Evaluation of 2 Novel Ratio-Based Metrics for Lumbar Spinal Stenosis.

BACKGROUND AND PURPOSE: Quantitative metrics of the dural sac such as the cross-sectional area are commonly used to evaluate central canal stenosis. The aim of this study was to analyze 2 new metrics to measure spinal stenosis on the basis of the ratio between the dural sac and disc cross-sectional areas (DDRCA) and the dural sac and disc anterior-posterior diameters (DDRDIA) and compare them with established quantitative metrics of the dural sac. MATERIALS AND METHODS: T2-weighted axial MR images (n = 260 patients) were retrospectively evaluated, graded for central canal stenosis as normal (no stenosis), mild, moderate, or severe from L1/L2 through L5/S1 with 1 grade per spinal level and annotated to measure the DDRCA and DDRDIA. Thresholds were obtained using a decision tree classifier on a subset of patients (n = 130) and evaluated on the remaining patients (n = 130) for accuracy and consistency across demographics, anatomic variation, and clinical outcomes. RESULTS: DDRCA and DDRDIA had areas under the receiver operating characteristic curve of 98.6 (97.4-99.3) and 98.0 (96.7-98.9) compared with dural sac cross-sectional area at 96.5 (95.0-97.7) for binary classification. DDRDIA and DDRCA had κ scores of 0.75 (0.71-0.79) and 0.80 (0.75-0.83) compared with dural sac cross-sectional area at 0.62 (0.57-0.66) for multigrade classification. No significant differences (P > .1) in the area under the receiver operating characteristic curve were observed for the DDRDIA across variations in the body mass index. The DDRDIA also had the highest area under the receiver operating characteristic curve among symptomatic patients (visual analog scale ≥ 7) or patients who underwent surgery. CONCLUSIONS: Ratio-based metrics (DDRDIA and DDRCA) are accurate and robust to anatomic and demographic variability compared with quantitative metrics of the dural sac and better correlated with symptomatology and surgical outcomes.

Reduced Jet Velocity in Venous Flow after CSF Drainage: Assessing Hemodynamic Causes of Pulsatile Tinnitus.

BACKGROUND AND PURPOSE: Idiopathic intracranial hypertension is commonly associated with transverse sinus stenosis, a venous cause of pulsatile tinnitus. In patients with idiopathic intracranial hypertension, CSF drainage via lumbar puncture decreases intracranial pressure, which relieves the stenosis, and may provide at least temporary cessation of pulsatile tinnitus. The objective of this study was to evaluate changes in venous blood flow caused by lowered intracranial pressure in patients with pulsatile tinnitus to help identify the cause of pulsatile tinnitus. MATERIALS AND METHODS: Ten patients with suspected transverse sinus stenosis as a venous etiology for pulsatile tinnitus symptoms underwent MR imaging before and after lumbar puncture in the same session. The protocol included flow assessment and rating of pulsatile tinnitus intensity before and after lumbar puncture and MR venography before lumbar puncture. Post-lumbar puncture MR venography was performed in 1 subject. RESULTS: There was a lumbar puncture-induced reduction in venous peak velocity that correlated with the opening pressure (r = -0.72, P = .019) without a concomitant reduction in flow rate. Patients with flow jets had their peak velocity reduced by 0.30 ± 0.18 m/s (P = .002), correlating with a reduction in CSF pressure (r = 0.82, P = .024) and the reduction in subjectively scored pulsatile tinnitus intensity (r = 0.78, P = .023). The post-lumbar puncture MR venography demonstrated alleviation of the stenosis. CONCLUSIONS: Our results show a lumbar puncture-induced reduction in venous peak velocity without a concomitant reduction in flow rate. We hypothesize that the reduction is caused by the expansion of the stenosis after lumbar puncture. Our results further show a correlation between the peak velocity and pulsatile tinnitus intensity, suggesting the flow jet to be instrumental in the development of sound.

Long-Term Effectiveness of Direct CT-Guided Aspiration and Fenestration of Symptomatic Lumbar Facet Synovial Cysts.

BACKGROUND AND PURPOSE: Lumbar facet synovial cysts are commonly seen in facet degenerative arthropathy and may be symptomatic when narrowing the spinal canal or compressing nerve roots. The purpose of this study was to analyze the safety, effectiveness, and long-term outcomes of direct CT-guided lumbar facet synovial cyst aspiration and fenestration for symptom relief and for obviating an operation. MATERIALS AND METHODS: We retrospectively reviewed the medical records and imaging studies of 64 consecutive patients between 2006 and 2016 who underwent 85 CT-guided lumbar facet synovial cyst fenestration procedures in our department. We recorded patient demographics, lumbar facet synovial cyst imaging characteristics, presenting symptoms, change in symptoms after the procedure, and whether they underwent a subsequent operation. We also assessed long-term outcomes from the medical records and via follow-up telephone surveys with patients. RESULTS: Direct CT-guided lumbar facet synovial cyst puncture was technically successful in 98% of procedures. At first postprocedural follow-up, 86% of patients had a complete or partial symptomatic response. During a mean follow-up of 49 months, 56% of patients had partial or complete long-term relief without the need for an operation; 44% of patients underwent an operation. Patients with calcified, thick-rimmed, or low T2 signal intensity cysts were less likely to respond to the procedure and more likely to need an operation. CONCLUSIONS: CT-guided direct lumbar facet synovial cyst aspiration and fenestration procedures are safe, effective, and minimally invasive for symptomatic treatment of lumbar synovial facet cysts. This procedure obviates an operation in a substantial number of patients, even at long-term follow-up, and should be considered before surgical intervention.

Differential risk reclassification improvement by exercise testing and myocardial perfusion imaging in patients with suspected and known coronary artery disease.

OBJECTIVE: The objective of this study is to compare the incremental prognostic and net risk reclassification value of exercise testing alone vs exercise myocardial perfusion imaging (MPI) for estimating the risk of death in patients with suspected and known coronary artery disease (CAD). METHODS: 6702 patients with suspected CAD and 2008 with known CAD had treadmill exercise MPI and were followed for 2.5 ± 0.9 years for the occurrence of all-cause death. The estimation of risk of death and net reclassification improvement (NRI) were examined in three models. Model 1: clinical variables; Model 2: model 1+Duke Treadmill Score; and Model 3: model 2+ MPI variables. Risk estimates were categorized as <1%, 1-3%, and >3% risk of death per year. RESULTS: In patients with suspected CAD, the global Chi-square for predicting risk of death increased significantly for Model 2 compared to Model 1 (74.78 vs 63.86 to (P = .001). However, adding MPI variables in Model 3 did not further improve predictive value (Chi-square 79.38, P = .10). In patients with suspected CAD risk, reclassification improved significantly in Model 2 over Model 1 (NRI = 0.12, 95% CI 0.02 to 0.22, P = .019), but not in Model 3 (NRI = 0.0009, 95% CI -0.072 to 0.070; P = .98). In contrast, in patients with known CAD Model 2 did not yield significant improvements for predicting risk and risk reclassification compared to Model 1. However, global Chi-square of Model 3 was significantly higher than that of Model 2 (30.03 vs 6.56, P < .0001) with associated significant reclassification improvement (NRI = 0.26 95% CI 0.067 to 0.46. P = .0084). CONCLUSION: Risk reclassification by diagnostic testing is importantly influenced by baseline characteristics of patient cohorts. In patients with suspected CAD, NRI is predominately achieved by exercise variables, whereas in patients with known CAD, greatest NRI is obtained by MPI variables.

Diffusivity measurements differentiate benign from malignant lesions in patients with peripheral neuropathy or plexopathy.

BACKGROUND AND PURPOSE: Peripheral nerve disorders caused by benign and malignant primary nerve sheath tumors, infiltration or compression of nerves by metastatic disease, and postradiation neuritis demonstrate overlapping features on conventional MR imaging but require vastly different therapeutic approaches. We characterize and compare diffusivities of peripheral nerve lesions in patients undergoing MR neurography for peripheral neuropathy or brachial or lumbosacral plexopathy. MATERIALS AND METHODS: Twenty-three patients, referred for MR neurography at our institution between 2003 and 2009 for a peripheral mononeuropathy or brachial or lumbosacral plexopathy and whose examinations included DWI, received a definitive diagnosis, based on biopsy results or clinical and imaging follow-up, for a masslike or infiltrative peripheral nerve or plexus lesion suspicious for tumor. Mean ADC values were determined within each lesion and compared across 3 groups (benign lesions, malignant lesions, and postradiation changes). RESULTS: Both ANOVA and Kruskal-Wallis tests demonstrated a statistically significant difference in ADC values across the 3 groups (P = .000023, P = .00056, respectively). Post hoc pair-wise comparisons showed that the ADC within malignant tumors differed significantly from that within benign tumors and postradiation changes. ADC within benign tumors and postradiation changes did not differ significantly from each other. CONCLUSIONS: DWI may be highly effective for the differentiation of benign from malignant peripheral nerve masslike or infiltrative lesions.

Controlled hypothermia in post-resuscitation management: what is so cool about it?

Survivors of successful resuscitated cardiac arrest have a high incidence of severe neurological deficits. The pathophysiology of cerebral injury is thought to be multifactorial, and therapeutic mild hypothermia is one of the strategies that have been shown to minimise this complication. In this article, we outline the theoretical basis for this strategy as well as the clinical evidence to support current practice guidelines advocating its use. We also review the technical aspects of implementing hypothermia after resuscitation as well as the potential side effects. Finally, unresolved issues are discussed as we outline the ongoing prospective clinical trial underway in Singapore in order to evaluate its safety and efficacy in our local population. We advocate further research into this topic, as it has great potential to improve the outcomes of comatose resuscitated patients of cardiac arrest.

Reducing patient radiation dose during CT-guided procedures: demonstration in spinal injections for pain.

BACKGROUND AND PURPOSE: CT guidance may improve precision for diagnostic and therapeutic spinal injections, but it can increase patient radiation dose. This study examined the impact of reducing tube current on patient radiation exposure and the technical success for these procedures, by using axial acquisitions for short scan lengths and eliminating nonessential imaging. MATERIALS AND METHODS: Our institutional review board approved retrospective analysis of records from 100 consecutive outpatients undergoing spinal injections for pain before and after the CT protocol modification to reduce radiation dose. Data collected included patient age and sex, response to injection, number of sites and spinal levels treated, injection type, performing physician, CT acquisition method, number of imaging series, tube current, scan length, and DLP. RESULTS: Image contrast was reduced with the low-dose protocol, but this did not affect technical success or immediate pain relief. Mean DLP for all procedures decreased from 1458 ± 1022 to 199 ± 101 mGy · cm (P < .001). The range of radiologist-dependent DLP per procedure also was reduced significantly with the modified protocol. Selective nerve root blocks, lumbar injections, multiple injection sites, and the lack of prior imaging were each associated with a slightly higher DLP (<50 mGy · cm). CONCLUSIONS: Radiation to patients undergoing CT-guided spinal injections can be decreased significantly without affecting outcome by reducing tube current, using axial acquisitions for short scan lengths, and eliminating nonessential imaging guidance. These measures also decrease variability in radiation doses between different practitioners and should be useful for other CT-guided procedures in radiology.

Reduced field-of-view diffusion imaging of the human spinal cord: comparison with conventional single-shot echo-planar imaging.

BACKGROUND AND PURPOSE: DWI of the spinal cord is challenging because of its small size and artifacts associated with the most commonly used clinical imaging method, SS-EPI. We evaluated the performance of rFOV spinal cord DWI and compared it with the routine fFOV SS-EPI in a clinical population. MATERIALS AND METHODS: Thirty-six clinical patients underwent 1.5T MR imaging examination that included rFOV SS-EPI DWI of the cervical spinal cord as well as 2 comparison diffusion sequences: fFOV SS-EPI DWI normalized for either image readout time (low-resolution fFOV) or spatial resolution (high-resolution fFOV). ADC maps were created and compared between the methods by using single-factor analysis of variance. Two neuroradiologists blinded to sequence type rated the 3 DWI methods, based on susceptibility artifacts, perceived spatial resolution, signal intensity-to-noise ratio, anatomic detail, and clinical utility. RESULTS: ADC values for the rFOV and both fFOV sequences were not statistically different (rFOV: 1.01 ± 0.18 × 10(-3) mm(2)/s; low-resolution fFOV: 1.12 ± 0.22 × 10(-3) mm(2)/s; high-resolution fFOV: 1.10 ± 0.21 × 10(-3) mm(2)/s; F = 2.747, P > .05). The neuroradiologist reviewers rated the rFOV diffusion images superior in terms of all assessed measures (P < 0.0001). Particular improvements were noted in patients with metal hardware, degenerative disease, or both. CONCLUSIONS: rFOV DWI of the spinal cord overcomes many of the problems associated with conventional fFOV SS-EPI and is feasible in a clinical population. From a clinical standpoint, images were deemed superior to those created by using standard fFOV methods.

Focused ultrasound and microbubbles for enhanced extravasation.

The permeability of blood vessels for albumin can be altered by using ultrasound and polymer or lipid-shelled microbubbles. The region in which the microbubbles were destroyed with focused ultrasound was quantified in gel phantoms as a function of pressure, number of cycles and type of microbubble. At 2MPa the destruction took place in a fairly wide area for a lipid-shelled agent, while for polymer-shelled agents at this setting, distinct destruction spots with a radius of only 1mm were obtained. When microbubbles with a thicker shell were used, the pressure above which the bubbles were destroyed shifts to higher values. In vivo both lipid and polymer microbubbles increased the extravasation of the albumin binding dye Evans Blue, especially in muscle leading to about 6-8% of the injected dose to extravasate per gram muscle tissue 30 min after start of the treatment, while no Evans Blue could be detected in muscle in the absence of microbubbles. Variation in the time between ultrasound treatment and Evans Blue injection, demonstrated that the time window for promoting extravasation is at least an hour at the settings used. In MC38 tumors, extravasation already occurred without ultrasound and only a trend towards enhancement with about a factor of 2 could be established with a maximum percentage injected dose per gram of 3%. Ultrasound mediated microbubble destruction especially enhances the extravasation in the highly vascularized outer part of the MC38 tumor and adjacent muscle and would, therefore, be most useful for release of, for instance, anti-angiogenic drugs.

Drosophila CAPS is an essential gene that regulates dense-core vesicle release and synaptic vesicle fusion.

Calcium-activated protein for secretion (CAPS) is proposed to play an essential role in Ca2+-regulated dense-core vesicle exocytosis in vertebrate neuroendocrine cells. Here we report the cloning, mutation, and characterization of the Drosophila ortholog (dCAPS). Null dCAPS mutants display locomotory deficits and complete embryonic lethality. The mutant NMJ reveals a 50% loss in evoked glutamatergic transmission, and an accumulation of synaptic vesicles at active zones. Importantly, dCAPS mutants display a highly specific 3-fold accumulation of dense-core vesicles in synaptic terminals, which was not observed in mutants that completely arrest synaptic vesicle exocytosis. Targeted transgenic CAPS expression in identified motoneurons fails to rescue dCAPS neurotransmission defects, demonstrating a cell nonautonomous role in synaptic vesicle fusion. We conclude that dCAPS is required for dense-core vesicle release and that a dCAPS-dependent mechanism modulates synaptic vesicle release at glutamatergic synapses.

Predicting the acoustic response of a microbubble population for contrast imaging in medical ultrasound.

Although the behavior of a bubble in an acoustic field has been studied extensively, few theoretical treatments to date have been applied to simulate the acoustic response of a real population of variably sized microbubbles in a finite-width sound beam. In this paper, we present a modified Trilling equation for single bubble dynamics that has been solved numerically for different conditions. Radiated waveforms from a large number of such bubbles are combined, reflecting their size distribution and location and the shape of a real acoustic beam. The resulting time-domain pressure waveforms can be compared with those obtained experimentally. The dependence of second-harmonic radiation on incident focal amplitude at different frequencies is presented. This model is particularly suited to the study of interaction between a medical ultrasound beam and microbubble contrast agents in aqueous media.

Growth of Qinghai Tibetans living at three different high altitudes.

This study compares the stature, weight, skinfolds, upper arm muscle area, and chest dimensions of Tibetan children, adolescents, and young adults who were born and raised, or who had lived from infancy, at 3,200 m, 3,800 m, and 4,300 m in Qinghai Province, People's Republic of China. While the individuals measured in Qinghai are among the tallest and heaviest Tibetans reported in the literature, they are nevertheless smaller and lighter than well-off children living at low altitude. The pattern of size variation among Tibetan males and females measured at the three high altitudes, along with evidence of a secular trend at 4,300 m, suggests that nutrition may significantly effect growth at high altitude. Only minor differences in thorax dimensions exist between Tibetan males and females measured at 3,200 m and 3,800 m. However, Tibetan males at 4,300 m possess slightly narrower and deeper chests (during and after adolescence) than males at 3,200 m and 3,800 m. Since individuals from 3,800 m and 4,300 m belong to the same local populations, this characteristic is unlikely to be genetically determined. However, it may be related to differences in the degree of hypoxia or to the influences of other environmental conditions.

Pediatric Chiari I malformations: do clinical and radiologic features correlate?

BACKGROUND: Although Chiari I malformation is increasingly recognized in children, little is known about its clinical presentation in this age group. OBJECTIVE: To evaluate the relationship between clinical and MRI features of pediatric Chiari I malformations. METHODS: We performed a chart review and MRI analysis of 49 children with Chiari I malformation. The degree of tonsillar ectopia was compared with age at onset, presence of syringomyelia, and a neurologic severity score as follows: asymptomatic = 0, symptomatic with normal neurologic examination = 1, and symptomatic with abnormal examination = 2. RESULTS: Age at onset of symptoms ranged from 10 months to 14 years. Fifty-seven percent of patients were asymptomatic. Headache and neck pain were the most frequent complaints. Syringomyelia was detected in 14% of patients and skull base abnormalities in 50%. The magnitude of tonsillar ectopia (5 to 23 mm) correlated with severity score (p = 0.04) but not with other clinical measures. CONCLUSIONS: The clinical symptoms of Chiari I malformations in children are nearly identical to those seen in adults. Children with greater amounts of tonsillar ectopia on MRI are more likely to be symptomatic.

Pulse inversion Doppler: a new method for detecting nonlinear echoes from microbubble contrast agents.

A novel technique for the selective detection of ultrasound contrast agents, called pulse inversion Doppler, has been developed. In this technique, a conventional Doppler or color Doppler pulse sequence is modified by inverting every second transmit pulse. Either conventional or harmonic Doppler processing is then performed on the received echoes. In the resulting Doppler spectra, Doppler shifts from linear and nonlinear scattering are separated into two distinct regions that can be analyzed separately or combined to estimate the ratio of nonlinear to linear scattering from a region of tissue. The maximum Doppler shift that can be detected is 1/2 the normal Nyquist limit. This has the advantage over conventional harmonic Doppler that it can function over the entire bandwidth of the echo signal, thus achieving superior spatial resolution in the Doppler image. In vitro measurements comparing flowing agent and cellulose particles suggest that pulse inversion Doppler can provide 3 to 10 dB more agent to tissue contrast than harmonic imaging with similar pulses. Similar measurements suggest that broadband pulse inversion Doppler can provide up to 16 dB more contrast than broadband conventional Doppler. Nonlinear propagation effects limit the maximum contrast obtainable with both harmonic and pulse inversion Doppler techniques.

Usefulness of contrast material in MR of patients with neurofibromatosis type 1.

PURPOSE: Our objective was to determine the usefulness of routine administration of contrast material in brain MR imaging for the evaluation of areas of probable myelin vacuolization and neoplasms in patients with neurofibromatosis type 1 (NF-1). METHODS: We retrospectively reviewed 112 consecutive contrast-enhanced brain MR studies obtained over a period of 7 years in 109 symptomatic and asymptomatic patients compiled from two institutional NF-1 data bases. MR studies were analyzed for areas of probable myelin vacuolization, with attention to degree of enhancement and its impact on lesion detection and characterization. Usefulness of contrast material was graded as 0 = not useful, 1+ = somewhat useful, and 2+ = useful. RESULTS: Of 112 studies, 45% (n = 49) were normal. In the remaining 63 studies, 88 regions of probable myelin vacuolization and 52 tumors were identified. Enhancement was not observed in any regions of probable myelin vacuolization. Enhancement was present in 31% of tumors, and, of these, was found to be useful in 44%, somewhat useful in 12%, and not useful in 44%. For enhancing tumors, contrast agent was useful for lesion detection in 19% and for lesion characterization in 25%. CONCLUSION: Contrast administration is useful in baseline MR studies to maximize tumor detection and characterization, to add confidence to the diagnosis of benign probable myelin vacuolization, and to document stability of neoplasms on follow-up examinations.

Gallbladder nonvisualization with pericholecystic rim sign: morphine-augmentation optimizes diagnosis of acute cholecystitis.

UNLABELLED: This study investigated the value of morphine-augmentation in patients who demonstrated gallbladder nonvisualization with a pericholecystic rim sign at 1 hr, a cholescintigraphic pattern considered highly predictive of acute cholecystitis. METHODS: Retrospectively, 170 consecutive morphine-augmented cholescintigrams were analyzed for the presence of a pericholecystic rim sign, marked or mild, associated with gallbladder nonvisualization at 1 hr (before morphine); those with a pericholecystic rim sign were further evaluated for persistent gallbladder nonvisualization versus gallbladder visualization after morphine. Scintigraphic interpretations were correlated with surgical pathology or clinical diagnosis. RESULTS: Before morphine, 43/170 (25%) patients demonstrated gallbladder nonvisualization with a pericholecystic rim sign. Since only 31 had acute cholecystitis, a diagnosis based solely on that scintigraphic pattern would have resulted in 12 false-positives. After morphine, gallbladder visualization correctly excluded acute cholecystitis in seven; a single false-negative was encountered; five false-positives remained. Morphine-augmentation improved the positive predictive value from 72% (gallbladder nonvisualization with pericholecystic rim sign before morphine) to 86% (gallbladder nonvisualization after morphine). Of 24 patients with marked pericholecystic rim signs, 21 had acute cholecystitis. Of 31 with acute cholecystitis, however, 10 (32%) had a mild pericholecystic rim sign. CONCLUSION: Morphine-augmented cholescintigraphy optimizes the diagnosis of acute cholecystitis in patients with the suggestive, but not pathognomonic, cholescintigraphic pattern at 1 hr of gallbladder nonvisualization with a pericholecystic rim sign, regardless of its intensity.

Serological evidence of Hantaan virus infection in the United States.

We found low titers of fluorescent antibodies against Hantaan virus, the etiologic agent of Korean hemorrhagic fever, in sera from 7 of 1,035 patients with febrile illnesses of unknown origin and from 6 of 664 blood donors in the United States. All but 1 of these individuals possessed neutralizing antibodies against Hantaan virus. This was a 31-year-old research technician who had worked with laboratory rodents with virus-induced tumors, but had not traveled abroad, suggesting that infection with Hantaan virus or a closely related agent was locally acquired. However, the precise source of his infection remains unclear.

The effects of betel-nut chewing on the buccal mucosa: a histological study.

Sixty-two "leukoplakias" from the cheeks of betel-nut chewers in West Malaysia were studied histologically. Ten biopsies were from non-tobacco betel-nut chewers. An amorphous von Kossa positive layer was seen on the keratin surface in 42 specimens. Tobacco did not appear essential for its formation, and it appeared to be significantly associated with parakeratosis. Its possible significance as a cuticle-like layer prolonging contact between carcinogens and the mucosa is discussed.Parakeratosis appeared to be the most common form of cornification seen, and the mitotic activity in parakeratinized leukoplakias appeared to be significantly greater than orthokeratinized leukoplakias.Comparison with studies on other population samples using different quids suggested that severe histological changes were more likely to be seen when tobacoo-containing quids were chewed as compared to non-tobacco-containing quids.An attempt to correlate the histological changes seen with the clinical habit in leukoplakias from chewers using tobacco-containing quids suggested that epithelial atrophy appeared to be significantly related to the duration of the habit but not to the "intensity" of the habit.