Classification Of Stenoses Research Articles

Classification of Intracranial Stenoses: Discrepancies between Transcranial Duplex Sonography and Computed Tomography Angiography

Transcranial color-coded duplex sonography (TCCS) and computed tomography angiography (CTA) are widely used to identify intracranial stenoses (ISs). We assessed concordance of IS grading between TCCS and CTA and proposed new TCCS criteria for severe IS ≥70%. One hundred two stroke patients (70 ± 13 y) with TCCS-identified IS were included. TCCS and CTA were performed within 24 h after admission. TCCS peak systolic velocity cutoffs for <50%/50%–69% stenoses were ≥155/≥220 cm/s (middle cerebral artery [MCA]-M1), ≥100/≥140 cm/s (MCA-M2), ≥120/≥155 cm/s (anterior cerebral artery [ACA]-A1), ≥100/≥145 cm/s (posterior cerebral artery [PCA]-P1 and PCA-P2), ≥90/≥120 cm/s (vertebral artery [VA]-V4) and ≥100/≥140 cm/s (basilar artery [BA]). Criteria for ≥70% stenoses were, despite variable flow velocities, post-stenotic flow alterations and/or leptomeningeal collateral flow. One hundred seventy-seven ISs were detected by TCCS. The number and grade (<50%/50%–69%/≥70%) of ISs were MCA 70 (39/19/12), BA 24 (9/11/4), ACA 21 (14/7/0), PCA 49 (29/15/5) and VA 13 (2/6/5). IS localization was confirmed by CTA in 84 of 177 cases (48%): MCA, 41/70 (59%); BA, 16/24 (67%); ACA 2/21, (10%); PCA, 17/49 (35%); VA, 8/13 (62%). Concordance between TCCS and CTA grading was (<50%/50%–69%/≥70%) 17%/19%/77%. TCCS and CTA exhibited substantial differences in the detection and grading of IS. Higher concordance rates for severe stenosis support our proposed TCCS criteria.

Impact of increasing dose of intracoronary adenosine on peak hyperemia duration during fractional flow reserve assessment

BackgroundFractional Flow Reserve (FFR) is currently indicated as a first line strategy for the functional assessment of intermediate coronary stenoses. However, the protocol for inducing hyperemia still lacks standardization. Intracoronary adenosine boli, with a progressive increase to high-dosage, have been proposed as a sensitive and accurate strategy for the classification of coronary stenoses, although being potentially affected by the achievement of plateau of the effect and by a less prolonged and stable hyperemia as compared to intravenous administration. Therefore, the aim of the present study was to define the conditioning parameters and assess the impact of increasing-dose intracoronary adenosine on peak hyperemia duration in patients undergoing FFR for intermediate coronary stenoses. MethodsFFR was assessed in patients with intermediate (40 to 70%) lesions by pressure-recording guidewire (Prime Wire, Volcano), after induction of hyperemia with intracoronary boli of adenosine (from 60 to 1440 μg, with dose doubling at each step). Hyperemic duration was defined as the time for the variation form minimum FFR ± 0.02 and time to recovery till baseline values. ResultsWe included 87 patients, undergoing FFR evaluation of 101 lesions. Mean peak hyperemia duration and time to recovery significantly increased with adenosine doses escalation (p = 0.02 and p < 0.001). Peak hyperemia duration and time to recovery with 1440 μg adenosine were 14.5 ± 12.6 s and 45.2 ± 30.7 s, respectively. Hyperemia duration was not related to Quantitative Coronary Angiography (QCA) parameters or FFR values. In fact, a similar increase in the time of hyperemic peak was noted when comparing patients with positive or negative FFR (pbetween = 0.87) or patients with lesions < or ≥20 mm (pbetween = 0.92) and lesions involving left main coronary or proximal left anterior descending artery (LAD) (pbetween = 0.07). A linear relationship was observed between time to recovery and FFR variations, with a greater time to baseline required in patients with FFR ≤ 0.80 (p = 0.003) and in lesions ≥ 20 mm (p = 0.006), but not in LAD/LM lesions (p = 0.55). ConclusionsThe present study shows a progressive raise in the duration of peak hyperemia and time to recovery, after the administration of increasing doses of intracoronary adenosine for the assessment of FFR. Therefore, considering the potential advantages of a high-dose adenosine protocol, allowing a more prolonged hyperemia and a more precise and reliable measurement of FFR, further larger studies with such FFR strategy should certainly be advocated to confirm its safety and benefits, before its routinely use recommendation.

Automatic Algorithm for Segmentation of Atherosclerotic Carotid Plaque

Carotid atherosclerosis is one of the major causes of stroke. The determination of the intima-media thickness, the identification of carotid atherosclerotic plaque, and the classification of the different stenoses are considered as important parameters for the assessment of atherosclerotic diseases. The aim of this work is to segment the plaques and to allow a better comprehension of carotid atherosclerosis. We considered 44 subjects, 22 with and 22 without the presence of plaques in the carotid axis, and we applied the snake algorithm. The resulting interclass correlation coefficients (ICCs) were significant for all 3 parameters (mean echogenicity: ICC1 = .78 [95%CI: .55-0.90]; perimeter: ICC2 = .81 [95%CI: .61-0.92]; area: ICC3 = .89 [95%CI: .75-0.95]). The diagnostic accuracy was 82%, with an appropriate cutoff value of 224.5, sensitivity of 79%, and specificity of 85%. In this study, we developed an automatic method to identify the carotid plaque. Our results showed that an automatic system of image segmentation could be used to identify, characterize, and measure atherosclerotic carotid plaques.

Institutional differences in carotid artery duplex diagnostic criteria result in significant variability in classification of carotid artery stenoses and likely lead to disparities in care.

The indications for carotid revascularization are based almost exclusively on the results of carotid duplex ultrasonography. Noninvasive vascular laboratories show large variation in the diagnostic criteria used to classify degree of carotid artery stenosis. We hypothesize that variability of these diagnostic criteria causes significant variation in stenosis classification directly affecting the number of revascularizations and associated costs. The diagnostic criteria to interpret carotid duplex ultrasounds were obtained from 10 New England institutions. All carotid duplex scans performed at our institution were reviewed from 2008 to 2012. Using the diagnostic criteria from each institution, the degree of stenosis that would have been reported was classified as 70% to 99% asymptomatic, 80% to 99% asymptomatic, and 50% to 99% symptomatic. We then calculated the theoretical number of carotid revascularization procedures that this cohort would be offered using each institution's diagnostic criteria and the costs of these procedures based on reimbursement rates. Among 10 614 patients who underwent 15 534 carotid duplex scans, 31 025 arteries were reviewed. Application of the 10 institutions' criteria to the patients from our institution yielded marked variation in the number classified as 70% to 99% asymptomatic (range, 186-2201), 80% to 99% asymptomatic (range, 78-426), and 50% to 99% symptomatic (range, 157-781). If revascularizations were based on these results, costs would range from $2.2 to $26 million, $0.9 to $5.0 million, and $1.9 to $9.2 million, respectively. Differences in diagnostic criteria to interpret carotid ultrasound result in significant variation in classification of carotid artery stenosis, likely leading to differences in the number and subsequent costs of revascularizations. This theoretical model highlights the need for standardization of carotid duplex criteria.

Institutional Differences in Carotid Artery Duplex Diagnostic Criteria Result in Significant Variability in Classification of Carotid Artery Stenoses and Likely Lead to Disparities in Care

Institutional Differences in Carotid Artery Duplex Diagnostic Criteria Result in Significant Variability in Classification of Carotid Artery Stenoses and Likely Lead to Disparities in Care

Stenoses of the salivary ducts-sialendoscopy based diagnosis and treatment

Our aim was to analyse the nature of a sialendoscopy-based classification and present its use in the treatment of stenoses of Wharton's and Stensen's ducts. The classification of stenoses of Wharton's duct has not been published before. We did 133 sialendoscopies in 114 patients who presented with possible obstruction of the ducts to the tertiary centre for ENT at the University Department in Poznań. Twenty-seven patients had their parotid ducts treated, and 24 their submandibular ducts. Suspicion of stenotic changes of the ductal system was suggested during ultrasound examination. They were examined with semirigid endoscopes that enabled direct visualisation of the stenotic areas. A total of 69 stenoses were diagnosed in 51 patients. Stenoses were divided into three groups according to their site. Patients with stenosis of the salivary ducts were treated by dilatation of the stenotic area, intraductal steroid injections, and insertion of a stent for 14–21 days. Forty of the 51 reported considerable improvement, and 7 partial improvement. Four patients had no improvement.Sialendoscopy is a safe way to treat obstruction of the salivary glands. Short and medium term follow up show that it is extremely successful.

Comprehensive approach to restoration of function in patients with radiation‐induced pharyngoesophageal stenosis: Report of 31 patients and proposal of new classification scheme

The treatment for upper aerodigestive tract malignancy with external beam radiation therapy and chemotherapy can result in a "cure," yet result in pharyngoesophageal (PE) stenosis. To improve communication, compare therapeutic results, and assist in treatment planning, we developed a new classification system to describe PE stenoses. Additionally, we analyzed our 6-year experience. The new classification system was defined and used to assess patient management. Thirty-one patients underwent treatment for PE stenoses using: 4 rendezvous dilations, 3 regional, and 24 free tissue transfers. Overall success was based on airway status, speech, and swallowing outcomes. Classification of posttreatment stenoses has been applied to this patient group. It is effective in defining the problem and considerations related to treatment planning and surgical access when augmentation pharyngoplasty is required. Patients with an intact larynx have many issues that make recovery of function less consistent, despite segment restoration.

Sialendoscopy‐based diagnosis and classification of parotid duct stenoses

To assess stenoses of Stensen's duct considering findings provided by sialendoscopy-based direct visualization. A practical classification scheme based on different parameters is presented. Ultrasonography and sialendoscopy were used to diagnose and analyze symptomatic stenoses of the parotid gland excretory duct in 93 patients. Sialendoscopy was performed with semirigid endoscopes that enabled direct evaluation and classification of those stenoses in terms of tissue quality, luminal narrowing, extend, number, location, and in consideration of possible etiologic diseases or conditions. A total of 111 stenoses were diagnosed in 93 patients. Three types could be distinguished. Stenoses were inflammation-dominated with various narrowing of the lumen (type I) in 16.1% of patients, fibrous and web-associated, predominant incomplete (luminal narrowing <50%, type II) in 18.3%, and fibrous, predominant high-grade (luminal narrowing >50%, type III) in 66.6%. A length of more than 1 cm or diffuse involvement of the duct system was observed in 12.9% of cases. Together 70.1% of all stenoses were found in middle and distal regions of the duct. Multiple stenoses were found in 12.9% of patients, bilateral in 6.5%. Of all patients, 45.2% had diseases possibly implicated in the etiogenesis. Type III stenoses were associated with these comorbidities in up to 100%. Minimally invasive techniques play a central role in the diagnosis and treatment of Stensen's duct stenoses. Sialendoscopy is the diagnostic method of first choice. It enables an exact and direct classification of stenoses and provides additional information for planning effective treatment.

Flussuntersuchungen an Strömungsphantomen im Vor- und Nachlauf stenoseförmiger Verengungen mittels geschwindigkeitskodierter MRT und numerischer Simulation der Fluiddynamik / Fluid studies on flow behaviour in narrowing vessels with PC-velocimetry and numerical simulations

Fluid dynamics play an important role in arterial diseases. PC-velocimetry as a magnetic resonance (MR) method is a useful tool for the examination of blood vessels, in particular in haemodynamics and morphology. Due to signal loss caused by turbulent flow, classification of stenoses remains difficult. In the presence of metallic stents, susceptibility effects and RF-artefacts further deteriorate image quality. Regarding fluid dynamics, stenosis, stent and restenosis (i.e., re-closing of the vessel in areas with stents) have similar properties: the flow close to an obstacle is accelerated and after a specific length, the so-called reattachment length, it redevelops into its original flow profile. Depending on the shape of the obstacle and its reattachment length, a method is developed to classify stenosis using MR-imaging. Enlarged, simplified stenosis models (phantoms) were examined and were also modelled using computational fluid dynamics (CFD). MR- and CFD-measurements show influences of the stenosis shape, especially the diameter. In graphical analysis (streamline and vector plots), a reattachment length of 6.7xstep size could be determined under laminar conditions and nonpulsatile flow. Stenosis and other narrowing of vessels are classifiable more exactly using PC-velocimetry. From the flow behaviour in the area around the narrowing of the vessel wall, the character of the stenosis can be derived. But more parameters, as bended vessel shapes, pulsated flow, non-Newtonian flow behaviour as well as elastic properties of the vessels need to be incorporated.

Coronary Artery Stenosis Quantification Using Multislice Computed Tomography

Reliable noninvasive detection of stenoses with multislice computed tomography (MSCT) is feasible. This study's aim was to analyze the agreement, correlation, and reliability of MSCT with conventional coronary angiography as the reference standard for quantification of coronary artery stenoses. A total of 118 significant (at least 50%) coronary artery stenoses with a reference vessel diameter of at least 1.5 mm in 62 patients were analyzed by MSCT using 16 detector rows (Aquilion, Toshiba, Otawara, Japan), multisegment reconstruction, and voxel sizes of 0.35x0.35x0.5 mm. The degree of stenosis on MSCT and quantitative coronary angiography (QCA) was measured by correlating the difference between the reference vessel diameter (average of 2 measurements directly proximal and distal to the stenosis) and the stenotic vessel diameter to the reference vessel diameter. Correlation between the percent diameter stenosis determined by MSCT (78.2+/-13.6%) and QCA (76.0+/-14.8%) was significant (P<0.001) but only moderately so (R=0.51). Bland-Altman analysis revealed no systematic under- or overestimation with MSCT but large limits of agreements (+/-27.6%). Also the limits of agreement for interobserver agreement (reliability) of MSCT data were considerably large (+/-24.8%). Among the 27 coronary artery stenoses with a reference diameter of at least 3.5 mm, there was improved correlation (R=0.80) and the limits of agreement between MSCT and QCA were significantly smaller (+/-17.3%, P<0.008). The agreement between MSCT and QCA was not significantly different for stenoses with no calcification or only calcium spots (+/-28.2%) as compared with those with moderate-or-severe calcifications (+/-27.3%; P=0.8). MSCT allowed correct classification of coronary stenoses into low-grade (below 75%) and high-grade stenoses (at least 75%), in 62% (73 of 118). The accuracy and reliability of coronary artery stenosis quantification with MSCT using isotropic voxel sizes and multisegment reconstruction is still too low to recommend routine clinical application because of rather low agreement, correlation, and reliability. Despite these limitations, the current results demonstrate the potential of MSCT for reliable and accurate quantification of coronary artery stenoses in the near future provided that further improvements in spatial and temporal resolution will be achieved.

Sonographic Examination of the Carotid Arteries

Ultrasonography (US) of the carotid arteries is a common imaging study performed for diagnosis of carotid artery disease. In the United States, carotid US may be the only diagnostic imaging modality performed before carotid endarterectomy. Therefore, the information obtained with carotid US must be reliable and reproducible. Technical parameters that can affect the accuracy of carotid US results include the Doppler angle, sample volume box, color Doppler sampling window, color velocity scale, and color gain. Important factors in diagnosis of atherosclerotic disease of the extracranial carotid arteries are the intima-media thickness, plaque morphology, criteria for grading stenosis, limiting factors such as the presence of dissection or cardiac abnormalities, distinction between near occlusion and total occlusion, and the presence of a subclavian steal. Challenges to the consistency of carotid US results may include lack of a standard protocol, poor Doppler technique, inexperience in interpretation of hemodynamic changes reflected in the Doppler waveform, artifacts, and physical challenges. Hindrances in the classification of problematic carotid artery stenoses may be overcome by following a standard protocol and optimizing scanning techniques and Doppler settings.

Variability of Doppler Velocity Ratios as a Function of Location in the Common Carotid Artery: Potential Problems When Quantifying Significant Internal Carotid Artery Stenoses

Introduction The use of the internal carotid artery (ICA) to common carotid artery (CCA) peak systolic velocity ratio (ICApsv/CCApsv) to quantitate ICA stenosis has been challenged based on the variability of Doppler-derived velocities at various locations within the CCA. We investigated these alleged differences to determine whether they affect actual classification of significant ICA stenoses. Methods Data from consecutive patients for an 18-month period were prospectively entered into a database. Only initial studies were included in this investigation. Follow-up examinations, postendarterectomy vessels, ICA occlusions, and CCA vessels with a PSV of &gt;150 cm/sec were excluded from analysis. CCApsvand ICApsv/CCApsvwere obtained and based on Doppler analysis at both the proximal most visualized CCA segment (proximal), and 1.5 cm proximal to the ICA flow divider (distal). ICApsv/CCApsv values of ≥ 2, ≥ 3, and ≥ 4 were used as threshold values for ≥ 50%, ≥ 60%, and ≥ 70% diameter stenoses. Results A total of 383 patients and 588 vessels were analyzed. CCApsv -proximal values, 75 ± 20 cm/sec, were significantly higher than CCApsv -distal, 68 ± 16 cm/sec (p &lt; 0.001). ICApsv/ CCApsv -distal ratios, 2.36 ± 2.77, were significantly higher than ICApsv/ CCApsv -proximal, 2.11 ± 2.46, (p &lt; 0.001). The average absolute difference between CCApsv -proximal and CCApsv -distal was 15% ± 13% (range, 0%–93%). For an ICApsv/CCApsv ≥ 50%, proximal and distal ratios would both be &lt; 2 in 66%, ≥ 2 in 29%, and 5% were contradictory. For an ICApsv/CCApsv ≥ 60%, proximal and distal ratios would both be &lt; 3 in 78%, ≥ 3 in 18%, and 4% contradictory. For an ICApsv/CCApsv ≥ 70%, proximal and distal ratios would both be &lt; 4 in 85%, ≥ 4 in 12%, and in 3% contradictory. Conclusions Significant differences in ICApsv/CCApsv calculation as a function of location of the CCApsv measurement were confirmed. Proximal and distal sampling sites, however, did not affect ICApsv/CCApsv classifications for 95% of the vessels analyzed. For contradictory classifications, ICApsv/CCApsv -distal had more potential for a positive result. To improve accuracy and address sensitivity or specificity interpretation parameters, the influence of the CCA sampling site should be considered and standardized when using carotid ratio criteria.

Endoscopic management of postoperative biliary strictures

Postoperative biliary strictures most often occur after cholecystectomy and have become commoner in the laparoscopic cholecystectomy era. Endoscopic treatment of postoperative strictures is feasible in 85% of cases, and long-term success is achieved in over 80% of patients completing a treatment protocol. Endoscopic treatment typically requires placement of multiple stents for a prolonged period of time. The best outcomes have been achieved by increasing the duration of stenting and the number of stents until there is complete cholangiographic resolution of the stricture. Excluding strictures after liver transplantion, this article reviews the pathogenesis, classification, and endoscopic management of postoperative biliary stenoses.

A comparison between colour duplex ultrasonography and arteriography for imaging infrapopliteal arterial lesions

To investigate the agreement between colour duplex ultrasonography and digital subtraction arteriography of the infrapopliteal arteries. Retrospective, blinded study. Vascular laboratory and Radiology Department, University Hospital. The infrapopliteal vasculature was examined in a total of 51 limbs by both colour duplex ultrasound and digital subtraction angiography. By examining all arteries from the distal popliteal to the pedal arteries, a total of 204 individual arterial segments were available for analysis. Each segment was graded as 0-49%, 50-99% diameter reduced or occluded by both modalities. Using ultrasound, classification of stenoses was achieved by observing peak systolic velocity ratios; a doubling of peak systolic velocity indicating a > or = 50% diameter reducing stenosis. Where no Doppler signal could be obtained, the vessel was assumed to be occluded. From angiographic studies, two radiologists separately and blindly assessed the extent of disease for each infrapopliteal artery noting areas of > or = 50% diameter reduction and occlusion. The Kappa statistic was used to examine the level of agreement between angiography and ultrasound as well as between both radiologists. The Kappa level (95% confidence interval) of agreement between ultrasound and angiographic assessments for distinguishing patent from occluded segments was 0.61 (0.49-0.74) for all segments. The equivalent agreement between radiologists was 0.80 (0.70-0.89). Poorest agreement was observed from ultrasound assessments of the peroneal and tibioperoneal trunk arterial segments. Since agreement between colour duplex scanning and angiography never fell significantly below levels achieved between two radiologists, we conclude that colour duplex ultrasound can be used to assess infrapopliteal artery patency.

Interobserver agreement for 10% categories of angiographic carotid stenosis.

Although the reliability of the assessment of severe 70% to 99% carotid stenosis by carotid angiography has been proven excellent, this may not necessarily be the case for a more detailed classification of carotid stenoses by 10% categories. Angiograms of the carotid arteries were assessed pairwise by three independent, experienced observers. The measurements of the degree of stenosis of both the carotid bifurcation and the internal carotid artery were made according to the European Carotid Surgery Trial method. Kappa statistics were used to assess the agreement beyond chance for severe (70% to 99%) carotid stenosis (kappa 1) and for 10% categories of carotid stenosis (kappa 2). The penalty scores were adjusted by weights for the relative difference in risk (RDR) of stroke in the ipsilateral carotid distribution between the 10% categories (kappa 3). An adjustment of the RDR method was made by assuming that only patients with a severe carotid stenosis would undergo surgery, and the penalty would be 0 if no disagreement would exist about the indication for surgery (kappa 4). An even further adjustment (kappa 5) was made by assuming that assessment of the rate of carotid stenosis by one or both observers would lead to different treatment recommendations in 50% of the cases, and accordingly the penalty for disagreement (RDR) was halved. One hundred twenty-one carotid bifurcations in 65 patients with a transient ischemic attack or nondisabling stroke were assessed. The intraclass correlation between the exact estimates of carotid stenosis was .90 (95% confidence interval, .85 to .92). The mean difference in stenosis between the two raters was 0.8% (95% confidence interval, -2.1% to 3.7%). kappa 1 to kappa 5 equaled 0.80, 0.40, 0.79, 0.91, and 0.92, respectively. Interobserver agreement for distinct 10% categories of angiographic carotid stenosis is moderate, but when realistic risk- and decision-based weights are used, agreement between experienced observers can be almost perfect.

CT angiography in carotid stenosis

Prospective evaluation of the accuracy of CT angiography (CTA) with different postprocessing for extracranial carotid artery in comparison with DSA. One hundred patients were studied with standardized CTA. For postprocessing, MPR, MIP, and 3D reconstruction based on segmentation with upper and lower threshold were used. Intravascular density profiles were considered. All CTA studies were correlated with intra-arterial angiography. The degree and classification of stenoses was determined using the guidelines established by the NASCET collaborators. Measurement of stenosis was possible by MPR in 82.5%, by MIP in 85%, and 3D in 100%. Correct classification was found in 65.5% for MPR, 66% for MIP and 88.5% for 3D. The sensitivity for severe stenoses was 74% for MPR, 82% for MIP, and 93% for 3D. The specificity of these methods was 98%, 96%, and 97%, respectively. All carotid occlusions were correctly identified, no carotid artery was wrongly classified as occluded. CT angiography allows reliable examinations in carotid artery stenoses and occlusions. 3D reconstruction based on threshold segmentation is superior to MPR and MIP. In some circumstances, e.g., carotid occlusion, further investigation by invasive procedures is not necessary.

Correction of central venous stenoses: Use of angioplasty and vascular Wallstents

Central venous stenoses are a frequent complication in hemodialysis patients. These lesions lead to fistula thromboses, arm swelling, and limit future vascular access. Stenoses are characterized by excellent initial response to transluminal angioplasty but rapid recurrence. Response to angioplasty allows classification of stenoses as elastic or nonelastic. The success of angioplasty alone in 30 patients with central venous stenoses was compared to angioplasty and Wallstent placement in 11 patients with recurrent stenoses. In those who had angioplasty alone, 7%+ failed angioplasty, 70% had > or = 50% improvement in the luminal diameter while 23% showed no improvement due to elastic lesions. Subsequently, 81% of those with a successful result restenosed at an average of 7.6 months while 100% of elastic lesions occluded in an average of 2.9 months. In the 10 patients who underwent angioplasty and Wallstent placement, 5 were due to elastic lesions with four recurrences at a mean of 8.6 months. Four of five patients (80%) stented with nonelastic lesions had reappearance of symptoms at a mean of 4.2 months. We conclude that vascular stents should be reserved for those lesions that show elastic recoil after standard angioplasty.

Proposed grading system for subglottic stenosis based on endotracheal tube sizes.

The classification of airway stenoses has been a problem for many years. As a result, both intradepartmental and interdepartmental comparisons of airway sizes remain difficult. It follows that comparisons of therapeutic maneuvers are even more difficult. A system is proposed that is simple, reproducible, and based on a readily available reference standard. Endotracheal tubes, which are manufactured to high standards of precision and accuracy, can be used to determine the size of an obstructed airway at its smallest point. The endotracheal tube that will pass through the lumen, if one exists, and tolerate normal leak pressures (10 to 25 cm H2O), can be compared to the expected age-appropriate endotracheal tube size. By using the outside diameters of the endotracheal tubes, the maximum percentage of airway obstruction can be determined. We present a conversion of tube size to the proposed grading scale: grade I up to 50% obstruction, grade II from 51% to 70%, and grade III above 70% with any detectable lumen. An airway with no lumen is assigned to grade IV.

Classification of lower limb arterial stenoses from doppler blood flow signal analysis with time-frequency representation and pattern recognition techniques

A pattern recognition system was used to classify Doppler blood flow signals for the determination of lower limb arterial stenoses. The diagnostic features were extracted from time-frequency representations of Doppler signals. Three techniques were tested to estimate time-frequency representations: the short-time Fourier transform, the autoregressive (AR) modeling, and the Bessel distribution. A boundary tracking algorithm was proposed to extract the frequency contour of the Doppler time-frequency representations. Based on the characteristics of the Doppler frequency contour, shape descriptors from an autoregressive analysis were proposed as diagnostic features. Simple algorithms were proposed to normalize these autoregressive shape descriptors. Amplitude distribution of the Doppler time-frequency representation was also found useful for stenosis classification. A total of 379 arterial segments from the aorta to the popliteal artery were classified by the pattern recognition system into three categories of diameter reduction (0–19%, 20–49%, and 50–99%). The short-time Fourier transform provided an overall accuracy of 80% (kappa = 0.38); AR modeling, 81% (kappa = 0.42); and the Bessel distribution, 82% (kappa = 0.43). All these results are better than those based on visual interpretation (accuracy = 76%, kappa = 0.29) performed by a trained technologist. The AR modeling and the Bessel distribution improved the performance of the pattern recognition system in comparison with the short-time Fourier transform. It is likely that with further improvement, the pattern recognition approach will be a useful clinical tool to quantify stenoses and to follow the disease progression with more reliability and less bias than visual interpretation as done currently in clinical practice.

Middle Cerebral Artery Stenoses: Assessment by Magnetic Resonance Angiography and Transcranial Doppler Ultrasound

Magnetic resonance angiography (MRA) findings of uni- or bilateral middle cerebral artery (MCA) stenosis were compared with results of transcranial Doppler ultrasound (TCD) and digital subtraction angiography (DSA). Eighteen patients with 22 MCA stenoses were selected by TCD criteria. To evaluate the diagnostic accuracy of MRA, TCD and DSA, criteria for classification of stenoses were established. MRA confirmed 21 MCA stenoses as revealed by TCD (n = 22). DSA did not demonstrate MCA stenoses in 6 cases diagnosed by TCD (classification grade I) and MRA. The classification of MCA stenoses by MRA correlated with TCD in 11 (50%) cases, while stenosis was underestimated by MRA in 3 (14%) and overestimated in 8 (36%) MCAs. Whereas the sensitivity of MRA for the detection of MCA stenoses compared to TCD and DSA findings was very high (100%), the correlation of the degree of stenosis by the three techniques was poor. This discordance is partly due to the insufficiency of routine DSA to reliably estimate the degree of stenosis since it delivers only one anterior-posterior projection plane. The combination of MRA and TCD is a noninvasive regime of high sensitivity to ensure the diagnosis of MCA stenosis and to estimate the severity of obstruction.