Robert Yeung

Certainty of Stroke Diagnosis: Incremental Benefit with CT Perfusion over Noncontrast CT and CT Angiography

PURPOSE To systematically evaluate the diagnostic benefits and inter- and intraobserver reliability of an incremental computed tomographic (CT) protocol in the confirmation of clinically suspected stroke, with combined imaging and clinical data as the reference standard. MATERIALS AND METHODS Institutional review board approval was obtained, and participants gave informed consent. A total of 191 patients (mean age, 67 years +/- 16 [standard deviation]; 105 men) with strokelike symptoms of no more than 3 hours duration were recruited. Blinded review was performed by four readers with limited stroke imaging experience. Diagnostic confidence was recorded on a five-point scale. Logistic regression analysis was used to calculate the difference between the real and observed diagnoses, adjusting for confidence. Predictive effects of observed diagnostic performance and confidence score were quantified with the entropy r(2) value. Sensitivity, specificity, and confidence intervals were calculated while accounting for multiple reader assessments. Receiver operating characteristic (ROC) analyses, including area under the ROC curve, were conducted for three modalities in combination with confidence score. Inter- and intraobserver agreement was established with the Cohen kappa statistic. RESULTS The final diagnosis was infarct in 64% of the patients, transient ischemic attack in 18%, and stroke mimic in 17%. Large-vessel occlusion occurred in 70% of the patients with an infarct. Sensitivity for stroke determination with noncontrast CT, CT angiography, and CT perfusion increased by 12.4% over that with noncontrast CT and CT angiography and by 18.2% over that with only noncontrast CT for a confidence level of 4 or higher. The incremental protocol was more likely to enable confirmation of clinical stroke diagnosis (odds ratio, 13.3) than was noncontrast CT and CT angiography (odds ratio, 6.4) or noncontrast CT alone (odds ratio, 3.3), The area under the ROC curve was 0.67 for the combination of noncontrast CT and confidence score, 0.72 for the combination of CT angiography and confidence score, and 0.81 for the combination of CT perfusion and confidence score. Inter- and intraobserver agreement increased with progressive sequence use. CONCLUSION An incremental stroke protocol that includes CT perfusion increases diagnostic performance for stroke diagnosis and inter- and intraobserver agreement.

Characterization of Carotid Plaque Hemorrhage A CT Angiography and MR Intraplaque Hemorrhage Study

Background and Purpose— The main objective of this study was to evaluate CT angiographic (CTA) features that are able to predict the presence of intraplaque hemorrhage (IPH) as defined by MR-IPH. Methods— One hundred sixty-seven consecutive patients (mean age 69 years, SD 12.8; 58 females) underwent both MR-IPH and CTA within 3 weeks. MR-IPH, the gold standard, was performed at 1.5 T using a neurovascular phased-array coil as a coronal T1-weighted 3-dimensional fat-suppressed acquisition. CTA was performed using a 4-slice or a 64-slice CT machine and evaluated, blinded to MR-IPH findings, for carotid stenosis, plaque density, and plaque ulceration. Plaque density was defined as the mean attenuation of plaque at the site of maximum stenosis and 2 sections above and below. Plaque ulceration was defined as outpouching of contrast into the plaque at least 2 mm deep on any single plane. Results— Prevalence of IPH increased at higher degrees of carotid stenosis. Mean CT plaque density was higher for plaques with MRI-defined IPH (47 Hounsfield units) compared with without IPH (43 Hounsfield units; P=0.02). However, significant overlap between distributions of plaque densities limited the value of mean plaque density for prediction of IPH. CTA plaque ulceration had high sensitivity (80.0% to 91.4%), specificity (93.0% to 92.3%), positive predictive value (72.0% to 71.8%), and negative predictive value (95.0% to 97.9%) for prediction of IPH. Interobserver agreement for presence/absence of CTA plaque ulceration was excellent (&kgr;=0.80). Conclusions— CTA plaque ulceration, but not mean CTA plaque density, was useful for prediction of IPH as defined by the MR-IPH technique.

Comparison of CTA to DSA in Determining the Etiology of Spontaneous ICH

BACKGROUND AND PURPOSE To compare the efficacy of computed tomographic angiography (CTA) to that of digital subtraction angiography (DSA) in the detection of secondary causes of intracerebral hemorrhage (ICH). METHODS Between January 2001 and February 2007 there were 286 patients that had both CTA and DSA for intracranial hemorrhage of all types. Those with primarily subarachnoid hemorrhage or recent trauma were excluded. Fifty-five patients formed the study cohort. Three reviewers independently analyzed the CTAs in a blinded protocol and classified them based on presence or absence of a secondary etiology. Results were compared with the reference standard DSA and kappa values determined for interobserver variability. RESULTS The overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy of CTA were 89%, 92%, 91%, 91% and 91%, respectively. Kappa value for interobserver agreement ranged from 0.78 to 0.89. Two of four dural arteriovenous fistulas (dAVF) were missed on CTA by all three reviewers. CONCLUSION CTA is nearly as effective as DSA at determining the cause of secondary intracerebral hemorrhage, but with a lower sensitivity for dAVFs. This supports the use of CTA as the first screening test in patients presenting with spontaneous ICH.

Interobserver Agreement of ASPECT Score Distribution for Noncontrast CT, CT Angiography, and CT Perfusion in Acute Stroke

Background and Purpose— The Alberta Stroke program early CT score (ASPECTS) is a semiquantative scale for estimating extent and distribution of early ischemic changes within the MCA territory in the acute stroke setting. Good interobserver agreement of total ASPECTS is demonstrated for noncontrast CT (NCCT) and other imaging modalities. Our purpose is to assess interobserver agreement for individual ASPECTS regions for different imaging modalities. Methods— One hundred and eighty-one consecutive patients presenting with acute stroke symptoms within 4.5 hours of onset were included. Four readers assigned total and individual ASPECTS for NCCT, CT angiography source images (CTA-SI), and CTP maps of cerebral blood volume (CTP-CBV). Interobserver agreement was assessed by measuring internal consistency and concordance of total and individual ASPECTS using Cronbach’s &agr; and intraclass correlation coefficient, respectively. Results— Total ASPECTS demonstrated very good concordance and internal consistency for all 3 modalities. Intraclass correlation coefficient and Cronbach’s &agr; were 0.834 and 0.859 for NCCT, 0.876 and 0.894 for CTA, and 0.903 and 0.911 for CTP-CBV, respectively. Performance for individual ASPECTS regions was inferior to total ASPECTS, but incremental improvement in interobserver reliability was demonstrated for NCCT, CTA-SI, and CTP-CBV, respectively. Highest concordance was shown for caudate, lentiform, and M1–M3, whereas performance for internal capsule and M4–M6 was poorer. Conclusions— CTP-CBV demonstrates the highest interobserver agreement for individual ASPECTS regions.

Delayed cochlear implantation after surgical labyrinthectomy

BACKGROUND Cochlear implantation has been used to rehabilitate profoundly deafened adults for more than 25 years. However, surgical labyrinthectomy is often considered a contraindication to cochlear implantation, especially if there is a significant delay between the two procedures. As the role of cochlear implantation continues to expand, this idea requires reconsideration. CASE REPORT A 59-year-old woman presented to our clinic after undergoing bilateral surgical labyrinthectomies for intractable Ménières disease 21 years prior. Despite the significant time delay, she underwent cochlear implantation with a good audiological outcome and improved quality of life. CONCLUSION Changes to the cochlea and vestibule following surgical labyrinthectomy include cochlear ossification and obliteration of the vestibule. These issues have been thought to limit the potential for cochlear implantation, especially when there is a significant delay between the two procedures. However, delayed cochlear implantation, even decades after labyrinthectomy, remains a viable treatment option which can benefit selected patients.

Hypofractionated Stereotactic Radiotherapy in Five Daily Fractions for Post-Operative Surgical Cavities in Brain Metastases Patients with and without Prior Whole Brain Radiation

Our purpose was to report efficacy of hypofractionated cavity stereotactic radiotherapy (HCSRT) in patients with and without prior whole brain radiotherapy (WBRT). 32 surgical cavities in 30 patients (20 patients/21 cavities had no prior WBRT and 10 patients/11 cavities had prior WBRT) were treated with image-guided linac stereotactic radiotherapy. 7 of the 10 prior WBRT patients had “resistant” local disease given prior surgery, post-operative WBRT and a re-operation, followed by salvage HCSRT. The clinical target volume was the post-surgical cavity, and a 2-mm margin applied as planning target volume. The median total dose was 30 Gy (range: 25–37.5 Gy) in 5 fractions. In the no prior and prior WBRT cohorts, the median follow-up was 9.7 months (range: 3.0–23.6) and 15.3 months (range: 2.9–39.7), the median survival was 23.6 months and 39.7 months, and the 1-year cavity local recurrence progression-free survival (LRFS) was 79 and 100%, respectively. At 18 months the LRFS dropped to 29% in the prior WBRT cohort. Grade 3 radiation necrosis occurred in 3 prior WBRT patients. We report favorable outcomes with HCSRT, and well selected patients with prior WBRT and “resistant” disease may have an extended survival favoring aggressive salvage HCSRT at a moderate risk of radiation necrosis.

Volumetric changes of the anterolateral thigh free flap following adjuvant radiotherapy in total parotidectomy reconstruction

The aim of this study was to prospectively evaluate volume change in anterolateral thigh free flaps pre‐ and postradiotherapy and to compare computed tomography (CT) volumetric analysis with intraoperative water displacement calculation.

Comparison of computed tomography angiography with digital subtraction angiography in the assessment of clipped intracranial aneurysms

Purpose: To examine whether computed tomography angiography (CTA) is comparable to digital subtraction angiography (DSA) in assessing clipped intracranial aneurysms. Materials and Methods: Retrospective collection of clipped aneurysms that had both CTA and DSA within 2 months of one another. Computed tomography angiograms were independently reviewed by 2 blinded neuroradiologists; rereviewed by one at least 4 months later. Each was classified as complete obliteration, neck remnant, or residual aneurysm. Parent vessel was classified as patent or occluded. Digital subtraction angiograms were reviewed in a similar manner by a third blinded neuroradiologist. Results: Forty-eight patients with 53 clipped aneurysms were collected. On DSA, 35 were completely obliterated, 10 neck remnants, and 8 residual aneurysms. The ability of CTA to detect residual aneurysms versus complete obliterations or neck remnants was excellent (mean sensitivity, 88%; specificity, 100%; positive predictive value [PPV], 100%; negative predictive value [NPV], 98%). The ability of CTA to detect neck remnants versus complete obliterations was poor (mean sensitivity, 20%; specificity, 99%; PPV, 83%; NPV, 81%). The CTAs were good at detecting parent vessel occlusion (mean sensitivity, 88%; specificity, 97%; PPV, 75%; NPV, 99%). Interrater and intrarater agreement was good to excellent for aneurysm and parent vessel assessment, with &kgr; values ranging from 0.6 to 1.0. Conclusions: Computed tomography angiography has high sensitivity and specificity for residual aneurysm detection and parent vessel occlusion. It is not accurate in neck remnant detection, although these were small and of uncertain clinical significance. This suggests that CTA is useful for follow-up of clipped aneurysms. However, given the potential to miss neck remnants or small residual aneurysms, it is recommended to perform initial DSA and CTA to select cases in which CTA follow-up is appropriate.

Falsely Claiming Use of NASCET Percentage Stenosis Method

We read with interest the report of Dr Anzidei and colleagues (1), which appeared in the May 2009 issue of Radiology, in which they compared steady-state contrast agent–enhanced magnetic resonance (MR) imaging with digital subtraction angiography (DSA) for the imaging of internal carotid artery (ICA) stenosis. This is an important contribution. Stenosis degrees were peripheral to this report, yet they were included. North American Symptomatic Carotid Endarterectomy Trial (NASCET) percentage stenosis methods (2–4) are referenced, with the explanation that percentage stenosis was used as a denominator beyond the bulb, where the walls are parallel, and was not The chief neuroradiology investigator (A.J.F.) for NASCET measured thousands of ICAs (2–4) in a consistent way as a balance to other inconsistent measurements (4,8–10). Yet, the so-called NASCET method for carotid stenosis calculation failed to enlist sufficient compliance. This is because many investigators choose ratio denominators from ICA locations that are too proximal, where the bulb is still tapering, contrary to the NASCET criteria to measure “where walls are parallel.” NASCET researchers never measured near occlusions, as it is fallacious and requires near occlusion interpretation before measuring. However, Dr Anzidei and colleagues ignore this in figure 1 (1). Researchers in scores of studies have also claimed to use NASCET criteria for percentage stenosis, yet the values they have produced have little relationship to NASCET. However, all of these investigators associate their findings with NASCET outcomes, with potentially many more surgeries resulting from overstated percentage stenosis. Radiologists are culpable for sending patients for surgery or stent placement on the basis of incorrect NASCET measurements and for the associated costs and risks. The ICA bulb is an anatomic aberration (2,4), which is larger than its outflow ICA. NASCET investigators adopted its method to provide the basis for a consistent measurement of percentage ICA stenosis, yet compliance with this method seems to be poor, with many authors using their own pseudo-NASCET methods. If the percentage stenosis denominator were eliminated and investigators and clinicians were to use the actual stenosis measurement in millimeters (7,13), now that it can easily be obtained, these ratio pitfalls that have been muddying things for years would be removed. References

Metastasis of follicular variant of papillary thyroid carcinoma masquerading as primary temporal bone tumour

OBJECTIVE We describe the first published case of papillary thyroid carcinoma metastatic to the temporal bone. CASE REPORT A 64-year-old woman presented with a large left temporal bone mass centred in the jugular foramen, initially thought to be a paraganglioma or schwannoma. She was simultaneously being investigated for a left-sided thyroid nodule, which was found to be unremarkable on repeated fine needle aspiration cytology. A biopsy of the temporal bone mass indicated that it was of thyroid origin. The patient underwent total thyroidectomy, which enabled a final diagnosis of follicular-variant papillary thyroid carcinoma with metastasis to the temporal bone. CONCLUSION Although biopsy is not the usual management for many types of temporal bone mass, pathological investigation is recommended if the tumour has an atypical growth rate, location, spread and/or radiological features. Metastasis of papillary thyroid carcinoma to the skull base is extremely rare, and correct diagnosis is essential in order to pursue an effective treatment plan.