Fast imaging

Assessment for Carotid Atherosclerotic Plaque Using Vessel Wall Magnetic Resonance Imaging: A Multireader ROC Study to Determine Optimal Sequence for Detecting Vessel Wall Calcification

INTRODUCTION

We aimed to compare conventional vessel wall MR imaging techniques and quantitative susceptibility mapping (QSM) to determine the optimal sequence for detecting carotid artery calcification.

METHODS

Twenty-two patients who underwent carotid vessel wall MR imaging and neck CT were enrolled. Four slices of 6-mm sections from the bilateral internal carotid bifurcation were subdivided into 4 segments according to clock position (0-3, 3-6, 6-9, and 9-12) and assessed for calcification. Two blinded radiologists independently reviewed a total of 704 segments and scored the likelihood of calcification using a 5-point scale on spin-echo imaging, FLASH, and QSM. The observer performance for detecting calcification was evaluated by a multireader, multiple-case receiver operating characteristic study. Weighted κ statistics were calculated to assess interobserver agreement.

RESULTS

QSM had a mean area under the receiver operating characteristic curve of 0.85, which was significantly higher than that of any other sequence (p < 0.01) and showed substantial interreader agreement (κ = 0.68). A segment with a score of 3-5 was defined as positive, and a segment with a score of 1-2 was defined as negative; the sensitivity and specificity of QSM were 0.75 and 0.87, respectively.

CONCLUSION

QSM was the most reliable MR sequence for the detection of plaque calcification.

Hyperparathyroidism — Comparison of Flash Imaging with Spin ECHO MR Imaging

MR images of the neck were prospectively studied in 19 patients with hyperparathyroidism. Fast low angle shot (FLASH) sequence was performed in addition to T1- and T2-weighted spin echo (SE) sequences. FLASH images were obtained with 320/12/20° (TR/TE/flip angle) using presaturation technique. TE of 12 ms was chosen to eliminate high signal of fat tissue. In the evaluation of detectability, a combination of T1-weighted SE and FLASH images (T1WI + FLASH) was compared with a combination of T1- and T2-weighted SE images (T1WI + T2WI). MR imaging correctly depicted 20 of 30 abnormal glands on both T1WI + FLASH and T1WI + T2WI. FLASH imaging effectively eliminated high signal of fat tissue. Nineteen abnormal glands demonstrated higher signal than surrounding tissues on FLASH images, whereas 12 glands were high-intense on T2-weighted SE images. We conclude that FLASH imaging provides improved tissue contrast and anatomic delineation and, thus, may replace T2-weighted SE imaging in the neck.

Thin-slice three-dimensional gradient-echo magnetic resonance imaging of the pituitary gland in healthy dogs

OBJECTIVE

To evaluate thin-slice 3-dimensional gradient-echo (GE) magnetic resonance imaging (MRI) of the pituitary gland in healthy dogs.

ANIMALS

11 healthy dogs.

PROCEDURES

By use of a 0.2-Tesla open magnet, MRI of the skull was performed with T1-weighted GE sequences and various protocols with variations in imaging plane, slice thickness, and flip angle before and after administration of contrast medium; multiplanar reconstructions were made. The pituitary region was subjectively assessed, and its dimensions were measured. Image quality was determined by calculation of contrast-to-noise and signal-to-noise ratios.

RESULTS

Best-detailed images were obtained with a T1-weighted GE sequence with 1-mm slice thickness and 30 degrees flip angle before and after administration of contrast medium. Images with flip angles > 50 degrees were of poor quality. Quality of multiplanar reconstruction images with 1-mm slices was better than with 2-mm slices. The bright signal was best seen without contrast medium. With contrast medium, the dorsal border of the pituitary gland was clearly delineated, but lateral borders were more difficult to discern.

CONCLUSIONS AND CLINICAL RELEVANCE

MRI of the canine pituitary gland with a 0.2-Tesla open magnet should include a T1-weighted GE sequence with 1-mm slice thickness and flip angle of 30 degrees before and after administration of contrast medium. The neurohypophysis was best visualized without contrast medium. The MRI examination permitted differentiation between the pituitary gland and surrounding structures.

Intracranial chondrosarcoma: a case report and review of the literature

OBJECTIVE AND IMPORTANCE

Chondrosarcomas rarely occur intracranially away from the skull base. We present a case of a supratentorial dural-based, low-grade classic chondrosarcoma and emphasize salient imaging findings that assist in its diagnosis.

CLINICAL PRESENTATION

A 23-year-old female presented with new onset seizures. Multiple radiographic imaging studies identified a large left frontal mass with radiological findings that suggested the correct diagnosis.

INTERVENTION

The patient underwent a left frontal craniotomy and gross total resection of the lesion and associated dura.

CONCLUSION

Intracranial chondrosarcomas away from the skull based are extremely rare malignancies. As with other extra-axial masses, they often grow to a relatively large size before generating symptoms. Careful analysis of CT, MR, and angiographic imaging characteristics should suggest the correct diagnosis.

Diagnosis of spinal arteriovenous malformations by MRI at 1.0 T

Eight patients were examined by magnetic resonance imaging (MRI) at 1.0 T; seven had an angiographically proved spinal intradural arteriovenous malformation and one had a hemangioblastoma of the spinal cord. Myelography was also performed in five and computed tomography (CT) in four patients. The clinical and radiological findings are presented. MRI revealed the location and extent of the lesion. Myelomalacia, edema, and hematomyelia were demonstrated in three patients. In our opinion MRI is the method of choice for the diagnosis of spinal arteriovenous malformation and facilitates spinal angiography, whereas myelography and CT do not provide any further information.

Unusual MR features in a case of completely thrombosed giant aneurysm of the posterior cerebral artery

An unusual case of completely thrombosed giant aneurysm of the left posterior cerebral artery, showing much more loss of signal on T2-weighted images compared with T2*-weighted images in the periphery of the thrombus is presented. Possible mechanism of this preferential signal loss on T2-weighted images is discussed.