Single-dose breath-hold gadolinium-enhanced three-dimensional MR angiography of the renal arteries

PURPOSE: To evaluate the quality of single-dose breath-hold three-dimensional (3D) magnetic resonance (MR) angiography of the renal arteries optimized with a 1-mL test bolus timing examination. MATERIALS AND METHODS: Three-dimensional spoiled gradient-echo imaging (3.8-4.2/1.3-1.7 [repetition time msec/echo time msec], 25 degrees-40 degrees flip angle) was performed in 60 patients after administration of gadopentetate dimeglumine (average dose, 0.11 mmol/kg). Synchronization of contrast material administration with data acquisition was achieved with a 1-mL test dose of contrast material to estimate patient circulation parameters. Image quality was assessed by using contrast-to-noise (CNR), relative vascular enhancement, and venous-to-arterial enhancement ratios and subjective scoring of arterial and venous enhancement. The effect of the contrast material injection rate and the influence of breath holding during the timing examination also were examined. RESULTS: Overall, of 60 studies, 58 were diagnostic and 56 demonstrated excellent arterial enhancement. Venous enhancement was seen in eight studies. The average aortic relative vascular enhancement (+/- SD) was 14.6 +/- 5.9, with an aorta-to-inferior vena cava (IVC) CNR of 69.7 +/- 43.9. The IVC-to-aorta venous-to-arterial enhancement ratio averaged 0.08 +/- 0.16. There was no significant difference in image quality based on injection rates or the performance of breath holding during the timing examination (P > .1). CONCLUSION: Breath-hold gadolinium-enhanced renal MR angiography free of venous enhancement can be performed consistently and reliably with 20 mL of contrast material when studies are synchronized to patient circulation time by using a timing examination.     

Coronary arteries: MR angiography with fast contrast-enhanced three-dimensional breath-hold imaging--initial experience

Gadolinium-enhanced, three-dimensional, breath-hold magnetic resonance (MR) coronary angiography was performed in two healthy volunteers and 11 patients suspected or known to have coronary artery disease. MR angiograms were compared with those obtained with retrospective respiratory gating. Of 52 main coronary arteries, 47 could be visualized with the breath-hold technique and 49 with the gating technique. Signal-to-noise and contrast-to-noise ratios were significantly higher with the breath-hold technique. Overall image quality was slightly lower with breath-hold imaging. With either technique, three of five, significant coronary stenoses were correctly identified.     

Renal artery stenosis: evaluation with conventional angiography versus gadolinium-enhanced MR angiography

PURPOSE: To evaluate the interobserver and intermodality variability of conventional angiography and gadolinium-enhanced magnetic resonance (MR) angiography in the assessment of renal artery stenosis. MATERIALS AND METHODS: Fifty-four patients underwent conventional angiography and gadolinium-enhanced three-dimensional gradient-echo MR angiography. Three angiographers blinded to each other's interpretations and the MR angiographic findings assessed the conventional angiograms for renal artery stenosis. Similarly, three blinded MR imagers evaluated the MR angiograms. RESULTS: Interobserver variability for the degree of renal artery stenosis in the 107 kidneys evaluated was not significantly different between the two modalities. The mean SD of the degree of stenosis was 6.9% at MR angiography versus 7.5% at conventional angiography (alpha < or = .05, P > .05). In 70 kidneys (65%), the average degree of stenosis reported by the readers for the two modalities differed by 10% or less. In 22 cases (21%), the degree of stenosis was overestimated with MR angiography by more than 10% relative to the results of conventional angiography. In 15 cases (14%), the degree of stenosis was underestimated with MR angiography by more than 10%. CONCLUSION: Gadolinium-enhanced MR angiography permits evaluation of renal artery stenosis with an interobserver variability comparable with that of conventional angiography.     

Pelvic arteriovenous malformations: gadolinium-enhanced three-dimensional MR angiography findings

Pelvic arteriovenous malformations (PAVMs) are rare disorders traditionally diagnosed by conventional angiography. Breath-hold three-dimensional gadolinium-enhanced MR angiography (3D-Gd-MRA) is a state-of-the-art alternative for vascular imaging. We describe the 3D-Gd-MRA findings in two patients with PAVMs. The 3D-Gd-MRA approach provides a noninvasive and versatile method for evaluation of PAVMs that enables both angiographic assessment of the malformations and evaluation of visceral involvement, which can preclude surgical intervention. Received: 15 September 1999; Revised: 27 December 1999; Accepted: 27 December 1999     

Multi-detector row helical CT angiography of hepatic vessels: depiction with dual-arterial phase acquisition during single breath hold

PURPOSE: To determine by using multi-detector row computed tomography (CT), in a triphasic hepatic dynamic study, which included single breath-hold dual-arterial phase acquisition, the accuracy and frequency of visualization of the small hepatic arterial and portal venous anatomy with angiographic correlation. MATERIALS AND METHODS: In 62 patients, pre- and postcontrast triphasic helical CT were performed by using a multi-detector row CT scanner, with 2.5-mm detector row collimation, at a pitch of 6. The first and second arterial phases were performed during a single breath hold. One reader, blinded to the results of the angiography, reviewed the first arterial phase images on a cine display to assess hepatic arterial anatomy. Visualization of the portal vein and its branches was assessed by using second arterial and portal venous phase images. RESULTS: Major arterial trunks (celiac, hepatic, superior mesenteric, and left gastric) were depicted in all cases. Visualization of small arteries was as follows: right and left hepatic, 62 (100%) of 62; middle hepatic, 52 (87%) of 60; cystic, 47 (90%) of 52; right gastric, 50 (89%) of 56; and right and left inferior phrenic, 57 (92%) and 55 (89%) of 62, respectively. Subsegmental or more peripheral branches of the portal vein were depicted in 83% of cases during the second arterial phase and in 96% during the portal phase. There was no difference in degree of visualization in these two phases. CONCLUSION: Multi-detector row CT angiography was able to depict the hepatic vascular anatomy.     

三维辐射相位对比肾动脉各向同性高空间分辨力非增强MR成像

目的对一种新的三维(3D)辐射相位对比MR血管成像与对比剂增强MR血管成像在肾动脉解剖方面的应用进行前瞻性对照评价。材料与方法本研究符合HIPAA要     

Renal MR angiography at 1.0 T: three-dimensional (3D) phase-contrast techniques versus gadolinium-enhanced 3D fast low-angle shot breath-hold imaging.

OBJECTIVE: The purpose of this study was to evaluate the diagnostic usefulness of three different MR angiographic techniques at 1.0 T. SUBJECTS AND METHODS: In 22 patients with renal artery stenosis confirmed at intraarterial catheter angiography, we also performed unenhanced and gadolinium-enhanced three-dimensional phase-contrast MR angiography and gadolinium-enhanced single breath-hold three-dimensional fast low-angle shot MR angiography. We determined circulation time to optimize signal acquisition in gadolinium-enhanced breath-hold MR angiography after bolus injection of contrast material. RESULTS: Sensitivity, defined as the detection of a hemodynamically significant stenosis (>50% luminal narrowing), was 85% for enhanced phase-contrast MR angiography, 91% for gadolinium-enhanced MR angiography, and 95% for unenhanced phase-contrast MR angiography. The combination of unenhanced phase-contrast MR angiography and gadolinium-enhanced MR angiography yielded 100% sensitivity for hilar artery stenoses. There were 13 false-positive findings with unenhanced phase-contrast MR angiography, 10 with enhanced phase-contrast MR angiography, and four with gadolinium-enhanced MR angiography (specificity: 38%, 52%, and 79%, respectively). Accessory renal arteries were not seen on unenhanced or enhanced phase-contrast MR angiography (0/8 patients) but were detected with gadolinium-enhanced MR angiography in five of the eight patients. Interobserver agreement (kappa = .62) was best with gadolinium-enhanced MR angiography. The quality of the images was unsatisfactory for adequate evaluation of segmental renal arteries with all three MR angiographic techniques. CONCLUSION: A combination of unenhanced phase-contrast MR angiography and gadolinium-enhanced MR angiography at 1.0 T proved useful as a screening protocol for renal artery stenosis.     

Examination of susceptibility artifact in three-dimensional gadolinium-enhanced chest MR angiography

Signal loss that is sometimes found in the subclavian artery during chest MR angiography is thought to be caused by the susceptibility effect of highly concentrated contrast medium. In our research project, we examined the conditions under which signal loss occurs. We made vessel phantoms (artery phantom, vein phantom) that contained different concentrations of Gd-DTPA water solutions, and placed them in a 0.5 mmol/l Gd-DTPA water solution. We examined signal loss when the vein phantom was parallel to the magnetic field and when it was perpendicular to the magnetic field. We found that there was no signal loss in the artery phantom when the vein phantom was parallel to the magnetic field. In contrast, signal loss occurred in the artery phantom when the vein phantom was perpendicular to the magnetic field. The higher the concentration in the vein phantom, the closer the distance to the vessel phantom, and the longer the echo time (TE), the greater was the signal loss. Thus, the cause of signal loss in the subclavian artery was found to be the perpendicular orientation of the subclavian vein (through which the highly concentrated contrast medium flows) to the magnetic field. With the MRI devices currently in use, perpendicular orientation of the subclavian vein to the magnetic field cannot be avoided. Furthermore, the subclavian vein and subclavian artery are anatomically in close proximity to one another. These factors cause the susceptibility artifact, which is thought to result in signal loss in the subclavian artery.     

Nasolacrimal system: evaluation with gadolinium-enhanced MR dacryocystography with a three-dimensional fast spoiled gradient-recalled technique

The aim of this study was to determine the diagnostic accuracy of gadolinium-enhanced three-dimensional (3D) fast spoiled gradient-recalled (FSPGR) MR dacryocystography in patients with epiphora. Bilateral nasolacrimal systems of 19 patients suspected of having nasolacrimal canal obstruction were evaluated with MR dacryocystography. A sterile 0.9% NaCl solution containing 1:100 diluted gadolinium chelate was instilled into the bilateral conjunctival sacs of the patients. The 3D FSPGR sequence was used with 1.0-T scanner with the following parameters: TR 9.3 ms; TE 2 ms; flip angle 20; 256x224 matrix; 13- or 26-cm field of view; and 1-mm slice thickness. Seventeen patients had digital dacryocystography for comparison which we considered standard of reference. Thirty-four nasolacrimal systems were evaluated with MR and digital dacryocystography. Discrepancies between the findings of both methods were detected in 2 patients. The overall sensitivity of MR in detecting the obstruction was 100%. Magnetic resonance helped to determine the canalicular and ductal obstruction in 100% of the patients and the saccular obstruction in 80% of the patients. We conclude that 3D FSGR technique for MR dacryocystography is a reliable and noninvasive method in the evaluation of the obstruction level in the lacrimal system in patients with epiphora.