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.

MRI characteristics of healed and unhealed peripheral vertical meniscal tears.

OBJECTIVE: The objective of our study was to retrospectively compare the MRI characteristics of surgically confirmed healed and unhealed peripheral vertical meniscal tears. MATERIALS AND METHODS: The study group consisted of 64 patients with 86 peripheral vertical meniscal tears diagnosed on MRI who subsequently underwent knee surgery. The MRI examinations were retrospectively reviewed to assess the following tear characteristics: tear location relative to the meniscocapsular junction, tear width, tear length, tear extension through one or both surfaces, sequences on which tear was visualized, signal intensity of tear on T2-weighted imaging, and presence of low-signal-intensity strands bridging the tear on T2-weighted imaging. Multivariate logistic regression models were used to determine whether MRI characteristics could be used to distinguish between healed and unhealed tears at surgery. RESULTS: Tear location was the most significant characteristic (p<0.001) for distinguishing between healed and unhealed tears: 17 of 18 (94.4%) tears located at the meniscocapsular junction of the medial meniscus were healed and 15 of 68 (22.1%) tears not located at the meniscocapsular junction were healed. For tears not located at the meniscocapsular junction, MRI characteristics significantly associated with healed tears included a tear width of less than 2 mm (p=0.01), tear visualized only on intermediate-weighted imaging (p=0.01), tear showing intermediate or bright signal intensity on T2-weighted imaging (p=0.06), and low-signal-intensity strands bridging the tear on T2-weighted imaging (p<0.001). CONCLUSION: Most peripheral vertical tears at the meniscocapsular junction of the medial meniscus spontaneously heal. The MRI characteristics of tears not located at the meniscocapsular junction can help distinguish between healed and unhealed tears.

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

PURPOSE: To 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. METHODS: Five 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. RESULTS: Inter-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%. CONCLUSION: Fp-VCT is a method for assessing trabecular structure parameters with low inter-scan, inter-reader and intra-reader variability.

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.

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.

Non-invasive evaluation of the kinetics of allergic and irritant contact dermatitis.

Reflectance confocal microscopy (RCM) allows non-invasive visualization of human skin in vivo. It has been used to describe the histopathological features of acute contact dermatitis (CD). This work was designed to investigate the kinetics of both allergic and irritant CD (ACD and ICD) in vivo. Eighteen subjects with a prior diagnosis of ACD were patch tested with the specific allergen sodium lauryl sulfate as an irritant, and appropriate controls. RCM, transepidermal water loss (TEWL), and fluorescence excitation spectroscopy (FES) were performed at several time points within 2 wk after patch removal. After removal of the Finn chambers at 48 h, superficial epidermal changes, primarily involving the stratum corneum, and increased epidermal thickness were mainly present in ICD. ACD, on the other hand, showed microvesicle formation peaking at 96 h following patch removal. Both ACD and ICD showed exocytosis and similar degrees of spongiosis on RCM. TEWL and FES demonstrated a significant difference between ACD and ICD. RCM, TEWL, and FES are valuable non-invasive tools to quantitatively study the kinetics of the pathophysiology of acute CD reactions in vivo and monitor the changes at a cellular level.

Pilot study on the sensitivity and specificity of in vivo reflectance confocal microscopy in the diagnosis of allergic contact dermatitis.

The validity, reproducibility, and specificity of patch-testing in the diagnosis of allergic contact dermatitis (ACD) have repeatedly been addressed. In vivo reflectance confocal microscopy (RCM) has been used for real-time evaluation of the histopathologic features of ACD. This pilot study was designed to determine the sensitivity and specificity of RCM in diagnosing ACD in reference to patch-testing. Sixteen participants were patch tested with allergens and control substances. Clinical scoring, digital photography, and RCM evaluation were performed at 72 hours, and RCM images were subjected to blinded evaluation. RCM evaluation parameters included stratum corneum (SC) disruption, parakeratosis, stratum spinosum (SS) and stratum granulosum (SG) spongiosis, and exocytosis. Overall, there was high specificity for all RCM features, ranging from 95.8% to 100%. Sensitivity ranged from 51.9% to 96.3%. Significant parameters with high sensitivity and specificity included spongiosis and exocytosis at the level of SS. Logistic regression analysis was performed on significant variables; P values were determined by chi2 analysis. RCM is a promising noninvasive technology for the evaluation of ACD. SC changes are not helpful in the diagnosis of ACD, although the presence of SG spongiosis and SS spongiosis shows high sensitivity in diagnosing ACD. Larger sensitivity and specificity studies are needed and the identification of ACD has to be based on a defined diagnostic algorithm. A limitation of this study is the small sample size; larger sensitivity and specificity studies are needed to confirm these findings. In addition, individual allergens have to be subjected to further evaluations in order to demonstrate the applicability of our findings for other contact allergens. In that regard, RCM may be considered as an adjunctive tool, rather than a substitute, to clinical evaluation.

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.

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.

OBJECTIVE: A 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. METHODS: Between 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. RESULTS: One 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. CONCLUSION: The 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.

Paraplegia after tethered cord surgery: an uncommon combined anomaly of spinal arteriovenous fistula and sacral lipoma--case report.

OBJECTIVE AND IMPORTANCE: The coexistence of spinal arteriovenous malformation (AVM) with congenital abnormalities is relatively common. However, the association of a spinal AVM and lipoma is rare. We present an adult patient with this combined anomaly and discuss the clinical relevance of this case. CLINICAL PRESENTATION: A 42-year-old Caucasian man with progressive paraparesis initially underwent surgery for a tethered spinal cord. Postoperatively, he became paraplegic. He improved gradually over an interval of 8 months and, at that point, worsened again. Subsequent angiographic study revealed a spinal dural arteriovenous fistula located at S1-S2. Additionally, an occipital dural AVM was discovered near the transverse sinus. INTERVENTION: The spinal arteriovenous fistula was excised along with the sacral lipoma. The occipital arteriovenous fistula was embolized successfully at a later time. CONCLUSION: The patient had immediate improvement in sensory symptoms after surgery. At a 9 month follow-up examination, he had regained the ability to walk with crutches, but his bladder dysfunction persisted. Recognition of co-existing vascular anomalies, such as spinal AVMs, is important in patients with tethered cords. The mechanisms involved in this patient's worsening neurological condition after release of the tethered cord are discussed.

Neurological recovery after decompressive craniectomy for massive ischemic stroke.

INTRODUCTION: Decompressive craniectomy has demonstrated efficacy in reducing morbidity and mortality in critically ill patients with massive hemispheric cerebral infarction. However, little is known about the patterns of functional recovery that exist in patients after decompressive craniectomy, and controversy still exists as to whether craniotomy and infarct resection ("strokectomy") are appropriate alternatives to decompression alone. We therefore used functional magnetic resonance imaging (f-MRI) to assess the extent and location of functional recovery in patients after decompressive craniectomy for massive ischemic stroke. METHODS: f-MRI was obtained in three patients with massive nondominant cerebral infarction who had undergone decompressive craniectomy for severe cerebral edema 13 to 26 months previously. Brain activation was triggered by hand-gripping or foot- movement tasks. Imaging results were combined with periodic clinical follow-up to determine the extent of neurological recovery. RESULTS: Activation of the contralateral hemisphere was seen in the sensorimotor cortex, premotor, and supplementary motor areas. Lesser activation patterns were seen in equivalent regions of the infarcted hemisphere. Peri-infarct activation foci were seen in two of the three patients, but no activation occurred within the area of infarction as defined by the initial stroke seen on diffusion-weighted MRI. All three patients demonstrated some corresponding neurological improvement. CONCLUSION: After massive hemispheric cerebral infarction requiring decompressive craniectomy, patients may experience functional recovery as a result of activation in both the infarcted and contralateral hemispheres. The evidence of functional recovery in peri-infarct regions suggests that decompression alone may be preferable to strokectomy where the risk of damage to adjacent nonischemic brain may be greater.