to become low-resistant below severe stenoses or occlusion. The mean peak flow velocity above/below SFA lesions was significantly higher in patients with severe disease (1.9 +/- 1.0, P = 0.01) or occlusion (2.0 +/- 1.0, P = 0.003) compared to normal volunteers (1.4 +/- 0.6). The delay in peak velocity below the lesions showed a significant positive correlation with lesion severity (r = 0.65, P < 0.001). The mean flow volume ratio above/below SFA lesions was greater in patients with occluded vessels compared to normal volunteers (3.9 and 2.3 respectively; P = 0.04).

CONCLUSION

Cine PC flow waveform changes across atherosclerotic lesions correlate with disease severity. This may help determine which lesions are hemodynamically significant.

In Vivo Evaluation of Patency and In-Stent Stenoses After Implantation of Nitinol Stents in Iliac Arteries Using MR Angiography

OBJECTIVE

Our study was a prospective in vivo study to evaluate whether MR angiography is suitable for assessing stent patency and grading in-stent stenoses and to examine whether the accuracy of MR angiography changes with time after stent implantation.

SUBJECTS AND METHODS

In a prospective study, 34 iliac stenoses in 27 patients were treated by implantation of 35 nitinol stents. MR angiography was performed immediately after stent placement for 32 stents, and both digital subtraction angiography (DSA) and MR angiography were repeated at the 6-month follow-up for 23 stents. Three blinded observers assessed stent patency and the degree of in-stent stenoses on MR angiography and DSA (the standard of reference) images. The difference between the observers' grading of stenoses on DSA and on MR angiography was determined. Statistical analysis was performed using the Student's t test for paired samples.

RESULTS

Stent patency was assessed correctly for all stents and both sets of MR angiography images. Evaluation of DSA 1 images (obtained at end of implantation procedure) revealed that 96.9% of in-stent stenoses were less than 50%. On DSA 2 images (obtained at follow-up), 95.7% of in-stent stenoses were graded as less than 50%. The difference between grading of stenoses on DSA and MR angiography images was 15.0% +/- 16.0% (minimum, 0.0%; maximum, 63.3%) for DSA 1 versus MR angiography 1 (statistically significant, p = 0.037) and 9.8% +/- 13.5% (minimum, 0.0%; maximum, 63.3%) for MR angiography 2 versus DSA 2 (not statistically significant, p = 0.355).

CONCLUSION

Patency was correctly assessed for all stents on MR angiography. The quality of MR angiography regarding characterization of in-stent stenoses improved with time after stent placement. However, discrepancies of more than 60% between grading of lumen narrowing on DSA and MR angiography images occurred even at the 6-month follow-up. Thus, MR angiography is not yet a reliable technique for characterization of in-stent stenoses.

Critical limb ischemia: hybrid MR angiography compared with DSA

PURPOSE

To compare a hybrid magnetic resonance (MR) angiography protocol with selective digital subtraction angiography (DSA) in patients with critical limb ischemia.

MATERIALS AND METHODS

The study was approved by the institutional review board, and written consent was obtained from all patients. Pretreatment DSA and hybrid MR angiography were performed in 19 consecutive patients (15 men, four women; mean age, 69.8 years; range, 44-86 years). Hybrid MR angiography included submillimeter dual-phase three-dimensional gadolinium-enhanced MR angiography in lower calf and foot, and four-station bolus-chase MR angiography in pelvis, thigh, and upper calf. Three readers identified the target lesion and inflow and outflow segments and determined treatment (bypass graft placement, percutaneous transluminal angioplasty, conservative management, amputation). Results of interobserver and intermethod comparisons were expressed as percentage of agreement and 95% confidence interval (CI).

RESULTS

On hybrid MR angiograms, no substantial venous overlay was present and image quality was excellent or adequate in 18 (95%) of 19 limbs. Readers 1, 2, and 3 selected the identical target lesion on the DSA image and the MR angiogram in 18, 17, and 18 of 18 comparable limbs, respectively. Mean percentage of agreement for readers 1 and 3 was 100% (95% CI: 81%, 100%) and for reader 2 was 94% (95% CI: 73%, 100%). Agreement of all three readers was superior with use of MR angiography for determination of inflow segments (13 [72%] of 18 limbs) and outflow segments (17 [94%] of 18 limbs), compared with agreement with use of DSA (13 [68%] of 19 inflow segments, 10 [53%] of 19 outflow segments). Agreement in therapy decisions was higher with DSA (15 [79%] of 19) than with MR angiography (11 [61%] of 18).

CONCLUSION

Preliminary data strongly support the combination of submillimeter dual-phase MR angiography in lower calf and foot with four-station bolus-chase MR angiography to extend the utility of MR angiography to patients with critical limb ischemia.

Contrast-enhanced magnetic resonance angiography of the lower extremities: Standard-dose vs. high-dose gadodiamide injection

PURPOSE

To compare the efficacy and safety of two different doses (0.1 and 0.3 mmol/kg of body weight [BW]) of gadodiamide for contrast-enhanced magnetic resonance angiography (ce-MRA) of the lower extremities with intraarterial digital subtraction angiography (IA-DSA).

MATERIALS AND METHODS

A total of 30 patients with peripheral arterial occlusive disease underwent IA-DSA and ce-MRA from the aortic bifurcation down to the ankle. Patients were randomized to receive a total dose of 0.1 or 0.3 mmol/kg of BW gadodiamide (Omniscan, Amersham Buchler), administered intravenously as a series of three automatic bolus injections. Ce-MRA was performed with a 1.5-T system using a body phased-array coil, centered stepwise over the calf, thigh, and pelvic region. A fast T1-weighted, three-dimensional gradient-echo sequence was obtained before and after injection of the allocated dose. IA-DSA was performed using the Seldinger technique and a femoral approach. The vessels under investigation were divided into 31 segments, and ce-MRA and IA-DSA image sets were evaluated in a double-blind fashion for the presence of stenosis, presence of collateral vessels, vessel delineation, and overall image quality. Both dose groups were compared with regard to contrast index (CI) and signal- and contrast-to-noise ratios (SNR, CNR). The occurrence of adverse events or side effects was also documented. Sensitivity, specificity, and accuracy were calculated in relation to the results of stenosis grading.

RESULTS

A total of 26 patients were entered in the efficacy evaluation, while all 30 patients were included in the safety assessment. The sensitivity, specificity, and accuracy for the 0.1 and 0.3 mmol/kg dose groups were 78.8%/93.0%/88.9% vs. 60.2.%/91.5%/83.2%, respectively. The detection of collaterals was similar to IA-DSA for the 0.3 mmol/kg dose group (30.2% vs. 27.4%), but was lower in the 0.1 mmol/kg dose group (27.3% vs. 12.3%). The high-dose gadodiamide injection proved to be superior to the 0.1 mmol/kg dose group with regard to vessel delineation and overall image quality (P = 0.007 and P = 0.002, respectively). The difference between the two dose groups regarding CI, SNR, and CNR was significant (P = 0.0001), in favor of the 0.3 mmol/kg dose group. No adverse events were observed in any of the patients.

CONCLUSION

Ce-MRA with gadodiamide is safe and efficacious. Comparison of two different doses with IA-DSA as the standard of reference showed that the 0.3 mmol/kg dose is superior to the standard 0.1 mmol/kg dose with respect to contrast enhancement, vessel delineation, image quality, and detection of collaterals. However, the 0.1 mmol/kg dose was superior to the high dose in the grading of stenosis.

A Comparison of Magnetic Resonance Angiography, Contrast Arteriography, and Duplex Arteriography for Patients Undergoing Lower Extremity Revascularization

The objective of this study was to compare magnetic resonance angiography (MRA), contrast arteriography (CA), and duplex arteriography (DA) for defining anatomic features relevant to performing lower extremity revascularizations. From March 1, 2001 to August 1, 2001, 33 consecutive inpatients with chronic lower extremity ischemia underwent CA, MRA, and DA before undergoing lower extremity revascularization procedures. The reports of these tests were compared prospectively and the differences in the aortoiliac segment, femoral-popliteal, and infrapopliteal segments were noted. The vessels were classified as mild disease (<50%), moderate disease (50-70%), severe disease (71-99%), and occluded. These studies and treatment plans based on these data were compared. During this time period, 11 patients were not able to undergo MRA and therefore were excluded from the study. Thirty-three patients were included in this study. These patients underwent 35 procedures, as 2 patients underwent bilateral procedures. The mean age of the 33 patients was 76+/-10 years (SD). Indications for the procedures included gangrene (20), ischemic ulcer (8), rest pain (4), and severe claudication (1). Patients' medical history included diabetes mellitus (25), hypertension (20), and end-stage renal disease (5). No differences were noted between intraoperative findings and CA in this series. Two of the three differences between DA and CA were felt to be clinically significant whereas 9 of the 12 differences between MRA and CA were felt to be clinically significant. On the basis of these data in this series, MRA does not yet seem to be able to obtain adequate data on infrapopliteal segments, at least not for this highly selected population. When severe tibial calcification or very low flow states are identified, CA may be necessary for patients undergoing DA.

Magnetic resonance angiography versus duplex arteriography in patients undergoing lower extremity revascularization: which is the best replacement for contrast arteriography?

OBJECTIVE

In an effort to explore alternatives to contrast material-enhanced arteriography, we compared magnetic resonance angiography (MRA) and duplex arteriography (DA) with contrast arteriography (CA) for defining anatomic features in patients undergoing lower extremity revascularization.

METHODS

From August 1, 2001, to August 1, 2002, 61 consecutive inpatients (64 limbs) with chronic lower extremity ischemia underwent CA, MRA, and DA before undergoing lower extremity revascularization procedures. The reports of these tests and images were compared prospectively, and the differences in the iliac, femoropopliteal, and infrapopliteal segments were noted. The vessels were classified as mildly diseased (<50%), moderately diseased (50%-70%), severely diseased (71%-99%), or occluded. The studies and treatment plans based on these data were compared.

RESULTS

Mean patient age was 76 +/- 10 years (SD). Indications for the procedures included gangrene (43%), ischemic ulcer (28%), rest pain (19%), severe claudication (9%), and failing bypass (1%). During this period 35 patients were ineligible for the protocol, because they could not undergo MRA (n=27) or angiography (n=8). Of the total 192 segments in the 64 patients (iliac, femoropopliteal, tibial), 17% were not able to be fully assessed with DA, and 7% with MRA. Disagreements with CA and DA were found in the iliac, femoropopliteal, and tibial segments in 0%, 7%, and 14% of cases, respectively, and between CA and MRA in 10%, 26%, and 42% of cases, respectively. Two of 9 differences (22%) between DA and CA were thought to be clinically significant, and 28 of 45 differences (62%) between MRA and CA were thought to be clinically significant.

CONCLUSIONS

A review of the data obtained in this series indicates that MRA does not yet seem to yield adequate data, at least in this highly selected population at our institution. When severe calcification is identified, CA may be necessary in patients undergoing DA.

MDCT Compared with Digital Subtraction Angiography for Assessment of Lower Extremity Arterial Occlusive Disease:Importance of Reviewing Cross-Sectional Images

OBJECTIVE

The aim of our study was to evaluate the efficacy of MDCT angiography in the assessment of lower limb peripheral arterial occlusive disease.

MATERIALS AND METHODS

Twenty-four patients (representing 27 cases) with symptomatic lower extremity peripheral arterial occlusive disease underwent both MDCT angiography and digital subtraction angiography of the aortoiliac and lower extremity arteries. For data analysis, the arterial system was divided into 10 segments. Each segment was classified as normal, mildly stenotic, moderately stenotic, severely stenotic, or occluded. In evaluating MDCT angiographic findings, cross-sectional images were mainly observed by scrolling. The diagnostic accuracy of MDCT angiography was determined, using digital subtraction angiography as the standard reference. The extent of calcification in each segment was also assessed on MDCT angiography and was classified as absent, mildly calcified, or severely calcified.

RESULTS

Of the 480 segments studied, 470 were assessable on both digital subtraction angiography and MDCT angiography. On digital subtraction angiography, 142 stenoocclusive segments (20 mildly stenotic, 14 moderately stenotic, 25 severely stenotic, and 83 occluded) were detected. With regard to the detection of segments that had more than mild stenosis, the sensitivity, specificity, and accuracy of MDCT angiography were 99.2%, 99.1%, and 99.1%, respectively. In the 421 noncalcified and mildly calcified segments, the sensitivity, specificity, and accuracy of MDCT angiography for the detection of more-than-mild stenosis were 100%, 100%, and 100%, respectively.

CONCLUSION

MDCT angiography is a reliable method for evaluating the aortoiliac and lower extremity arteries.

Is half-dose contrast-enhanced three-dimensional MR angiography sufficient for the abdominal aorta and pelvis?

PURPOSE

To evaluate the usefulness of half-dose contrast-enhanced magnetic resonance (MR) angiography for depicting the abdominal aorta and its major branches.

MATERIALS AND METHODS

A total of 72 consecutive patients were randomly assigned to one of four groups that underwent MR angiography after receiving different concentrations (original or diluted to 50%) and total amounts (single or half-dose) of gadolinium chelate injected at different rates (1 or 0.5 mL/second). The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the abdominal aorta and of the common and external iliac arteries were calculated, and two blinded readers rated the respective image qualities.

RESULTS

The SNR and CNR of the abdominal aorta and the common iliac artery in the 0.5 mL/second groups were statistically significantly lower than those in the 1 mL/second groups. The differences in overall image quality across the four groups were not statistically significant.

CONCLUSION

Half-dose MR angiography using diluted contrast medium injected at a rate of 1 mL/second depicted the abdominal aorta and its branches as clearly as using a full single dose.

Contrast-enhanced peripheral magnetic resonance angiography using time-resolved vastly undersampled isotropic projection reconstruction

PURPOSE

To investigate the application of time-resolved vastly undersampled isotropic projection reconstruction (VIPR) in contrast-enhanced magnetic resonance angiography of the distal extremity (single station), and peripheral run-off vasculature in the abdomen, thigh, and calf (three stations).

MATERIALS AND METHODS

Time-resolved distal extremity imaging was performed using VIPR sequence through the comparison of two acquisition matrix sizes: 256 with TR/TE=3.7/1.4 msec and 320 with TR/TE=4.5/1.8 msec under the same scan time of two minutes. VIPR acquisition was combined with a bolus-chase technique to image the peripheral run-off vasculature. The time-resolved images were reconstructed using a revised sliding window reconstruction filter whose temporal aperture remained narrow for low spatial frequencies and increased quadratically to include all the projection data for high spatial frequencies.

RESULTS

The new temporal filter significantly suppressed the undersampling streak artifacts and venous contamination, while maintaining a high temporal resolution. Both high spatial resolution (ranging from 1.56 x 1.56 x 1.56 mm to 1.25 x 1.25 x 1.25 mm) and high temporal resolution (three seconds per frame) distal extremity images and peripheral run-off images were generated using time-resolved VIPR acquisition, which provides isotropic spatial resolution and isotropic coverage.

CONCLUSION

Time-resolved VIPR acquisition was demonstrated to be well suited for distal extremity imaging by providing isotropic spatial resolution, isotropic coverage, and high temporal resolution. The combination of time-resolved VIPR and bolus chase technique provided a novel approach for peripheral run-off examinations.

Gadobutrol-enhanced moving-table magnetic resonance angiography in patients with peripheral vascular disease: a prospective, multi-centre blinded comparison with digital subtraction angiography

The purpose of this study was to compare moving-table three-dimensional contrast-enhanced magnetic resonance angiography (CE MRA), using 1.0-mol gadobutrol, with intra-arterial digital subtraction angiography (i.a. DSA) for evaluation of pelvic and peripheral arteries in patients with peripheral arterial occlusive disease. A total of 203 patients were examined in a prospective, multi-centre study at 1.0/1.5 T. Ten vessel segments of one leg were evaluated on-site and by three independent blinded reviewers off-site. One hundred eighty-two patients were evaluable in blinded reading. For pelvis and thigh, there was statistically significant diagnostic agreement between CE MRA and i.a. DSA on-site (94%) and off-site (86-88%). Overall, for detection of clinically significant stenoses, 93% sensitivity and 90% specificity were achieved in on-site evaluation, with 71-76 and 87-93% off-site; for detection of occlusion, sensitivity and specificity on-site were 91 and 97%, with 75-82 and 94-98% off-site. Evaluation was more sensitive on-site than off-site for detection of stenoses and occlusion, whereas specificity was similar. The CE MRA with 1.0-mol gadobutrol gave results comparable to those of i.a. DSA for the larger arteries of pelvis and thigh. Results for calf arteries were compromised by spatial resolution and technical limitations.

Peripheral MR angiography

Peripheral arterial occlusive disease is a chronic and progressive disease with a reported incidence rate from 4.5% to 8.8% in men over 55 years of age. The diagnosis is usually made clinically, but for treatment planning and control, imaging of the peripheral arteries is required. Since its introduction in 1994, contrast-enhanced MR angiography has demonstrated a high diagnostic confidence and has replaced the invasive intra-arterial DSA, which is still the current gold standard for many different indications. For the peripheral arteries, clinical use of MR angiography was hampered for some years by the unsolved problem of the large imaging volume and the small diameter of the distal arteries. However, since the availability of ultra-fast high-gradient sequences and the possibility of moving-bed imaging, contrast-enhanced MR angiography, over the last few years, has shown its enormous potential and high accuracy in the diagnosis and follow-up of patients suffering from peripheral arterial occlusive disease. Exciting innovations in hardware and software allows very fast, very accurate, and very robust noninvasive imaging of the peripheral arteries, and both treatment planning as well as follow-up can be performed using contrast-enhanced MR angiography. The following review introduces the basic concepts of peripheral MR angiography--focusing on contrast enhanced imaging--and presents the different techniques as well as some potential limitations and how they could be solved. Finally, this article provides a look into the already-begun future of peripheral contrast-enhanced MR angiography with hybrid and combination techniques.

Helical computed tomography angiography is the most efficient test to assess vascular calcifications in the iliac arterial sector in renal transplant candidates

The increased scope of renal transplant indications has lead to a larger number of recipients with vascular problems due to arterial calcifications in the iliac region. Compared to magnetic resonance and conventional arteriography, helical computed tomography angiography (HCTA) accurately depicts arterial diseases, including the location and extent of arterial calcification. The objective of this study was to assess the value of HCTA with maximum-intensity-projection (MIP) reconstruction to evaluate iliac arterial calcifications and stenosis among candidates for renal transplantation.

MATERIAL AND METHODS

From December 1997 to March 2002, 114 HCTA scans with MIP reconstruction were performed in candidates for renal transplantation. Included patients fulfilled some of the following conditions: (a) older than 55 years, (b) diabetic, (c) second transplants, and (d) obvious vascular calcifications on plain abdominal x-ray.

RESULTS

Among the 114 patients, 33 (29%) were excluded for transplantation due to universal calcification of the iliac arterial sector, and 81 (71%) were included on the waiting list due to the presence of calcium-free areas for the vascular anastomosis. Transplantation, which was attempted in 28 of the 81 patients, was successful in 25 using the area programmed after HCTA analysis. The transplants failed in three cases because no calcium-free area could be found upon surgical examination.

CONCLUSION

HCTA with MIP reconstruction makes it possible to draw an exact map of the arterial calcifications of the iliac arterial sector, allowing better recipient selection and accurate planning for the vascular anastomosis and placement of the renal graft.

SNR improvement for multiinjection time-resolved high-resolution CE-MRA of the peripheral vasculature

Peripheral MR angiography (MRA) should ideally provide images over a large field of view with high spatial resolution and adequate temporal resolution to accommodate differences in regional filling times. Image subtraction is usually used to remove background signals. In examination protocols involving multiple injections at multiple sites, previously injected contrast present in the mask image provides a substantial decrease in the subtraction image signal. Bolus chase methods avoid this problem but provide limited time for acquisition of high-resolution images at each station. We present here a technique applied to peripheral angiography that provides high spatial and temporal resolution while maintaining high SNR in multiple injection examinations. Undersampled projection imaging was used to increase spatial resolution relative to a previously reported technique using a Cartesian acquisition technique. Late acquisition of high spatial frequencies and temporal matched-filtering were used to increase spatial resolution and SNR, respectively. Temporal correlation analysis was applied to permit multistation examinations without mask subtraction, thus providing an additional gain in SNR relative to multistation subtraction methods. Quantitative analysis is provided to evaluate the signal and noise behavior in the matched-filtering process due to multiinjection and mask subtraction.