Low-dose intra-arterial contrast-enhanced MR aortography in patients based on a theoretically derived injection protocol

Abstract

Multiple intra-arterial contrast agent injections are necessary during MR-guided endovascular interventions. In respect to the approved limits of maximum daily gadolinium dose, a low-dose injection protocol is mandatory. The objective of this study was to derive and apply a low-dose injection protocol for intra-arterial 3D contrast-enhanced MR aortography in patients. Injection rate (Q inj ), concentration of injected gadolinium [Gd] inj and aortal blood flow rate (Q blood ) were included for the theoretical evaluation of signal intensity (SI) of the arterial lumen. SI simulations were carried out at Q inj =2 versus 4 ml/s in the [Gd] inj range between 0-500 mM. Q inj and [Gd] inj with SI above the 75% threshold of the maximal SI were regarded as optimal injection parameters.[Gd] inj =50 mM and Q inj =4 ml/s were considered as optimal and were administered in five patients for 3D MR aortography. All images revealed clear delineation of the abdominal aorta and its major branches. Mean± SD of contrast-to-noise ratios of the abdominal aorta, common iliac and renal artery were 70.2±15.2, 58.6± 12.3 and 67.4±12.3. Approximately seven intra-aortal injections would be permissible in patients during MRguided interventions without exceeding the maximal dose of gadolinium.

Magnetic Resonance–Guided Passive Catheter Tracking for Endovascular Therapy

“…MR angiograms with intraarterial gadolinium contrast may also be used for MR guidance of endovascular procedures 18 (Figure 3). Similar to DSA, contrast-enhanced MRAs can be overlaid onto subsequent image acquisitions for vascular road-map guidance 19-21 .…”

“…The U.S. Food and Drug Administration (FDA) total dose limit for gadolinium chelate is 0.3 mmol/l/kg body weight. A low-dose gadolinium injection protocol requires 18, 22 taking into account the blood flow rate in the artery of interest and avoids excess concentrations of gadolinium (resulting in T2/T2* spin-dephasing effects) or inadequate gadolinium concentrations (resulting in lack of T1 shortening) 20, 24 . Since contrast delivery is local rather than systemic, much lower doses are needed, and thus, repeat intra-arterial contrast administration is practical.…”

MR-guided endovascular interventions: a comprehensive review on techniques and applications

“…Herein, multiple applications of gadolinium chelates during interventions should not exceed the daily dose limit (0.3 mmol/l/kg body weight) for gadolinium, as given by the U.S. Food and Drug Administration (FDA). The previously suggested injection protocol, depending on factors like injection rate, blood flow rate of the target vessel and gadolinium concentration, furthermore keeps the gadolinium blood concentration in a target range during MR data acquisition [23]. This is important because the paramagnetic effects of gadolinium would otherwise lead to fast spin-dephasing with T2/T2* signal reduction (gadolinium concentration above target range) or signal loss due to insufficient T1-shortening (gadolinium concentration below target range) [24].…”

“…Presently the intra-arterial application of gadolinium is an off-label use, which may be applied as there are no serious side effects documented so far. Due to the short half-life of gadolinium chelates and the consecutive need for repetitive applications, a low-dose gadolinium injection protocol is required [18,23]. Herein, multiple applications of gadolinium chelates during interventions should not exceed the daily dose limit (0.3 mmol/l/kg body weight) for gadolinium, as given by the U.S. Food and Drug Administration (FDA).…”

Renal Contrast-enhanced MR Angiography: Timing Errors and Accurate Depiction of Renal Artery Origins

“…A study in which researchers compared contrast agent doses that ranged from 0.1 to 0.3 mmol per kilogram of body weight showed that higher contrast agent doses increase contrast and improve depiction of smaller vessels (14); however, single-dose examinations have yielded sensitivity of at least 96% in the detection of renal artery stenosis (1,2) and have produced diagnostic images (15)(16)(17). Doses as low as 3.0 mmol enabled clear delineation of the abdominal aorta and its main branches (18), thus making renal contrast-enhanced MR angiography a good screening tool with which to rule out renal stenosis. In many protocols, a single fixed contrast agent volume was used (6,10,(15)(16)(17)19), and injection rates ranging from 0.5 mL/sec (19) to 3.5 mL/sec (3,8) have been used in high-spatial-resolution renal studies.…”