Unruptured Arteriovenous Malformations in the Multidetector Computed Tomography Era: Frequency of Detection and Predictable Failures.

OBJECTIVES: While hemorrhage arising from ruptured arteriovenous malformations (AVMs) is usually evident on multidetector non-contrast computed tomography (NCCT), unruptured AVMs can be below the limits of detection. We performed a retrospective review of NCCT of patients with a proven diagnosis of unruptured AVM to determine if advances in CT technology have made them more apparent and what features predict their detection. MATERIAL AND METHODS: Twenty-five NCCTs met inclusion criteria of having angiography or MR proven AVM without hemorrhage, prior surgery, or other CNS disease. Demographic variables, clinical symptoms at presentation, abnormal CT imaging findings, attenuation of the superior sagittal sinus (SSS), and Spetzler-Martin grade of each AVM were recorded. We examined the relationship between AVM detection and SSS attenuation through Kruskal-Wallis test. Exploratory serial logistic principal components analysis was performed including demographics, symptoms, and CT features in the multivariate model. RESULTS: About 80% of the NCCTs showed an abnormality while 20% were normal. All those with an identifiable abnormality showed hyperdensity (80%). Logistic regression models indicate that clustered associations between several CT features, primarily calcifications, hyperdensity, and vascular prominence significantly predicted Spetzler-Martin grade (likelihood ratio 7.7, P = 0.006). SSS attenuation was significantly lower in subjects with occult AVMs when compared to those with CT abnormalities (median 47 vs. 55 HU, P < 0.04). CONCLUSION: Abnormal hyperdensity was evident in all detectable cases (80%) and multiple CT features were predictive of a higher Spetzler-Martin AVM grade. Moreover, SSS attenuation less than 50 HU was significantly correlated with a false-negative NCCT.

Economic impact of selective use of contrast for routine follow-up MRI of patients with multiple sclerosis.

BACKGROUND AND PURPOSE: Imaging and autopsy studies show intracranial gadolinium deposition in patients who have undergone serial contrast-enhanced MRIs. This observation has raised concerns when using contrast administration in patients who receive frequent MRIs. To address this, we implemented a contrast-conditional protocol wherein gadolinium is administered only for multiple sclerosis (MS) patients with imaging evidence of new disease activity on precontrast imaging. In this study, we explore the economic impact of our new MRI protocol. METHODS: We compared scanner time and Medicare reimbursement using our contrast-conditional methodology versus that of prior protocols where all patients received gadolinium. RESULTS: For 422 patients over 4 months, the contrast-conditional protocol amounted to 60% decrease in contrast injection and savings of approximately 20% of MRI scanner time. If the extra scanner time was used for performing MS follow-up MRIs in additional patients, the contrast-conditional protocol would amount to net revenue loss of $21,707 (∼3.7%). CONCLUSIONS: Implementation of a new protocol to limit contrast in MS follow-up MRIs led to a minimal decrease in revenue when controlled for scanner time utilized and is outweighed by other benefits, including substantial decreased gadolinium administration, increased patient comfort, and increased availability of scanner time, which depending on type of studies performed could result in additional financial benefit.

Calcifications of the Medial Choroid in the Velum Interpositum: An Unrecognized Site of Physiologic Calcifications Evident on Multidetector Computed Tomography.

OBJECTIVE: In adult patients undergoing multidetector computed tomography (CT) of the brain, we observed linear calcification along the deep venous system on thin (<3 mm) sagittal reconstructions. We found no reports of this finding in the velum interpositum (VI) in the imaging literature. We performed a focused examination of the VI on 2 autopsy cases and retrospectively reviewed sagittal, thin-section reconstructions of CT scans of 273 consecutive adult patients. METHODS: On 2 routine autopsies of the brain, sampling and histologic evaluation was performed of structures within the VI. A series of 273 unselected, sequentially acquired clinical head CT scans of patients ≥60 years old were retrospectively reviewed on a three-dimensional workstation to determine the incidence of this finding and its correlation with patient age. RESULTS: In 1 of the autopsy cases, calcified choroid plexus was identified in the region of the VI; this was also visible on the patient's premorbid CT. In the series of CT scans, linear calcification of ≥9 mm along the deep venous system was evident in 24.5% of cases. The median age of the cases without calcifications was 72 years, while the median age of the cases with calcification was 82; this difference was statistically significant (χ2, P < 0.0005). CONCLUSIONS: Evidence supports that linear midline calcification along the internal cerebral veins represents age-related, physiologic calcification of extraventricular choroid plexus within the VI. Awareness of this previously unreported finding on CT will prevent mistaking these physiologic calcifications on CT for evidence of underlying venous pathology. This finding provides additional support that the midline choroid plexus lies within the VI rather than in the third ventricle and expands our understanding of the detailed anatomy of the VI.

Magnetic Eyelashes: A New Source of MRI Artifacts.

OBJECTIVE. The purpose of this study was to show, by use of a phantom, that magnetic eyelashes worn in the MRI environment can cause substantial artifact and that detachment of the eyelashes from the phantom can occur. CONCLUSION. A new cosmetic product, magnetic eyelashes, should be of interest and concern to radiologists and technologists working in the MRI environment. We strongly recommend inserting a line about magnetic eyelashes on the MRI safety questionnaire and adding stops in the screening system to prevent the entry of anyone with these lashes, including staff, into the MRI scanner room.

An Initiative to Reduce Unnecessary Gadolinium-Based Contrast in Multiple Sclerosis Patients.

OBJECTIVE: Patients with multiple sclerosis (MS) routinely undergo serial contrast-enhanced MRIs. Given concerns regarding tissue deposition of gadolinium-based contrast agents (GBCAs) and evidence that enhancement of lesions is only seen in patients with new disease activity on noncontrast imaging, we set out to implement a prospective quality improvement project whereby intravenous contrast would be reserved only for patients with evidence of new disease activity on noncontrast images. METHODS: To prospectively implement such a protocol, we leveraged our in-house computer-assisted detection (CAD) software and 3-D laboratory radiology technologists to perform real-time preliminary assessments of the CAD-processed T2 fluid attenuated inversion recovery (FLAIR) noncontrast images as a basis for deciding whether to inject contrast. Before implementation, we held multidisciplinary meetings with neurology, neuroradiology, and MR technologists and distributed surveys to objectively assess opinions and obstacles to clinical implementation. We evaluated reduction in GBCA utilization and technologist performance relative to final neuroradiologist interpretations. RESULTS: During a 2-month trial period, 153 patients were imaged under the new protocol. Technologists using the CAD software were able to identify patients with new or enlarging lesions on FLAIR images with 95% accuracy and 97% negative predictive value relative to final neuroradiologist interpretations, which allowed us to avoid the use of contrast and additional imaging sequences in 87% of patients. DISCUSSION: A multidisciplinary effort to implement a quality improvement project to limit contrast in MS patients receiving follow-up MRIs allowed for improved safety and cost by targeting patients that would benefit from the use of intravenous contrast in real-time.

Perilesional Hyperintensity on T1-Weighted Images in Intra-Axial Brain Masses other than Cavernous Malformations.

BACKGROUND AND PURPOSE: Hyperintensity on T1-weighted imaging in perilesional vasogenic edema has been reported as a useful sign for differentiating cavernous malformation from other hemorrhagic intra-axial masses. In this study, we investigated the frequency of perilesional hyperintensity on T1-weighted imaging in patients with intra-axial hemorrhagic and nonhemorrhagic brain masses. METHODS: The study was performed with the approval of the institutional review board. Magnetic resonance images of 218 patients with 282 intra-axial brain masses (129 metastases, 46 gliomas, 18 primary central nervous system lymphomas [PCNSLs], 25 intracerebral hemorrhages, 50 cavernous malformations, and 14 patients with brain abscesses) were evaluated. The signal intensity in perilesional area was qualitatively evaluated on T1-weighted sequences. In addition, signal intensity in perilesional area was quantitatively measured on T1-weighted sequences and normalized to the contralateral white matter. RESULTS: Hyperintensity on T1-weighted imaging in perilesional vasogenic edema was found in 12 (9%) of 129 metastases, 8 (16%) of 50 cavernous malformations, 1 (4%) in 25 nonneoplastic intracerebral hemorrhages, and none of the patients with high-grade glioma, PCNSL, or abscess. All of the lesions with perilesional hyperintensity showed either acute or subacute hemorrhage. Pairwise comparison of qualitative hyperintensity on T1-weighted imaging demonstrated no significant difference between the groups. Perilesional hyperintensity on T1-weighted imaging showed high specificity in both metastasis and cavernous malformation groups (94%). CONCLUSION: Perilesional hyperintensity on T1-weighted imaging is not limited to cavernous malformations and frequently evident with melanoma and other hemorrhagic metastasis to the brain. In our experience, it was not seen in high-grade glioma, PCNSL, and brain abscess.

The Many Faces of Cerebral Developmental Venous Anomaly and Its Mimicks: Spectrum of Imaging Findings.

Developmental venous anomalies (DVAs) are the most common cerebral vascular malformations and are usually found incidentally on neuroimaging studies. Despite the benign nature of DVAs, occasionally, they can be symptomatic. The objective of this article is to review the spectrum of imaging findings of DVAs on conventional and advanced imaging studies. In addition, neuroimaging findings of symptomatic DVAs as well as imaging mimicks will also be described to assist in the approach to differential diagnosis.

Utility of fat-suppressed sequences in differentiation of aggressive vs typical asymptomatic haemangioma of the spine.

OBJECTIVE: While haemangiomas are common benign vascular lesions involving the spine, some behave in an aggressive fashion. We investigated the utility of fat-suppressed sequences to differentiate between benign and aggressive vertebral haemangiomas. METHODS: Patients with the diagnosis of aggressive vertebral haemangioma and available short tau inversion-recovery or T2 fat saturation sequence were included in the study. 11 patients with typical asymptomatic vertebral body haemangiomas were selected as the control group. Region of interest signal intensity (SI) analysis of the entire haemangioma as well as the portion of each haemangioma with highest signal on fat-saturation sequences was performed and normalized to a reference normal vertebral body. RESULTS: A total of 8 patients with aggressive vertebral haemangioma and 11 patients with asymptomatic typical vertebral haemangioma were included. There was a significant difference between total normalized mean SI ratio (3.14 vs 1.48, p = 0.0002), total normalized maximum SI ratio (5.72 vs 2.55, p = 0.0003), brightest normalized mean SI ratio (4.28 vs 1.72, p < 0.0001) and brightest normalized maximum SI ratio (5.25 vs 2.45, p = 0.0003). Multiple measures were able to discriminate between groups with high sensitivity (>88%) and specificity (>82%). CONCLUSION: In addition to the conventional imaging features such as vertebral expansion and presence of extravertebral component, quantitative evaluation of fat-suppression sequences is also another imaging feature that can differentiate aggressive haemangioma and typical asymptomatic haemangioma. ADVANCES IN KNOWLEDGE: The use of quantitative fat-suppressed MRI in vertebral haemangiomas is demonstrated. Quantitative fat-suppressed MRI can have a role in confirming the diagnosis of aggressive haemangiomas. In addition, this application can be further investigated in future studies to predict aggressiveness of vertebral haemangiomas in early stages.

Leukostasis in an Adult with AML Presenting as Multiple High Attenuation Brain Masses on CT.

Acute myeloid leukemia (AML) is a hematologic malignancy that can present with central nervous system (CNS) symptoms. Neurological symptoms may result from the local accumulation of malignant cells in or near the brain (chloroma), infection, hemorrhage, or infarcts from leukostasis. Leukostasisis a syndrome that can include brain infarction due hyperviscosity of blood with vascular occlusion but CNS involvement is rarely encountered in adults. We report an unusual case of leukostasis in an adult who presented with multiple high attenuation intracranial masses on CT. While initially thought to represent chloromasthey proved to be hemorrhagic infarcts secondary toleukostasis on open brain biopsy. This condition is under-reported in the radiology literature and only rarely biopsy proven. We review in this paper the pathological, CT and MRI findings of leukostasis in order to increase awareness of this uncommon entity and facilitate diagnosis.

Absence of abnormal vessels in the subarachnoid space on conventional magnetic resonance imaging in patients with spinal dural arteriovenous fistulas.

Spinal dural arteriovenous fistula (DAVF) is an uncommon condition that can be difficult to diagnose. This often results in misdiagnosis and treatment delay. Although conventional MRI plays an important role in the initial screening for the disease, the typical MRI findings may be absent. In this article, the authors present a series of 4 cases involving patients with angiographically proven spinal DAVFs who demonstrated cord T2 prolongation on conventional MRI but without abnormal subarachnoid flow voids or enhancement. These cases suggest that spinal DAVF cannot be excluded in symptomatic patients with cord edema based on conventional MRI findings alone. Dynamic Gd-enhanced MR angiography (MRA) was successful in demonstrating abnormal spinal vasculature in all 4 cases. This limited experience provides support for the role of spinal MRA in patients with abnormal cord signal and symptoms suggestive of DAVF even when typical MRI findings of a DAVF are absent.