MR imaging of aortic coarctation.

Aortic coarctation accounts for 5%-10% of all congenital heart diseases and represents 7% of critically ill infants with heart disease. Magnetic resonance (MR) imaging allows the study of this disease with several advantages in comparison with conventional angiography, transesophageal echocardiography, and computed tomography. The MR protocol applied at our institution for both diagnosis and follow-up after surgical or endovascular treatment consists of four steps: morphologic study, cine MR study, flow analysis, and MR angiography (MRA). The first three sequences are acquired during breath-hold and with electrocardiographic gating. Anatomy is well depicted with dark-blood half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences. Cine true-fast imaging with steady-state precession (true-FISP) sequences show not only morphologic features but also blood-flow changes inside the aorta. Gradient-echo sequences for phase-velocity mapping allow flow analysis. Application of Bernoulli's equation--here briefly presented and discussed--allows for calculation of the pressure gradient caused by the coarctation. MRA, acquired with a breath-hold three-dimensional T1-weighted gradient-echo sequence and intravenous administration of paramagnetic contrast material, allows for optimal depiction of the aortic lumen, with a panoramic view of the whole aorta, its main branches and possible collateral circulation.

The value of chemical fat-saturation pulse added to T1-weighted spin-echo sequence in evaluating gadolinium-enhancing brain lesions in multiple sclerosis.

PURPOSE: This study was undertaken to assess the value of a chemical (spectral) fat-saturation (fat-sat) pulse added to a T1-weighted spin-echo sequence after intravenous administration of paramagnetic contrast agent in detecting enhancing lesions in multiple sclerosis. MATERIALS AND METHODS: Twenty patients with relapsing-remitting multiple sclerosis underwent a brain 1.0-Tesla magnetic resonance (MR) scan with T1-weighted spin-echo sequences (24 contiguous para-axial slices with a thickness of 5 mm, pixel size 0.96 mm(2), number of excitations 2, flip angle 90 degrees ) 5 min after intravenous injection of 0.1 mmol/kg of gadodiamide with and without fat-sat, acquired with randomised order of priority. Two readers counted by consensus the number of enhancing lesions and assigned a conspicuity score (low conspicuity=1; high conspicuity=2) to each enhancing lesion during a randomised reading without any visual comparison between the two corresponding images (with and without fat-sat) of the same patient. McNemar and Wilcoxon matched-pair signed-rank tests were used. RESULTS: Seventy-two enhancing lesions without fat-sat and 94 with fat-sat were detected; 22 lesions were visible only with fat-sat, whereas no lesion was detected only without fat-sat (p<0.0001). The conspicuity score was 1.17+/-0.38 (mean+/-standard deviation) and 1.57+/-0.44, respectively (p<0.0001). CONCLUSIONS: A fat-sat pulse added to a T1-weighted spin-echo sequence increases significantly the number and conspicuity of contrast-enhancing lesions in patients with relapsing-remitting multiple sclerosis.

White matter hyperintensities on brain magnetic resonance in systemic sclerosis.

OBJECTIVE: To evaluate the brain status of patients with systemic sclerosis (SSc). METHODS: Fourteen female patients with SSc aged 24-74, with a disease duration of 1-12 years and without other relevant systemic diseases, were enrolled. All patients and an age matched female control group (CG) of 14 clinically normal subjects, underwent brain magnetic resonance examination at 1.5 T; spin echo proton density weighted images were evaluated. Mann-Whitney U and Spearman rank correlation tests were used for statistical analysis. RESULTS: 170 white matter hyperintensities >/=2 mm in diameter were counted in the patient group (range 0-75, mean 12.1, median 4.5), only 13 in the CG (0-2, 0.9, 1, respectively), with a significant difference (p = 0.011). Moreover, 208 white matter hyperintensities <2 mm were found in the patient group (0-38, 14.9, 8, respectively), only 31 in the CG (0-7, 2.0, 1, respectively), with a significant difference (p = 0.006). No statistically significant correlation between the number of hyperintensities and either patient's age or disease duration was observed. CONCLUSION: White matter hyperintensities are more common in patients with SSc than in a CG. These findings might be related to obliterative microvascular processes due to the disease. Early brain involvement in patients with SSc may occur.

Evaluation of Gd-enhancement in brain MR of multiple sclerosis: image subtraction with and without magnetization transfer.

The aim of our study was to test the possibility of using image subtraction in detecting enhancing lesions in brain MR scans with and without magnetization transfer (MT) in multiple sclerosis (MS). Ten MS patients underwent 1.5-T MR imaging of the brain with spin-echo T1-weighted sequences with and without MT, repeated after 0.1 mmol/kg of an usual two-compartment paramagnetic contrast agent (Gadoteridol, Gd-HP-DO3A). Precontrast images were subtracted from postcontrast. Enhancing lesions were counted on the postcontrast images only (post-Gd), comparing pre- and postcontrast images by direct visual control (pre/post-Gd), and on the subtracted images (SI) only. Without MT, 36 enhancing lesions were counted on post-Gd, 36 on pre/post-Gd, and 59 on SI; using MT, 69, 52, and 50, respectively. Significant differences were found for pre/post-Gd without MT vs SI without MT ( p=0.028) and vs pre/post-Gd with MT ( p=0.012) as well as for pre/post-Gd with MT vs post-Gd with MT ( p=0.028). With pre/post-Gd, MT allowed the detection of 1.6 enhancing lesions per patient more than without MT. Whereas the SI without MT allow the detection of an increased number of enhancing lesions, SI with MT do not. An off-site final assessment allowed calculation of sensitivity and positive predictive value as follows: without MT were 63 and 94% (post-Gd), 67 and 100% (pre/post-Gd), 96 and 88% (SI); and with MT were 93 and 73% (post-Gd), 96 and 100% (pre/post-Gd), 91 and 98% (SI), respectively. Thus, SI seem to increase the sensitivity without MT; moreover, they could be used to correct the pseudoenhancement that impair post-Gd images with MT.

MR evaluation of coronary stents with navigator echo and breath-hold cine gradient-echo techniques.

The aim of this study was to evaluate coronary artery stents with MR. Thirty-eight patients underwent MR imaging 48.1 +/- 6.6 days (range 38-60 days) after placement of 47 coronary stents of 11 different types, using navigator echo (NE) and cine gradient-echo (GE) techniques. For both sequences the low signal artifact was used to localize the stent, whereas the flow-related high signal before and distal to the stent was considered as a patency sign. Exercise electrocardiographic test (EET) had been performed 1-7 days before MR. No adverse event with possible relation to the MR examination was observed. All the stents were recognized as signal void with GE, and all but one with NE. Of the 2 patients with positive EET, the first one, with a stent on the left anterior descending coronary artery, presented low signal distal to the stent at both MR sequences, suggesting dysfunction [60% stenosis at conventional coronary angiography (CCA)]; the second one, with two sequential stents on the right coronary artery, presented lack of signal distal to the stents at both MR sequences, suggesting occlusion (97% stenosis at CCA). For the 44 remaining stents in 36 patients with negative EET, MR high signal before and distal to the stent suggested patency at both sequences. MR seems to be a safe and promising technique for non-invasive evaluation of coronary stents.

Contrast agents and temporal resolution in breast MR imaging.

The article summarizes the technique of dynamic Gd-enhanced breast magnetic resonance (MR) imaging and the established clinical indications to this examination. The main features of the four different non-selective Gd-chelates today available for contrast-enhanced MR breast imaging are described. Their typical two-compartment (vascular/interstitial) distribution is related to the temporal resolution used for the MR acquisition; the gain in specificity obtained increasing the temporal resolution during the first phase after the contrast intravenous injection (using both, rapid T1-weighted sequences or ultrafast T2*-weighted perfusion imaging) is discussed. Moreover, a survey of new contrast agents is supplied, including a high T1-relaxivity Gd-chelate, blood pool agents, and lymph node targeted agents. In conclusion, future directions are delineated.

[An evaluation of orthotopic ileal neobladders by dynamic digital urography]. / Valutazione delle neovesciche ileali ortotopiche mediante urografia digitale dinamica.

PURPOSE: To report on the diagnostic capabilities of dynamic digital urography in the evaluation of orthotopic ileal neobladders. MATERIAL AND METHODS: Ten male patients (aged 61.3 +/- 14.7 years) with orthotopic ileal neobladder (4 Studer, 4 Camey type II with spiralized ileal segment and 2 classic Camey type II) underwent dynamic digital urography using an angiographic unit (Philips DVI/ARC-A). Eight patients were asymptomatic and two presented mild nycturia. All patients should have undergone follow-up conventional urography, which was replaced, for the purposes of our study, by dynamic digital urography. The intestinal cleansing regimen usual for the double contrast barium enema was used in all the patients. Ninety mL of a nonionic iodinated contrast agent were administered i.v. with an automatic injector. After precontrast mask images, two postcontrast sequences were acquired 15 s and 30 min after the injection (each made of 20 images acquired every 10 seconds). Postprocessing consisted of digital image subtraction and videorecording. RESULTS: Renal pelvis and calyceal systems were well visualized in 18/20 excretory systems. Eighteen of 20 ureters were visualized completely up to the ureteral jet, and two were only partially visualized. Calyceal, pyelic and ureteral enlargement with ureteral kinking were observed in a patient with classic Camey type II. High motility was seen in 11 ureters, moderate in 5 and mild in 4. The orthotopic ileal neobladder was well opacified in 8/10 patients. Effective peristalsis of the afferent ileal segment was seen in all the Studer type neobladders. Ureteral reflux was not observed in any patient. DISCUSSION: After orthotopic ileal neobladder reconstruction, the most frequent complications include urinary leakage, intestinal obstruction, venous thrombosis, stenosis of the neobladder anastomoses, incontinence, cancer recurrence, stone formation. In the follow-up, many diagnostic tools are used: intravenous urography, retrograde cystography, urodynamic studies, transabdominal and transrectal ultrasonography. With dynamic digital urography the nephrographic evaluation was possible in all patients, as well as the evaluation of calyceal, pyelic and ureteral opacification and even ureteral peristalsis. Moreover, this diagnostic tool allows the morphofunctional dynamic study of the ureteral-neobladder anastomoses and of the orthotopic ileal neobladder, even evaluating the residual peristalsis of the detubularized ileal segment. A major drawback of the new method is the relatively high radiation dose given to the patient. A limitation of the study is the selection of a population of completely or nearly asymptomatic patients. CONCLUSIONS: Dynamic digital urography provides useful morphologic and functional information in the follow-up of patients with orthotopic ileal neobladder and could replace conventional urography in symptomatic patients.