Multisection CT: scanning techniques and clinical applications.

Multisection computed tomography (CT) was introduced in 1992 with the advent of dual-section-capable scanners and was improved in 1998 following the development of quad-section technology. With a recent increase in gantry speed from one to two revolutions per second, multisection CT scanners are now up to eight times faster than conventional single-section helical CT scanners. The benefits of quad-section CT relative to single-section helical CT are considerable. They include improved temporal resolution, improved spatial resolution in the z axis, increased concentration of intravascular contrast material, decreased image noise, efficient x-ray tube use, and longer anatomic coverage. These factors substantially increase the diagnostic accuracy of the examination. The multisection CT technique has enabled faster and superior evaluation of patients across a wide spectrum of clinical indications. These include isotropic viewing, musculoskeletal applications, use of multiplanar reformation in special situations, CT myelography, long coverage and multiphase studies, CT angiography, cardiac scoring, evaluation of brain perfusion, imaging of large patients, evaluation of acute chest pain or dyspnea, virtual endoscopy, and thin-section scanning with retrospective image fusing. Multisection CT is superior to single-section helical CT for nearly all clinical applications.

Temporal bone: comparison of isotropic helical CT and conventional direct axial and coronal CT.

OBJECTIVE: The objective of the study was to compare helical CT (with reformation of coronal images from the axial data set) with conventional direct axial and coronal CT of the temporal bones. SUBJECTS AND METHODS: Nineteen patients underwent both conventional 1-mm direct axial and coronal CT and helical 0.5-mm axial CT. The helical data set was reconstructed at 0.2-mm increments, and axial and coronal images were reconstructed in a plane similar to that of the conventional study, with a slice width of 0.5 mm and 0.5-mm increments. Forty small structures were evaluated independently by three observers, who were unaware of the method of imaging. Observers graded the 40 structures using a modified Likert scale. The graded differences between the two techniques were evaluated using a paired t test. Correlation between observers' gradings was evaluated using analysis of variance. RESULTS: The helical CT technique scored significantly higher than the conventional technique for many individual structures and groups of structures (scutum [p = .041], stapes footplate [p = .006], stapes crura [p = .004], oval window [p = .026], crista falciformis [p = .006], whole temporal bone [P = .012], middle ear [p = .033], inner ear [p = .021], ossicles [p = .044], and stapes [p = .010]). The correlation coefficient among observers was .91 for the whole temporal bone. CONCLUSION: Helical CT using 0.5-mm technique and reconstruction produces diagnostic images comparable with or superior to conventional 1-mm technique because helical CT can obtain thinner slices.

Brain: gadolinium-enhanced fast fluid-attenuated inversion-recovery MR imaging.

PURPOSE: To determine the clinical utility of gadolinium-enhanced fluid-attenuated inversion-recovery (FLAIR) magnetic resonance (MR) imaging of the brain by comparing results with those at gadolinium-enhanced T1-weighted MR imaging with magnetization transfer (MT) saturation. MATERIALS AND METHODS: In 105 consecutive patients referred for gadolinium-enhanced brain imaging, FLAIR and T1-weighted MR imaging with MT saturation were performed before and after administration of gadopentetate dimeglumine (0.1 mmol per kilogram of body weight). Pre- and postcontrast images were evaluated to determine the presence of abnormal contrast enhancement and whether enhancement was more conspicuous with the FLAIR or T1-weighted sequences. RESULTS: Thirty-nine studies showed intracranial contrast enhancement. Postcontrast T1-weighted images with MT saturation showed superior enhancement in 14 studies, whereas postcontrast fast FLAIR images showed superior enhancement in 15 studies. Four cases demonstrated approximately equal contrast enhancement with both sequences. Six cases showed some areas of enhancement better with T1-weighted imaging with MT saturation and other areas better with postcontrast fast FLAIR imaging. Superficial enhancement was typically better seen with postcontrast fast FLAIR imaging. CONCLUSION: Fast FLAIR images have noticeable T1 contrast making gadolinium-induced enhancement visible. Gadolinium enhancement in lesions that are hyperintense on precontrast FLAIR images, such as intraparenchymal tumors, may be better seen on T1-weighted images than on postcontrast fast FLAIR images. However, postcontrast fast FLAIR images may be useful for detecting superficial abnormalities, such as meningeal disease, because they do not demonstrate contrast enhancement of vessels with slow flow as do T1-weighted images.

Neuroradiologic review of intracranial infection.

The detection of intracranial infection continues to be a common reason for neuroradiologic examination. This review covers the neuroradiologic findings of the variety of common infections. It includes meningitis and its complications, as well as bacterial, viral, tuberculous, fungal, and parasitic diseases. Finally, a review of the common infections associated with AIDS is presented. With an increased ability to recognize such infections, radiologists should be able to supply their clinical colleagues with more specific diagnoses.

CT-Guided Percutaneous Fine-Needle Aspiration Biopsy of Posterior Skull Base Lesions.

We describe a retroauricular approach, adjacent to the mastoid tip, in two patients that allowed successful biopsy of posterior skull base lesions. Diagnoses were central giant cell granuloma, an unusual tumor rarely reported in the skull base, and meningioma. In both patients, the needle biopsy accurately identified the pathology found at surgery. The described approach may allow biopsy of posterior lesions that are inaccessible with other methods.

Topical contrast-enhanced CT and MR dacryocystography: imaging the lacrimal drainage apparatus of healthy volunteers.

OBJECTIVE: The purpose of this study was to evaluate the feasibility of administering topical contrast material during helical CT dacryocystography and topical saline solution during MR dacryocystography to reveal the lacrimal drainage apparatus. SUBJECTS AND METHODS: Fourteen healthy volunteers underwent helical CT dacryocystography, MR dacryocystography, or both. Eight of the 14 subjects underwent both techniques; three subjects underwent MR dacryocystography, and three subjects underwent CT dacryocystography. Images were evaluated by two radiologists for degree of visualization of components of the lacrimal drainage apparatus. Each volunteer was questioned about the relative discomfort of contrast material and saline solution administration. RESULTS: The lacrimal drainage system was seen on both CT dacryocystography and MR dacryocystography. CT dacryocystography allowed two-dimensional and three-dimensional reconstructions on which adjacent bone anatomy could be seen. The MR dacryocystography two-dimensional reconstructions and maximum intensity projections also showed the drainage apparatus. However, smaller drainage structures were more consistently seen on CT dacryocystography than on MR dacryocystography. Saline solution was more comfortable than contrast material. CONCLUSION: CT dacryocystography and MR dacryocystography reproducibly and non-invasively revealed the lacrimal drainage apparatus and allowed a better physiologic examination than cannulation dacryocystography. MR dacryocystography can be performed without administration of ionizing radiation or contrast material, but this technique cannot show adjacent bone anatomy and less consistently showed the smaller drainage structures than CT dacryocystography.

Engorged anterior epidural venous plexus mimics an anterior epidural mass.

A 48-year-old woman presented with severe neck pain on flexion 1 week after a reportedly uncomplicated lumbar puncture, and with a slightly elevated white blood cell count. Magnetic resonance imaging showed an anterior epidural mass that was thought to represent an epidural abscess. At surgery, the epidural "mass" was due to an engorged anterior epidural venous plexus.

Clinical and surgical application of reformatted high-resolution CT of the temporal bone.

High resolution CT has played a pivotal role in temporal bone imaging since the early 1980s. Although the appearance of MR imaging technology with its superior demonstration of fluid-containing spaces of the inner ear and the posterior fossa structures, CT continues to offer distinct advantages for the evaluation of conductive hearing loss, and petrous apex lesions. With the advent of helical scanning techniques, CT is increasingly the imaging study of choice for definitive preoperative temporal bone imaging.