The purpose of this study was to demonstrate a new technical approach for a noninvasive dynamic study of gastric motor function with hydro-MRI. This robust method may have clinical application, e.g., in the diagnosis of gastroparesis, and may be extended to the rest of the gastrointestinal tract.

Seventy-four patients with one to eight proven intraaxial brain metastases received a total cumulative dose of 0.2 mmol/kg bodyweight gadobenate dimeglumine, administered as sequential injections of 0.05, 0.05 and 0.1 m mol/kg over a 20-min period. MR imaging was performed before the first administration (T2- and T1-weighted sequences) and after each injection of contrast agent (T1-weighted sequences only). Quantitative assessment of images revealed significant (P <0.01) dose-related increases in lesion-to-brain (L/B) ratio and percent enhancement of lesion signal intensity. Qualitative assessment by two independent, blinded assessors revealed additional lesions in 22%, 25% and 38% (assessor 1) and 29%, 32% and 34% (assessor 2) of patients after each cumulative dose when compared with combined T1- and T2-weighted pre-contrast images. Significantly more lesions (P < 0.01) were noted by both assessors after the first injection and by one assessor after each subsequent injection. For patients with just one lesion observed on unenhanced T1- and T2-weighted images, additional lesions were noted in 12%, 16% and 28% of patients by assessor 1 following each dose and in 24%, 27% and 30% of patients by assessor 2. Contemporaneously, diagnostic confidence was increased and lesion conspicuity improved over unenhanced MRI. For patients with one lesion observed after an initial dose of 0.05 mmol/kg, additional lesions were noted by assessors 1 and 2 in 9.1% and 11.8% of patients, respectively, after a cumulative dose of 0.1 mmol/kg and in a further 9.1% and 5.9% of patients, respectively, after a cumulative dose of 0.2 mmol/kg. No safety concerns were apparent.

In the evaluation of ischemic heart disease only MR imaging seems to have the potential to assess myocardial perfusion, function, and coronary morphology on a single instrument. The aim of this study was to assess the feasibility of a stress test with dipyridamole (0. 56 mg/kg) to analyze myocardial perfusion by Gd first-pass enhancement in ultrafast gradient-recalled-echo MRI (perf-MRI), and wall motion by cine gradient-recalled-echo MRI (Cine-MRI) in one imaging session. Twelve patients underwent complete rest and stress studies; satisfactory MR images were acquired in 10 patients. By 99 mTc-MIBI-SPECT sensitivities to detect ischemic segments were 66.7 % with Perf-MRI, 80.0 % with WM-MRI and 86.7 % for Perf-WM-MRI (Perf-MRI vs Perf-WM-MRI; p = 0.03). Scar was equally detected with a sensitivity of 91.6 % with either MRI technique. Thus, Perf-Cine-MRI provides complementary information for the management of ischemic heart disease and has a higher sensitivity than Perf-MRI alone.

The application of a contrast-enhanced, two-dimensional MR technique, which provides dynamic projection angiograms at a subsecond temporal frame rate for depiction of the cervical and intracranial arteries, was evaluated in three healthy volunteers and seven patients with various cervicocranial steno-occlusive diseases. Intra-arterial digital subtraction angiography (DSA) served as standard of reference for findings in the patients. Magnetic resonance projection angiography (MRPA) was performed on a standard 1.5-T clinical MR imaging system at intravenous injection of a single dose of contrast agent (0.1 mmol/kg GdDTPA-BMA). Sixty consecutive images of the cerebral circulation were acquired at a temporal frame rate of 900 ms per image in the coronal plane. The collateral flow and the perfusion of the compromised vessel territory were readily assessed by MPRA in patients with occlusion of the internal cerebral artery (ICA) or middle cerebral artery (MCA). The leptomeningeal collateralisation of these patients was displayed in a dynamic fashion. Furthermore, quantitative perfusion measurement provided a difference between both MCA territories in the time to peak (deltaDTTP) of the contrast bolus of 1.12 +/- 0.28 s in five patients with severe stenosis or occlusion of the ICA (healthy volunteers 0.19 +/- 0.05 s). However, important pathological findings, such as the evaluation of carotid artery stenoses and the intracranial collateral flow pattern in patients with severe carotid stenoses, were not sufficiently assessable as compared with DSA. We conclude that the possibility of obtaining simultaneously information about morphology and perfusion dynamics of the cervicocranial vessels is unique in MPRA as compared with other MR techniques. However, in the applied form, the technique is not a reliable tool for the complete evaluation of the cervicocranial vessels in patients with steno-occlusive disease.

MR angiography (MRA) is a technique under ongoing discussion. Its non-invasiveness and sensitivity to flow irregularities make it an investigational technique which is easy to apply but which does not always lead to comprehensive results. It requires special skill to perform and also experience for correct interpretation of the results. The lengthiness of the procedure combined with certain physical properties tends to limit its use to mostly neurovascular applications. With the introduction of ultrafast MRA in conjunction with peripheral bolus-injection of extracellular contrast media, a new approach to the imaging of such regions as the thoracic and abdominal vasculature not to mention other vascular territories has become possible. In this paper, considerations of bolus and measurement optimization and timing protocols for dedicated indications are presented together with an overview on the experience acquired to date for CE-MRA of the carotid artery, mediastinal and pulmonary vessels, abdominal vasculature, and peripheral vessels. The main advantage of ultrafast CE-MRA is that patients are subjected to much more tolerable breath-hold investigations with the result that physiological motion such as peristalsis or major pulsation is minimised.