Coarctation of the aorta.
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Aorta, Thoracic↗
Biomedical subjects
R Janka
Publications and source records attributed to R Janka.
[Fully automated floating table MR angiography of pelvic and leg arteries: initial clinical results].
The aim of this study was to obtain first clinical experiences with magnetic resonance angiography (MRA) with digital subtraction (MR-DSA) using an automatic floating table for visualization peripheral arteriosclerotic occlusive disease (paod). We examined 10 patients on a 1.5 T MR unit applying a fast MRA technique (3D FLASH) with intravenous application of positive contrast agent. MR-DSA examinations were compared with the gold standard intraarterial (i.a.) DSA. MR-DSA proved to be useful for routine application which could be performed sufficiently in all patients. MR-DSA and i.a. DSA showed comparable results for imaging of the pelvic and upper leg arteries. Looking at the thighs image quality of MR-DSA did not match the image quality of i.a. DSA in every case. This was due to venous overlap and in comparison to i.a. DSA reduced signal-to-noise ratios. However, clinical findings, obtained with MR-DSA, were sufficient for adequate therapy planning. Our preliminary results reveal the potential of this new technique to become a realistic, robust, and non-invasive alternative to i.a. DSA in the diagnosis of paod.
Aged↗
Dedicated phased-array coil for peripheral MRA.
In this paper we introduce a phased-array coil dedicated for MRA of peripheral arteries which covers the upper and lower legs. The structure of this coil includes a solid cabinet with four flexible wings forming a "T." The flexibility of the wings allows adaptation to the individual leg size. There are eight circularly polarized channels, four on each side. This coil is compatible with other surface coils. For MRA of peripheral arteries, it is combined with the body phased-array coil and the spine array coil which cover the lower abdomen and the pelvis. We examined six patients using this coil combination. The image quality, the signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of these examinations were compared with that of peripheral MRA examinations obtained with the body resonator. Image quality with the array coil was considerably improved in comparison with the body resonator examinations. The SNR and CNR increased approximately 100%. The handling of this coil was very quick and simple, similar to the procedure with other surface coils. The use of dedicated phased-array coils for peripheral MRA may be an important step toward the establishment of MR digital subtraction angiography (DSA) as a non-invasive alternative to intra-arterial DSA in the visualization of peripheral arteries. Its potential has to be evaluated in future studies.
Aged↗
Fluoroscopically triggered contrast-enhanced 3D MR DSA and 3D time-of-flight turbo MRA of the carotid arteries: first clinical experiences in correlation with ultrasound, x-ray angiography, and endarterectomy findings.
The aim of this article was to obtain initial experiences with fluoroscopically triggered contrast-enhanced (CE) 3D MR DSA with elliptical centric k-space order and 3D time-of-flight (TOF) turbo MRA of the carotid arteries. In this prospective study we examined 16 consecutive patients with suspicion of atherosclerotic disease involving the carotid arteries. Ultrasound was available in all, x-ray angiography in 12, surgical correlation in 9, and intraoperative x-ray angiography in 4 patients. All examinations were done on a 1.5 T unit applying: transverse plain 3D TOF turbo MRA and coronal CE MRA with fluoroscopic triggering. Combining head and neck array coils allowed the visualization of supraaortic arteries from the aortic arch to the circle of Willis. MRA results (maximum intensity projections) were compared with x-ray angiography, ultrasound, and inspection of endarterectomy specimens. Volume rendering was performed in selected cases additionally. Agreement between CE MRA, 3D TOF turbo MRA and x-ray angiography regarding stenoses of the internal and external carotid artery was very good. CE MRA was able to detect correctly intracranial stenoses, but delineation of the aortic arch and proximal common carotid arteries was sometimes reduced. Volume rendering was suited for visualization of MRA images providing a realistic three-dimensional impression. In conclusion, high-resolution fluoroscopically triggered CE MRA as non-invasive technique is another important step on the way to replace invasive x-ray angiography for the evaluation of atherosclerotic carotid artery disease. High resolution 3D TOF turbo MRA might be a helpful adjunct to increase the diagnostic reliability for the carotid bifurcation.
Aged↗
[A hybrid technique for the automatic floating table MRA of peripheral arteries using a dedicated phased-array coil combination].
PURPOSE: We introduce a hybrid technique which allows a high resolution MRA of the peripheral arteries with a dedicated phased-array coil using the floating table technique. MATERIALS AND METHODS: Five patients with peripheral arterial occlusive disease were examined within one week with i.a. DSA and MRA using the hybrid technique. MRA examinations were done on a 1.5 T system. At first, pelvic arteries were examined in a single step mode applying the CareBolus technique. Subsequently, thighs and lower legs were examined using the floating table mode. 125 vascular segments were evaluated. RESULTS: The hybrid technique proved to be robust and could be performed in each case. Mean examination time was about 30 min. For 117 vascular segments no difference was found between i.a. DSA and MRA. Three segments revealed a higher grade of stenosis in DSA than in MRA, five segments were graded higher in MRA than in DSA. Occlusions were visualized identically in both methods. Venous overlap had no relevant effects on image evaluation. CONCLUSIONS: This hybrid technique in combination with phased-array coils allows a high resolution MRA of the peripheral arteries with very good image quality. If future studies confirm reduced venous overlap, this method may be an alternative also for users of the floating table MRA with the body resonator.
Arterial Occlusive Diseases↗
Post occlusion visualization of peripheral arteries with "floating table" MR angiography.
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Angiography, Digital Subtraction↗
Contrast enhanced MRA of peripheral arteries with the automatic "floating table".
Magnetic resonance angiography (MRA) is increasingly used as a non-invasive alternative to digital subtraction angiography (DSA). Besides plain time-of-flight (TOF) and phase contrast (PC) MRA a new MRA technique using positive contrast agent has been introduced recently. A fast 3D gradient-echo sequence is applied to reach a significant reduction of measurement time for acquisition of the MRA within the first pass of the contrast agent, thereby avoiding venous overlap. A significant progress was yielded by MR systems allowing manual table movement for examination of the pelvis and the lower limbs in one examination with a single contrast agent bolus. However, in this case it is necessary to have a coworker in the examination room moving the table manually. In this paper we report a prototype system which allows automatic table movement ("floating table"). Using this novel system we examined a patient with an aneurysm of the abdominal aorta and peripheral arterial occlusive disease (PAOD). Diagnostic results of contrast enhanced MRA and DSA were equivalent. In summary, the automatic floating table system introduced in this paper allows comfortable non-invasive examination of pelvic and lower limb arteries. The value of this technique in comparison to DSA has to be determined in future studies.
Arterial Occlusive Diseases↗
Gd-BOPTA: "the MRA contrast agent of choice"?
Gd-BOPTA is a new positive MR contrast agent for intravenous application. In comparison to other gadolinium-chelates it has a nearly two-fold increased relaxivity due to weak protein binding with plasmatic macromolecules. In the papers published yet it has been evaluated to be useful for liver imaging. The purpose of this study was to evaluate, whether Gd-BOPTA is suited as an "magnetic resonance angiography (MRA) contrast agent". We examined four patients (aortic dissection, carotid artery stenosis, portal vein stenosis, exclusion of subclavian artery stenosis) with Gd-BOPTA with a dosage of 0.05 mmol/kg body weight. Furthermore, peripheral MRA of the pelvis and lower extremities was acquired in two healthy volunteers comparing 0.1 mmol Gd-DTPA/kg with 0.1 mmol Gd-BOPTA/kg. There was a delay of one week between the Gd-DTPA and the Gd-BOPTA examinations. In another volunteer Gd-BOPTA was reduced to 0.05 mmol/kg. The patient examinations revealed sufficient quality comparable with Gd-DTPA examinations despite of reduced dosage. In the volunteers Gd-BOPTA proved to be superior especially in the delineation of small pedal arteries which is important for surgical planning. These preliminary results demonstrate the potential of Gd-BOPTA to become a useful contrast agent for MRA. Its efficacy for this purpose has to be evaluated in future prospective studies.
Aortic Valve Stenosis↗