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Magnetic resonance imaging (MRI) with a continuously moving table (CMT) represents a novel method allowing for the seamless acquisition of an extended field-of-view in the z-direction. One option to realize CMT MRI from a technical point of view is based on very fast sequences like echo planar imaging (EPI). Consequently, table translation for signal sampling and image reconstruction can be neglected. The acquisition of different contrasts, however, necessitates table motion correction, either during acquisition or via post-processing. First clinical studies applying fast steady-state imaging already yielded promising results with respect to metastasis detection. Nevertheless, additional equipment has to be installed for table motion and position tracking. In contrast, the subsequently developed sliding multislice (SMS) technique can be implemented without any additional hardware. In clinical studies, the achievable image quality corresponds to stationary sequences. Additionally, the use of SMS for the detection of pulmonary and abdominal metastases appears to be comparable to computed tomography (CT). Due to the relatively short examination times, CMT MRI can be integrated into highly specialized stationary imaging protocols, thus increasing the possibility to combine local staging with thoracoabdominal metastasis screening within one examination. New contrasts like diffusion-weighted imaging (DWI) or Dixon techniques as well as improved workflow including breathing motion compensation and intuitive scout acquisition have already been proposed and will further expand the clinical applications of this technique., (© Georg Thieme Verlag KG Stuttgart · New York.)

Purpose: To investigate the feasibility of diffusion-weighted (DWI) echo-planar imaging (EPI) to depict the submandibular glands and to measure different functional conditions., Materials and Methods: Twenty-seven healthy volunteers were examined. Diffusion weighted sequence was performed prior to stimulation. Exactly 30 seconds after a commercially available lemon juice was given orally, the diffusion weighted sequence was repeated. All examinations were performed by using a 1.5-T superconducting system with a 30 mT/m maximum gradient capability and maximum slew rate of 125 mT/m/sec (Magnetom Symphony, Siemens, Erlangen, Germany). The lower part of the circularly polarized (CP) head coil and a standard two-element CP neck array coil were used. The flexibility of the neck array coil allowed positioning the N1 element (upper part of the coil) right next to the submandibular gland. The axial diffusion-weighted EPI (echo planar imaging) sequence was performed using a matrix of 119 x 128, a field of view of 250 x 250 mm (pixel size 2.1 x 1.95 mm), a section thickness of 5 mm with an interslice gap of 1 mm. The b factors used were 0 sec/mm(2), 500 sec/ mm(2) and 1000 sec/mm(2). Apparent diffusion coefficiant (ADC) maps were digitally transferred to MRIcro (Chris Rorden, Universitiy of Nottingham, Great Britain). After detecting the submandibular glands a region of interest (ROI) was placed manually exactly within the boarder of both submandibular glands, excluding the external carotid artery on ADC maps. These procedures were performed on all ADC slices the submandibular glands could be differentiated in before and after oral stimulation. For statistical comparison of results, a student's t-test was performed with an overall two-tailed significance level of p = 0.05., Results: The visualization of the submandibular glands using the diffusion-weighted EPI sequence was possible in all of the 27 volunteers. Prior to oral stimulation an ADC of 1.31 x 10(-3) mm(2)/sec (95 % CI, 1.39 x 10(-3) mm(2)/sec, 1.44 x 10(-3) mm(2)/sec) was calculated which increased to 1.41 x 10(-3) mm(2)/sec (95 % KI, 1.39 x 10(- 3) mm(2)/sec, 1.44 x 10(-3) mm(2)/sec) 30 seconds after stimulation. This increase proved to be significant (p < 0.001)., Conclusion: Diffusion-weighted echo-planar MR imaging allows non-invasive quantification of functional changes in the submandibular gland.

Purpose: An experimental study using porcine lung explants and a dedicated chest phantom to evaluate the signal intensity of artificial alveolar infiltrates with T 1 - and T 2 -weighted MRI sequences., Material and Methods: 10 porcine lung explants were intubated, transferred into the cavity of a MRI-compatible chest phantom and inflated by continuous evacuation of the artificial pleural space. All lungs were examined with MRI at 1.5 T before and after intra-tracheal instillation of either 100 or 200 ml gelatine-stabilised liquid to simulate alveolar infiltrates. MR-examination comprised gradient echo (2D- and 3D-GRE) and fast spin echo sequences (T 2 -TSE and T 2 -HASTE). The signal intensity of lung parenchyma was evaluated at representative cross sections using a standardised scheme. Control studies were acquired with helical CT., Results: The instilled liquid caused patchy confluent alveolar infiltrates resembling the findings in patients with pneumonia or ARDS. CT revealed typical ground-glass opacities. Before the application of the liquid, only T 2 -HASTE and T 2 -TSE displayed lung parenchyma signals with a signal/noise ratio of 3.62 and 1.39, respectively. After application of the liquid, both T 2 -weighted sequences showed clearly visible infiltrates with an increase in signal intensity of approx. 30 % at 100 ml (p < 0.01) and 60 % at 200 ml (p < 0.01). With 2D- and 3D-GRE the infiltrates were not visible, although the lung parenchyma signal increase was statistically significant. On 2D-GRE the increase in signal intensity reached 0.74 % (p = 0.32) after 100 ml and 5.6 % (p < 0.01) after 200 ml (for 3D-GRE: 2.2 % [p = 0.02] at 100 ml and 4.4 % at 200 ml [p < 0.01]). The CT controls revealed a significant increase of lung density of 17 H.E. at 100 ml (p = 0.02) and 75 H.E. at 200 ml (p < 0.01)., Conclusions: MRI with T 2 -weighted sequences detects artificial alveolar infiltrates with high signal intensity and may be a highly sensitive tool to detect pneumonia in patients.

Purpose: Different parameters for the evaluation of perfusion studies with dynamic MR measurements after the administration of paramagnetic contrast agent were compared., Method: An echo planar imaging (EPI) sequence was developed that allows dynamic multi-slice data acquisition. Evaluations of the measurements were performed by calculating parameter maps. Phenomenological quantities such as maximal signal reduction and time to peak as well as derived quantities such as approximations of the regional cerebral blood volume were used as parameters. Patients with a low grade astrocytoma, with an acute cerebral infarction and with stenoses of the carotid arteries were examined., Results: On comparison of the derived parameters with the phenomenological parameters no major differences were found in qualitative comparisons of the parameter maps. The comparison of relative parameter values in selected regions within the datasets of 20 patients show a high correspondence between phenomenological and derived parameter values., Conclusions: Using EPI measurement techniques with high temporal resolution, parameter maps of simple values like maximal signal reduction and time-to-peak are sufficient to visualize relative differences of perfusion within the selected slices. However, the calculation of relative rCBV and rCBF values might be helpful for the detailed characterization of signal courses in selected regions.

Purpose: Analysis of temporal changes of ADC values at different stages after stroke., Materials and Methods: The original images of all scans were evaluated and a region of interest analysis was performed on ADC (apparent diffusion coefficient) maps. 92 patients with symptoms of ischemic stroke were examined at 1.5 Tesla (ACS-NT, Philips Medical Systems). The study protocol included a navigated multishot SE-EPI DWI (b = 0, 189, 750 s/mm-2, TE = 120/140 ms, delta/delta = 49/60 ms), a GraSE (TR/TE = 3500/90 ms) and a FLAIR-TSE (TR/TE/TI = 6000/150/2000 ms) sequence. 8 patients had regular follow-ups. All patients had an additional CT scan., Results: In hyperacute stroke (< 6 h, n = 10) the relative ADC of the infarct core dropped to about 50% and reached a minimum in the acute state (6-48 h, n = 14) during the next few hours. In subacute stroke (< 3 weeks, n = 29) the ADC began to rise significantly (p = 0.001) back to normal values and reached (p < 10(-4)) values similar to cerebrospinal fluid in the chronic state (> 3 weeks, n = 20). The combined use of DWI and conventional MRI improved the diagnostic information in 16% of all MR examination beyond the hyperacute assessment., Conclusion: By means of the ADC-values the age of stroke can be determined. Infarcts at different stages can be readily diagnosed with the combined use of DWI, FLAIR-TSE and GraSE. Pitfalls of DWI and conventional imaging can be avoided.

A diffusion sensitive pulse sequence using a stimulated echo (STEAM) type excitation and echo-planar (EPI) readout was developed on a 1.5 T echo-planar MR imaging system. Using this sequence the authors measured the apparent diffusion coefficients (ADC) of water in normal human liver, spleen, muscle and kidney in 12 volunteers. ADCs measured in normal volunteers were: liver, 1.39 +/- 0.16 x 10(-3) mm2/s, spleen, 0.95 +/- 0.15 x 10(-3) mm2/s, muscle, 1.99 +/- 0.16 x 10(-3) mm2/s, kidney, 3.54 +/- 0.47 x 10(-3) mm2/s. A large scatter of the ADCs in the kidneys was found in the different degrees of hydration status among the volunteers and also due to inter-subject variability. With further clinical experience, in vivo diffusion measurements of the abdominal organs may prove helpful in the identification and classification of abdominal disease by MRI.

The purpose of the present study was to investigate the clinical application of echoplanar MR imaging compared to conventional MR imaging in the detection of focal liver lesions. A total of three conventional and 12 echoplanar pulse sequences were acquired in 35 patients with focal liver lesions. Motion artifacts were eliminated because of short acquisition times of 32 ms subsequently improving signal-to-noise. A single-shot spin-echo technique with a TE of 26 ms provided the highest liver signal-to-noise ratio (p < 0.05) of all sequences acquired. Contrast-to-noise ratios for a single-shot SE technique with echo times of 50-100 ms were as high as 10-40.