Incidental Thyroid Nodules on CT or MRI: Discordance Between What We Report and What Receives Workup.

OBJECTIVE: The objective of this study was to determine the proportion of incidental thyroid nodules (ITNs) reported on CT or MRI that receive additional workup and the factors that influence workup. A secondary aim was to evaluate the effect of the American College of Radiology (ACR) white paper recommendations for reporting of ITNs. MATERIALS AND METHODS: We retrospectively reviewed patients with ITNs reported on CT or MRI studies over 12 months. We identified patients with ITNs that underwent workup and the factors associated with workup. The ACR white paper recommendations were retrospectively applied to estimate how their use would have changed the number of nodules reported in the impression section of radiology reports and the number of cancers diagnosed. The recommendations are based on suspicious imaging features, patient age, and nodule size. RESULTS: A total of 375 patients had ITNs reported. For 138 of these patients (37%), ITNs were reported by radiologists in the impression section of their reports; 26 patients (19%) received workup. Patients with ITNs reported in the impression section were 14 times more likely to undergo workup than were patients with ITNs reported only in the findings section of the radiology report. On multivariate analysis, the only factors associated with workup were younger patient age and larger nodule size (p ≤ 0.002). The ACR recommendations resulted in a 54% reduction in the number of ITNs reported in the impression section and one missed papillary cancer (TNM classification T1bN0M0). CONCLUSION: Only one in five patients with ITNs reported in the impression section of CT or MRI reports underwent additional workup, and this decision was influenced by younger patient age and larger nodule size. These factors are components of the ACR recommendations, which have the potential to reduce the number of reported ITNs and improve the standardization of radiology reporting.

Applying the Society of Radiologists in Ultrasound recommendations for fine-needle aspiration of thyroid nodules: effect on workup and malignancy detection.

OBJECTIVE: The Society of Radiologists in Ultrasound (SRU) recommendations on thyroid nodules are intended to "diagnose thyroid cancers that have reached clinical significance, while avoiding unnecessary tests and surgery in patients with benign nodules." The aim of our study was to determine the proportion of thyroid nodules undergoing ultrasound-guided fine-needle aspiration (FNA) that do not meet SRU recommendations. MATERIALS AND METHODS: This study is a retrospective study of 400 consecutive ultrasound-guided thyroid FNA encounters from July 2010 through June 2011. An encounter was defined as presentation to the department of radiology on a given date for FNA of one or more thyroid nodules. The criteria for performing biopsy of a nodule were determined by the referring clinicians. Nodules were categorized on the basis of sonographic findings as meeting SRU recommendations for biopsy, which we refer to as "SRU-positive," or not, which we refer to as "SRU-negative." Patients without a definitive pathology diagnosis of Bethesda class benign or malignant nodules were excluded. The characteristics of malignancies were compared for SRU-positive and SRU-negative encounters. RESULTS: The final study group consisted of 360 biopsy encounters for 350 patients and 29 malignancies (8%). Of the 360 biopsy encounters, 86 (24%) were SRU-negative encounters. Malignancy rates in SRU-positive and SRU-negative encounters were 9% (24/274) and 6% (5/86), respectively, and were not significantly different (p=0.5). Eighteen malignancies (75%) in the SRU-positive group were localized, whereas the others had nodal metastases (4/24) or distant metastases (2/24). SRU-positive encounters included medullary carcinoma, anaplastic carcinoma, and melanoma metastasis in addition to papillary carcinoma. All SRU-negative malignancies were localized papillary carcinomas. CONCLUSION: One in four thyroid biopsy encounters at our institution did not meet SRU recommendations for biopsy. The application of SRU recommendations reduces the number of benign nodules that undergo workup. Potentially missed malignancies in SRU-negative nodules are less aggressive by histologic type and stage compared with SRU-positive malignancies.

Physician self-referral: frequency of negative findings at MR imaging of the knee as a marker of appropriate utilization.

PURPOSE: To determine whether ownership of magnetic resonance (MR) imaging equipment by ordering physicians affects the likelihood of positive findings at MR imaging of the knee and to evaluate rates of knee abnormalities seen at MR imaging as a metric for comparison of utilization. MATERIALS AND METHODS: The institutional review board approved this retrospective HIPAA-compliant study and waived the need for informed consent. A retrospective review was performed of consecutive diagnostic MR images of the knee interpreted by one radiology practice between January and April 2009 for patients who had been referred by two separate physician groups serving the same geographic community: one with financial interest (FI) in the MR imaging equipment used and one with no FI (NFI) in the MR imaging equipment used. The percentage of examinations with negative results was tabulated for both groups, and the relative frequency of each abnormality subtype was calculated among the studies with positive findings in each group. To examine frequency differences among groups, χ(2) tests were used, and to examine mean differences among groups, t tests were used. RESULTS: Of 700 examinations, 205 had negative results (117 of 350 in the FI group and 88 of 350 in the NFI group, P = .016). Among the examinations with positive results, the mean total number of positive abnormality subtypes per image did not significantly differ between groups: 1.52 for the FI group and 1.53 for the NFI group (P = .96). CONCLUSION: MR images of the knee among patients referred by the FI group were significantly more likely to be negative than those among patients referred by the NFI group. Frequency of abnormality subtype and distribution among examinations with positive results suggests a highly similar distribution and severity of abnormalities between the two patient groups.

Journal Club: Shoulder MRI utilization: relationship of physician MRI equipment ownership to negative study frequency.

OBJECTIVE: The purpose of this article is to determine whether ownership of MRI equipment by ordering physicians influences the frequency of negative shoulder MRI scans. MATERIALS AND METHODS: A retrospective review was performed of 1140 consecutive shoulder MRI scans ordered by two separate referring physician groups serving the same geographic community. The first group (financially incentivized) owned the scanners used and received technical fees for their use. The second group (non-financially incentivized) did not own the scanners used and had no direct financial interest. All examinations were performed with identical protocols and were interpreted by a single radiologist group without financial interest in the imaging equipment used. The frequency of negative examinations and the number of abnormalities in each positive study was tabulated for each group. RESULTS: A total of 1140 shoulder MRI scans met inclusion criteria; 255 were negative (142 for the financially incentivized group and 113 for the non-financially incentivized group). There were 25.6% more negative scans in the financially incentivized group (p=0.047). There was no statistically significant difference in the average number of lesions per positive scan (1.67 for the financially incentivized group and 1.71 for the non-financially incentivized group; p=0.34). No statistically significant difference was found in the frequency of 19 of 20 examined lesions. CONCLUSION: Shoulder MRI examinations referred by physicians with a financial interest in the imaging equipment used were significantly more likely to be negative. Positive examinations exhibited no statistically significant difference in the number of lesions per scan or in the frequency of 19 of 20 lesion subtypes. This finding suggests a highly similar distribution and severity of disease among the two patient groups.

Physician self-referral of lumbar spine MRI with comparative analysis of negative study rates as a marker of utilization appropriateness.

OBJECTIVE: Financial interest in imaging equipment may affect the imaging referral patterns of ordering physicians. The purpose of this article is to determine whether ownership of MRI equipment by ordering physicians predicts the likelihood and prevalence of positive findings on lumbar spine MRI as a metric for comparison of utilization. MATERIALS AND METHODS: A retrospective review was performed of 500 consecutive diagnostic lumbar spine MRI examinations in one radiology practice ordered by two separate referring physician groups serving the same geographic community: one with financial interest in the MRI equipment used (financial-interest group) and one without financial interest in the MRI equipment used (no-financial-interest group). Negative examinations and total number of lesions per positive study were recorded for each group. RESULTS: Five hundred scans met inclusion criteria during the study period (250 in the financial-interest group and 250 in the no-financial-interest group). The negative scan frequency was 86% higher in the financial-interest group (p < 0.0001). Among positive scans, there was no significant difference in the average total number of positive lesions per scan (3.93 for the financial-interest group and 4.31 for the no-financial-interest group; p = 0.132). The average age of patients imaged by the financial-interest group was 49.8 years, versus 56.9 years for the no-financial-interest group (p < 0.0001). CONCLUSION: Lumbar spine MRI examinations referred by the financial-interest group were significantly more likely to be negative than those referred by the no-financial-interest group. Lesion frequency among positive scans suggests similar severity of disease between the two patient populations. Patients imaged by the financial-interest group were significantly younger than those imaged by the no-financial-interest group.

Organ-based dose current modulation and thyroid shields: techniques of radiation dose reduction for neck CT.

OBJECTIVE: The purpose of this study was to assess the difference in absorbed organ dose and image quality for MDCT neck protocols using automatic tube current modulation alone compared with organ-based dose modulation and in-plane thyroid bismuth shielding. MATERIALS AND METHODS: An anthropomorphic female phantom with metal oxide semiconductor field effect transistor (MOSFET) detectors was scanned on a 64-MDCT scanner. The protocols included a reference neck CT protocol using automatic tube current modulation and three modified protocols: organ-based dose modulation, automatic tube current modulation with thyroid shield, and organ-based dose modulation with thyroid shield. Image noise was evaluated quantitatively with the SD of the attenuation value, and subjectively by two neuroradiologists. RESULTS: Organ-based dose modulation, automatic tube current modulation with thyroid shield, and organ-based dose modulation with thyroid shield protocols reduced the thyroid dose by 28%, 33%, and 45%, respectively, compared with the use of automatic tube current modulation alone (p ≤ 0.005). Organ-based dose modulation also reduced the radiation dose to the ocular lens (33-47%) compared with the use of automatic tube current modulation (p ≤ 0.04). There was no significant difference in measured noise and subjective image quality between the protocols. CONCLUSION: Both organ-based dose modulation and thyroid shields significantly reduce the thyroid organ dose without degradation of subjective image quality compared with automatic tube current modulation. Organ-based dose modulation has the additional benefit of dose reduction to the ocular lens.

Variation in tube voltage for adult neck MDCT: effect on radiation dose and image quality.

OBJECTIVE: The purpose of this study was to assess the effect of peak kilovoltage on radiation dose and image quality in adult neck MDCT. MATERIALS AND METHODS: An anthropomorphic phantom with metal oxide semiconductor field effect transistor detectors was imaged with a 64-MDCT scanner. The reference CT protocol called for 120 kVp, and images obtained with that protocol were compared with CT images obtained with protocols entailing 80, 100, and 140 kVp. All imaging was performed with automatic tube current modulation. Organ dose and effective dose were determined for each protocol and compared with those obtained with the 120-kVp protocol. Image noise was evaluated objectively and subjectively for each protocol. RESULTS: The highest organ doses for all protocols were to the thyroid, ocular lens, skin, and mandible. The greatest reductions in organ dose were for the bone marrow of the cervical spine and mandible: 43% and 35% with the 100-kVp protocol and 63% and 53% with the 80-kVp protocol. Effective dose decreased as much as 9% with the 100-kVp protocol and 12% with the 80-kVp protocol. Use of the 140-kVp protocol was associated with an increase in organ dose as high as 64% for bone marrow in the cervical spine and a 19% increase in effective dose. Image noise increased with lower peak kilovoltage. The measured noise difference was greatest at 80 kVp, absolute increases were less than 2.5 HU. There was no difference in subjective image quality among protocols. CONCLUSION: Reducing the voltage from 120 to 80 kVp for neck CT can result in greater than 50% reduction in the absorbed organ dose to the bone marrow of the cervical spine and mandible without impairment in subjective image quality.

Correlation of cross-sectional diameter with image quality and radiation exposure in MDCT examinations of the neck.

OBJECTIVE: The purpose of this study was to identify an optimal cross-sectional neck diameter that correlates with image quality and radiation exposure in MDCT examinations of the neck performed with automatic tube current modulation. MATERIALS AND METHODS: Ninety-six adults underwent 64-MDCT of the neck with automatic tube current modulation at the same noise setting. On frontal and lateral scout images, maximal body diameters were measured in the transverse and anteroposterior planes at two levels: just below the mandible (upper neck) and at the lung apex (lower neck). Neck diameters were correlated with image quality on a subjective 4-point scale and with radiation exposure (volume CT dose index). RESULTS: As continuous variables, both anteroposterior and transverse diameters in the lower neck were associated with image quality (p ≤ 0.0012). Diameters in the upper neck were not associated with image quality. When diameters in the lower neck were categorized into small, medium, and large, image quality grades were higher for smaller patients (p < 0.001). Images of 81% of small patients (lower neck transverse diameter < 40 cm) had a high image quality grade, compared with images of 7-20% of large patients (diameter > 48 cm). Transverse diameter in the lower neck correlated best with radiation dose measured as volume CT dose index (r = 0.78). When transverse diameter in the lower neck was used to categorize patients' size, the mean volume CT dose index for small patients was 34.1 mSv and that for large patients was 63.5 mSv. CONCLUSION: Lower neck transverse diameter on the CT scout image best correlates with image quality and radiation exposure for neck MDCT examinations performed with automatic tube current modulation. Images of patients with a lower neck transverse diameter less than 40 cm are of higher quality than those of larger patients. Individualized dose reduction techniques therefore may be appropriate for smaller patients.

Multiplanar CT and MRI of collections in the retropharyngeal space: is it an abscess?

OBJECTIVE: The purpose of this article is to describe a practical imaging approach to evaluating collections in the retropharyngeal space. CONCLUSION: The differential diagnoses for fluid in the retropharyngeal space include both noninfectious and infectious processes. The multiplanar capabilities of CT and MRI are ideal for characterizing and delineating collections. In this pictorial essay, we describe the anatomy of the retropharyngeal space and offer a four-step approach to evaluating retropharyngeal collections on multiplanar imaging.

Radiation dose exposure for lumbar spine epidural steroid injections: a comparison of conventional fluoroscopy data and CT fluoroscopy techniques.

OBJECTIVE: The purpose of this article is to compare the radiation dose of conventional fluoroscopy-guided lumbar epidural steroid injections (ESIs) and CT fluoroscopy (CTF)-guided lumbar ESI using both clinical data and anthropomorphic phantoms. MATERIALS AND METHODS: We performed a retrospective review of dose parameters for 14 conventional fluoroscopy ESI procedures performed by one proceduralist and 42 CTF-guided ESIs performed by three proceduralists (14 each). By use of imaging techniques similar to those for our clinical cohorts, a commercially available anthropomorphic male phantom with metal oxide semiconductor field effect transistor detectors was scanned to obtain absorbed organ doses for conventional fluoroscopy-guided and CTF-guided ESIs. Effective dose (ED) was calculated from measured organ doses. RESULTS: The mean conventional fluoroscopy time for ESI was 37 seconds, and the mean procedural CTF time was 4.7 seconds. Calculated ED for conventional fluoroscopy was 0.85 mSv compared with 0.45 mSv for CTF. The greatest contribution to the radiation dose from CTF-guided ESI came from the planning lumbar spine CT scan, which had an ED of 2.90 mSv when z-axis ranged from L2 to S1. This resulted in a total ED for CTF-guided ESI (lumbar spine CT scan plus CTF) of 3.35 mSv. CONCLUSION: The ED for the CTF-guided ESI was almost half that of conventional fluoroscopy because of the shorter fluoroscopy time. However, the overall radiation dose for CTF-guided ESIs can be up to four times higher when a full diagnostic lumbar CT scan is performed as part of the procedure. Radiation dose reduction for CTF-guided ESI is best achieved by minimizing the dose from the preliminary planning lumbar spine CT scan.

Multiplanar sinus CT: a systematic approach to imaging before functional endoscopic sinus surgery.

OBJECTIVE: The purpose of this essay is to present a systematic approach to the use of coronal, axial, and sagittal images for CT evaluation of the sinuses before functional endoscopic sinus surgery (FESS). CONCLUSION: We present a systematic approach to the use of coronal, axial, and sagittal images in CT evaluation before FESS. Each imaging plane is valuable for displaying anatomic variants, which can predispose a patient to recurrent disease and affect the surgical approach, and critical variants, which can make surgery hazardous.

CT mucosal window settings: a novel approach to evaluating early T-stage head and neck carcinoma.

OBJECTIVE: The purpose of this study is to evaluate the CT densities of small head and neck mucosal cancers as a means of deriving a CT mucosal window display of narrower window width and higher window level to better detect and delineate head and neck carcinomas. MATERIALS AND METHODS: We retrospectively studied 19 subjects with T1-2 head and neck carcinomas. The density of tumor and adjacent normal mucosa on CT were measured. CT scans for the 19 patients with tumors and 35 subjects without mucosal tumors were anonymized and interpreted by two readers using standard soft-tissue windows and were reviewed again 1 week later with the addition of mucosal windows. RESULTS: The mean (± SD) attenuation of 17 visible tumors was 85.5 ± 18.3 Hounsfield units (HU) and that of the surrounding normal mucosa was 55.3 ± 15.2 HU (p < 0.0001). From our data, we derived guideline mucosal window settings-a window width of 120 HU and a window level of 60 HU. On blinded review, reader A detected 12 tumors with the addition of mucosal windows (sensitivity, 63%; specificity, 82%) and nine tumors on soft-tissue windows alone (sensitivity, 47%; specificity, 94%). Reader B detected nine tumors with use of mucosal windows (sensitivity, 47%; specificity, 71%) and eight tumors on soft-tissue windows alone (sensitivity, 42%; specificity, 74%). CONCLUSION: Early T-stage tumors have higher CT density than normal mucosa. Their conspicuity can be amplified using display windows with narrower window width and higher window level. The potential clinical applications are for the improved detection of unknown primary tumors and delineation of a known mucosal tumor.

Acute stroke imaging research roadmap.

The recent "Advanced Neuroimaging for Acute Stroke Treatment" meeting on September 7 and 8, 2007 in Washington DC, brought together stroke neurologists, neuroradiologists, emergency physicians, neuroimaging research scientists, members of the National Institute of Neurological Disorders and Stroke (NINDS), the National Institute of Biomedical Imaging and Bioengineering (NIBIB), industry representatives, and members of the US Food and Drug Administration (FDA) to discuss the role of advanced neuroimaging in acute stroke treatment. The goals of the meeting were to assess state-of-the-art practice in terms of acute stroke imaging research and to propose specific recommendations regarding: (1) the standardization of perfusion and penumbral imaging techniques, (2) the validation of the accuracy and clinical utility of imaging markers of the ischemic penumbra, (3) the validation of imaging biomarkers relevant to clinical outcomes, and (4) the creation of a central repository to achieve these goals. The present article summarizes these recommendations and examines practical steps to achieve them.

Extrapulmonary Findings and Malignancies in Participants Screened With Chest CT in the National Lung Screening Trial.

PURPOSE: The aim of this study was to measure the prevalence of clinically significant extrapulmonary findings on chest CT for lung cancer screening in the National Lung Screening Trial (NLST). METHODS: Prospectively acquired data on 17,309 participants who underwent low-dose screening chest CT from August 2002 through September 2007 during the NLST were retrospectively analyzed for extrapulmonary findings. NLST radiologist readers coded such findings as "minor" or "potentially significant." On the basis of review of recorded text descriptions, extrapulmonary findings were assigned to five organ groupings (cardiovascular, thyroid, adrenal, renal, and hepatobiliary). Extrapulmonary malignancies diagnosed during screening were also identified from medical and vital status records in the same population. The prevalence rates of organ-specific findings and newly diagnosed extrapulmonary malignancies were calculated. Exemption from human subjects research review was obtained. RESULTS: Extrapulmonary findings were noted in 58.7% of CT-screened participants, and 19.6% had findings coded as potentially significant. The prevalence of potentially significant abnormalities was highest for cardiovascular findings (8.5%), followed by renal (2.4%), hepatobiliary (2.1%), adrenal (1.2%), and thyroid (0.6%) findings. Sixty-seven of 17,309 participants (0.39%) had primary extrathoracic cancers diagnosed during screening. The prevalence of cancers among screened participants was 0.26% (n = 45) for kidney, 0.08% (n = 14) for thyroid, and 0.05% (n = 8) for liver cancers. CONCLUSIONS: One in five patients screened with CT for lung cancer will have extrapulmonary findings potentially requiring further evaluation. Indiscriminate workups of incidental extrapulmonary findings could place a significant burden on the health care system with little benefit because extrapulmonary malignancies diagnosed during screening are uncommon. Radiologists reporting screening CT should be familiar with existing recommendations for incidental findings from the ACR white papers.

Parathyroid 4D CT and Scintigraphy: What Factors Contribute to Missed Parathyroid Lesions?

OBJECTIVE: To determine the prevalence of missed lesions for parathyroid 4-dimensional computed tomography (4D CT) and scintigraphy and to describe the factors leading to missed lesions for both modalities. STUDY DESIGN: Case series with chart review. SETTING: Single center, hospital based. SUBJECTS AND METHODS: Forty patients undergoing 4D CT and scintigraphy before parathyroidectomy between July 2009 and October 2013 were included. Radiology reports and imaging were reviewed and correlated with operative notes to identify cases with missed lesions and the reasons for those misses. All lesions were then classified according to the following factors: multigland disease, lesion size, patient body weight, and multinodular goiter. RESULTS: Of the 40 patients, 6 had multigland disease, resulting in 51 lesions; 12 and 29 lesions were missed on 4D CT and scintigraphy, respectively. The sensitivity for detection of all lesions was 76% for 4D CT and 43% for scintigraphy. Sensitivities for single-gland disease were 88% for 4D CT and 50% for scintigraphy. Sensitivities for multigland disease were 53% for 4D CT and 24% for scintigraphy. Rates of multigland disease in patients with missed lesions were 75% on 4D CT and 48% on scintigraphy, as compared with patients with detected lesions, 23% and 18%, respectively (P ≤ .04). Mean weight of lesions missed on 4D CT was 0.3 and 0.6 g in detected lesions (P = .15). Mean weight of lesions missed on scintigraphy was 0.4 and 0.8 g in detected lesions (P = .03). CONCLUSION: 4D CT has higher sensitivity than scintigraphy. Missed lesions are more likely to occur with multigland disease for both modalities and in smaller lesions for scintigraphy.

Comparative overview of brain perfusion imaging techniques.

BACKGROUND AND PURPOSE: Numerous imaging techniques have been developed and applied to evaluate brain hemodynamics. Among these are positron emission tomography, single photon emission computed tomography, Xenon-enhanced computed tomography, dynamic perfusion computed tomography, MRI dynamic susceptibility contrast, arterial spin labeling, and Doppler ultrasound. These techniques give similar information about brain hemodynamics in the form of parameters such as cerebral blood flow or cerebral blood volume. All of them are used to characterize the same types of pathological conditions. However, each technique has its own advantages and drawbacks. SUMMARY OF REVIEW: This article addresses the main imaging techniques dedicated to brain hemodynamics. It represents a comparative overview established by consensus among specialists of the various techniques. CONCLUSIONS: For clinicians, this article should offer a clearer picture of the pros and cons of currently available brain perfusion imaging techniques and assist them in choosing the proper method for every specific clinical setting.

Brain morphometry, T2-weighted hyperintensities, and IQ in children with neurofibromatosis type 1.

BACKGROUND: Larger gray matter (GM) volume in healthy children is correlated with higher IQ. Children with neurofibromatosis type 1 (NF1) have larger brains, their magnetic resonance images frequently show T2-weighted hyperintensities, and their IQs are lower. OBJECTIVES: To confirm the hypotheses that (1) children with NF1 have larger GM and white matter volumes, (2) the greatest volume differences are in the frontal and parietal regions and in children with NF1 with hyperintensities, and (3) GM volume is inversely related to IQ in children with NF1. DESIGN: Wechsler Intelligence Scale for Children-Third Edition IQ testing and measurement of cerebral volumes and hyperintensities in brain magnetic resonance images were performed on 36 children with NF1 and on 36 matched relatives who served as control subjects. RESULTS: Gray matter and white matter volumes were significantly larger in children with NF1. The greatest difference was observed in cerebral white matter volume, predominantly in the frontal lobes, whereas the greatest difference in GM volume was in the temporal, parietal, and occipital regions. In controls, IQ was significantly related to GM volume, but in children with NF1, IQ was not inversely associated with GM volume, although IQs of children with NF1 were significantly lower. CONCLUSIONS: Children with NF1 do not have the normal relationship between GM volume and IQ. Larger GM volume in the posterior brain regions and larger white matter volumes in the frontal brain regions contribute to the larger brain volume in children with NF1.

Contrast-enhanced magnetic resonance angiography of carotid arteries: utility in routine clinical practice.

BACKGROUND AND PURPOSE: Contrast-enhanced magnetic resonance angiography (CEMRA) is among the newer noninvasive tests used for the evaluation of patients with carotid artery disease. Evidence supporting its utility in routine clinical practice is lacking. METHODS: The results of CEMRA were compared with those of catheter angiography in 50 consecutive patients being evaluated for carotid endarterectomy (CEA) at a community hospital. Using indications for CEA based on published guidelines, we determined the rate of misclassification for surgery, sensitivity, specificity, and positive and negative predictive values. In addition, the interrater agreement (kappa score) of CEMRA was compared with that of catheter angiography in the studied population and with interpretations provided by 2 blinded radiologists. RESULTS: Compared with catheter angiography, 24% (95% CI, 12% to 36%) of patients would have been misclassified for CEA on the basis of CEMRA results alone. CEMRA was associated with sensitivity of 92%, specificity of 62%, positive predictive value of 78%, and negative predictive value of 89%. When both CEMRA and duplex Doppler ultrasound were performed and the results were concordant, the misclassification rate decreased to 17% (95% CI, 2% to 32%). kappa scores were similar for CEMRA and catheter angiography (0.72 and 0.75, respectively). CONCLUSIONS: CEMRA was found to be highly sensitive for detection of surgically amenable carotid stenosis. kappa scores for the interpretation of CEMRA and catheter angiography were similar. However, clinicians should be cautious when using CEMRA alone for surgical decision making in CEA candidates because a significant number of patients may be misclassified. The rate of misclassification is reduced when the results of CEMRA and duplex Doppler ultrasound are concordant.

Subcutaneous administration of nimodipine improves bioavailability in rabbits.

We compared subcutaneous and oral methods of nimodipine administration to determine a method of nimodipine administration that maintained serum levels at or above the optimal therapeutic concentration (7 ng/ml). Plasma concentrations of nimodipine were measured in New Zealand White rabbits (2.6-3.9 kg). First, peak plasma concentration (C(max)), time to reach peak plasma concentration (T(max)), and area under the curve (AUC) parameters were calculated and compared between animals receiving oral or subcutaneous nimodipine (5-15 mg/kg). Next, plasma concentrations were measured 24 h after subcutaneous administration of 2.5 mg/kg of nimodipine in healthy animals and animals with experimentally induced SAH. C(max), T(max) and AUC parameters were significantly greater for subcutaneous compared to oral nimodipine administration, irrespective of dose. Mean nimodipine concentrations at 24 h were >7 ng/ml in both healthy animals (12.9 +/- 10.0 ng/ml) and in animals with SAH (11.8 +/- 4.6 ng/ml) that received 2.5 mg/kg of subcutaneous nimodipine. In this model, the subcutaneous method of nimodipine administration consistently maintains plasma levels at or above the optimal therapeutic concentration, whereas oral administration fails to do so.

CT perfusion parameter values in regions of diffusion abnormalities.

BACKGROUND AND PURPOSE: Dynamic CT perfusion imaging is a rapid and widely available method for assessing cerebral hemodynamics in the setting of ischemia. Nevertheless, little is known about perfusion parameters within regions of diffusion abnormality. Since MR diffusion-weighted (DW) imaging is widely considered the most sensitive and specific technique to examine the ischemic core, new knowledge about CT perfusion findings in areas of abnormal diffusion would likely provide valuable information. The purpose of our study was to measure the CT-derived perfusion values within acute ischemic lesions characterized by 1) increased signal intensity on DW images and 2) decreased apparent diffusion coefficient (ADC) and compare these values with those measured in contralateral, normal brain tissue. METHODS: Analysis was performed in 10 patients with acute middle cerebral artery territory stroke of symptom onset less than 8 hours before imaging who had undergone both CT perfusion and DW imaging within 2 hours. After registration of CT perfusion and DW images, measurements were made on a pixel-by-pixel basis in regions of abnormal hyperintensity on DW images and in areas of decreased ADC. RESULTS: Significant decreases in cerebral blood flow and cerebral blood volume with elevated mean transit times were observed in regions of infarct as defined by increased signal intensity on DW images and decreased ADC. Comparison of perfusion parameters in regions of core infarct differed significantly from those measured in contralateral normal brain. CONCLUSION: CT perfusion findings of decreased cerebral blood flow, mean transit time, and cerebrovascular volume correlate with areas of abnormal hyperintensity on DW images and regions of decreased ADC. These findings provide important information about perfusion changes in acute ischemia in areas of diffusion abnormality.