Non-Contrast-Enhanced Carotid MRA: Clinical Evaluation of a Novel Ungated Radial Quiescent-Interval Slice-Selective MRA at 1.5T

BACKGROUND AND PURPOSE

Non-contrast-enhanced MRA techniques have experienced a renaissance due to the known correlation between the use of gadolinium-based contrast agents and the development of nephrogenic systemic fibrosis and the deposition of gadolinium in some brain regions. The purpose of this study was to assess the diagnostic performance of ungated non-contrast-enhanced radial quiescent-interval slice-selective MRA of the extracranial supra-aortic arteries in comparison with conventional contrast-enhanced MRA in patients with clinical suspicion of carotid stenosis.

MATERIALS AND METHODS

In this prospective study, both MRA pulse sequences were performed in 31 consecutive patients (median age, 68.8 years; 19 men). For the evaluation, the cervical arterial system was divided into 35 segments (right and left side). Three blinded reviewers separately evaluated these segments. An ordinal scoring system was used to assess the image quality of arterial segments and the stenosis grading of carotid arteries.

RESULTS

Overall venous contamination in quiescent-interval slice-selective MRA was rated as "none" by all readers in 84.9% of cases and in 8.1% of cases in contrast-enhanced MRA (P < .0001). The visualization quality of arterial segments was considered good to excellent in 40.2% for the quiescent-interval slice-selective MRA and in 52.2% for the contrast-enhanced MRA (P < .0001). The diagnostic accuracy of ungated quiescent-interval slice-selective MRA concerning the stenosis grading showed a total sensitivity and specificity of 85.7% and 90.0%, respectively.

CONCLUSIONS

Ungated quiescent-interval slice-selective MRA can be used clinically as an alternative to contrast-enhanced MRA without a significantly different image quality or diagnostic accuracy for the detection of carotid stenosis at 1.5T.

High-resolution in utero 3D MR imaging of inner ear microstructures in fetal sheep

BACKGROUND AND PURPOSE

Developmental inner ear abnormalities can occur due to embryopathies as well as in the context of syndromal diseases like the CHARGE association. In severe cases, an early and definite in utero diagnosis is important for decision-making; here, fetal MR imaging can be a helpful tool. We present results of performing high-resolution MR imaging of the inner ear structures of fetal sheep in vivo.

METHODS AND MATERIALS

Six ewes carrying singleton fetuses (mean gestational age, 120 days) were examined under general anesthesia at 1.5T. A 3D true FISP sequence with isotropic voxel size (0.7 mm) was applied; acquisition time was 2:35 minutes. For a standard of reference, 1 stillborn lamb of equivalent gestation age was examined. Image analysis was performed in consensus by 2 radiologists regarding the depiction of anatomic landmarks on a 5-point scale. Motion artifacts were quantified on a 3-point scale.

RESULTS

The turns and modiolus of the cochlea as well as the origins of all 3 semicircular canals of the vestibular system of both sides could be reliably identified in every animal. Motion artifacts due to maternal breathing excursions or movements of the fetus were minimal. In case of breech presentation, the ventilation of the ewe had to be paused during the image acquisition to achieve acceptable results.

CONCLUSIONS

High-resolution intrauterine MR imaging of the inner ear microstructures in an animal model is feasible. However, the acquisition time of the sequence applied is still too long to perform such measurement in a clinical setting.

Sjögren's syndrome of the parotid gland: value of diffusion-weighted echo-planar MRI for diagnosis at an early stage based on MR sialography grading in comparison with healthy volunteers

PURPOSE

To investigate the value of diffusion-weighted echo-planar imaging (DW-EPI) for quantifying functional changes of the parotid gland in Sjögren's disease and to evaluate whether ADC mapping allows for early diagnosis based on MR sialography grading.

MATERIALS AND METHODS

Using a DW-EPI sequence at 1.5 T (b-factors: 0, 500 and 1000 sec/mm (2)), the parotid glands of 52 healthy volunteers and 13 patients with histologically verified affection of Sjögren's disease were examined. All scans were performed prior to and following gustatory stimulation with 5 ml of lemon juice. ADC maps were evaluated by placing an inordinate region-of-interest (ROI) enclosing the entire parotid gland. Sjögren's disease was graded based on MR sialography findings using a 4-point grading-scale. Statistics included student t-test and kappa-analysis.

RESULTS

In healthy volunteers mean ADCs of 1.14 x 10 (-3 )mm (2) /sec before and 1.2 x 10 (-3) mm (2) /sec after stimulation were observed. Higher ADCs were determined for early-stage Sjögren's disease, averaging 1.22 x 10 (-3) mm (2) /sec before and 1.29 x 10 (-3) mm (2) /sec after stimulation. Advanced disease revealed significantly lower ADCs (0.97 x 10 (-3) mm (2) /sec (p = 0.002) before and 1.01 x 10 (-3) mm (2) /sec (p < 0.001) after stimulation).

CONCLUSION

DW-EPI seems to display functional changes of the parotid gland affected by Sjögren's disease. Combined with MR sialography, it might be a useful tool for discriminating healthy from affected glands and seems to allow differentiation between the early and advanced disease.

Diffusion-weighted echo-planar MR imaging of primary parotid gland tumors: is a prediction of different histologic subtypes possible?

BACKGROUND AND PURPOSE

Our aim was to determine the value of echo-planar diffusion-weighted MR imaging (epiDWI) in differentiating various types of primary parotid gland tumors.

MATERIALS AND METHODS

One hundred forty-nine consecutive patients with suspected tumors of the parotid gland were examined with an epiDWI sequence by using a 1.5T unit. Image analysis was performed by 2 radiologists independently, and the intraclass correlation coefficient was computed. Histologic diagnosis was obtained in every patient. For comparison of apparent diffusion coefficients (ADCs), a paired 2-tailed Student t test with a Bonferroni correction was used.

RESULTS

In 136 patients, a primary parotid gland tumor was confirmed by histology. Among the observers, a high correlation was calculated (0.98). ADC values of pleomorphic adenomas were significantly higher than those of all other entities, except for myoepithelial adenomas (P = .054). ADC values of Warthin tumors were different from those of myoepithelial adenomas, lipomas, and salivary duct carcinomas (P < .001, 0.013, and .037, respectively). Mucoepidermoid carcinomas, acinic cell carcinomas, and basal cell adenocarcinomas were not differentiable from Warthin tumors (P = .094, .396, and .604, respectively).

CONCLUSION

epiDWI has the potential to differentiate pleomorphic adenoma and myoepithelial adenomas from all other examined entities. Due to an overlap not only within the group of benign and malignant lesions but also between groups, diagnoses should not be addressed on the basis of ADC values solely. Therefore, further studies combining DWI, morphologic criteria, and probably other MR imaging techniques seem warranted.

Accuracy and precision in the detection of articular cartilage lesions using magnetic resonance imaging at 1.5 Tesla in an in vitro study with orthopedic and histopathologic correlation

BACKGROUND

Magnetic resonance (MR) sequences for cartilage visualization have been the target of numerous studies, and the optimal sequence for cartilage imaging remains a matter of debate in the literature.

PURPOSE

To compare MR findings with different MR sequences for the detection of cartilage lesions in fresh deep-frozen human cadaveric patellae in an in vitro setting.

MATERIAL AND METHODS

Ten cadaveric patellae were imaged on a 1.5T MR scanner with a 2x2 channel carotid sandwich coil and a conventional knee coil, and compared with orthopedic findings and gold-standard histopathology. MR sequences were: a) fat-saturated (FS) proton density-weighted (PDw) turbo spin-echo (TSE) sequence (TR/TE 4000/39 ms); b) T2-weighted (T2w) double-echo steady-state (DESS) 3D water-excitation (we) sequence (TR/TE 17/4.7 ms); c) 3D-PDw-SPACE (sampling perfection with application-optimized contrasts using different flip-angle evolutions)-we sequence (TR/TE 1800/19 ms). Accuracy, Kendall's tau-b correlation, and weighted kappa coefficients were calculated.

RESULTS

Accuracy for cartilage lesion detection with the FS PDw-TSE sequence and the carotid coil was 78.3%, and with the knee coil 73.9%. For the T2wDESS-3D-we sequence, the corresponding values were 69.5% and 65.2%, and for the 3D-PDw-SPACE-we sequence 65.2% and 60.8%, respectively. Kendall's tau-b correlation ranged between 0.508 for the 3D-PDw-SPACE-we sequence (knee coil) and 0.720 for the FS PDw-TSE sequence (carotid and knee coil). Weighted kappa coefficient was lowest for the 3D-PDw-SPACE-we sequence (knee coil) at 0.607, and highest for the carotid coil and FS PDw-TSE sequence at 0.779.

CONCLUSION

The evaluated FS PDw-TSE sequences are superior in comparison to the T2wDESS-3D-we and 3D-PDw-SPACE-we sequences in the in vitro setting for the detection of cartilage lesions, and are comparable to results reported in the literature.

Monitoring of gustatory stimulation of salivary glands by diffusion-weighted MR imaging: comparison of 1.5T and 3T

BACKGROUND AND PURPOSE

Our aim was to compare different field strengths monitoring physiologic changes due to oral stimulation of parotid glands by using diffusion-weighted (DW) echo-planar imaging (EPI).

MATERIALS AND METHODS

Twenty-seven healthy volunteers were examined with a DW-EPI sequence at 1.5T and 3T before and after oral stimulation with commercially available lemon juice. The b factors used were 0, 500, and 1000 s/mm(2). Apparent diffusion coefficient (ADC) maps were evaluated with a manually placed region of interest including the entire parotid gland. For comparison of results, a Student t test was used on the basis of the mean of the volunteer median values. To compare both field strengths, we calculated the Pearson correlation coefficient (r).

RESULTS

DW-EPI MR imaging visualized the parotid glands of all volunteers. With 1.5T, the mean ADC before stimulation was 1.12 x 10(-3) mm(2)/s +/- 0.08 x 10(-3) mm(2)/s. After stimulation with lemon juice, the ADC increased to 1.18 x 10(-3) mm(2)/s +/- 0.09 x 10(-3) mm(2)/s. For 3T, the ADC before stimulation was 1.14 x 10(-3) mm(2)/s +/- 0.04 x 10(-3) mm(2)/s, with an increase to 1.17 x 10(-3) mm(2)/s +/- 0.05 x 10(-3) mm(2)/s after stimulation. For both field strengths, the increase in ADC after stimulation was significant (P < .001). High correlations between both field strengths were found pre- and poststimulation (r = 0.955, and 0.936, respectively).

CONCLUSION

DW-EPI MR imaging allows monitoring of physiologic changes due to oral stimulation of parotid glands by using DW imaging with high correlation between 1.5T and 3T.

MR-Sialographie: Prospektive Evaluation ultraschneller Sequenzen mit paralleler Bildgebung und oraler Stimulation bei Patienten

PURPOSE

To evaluate an ultra-fast sequence for MR sialography requiring no post-processing and to compare the acquisition technique regarding the effect of oral stimulation with a parallel acquisition technique in patients with salivary gland diseases.

MATERIALS AND METHODS

128 patients with salivary gland disease were prospectively examined using a 1.5-T superconducting system with a 30 mT/m maximum gradient capability and a maximum slew rate of 125 mT/m/sec. A single-shot turbo-spin-echo sequence (ss-TSE) with an acquisition time of 2.8 sec was used in transverse and oblique sagittal orientation. All images were obtained with and without a parallel imaging technique. The evaluation of the ductal system of the parotid and submandibular gland was performed using a visual scale of 1-5 for each side. The images were assessed by two independent experienced radiologists. An ANOVA with post-hoc comparisons and an overall two tailed significance level of p = 0.05 was used for the statistical evaluation. An intraclass correlation was computed to evaluate interobserver variability and a correlation of > 0.8 was determined, thereby indicating a high correlation.

RESULTS

Depending on the diagnosed diseases and the absence of abruption of the ducts, all parts of excretory ducts were able to be visualized in all patients using the developed technique with an overall rating for all ducts of 2.70 (SD +/- 0.89). A high correlation was achieved between the two observers with an intraclass correlation of 0.73. Oral application of a sialogogum improved the visibility of excretory ducts significantly (p < 0.001). In contrast, the use of a parallel imaging technique led to a significant decrease in image quality (p = 0,011).

CONCLUSION

The applied ss-TSE for MR sialography allows fast and sufficient visualization of the excretory ducts of the main salivary glands in patients, and no elaborate post-processing is required. Use of an oral sialogogum is suggested to improve the results of MR sialography.

Diffusionsgewichtete MRT zur Funktionsdiagnostik der Glandula submandibularis

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.

Diffusion-weighted echo-planar MRI: a valuable tool for differentiating primary parotid gland tumors?

PURPOSE

To investigate the feasibility of using diffusion-weighted (DW) echo-planar imaging (EPI) for differentiating primary parotid gland tumors.

MATERIAL AND METHODS

Fifty consecutive patients with a suspected primary tumor of the parotid gland were examined with a DW EPI sequence (TR 1,500 msec, TE 77 msec, field of view 250 x 250 mm, pixel size 2.10 x 1.95 mm, section thickness 5 mm). The b factors used were 0, 500, and 1,000 sec/mm (2). Apparent diffusion coefficient (ADC) maps were digitally transferred to MRIcro (Chris Rorden, University of Nottingham, Great Britain) and evaluated with a manually placed irregular region of interest (ROI) containing the entire tumor. Additionally, the contralateral, non affected parotid gland was measured and a circular ROI containing 100 - 200 pixels was placed in the cerebrospinal fluid (CSF) next to the spinal cord in every patient. For comparison of the results, the two-tailed Student's t test was used, based on the median ADC values for each patient, and a p-value <.05 was determined to indicate statistical significance.

RESULTS

In 45 patients, a primary neoplasm of the parotid gland could be histologically verified. For the non-affected parotid glands of all 45 evaluated patients, the mean ADC value was 1.14 x 10 ( - 3) mm (2)/sec +/- 0.12 x 10 ( - 3) mm (2)/sec (mean +/- standard deviation). Seven different entities of parotid gland tumors were histologically discriminated. Pleomorphic adenomas (2.14 x 10 ( - 3) mm (2)/sec +/- 0.11 x 10 ( - 3) mm (2)/sec), Warthin tumors (0.85 x 10 ( - 3) mm (2)/sec +/- 0.1 x 10 ( - 3) mm (2)/sec), and mucoepidermoid carcinomas (1.04 x 10 ( - 3) mm (2)/sec +/- 0.3 x 10 ( - 3) mm (2)/sec) showed statistically significant different ADC values in comparison to all other evaluated tumors (p .001), and also among each other (p <.001). Additionally, ADC values presented by lipomas were statistically significant compared to all other entities (p <.001 to .015). Among all other [corrected] primary malignant parotid gland tumors, no statistically significant ADC values could be observed (p .18 to 1).

CONCLUSION

Diffusion-weighted echo-planar MRI seems to be a valuable tool for differentiating benign from malignant primary parotid gland tumors.

[MR-sialography: optimisation and evaluation of an ultra-fast sequence in parallel acquisition technique and different functional conditions of salivary glands]

PURPOSE

To optimise a fast sequence for MR-sialography and to compare a parallel and non-parallel acquisition technique. Additionally, the effect of oral stimulation regarding the image quality was evaluated.

MATERIAL AND METHODS

All examinations were performed by using a 1.5-T superconducting system. After developing a sufficient sequence for MR-sialography, a single-shot turbo-spin-echo sequence (ss-TSE) with an acquisition time of 2.8 sec was used in transverse and oblique sagittal orientation in 27 healthy volunteers. All images were performed with and without parallel imaging technique. The assessment of the ductal system of the submandibular and parotid gland was performed using a 1 to 5 visual scale for each side separately. Images were evaluated by four independent experienced radiologists. For statistical evaluation, an ANOVA with post-hoc comparisons was used with an overall two-tailed significance level of P =.05. For evaluation of interobserver variability, an intraclass correlation was computed and correlation >.08 was determined to indicate a high correlation.

RESULTS

All parts of salivary excretal ducts could be visualised in all volunteers, with an overall rating for all ducts of 2.26 (SD +/- 1.09). Between the four observers a high correlation could be obtained with an intraclass correlation of 0.9475. A significant influence regarding the slice angulations could not be obtained (p = 0.74). In all healthy volunteers the visibility of excretory ducts improved significantly after oral application of a Sialogogum (p < 0.001; eta (2) = 0.049). The use of a parallel imaging technique did not lead to an improvement of visualisation, showing a significant loss of image quality compared to an acquisition technique without parallel imaging (p < 0.001; eta (2) = 0.013).

CONCLUSION

The optimised ss-TSE MR-sialography seems to be a fast and sufficient technique for visualisation of excretory ducts of the main salivary glands, with no elaborate post-processing needed. To improve results of MR-sialography, it is reasonable to use an oral Sialogogum.

MRT der Pulmonalarterien bei Kindern nach arterieller Switch-Operation (ASO) bei Transposition der großen Gefäße (d-TGA)

PURPOSE

To determine the value of MRI in postoperative evaluation of patients with arterial-switch-operation (ASO) for d-TGA.

MATERIAL AND METHODS

14 consecutive patients with d-TGA and ASO were examined with MRI in addition to ultrasound because the acoustic window in echocardiography was insufficient. Nine patients had a pulmonary-artery-bifurcation anterior to the aortic root (group 1), and five (group 2) laterally (two of them left, three of them right). MRI was performed in six patients as contrast-enhanced MR-angiography, in 8 patients as native examination. Diameters of pulmonary arteries were measured in two perpendicular views at the origin and in two further locations each with a distance of one cm.

RESULTS

One patient showed a supravalvular pulmonary artery stenosis with subsequent pulmonary artery aneurysm, which had not been detected in echocardiography. This patient showed only indirect signs of pulmonary artery stenosis in echocardiography. Compared to group 1, pulmonary arteries in group 2 generally had greater diameters. Those pulmonary arteries in Group 2 which cross the mediastinum underneath the aortic arch had lower diameters compared to the pulmonary artery positioned on the other side. In group 1, the left-sided pulmonary artery had lower diameters than the right-sided pulmonary arteries. It seems remarkable that the narrowing of pulmonary arteries is associated with a flattening of the transversal vessel diameter.

CONCLUSION

Narrowing of pulmonary arteries after ASO is associated with oval vessel diameters. Therefore, multiplanar diagnostic methods are necessary. MRI meets this prerequisite and is therefore advantageous to echocardiography in follow-up examinations at patients with ASO for d-TGA. Special attention should be focused on the main pulmonary artery, on the left pulmonary artery in patients with preaortic pulmonary artery bifurcation as well as on the pulmonary artery which crosses the mediastinum in patients with laterally placed pulmonary artery bifurcation. Angiography should only be performed when intervention is planned.

Functional imaging of parotid glands: diffusion-weighted echo-planar MRI before and after stimulation

PURPOSE

To investigate the feasibility of diffusion-weighted (DW) echo-planar imaging (EPI) for measuring different functional conditions of the parotid gland and to compare different measurement approaches.

MATERIALS AND METHODS

Parotid glands of 27 healthy volunteers were examined with a DW EPI sequence (TR 1,500 msec, TE 77 msec, field-of-view 250 x 250 mm, pixel size 2.10 x 1.95 mm, section thickness 5 mm) before and after oral stimulation with commercially available lemon juice. The b factors used were 0, 500, and 1,000 sec/mm (2). Apparent diffusion coefficient (ADC) maps were digitally transferred to MRIcro (Chris Rorden, University of Nottingham, Great Britain) and evaluated with a manually placed circular region of interest (ROI) containing 100 - 200 pixel. Additional ROIs including the entire parotid gland were placed on either side. The results of both measurements were compared, using the Student's t test based on the median ADC values for each person. A two-tailed p-value of less than.05 was determined to indicate statistical significance. To compare both measurement approaches, the Pearson's correlation coefficient (r) was calculated.

RESULTS

Diffusion-weighted echo-planar MR imaging successfully visualized the parotid glands of all volunteers. In a first step, the median ADC value per person was computed. Using ROIs of 100 - 200 pixels, the mean was calculated to be 1.08 x 10 (- 3) mm (2)/sec +/- 0.12 x 10 (- 3) mm (2)/sec for both parotid glands prior to stimulation. After stimulation, the mean ADC was measured at 1.15 x 10 (- 3) mm (2)/sec +/- 0.11 x 10 (- 3) mm (2)/sec for both parotid glands. Evaluating the entire parotid gland, the ADC was 1.12 x 10 (- 3) mm (2)/sec +/- 0.08 x 10 (- 3) mm (2)/sec prior to stimulation, whereas the ADC increased to 1.18 x 10 (- 3) mm (2)/sec +/- 0.09 x 10 (- 3) mm (2)/sec after stimulation with lemon juice. For both types of measurements, the increase in ADC after stimulation proved to be significant (p < 0.001). High correlations between both measurement types were found (r >.83).

CONCLUSION

Diffusion-weighted echo-planar MR imaging allows non-invasive quantification of functional changes in the parotid glands.

Analysis of artefacts and detail resolution of lung MRI with breath-hold T1-weighted gradient-echo and T2-weighted fast spin-echo sequences with respiratory triggering

The aim of this study was to evaluate feasibility and limitations of two MR sequences for imaging of the lung using a semi-quantitative rating scale. Ten healthy volunteers were assessed with a breath-hold T1-weighted gradient-recalled-echo (TR/TE=129/2.2 ms, matrix 173 x 256) and a T2-weighted turbo spin-echo (TSE) sequence with respiratory triggering (TR/TE=3000-5000/120 ms, matrix 270 x 512) in axial 6-mm slices. The T1-weighted GRE protocol included a pre-saturation pulse over the mediastinal structures. Artefacts and resolution of vessel/airway structures in each lung segment were evaluated by two observers (10 volunteers, 180 segments). Cardiac and vessel pulsation artefacts predominated on T1-weighted GRE, respiration artefacts on T2-weighted TSE (lingula and middle lobe). Pre-saturation of the mediastinum reduced pulsation artefacts on T1-weighted GRE. T1-weighted GRE images were improved by bright flow signal of vessels, whereas image quality of T2-weighted TSE was reduced by black-blood effects in central parts of the lung. Delineation of lung periphery and the mediastinum was superior with T2-weighted TSE. Segmental/sub-segmental vessels (up to fourth/fifth order) and bronchi (up to third order) were identified. All 180 lung segments were imaged in diagnostic quality with at least one of the two sequences (T1-weighted GRE not diagnostic in 9 of 180, T2-weighted TSE in 4 of 180). Both sequences were found to be complementary: superior identification of gross lung anatomy with T1-weighted GRE and higher detail resolution in the periphery and the mediastinum with T2--weighted TSE.

Magnetic resonance imaging of the lung with a volumetric interpolated 3D-gradient echo sequence

OBJECTIVE

To evaluate the feasibility of a magnetic resonance imaging protocol for the lung using a volumetric interpolated 3D-gradient echo sequence (3D-GRE).

SUBJECTS AND METHODS

A T(1)-weighted 3D-GRE sequence was used for volumetric interpolated breath-hold examinations ("VIBE") of the lung in twelve healthy volunteers (TR/TE 4.5/1.9 ms, flip-angle 12 degrees, matrix 502 X 512 [interpolated]). Three coronal 80 mm slabs (16 aportitions, 2.5 mm slices) were added to 3D data sets for multi-planar reformations. No contrast material was applied. Artifacts and resolution o vessel and airway structures in each lung segment were evaluated by two observers (12 volunteers, 228 lung segments).

RESULTS

The protocol provided excellent images of vascular and tracheo-bronchial structures with very moderate pulsation artifacts. 224/228 lung segments were imaged with "good" (146/228) or "sufficient" quality (78/228). Segmental and sub-segmental vessels (5th order) were identified due to bright flow signal without administration of contrast material. Walls of segmental bronchi (3rd order) were delineated in all parts of the lung.

CONCLUSIONS

The high spatial resolution, the excellent visualization of lung anatomy, the low rate of artifacts without respiratory triggering and the short acquisition times are clear advantages of the 3D-GRE (VI-BE) sequence compared to existing 2D-GRE strategies for MRI of the lung.

Iliofemoral arterial occlusive disease: contrast-enhanced MR angiography for preinterventional evaluation and follow-up after stent placement

PURPOSE

To evaluate the efficacy of contrast material-enhanced magnetic resonance (MR) angiography for the diagnosis of peripheral arterial occlusion and follow-up after stent placement.

MATERIALS AND METHODS

Sixty-seven patients (21 women, 46 men; mean age, 64.6 years) were examined. Digital subtraction angiography and contrast-enhanced MR angiography were performed in 28 patients for preinterventional evaluation of iliofemoral arterial occlusion and in 39 patients for follow-up after stent placement in the iliac or femoral arteries, which had been performed several months before.

RESULTS

All 24 occlusions were correctly diagnosed with contrast-enhanced MR angiography. Of the 59 stenoses, 36 were greater than 50% and 23 were 50% or less. Sensitivity and specificity for the detection of stenoses greater than 50% were 100% and 83%, respectively. Patency of the different stents was determined correctly with contrast-enhanced MR angiography. Some stents caused signal intensity dropout, which made MR evaluation of stents difficult. Generally, these signal intensity artifacts were most severe in stainless steel stents and mild in some nitinol stents.

CONCLUSION

Contrast-enhanced MR angiography is comparable to digital subtraction angiography for the detection of stenosis greater than 50% and occlusion in the iliofemoral arteries. Stent patency can be determined, but contrast-enhanced MR angiography is not suitable for stent evaluation owing to signal intensity dropout; however, it provides information about the vascular anatomic areas proximal and distal to the stent.

Hepatic blood supply: comparison of optimized dual phase contrast-enhanced three-dimensional MR angiography and digital subtraction angiography

PURPOSE

To optimize and determine the value of dual-phase contrast material-enhanced three-dimensional (3D) magnetic resonance (MR) angiography for preoperative evaluation of the blood supply to the liver.

MATERIALS AND METHODS

Dual phase 3D MR angiography of the hepatic arteries and portal vein was performed in 140 patients. In 80 patients, the value of fat saturation, digital image subtraction, an anticholinergic agent, and a high-caloric meal were evaluated. In the next 60 patients, MR angiographic and digital subtraction angiographic (DSA) image quality and diagnostic value were compared.

RESULTS

Fat-saturated images were of significantly better quality (P < .01) than non-fat-saturated images. Digital image subtraction was useful in only 23 of 40 patients. The injection of an anticholinergic agent was superfluous, whereas administration of a high-caloric meal helped in demonstration of the superior mesenteric artery and portal vein. Classification on MR angiograms of the arterial blood supply was correct in 57 of 60 patients. All arterial and portal venous lesions were seen on MR angiograms, and MR angiograms had a significantly higher subjective image-quality ranking than did DSA images in the evaluation of the portal vein (P < .05).

CONCLUSION

Fat saturation and use of a high-caloric meal improve the results of MR angiography of hepatic vessels. MR angiography was comparable to DSA for evaluation of the arterial system and was superior for demonstration of the portal vein; therefore, MR angiography could replace intraarterial DSA.

Electrocardiograph-triggered two-dimensional time-of-flight versus optimized contrast-enhanced three-dimensional MR angiography of the peripheral arteries

We determined whether the accuracy of magnetic resonance angiography (MRA) in the peripheral run-off vessels can be improved by using contrast-enhanced (CE) three-dimensional (3D) technique in comparison to electrocardiograph (ECG)-triggered two-dimensional (2D) time-of-flight (TOF) technique. In a prospective study 20 patients with occlusions of the pelvic and/or femoral arteries underwent a CE 3D MRA (repetition time (TR): 5 ms, (TE) echo time: 2 ms, flip angle (FA): 30 degrees ) and an ECG-triggered 2D time-of-flight (TOF) technique (TR: 408 resp. 608 ms, TE: 7 ms, FA: 70 degrees) of the run-off vessels on a 1.5 T MR system. Each patient received a contrast material volume of 0.15 mmol/kg of body weight of gadolinium (Gd)/DTPA using an automatic injector. The tube system to the patient was flushed by 50 mL of a saline solution applied with the same injection rate as the contrast material administration. The start of the 3D MR sequence was tailored individually to the applied contrast material after determination of circulation times by a prior bolus. All patients underwent each conventional or digital arteriography for comparison, as well. The visualization of the run-off vessels was ranked on a scale of 0-3 (0 = poor, 1 = fair, 2 = good, 3 = excellent) by three blinded reviewers. They also graded the vascular segments as either occluded or significantly altered (>50% reduction in diameter) or free of significant stenosis. CE 3D MRA was significantly faster in imaging the run-off vessels in comparison to the ECG-triggered 2D TOF technique. All 160 vascular segments were visualized with the 3D method, whereas only 142/160 segments were seen with 2D technique. The resulting image quality ranking of all vascular segments was significantly higher (p < 0.05) using CE 3D MRA (2.8) than with the 2D TOF technique (2.4). The detection of the stenoses was possible with both techniques. The grading of seven of seven stenoses was correct with 3D method and in five of seven cases with the 2D TOF technique. All vessel occlusions were detected by using both techniques. Small collaterals were visualized in more detail with the CE 3D MR angiography. These data demonstrate an improvement in image quality and accuracy of MRA of the peripheral arteries using a CE 3D technique in comparison to an ECG-triggered 2D TOF sequence.

[Ultra-rapid T2-weighted MR imaging during suspended respiration for the examination of focal lesions of the liver: a comparison of TSE, HASTE and HASTE-STIR sequences using a CP body array coil]

PURPOSE

A comparison of ultra rapid T2-weighted HASTE and HASTE-STIR sequences during suspended respiration for the detection of focal lesions of the liver.

MATERIAL AND METHODS

Twenty-one patients (59 +/- 12 years) with a total of 33 focal lesions (7 < or = 1 cm, 19 < or = 3 cm; 17 cystic liquid and 16 solid lesions) were examined with a 1.5 T MR apparatus. Sequences: T2 weighted HASTE (TEeff = 64 ms, 90 ms), HASTE-STIR (TEeff = 64 ms, 81 ms) TSE (TE = 132 ms) and T1-weighted FLASH 2D.

RESULTS

The T2-weighted TSE and both HASTE sequences showed all the lesions. Two out of the 33 lesions were not demonstrated by the other sequences. Best image quality without movement artefacts and the best resolution of the lesions in the T2-weighted sequences, with the most favourable contrast/noise ratio (36.6 +/- 33.1) and signal/noise ratio (20.8 +/- 10.5) resulted from the HASTE 90, followed by the HASTE 64 sequence (27.5 +/- 24.2; 24.6 +/- 9.1). Both these techniques were superior to the TSE sequence (23.9 +/- 29.4; 13.9 +/- 7.4), which resulted in movement artifacts. With the HASTE-STIR sequences it was possible to show 31 and 32 of the 33 lesions respectively, with very good resolution but poor signal/noise ratio.

CONCLUSION

HASTE sequences have the potential of improving the diagnosis of focal liver lesions.

[MR angiography of the carotid arteries using 3D TOF technique with sagittal double-volume acquisition using a new head-neck coil]

PURPOSE

The aim of the study was to assess the value of MR angiography (MRA) in sagittal technique compared to DSA in the evaluation of carotid artery stenosis.

METHODS

80 carotid arteries in 40 symptomatic patients were prospectively studied with DSA and MRA. MRA was carried out by means of 3 D time-of-flight technique with a FISP sequence (TE6 ms/TR80 ms, flip angle 25 degrees, FOV 240 x 210 mm, matrix 157 x 256 mm, in-plane resolution 1.34 x 0.94 mm, partition thickness 1.32 mm, slab thickness 45 mm, acquisition time 7 min) using a new head-neck coll. Data acquisition was performed in sagittal orientation with the "double-slab" technique. Imaging quality of the extracranial carotid arteries and correctness of quantification of stenosis was performed.

RESULTS

Imaging quality was good at the origin of the carotid arteries in 65%, at the bifurcation region in 98% and near the skull base in 81%. The agreement of DSA and MRA was 96% of the normal arteries (24/25), 90% of the severe stenoses (28/31) and 100% of the occluded arteries (9/9).

CONCLUSION

MRA in sagittal "double-slab" technique is a noninvasive technique allowing to detect normal arteries and candidates for surgery with a high degree of certainty.