Ellen G. Hoeffner

Computed tomography Perfusion of squamous cell carcinoma of the upper aerodigestive tract: Initial results

Objective To define the computed tomography (CT) perfusion characteristics of head and neck squamous cell carcinoma. Methods Fourteen consecutive patients with untreated squamous cell cancers of head and neck underwent CT of the head and neck along with CT perfusion imaging through the primary site. For the perfusion studies, CT density changes in blood and tissues were kinetically analyzed using the commercially available CT Perfusion 2 software (General Electric Medical Systems. Milwaukee, WI) on a GE Advantage Windows workstation. This yielded parameter maps of fractional tissue blood volume (mL/100 g), blood flow (mL · 100 g−1 · min−1), mean transit time (s), and microvascular permeability surface area product (mL · 100 g−1 · min−1). One head and neck radiologist analyzed perfusion data. Regions of interest (ROI) were placed over the primary tumor site, tongue base, and adjacent muscle groups. The average values of tissue blood volume (BV), blood flow (BF), mean transit time (MTT), and capillary permeability surface area product (CP) were then calculated for the tumor and compared with the average values for the tongue base and adjacent musculature. To determine a statistically significant difference between the tumor and muscle parameters, the Wilcoxon sign test, a nonparametric test for paired data, was employed. Results The average values of CP, BF, and BV were higher in primary tumor (41.9, 132.9, 6.2, respectively) than in tongue base or adjacent muscular structures. The MTT was reduced in primary tumors (4.0) compared with adjacent normal structures. The above differences were statistically significant (P < 0.05). Conclusions We obtained baseline perfusion data for head and neck squamous cell cancers and compared it with adjacent normal structures. Our initial results suggest that CT perfusion parameters (CP, BF, BV, and MTT) can be used to help differentiate head and neck squamous cell carcinoma (SCCA) from adjacent normal tissue.

Utility of Dual-Energy CT Virtual keV Monochromatic Series for the Assessment of Spinal Transpedicular Hardware-Bone Interface

OBJECTIVE Our aim was to evaluate the utility of dual-energy CT (DECT) virtual kilo-electron volt (keV) monochromatic images for the visualization of the transpedicular screw-bone interface after spinal fusion. MATERIALS AND METHODS This retrospective study included postfusion spine CT studies performed from October 2011 through April 2012 on a dual-energy 64-MDCT unit (Discovery CT750 HD). Studies were postprocessed on an Advantage Windows workstation (version 4.4) by two neuroradiologists with creation of monochromatic images from 40 to 140 keV. Each reader graded the screw-bone interfaces on the 70-keV images (used for clinical interpretation) and on the monochromatic series using a 5-point scale (1 [uninterpretable] to 5 [excellent]). The grades of the interfaces were compared using the Wilcoxon signed rank test to detect differences between the 70-keV image and the monochromatic series. RESULTS Ninety-two transpedicular screws in 10 patients were studied. Significant improvement in the visibility of the hardware-bone interface was seen on the monochromatic series compared with the 70-keV images: The median grade for the monochromatic series was 4 (range, 2-5) for both readers, whereas the median grade for the 70-keV images was 3 (range, 2-4) for reader 1 and 2 (range, 2-3) for reader 2 (both, p < 0.001). The interobserver agreement using weighted kappa was 0.51 for grading screw-bone interface visualization. The volume CT dose index was 29.5 mGy in all patients and the mean dose-length product was 805.2 mGy × cm. CONCLUSION Monochromatic images generated on gemstone spectral DECT are beneficial in the reduction of metallic streak artifact and enable better visualization of the hardware-bone interface than the 70-keV series in patients treated with spinal transpedicular screw fixation.

Stroke risk stratification in acute dizziness presentations: A prospective imaging-based study.

Objective: To estimate the ability of bedside information to risk stratify stroke in acute dizziness presentations. Methods: Surveillance methods were used to identify patients with acute dizziness and nystagmus or imbalance, excluding those with benign paroxysmal positional vertigo, medical causes, or moderate to severe neurologic deficits. Stroke was defined as acute infarction or intracerebral hemorrhage on a clinical or research MRI performed within 14 days of dizziness onset. Bedside information comprised history of stroke, the ABCD2 score (age, blood pressure, clinical features, duration, and diabetes), an ocular motor (OM)-based assessment (head impulse test, nystagmus pattern [central vs other], test of skew), and a general neurologic examination for other CNS features. Multivariable logistic regression was used to determine the association of the bedside information with stroke. Model calibration was assessed using low (<5%), intermediate (5% to <10%), and high (≥10%) predicted probability risk categories. Results: Acute stroke was identified in 29 of 272 patients (10.7%). Associations with stroke were as follows: ABCD2 score (continuous) (odds ratio [OR] 1.74; 95% confidence interval [CI] 1.20–2.51), any other CNS features (OR 2.54; 95% CI 1.06–6.08), OM assessment (OR 2.82; 95% CI 0.96–8.30), and prior stroke (OR 0.48; 95% CI 0.05–4.57). No stroke cases were in the models low-risk probability category (0/86, 0%), whereas 9 were in the moderate-risk category (9/94, 9.6%) and 20 were in the high-risk category (20/92, 21.7%). Conclusion: In acute dizziness presentations, the combination of ABCD2 score, general neurologic examination, and a specialized OM examination has the capacity to risk-stratify acute stroke on MRI.

Neuroradiology Back to the Future: Brain Imaging

SUMMARY: The beginning of neuroradiology can be traced to the early 1900s with the use of skull radiographs. Ventriculography and pneumoencephalography were introduced in 1918 and 1919, respectively, and carotid angiography, in 1927. Technical advances were made in these procedures during the next 40 years that lead to improved diagnosis of intracranial pathology. Yet, they remained invasive procedures that were often uncomfortable and associated with significant morbidity. The introduction of CT in 1971 revolutionized neuroradiology. Ventriculography and pneumoencephalography were rendered obsolete. The imaging revolution continued with the advent of MR imaging in the early 1980s. Noninvasive angiographic techniques have curtailed the use of conventional angiography, and physiologic imaging gives us a window into the function of the brain. In this historical review, we will trace the origin and evolution of the advances that have led to the quicker, less invasive diagnosis and resulted in more rapid therapy and improved outcomes.

Cerebral perfusion imaging.

There are multiple imaging techniques available to assess cerebral perfusion, including positron emission tomography (PET), xenon computed tomography (XeCT), single photon emission computed tomography (SPECT), perfusion-weighted MRI (PWI), and perfusion computed tomography (PCT). Current interest has focused mainly on their use in the setting of acute brain ischemia. Perfusion imaging may be able to distinguish infarcted from salvageable ischemic tissue as a guide to treatment. Perfusion techniques may also be helpful in cases of chronic ischemia, post-subarachnoid hemorrhage vasospasm, trauma, and contemplated therapeutic carotid artery occlusion.

Safety of Intravenous Thrombolytic Use in Four Emergency Departments Without Acute Stroke Teams

OBJECTIVES The objective was to evaluate safety of intravenous (IV) tissue plasminogen activator (tPA) delivered without dedicated thrombolytic stroke teams. METHODS This was a retrospective, observational study of patients treated between 1996 and 2005 at four southeastern Michigan hospital emergency departments (EDs) with a prospectively defined comparison to the National Institute of Neurological Disorders and Stroke (NINDS) tPA stroke study cohort. Main outcome measures were mortality, intracerebral hemorrhage (ICH), systemic hemorrhage, neurologic recovery, and guideline violations. RESULTS A total of 273 consecutive stroke patients were treated by 95 emergency physicians (EPs) using guidelines and local neurology resources. One-year mortality was 27.8%. Unadjusted Cox model relative risk (RR) of mortality compared to the NINDS tPA treatment and placebo groups was 1.20 (95% confidence interval [CI] = 0.87 to 1.64) and 1.04 (95% CI = 0.76 to 1.41), respectively. The rate of significant ICH by computed tomography (CT) criteria was 6.6% (odds ratio [OR] = 1.03, 95% CI = 0.56 to 1.90 compared to the NINDS tPA treatment group). The proportions of symptomatic ICH by two other prespecified sets of clinical criteria were 4.8 and 7.0%. The rate of any ICH within 36 hours of treatment was 9.9% (RR = 0.94, 95% CI = 0.58 to 1.51 compared to the NINDS tPA group). The occurrence of major systemic hemorrhage (requiring transfusion) was 1.1%. Functional recovery by the modified Rankin Scale score (mRS = 0 to 2) at discharge occurred in 38% of patients with a premorbid disability mRS < 2. Guideline deviations occurred in the ED in 26% of patients and in 25% of patients following admission. CONCLUSIONS In these EDs there was no evidence of increased risk with respect to mortality, ICH, systemic hemorrhage, or worsened functional outcome when tPA was administered without dedicated thrombolytic stroke teams. Additional effort is needed to improve guideline compliance.

Feasibility of superficial temporal artery as the input artery for cerebral perfusion CT

OBJECTIVE The purpose of this study was to determine whether the superficial temporal artery as a surrogate arterial input function, compared with the anterior cerebral artery as the arterial input function, generates accurate perfusion CT maps with significant correlates for cerebral blood flow, cerebral blood volume, and mean transit time. MATERIALS AND METHODS One hundred perfusion CT examinations performed on 90 patients (51 women and girls, 39 men and boys) were retrospectively reviewed and postprocessed by one investigator using CT perfusion software at a workstation. Color-coded cerebral blood flow, cerebral blood volume, and mean transit time maps were constructed with the superficial temporal artery as a surrogate arterial input function and the anterior cerebral artery as the arterial input function. The effect of input artery choice on mean cerebral blood flow, cerebral blood volume, and mean transit time values in six regions of interest (one region of interest in each anterior cerebral artery, middle cerebral artery, and posterior cerebral artery territory) was assessed. RESULTS All graphs of correlation between the anterior cerebral artery as the arterial input function and the superficial temporal artery as a surrogate arterial input function produced significant results (p < 0.0001). Excellent correlation existed between the cerebral blood flow (r = 0.96 [Pearson correlation coefficient]; rho(c) = 0.96 [concordance correlation coefficient]), cerebral blood volume (r = 0.97; rho(c) = 0.97), and mean transit time (r = 0.97; rho(c) = 0.97) values obtained with the anterior cerebral artery and the values obtained with the superficial temporal artery. Linear regression lines produced strong agreement between use of the anterior cerebral artery and use of the superficial temporal artery (cerebral blood flow, y = 1.03x + 0.65; cerebral blood volume, y = 1.05x - 0.09; mean transit time, y = 0.92x + 0.21). CONCLUSION The preliminary results show that using an extracranial vessel such as the superficial temporal artery as a surrogate input artery can generate perfusion maps comparable with those generated with an intracranial vessel such as the anterior cerebral artery. This knowledge can be useful if the proximal intracranial vessels typically used for arterial input are not visible owing to diffuse disease, such as diffuse vasospasm and atherosclerosis, or are not included in the field of view of perfusion CT.

Cerebral Blood Flow Alterations in Pain-Processing Regions of Patients with Fibromyalgia Using Perfusion MR Imaging

BACKGROUND AND PURPOSE: Widespread pain sensitivity in patients with FM suggests a CNS processing problem. The purpose of this study was to assess alterations in perfusion as measured by DSC in a number of brain regions implicated in pain processing between patients with FM and healthy controls. MATERIALS AND METHODS: Twenty-one patients with FM and 27 healthy controls underwent conventional MR imaging and DSC. For DSC, 12 regions of interest were placed in brain regions previously implicated in pain processing. rCBF values were calculated for each region of interest. Subjects answered mood/pain coping questionnaires and underwent clinical/experimental pain assessment. RESULTS: There were significant correlations between the thalamic rCBF values and the pain-control beliefs of FM subjects. The strength of the relationship between clinical pain measures and thalamic rCBF values increased after adjusting for pain-control beliefs. There was a significantly different distribution pattern of rCBF values across various brain regions between the FM group and the healthy controls. There was a lower degree of correlation in the FM group between the thalamic rCBF values and the other brain regions relative to the healthy controls. CONCLUSIONS: Significant correlations were found between thalamic rCBF values and pain belief values. These data suggest that there are baseline alterations of brain perfusion in patients with FM. rCBF values of the thalami exhibited lower correlations with respect to other brain regions thought to be involved in pain processing compared with those in healthy controls.

Applications of Magnetic Resonance Imaging in Adult Temporal Bone Disorders

Magnetic resonance (MR) imaging has new applications in the assessment of temporal bone disorders. This article summarizes current MR imaging applications in evaluating adult temporal bone lesions according to their location, beginning from the most common indication, vestibular schwannoma. Inner ear lesions, petrous lesions, and middle ear lesions are discussed, including the role of diffusion-weighted imaging in cholesteatomas, external ear lesions, and a few systemic conditions. Although this article emphasizes the role of MR imaging, the diagnostic value of computed tomography scan associated with MR imaging is also stressed. The main indications of temporal bone MR imaging are summarized.

Central Nervous System Complications of Oncologic Therapy.

Traditional and newer agents used to treat cancer can cause significant toxicity to the central nervous system. MRI of the brain and spine is the imaging modality of choice for patients with cancer who develop neurologic symptoms. It is important to be aware of the agents that can cause neurotoxicity and their associated imaging findings so that patients are properly diagnosed and treated. In some instances conventional MRI may not be able to differentiate posttreatment effects from disease progression. In these instances advanced imaging techniques may be helpful, although further research is still needed.