Fast spin-echo MR in the detection of vertebral metastases: comparison of three sequences

PURPOSE

To examine the relative capabilities for the detection of vertebral metastases of three available fast spin-echo sequences: T1-weighted fast spin-echo, short tau inversion recovery (STIR) fast spin-echo, and T2-weighted fast spin-echo sequences with chemical shift selective saturation pulse fat suppression.

METHODS

Fourteen patients were evaluated prospectively over a 2-month period with T1-weighted fast spin-echo (four echo train, four acquisitions, 1 min 59 sec-2 min 37 sec). STIR fast spin-echo (16 echo train, four acquisitions, 2 min 30 sec-3 min 19 sec), and T2-weighted fast spin-echo (16 echo train, 4 acquisitions, 2 min 27 sec-3 min 16 sec). For all three pulse sequences, measurements were obtained of the signal intensities of normal marrow, abnormal marrow, fat, and noise posterior to the spine. Contrast-to-noise ratios were calculated for metastases in each case. Lesions were evaluated by three observers and rated for size, location, and conspicuity.

RESULTS

Signal intensities of fat, normal marrow, and noise were highest for T1-weighted fast spin-echo sequences. STIR fast spin-echo and fat-suppressed T2-weighted fast spin-echo had approximately similar fat-suppression capabilities. Though contrast-to-noise ratios were highest overall for STIR fast spin-echo, the finding was not statistically significant and lesion conspicuity was deemed better with fat-suppressed T2-weighted fast spin-echo and T1-weighted fast spin-echo images. Discrete lesions were well identified on all three pulse sequences.

CONCLUSION

Fast spin-echo sequences appear promising for the detection of vertebral metastases. Further work should be directed toward comparison with conventional spin-echo to determine whether fast spin-echo may replace conventional spin-echo sequences for evaluation of vertebral metastases.

Imaging of neurologic complications associated with pregnancy

The occurrence of a neurologic event during pregnancy or the puerperium may have devastating consequences for mother and child. It is imperative that the radiologist be familiar with the entities likely to be encountered in pregnancy so that these patients can be examined rapidly and efficiently. The importance of early and accurate diagnostic imaging is underscored by the fact that most patients are otherwise young and healthy, and prompt institution of appropriate therapy can result in complete recovery. In this report, we illustrate some of the more common neurologic complications that occur during pregnancy and the immediate postpartum period.

Primary brain tumors in adults

Adult primary brain tumors comprise a diverse group of neoplasms that vary in their behavior depending on such factors as cell of origin, site of occurrence, morphology, and pattern of spread. Although the incidence of primary brain tumors is increasing in frequency, the prognosis of patients with these neoplasms has improved considerably due to recent advances in microsurgery, radiation treatment, and chemotherapy. Central to the efficacy of these techniques, however, is the ability of the radiologist to diagnose and interpret the growth pattern of these tumors. This article describes various types of primary intracranial neoplasms found in the adult, with emphasis on imaging characteristics and their importance in neuro-oncologic evaluation and management.

Hypertensive encephalopathy: findings on CT, MR imaging, and SPECT imaging in 14 cases

Hypertensive encephalopathy is a syndrome consisting of headache, seizures, visual changes, and other neurologic disturbances in patients with elevated systemic blood pressure. The purpose of this study was to analyze the imaging findings in 14 patients with hypertensive encephalopathy. CT (n = 13), MR (n = 12), and single-photon emission computed tomography (n = 2) examinations performed in these patients before and after resolution of symptoms were reviewed. Eight had the preeclampsia-eclampsia syndrome, and six had hypertensive encephalopathy due to other causes. CT and MR findings in all patients having these examinations were indicative of edema in the cortex and subcortical white matter in the occipital lobes. Two of the 14 patients also had similar findings in the cerebellum and frontal lobes. Single-photon emission computed tomography showed increased vascular perfusion adjacent to areas that appeared abnormal on CT and MR. The findings on the imaging studies resolved on follow-up examinations performed after the hypertension was corrected. Our results suggest that the radiologic findings associated with hypertensive encephalopathy may be useful in establishing the diagnosis in the appropriate clinical setting.

Rapid MR imaging of the pediatric brain using the fast spin-echo technique

PURPOSE

To evaluate diagnostic reliability and to establish optimal scanning techniques of a recently developed Fast Spin-echo MR pulse sequence that allows rapid proton density-weighted and T2-weighted imaging.

METHODS

We compared lesion conspicuity and signal intensity measurements on Fast Spin-echo and conventional spin-echo sequences in 81 patients ranging from 1 week to 25 years in age on a 1.5-T MR unit. A total of 28 Fast Spin-echo dual-echo images (14 slice locations) were obtained in 2:08 minutes with a 256 x 128 matrix or in 3:12 minutes with a 256 x 192 matrix at a TR of 2000 msec and two excitations.

RESULTS

Lesion conspicuity and characterization on Fast Spin-echo images compared favorably with conventional spin-echo images in our series when pseudo-TEs of 15 and 90 msec were employed for proton density-weighted and T2-weighted images, respectively. Fast Spin-echo images yielded diagnostic information in four nonsedated patients whose conventional spin-echo images were either degraded by motion or unobtainable. Fat signal remained bright on T2-weighted Fast Spin-echo images. Magnetic-susceptibility effects were slightly reduced with Fast Spin-echo but did not pose any diagnostic problem in our series.

CONCLUSION

Diagnostically reliable rapid dual-echo brain images can be obtained with Fast Spin-echo sequences.

Brain hemorrhage: evaluation with fast spin-echo and conventional dual spin-echo images

Signal intensity of blood products on proton-density- and T2-weighted images obtained with spin-echo (SE) and fast SE (FSE) sequences was evaluated in 15 patients with central nervous system hemorrhage to determine the extent of differences between the two techniques when signal loss from magnetic susceptibility effects in hemorrhagic lesions is considered. Within operator-defined regions of interest, signal intensity of hemorrhage, iron-containing nuclei, white matter, scalp fat, and noise was measured along the phase-encoding direction. Hemosiderin, deoxyhemoglobin, and iron-containing nuclei had slightly higher signal intensity on FSE images than on SE images, but the differences were not statistically significant. Signal intensity of methemoglobin was similar with both sequences, whereas that of scalp fat was higher on FSE images. Signal intensity measurements for most tissues studied were comparable, but the signal-to-noise ratios with FSE imaging were less than those with SE imaging. Although paramagnetic blood products may show slightly higher signal intensity with FSE imaging, contrast with the two sequences was comparable and lesion conspicuity was nearly identical.

Impending rupture of nonaneurysmal bacterial aortitis: CT diagnosis

The CT appearance of mycotic abdominal aortic aneurysms leading to eventual rupture has been well described. On the other hand, ruptured nonaneurysmal bacterial aortitis has not been demonstrated in the CT literature. We present two cases with subsequent rupture documented on CT. The characteristic findings of periaortic density and adjacent gas collection should suggest the diagnosis of acute aortic infection. This may herald impending rupture, even in the absence of aneurysmal dilatation, and should direct therapy accordingly.