3D Contrast-enhanced MR Angiography Research Articles

Cardiovascular magnetic resonance in patients with pectus excavatum compared with normal controls.

PurposeTo assess cardiothoracic structure and function in patients with pectus excavatum compared with control subjects using cardiovascular magnetic resonance imaging (CMR).MethodThirty patients with pectus excavatum deformity (23 men, 7 women, age range: 14-67 years) underwent CMR using 1.5-Tesla scanner (Siemens) and were compared to 25 healthy controls (18 men, 7 women, age range 18-50 years). The CMR protocol included cardiac cine images, pulmonary artery flow quantification, time resolved 3D contrast enhanced MR angiography (CEMRA) and high spatial resolution CEMRA. Chest wall indices including maximum transverse diameter, pectus index (PI), and chest-flatness were measured in all subjects. Left and right ventricular ejection fractions (LVEF, RVEF), ventricular long and short dimensions (LD, SD), mid-ventricle myocardial shortening, pulmonary-systemic circulation time, and pulmonary artery flow were quantified.ResultsIn patients with pectus excavatum, the pectus index was 9.3 ± 5.0 versus 2.8 ± 0.4 in controls (P < 0.001). No significant differences between pectus excavatum patients and controls were found in LV ejection fraction, LV myocardial shortening, pulmonary-systemic circulation time or pulmonary flow indices. In pectus excavatum, resting RV ejection fraction was reduced (53.9 ± 9.6 versus 60.5 ± 9.5; P = 0.013), RVSD was reduced (P < 0.05) both at end diastole and systole, RVLD was increased at end diastole (P < 0.05) reflecting geometric distortion of the RV due to sternal compression.ConclusionDepression of the sternum in pectus excavatum patients distorts RV geometry. Resting RVEF was reduced by 6% of the control value, suggesting that these geometrical changes may influence myocardial performance. Resting LV function, pulmonary circulation times and pulmonary vascular anatomy and perfusion indices were no different to controls.

Overestimation of moderate carotid stenosis assessed by both Doppler US and contrast enhanced 3D-MR angiography in the CARMEDAS study

To evaluate the agreement and diagnostic accuracy of Contrast enhanced magnetic resonance angiography (CE-MRA), Doppler ultrasound (DUS) and Digital subtraction angiography (DSA) in the assessment of carotid stenosis. DUS, CE-MRA and DSA were performed in 56 patients included in the Carotide-angiographie par résonance magnétique-échographie-doppler-angioscanner (CARMEDAS) multicenter study with a carotid stenosis ≥ 50%. Three readers evaluated stenoses on CE-MRA and DSA (NASCET criteria). Velocities criteria were used for stenosis estimation on DUS. CE-MRA had a sensitivity and specificity of 96-98% and 66-83% respectively for carotid stenoses ≥ 50% and a sensitivity and specificity of 94% and 76-84% respectively for carotid stenoses ≥ 70%. The interobserver agreement of CE-MRA was excellent, except for moderate stenoses (50-69%). DUS had a sensitivity and specificity of 88 and 75% respectively for carotid stenoses ≥ 50% and a sensitivity and specificity of 83 and 86% respectively for carotid stenoses ≥ 70%. Combined concordant CE-MRA and DUS had a sensitivity and specificity of 100 and 85-90% respectively for carotid stenoses ≥ 50% and a sensitivity and specificity of 96-100% and 80-87% respectively for carotid stenoses ≥ 70%. The positive predictive value of the association CE-MRA and DUS for carotid stenoses ≥ 70% is calculated between 77 and 82% while the negative predictive value is calculated between 97 and 100%. CE-MRA and DUS have concordant findings in 63-72%, and the overestimations cases were recorded only for carotid stenosis ≤ 69%. Combined DUS-CE-MRA is excellent for evaluation of severe stenosis but remains debatable in moderate stenosis (50-69%) due to the risk of overestimations.

Intraindividual Comparison of Contrast-Enhanced MRI and Unenhanced SSFP Sequences of Stenotic and Non-stenotic Pulmonary Artery Diameters

To evaluate the agreement of pulmonary artery diameters assessed with 3D contrast-enhanced MR angiography (CE-MRA) and a 2D balanced steady-state-free precession sequence (bSSFP) in non-stenotic and stenotic pulmonary arteries (PA). 44 right and left PAs (30 non-stenotic and 14 stenotic) were examined in 23 consecutive patients by performing CE-MRA as well as bSSFP. Two independent readers determined the transverse diameters of the PA. No significant difference in diameter measurements was found between CE-MRA and bSSFP (p = 0.8608 for the stenotic and p = 0.6208 for the non-stenotic PA). Bland-Altman analysis revealed good agreement between CE-MRA and bSSFP for both the non-stenotic (mean bias, 0.07 cm; with 95 % limits of agreement, ± 0.34 cm) and the stenotic (mean bias, 0.05 cm; with 95 % limits of agreement, ± 0.30 cm) PA. bSSFP allows rapid and accurate determination of PA diameters without the use of ionizing radiation and the risk of contrast media-associated side-effects.

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

Non‐contrast renal artery MRA using an inflow inversion recovery steady state free precession technique (Inhance): Comparison with 3D contrast‐enhanced MRA

To assess the performance of a three-dimensional (3D) non-contrast respiratory-triggered steady state free precession (SSFP) pulse sequence for detection of renal artery stenosis. A total of 64 patients who had non-contrast MR angiography (NC MRA) and 3D contrast-enhanced MRA (CE MRA) performed during the same exam and three patients who had NC MRA followed by conventional catheter angiography within one month of the MRI exam were included in this retrospective study. Two blinded readers evaluated NC MRA images for the presence of significant renal artery stenosis and also rated their diagnostic confidence and evaluated the images for artifact. A similar analysis was performed for CE MRA images by two additional blinded readers, and discrepancies were resolved by consensus reading. The 67 patients had 168 main and accessory renal arteries, with significant (>50%) stenosis in 34 arteries on CE MRA or conventional angiography. The two NC MRA readers had sensitivity and specificity for detection of significant stenosis of 94%/82% and 82%/87% respectively on a per renal artery basis. There was good agreement between CE MRA and NC MRA for detection of significant renal artery stenosis. This technique should prove useful in evaluating patients with suspected renovascular hypertension who are unable to undergo CE MRA.

Quality-Evaluation Scheme for Cerebral Time-Resolved 3D Contrast-Enhanced MR Angiography Techniques

No practical tool has been reported in the literature to evaluate the quality of cerebral TR-3D-CE-MRA techniques. Our study assessed a large list of parameters used to propose a quality-evaluation scheme for TR-3D-CE-MRA. A large list of visual and quantitative parameters used to study the quality of images was collected from the literature and evaluated in 19 healthy patients and 11 patients with arteriovenous shunts who had undergone both CENTRA keyhole TR-3D-CE-MRA at 3T and CCA. Several observers evaluated the visual parameters, such as the diagnostic confidence index, artifacts, maximum vascular signal intensity, arterial-to-venous separation, and visibility of 17 arteries and 7 veins; and quantitative parameters, such as maximum arterial SI, arteriovenous transit time, arteriovenous contrast curve, and ADW. A statistical analysis was used to determine interobserver reproducibility of the visual parameters, to calculate the sensitivity of TR-3D-CE-MRA for detecting each vessel (with CCA as standard of reference), and to compare the results of the visual and quantitative evaluations. Diagnostic confidence index, artifacts, arterial-to-venous separation, and 4 vessels-the PICA, ophthalmic and occipital arteries, and the ISS-demonstrated high reproducibility and sensitivity. The ADW was the most reliable dynamic quantitative parameter and was correlated with arterial-to-venous separation. The image quality of TR-3D-CE-MRA can be effectively evaluated with a scheme of 1 quantitative and 7 visual parameters.

Contrast Material for Abdominal Dynamic Contrast-Enhanced 3D MR Angiography With Parallel Imaging: Intraindividual Equimolar Comparison of a Macrocyclic 1.0 M Gadolinium Chelate and a Linear Ionic 0.5 M Gadolinium Chelate

The purpose of this study was to compare a macrocyclic 1.0 M contrast agent with a linear ionic 0.5 M contrast agent at equimolar dosage in regard to image quality and number of vessel segments visualized at abdominal dynamic contrast-enhanced 3D MR angiography. In an intraindividual comparative study, 15 patients (six women, nine men; mean age, 53 +/- 12.1 years; range, 25-72 years) underwent 32 1.5-T whole-body contrast-enhanced 3D MR angiographic examinations performed with parallel imaging technique. At random and in separate sessions, each patient was examined after IV injection of 0.1 mmol/kg body weight 1.0 M macrocyclic gadobutrol and 0.5 M linear ionic gadopentetate dimeglumine. Three-dimensional data sets were acquired in the arterial, portal venous, and venous phases with identical imaging protocols. Quantitative analysis included contrast measurements of vessels compared with adjacent background tissue (Student's t test). Qualitative analysis was performed independently by two radiologists with regard to visualization of arterial and venous vessel segments and overall image quality (Wilcoxon's test). Visualization of individual vessel segments was rated significantly better after administration of 1.0 M macrocyclic gadobutrol compared with 0.5 M linear ionic gadopentetate dimeglumine (p < 0.001). Overall image quality was superior with 1.0 M macrocyclic gadobutrol, but the difference was not significant. Vessel-to-background contrast after injection of 1.0 M macrocyclic gadobutrol was significantly higher (arterial phase, 0.90, p = 0.02; portal venous phase, 0.78, p = 0.0002; venous phase, 0.74, p = 0.0002) compared with 0.5 M linear ionic gadopentetate dimeglumine (arterial phase, 0.89; portal venous phase, 0.73; venous phase, 0.67). At abdominal contrast-enhanced 3D MR angiography, depiction of small abdominal vessels was significantly better and vessel-to-tissue contrast significantly higher with 1.0 M macrocyclic gadobutrol than with an equimolar dose of 0.5 M linear ionic gadopentetate dimeglumine.

Low-Dose, Time-Resolved, Contrast-Enhanced 3D MR Angiography in the Assessment of the Abdominal Aorta and Its Major Branches at 3 Tesla

The aims of this study were to evaluate the effectiveness of low-dose, contrast-enhanced (CE), time-resolved, three-dimensional magnetic resonance angiography (MRA) in the assessment of the abdominal aorta and its major branches at 3 T and to compare the results with those of high-spatial resolution CE MRA. Twenty-two consecutive patients (eight men, 14 women; mean age, 43.9 +/- 17.9 years) underwent CE time-resolved three-dimensional MRA and high-spatial resolution three-dimensional MRA. Studies were performed using a 3-T magnetic resonance system; gadolinium-based contrast medium was administered at a dose of 3 to 5 mL for time-resolved MRA, followed by 0.1 mmol/kg gadopentetate dimeglumine for single-phase CE MRA. For analysis purposes, the abdominal arterial system was divided into 11 arterial segments, and image quality as well as the presence and degree of vascular pathology were evaluated by two independent magnetic resonance radiologists. A total of 242 arterial segments were visualized with good image quality. Time-resolved MRA was able to visualize the majority of arterial segments with good definition in the diagnostic range. Vascular pathologies (stenosis, occlusion) or abnormal vascular anatomy was detected in 19 arterial segments, with good interobserver agreement (kappa = 0.78). All image findings were detected with time-resolved CE MRA by both observers and were confirmed by correlative imaging. Low-dose, time-resolved MRA at 3 T yields rapid and important anatomic and functional information in the evaluation of the abdominal vasculature. Because of its limited spatial resolution, time-resolved MRA is inferior to CE MRA in demonstrating fine vascular details.

Time-resolved, contrast-enhanced 3D MR angiography in the subclavian steal effect

The subclavian steal effect indicates atherosclerotic disease of the supraaortic vessels but rarely causes cerebrovascular events in itself. Noninvasive imaging providing detailed anatomic as well as hemodynamic information would therefore be desirable. From a group of 25 consecutive patients referred for MR angiography, four with absent or highly attenuated signal in one of the vertebral arteries on 3D multislab time-of-flight MR angiography were selected to undergo 3D time-resolved contrast-enhanced MR angiography. The time-resolved 3D contrast series (source images and MIPs) were evaluated visually and by graphic analysis of time-intensity curves derived from the respective V1 and V3 segments of both vertebral arteries on the source images. In two cases with high-grade proximal left subclavian stenosis, time-resolved 3D ce-MRA was able to visualise retrograde contrast filling of the left VA. There was a marked delay in time-to-peak between the left and right V1 segments in one case and a shallower slope of enhancement in another. In the other two cases, there was complete or collateralised segmental occlusion of the VAs.

Measuring aortic diameter with different MR techniques: Comparison of three‐dimensional (3D) navigated steady‐state free‐precession (SSFP), 3D contrast‐enhanced magnetic resonance angiography (CE‐MRA), 2D T2 black blood, and 2D cine SSFP

To compare nongated three-dimensional (3D) contrast-enhanced magnetic resonance angiography (CE-MRA) with 3D-navigated cardiac-gated steady-state free-precession bright blood (3D-nav SSFP) and noncontrast 2D techniques for ascending aorta dimension measurements. Twenty-five clinical exams were reviewed to evaluate the ascending aorta at 1.5T using: breathhold cine bright blood (SSFP), cardiac-triggered T2 black blood (T2 BB), axial 3D-nav SSFP, and nongated 3D CE-MRA. Three radiologists independently measured aortic size at three specified locations for each sequence. Means, SDs, interobserver correlation, and vessel edge sharpness were statistically evaluated. Measurements were greatest for 3D-nav SSFP and 3D CE-MRA and smallest for T2 BB. There was no significant difference between 3D-nav SSFP and 3D CE-MRA (P = 0.43-0.86), but significance was observed comparing T2 BB to all sequences. Interobserver agreement was uniformly >0.9, with T2 BB best, followed closely by 3D-nav SSFP and 2D cine SSFP, and 3D CE-MRA being the worst. Edge sharpness was significantly poorer for 3D CE-MRA compared to the other sequences (P < 0.001). If diameter measurements are the main clinical concern, 3D-nav SSFP appears to be the best choice, as it has a sharp edge profile, is easy to acquire and postprocess, and shows very good interobserver correlation.

High-resolution 3D contrast-enhanced MRA with parallel imaging techniques before endovascular interventional treatment of arterial stenosis

This study aimed to evaluate the efficacy of high-resolution 3D contrast-enhanced magnetic resonance angiography (3D CE MRA) with parallel imaging techniques for the diagnosis of various arterial stenoses and its value for planning endovascular interventional treatment. Thirty-five patients underwent 3D CE MRA before endovascular interventional treatment. Numbers of patients were as follows: clinically documented renal artery stenosis (n = 10), renal transplant artery stenosis (n = 1), carotid artery stenosis (n = 12), iliac artery stenosis (n = 11) and femoro-popliteal artery stenosis (n = 1). A total of 39 arterial segments were treated. The depiction of various arterial stenoses was evaluated. The degree and length of the stenoses were compared and analyzed between 3D CE MRA and digital subtraction angiography (DSA). The accuracy of MRA in depicting lesion characteristics (ulceration, eccentricity, post-stenotic dilatation) was reviewed. The overall value of 3D CE MRA in planning interventional treatment was determined. The quality of 3D CE MRA in the demonstration of various arterial stenoses was judged excellent or good. A strong correlation was noted between 3D CE MRA and DSA regarding severity and length of stenosis. The accuracy of 3D CE MRA in depicting lesion characteristics was good. 3D CE MRA overestimated three severe iliac artery stenoses. Except in these three segments, the value of 3D CE MRA analysis was judged high. 3D CE MRA was found to be better than DSA in revealing the distal reconstitution and occluded segment in cases of iliac artery stenosis. 3D CE MRA is accurate in demonstrating the relevant anatomy necessary to plan endovascular interventional treatment for patients with arterial stenosis.

Peripheral Vasculature: High-Temporal- and High-Spatial-Resolution Three-dimensional Contrast-enhanced MR Angiography

To prospectively evaluate the feasibility of performing high-spatial-resolution (1-mm isotropic) time-resolved three-dimensional (3D) contrast material-enhanced magnetic resonance (MR) angiography of the peripheral vasculature with Cartesian acquisition with projection-reconstruction-like sampling (CAPR) and eightfold accelerated two-dimensional (2D) sensitivity encoding (SENSE). All studies were approved by the institutional review board and were HIPAA compliant; written informed consent was obtained from all participants. There were 13 volunteers (mean age, 41.9; range, 27-53 years). The CAPR sequence was adapted to provide 1-mm isotropic spatial resolution and a 5-second frame time. Use of different receiver coil element sizes for those placed on the anterior-to-posterior versus left-to-right sides of the field of view reduced signal-to-noise ratio loss due to acceleration. Results from eight volunteers were rated independently by two radiologists according to prominence of artifact, arterial to venous separation, vessel sharpness, continuity of arterial signal intensity in major arteries (anterior and posterior tibial, peroneal), demarcation of origin of major arteries, and overall diagnostic image quality. MR angiographic results in two patients with peripheral vascular disease were compared with their results at computed tomographic angiography. The sequence exhibited no image artifact adversely affecting diagnostic image quality. Temporal resolution was evaluated to be sufficient in all cases, even with known rapid arterial to venous transit. The vessels were graded to have excellent sharpness, continuity, and demarcation of the origins of the major arteries. Distal muscular branches and the communicating and perforating arteries were routinely seen. Excellent diagnostic quality rating was given for 15 (94%) of 16 evaluations. The feasibility of performing high-diagnostic-quality time-resolved 3D contrast-enhanced MR angiography of the peripheral vasculature by using CAPR and eightfold accelerated 2D SENSE has been demonstrated.

Optimized time-resolved 3D contrast-enhanced MRA at 3T: Appreciating the feasibility of assessing cervical paragangliomas

To describe an optimized 3D time-resolved contrast-enhanced MR angiography (3D TR-CE-MRA) at 3T in diagnosing head and neck paragangliomas and assessing their morphology and relation to neighboring vessels. In a prospective study, eight consecutive patients presenting cranial cervical masses suspected to be 10 paragangliomas were examined with 3D TR-CE-MRA at 3T. Two neuroradiologists evaluated the overall image quality, the presence of a paraganglioma, the maximum diameter, as well as the vessel invasion. In all of the cases, the overall image quality was scored as good. The tumors (n=10) were all visualized and localized. The mean maximum diameter was 32.7mm [range 7-80]. Vessel invasion was assessed as uncertain in one case and improbable in nine cases. 3D TR-CE-MRA at 3T associated with conventional sequences facilitates a comprehensive investigation of paragangliomas, thus providing the anatomical and functional information.

A free-breathing non-contrast-enhanced pulmonary magnetic resonance angiography at 3 Tesla.

The breathhold contrast-enhanced three-dimensional magnetic resonance angiography (MRA) using T1-weighted gradient-echo imaging sequence is the standard technique for MRA of the thorax. However, this technique is not desirable for certain patients with respiratory insufficiency, serious renal impairment, or allergy to contrast agents. The objective of this study was to optimize and evaluate a non-contrast-enhanced free-breathing pulmonary MRA protocol at 3 Tesla. The time-of-flight protocol was based on a two-dimensional T1-weighted turbo field echo sequence with slice-selective inversion recovery and magnetization transfer preparation together with respiratory navigator gating, cardiac gating, and parallel imaging. Optimal values for time of inversion delay, flip angle and slice thickness were experimentally determined and used for all subjects. Excellent pulmonary MRA images, in which the 7th order branches of pulmonary arteries could be reliably identified, were obtained in the 12 free-breathing healthy volunteers. TI of approximately 300 ms provides the best suppression of background thoracic and cardiac muscles and effective inflow enhancement. With increasing flip angle, the pulmonary vessels gradually brightened and exhibited optimal contrast at 20 degrees-30 degrees. The 2 mm slice thickness and 0.5 mm slice overlap is suitable for visualization of the peripheral pulmonary vessel. The MRA protocol at 3 Tesla may have clinical significance for pulmonary vascular imaging in patients who are not available for contrast-enhanced 3D MRA and CT angiography examination or are unable to sustain a long breath-hold.

Rare pattern of aortic arch branching in a patient with operated congenital heart disease

Magnetic resonance imaging (MRI) has become one of the state-of-the-art examinations for the primary diagnostics and follow-up of patients with congenital cardiac defects. The evaluation of the altered cardiovascular system, however, remains a diagnostic challenge. We present MRI findings in a boy with a complex congenital heart defect. To reveal postoperative changes in blood flow dynamics, time-resolved contrast-enhanced 3D MR angiography (CE-MRA) was performed, providing information on altered vessel anatomy and vascular dynamics using spatio-temporal image acceleration. Additionally, an exceptional and rarely described supraaortic vessel variation was detected, consisting of five independent supraaortic arteries. The knowledge of this unusual vessel anomaly detected by CE-MRA might be significant in the case of future therapeutic interventions.

The role of time-resolved 3D contrast-enhanced MR angiography in the assessment and grading of cerebral arteriovenous malformations

Purpose To assess the role of three-dimensional (3D) contrast-enhanced, time-resolved MR angiography (CE TR MRA) in patients with intracranial arteriovenous malformations (AVMs). Methods We studied 12 patient with intracranial AVMs on a 3.0 T MR imaging system (Magentom TIM Trio, Siemens Medical Solutions, Erlangen, Germany) using 3D CE TR MRA with autocalibrating partially parallel acquisitions and echo sharing schemes, which provided temporal resolution of 0.58 or 1.7 s and near isotropic voxels. We qualitatively assessed image quality of the 3D CE TR MRA and compared the grading of the AVMs based on modified Spetzler–Martin system for 3D CE TR MRA and catheter digital subtraction angiography (DSA). Results CE TR MRA provided good quality images in the 3 standard orthogonal planes, and good arterial-venous separation in all cases. All AVMs were correctly graded by CE TR MRA when compared with DSA. 3D CE TR MRA provides a non-invasive alternative to DSA for the evaluation of cerebral AVMs.

Unmasking pedal arteries in patients with critical ischemia using time-resolved contrast-enhanced 3D MRA

To test the diagnostic relevance of fast Gadobenate dimeglumine (Gd-BOPTA) enhanced, time-resolved, three-dimensional magnetic resonance angiography (t3D MRA) of distal calf and pedal vasculature in critical limb ischemia in a prospective comparison with conventional selective digital subtraction angiography (DSA) and high-resolution duplex ultrasound (US) scan. From April 2007 to June 2008, 34 feet of 29 consecutive patients suffering from limb-threatening ischemia underwent diagnostic US scan, DSA, and t3D MRA before treatment. The investigations took place within 3 days. A t3D MRA was performed using a 3 Tesla whole-body magnetic resonance (MR) system with an eight-element phased-array coil. Image quality and diagnostic findings were subjectively analyzed by two radiologists and one vascular surgeon. Each distal calf and foot was divided into six arterial segments for DSA and t3D MRA, and four segments were investigated by US scan. Patency or occlusion was studied with all the techniques, whereby DSA and t3D MRA were additionally evaluated in patients having greater or less than 50% stenosis. Finally, images were visually assessed by the three observers by applying a six-point grading scale. The acquired data was statistically analyzed using McNemar's test and Wilcoxon's matched-pairs signed-rank sum test. The P values of less than an alpha level of .05 were considered to be statistically significant. We achieved MRA images of diagnostic quality in all patients. Significantly more patent pedal arteries were identified by applying t3D MRA than DSA (P < .001) and US scan (P < .02). For estimating the degree of stenosis, no technique proved to be superior (P > .28). Overall image quality was rated best for t3D MRA. Additionally, potential bypass target vessels could be clearly discriminated from pedal veins due to the temporal resolution. In our prospective study, t3D MRA has been proven to be superior to DSA and US scan in pedal vasculature imaging in critical limb ischemia. This is a valuable, noninvasive method for detecting potential pedal bypass target arteries.

Contrast enhanced MR angiography with parallel imaging in the early period after renal transplantation

To evaluate renal allograft vessels in the early period after kidney transplantation with three-dimensional (3D) contrast-enhanced MR angiography (3D CE MRA) using a parallel imaging technique. Sixty-three consecutive patients were examined with 3D CE MRA and integrated SENSE technique (Sensitivity Encoding) 2 to 21 days after renal transplantation. MR angiography studies were analyzed for the presence of arterial stenosis. The degree of renal transplant artery stenosis was graded qualitatively as <50% = mild, 50-70% = moderate, 70-99% = severe, and occlusion. Four patients (6.3%) with moderate (n = 1) or severe (n = 3) arterial stenoses on CE MRA underwent selective intra-arterial digital subtraction angiography. In two patients, selective intravenous digital subtraction angiography (DSA) was performed. Twenty-seven (42.9%) of the 63 patients had normal CE MR angiograms, 29 (46%) showed mild, 3 patients (4.8%) moderate, and 4 patients (6.3%) severe stenoses of the donor artery. In three patients, the severe stenosis of the graft artery was confirmed by surgery or intra-arterial DSA. One patient with suspicion of severe arterial stenosis on MRA had moderate vessel narrowing on DSA. Twelve months after kidney transplantation, serum creatinine levels were not significantly different in patients with mild and moderate stenoses from those without (P > 0.19) but significantly different from those with severe stenoses (P < 0.05). The incidence of mild and moderate vessel narrowing at the arterial anastomosis is unexpectedly high in the early period after kidney transplantation and is most likely due to surgery-related tissue edema.

Seguimiento mediante angio-resonancia magnética de aneurismas cerebrales embolizados: concordancia entre lectores

Objective To determine the interobserver agreement in the interpretation of MR angiography (MRA) studies for surveillance of embolized intracranial aneurysms. To determine whether contrast administration improves interobserver agreement. Material and methods Two experienced neuroradiologists independently reviewed all follow-up MRA studies performed between July 2004 and December 2006 of cerebral aneurysms embolized with coils. All MRA studies included both unenhanced 3D time-of-flight (3D TOF) and contrast-enhanced MRA (CE-MRA) images. Studies were classified as: a) not assessable; b) complete occlusion; c) residual aneurysm. Interobserver agreement for unenhanced and enhanced MRA studies was determined using the kappa statistic. Kappa values were considered insignificant when<0.2, low when between 0.21 and 0.4, and moderate when between 0.41–0.6; values >0.6 were considered good agreement and >0.8 excellent agreement. Significance was set at p<0.005. Results We reviewed a total of 200 MRA studies (100 3D TOF studies and 100 CE-MRA studies) performed in 48 patients (25 women, 23 men) at 6, 12, and/or 24 months after embolization. Interobserver agreement was good in both 3D TOF and CE-MRA studies, although it was better in CE-MRA studies (κ=0.660, p<0.001 and κ=0.779, p<0.001, respectively). Conclusions Interobserver agreement is good for follow-up MRA studies of embolized intracranial aneurysms. Gadolinium administration improves interobserver agreement.

Assessment of arteriovenous malformations with 3-Tesla time-resolved, contrast-enhanced, three-dimensional magnetic resonance angiography

Although conventional catheter angiography is commonly used in the evaluation of intracranial arteriovenous malformations (AVMs), less invasive tools are more suitable for screening or follow-up. Older MR angiography techniques cannot provide high enough temporal and spatial resolution for assessing AVMs. Threetesla time-resolved imaging of contrast kinetics (TRICKS)-a time-resolved, contrast-enhanced 3D MR angiography technique-achieves subsecond time resolution without sacrificing spatial resolution. The purpose of this study was to assess the accuracy of TRICKS at 3 T in the evaluation of AVMs. Between November 2006 and November 2007, 31 patients who were known to have AVMs underwent evaluation in a 3-T unit with the TRICKS technique. The TRICKS images were then evaluated independently by 2 radiologists for nidus detection, early venous filling detection, and Spetzler-Martin classification, and these results were compared with the results of catheter angiography. Time-resolved imaging of contrast kinetics achieved 96% sensitivity and 100% specificity both in nidus detection and early venous filling detection. The Spetzler-Martin grades also showed excellent correlation with catheter angiography findings (kappa= 0.89). Although this is a preliminary study, the authors' results indicate that time-resolved contrast-enhanced 3D MR angiography at 3 T is a good tool to assess AVMs, and has the potential to replace catheter angiography in screening or follow-up examinations of patients with AVMs.