Unenhanced FLAIR images are of more value than spin-echo T2-weighted images for the diagnosis of intracranial meningeal carcinomatosis. Contrast-enhanced FLAIR images can sometimes surpass contrast-enhanced T1-weighted images in their quality.
Fig. 1-71-year-oldwoman with carcinoma ofthe bile duct. A, MRCP shows complete obstruction at level of confluence of cystic duct (arrowheads).Hydrops of the gallbladder (GB), which contains multiple stones and choledochal stone (arrow), is also shown.
B, Contrast-enhancedCT scan shows well-circumscribed jellybeanlike mass (arrow) at level of confluence of right (R) and left (L) hepatic ducts. This mass was seen to be connected to both gallbladder and bile duct on serial CT images (not shown We did not believe these findings to indicate an extrinsic mass effect on the common hepatic duct. CT showed a 25-mm well-circumscribed mass that was lateral to the portal vein (Fig. 7B)
We have implemented a new diffusion-weighted MRI (DWI) sequence based on the single-shot fast spin-echo technique. We hypothesised that this would add information to conventional MRI for diagnosis of lesions of the cervical spinal cord. DWI was performed using a technique in which echo collection after the application of motion-probing gradients was done in the same manner as in the single-shot fast spin-echo technique. We first imaged six healthy volunteers to demonstrate the cervical spinal cord using the sequence. Then we applied the sequence to 12 patients with cervical myelomalacia due to chronic cord compression. The spinal cord was well seen in all subjects without the distortion associated with echo-planar DWI. In the patients, lesions appeared as areas of low- or isointense signal on DWI. Calculated apparent diffusion coefficients of the lesions (3.30+/-0.38x10(-3) mm(2)/s) were significantly higher than those of normal volunteers (2.26+/-0.08x10(-3) mm(2)/s). Increased diffusion in areas of cervical myelomalacia, suggesting irreversible damage, can be detected using this technique.
We reviewed diffusion-weighted images (DWI) from eight patients with subdural and four with epidural empyemas to assess the possibility of differentiating between these lesions by DWI. The signal intensities of the empyemas on DWI, and maps of the apparent diffusion coefficient (ADC) were analysed in seven patients. In seven of the eight patients with subdural empyema, the lesions appeared as areas of high signal. The ADC maps confirmed that these areas were the result of restricted diffusion. (In the remaining patient, the lesion showed a mixture of high and low signal.) The epidural empyemas contained areas of low signal in all four patients; part of the empyema was isointense or gave high signal in two. DWI may be an adjunct to conventional sequences for differentiating between subdural and epidural empyemas.
HASTE (half-Fourier acquisition single-shot turbo spin echo) is a sequence that enables T2 weighted magnetic resonance (MR) images to be obtained in a few seconds. The purpose of this study was to evaluate the usefulness of this sequence in the diagnosis of fetal cerebral abnormalities. Five fetuses suspected of having cerebral abnormalities on ultrasound examination were studied by MR imaging using the HASTE sequence in utero. We compared the images with post-natal MR images or computed tomography (CT) scans. In four fetuses, the abnormality was diagnosed correctly, and the diagnosis was almost correct in the remaining fetus. This sequence is useful because it provides images of diagnostic quality in a very short scanning time.
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