Arnold Cheung

Results of a prospective protocol of computed tomographic angiography in place of catheter angiography as the only diagnostic and pretreatment planning study for cerebral aneurysms by a combined neurovascular team.

OBJECTIVE:At many centers, patients undergo both computed tomographic angiography (CTA) and digital subtraction angiography (DSA). This practice negates most of the advantages of CTA, and it renders the risks and disadvantages of the two techniques additive. Previous reports in the literature have assessed the sensitivity and specificity of CTA compared with DSA; however, these investigations have not analyzed the clinical implications of a protocol that replaces DSA with CTA as the only diagnostic and pretreatment planning study for patients with cerebral aneurysms. METHODS:Since late 2001/early 2002, the combined neurovascular unit of the Massachusetts General Hospital has adopted a prospective protocol of CTA in place of DSA as the only diagnostic and pretreatment planning study for patients with cerebral aneurysms (ruptured and unruptured). We report the results obtained during the 12-month period from January 2002 to January 2003. RESULTS:During the study period, 223 patients with cerebral aneurysms underwent initial diagnostic evaluation for cerebral aneurysm by the combined neurovascular team of Massachusetts General Hospital. Of the 223 patients, 109 patients had confirmed subarachnoid hemorrhage (Group A) and 114 patients did not have SAH (Group B). All of these patients were included in the prospective CTA protocol. Cerebral aneurysm treatment was initiated on the basis of CTA alone in 93 Group A patients (86%), in 89 Group B patients (78%), and in 182 patients (82%) overall. Treatment consisted of surgical clipping in 152 patients (68%), endovascular coiling in 56 patients (25%), endovascular parent artery balloon occlusion in 4 patients (2%), and external carotid artery to internal carotid artery bypass and carotid artery surgical occlusion in 2 patients (1%). Nine patients (4%) did not undergo treatment. The cerebral aneurysm detection rate by CTA was 100% for the presenting aneurysm (ruptured aneurysm in Group A or symptomatic/presenting aneurysm in Group B) in both groups. The detection rate by CTA for total cerebral aneurysms, including incidental multiple aneurysms, was 95.3% in Group A, 98.3% in Group B, and 97% overall. The overall morbidity associated with DSA (pretreatment or as intraoperative or postoperative clip evaluation) was one patient (1.3%) with a minor nonneurological complication, one patient (1.3%) with a minor neurological complication, and no patients (0%) with a major neurological complication. CONCLUSION:We have demonstrated promising results with a prospective protocol of CTA in place of DSA as the only diagnostic and pretreatment planning study for patients with ruptured and unruptured cerebral aneurysms. It seems safe and effective to make decisions regarding treatment on the basis of CTA, without performing DSA, in the majority of patients with ruptured and unruptured cerebral aneurysms.

Flat-Panel Volume CT : Fundamental Principles, Technology, and Applications

Flat-panel volume computed tomography (CT) systems have an innovative design that allows coverage of a large volume per rotation, fluoroscopic and dynamic imaging, and high spatial resolution that permits visualization of complex human anatomy such as fine temporal bone structures and trabecular bone architecture. In simple terms, flat-panel volume CT scanners can be thought of as conventional multidetector CT scanners in which the detector rows have been replaced by an area detector. The flat-panel detector has wide z-axis coverage that enables imaging of entire organs in one axial acquisition. Its fluoroscopic and angiographic capabilities are useful for intraoperative and vascular applications. Furthermore, the high-volume coverage and continuous rotation of the detector may enable depiction of dynamic processes such as coronary blood flow and whole-brain perfusion. Other applications in which flat-panel volume CT may play a role include small-animal imaging, nondestructive testing in animal survival surgeries, and tissue-engineering experiments. Such versatility has led some to predict that flat-panel volume CT will gain importance in interventional and intraoperative applications, especially in specialties such as cardiac imaging, interventional neuroradiology, orthopedics, and otolaryngology. However, the contrast resolution of flat-panel volume CT is slightly inferior to that of multidetector CT, a higher radiation dose is needed to achieve a comparable signal-to-noise ratio, and a slower scintillator results in a longer scanning time.

Distal Radius in Adolescent Girls with Anorexia Nervosa: Trabecular Structure Analysis with High-Resolution Flat-Panel Volume CT

PURPOSE To examine trabecular microarchitecture with high-resolution flat-panel volume computed tomography (CT) and bone mineral density (BMD) with dual-energy x-ray absorptiometry (DXA) in adolescent girls with anorexia nervosa (AN) and to compare these results with those in normal-weight control subjects. MATERIALS AND METHODS The study was approved by the institutional review board and complied with HIPAA guidelines. Informed consent was obtained. Twenty adolescent girls, 10 with mild AN (mean age, 15.9 years; range, 13-18 years) and 10 age- and sex-matched normal-weight control subjects (mean age, 15.9 years; range, 12-18 years) underwent flat-panel volume CT of distal radius to determine apparent trabecular bone volume fraction (BV/TV), apparent trabecular number (TbN), apparent trabecular thickness (TbTh), and apparent trabecular separation (TbSp). All subjects underwent DXA of spine, hip, and whole body to determine BMD and body composition. The means and standard deviations (SDs) of structure parameters were calculated for AN and control groups. Groups were compared (Student t test). Linear regression analysis was performed. RESULTS AN subjects compared with control subjects, respectively, showed significantly lower mean values for BV/TV (0.37% +/- 0.05 [SD] vs 0.46% +/- 0.03, P = .0002) and TbTh (0.31 mm +/- 0.03 vs 0.39 mm +/- 0.03, P < .0001) and higher mean values for TbSp (0.54 mm +/- 0.13 vs 0.44 mm +/- 0.04, P = .02). TbN was lower in AN subjects than in control subjects, but the difference was not significant (1.17 mm(-3) +/- 0.15 vs 1.22 mm(-3) +/- 0.07, P = .43). There was no significant difference in BMD between AN and control subjects. BMD parameters showed positive correlation with BV/TV and TbTh in the control group (r = 0.55-0.84, P = .05-.01) but not in AN patients. CONCLUSION Flat-panel volume CT is effective in evaluation of trabecular structure in adolescent girls with AN and demonstrates that bone structure is abnormal in these patients compared with that in normal-weight control subjects despite normal BMD. SUPPLEMENTAL MATERIAL http://radiology.rsnajnls.org/cgi/content/full/249/3/938/DC1.

Musculoskeletal applications of flat-panel volume CT

Flat-panel volume computed tomography (fpVCT) is a recent development in imaging. We discuss some of the musculoskeletal applications of a high-resolution flat-panel CT scanner. FpVCT has four main advantages over conventional multidetector computed tomography (MDCT): high-resolution imaging; volumetric coverage; dynamic imaging; omni-scanning. The overall effective dose of fpVCT is comparable to that of MDCT scanning. Although current fpVCT technology has higher spatial resolution, its contrast resolution is slightly lower than that of MDCT (5-10HU vs. 1-3HU respectively). We discuss the efficacy and potential utility of fpVCT in various applications related to musculoskeletal radiology and review some novel applications for pediatric bones, soft tissues, tumor perfusion, and imaging of tissue-engineered bone growth. We further discuss high-resolution CT and omni-scanning (combines fluoroscopic and tomographic imaging).

Outcomes for surgical and endovascular management of intracranial aneurysms using a comprehensive grading system.

OBJECTIVEA systematic approach to the consideration of various factors on outcome demands a comprehensive grading system for patients with intracranial aneurysms. We have previously identified potential patient- and lesion-specific factors that correlate strongly with outcome after treatment for intracranial aneurysms, and we have developed a comprehensive grading system based on these factors. In this study, we evaluate this grading system in a large series of aneurysm patients treated by surgery and endovascular therapy. METHODSBetween January 1998 and January 2003, ruptured and unruptured aneurysm patients were prospectively entered into a database. Based on our previous study that showed which factors correlated strongly with outcome, data were collected on patient age, aneurysm size, Hunt and Hess grade, and Fisher scale (if presenting with subarachnoid hemorrhage), and a Massachusetts General Hospital grade was then applied. The modified Glasgow Outcome Scale was used for clinical assessment at follow-up, and a binary analysis classified patients into favorable versus unfavorable outcome. Univariate and multivariate analyses for the predictor variables were performed. RESULTSOne thousand forty-nine aneurysms in 914 patients were identified. Fifty-eight percent (n = 608) of the lesions were unruptured, and 25% (n = 261) were treated endovascularly. For patients treated either surgically or endovascularly, worsening outcome was demonstrated for higher Hunt and Hess grade (surgery, P < 0.001; endovascular, P < 0.001), Fisher scale (surgery, P < 0.001; endovascular, P < 0.001) and for older patients (surgery, P < 0.001; endovascular, P = 0.004). Size of aneurysm had a significant effect on outcome after surgery (P = 0.04), but not after endovascular therapy (P = 0.3). Overall, there was a greater proportion of favorable outcomes for anterior circulation compared with posterior circulation lesions (P < 0.0001). For both the surgical and endovascular subgroups, MGH grade correlated well with clinical outcomes. CONCLUSIONThe MGH grade is a comprehensive grading system that is easily applied and that allows separation of patients with aneurysms into groups with markedly different outcomes. This information can potentially be helpful in making treatment decisions and when discussing projected outcome before surgical or endovascular intervention of both unruptured and ruptured aneurysms.

Reproducibility of trabecular structure analysis using flat-panel volume computed tomography

PurposeTo determine inter-scan, inter-reader and intra-reader variability of trabecular structure analysis using flat-panel volume computed tomography (fp-VCT) in cadaver knee specimens.MethodsFive explanted knee specimens were imaged at three different time points using fp-VCT. Four parameters that quantify trabecular bone structure of the proximal tibia were measured by two observers at two different time points. Bland–Altman analysis was used to compute the inter-scan, inter-observer and intra-observer variability.ResultsInter-scan variability was low, with a mean difference of 0% and a standard deviation less than 8.4% for each of the four parameters. The inter-observer and intra-observer variability was less than 2.8% ± 8.5%.ConclusionFp-VCT is a method for assessing trabecular structure parameters with low inter-scan, inter-reader and intra-reader variability.

Smart Stylet: The Development and Use of a Bedside External Ventricular Drain Image-Guidance System

Background: Placement accuracy of ventriculostomy catheters is reported in a wide and variable range. Development of an efficient image-guidance system may improve physician performance and patient safety. Objective: We evaluate the prototype of Smart Stylet, a new electromagnetic image-guidance system for use during bedside ventriculostomy. Methods: Accuracy of the Smart Stylet system was assessed. System operators were evaluated for their ability to successfully target the ipsilateral frontal horn in a phantom model. Results: Target registration error across 15 intracranial targets ranged from 1.3 to 4.6 mm (mean 3.1 mm). Using Smart Stylet guidance, a test operator successfully passed a ventriculostomy catheter to a shifted ipsilateral frontal horn 20/20 (100%) times from the frontal approach in a skull phantom. Without Smart Stylet guidance, the operator was successful 4/10 (40%) times from the right frontal approach and 6/10 (60%) times from the left frontal approach. In a separate experiment, resident operators were successful 2/4 (50%) times when targeting the shifted ipsilateral frontal horn with Smart Stylet guidance and 0/4 (0%) times without image guidance using a skull phantom. Conclusions: Smart Stylet may improve the ability to successfully target the ventricles during frontal ventriculostomy.