Effect of a prescan patient-radiologist encounter on functional MR image quality.

BACKGROUND AND PURPOSE: A substantial number of clinical fMRI examinations inadequately assess language localization or lateralization, usually due to patient movement and suboptimal participation. We hypothesized that a prescan interview of the patient by the radiologist would reduce the fraction of nondiagnostic scans. MATERIALS AND METHODS: A single noise score for each acquisition was produced from time-series data on the basis of a weighted sum of 22 factors. Scores were recorded as the following quartiles: 0-5 = excellent, 5-10 = adequate, 10-15= marginal, and >15 = unacceptable. This measure was evaluated for 202 consecutive fMRI patients: 96 without and 106 with a physician prescan interview. The data were analyzed to compute the fraction of all nondiagnostic sequences and entire studies and were compared between the 2 groups. Image-noise characteristics included the SDs of linear and angular displacements of the head and the number of time-series outliers caused by focal motion. RESULTS: Of 999 sequences acquired, 539 had a prescan interview. The mean noise score significantly decreased for both individual sequence (from 7.9 to 6.3, P = <.001) and study-based (from 7.7 to 6.2, P = .05) methods. The fraction of sequences or studies scored as unacceptable decreased for sequence-based (from 15.2% to 10.9%, P = .04) and study-based (from 9.4% to 1.9%, P = .02) analyses. SDs of head motion decreased for linear (by 12%-14%, P < .01) and angular displacement (by 38%-48%, P < .001). The number of time-series spikes decreased by 10% (P = .004). CONCLUSIONS: We report that a prescan physician-patient interview modestly but significantly reduces fMRI noise scores. These results support the newly added billable costs of professional intervention before fMRI scans.

Pituitary stalk duplication in association with moya moya disease and bilateral morning glory disc anomaly - broadening the clinical spectrum of midline defects.

BACKGROUND: Duplication of the pituitary stalk, morning glory disc anomaly and moya moya are rare malformations. The combination of these findings may be syndromic and may have an underlying genetic etiology. METHODS: Case report and review of the literature of neurological, ophthalmological, and neuroradiological findings including ophthalmic examination, MRI and MRA. CASE REPORT: A 2 year-old girl presented with reduced visual acuity and roving eye movements since birth. Ophthalmological workup revealed bilateral morning glory disc anomaly. MRI showed duplication of the pituitary stalk and caudal displacement of the floor of the third ventricle. MRA showed narrowing of the supraclinoid internal carotid arteries with focal narrowing of the proximal middle cerebral arteries consistent with early moya moya disease. CONCLUSIONS: Review of the literature of pituitary gland duplication and of the combination of morning glory disc anomaly and moya moya disease revealed only one previously reported case. However, the spectrum of this possibly syndromic presentation may be much broader and include various types of anterior midline defects and may have a common underlying genetic cause.

MR imaging in epilepsy.

The advent of MR imaging techniques has immensely improved the ability to evaluate and manage patients with epilepsy. The principles of various MR techniques, the pertinent MRI neuro-anatomic features, and computer based 3D reconstruction post processing methods are discussed. Newer MR-based techniques such as magnetic resonance spectroscopy (MRS) and diffusion weighted imaging (DWI) and their applications and potential usefulness in the evaluation of patients with medically intractable epilepsy are also reviewed.

Hemorrhage detected using MR imaging in the setting of acute stroke: an in vivo model.

BACKGROUND AND PURPOSE: The treatment algorithm for acute cerebrovascular accidents has traditionally sorted these accidents as either hemorrhagic or nonhemorrhagic, and MR imaging, with its ability to allow expeditious assessment of vascular substrates and regional blood volume, is well suited for this purpose. Our purpose was to delineate the accuracy of MR imaging in acute, hemorrhagic forms of stroke during the time frame considered beneficial for intervention in an animal model. METHODS: Eighteen dogs with small, iatrogenic parenchymal, subarachnoid hemorrhage (SAH), or both were serially scanned over the initial 6-hour postictal period. Confirmatory pathologic specimens and 3-hour postictal CT scans were obtained in all animals. The MR and CT studies were then interpreted in a blinded fashion by two neuroradiologists for the presence of hemorrhage. The results were subjected to receiver operating characteristic analysis. RESULTS: MR imaging depicted acute parenchymal hemorrhage and SAH with a high degree of accuracy at 1.5 T. This finding was independent of each of the time points studied during the 6-hour window. For SAH, the MR accuracy for reader 1 was 0.86 (95% CI, 0.76-0.97); for reader 2, accuracy was 0.85 (95% CI, 0.71-0.99). The CT accuracy for the two readers was 0.42 (95% CI, 0.26-0.58) and 0.66 95% CI, 0.43-0.89), respectively. Fluid-attenuated inversion-recovery images improved the conspicuity of SAH on MR images and, along with spin-density-weighted spin-echo sequences, helped to establish the hemorrhagic nature. For parenchymal hemorrhage, the MR accuracy for reader 1 was 0.90 (95% CI, 0.81-0.99); for reader 2, accuracy was 0.93 (95% CI, 0.84-1.00). With CT, the accuracy of reader 1 was 0.91 (95% CI, 0.85-0.97) whereas for reader 2 accuracy was 0.76 (95% CI, 0.69-.83). Parenchymal hemorrhage detection and diagnosis was best with T2*-weighted gradient-echo images. CONCLUSION: MR imaging with appropriately selected sequences appears able to provide information regarding the presence (or absence) of hemorrhage in an acute stroke model requisite to the initiation of treatment.

Pulse sequences in lumbar spine imaging.

A host of different pulse sequences has been applied to MR imaging of the spine. As the routine evaluation of the spine has become quite standardized, much of the recent development has resulted in minor refinements of this process. This article outlines the pulse sequences commonly used for routine MR imaging of the lumbar spine and provides a critique of the newer sequences and the modifications of the conventional techniques.

Extensive intraosseous gas associated with lymphangiomatosis of bone: report of three cases.

Asymptomatic pneumatosis may be found in patients with lymphangiomatosis of bone. The authors report three cases from three institutions in which development of intraosseous gas in association with lymphangiomatosis of bone was found incidentally at imaging. Soft-tissue emphysema also developed in two cases. In all three cases, intraosseous gas developed after biopsy or surgery in the areas involved with lymphangiomatosis.

Segmented three-dimensional echo-planar flow imaging of the cervical carotid arteries.

PURPOSE: To implement and assess the application of segmented three-dimensional echo-planar MR imaging time-of-flight flow sequences for studying the anatomy of the cervical carotid arteries at 1.5 T. METHODS: The 3-D echo-planar sequences were segmented along the in-plane phase-encoding direction. Echo train lengths (ETLs) of 3 and 5 and signal bandwidths of +/-25, +/-33, and +/-50 KHz were tested along with a conventional (ETL = 1) 3-D MR flow study in six healthy volunteers and in five patients with known arteriosclerotic disease involving the carotid bifurcation as confirmed by conventional angiography. The volunteer data were used to rank the techniques with respect to vessel dimension, vessel/background contrast, and quality by four trained neuroradiologists. For the patient studies, the percentage of stenoses was measured for all MR studies and compared against the conventional angiographic data using the criteria of the North American Symptomatic Carotid Endarterectomy Trial. RESULTS: Using Wilcoxon's test statistic and a significance level of .05, we found that the conventional MR flow examination was better than the segmented techniques and that the segmented techniques with ETL of 3 were superior to their counterparts with ETL of 5. For the ETL of 3 techniques, the high-bandwidth studies were inferior to their lower bandwidth counterparts; however, there was no significant difference between the performance of the medium- and low-bandwidth sequences. The patient data revealed that the segmented techniques consistently overestimated the severity of stenosis; however, in no instance did any of the segmented examinations erroneously indicate the presence of disease. CONCLUSIONS: The reduction in acquisition time and the zero false-positive rate we obtained suggest that segmented 3-D echo-planar MR flow techniques may be used as a screening/locating study for cervical carotid artery disease.

High resolution, magnetization transfer saturation, variable flip angle, time-of-flight MRA in the detection of intracranial vascular stenoses.

OBJECTIVE: Factors that restrict 3D TOF MRA are limited resolution, saturation of flow, and degree of background suppression. We evaluated MRA for intracranial stenoses by using a 3D TOF technique that minimizes these factors. MATERIALS AND METHODS: Twenty-nine patients underwent MRA and intraarterial digital subtraction angiography (DSA). The MRA studies were performed on a 1.5 T Siemens SP 4000 system. Integrated techniques applied to the conventional 3D TOF acquisition included the following: (a) 256 x 256 matrix with a 140 mm FOV and 0.9 mm slice thickness, yielding a 0.54 x 0.54 x 0.9 mm3 voxel; (b) tilted optimized nonsaturating excitation (TONE); and (c) magnetization transfer saturation (MTS). The intraarterial DSA was performed on a Siemens Angiostar system with a 1,024 x 1,024 noninterpolated matrix. The MRAs were reviewed by two neuroradiologists. Two hundred seventy-seven vessels were evaluated for a total of 806 segments. Vessel segments were evaluated with a 5 point scale. RESULTS: The estimated accuracy of MRA for detecting stenosis over all intracranial vessel segments was 0.88 +/- 0.03 and 0.89 +/- 0.02 for the two readers, respectively. The estimated accuracy ranged from 0.94 +/- 0.02 and 0.93 +/- 0.02 for detecting internal carotid artery stenosis by the two readers, respectively, to 0.65 +/- 0.17 and 0.71 +/- 0.15 for detecting distal vertebral artery stenosis. In vessels determined by catheter angiography to be stenosis-free, reader confidence at the proximal versus distal segments was similar for the internal carotid, basilar, and posterior cerebral arteries. However, for the anterior and middle cerebral arteries, one or both readers were more confident in diagnosing the proximal segment. CONCLUSION: High resolution MTS TONE 3D TOF MRA is an accurate technique for the screening of medium and large vessel intracranial stenoses.

Intracranial aneurysms.

MR angiography provides a rapid, accurate, and extremely flexible noninvasive evaluation of intracranial aneurysms without the cost and risk of conventional angiography. TOF and phase contrast techniques each have specific advantages and disadvantages that can be selectively exploited to optimize aneurysm evaluation. Present indications for MR angiography in aneurysm evaluation include: (1) the presence of incidental findings on a CT or MR examination that suggest the possibility of aneurysm (Figs. 7 and 8), (2) when angiography is contraindicated or when the risk is too high, (3) non-invasive follow-up of patients with known aneurysms, (4) patient refusal of contrast angiography, and (5) evaluation of patients with specific clinical symptoms (i.e., third cranial nerve palsy) or patients with non-specific subacute symptoms in whom an aneurysm might explain the clinical presentation. Although MR angiography certainly can detect aneurysms with a high rate of sensitivity and specificity, detailed decision analyses generally have not supported the overall benefit of this type of screening. Future technical advances as well as advances in the overall understanding of aneurysms may one day prove unequivocally the benefit of MR angiography in screening high-risk patient groups. MR angiography has not yet been clinically evaluated as a tool in the evaluation of acute subarachnoid hemorrhage. Potential obstacles to such an evaluation include the clinical instability of SAH patients, limited spatial resolution of the MR angiography acquisitions, the potential for subarachnoid blood or focal intraparenchymal hematomas to obscure or mimic small aneurysms, and the unreliability of MR angiography in demonstrating vasospasm. Currently these factors continue to provide an integral role for contrast angiography in aneurysm evaluation.

Cervical radiculopathy.

Cervical radiculopathy refers to any disease process that compromises the cervical nerve roots. This article briefly reviews the normal anatomy of the cervical spine and the clinical presentation of patients with radiculopathy. Emphasis is then placed on the magnetic resonance evaluation of these patients, with focus on degenerative disease, the most common cause of cervical radiculopathy. Dramatic improvements have been appreciated in the magnetic resonance pulse sequences because they have evolved from standard two-dimensional spin echo studies to a combination of two-dimensional spin echo and three-dimensional gradient echo acquisitions. More recently, the gradient echo study has been replaced by hybrid RARE sequences and may soon be supplanted by a three-dimensional version of this sequence with the advent of advanced gradient capabilities of newer magnetic resonance imaging systems.

Hyperintense disks on T1-weighted MR images: correlation with calcification.

PURPOSE: To determine if calcification in the intervertebral disk is associated with hyperintensity on T1-weighted spin-echo magnetic resonance (MR) images. MATERIALS AND METHODS: Sagittal T1-weighted MR images that showed one or more hyperintense intervertebral disks and correlative computed tomographic (CT) scans, plain radiographs, or both, were obtained in 11 patients retrospectively and in 43 patients prospectively. Six patients underwent MR imaging with a fat-suppression technique. Histologic analysis of two disks was performed. RESULTS: Absence of calcification was associated with disks that were isointense relative to normal disks (P < .001), mild to moderate calcification was associated with hyperintense disks (P < .001 and P = .004 [two readers]), and both mild to moderate and marked calcifications were associated with hypointense disks (P < .001). Fat suppression resulted in a decrease in hyperintense signal in two patients. CONCLUSION: The results indicate that hyperintensity is associated with calcification. In the absence of clinical findings that suggest other causes, hyperintense disks are suggestive of degenerative disk disease.

Thoracic aortic disease: evaluation using a single MRA volume series.

OBJECTIVE: Use of MRA for thoracic aortic disease (TAD) evaluation has been limited. This report describes an initial experience with TAD evaluation using a single MRA volume series. MATERIALS AND METHODS: A single volume series, based on sequential 2D TOF MRA, was acquired in 30 cases (28 with suspected TAD and 2 normals). Each series was processed using multiplanar reconstruction (MPR) and maximum intensity projection (MIP); resulting tomographic (one base and two MPR) and MIP sets were blindly interpreted by four reviewers to detect TAD and, if present, to diagnose its specific form. For cases incorrectly interpreted, the standard MR images were subsequently interpreted. RESULTS: The TAD categories included aneurysm (n = 13), dissection (n = 9), and arch anomalies (n = 5). Sensitivities were high for TAD overall (89-100%) and TAD in ascending and descending portions; sensitivities were lower for TAD of the arch (two of four reviewers > or = 90% for TAD overall and descending TAD). Specificities for TAD overall had a wider range (67-100%), but were high for ascending, arch, and descending portions (three to four of four reviewers > or = 90% for each). Sensitivities for aneurysms (69-92%) and dissections overall (67-100%) were comparable, as they were in ascending and arch portions; descending dissection was better detected than descending aneurysm (two of four reviewers > or = 90% for ascending or arch aneurysm and for descending dissection); overall specificities (88-100 vs. 81-95%) and specificities in ascending, arch, and descending portions were also comparable (three to four of four reviewers > or = 90% for both in each portion; two of four reviewers > or = 90% for dissection overall). Each reviewer achieved > or = 70% diagnostic accuracy for TAD (one of four reviewers = 85%); accuracies for each category were comparable. Interpretation of standard MR images corrected all detection and most diagnostic (> or = 63%) errors. CONCLUSION: This initial experience with conventional TOF MRA for TAD evaluation is encouraging, but it indicates the potential for advancements in data acquisition and/or postprocessing.

Time-of-flight intracranial MR venography: evaluation of the sequential oblique section technique.

PURPOSE: To implement a time-of-flight MR angiographic technique using the oblique acquisition of thin gradient-echo sections to evaluate the intracranial venous system, and to assess the feasibility of application of this technique in a routine clinical setting. METHODS: The MR angiographic technique consisted of a two-dimensional gradient-echo technique with sequential overlapped sections obtained with an oblique orientation, angled from the sagittal toward the coronal plane. Parameters were evaluated during 41 measurements in 21 healthy volunteers with the section orientation varying from direct sagittal to direct coronal, followed by 64 examinations in 53 patients with an angle of obliquity of 15 degrees to 20 degrees from the sagittal toward the coronal plane. Confirmation of MR venographic findings was through correlation with clinical data and imaging studies. RESULTS: The volunteer data demonstrated optimal visibility of the smaller midline structures with an angle of obliquity of 15 degrees or greater. Patient examinations with this angle demonstrated sinus obstruction or thrombosis (n = 11), sinus compression (n = 2), and apparent sinus stenosis (n = 1). CONCLUSIONS: Oblique-acquisition time-of-flight MR venography seems to provide a rapid, robust technique for intracranial venous examination and can be applied as a useful adjunct to parenchymal MR in the evaluation of suspected venoocclusive disease. This oblique technique demonstrated improved vessel contrast over direct sagittal acquisition, required significantly fewer sections and thus a shorter acquisition time than direct coronal acquisition, and was applied without difficulty in the vast majority of patients in the clinical setting.

Occult intracranial aneurysms in polycystic kidney disease: screening with MR angiography.

PURPOSE: To estimate the prevalence, location, and type of cerebral aneurysms in patients with adult polycystic kidney disease (PCKD) and identify associated risk factors. MATERIALS AND METHODS: Ninety-three patients with PCKD were screened for aneurysms with spin-echo parenchymal magnetic resonance (MR) imaging and three-dimensional time-of-flight MR angiography. Prevalence was estimated with the calculated proportions of patients who had aneurysms, adjusted for reported sensitivity and specificity of MR angiography. RESULTS: Thirteen aneurysms, found in 10 patients, were 7 mm or smaller in largest dimension; 11 of these aneurysms were saccular. Intra- and interobserver variabilities were 96%-98%. Conventional arteriograms, obtained in six patients, helped confirm the MR angiographic findings. The best estimates of prevalence of aneurysms were 11.7% in the study group (n = 93) and 25.8% in patients with a family history of aneurysms (n = 6). CONCLUSION: The prevalence of aneurysms in the study group was greater than in the general population. MR angiography is useful in screening for cerebral aneurysms.

Pulse sequence strategies for vascular contrast in time-of-flight carotid MR angiography.

A systematic evaluation in healthy volunteers of the relative efficacy of various techniques for background suppression to improve two-dimensional (2D) and three-dimensional (3D) time-of-flight magnetic resonance angiography of the cervical carotid arteries was performed. Conventional 2D and 3D FISP (fast imaging with steady-state precession) sequences with flow compensation were compared with modifications of these sequences, including a tracking saturation pulse (2D), prolonged absolute TEs for fat suppression based on T2* decay (2D and 3D), frequency-selective saturation of fat (2D and 3D), in-plane spatial saturation (2D), and magnetization transfer contrast (2D and 3D). The tracking saturation pulse and slight overlap of the excitation sections provided uniform background suppression without impairing depiction of the morphology of the cervical carotid arteries. Frequency-selective fat saturation was the most effective background suppression scheme among the 2D and 3D techniques but was occasionally compromised by local field inhomogeneities. Magnetization transfer contrast provided little suppression of stationary tissues in the neck because of the intrinsic limitations of the coil. In-plane spatial saturation yielded the highest background suppression but reduced apparent arterial diameters and could not be implemented in a 3D version. The T2* decay method not only reduced the apparent size of the vessels but also their signal intensity.

Three-dimensional time-of-flight MR angiography with a specialized gradient head coil.

A gradient head coil has been developed, incorporating two independent gradients within the conventional body coil of the magnetic resonance (MR) system, with reduced rise times (200 microseconds) and maximum amplitudes of 37 and 18 mT/m in the z and y directions, respectively. This gradient coil was systematically evaluated by testing two-dimensional (2D) and three-dimensional (3D) time-of-flight (TOF) MR angiography sequences applied to a pulsatile flow phantom simulating a carotid stenosis and the intracranial vasculature. When standard 2D and 3D TOF MR angiography techniques were used to image the carotid stenosis model, dramatic signal loss in the stenotic segment and a large flow void distal to the stenosis were seen. The shorter (3.8 msec) absolute echo times (TEs) achievable with the gradient coil in 3D sequences substantially reduced the phase dispersion and associated signal loss in the region of stenosis. Shorter TEs alone (3.2 msec) did not minimize signal loss, and first-order flow compensation in the read and section-select directions provided further improvements (despite slightly longer TEs). Reduction of TEs in 2D sequences yielded relatively poor results regardless of the refocusing scheme or TE. This study confirms the predicted benefits of a dedicated coil with improved gradient capabilities for 3D MR angiography. The study suggests the limitations of 2D TOF MR angiography in the evaluation of severe stenoses.

3D MRI of the cervical spine: low flip angle FISP vs. Gd-DTPA TurboFLASH in degenerative disk disease.

The authors undertook this study to compare bright and dark CSF three-dimensional (3D) gradient-echo (GE) MR techniques to answer the following questions: Could a single Gd-DTPA enhanced T1-weighted GE volume sequence (with multiplanar reformats) be diagnostically equivalent for degenerative cervical disk disease to a standard sequence consisting of sagittal T1-weighted spin echo and axial low flip angle volume GE images (with reformatted images)? Does performing oblique coronal reformats perpendicular to the course of exiting cervical nerve roots improve diagnostic confidence over axial images alone? Thirty-one consecutive patients received a "routine" MR examination consisting of a sagittal T1-weighted spin echo and axial low flip angle volume sequence (FISP) [(35/7/5), 64 slices, 2 mm slice thickness, 192 x 256 matrix, 7.2 min]. Each patient was then given 0.1 mmol/kg Gd-DTPA intravenously, and reimaged with a T1-weighted volume GE sequence [(13/6/12), acquired as 128-1.2 mm coronal partitions, 192 x 256 matrix, 5.5 min]. Sequences were reconstructed on the standard diagnostic console in 1 mm increments. Sets of examinations (routine vs T1-weighted volume) were independently interpreted by three neuroradiologists for location, type, and severity of extradural degenerative disease. There was no strong or consistent trend for increased detection of disease by one imaging sequence over the other. For lateral disk disease, only 3% of the observations were in discordance. For disk disease, there was close agreement in the severity scores. All readers indicated that additional information was provided by the reformatted images more frequently with TurboFLASH (fast low angle shot) than with FISP. All readers indicated that increased confidence was provided by the reformatted images more frequently with TurboFLASH than with FISP. A single 3D contrast-enhanced TurboFLASH sequence is diagnostically equivalent to a set of two-dimensional T1-weighted sagittal spin echo and 3D axial low flip angle sequences for assessing the location and degree of cervical extradural degenerative disease. A screening examination of the cervical spine could be performed with a single contrast-enhanced 5.2 min study, and then relying on computer postprocessing to provide additional imaging planes.