Mathias Goyen

Rapid magnetic resonance angiography for detection of atherosclerosis

BACKGROUND Choice of treatment for atherosclerosis depends on various clinical factors and radiological techniques. We aimed to assess the diagnostic accuracy of a new three-dimensional magnetic resonance angiography (3D MRA) strategy for the display of arterial vasculature from supra-aortic arteries to distal runoff vessels in 72 s. METHODS We examined five healthy volunteers and six patients over 6 weeks. Conventional digital subtraction angiography (DSA) was available as reference standard in all six patients. Magnetic resonance imaging was done on a commercially available 1.5 Tesla scanner. The imaging technique was based on the acquisition of five 3D data sets in rapid succession with an optimum single injection protocol. FINDINGS Compared with conventional catheter angiography, according to the findings of two independent and masked readers, whole-body MRA had overall sensitivities of 91% (95% CI 0.76-0.98) and 94% (0.8-0.99), and specificities of 93% (0.85-0.97) and 90% (0.82-0.96) for the detection of substantial vascular disease (luminal narrowing >50%), interobserver agreement for assessment of whole-body magnetic angiograms was very good (kappa=0.94; 95% CI 0.9-0.98). INTERPRETATION The technique provides a comprehensive non-invasive approach for morphological screening assessment of the arterial vasculature from supra-aortic arteries to the distal runoff arteries.

Dynamic 3D MR angiography of the pulmonary arteries in under four seconds.

Although 3D MRA has been shown to provide excellent depiction of the pulmonary arterial tree, its clinical use has been limited due to lengthy breath‐holding requirements. Employing the newest gradient generation (1.5 T MR system, amplitude of 40 mT/m and a slew rate of 200 mT/m/msec), we evaluated a technique permitting the dynamic acquisition of 3D data sets of the entire pulmonary tree in under 4 seconds. Coronal image sets were collected using a repetition time of 1.64 msec and an echo time of 0.6 msec, resulting in an acquisition time of 3.74 seconds. Three volunteers and eight dyspneic patients with known or suspected pulmonary embolism underwent MRI of the pulmonary arteries. The pulmonary arterial tree was visible to a subsegmental level in all examined subjects. Regarding the presence of pulmonary emboli in four patients, there was complete concordance between MR angiographic findings and those of corroborative studies. We conclude that diagnostic MRA of the pulmonary vasculature can be obtained even in patients with severe respiratory distress. J. Magn. Reson. Imaging 2001;13:372–377.

0.5 M Gd chelate (Magnevist®) versus 1.0 M Gd chelate (Gadovist®): Dose-independent effect on image quality of pelvic three-dimensional MR-angiography

To compare the effect on image quality of a 1.0 M gadolinium (Gd) chelate to that of a conventional 0.5 M Gd chelate, five healthy volunteers and seven patients with angiographically documented aorto‐iliac disease underwent a mono‐station three‐dimensional magnetic resonance angiography (MRA) exam (Siemens SONATA®, Erlangen, Germany) twice, once using Gadovist® 1.0 and the other time using Magnevist® as the contrast agent. All subjects received a fixed volume of Gadovist® 1.0, corresponding to a dose between 0.1 and 0.15 mmol/kg body weight followed by a saline flush. For the Magnevist® exam, the contrast agent volumes and flow rates were doubled. For both quantitative and qualitative analysis of the angiographic data sets, the arterial tree was divided into nine segments. 1 M Gadovist® 1.0‐enhanced three‐dimensional MRA data sets were characterized by significantly higher signal‐to‐noise ratio (SNR) and contrast‐to‐noise ratio (CNR) values compared to 0.5 M Magnevist®‐enhanced images. The data revealed mean SNR/CNR increases exceeding 70% (P < 0.01). Although there was no statistically significant difference in the rating of image quality (P > 0.05), the Gadovist® 1.0 exam led to better delineation of the arterial morphology, especially of small vessels. J. Magn. Reson. Imaging 2001;14:602–607.

Interventional therapy of vascular complications caused by the hemostatic puncture closure device Angio‐Seal

The hemostatic puncture closure device Angio‐Seal is a quick, safe, and easy‐to‐use system, allowing rapid sealing of the vascular access site following coronary angiography and interventional procedures. It is advantageous for patients in whom early mobilization is desired and may therefore decrease hospital costs. Despite the documented low complication rate, there are some specific problems. Reporting on five cases, we describe problems in diagnosis and possible interventional therapy of Angio‐Seal–associated complications such as stenosis, occlusion, or peripheral embolism. Our experience led to the concept of precise diagnosis in any patient with leg symptoms and early interventional treatment with the aim of complete removal of the intra‐arterial parts of the Angio‐Seal device. Any delay in diagnosis and treatment increases the risk of additional thrombotic occlusion. Spontaneous dissolution of the Angio‐Seal sponge limits interventional possibilities of complete removal. Cathet. Cardiovasc. Intervent. 49:142–147, 2000.

Using a 1 M Gd-chelate (gadobutrol) for total-body three-dimensional MR angiography: Preliminary experience

To determine whether higher concentrated gadolinium chelates are advantageous for the recently introduced concept of total‐body magnetic resonance angiography (MRA), allowing whole‐body coverage, extending from the carotid arteries to the runoff vessels, in merely 72 seconds.

Total-body 3D magnetic resonance angiography influences the management of patients with peripheral arterial occlusive disease

High-resolution total-body 3D MR angiography (MRA) has recently become available, revealing additional clinically relevant disease in patients with peripheral arterial occlusive disease (PAOD). However, the actual impact of total-body MRA on patient management in patients with PAOD has not been investigated so far. Two hundred forty-nine consecutive patients with angiographically proven PAOD were prospectively examined by means of contrast-enhanced total-body 3D MRA on a 1.5-T MR scanner. All correlative imaging studies performed within 60 days of total-body MRA were included in the efficacy analysis. Additional clinically relevant disease (luminal narrowing >50%, aneurysmal changes or dissections) was found in 73 segments (52 patients), including the renal arteries (36 segments), carotid arteries (28 segments), subclavian arteries (four segments) and abdominal aortic aneurysms (AAA) (five segments). Of the 73 segments, 36 were deemed necessary for further investigation by means of focused MRA examinations; the diagnosis was confirmed in all cases. Within the 60-day follow-up period, interventional or surgical therapy outside the peripheral arterial tree was performed in nine patients (11 segments), including carotid endatherectomy and renal artery angioplasty. The outlined total-body 3D MRA approach permits a comprehensive evaluation of the arterial system in patients with atherosclerosis and does indeed have an impact on patient management in patients with PAOD.

Biomechanical Incompatibility of Popliteal Stent Placement

Peripheral stents or endografts in specific arterial segments are exposed to extreme mechanical stress. Despite high rates of primary technical success, mechanical bending due to knee joint flexion can limit long-term patency of stents or endografts in the popliteal artery or the femoropopliteal segment. Every stent or endograft responds differently to bending during knee joint flexion, which can be revealed only by functional investigation. Mechanical bending has to be considered in future studies to assess the influence of differences in stent design, material, or postinterventional drug treatment on the long-term patency of endoprostheses in the femoropopliteal segment. To demonstrate the concept of biomechanical incompatibility, we present several illustrations of different stent designs placed in the popliteal artery.

Improved multi‐station peripheral MR angiography with a dedicated vascular coil

Delineation of small branch vessels can be crucial for assessing the peripheral arterial system of patients requiring surgical grafting. Thus signal‐to‐noise needs to be maximized. We evaluated the performance of a dedicated peripheral vascular coil in four subjects by comparing it to the body coil using DSA as the standard of reference. SNR and CNR values of the dedicated peripheral coil exceeded those obtained with the body coil by a mean of 398%, thus permitting improved delineation of the infrapopliteal arterial morphology. J. Magn. Reson. Imaging 2001;13:475–480.

Small bowel hydro-MR imaging for optimized ileocecal distension in Crohn's disease: Should an additional rectal enema filling be performed?

To assess the impact of an additional rectal enema filling in small bowel hydro‐MRI in patients with Crohns disease.

MR-angiography: the role of contrast agents

Contrast-enhanced 3D MR angiography (MRA) permits comprehensive assessment of the supraaortic arteries as well as the arterial system in the chest, abdomen and lower extremities. 3D MRA combines intravenous injection of a non-nephrotoxic, paramagnetic, extracellular contrast agent that increases the signal intensity of blood by shortening its T1 value with the acquisition of a fast 3D data set. High contrast between the vascular lumen and surrounding tissues, inherent three-dimensionality and the ability to collect image data in the chest and abdomen under apnea conditions all contribute to excellent image quality. This review provides clinical applications of 3D MRA in the chest, abdomen and lower extremities based upon the available literature and several clinical examples.