Precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest supported by differentiation curve

Objectives

To evaluate the precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest (ROI) supported by differentiation curves.

Study design

We used vascular models (actual attenuation value of the wall: 87 HU) with wall thicknesses of 1.5, 1.0, or 0.5 mm, filled with contrast material of 250, 348, or 436 HU. The nine vascular models were scanned with a 64-detector CT. The wall attenuation values were measured using three sizes (diameter: 0.5, 1.0, and 1.5 mm) of ROIs without differentiation curves. Sixteen measurements were repeated for each vascular model by each of two operators. Measurements supported by differentiation curves were also performed. We used analyses of variance with repeated measures for the measured attenuations for each size of the ROI.

Results

Without differentiation curves, there were significant differences in the attenuation values of the wall among the three densities of contrast material, and the attenuation values tended to be overestimated more as the contrast material density increased. Operator dependencies were also found in measurements for 0.5- and 1.5-mm thickness models. With differentiation curves, measurements were not possible for 0.5- and 1.0-mm thickness models. Using differentiation curves for 1.5-mm thickness models with a ROI of 1.0- or 1.5-mm diameter, the wall attenuations were not affected by the contrast material densities and were operator independent, measuring between 75 and 103 HU.

Conclusions

The use of differentiation curves can improve the precision and accuracy in wall attenuation measurement using a ROI technique, while measurements for walls of ≤1.0 mm thickness are difficult.     

Neural correlates of auditory perception in Williams syndrome: an fMRI study

Williams syndrome (WS), a neurogenetic developmental disorder, is characterized by a rare fractionation of higher cortical functioning: selective preservation of certain complex faculties (language, music, face processing, and sociability) in contrast to marked and severe deficits in nearly every other cognitive domain (reasoning, spatial ability, motor coordination, arithmetic, problem solving). WS people are also known to suffer from hyperacusis and to experience heightened emotional reactions to music and certain classes of noise. We used functional magnetic resonance imaging to examine the neural basis of auditory processing of music and noise in WS patients and age-matched controls and found strikingly different patterns of neural organization between the groups. Those regions supporting music and noise processing in normal subjects were found not to be consistently activated in the WS participants (e.g., superior temporal and middle temporal gyri). Instead, the WS participants showed significantly reduced activation in the temporal lobes coupled with significantly greater activation in the right amygdala. In addition, WS participants (but not controls) showed a widely distributed network of activation in cortical and subcortical structures, including the brain stem, during music processing. Taken together with previous ERP and cytoarchitectonic studies, this first published report of WS using fMRI provides additional evidence of a different neurofunctional organization in WS people than normal people, which may help to explain their atypical reactions to sound. These results constitute an important first step in drawing out the links between genes, brain, cognition, and behavior in Williams syndrome.     

Imaging technologies and techniques

Equipment manufacturers provide contrast-specific detection techniques that have excellent sensitivity and excellent agent-to-tissue specificity along with helpful tools that improve workflow efficiency dramatically. Excellent contrast agents have been approved for LV opacification and are available worldwide. Techniques designed for low-MI imaging offer real-time acquisition capabilities and lead to faster examinations. Techniques designed for medium-MI imaging offer better sensitivity than low-MI techniques while maintaining the benefit of rapid image acquisition. Techniques designed for high-MI imaging offer the best sensitivity with longer acquisition times. These techniques are viable means for imaging contrast agents tailored to clinical needs. Progress by contrast agent manufacturers, equipment manufacturers, and physicians will continue to drive improvements in the areas of detection and clinical workflow for improved patient care.     

Rapid diagnosis of acute bacterial meningitis: role of a broad range 16S rRNA polymerase chain reaction

Background: Acute bacterial meningitis is a significant cause of morbidity and mortality throughout the world. It can be difficult to diagnose, as the symptoms and signs are often non-specific. Study Objective: To evaluate the performance of an in-house semi-nested polymerase chain reaction (PCR) assay targeting the 16S rRNA gene of Eubacteria for the rapid diagnosis of acute bacterial meningitis using cerebrospinal fluid (CSF) specimens. Methods: A total of 112 CSF samples from 112 patients were used in the study. Among these, 32 samples were obtained from confirmed cases of Streptococcus pneumoniae, six samples were obtained from confirmed cases of Haemophilus influenzae, one sample from a confirmed case of Neisseria meningitidis, and 10 cases of clinically suspected acute bacterial meningitis. The remaining 63 CSF samples were obtained from patients with non-infectious illnesses (n = 47) of the central nervous system (CNS) and autopsy-confirmed tuberculous meningitis (n = 16). Results: The assay had an overall sensitivity of 93% (95% confidence interval [CI] 0.81–0.98, negative predictive value = 95%) and a specificity of 98% (95% CI 0.92–1.0, positive predictive value = 98%). Conclusion: These preliminary findings suggest that the semi-nested PCR assay targeting the 16S rRNA gene may be used as a rapid test for the diagnosis of acute bacterial meningitis.     

Muscle blood flow in diabetes mellitus. Evidence of abnormality after exercise.

OBJECTIVE--To determine whether muscle blood flow before and after exercise is abnormal in patients with diabetes mellitus. RESEARCH DESIGN AND METHODS--Muscle blood flow (MBF) was measured with the 133Xe clearance technique in 15 nondiabetic subjects, 10 patients with insulin-dependent diabetes mellitus (IDDM), and 11 patients with non-insulin-dependent diabetes (NIDDM) at rest and after exercise. None of the patients had neuropathy. RESULTS--The median resting MBF was similar in all three groups. The median postexercise MBF was significantly greater in nondiabetic subjects (40.1 ml.min-1.100 g-1 of tissue) than in patients with IDDM (25.7 ml.min-1.100 g-1 of tissue; P less than 0.01) or NIDDM (14 ml.min-1.100 g-1 of tissue; P less than 0.01). The difference between IDDM and NIDDM was not significant. CONCLUSIONS--Diabetic patients have abnormalities of MBF in response to exercise. This abnormality occurs in the absence of clinical diabetic neuropathy.     

Assessment of leptomeningeal collaterals using dynamic CT angiography in patients with acute ischemic stroke

Whole-brain dynamic time-resolved computed tomography angiography (CTA) is a technique developed on the new 320-detector row CT scanner capable of generating time-resolved cerebral angiograms from skull base to vertex. Unlike a conventional cerebral angiogram, this technique visualizes pial arterial filling in all vascular territories, thereby providing additional hemodynamic information. Ours was a retrospective study of consecutive patients with ischemic stroke and M1 middle cerebral artery +/−intracranial internal carotid artery occlusions presenting to our center from June 2010 and undergoing dynamic time-resolved CTA and perfusion CT within 6 hours of symptom onset. Leptomeningeal collateral status was assessed by determining relative prominence of pial arteries in the ischemic region, rate and extent of retrograde flow, and various topographical patterns of pial arterial filling. Twenty-five patients were included in the study. We demonstrate the existence of the following novel properties of leptomeningeal collaterals in humans: (a) posterior (posterior cerebral artery (PCA)–MCA) dominant collateralization, (b) intra-territorial ‘within MCA region'' leptomeningeal collaterals, and (c) significant variability in size, extent, and retrograde filling time in pial arteries. We also describe a simple and reliable collateral grading template that, for the first time on dynamic CTA, incorporates back-filling time as well as size and extent of collateral filling.