Renal artery stenosis (RAS) evaluation with Nonenhanced MR Angiography.

Transcription

1 Renal artery stenosis (RAS) evaluation with Nonenhanced MR Angiography. Poster No.: C-1329 Congress: ECR 2012 Type: Scientific Exhibit Authors: B. Corcioni, C. Gaudiano, F. Busato, M. G. Orrei, D. Valerio, R. Golfieri; Bologna/IT Keywords: Arteriosclerosis, Imaging sequences, Diagnostic procedure, Computer Applications-3D, MR-Angiography, MR, Vascular, Kidney, Arteries / Aorta DOI: /ecr2012/C-1329 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 21

2 Purpose The MR study of the renal arteries can be carried out by both contrast enhanced MR angiography (CE-MRA) and by non-enhanced MR Angiography. CE MR-Angiography is a high-resolution 3D T1-weighted sequence, obtained before, during and after the passage of contrast medium. It requires optimization of acquisition timing (test bolus techniques, Fluoro-RM, Bolus-Track, Figg. 1-3). Non-enhanced MR Angiography is performed by three-dimensional (3D) Fast Imaging Employing Steady-State Acquisition (FIESTA). It consists of Ultrafast Gradient Echo sequence (short TR and permanent transverse magnetization, MT). 3D FIESTA Sequence obtains high resolution images of structures containing fluids with shorter scan times than other conventional 3D sequences (very short TR and TE) with the possibility of reconstruction MPR, MIP and VR from each partition (Fig. 4-5). Nonenhanced MR Angiography allows faster, cheaper and less invasive examination than CE-MRA especially useful in patients with nephropathy. Aim of our study is to assess the accuracy of three-dimensional (3D) Fast Imaging Employing Steady-State Acquisition (FIESTA) in the detection and quantification of RAS. Page 2 of 21

3 Images for this section: Fig. 1: CE-MRA (Contrast Enhancement Magnetic Resonance Angiography. Highresolution sequence 3D T1-weighted, before, during and after the passage of contrast medium. It requires optimization of acquisition timing (test bolus techniques, Fluoro-RM, Bolus-Track. Page 3 of 21

4 Fig. 2: MIP reconstruction analysis. Page 4 of 21

5 Fig. 3: VR reconstruction analysis. Page 5 of 21

6 Fig. 4: 3D FIESTA (Fast Imaging Employing Steady-State Acquisition). a) Ultrafast Gradient Echo sequence (short TR and permanent transverse magnetization, MT) obtains high resolution images of structures containing fluids with shorter scan times than other conventional 3D sequences (very short TR and TE). b)individual partitions can be used to reconstruct MPR, MIP and VR. Page 6 of 21

7 Fig. 5: The curved reconstructions in the axial plane (a) and coronal images (b, c) of the 3D FIESTA enable the correct display of the vessel throughout its course and a thorough analysis of his caliber. Page 7 of 21

8 Methods and Materials Study Population From March 2010 to November 2011, seventy-seven patients (42 men and 35 females; years, mean age 53.5 years) with suspected RAS for the onset of hypertension or rapid impairment of renal function were prospectively evaluated with MRI. MRI protocol All exams were performed with a 16 channels 1.5T whole-body scanner (Signa HDxt; General Electric Company,Milwaukee,WI,USA) and a standard phased-array body-coil. The standard MRI protocol for kidney study, which was performed in all patients included: axial respirator-triggered single-shot fast spin-echo (SSFSE) T2-weighted sequence, axial breath-hold fast-spoiled gradient (FSPGR) T1-weighted sequence (double acquisition in/out of phase) and 2D coronal respiratory-triggered fast imaging employing steady-state acquisition (FIESTA) sequence. 3D FIESTA sequence in the axial plane and contrast-enhanced MR angiography (CEMRA) for evaluation of the renal arteries were performed. CEMRA was acquired during intravenous injection of a contrast bolus of 0.2 mmol per kilogram of body weight of Gadoterate meglumine (Dotarem, Guerbet S.A., Roissy, France), at flow rate of 2 ml/sec, followed by 20 ml of saline solution, by synchronizing with fluoro-trigger. Examination quality and stenosis grade of the renal artery in three defined segments (proximal, middle and distal) were defined. Patients with clinical indication to PTA (Percutaneous Transluminal Angioplasty) were evaluated with DSA (Digital Subtraction Angiography). Imaging Analysis Evaluation of the images was performed in consensus by two experienced radiologists (BC and CG). The presence of focal or diffuse parenchymal signal alteration, perirenal changes and collecting system alteration were also noted. Visualization and quantification of renal artery stenosis included: Location of the stenosis (proximal, middle, distal) Degree of stenosis (Tab 1): stenosis: 1 - (S / V) x 100 S: stenosis diameter Page 8 of 21

9 V: normal vessel diameter The evaluation included detection of vascular abnormalities (presence of accessory renal arteries). Statistical analysis Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 3D FIESTA were calculated with artery-by-artery and patient-by-patient analysis, using CE-MRA and DSA, when possible, as the reference standard. Page 9 of 21

10 Images for this section: Table 1: Degree of stenosis Page 10 of 21

11 Results In 48/77 (62%) patients, no RAS were detected; in 29/77 (38%) patients, RAS was present (bilateral in 14 patients, Fig. 6-7). Overall, 111/154 arteries had no stenosis and 43/154 arteries were judged stenotic on the basis of CE-MRA findings, with 30 significant stenosis (>50%, fig. 8). When compared with CE-MRA, sensitivity, specificity, PPV, and NPV of 3D FIESTA for RAS detection were: at artery-by-artery analysis, 90%, 100%, 100%, 81%; at patient-bypatient analysis, 91%, 100%, 100%, 75% (tab. 2). When compared with DSA, the corresponding values were 77%, 100%, 100%, 40% (Fig. 9 and tab. 3). In all patients a total of 17 accessory renal arteries were detected. 3D FIESTA showed 13/17 accessory arteries, while CE-MRA detected 13/17 accessory arteries: 4 were not visible by 3D FIESTA because they were outside the volume of study (emergency too low, Fig. 10) and another 4 were not detected by CE-MRA for reduced flow, including 1 with sub-occlusive stenosis of the origin (visible on 3D FIESTA, fig. 11). Page 11 of 21

12 Images for this section: Fig. 6: Bilateral RAS. Grade 4 on the right renal artery and grade 3 on the left renal artery with concordance between 3D FIESTA (a, b) and CE-MRA (c). 3D FIESTA well estimates even ostial plaque (c, see across). Page 12 of 21

13 Fig. 7: RAS grade 3. Same case of fig. 6, ostial plaque was treated with PTA. Fig. 8: Right RAS. Grade 4 both 3D FIESTA (a) that CE-MR (b). Slight underestimation of the 3D FIESTA compared to CE-MRA (80% vs. 95%). Page 13 of 21

14 Table 2: Results Page 14 of 21

15 Fig. 9: Right RAS. RAS grade 4, the same case of Fig.8, DSA (a) and PTA (b). Table 3: Comparison with DSA Page 15 of 21

16 Fig. 10: Accessory renal arteries, CE MRA. Accessory arteries are not visible on 3D FIESTA Images because not included in the study volume. Fig. 11: Accessory left renal artery is not visible due to low flow in the CE-MRA scans (a) and visible in the FIESTA (b). Page 16 of 21

17 Page 17 of 21

18 Conclusion In all cases FIESTA 3D images were of good quality, making possible an evaluation of the renal arteries with good confidence. The main advantages of 3D FIESTA images consist of: - speed and mini-invasive assessment - conspicuity and signal homogeneity of the vessel lumen - high delineation of the borders Both 3D FIESTA both CE-MRA cannot be used in the follow-up of patients with PTA and stenting for the magnetic susceptibility artifacts due to the presence of the stent (Fig 12). Non-enhanced MR Angiography with 3D FIESTA sequence showed good correlation with CE-MRA and may be a viable alternative to CEMRA for the detection of RAS, especially in cases of impaired renal function. We propose, therefore, the inclusion of the 3D FIESTA sequence in the study protocol of the renal arteries assessment. In positive/doubt cases the MR study can be easily completed by CE-MRA. However, the low VPN limits its widespread use as a screening tool. Page 18 of 21

19 Images for this section: Fig. 12: Bilateral PTA and stenting. Artifacts in 3D Fiesta (a, b) and CE MRA (C). Page 19 of 21

20 References Parienty I, Rostoker G, Jouniaux F, Piotin M, Admiraal-Behloul F, Miyazaki M. Renal artery stenosis evaluation in chronic kidney disease patients: nonenhanced time-spatial labeling inversion-pulse three-dimensional MR angiography with regulated breathing versus DSA. Radiology May;259(2): Liu X, Berg N, Sheehan J, Bi X, Weale P, Jerecic R, Carr J. Renal transplant: nonenhanced renal MR angiography with magnetization-prepared steady-state free precession. Radiology May;251(2): Lanzman RS, Voiculescu A, Walther C, Ringelstein A, Bi X, Schmitt P, Freitag SM, Won S, Scherer A, Blondin D. ECG-gated nonenhanced 3D steady-state free precession MR angiography in assessment of transplant renal arteries: comparison with DSA. Radiology Sep;252(3): Wyttenbach R, Braghetti A, Wyss M, Alerci M, Briner L, Santini P, Cozzi L, Di Valentino M, Katoh M, Marone C, Vock P, Gallino A Renal artery assessment with nonenhanced steady-state free precession versus contrast-enhanced MR angiography. Radiology Oct;245(1): Wilson G. J., Maki J. H. Non-Contrast-Enhanced MR Imaging of Renal Artery Stenosis at 1,5 Tesla. Magn Reson imaging of North America. 2009; 17(1): Page 20 of 21

21 Personal Information Page 21 of 21