Breath-hold contrast-enhanced three-dimensional MR angiography of the abdomen: time-resolved imaging versus single-phase imaging

PURPOSE

To evaluate a technique for time-resolved breath-hold contrast material-enhanced three-dimensional magnetic resonance (MR) angiography of the abdomen.

MATERIALS AND METHODS

In a prospective study, 43 patients underwent time-resolved MR angiography (acquisition time per data set, 7 seconds). The patients also underwent single-phase high-spatial-resolution MR angiography (acquisition time, 27 seconds) (n = 6), conventional angiography (n = 7), or both (n = 30). No bolus timing study was performed for time-resolved MR angiography. Image quality (presence of artifacts, ability to prevent venous overlap on arterial phase images, contrast enhancement) and demonstration of anatomic variants (renal arterial and venous variants, vena caval anomaly, visceral arterial variants) and vascular diseases were assessed.

RESULTS

Time-resolved MR angiographic images were characterized by fewer and less severe artifacts, less overlap of enhancing veins, and better contrast enhancement than were single-phase MR angiographic images (P < .05). The mean sensitivity and specificity were 90% (nine of 10) and 100% (1 73 of 1 73), respectively, for detection of arterial anatomic variants and 93% (28 of 30) and 100% (324 of 325), respectively, for detection of disease. The technique also proved to be reliable for demonstration of venous disease.

CONCLUSION

In comparison with current non-time-resolved MR angiographic techniques, time-resolved MR angiography is more robust and easier to perform and allows simultaneous evaluation of arterial and venous disease.

Three-dimensional phase contrast MR cerebral venography with zero filling interpolation in the slice encoding direction

The purpose of this study was to evaluate the magnetic resonance (MR) cerebral venography findings of a three-dimensional phase contrast MR sequence with zero filling interpolation of the data in the slice encoding direction. Fifty volunteers were enrolled in the study. Images were obtained on a 1.5 MR imaging system with acquisition time of 12 min. MIP images were reconstructed throughout the entire imaging volume. A grading scale system was used to assess dural venous sinuses, major deep veins, cortical, and cortical eponymic veins. Inferior group of dural venous sinuses, inferior sagittal sinus, and cortical eponymic veins were poorly demonstrated. Score of the superior sagittal sinus, the straight sinus, the confluence of the superior sinus group, the right transverse and sigmoid sinuses, the internal veins, and the vein of Galen was excellent. The score of the left transverse and sigmoid sinuses was good. In conclusion, when using zero filling interpolation of the data in a three-dimensional phase contrast MR cerebral venography sequence, the superior group of dural venous sinuses and main major deep veins are demonstrated with good conspicuity.

Screening applications for MRI in the detection of upper abdominal disease: comparative study of non-contrast-enhanced single-shot MRI and contrast-enhanced helical CT

PURPOSE

To compare the value of 'push-button' single-shot non-contrast-enhanced MRI and contrast-enhanced helical CT for detection of upper abdominal disease.

METHODS

In 120 patients, images obtained with non contrast-enhanced single-shot MRI (T2: double echo HASTE, and T1: turbo FLASH) and contrast-enhanced helical CT were compared. Lesions or abnormalities were divided in 8 anatomical categories (1: liver; 2: pancreatobiliary; 3: kidney/adrenal gland; 4: retroperitoneum; 5: vascular; 6: spleen; 7: gastrointestinal tract and peritoneum; 8: base of thorax) and classified as follows: 2: seen at MRI only; 1: better seen at MRI; 0: no difference; -1: better seen at CT; -2: seen at CT only. Also recorded were the 'door-to-door' examination times.

RESULTS

Of a total of 629 abnormalities, 594 were detected at MRI (94 %) and 536 at CT (85 %). CT offered better results in two categories only: retroperitoneum (mean score: -0.68) and vascular (mean score -0.87). Mean examination times were 19 min for CT and 14.8 min for MRI.

CONCLUSION

Unenhanced single-shot MRI is a valuable first step of a comprehensive upper abdominal MR exam and may even be the final step in many patients.

Assessment of iron oxide particles (AMI 227) and a gadolinium complex (Gd-DOTA) in dynamic susceptibility contrast MR imagings (FLASH and EPI) in a tumor model implanted in rats

The objective of our study was to assess the feasibility of dynamic susceptibility contrast MR technique after bolus injection of SPIO and Gd-DOTA in a tumor model implanted in rats. Tumors were subcutaneously implanted in 24 rats. A FLASH sequence and EPI were evaluated. Different doses of AMI 227 and Gd-DOTA were assessed. Mean signal intensity vs. time curves were plotted. Well-shaped curves of the first pass of the contrast agent were only obtained with Gd-DOTA. According to these results it appears difficult to assess tumor blood volume with USPIO dynamic susceptibility contrast imaging.

Time-resolved MR angiography of the upper abdomen: initial clinical experience

In this study, thirty-eight patients with a variety of upper abdominal diseases were examined with three-dimensional time-resolved MR angiography (7 sec/data set). Visualisation of arterial and venous anatomy was excellent in the majority of patients. Moreover, subtraction images could be calculated and organ perfusion could be assessed. It is concluded that this technique opens new perspectives for a comprehensive evaluation of vascular and parenchymal disease.

Comparison of iron oxide particles (AMI 227) with a gadolinium complex (Gd-DOTA) in dynamic susceptibility contrast MR imagings (FLASH and EPI) for both phantom and rat brain at 1.5 Tesla

The goal of the study was to compare, in phantom and normally perfused rat brain tissue, a superparamagnetic iron oxide particle-based contrast agent (AMI 227) with a low-molecular-weight gadolinium chelate, gadolinium tetraazacyclododecanetetraacetic acid (Gd-DOTA), in two susceptibility contrast magnetic resonance imaging (MRI) modes [fast low-angle shot sequence (FLASH) and echoplanar imaging (EPI)]. A phantom consisting of dilution series of both contrast agents was manufactured. Dilutions were obtained with isotonic serum from the available agent solutions (0.5 mmol Gd/mL Gd-DOTA; 350 mumol Fe/mL AMI 227). Eighteen rats were studied. Contrast agent (0.1 mL) was bolus injected in each rat, and dynamic MRI was performed (first pass of the contrast agent) in rat brain. The doses of AMI 227 injected were extrapolated from the phantom experiment: 0.2 mmol/kg body weight of Gd-DOTA and 7, 14, and 28 mumol Fe/kg body weight of AMI 227 were injected. For both sequences, signal-to-noise ratios (S/N) were measured on each tube of the phantom and on rat brain from each image of the dynamic imaging. S/N was plotted versus contrast dilution (phantom) and versus time (rats). In the FLASH sequence, a well-shaped curve (S/N decrease, S/N peak decrease, S/N increase) of the first pass of the contrast agent was demonstrated for Gd-DOTA and for AMI 227 (7 mumol Fe/kg body weight). In the EPI sequence, a well-shaped curve was demonstrated for Gd-DOTA, and a plateau effect was noted for both concentrations of AMI 227. With the FLASH technique, dynamic susceptibility contrast imaging of rat brain can be performed with very low concentrations of AMI 227 compared with the Gd-DOTA concentration (0.2 mmol Gd/kg body weight) used in clinical practice. This could be of interest in perfusion imaging, because it may allow for first-pass susceptibility imaging after administration of a small volume in a narrow bolus.

Normal Vaterian sphincter complex: evaluation of morphology and contractility with dynamic single-shot MR cholangiopancreatography

OBJECTIVE

The objective of this study was to assess the usefulness of dynamic single-shot MR cholangiopancreatography in the evaluation of the morphology and contractility of the normal Vaterian sphincter complex and to assess whether i.v. injection of glucagon can improve visualization.

SUBJECTS AND METHODS

Sixty patients without signs of Vaterian sphincter complex dysfunction were studied. A fast single-shot MR imaging sequence was used to obtain 20 consecutive images of the Vaterian sphincter complex during successive episodes of breathholding. In patients of group A (n = 30), 10 images were obtained before and 10 after i.v. administration of a sphincter-relaxing agent (glucagon). In the patients of group B (n = 30), no glucagon was administered. The degree of visualization of the Vaterian sphincter complex was assessed.

RESULTS

Overall, the morphology and contractility of the Vaterian sphincter complex was adequately assessed in 57 patients (95%). However, the number of repetitions required to obtain this result varied greatly (mean, seven; range, two to 18). Glucagon had no apparent effect on the visibility of the most distal portion of the common bile duct.

CONCLUSION

Nonvisualization of the most distal portion of the common bile duct on MR cholangiopancreatography studies is a normal variant that can simulate disease. Obtaining serial breath-hold images using a single-shot technique is helpful to avoid diagnostic errors.

Preliminary experience with a new double-echo half-Fourier single-shot turbo spin echo acquisition in the characterization of liver lesions

A new double-echo half-Fourier single-shot turbo spin echo technique has been implemented in which two images are obtained per excitation pulse, one with an echo time (TE) of 60 ms and another with a TE of 438 ms. The acquisition window per image is 380 ms and is determined by the echo spacing of 4.3 ms and the echo train length of 88 for images with resolution of 160 x 256. No breath holding was performed. The aim of the study was to test whether the additional information of the late TE image improves the characterization of liver lesions. Twenty-eight patients with 39 focal liver lesions (9 cysts, 11 hemangiomas, and 19 solid lesions) were imaged with the new technique, and signal intensity (SI) ratios of lesion and liver were obtained. A t-test analysis showed that in the TE 60 ms image, SI ratios of cysts and hemangiomas were not significantly different, whereas in the TE 438 ms images the two types of lesions can be classified. Signal intensity ratios of solid lesions were in both images clearly lower than those of cysts and hemangiomas. The technique, therefore, seems a promising and straightforward new tool for the characterization of liver lesions.

Chordoma of the lower cervical spine

Vertebral chordomas are rather rare tumours, especially in the lower cervical region. We present a patient with a C7 vertebral body chordoma and a discussion of pertinent literature is given. Only three C7 chordomas have been reported previously. Diagnosis is sometimes difficult to establish and is based on radiological examinations. Once the histological diagnosis is available, one should aim at a total resection. If this is not possible, adjuvant radiotherapy should be given. For limited cervical lesions, we advise a corporectomy with fusion by an iliac crest graft and osteosynthetic plate stabilisation.