Comparing Preliminary and Final Neuroradiology Reports: What Factors Determine the Differences?

BACKGROUND AND PURPOSE: Trainees' interpretations of neuroradiologic studies are finalized by faculty neuroradiologists. We aimed to identify the factors that determine the degree to which the preliminary reports are modified. MATERIALS AND METHODS: The character length of the preliminary and final reports and the percentage character change between the 2 reports were determined for neuroradiology reports composed during November 2012 to October 2013. Examination time, critical finding flag, missed critical finding flag, trainee level, faculty experience, imaging technique, and native-versus-non-native speaker status of the reader were collected. Multivariable linear regression models were used to evaluate the association between mean percentage character change and the various factors. RESULTS: Of 34,661 reports, 2322 (6.7%) were read by radiology residents year 1; 4429 (12.8%), by radiology residents year 2; 3663 (10.6%), by radiology residents year 3; 2249 (6.5%), by radiology residents year 4; and 21,998 (63.5%), by fellows. The overall mean percentage character change was 14.8% (range, 0%-701.8%; median, 6.6%). Mean percentage character change increased for a missed critical finding (+41.6%, P < .0001), critical finding flag (+1.8%, P < .001), MR imaging studies (+3.6%, P < .001), and non-native trainees (+4.2%, P = .018). Compared with radiology residents year 1, radiology residents year 2 (-5.4%, P = .002), radiology residents year 3 (-5.9%, P = .002), radiology residents year 4 (-8.2%, P < .001), and fellows (-8.7%; P < .001) had a decreased mean percentage character change. Senior faculty had a lower mean percentage character change (-6.88%, P < .001). Examination time and non-native faculty did not affect mean percentage character change. CONCLUSIONS: A missed critical finding, critical finding flag, MR imaging technique, trainee level, faculty experience level, and non-native-trainee status are associated with a higher degree of modification of a preliminary report. Understanding the factors that influence the extent of report revisions could improve the quality of report generation and trainee education.

Critical findings: timing of notification in neuroradiology.

BACKGROUND AND PURPOSE: Timely reporting of critical findings in radiology has been identified by The Joint Commission as one of the National Patient Safety Goals. Our aim was to determine the magnitude of delays between identifying a neuroradiologic critical finding and verbally notifying the caregiver in an effort to improve clinical outcomes. MATERIALS AND METHODS: We surveyed the time of critical finding discovery, attempted notification, and direct communication between neuroradiologists and caregivers for weekday, evening, overnight, and weekend shifts during an 8-week period. The data were collected by trained observers and/or trainees and included 13 neuroradiology attendings plus fellows and residents. Critical findings were based on a previously approved 17-item list. Summary and comparative t test statistics were calculated, and sources of delays were identified. RESULTS: Ninety-one critical findings were recorded. The mean time from study acquisition to critical finding discovery was 62.2 minutes, from critical finding discovery to call made 3.7 minutes, and from call made to direct communication, 5.2 minutes. The overall time from critical finding discovery to caregiver notification was within 10 minutes in 72.5% (66/91) and 15 minutes in 93.4% (85/91) of cases. There were no significant differences across shifts except for daytime versus overnight and weekend shifts, when means were 2.4, 5.6, and 8.7 minutes, respectively (P < .01). If >1 physician was called, the mean notification time increased from 3.5 to 10.1 minutes (P < .01). Sources of delays included inaccurate contact information, physician unavailability (shift change/office closed), patient transfer to a different service, or lack of responsiveness from caregivers. CONCLUSIONS: Direct communication with the responsible referring physician occurred consistently within 10-15 minutes after observation of a critical finding. These delays are less than the average interval from study acquisition to critical finding discovery (mean, 62.2 minutes).

Attitudes about medical malpractice: an American Society of Neuroradiology survey.

SUMMARY: The concern over medicolegal liability is pervasive among physicians. We sought, through an email survey to the members of the ASNR, to assess the experience with and attitudes about the medicolegal environment among neuroradiologists. Of 4357 physicians surveyed, 904 answered at least 1 of the questions in the survey; 449 of 904 (49.7%) had been sued: 180 (44.9%) had been sued once, 114 (28.4%) twice, 60 (15.0%) 3 times, and 47 (11.7%) more than 3 times. The payouts for suits were most commonly in the $50,000 to $150,000 range, except for interventional neuroradiologists, in whom the most common value was $600,000 to $1,200,000. Only 9 of 481 (1.9%) of suits returned a plaintiff verdict. Despite reported outcomes that favored physicians with respect to cases being dropped (270/481 = 56.1%), settled without a payment (11/481 = 2.3%), or a defense verdict (46/481 = 9.6), most respondents (81.1%, 647/798) believed that the medicolegal system was weighted toward plaintiffs. More than half of the neuroradiologists (55.2%, 435/787) reported being mildly to moderately concerned, and 19.1% (150/787) were very or extremely concerned about being sued.

Neuroradiology critical findings lists: survey of neuroradiology training programs.

BACKGROUND AND PURPOSE: The Joint Commission has identified timely reporting of critical results as one of the National Patient Safety Goals. We surveyed directors of neuroradiology fellowships to assess and compare critical findings lists across programs. MATERIALS AND METHODS: A 3-question survey was e-mailed to directors of neuroradiology fellowships with the following questions: 1) Do you currently have a "critical findings" list that you abide by in your neuroradiology division? 2) How is that list distributed to your residents and fellows for implementation, if at all? and 3) Was this list vetted by neurology, neurosurgery, and otolaryngology departments? Programs with CF lists were asked for a copy of the list. Summary and comparative statistics were calculated. RESULTS: Fifty-one of 89 (57.3%) programs responded. Twenty-one of 51 (41.2%) programs had CF lists. Lists were distributed during orientation, sent via Web sites and e-mails, and posted in work areas. Eleven of 21 lists were developed internally, and 5 of 21, with the input from other departments. The origin of 5 of 21 lists was unknown. Forty CF entities were seen in 20 submitted lists (mean, 9.1; range, 2-23). The most frequent entities were the following: cerebral hemorrhage (18 of 20 lists), acute stroke (15 of 20), spinal cord compression (15 of 20), brain herniation (12 of 20), and spinal fracture/instability (12 of 20). Programs with no CF lists called clinicians on the basis of "common sense" and "clinical judgment." CONCLUSIONS: Less than a half (41.2%) of directors of neuroradiology fellowships that responded have implemented CF lists. CF lists have variable length and content and are predominantly developed by radiology departments without external input.

Quality control in neuroradiology: impact of trainees on discrepancy rates.

BACKGROUND AND PURPOSE: Prior studies have found a 2%-8% clinically significant error rate in radiology practice. We compared discrepancy rates of studies interpreted by subspecialty-trained neuroradiologists working with and without trainees. MATERIALS AND METHODS: Subspecialty-trained neuroradiologists reviewed 2162 studies during 41 months. Discrepancies between the original and "second opinion" reports were scored: 1, no change; 2, clinically insignificant detection discrepancy; 3, clinically insignificant interpretation discrepancy; 4, clinically significant detection discrepancy; and 5, clinically significant interpretation discrepancy. Faculty alone versus faculty and trainee discrepancy rates were calculated. RESULTS: In 87.6% (1894/2162), there were no discrepancies with the original report. The neuroradiology division had a 1.8% (39/2162; 95% CI, 1.3%-2.5%) rate of clinically significant discrepancies. In cases reviewed solely by faculty neuroradiologists (16.2% = 350/2162 of the total), the rate of discrepancy was 1.7% (6/350). With fellows (1232/2162, 57.0% of total) and residents (580/2162, 26.8% of total), the rates of discrepancy were 1.6% (20/1232) and 2.2% (13/580), respectively. The odds of a discrepant result were 26% greater (OR = 1.26; 95% CI, 0.38-4.20) when reading with a resident and 8% less (OR = 0.92; 95% CI, 0.35-2.44) when reading with a fellow than when reading alone. CONCLUSIONS: There was a 1.8% rate of clinically significant detection or interpretation discrepancy among academic neuroradiologists. The difference in the discrepancy rates between faculty only (1.7%), fellows and faculty (1.6%), and residents and faculty (2.2%) was not statistically significant but showed a trend indicating that reading with a resident increased the odds of a discrepant result.

Addressing an unmet need in oncology patients: rehabilitation of upper aerodigestive tract function.

BACKGROUND: Laryngeal dysfunction in the oncology population is common and may detract from quality of life (QoL) due to vocal restriction and aspiration. Therapies to address this complex issue have not been explored to date. We examined the outcomes among oncology patients treated with a minimally invasive office-based surgical approach for the rehabilitation of laryngeal dysfunction. PATIENTS AND METHODS: A retrospective analysis was carried out of oncology patients referred for laryngeal dysfunction. Patients who underwent minimally invasive injection laryngoplasty (IL) were selected. Subjective outcome measures, objective voice analysis parameters, and swallowing studies were annotated. RESULTS: Sixty-one patients underwent IL for the management of laryngeal dysfunction. Lung cancer was the most common cancer diagnosis (39.3%), and 52% of patients had thoracic malignancies. All patients had a self-reported improvement in vocal function with a single injection, and 55 patients (90%) reported lasting effects at 3 months. In patients with pre- and postoperative voice analysis, phonatory function increased from 5.0 to 10.5 s, more than twofold improvement compared with baseline functioning. Seventy-one percent of patients who aspirated before injection no longer required a modified diet. There were no major complications. CONCLUSIONS: Interventions to improve the QoL in oncology patients continue to evolve. We report significant improvements in both subjective and objective measures of laryngeal function after IL for vocal fold dysfunction that are both immediate and sustained. We conclude that IL is a safe and efficacious procedure for the treatment of laryngeal dysfunction in oncology patients, resulting in palliation and improved QoL.

Evaluation of MR imaging guided steroid injection of the sacroiliac joints for the treatment of children with refractory enthesitis-related arthritis.

OBJECTIVES: To test the hypothesis that MR imaging guided triamcinolone acetonide injection into the sacroiliac joints of children with enthesitis-related arthritis is feasible, accurate and safe; and effectively reduces sacroiliac inflammation and disease progression. METHODS: A retrospective analysis of 14 children (6/14 [43%] female, 8/14 (57%) male; mean age, 13.2 years; range, 6-16 years) who received MR imaging guided sacroiliac joint injections at 0.2 Tesla or 1.5 Tesla for enthesitis-related arthritis and acute sacroilitis refractory to medical therapy was performed. 20 mg triamcinolone acetonide were injected. Assessed were intra-articular drug delivery; image quality, duration, and complications. Success of therapy was defined by change of sacroiliac inflammation. Remission time and erosions were assessed by follow-up MRI (range, 10-22 months). RESULTS: Twenty four procedures resulted in intra-articular injection. Image quality was sufficient. No complications occurred. Procedure time was 40 min. Sedation time was 22 min. Success of therapy was achieved in 11/14 (79%) children. Sacroiliac inflammation decreased significantly (-59%). Median remission time was 13.7 months. No erosions occurred. CONCLUSIONS: MR imaging guided steroid injection of the sacroiliac joints is feasible, accurate, and safe and can effectively reduce sacroiliac inflammatory activity and may therefore aid in the prevention of disease progression.

Magnetic resonance imaging-guided renal artery stent placement in a Swine model: comparison of two tracking techniques.

BACKGROUND: Magnetic resonance (MR)-guided interventions have evolved from a pure research application to a preclinical method over the last decade. Among the device-tracking techniques, susceptibility artifact-based tracking relies on the contrast between the surrounding blood and the device, and radiofrequency coil-based tracking relies on the local gradient field amplification in a resonating circuit attached to the interventional device. PURPOSE: To evaluate the feasibility and precision of susceptibility artifact-based and microcoil-based MR guidance methods for renal artery stent placement in a swine model. MATERIAL AND METHODS: MR imaging-guided renal artery stent placements were performed in six fully anesthetized pigs using a 1.5T short-bore MR scanner. Susceptibility artifact-based tracking with manual scan-plane adjustments and microcoil tracking with automatic scan-plane adjustments were used for renal artery stent placements in three pigs in each group. With both methods, near real-time steady-state free-precession (SSFP) imaging was used. Differences between the two tracking approaches on stenting time, total procedure time, and stent position were measured. RESULTS: The microcoil-based approach yielded a shorter mean procedure time (17 vs. 23 min). There was no relevant difference for the mean stenting time (12 vs. 13 min). The mean stent deviation from the aortic wall with the susceptibility approach was larger than with the microcoil approach (10 vs. 4.0 mm). CONCLUSION: For MRI-guided renal artery stent placement, the microcoil-based technique had a shorter procedure time and a higher stent placement precision than the susceptibility artifact-based approach.

CT assessment of vocal cord medialization.

BACKGROUND AND PURPOSE: Unilateral vocal cord paralysis (UVCP) occurs after iatrogenic injury or disease process and is associated with dysphonia and aspiration. Various surgical options are available for treatment of UVCP, including vocal cord medialization thyroplasty and injection laryngoplasty. These augmentative procedures improve phonation and airway protection. Our purpose was to demonstrate the CT appearance of implants used for the treatment of UVCP. METHODS: Twelve patients treated surgically for UVCP were studied with helical CT. The vocal cords were augmented by using Silastic implants (n = 7), polytetrafluoroethylene (Gore-Tex) implants (n = 2), Teflon injections (n = 2), or fat injection (n = 1). Augmented vocal cords were characterized by size, shape, and Hounsfield units (HU). Two other patients with failed medialization thyroplasty were evaluated for the position of the extruded implant relative to the paralyzed vocal cord. RESULTS: The 7 Silastic implants were triangular and hyperattenuated (293.4 +/- 90.4 HU). The 2 Gore-Tex implants were heterogeneous with lobulated medial margins and were hyperattenuating (320 and 414 HU). The injected materials demonstrated ovoid/masslike configurations: the 2 Teflon injections were hyperattenuated (107 and 429 HU), and the fat injection was hypoattenuated (-102 HU). Inferior displacement of the implant was demonstrated relative to the true vocal cord in 2 patients with failed Silastic thyroplasties. CONCLUSION: CT can distinguish various types of vocal cord augmentation. Silastic implants are recognized by their characteristic triangular configuration. The Gore-Tex implants had unique heterogeneous attenuation with lobulated medial margins. Fat and Teflon injections both appear ovoid/masslike. Teflon injection should not be mistaken for tumor.

Magnetic resonance-guided biliary drainage in a patient with malignant obstructive jaundice and thrombocytopenia.

In a patient suffering from malignant obstructive jaundice and thrombocytopenia, magnetic resonance imaging (MRI) was used to guide percutaneous transhepatic biliary drainage, to avoid blind puncture of the bile ducts using fluoroscopy. The first puncture approach was successful, and an MRI-visible guide wire and drainage catheter were inserted successfully within 35 min. The course after the intervention was uneventful, and the patient's fever and itching improved. MRI guidance facilitated optimal procedure planning and high puncture accuracy.

Segmented k-space and real-time cardiac cine MR imaging with radial trajectories.

The authors developed and evaluated two cine magnetic resonance (MR) imaging sequences with a radial rather than a rectilinear k-space coordinate frame: segmented k space and real-time true fast imaging with steady-state precession, or FISP. The two radial k-space segmentation (or view sharing) techniques, which were interleaved or continuous, were compared, and the feasibility of their application in cardiac cine MR imaging was explored in phantom and volunteer studies. Images obtained with the radial sequences were compared with those obtained with two-dimensional Fourier transform, or 2DFT, sequences currently used in cine MR imaging. Temporal resolution of 55 msec was achieved with the real-time radial sequences, which allowed acquisition of almost 19 high-quality images per second.

Inhibition of prostate carcinogenesis in TRAMP mice by oral infusion of green tea polyphenols.

Development of effective chemopreventive agents against prostate cancer (CaP) for humans requires conclusive evidence of their efficacy in animal models that closely emulates human disease. The autochthonous transgenic adenocarcinoma of the mouse prostate (TRAMP) model, which spontaneously develops metastatic CaP, is one such model that mimics progressive forms of human disease. Employing male TRAMP mice, we show that oral infusion of a polyphenolic fraction isolated from green tea (GTP) at a human achievable dose (equivalent to six cups of green tea per day) significantly inhibits CaP development and increases survival in these mice. In two separate experiments, the cumulative incidence of palpable tumors at 32 weeks of age in 20 untreated mice was 100% (20 of 20). In these mice, 95% (19 of 20), 65% (13 of 20), 40% (8 of 20), and 25% (5 of 20) of the animals exhibited distant site metastases to lymph nodes, lungs, liver, and bone, respectively. However, 0.1% GTP (wt/vol) provided as the sole source of drinking fluid to TRAMP mice from 8 to 32 weeks of age resulted in (i) significant delay in primary tumor incidence and tumor burden as assessed sequentially by MRI, (ii) significant decrease in prostate (64%) and genitourinary (GU) (72%) weight, (iii) significant inhibition in serum insulin-like growth factor-I and restoration of insulin-like growth factor binding protein-3 levels, and (iv) marked reduction in the protein expression of proliferating cell nuclear antigen (PCNA) in the prostate compared with water-fed TRAMP mice. The striking observation of this study was that GTP infusion resulted in almost complete inhibition of distant site metastases. Furthermore, GTP consumption caused significant apoptosis of CaP cells, which possibly resulted in reduced dissemination of cancer cells, thereby causing inhibition of prostate cancer development, progression, and metastasis of CaP to distant organ sites.

A multielement RF coil for MRI guidance of interventional devices.

Accurate localization of minimally invasive devices is critical to the success of interventional procedures. Device orientation and tip position are two of the most important pieces of information needed to define device location for magnetic resonance imaging (MRI)-guided interventional procedures. While a single one-element micro coil incorporated into an interventional device has proven to be effective in some applications, it can only supply tip position information. However, multiple positions on the device are necessary to also determine its orientation. For this purpose, a novel single micro coil design with three separate winding elements that provides both the device orientation and tip position is described in this study. Definition of MR scan planes, by using the device orientation and the target tissue location, permits automatic tracking of the insertion of the device. Furthermore, devices that include this coil design are permitted to bend to a limited extent. This makes the micro coil design appropriate for many flexible interventional devices. Reliable near-real-time tracking of three points on an interventional device is demonstrated on a 0.2T MRI system with modest gradient performance. Phantom and in vivo animal experiments are used to demonstrate the utility of this new coil design.

Experience with the chin tuck maneuver in postesophagectomy aspirators.

Aspiration is a common finding in the postesophagectomy barium swallow that often necessitates premature termination of the study prior to complete evaluation of the gastric conduit. More importantly, aspiration may play a significant role in the high incidence of postoperative pulmonary complications in this population. The chin tuck maneuver is a postural technique that reduces and often eliminates aspiration in swallowing-impaired patients. To evaluate the ability of the chin tuck maneuver to prevent aspiration during radiographic examination of the gastric conduit, the technique was used in 21 esophagectomy patients who aspirated during a swallowing evaluation combining the barium swallow and videofluoroscopy. Aspiration was eliminated in 81% of aspirators using the chin tuck maneuver. The results of this study demonstrate that the chin tuck maneuver is a simple technique that should be attempted in patients who aspirate postesophagectomy during radiographic imaging studies that require multiple swallows of contrast materials. Combining the barium swallow with the videofluoroscopic evaluation of swallowing provides objective documentation of both the structural integrity of the gastric conduit and swallowing function in patients after esophagectomies who are at high risk for postoperative morbidity.

The value of diffusion-weighted imaging for prediction of lasting deficit in acute stroke: an analysis of 134 patients with acute neurologic deficits.

Acute stroke is one of the three major causes of death and disability in the United States. Now that new, and possibly effective therapy is becoming available, accurate, rapid diagnosis is important to provide timely treatment, while avoiding the risk of complications from unnecessary intervention. Our objective was to test the hypothesis that use of echo-planar (EPI) diffusion-weighted imaging (DWI) is more accurate than conventional T2 weighted MRI in predicting progression to stroke in patients with acute ischemic neurologic deficits. We studied 134 patients presenting with acute neurologic deficits to a community hospital emergency room with both conventional MRI and DWI within 72 h of the onset of the acute deficit. We found DWI significantly more sensitive to permanent neurologic deficit at discharge (sensitivity 0.81) than conventional MRI (sensitivity 0.41). When available, DWI should be considered for routine use in patients being imaged for acute stroke.

Perfusion-modulated MR imaging-guided radiofrequency ablation of the kidney in a porcine model.

OBJECTIVE: This study was performed to test the hypothesis that temporary renal ischemia will result in increased thermal lesion size during radiofrequency thermal ablation in the kidney. MATERIALS AND METHODS: Twelve kidneys were treated in six pigs that were placed under general anesthesia in the MR suite, using a 0.2-T open C-shaped MR imaging system. A 4-cm-long, 14-mm-diameter balloon catheter was placed into the aorta using a transfemoral approach, and the balloon was positioned proximal to the renal arteries via guidance with MR imaging. A 2-cm exposed-tip MR-compatible 17-gauge radiofrequency electrode was placed into one kidney under MR fluoroscopy using fast imaging with steady-state free precession (FISP) sequences. Thermal ablation was performed with the electrode tip temperature maintained at 90 +/- 2 degrees C for 10 min. This procedure was repeated in the contralateral kidney. The balloon was inflated during one ablation. Postablation images were obtained, the pigs were sacrificed, and both kidneys of each animal were harvested for pathologic correlation. RESULTS: Technical success was achieved in all animals. The lesion measured 14.2 +/- 2.2 mm (mean +/- standard deviation) for the ischemic kidney versus 8.0 +/- 2.6 mm in the normally perfused kidney (p = 0.00002). No significant complications were noted. In all images, thermal lesions displayed low signal intensity with a sharp rim of high signal intensity best visualized using short tau inversion recovery (STIR) sequences with a mean accuracy of 1.3 +/- 1.2 mm when compared with pathologic findings and a mean contrast-to-noise ratio of 4.9 +/- 2.5. CONCLUSION: We accept the hypothesis that temporary renal ischemia leads to a significantly increased radiofrequency ablation lesion size. We conclude that catheter-based balloon perfusion reduction is feasible, that the procedure does not lead to major complications, and that it can be performed using MR imaging as the sole imaging modality.

MR imaging-guided radiofrequency thermal ablation in the porcine brain at 0.2 T.

The aim of this study was to test the hypotheses that (a) MR imaging-guided radiofrequency (RF) thermal ablation is safe and feasible in porcine brain using an open C-arm-shaped low-field MR system, and that (b) induced thermal lesion size can be predicted using low-field MR imaging. Magnetic resonance-guided RF ablation was performed in the cerebral frontal lobes of six pigs. An 18-G monopolar RF electrode was inserted into the porcine brain using MR image guidance and RF was then applied for 10 min. After post-procedure imaging (T2-weighted, T1-weighted before and after gadodiamide administration), the pigs were killed and the brains were used for pathologic examination. Successful RF electrode placement was accomplished in all cases without complications; total magnet time ranged from 73 to 189 min. The thermal lesion size varied from 10 to 12 mm perpendicular to the electrode track and was easily visualized on T2-weighted and enhanced T1-weighted images. Enhanced T1-weighted imaging demonstrated the highest brain-to-RF thermal lesion contrast-to-noise ratio with an average of 1.5 +/- 1.6. Enhanced T1-weighted imaging never underestimated pathologic lesion diameter with a mean difference of 2.3 +/- 1.0 mm and a radiologic/pathologic correlation of 0.69. Magnetic resonance imaging-guided RF thermal ablation is feasible and safe in the porcine brain using an open MR low-field system. Induced-thermal lesion size can best be monitored using enhanced T1-weighted images. In the future, RF ablation under low-field MR guidance may offer an alternative treatment option for primary and secondary brain tumors.

Further experience with Botox injection for tracheoesophageal speech failure.

BACKGROUND: Some patients fail to acquire tracheoesophageal (TE) speech after laryngectomy because of pharyngeal constrictor hypertonicity. Botox injection relieves hypertonicity, but there are little objective data regarding outcomes, duration of effect, and reinjection rates. METHODS: Hypertonicity was identified by means of insufflation testing and confirmed videofluoroscopically in 23 unsuccessful TE speakers. Each patient received an EMG-guided Botox injection. Additional injections were offered if the first injection failed to produce fluent speech. RESULTS: Overall, 20 of 23 patients (87%) achieved fluent TE speech production after Botox injections; 5 after additional injections. Two patients declined further intervention, and 1 failed to achieve fluent TE speech production even after 3 Botox injections. The longest sustained effect was 37 months, the shortest was 5 months for 1 patient who required reinjection of Botox to maintain her TE speech production. CONCLUSIONS: Botox injection relieves constrictor hypertonicity in selected cases of TE speech failure with little need for reinjection to maintain long-term speech success.

[Comparison of susceptibility artefacts of different radiofrequency electrodes at O.2 T. Influence of electrode positioning, pulse sequence and image reconstruction methods]. / Vergleich der Suszeptibilitätsartefakte unterschiedlicher Radiofrequenzelektroden bei 0,2 T. Einfluss von Elektrodenlegierung, Pulssequenz und Bildrekonstruktionsmethode.

PURPOSE: Interventional MRI procedure monitoring requires small but accurate susceptibility artifacts of the instruments used. In this investigation, susceptibility artifacts of different RF-electrode designs were compared using a variety of pulse sequences and k-space acquisition methods. METHODS: 4 different 18-gauge RF-electrodes (with three single electrodes made of stainless steel, copper, inconal, and a triple-clustered electrode configuration made of inconal) were placed in a 0.2 T MR-scanner perpendicular to the main magnetic field. Pulse sequences used included: TSE T2, FISP, true-FISP, PSIF, and a temperature sensitive ES-GRE sequence. In addition to the 2D Cartesian k-space trajectory with Fourier transformation (2DFT), projection reconstruction (PR) was used with the FISP, true-FISP and PSIF sequences. RESULTS: The best tip accuracy was achieved with the combination of inconal electrodes and TSE T2. The usefulness of the tested sequences was found to be: TSE T2 > PSIF > FISP/true-FISP > ES-GRE. In general 2DFT provided better or equal tip accuracy than PR. The apparent shaft width was smaller using the copper electrode compared to the inconal electrode. However, the "match shaped" tip artifact of the copper probe led to a higher error in tip accuracy. CONCLUSIONS: TSE-T2 sequences and Cartesian 2DFT acquisitions should be used for accurate tip positioning at 0.2 T. Further, artifact size of the electrode shaft prevents the use of inconal for temperature sensitive sequences. Copper electrodes can be used for these purposes, although copper is not considered to be biocompatible at present.

Initial angiographic appearance of intracranial vascular occlusions in acute stroke as a predictor of outcome of thrombolysis: initial experience.

PURPOSE: To determine whether the initial angiographic morphology and location of intracranial arterial occlusions in acute stroke are reliable predictors of success of thrombolysis. MATERIALS AND METHODS: Thirty-three intracranial occlusions were studied in 32 patients who underwent intraarterial thrombolysis with urokinase within 6 hours from clinical onset of stroke symptoms. The initial angiographic appearance of each occlusion was categorized as cutoff, tapered, meniscus, tram-track, or tandem. Following thrombolysis, outcomes were classified as complete, partial, or no recanalization. RESULTS: Complete recanalization was accomplished in 17 of the 33 lesions, partial recanalization in nine, and no effect in seven. Tram-track (n = 3) and tapered (n = 7) lesions demonstrated the highest rates of at least partial recanalization (100% and 86%, respectively), whereas cutoff lesions (n = 13) demonstrated the lowest rate (69%). Intracranial hemorrhage was associated with higher doses of urokinase. Complete recanalization success rates were 60% for M1 lesions (n = 10), 43% for M2 or A2 lesions (n = 14), and 33% for M3 lesions (n = 3). Vertebrobasilar lesion (n = 5) success rates for complete and at least partial recanalization were 80% and 100%, respectively. CONCLUSION: Relationships were found to exist between the success rate of recanalization and initial angiographic lesion location and morphology, which represent important trends; however, further studies with a larger sample size are needed.