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We present a new technique for the design of diffractive optical elements (DOE's) that is based on previous nonlinear least squares (NLS) and phase-shifting quantization methods [Appl. Opt. 36, 7297-7306 (1997)]. The technique uses a memory-matrix-based identification (MMBI) optimization procedure. We compare results from the MMBI method with those from iterative Fourier transform and NLS methods. In comparison, the MMBI DOE designs produce better-quality reconstructions for DOE's with eight or more fabrication phase levels and generally have a higher signal-to-noise ratio and better uniformity.
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PURPOSE: Acetazolamide (ACZ)-enhanced single photon emission computed tomography (SPECT) scans can assess both cerebral perfusion and vascular reactivity. Patients with asymptomatic critical carotid artery stenosis were evaluated for cerebral vascular reactivity to determine the effect of extracranial occlusive disease and the effect of carotid endarterectomy (CEA) on intracerebral reactivity. METHODS: In 44 patients with asymptomatic critical carotid artery stenosis, cerebral perfusion and vascular reactivity were assessed before CEA with resting and ACZ-enhanced SPECT scans. All patients had a 70% or greater ipsilateral internal carotid artery stenosis. Preoperative ACZ-enhanced SPECT scans were obtained, usually 5 days before CEA. Postoperative ACZ-enhanced SPECT scans were obtained in 30 patients. RESULTS: Preoperative SPECT scans were asymmetric, revealing focal (n = 19) or global (n = 15) decreased reactivity in 34 patients (77%). Ten patients had symmetric or normal reactivity. After CEA, 23 patients demonstrated an improvement in reactivity ipsilateral to the side of surgery. The remaining seven patients failed to improve after surgery. CONCLUSION: Although all patients had a high-grade internal carotid stenosis, nearly a quarter of the patients had excellent intracerebral collateral flow. Only 71% of patients demonstrated improved intracerebral vasoreactivity after CEA. The lack of improvement in the other patients may have resulted from intracerebral pathology or lack of improvement in the extracranial carotid hemodynamics.
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Acetazolamida , Estenosis Carotídea/diagnóstico por imagen , Aumento de la Imagen , Tomografía Computarizada de Emisión de Fotón Único , Vasodilatadores , Anciano , Anciano de 80 o más Años , Estenosis Carotídea/cirugía , Circulación Cerebrovascular , Circulación Colateral , Endarterectomía Carotidea , Femenino , Humanos , Masculino , Persona de Mediana Edad , Cuidados Preoperatorios , Estudios RetrospectivosRESUMEN
PURPOSE: Drag reducing polymers (DRPs) have been shown to decrease plaque formation. Their mechanism of action is unknown. Atherosclerosis tends to develop in areas of low shear stress. This study investigates whether DRPs increase shear stress in areas normally exposed to low shear stress. METHODS: Six dogs underwent surgical plication of the left half of the aorta. A specially modified 20-MHz Doppler ultrasound probe mounted at a 45-degree angle on a micromanipulator was used to measure blood flow velocity at six 4-mm intervals along both lateral sides of the aorta starting at the aortic wall and then at subsequent 0.1-mm depths moving into the lumen before and after administering DRP. Shear rates were calculated using linear regression and then compared using the paired t test. The blood viscosity remained constant at 0.04 poise during infusions of this amount of DRP. RESULTS: The maximum shear rate occurring during the cardiac cycle on the side of the aortic stenosis (plication) was 9.96 +/- 1.52/sec before the administration of the DRP and 14.27 +/- 2.01/sec after the administration of the DRP (P =.0240). The maximum shear rate on the side of the unstenosed aortic wall was 57.25 +/- 7.93/sec before the administration of the DRP and 44.80 +/- 6.23/sec after the administration of the DRP (P =. 0081). CONCLUSION: One of the ways that DRPs inhibit the development of atherosclerosis appears to be by increasing shear stress in areas normally exposed to low shear stress. Understanding this mechanism may lead to the development of pharmaceutical agents that inhibit the development of atherosclerosis.
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Arteriosclerosis/prevención & control , Arteriosclerosis/fisiopatología , Polietilenglicoles/uso terapéutico , Polímeros/uso terapéutico , Animales , Fenómenos Biomecánicos , PerrosRESUMEN
The clinical presentation of patients with acute lower-limb ischemia and primary aortic thrombus prompted this review. Following recognition of the first case in early 1994, relevant patients (n = 6) were kept in a database and were reviewed for presentation, treatment, and follow-up. The median age was 41 and five patients were male. Angiography, computed tomography, and/or magnetic resonance angiography demonstrated one or more aortic sessile or pedunculated thrombus(i) without associated atherosclerotic disease. In two cases, a retropancreatic intraaortic mural thrombus was associated with severe pancreatitis. All other cases presented with acute lower-limb emboli requiring limb salvage embolectomy. Because of significant patient illness, systemic anticoagulation was chosen acutely to prevent recurrent emboli. Interestingly, serial studies demonstrated aortic thrombus resolution. Failure to continue warfarin therapy resulted in recurrent problems (n = 1) unless the instigating event had resolved (n = 3). There were no deaths or amputations. We concluded that surgical embolectomy, when required, with subsequent anticoagulation, results in limb salvage and allows for eventual resolution of the primary aortic thrombus. Long-term anticoagulation is required unless the etiologic process resolves. The literature describes patients with atherosclerosis and overlying thrombus but fails to describe the approach to patients with primary thrombus formation.
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Enfermedades de la Aorta , Trombosis , Enfermedad Aguda , Adulto , Anciano , Anticoagulantes/uso terapéutico , Aorta Abdominal , Enfermedades de la Aorta/complicaciones , Enfermedades de la Aorta/diagnóstico , Enfermedades de la Aorta/terapia , Embolectomía , Embolia/etiología , Femenino , Heparina/uso terapéutico , Humanos , Pierna/irrigación sanguínea , Masculino , Pancreatitis/etiología , Trombosis/complicaciones , Trombosis/diagnóstico , Trombosis/terapia , Warfarina/uso terapéuticoRESUMEN
We present an optoelectronic-VLSI system that integrates complementary metal-oxide semiconductor/multiple-quantum-well smart pixels for high-throughput computation and signal processing. The system uses 5 x 10 cellular smart-pixel arrays with intrachip electrical mesh interconnections and interchip optical point-to-point interconnections. Each smart pixel is a fine grain microprocessor that executes binary image algebra instructions. There is one dual-rail optical modulator output and one dual-rail optical detector input in each pixel. These optical input-output arrays provide chip-to-chip optical interconnects. Cascading these smart-pixel array chips permits direct transfer of two-dimensional data or images in parallel. We present laboratory demonstrations of the system for digital image edge detection and digital video motion estimation. We also analyze the performance of the system compared with that of conventional single-instruction-multiple-data processors.
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PURPOSE: We present a review of 35 patients who underwent an operation for subclavian (n = 18) or axillary (n = 17) vessel injury. In some patients, both an artery and a vein were damaged, resulting in a total of 30 arterial and 16 venous injuries. METHODS: The wounding source included a gunshot (n = 19), a stab wound (n = 9,) and blunt trauma (n = 7). Seven patients had hypotension and were taken immediately to the operating room. Seventeen patients had diminished or absent pulses, whereas 13 patients had normal pulses despite an arterial injury. Associated injuries included nerve injury (n = 15), pneumohemothorax (n = 5), and fractures (n = 7). Angiography in 21 patients demonstrated an intimal flap (n = 8), extravasation (n = 5), a pseudoaneurysm (n = 3), an arteriovenous fistula (n = 2), and occlusion (n = 1). Two angiograms were normal. Arterial repair was accomplished by interposition graft (n = 17), primary repair (n = 9), patch angioplasty (n = 3,) and ligation (n = 1). RESULTS: No functional deficits occurred in patients with an isolated vascular injury. Seven patients with associated brachial plexus injuries experienced severe disability. One arm of a patient was amputated. Two patients died. CONCLUSIONS: The use of angiography helps to confirm and localize injuries. Prompt correction of the vascular injury avoids disability resulting from ischemia. Although the amputation rate is low with vascular repair, the functional disability resulting from associated nerve injuries can be devastating.
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Arteria Axilar/lesiones , Vena Axilar/lesiones , Arteria Subclavia/lesiones , Vena Subclavia/lesiones , Traumatismos Torácicos/cirugía , Adolescente , Adulto , Anciano , Amputación Quirúrgica , Aneurisma Falso/etiología , Angiografía , Angioplastia , Brazo/cirugía , Fístula Arteriovenosa/etiología , Arteria Axilar/diagnóstico por imagen , Arteria Axilar/cirugía , Vena Axilar/diagnóstico por imagen , Vena Axilar/cirugía , Implantación de Prótesis Vascular , Plexo Braquial/lesiones , Constricción Patológica/etiología , Femenino , Fracturas Óseas/etiología , Hemoneumotórax/etiología , Humanos , Hipotensión/etiología , Hipotensión/cirugía , Masculino , Persona de Mediana Edad , Pulso Arterial , Arteria Subclavia/diagnóstico por imagen , Arteria Subclavia/cirugía , Vena Subclavia/diagnóstico por imagen , Vena Subclavia/cirugía , Tasa de Supervivencia , Túnica Íntima/lesiones , Heridas por Arma de Fuego/cirugía , Heridas no Penetrantes/cirugía , Heridas Punzantes/cirugíaAsunto(s)
Aneurisma Falso/diagnóstico , Hemangiosarcoma/diagnóstico , Arteria Poplítea/patología , Neoplasias Vasculares/diagnóstico , Anciano , Aneurisma Falso/diagnóstico por imagen , Diagnóstico Diferencial , Hemangiosarcoma/diagnóstico por imagen , Hemangiosarcoma/secundario , Humanos , Imagen por Resonancia Magnética , Masculino , Arteria Poplítea/diagnóstico por imagen , Trombosis/diagnóstico por imagen , Tomografía Computarizada por Rayos X , Ultrasonografía Doppler Dúplex , Neoplasias Vasculares/diagnóstico por imagenRESUMEN
We present a novel algorithm for designing optimal cellular interconnects (OCI's), which can significantly accelerate the communications among processors in single-instruction multiple-data machines with optoelectronic interconnections. We present the foundations of the OCI architecture and show that the optoelectronic OCI is the optimal topology for a space-invariant interconnect pattern. The OCI is optimal in achieving a minimum number of clock cycles per data shift for a given number of optoelectronic links. In addition, our algorithm for designing the OCI is deterministic, whereas previous designs required a trial-and-error procedure.
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PURPOSE: To evaluate the patency and hemodynamic impact of a cryopreserved allograft venous valve transplanted to the superficial femoral vein (SFV) of a canine insufficiency model aided by a distal arteriovenous fistula (dAVF). METHODS: Eight greyhounds had intravenous hemodynamic parameters measured (venous filling time [VFT], 90% of venous refilling time [VRT90], and simulated ambulatory venous pressure [AVP]) before (T0) and after complete hindlimb venous valvulotomy (T1) to produce venous insufficiency. Simultaneously, a valve-containing vein segment was harvested from the opposite SFV or external jugular vein (n = 1) and cryopreserved. Three weeks later a blood type-matched cryopreserved valve was transplanted to the insufficient SFV aided by a low-flow (n = 4) or high-flow (n = 4) dAVF. The fistula was ligated in 3 to 6 weeks, and venous indexes (T2) were obtained 3 weeks later. Analysis of variances compared the venous indexes at T0, T1, and T2 for statistical significance. Gross and histologic inspection assessed valve integrity. RESULTS: Two valves aided by a low-flow dAVF exhibited thrombosis and scarring. The hemodynamics of the six remaining valves demonstrated normalization of the VRT90, an AVP consistent with insufficiency, and a VFT between normal and total venous insufficiency. The patent valves were normal on gross examination and by histologic examination with signs of normal external healing. CONCLUSIONS: A cryopreserved venous valve allograft transplanted to the SFV of an incompetent hindlimb partially corrects venous hemodynamics. A high-flow arteriovenous fistula most consistently preserves transplant patency.
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Derivación Arteriovenosa Quirúrgica , Criopreservación , Venas/trasplante , Insuficiencia Venosa/cirugía , Animales , Velocidad del Flujo Sanguíneo , Perros , Arteria Femoral/cirugía , Vena Femoral/cirugía , Hemodinámica , Flujo Sanguíneo Regional , Trasplante Homólogo , Grado de Desobstrucción Vascular , Insuficiencia Venosa/fisiopatologíaRESUMEN
BACKGROUND AND METHODS: In 64 patients, cerebral perfusion and vascular reactivity were assessed before and after carotid endarterectomy (CEA) using acetazolamide (ACZ)-enhanced single photon emission computer tomography (SPECT). Twenty-five patients were asymptomatic, whereas the remainder were symptomatic. Sixty-one patients had a > or = 70% ipsilateral internal carotid artery stenosis. RESULTS: Fifty SPECT scans revealed decreased vascular reactivity. Twenty-three showed infarcts. Fourteen patients had normal studies. Twenty of the SPECT scans of asymptomatic patients demonstrated poor vascular reactivity. After CEA, 39 patients had improved ipsilateral vasoreactivity. In 12 patients, contralateral improvement was also found. CONCLUSION: ACZ-enhanced SPECT scans, by assessing cerebral perfusion and vascular reactivity, may help to identify patients at risk of stroke should perfusion further diminish. Postoperative studies confirm improvement in vascular reactivity. ACZ-enhanced SPECT scans may provide objective evidence for the selection of patients with a high-grade asymptomatic carotid stenosis for CEA.
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Acetazolamida , Estenosis Carotídea/fisiopatología , Circulación Cerebrovascular , Endarterectomía Carotidea , Radiofármacos , Tomografía Computarizada de Emisión de Fotón Único , Estenosis Carotídea/diagnóstico por imagen , Estenosis Carotídea/cirugía , Humanos , Tomografía Computarizada de Emisión de Fotón Único/métodosRESUMEN
We describe a new approach to suppress undesired diffraction orders in the signal area of a Fourier plane diffractive optical element (DOE). We implement this new approach for the DOE design by a two-stage iterative Fourier transform algorithm that incorporates an adaptive optimization of the signal-to-noise ratio and does not require the introduction of a dummy output area outside the field of view. A comparison among this approach and three other approaches are presented on the basis of numerical results from several sample diffraction patterns.
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BACKGROUND AND OBJECTIVE: This study compares the development of neointimal hyperplasia following conventional and argon ion laser carotid endarterectomy and assesses the potential advantage of endothelial cell seeding. STUDY DESIGN/MATERIALS AND METHODS: Eight dogs underwent conventional endarterectomy in one carotid artery and an argon ion laser endarterectomy in the other. After 42 days, these arteries were harvested and the intimal thickness were compared. Six additional dogs underwent bilateral argon ion laser carotid endarterectomy with endothelial cell seeding on the one side only. These arteries were harvested after 65 days and their mean intimal thickness were compared. RESULTS: At 42 days, the mean intimal thickness in the conventional endarterectomy group was 0.070 +/- 0.007 mm; in the argon ion laser endarterectomy group it was 0.058 +/- 0.001 mm (P = 0.76, NS). At 65 days, the mean intimal thickness in the group without endothelial cell seeding was 0.125 +/- 0.003 mm vs. 0.061 +/- 0.001 mm on the seeded side (P = 0.043). CONCLUSION: Argon ion laser carotid endarterectomy results in no more neointimal hyperplasia than conventional endarterectomy. The neointimal hyperplasia is reduced by endothelial cell seeding.
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Endarterectomía Carotidea/métodos , Endotelio Vascular , Terapia por Láser , Túnica Íntima/patología , Animales , Argón , Perros , Hiperplasia , IonesRESUMEN
A new, to our knowledge, design method for diffractive optical elements (DOE's) is described and compared with existing methods. The technique applies a nonlinear least-squares algorithm to design two-dimensional pure phase DOE's that reconstruct a desired diffraction pattern with high uniformity, efficiency, and signal-to-noise ratio. The technique also uses a phase-shifting quantization procedure that greatly reduces the quantization error for DOE's to a minimum level. In this paper, we compare simulated reconstruction results of DOE's designed by use of these methods with results obtained by the commonly used two-stage iterative Fourier transform design algorithm of Wyrowski. [J. Opt. Soc. Am. A 7, 961, (1990)].
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BACKGROUND: Current experience with carotid body tumors suggesting a high prevalence of associated cervical paragangliomas prompted this review. PATIENTS AND METHODS: An 8-year retrospective study of patients with carotid body tumors was undertaken, detailing presentation, diagnosis, and treatment. RESULTS: Eleven patients harboring 17 carotid body tumors were discovered. All patients had a neck mass. Seven patients (64%) had bilateral carotid body tumors. Six (55%) reported a positive family history-4 were first-generation relatives, 5 had bilateral tumors, and 3 had other head and neck paragangliomas. Angiography documented 4 associated vagal and 2 glomus jugulare paragangliomas in addition to the carotid body tumors. Precise surgical care limited blood loss to an average of 590 cc. The carotid artery was repaired during 5 resections (29%). Cranial nerve injury occurred in 3 cases, all following vagal body or glomus jugulare resection. Every patient is currently alive, stroke free, and functioning without major disability. CONCLUSIONS: Patients with carotid body tumors have a propensity for multiple head and neck paragangliomas. Angiography is diagnostic. The need for associated paraganglioma resection dramatically increases the risk of cranial nerve injury.
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Tumor del Cuerpo Carotídeo/complicaciones , Tumor del Cuerpo Carotídeo/genética , Neoplasias de Cabeza y Cuello/complicaciones , Paraganglioma/complicaciones , Adulto , Angiografía , Tumor del Cuerpo Carotídeo/diagnóstico por imagen , Tumor del Cuerpo Carotídeo/cirugía , Femenino , Neoplasias de Cabeza y Cuello/diagnóstico por imagen , Neoplasias de Cabeza y Cuello/cirugía , Humanos , Incidencia , Masculino , Persona de Mediana Edad , Paraganglioma/diagnóstico por imagen , Paraganglioma/cirugía , Linaje , Resultado del TratamientoRESUMEN
PURPOSE: To determine the accuracy of two-dimensional (2D) time-of-flight (TOF) magnetic resonance (MR) angiography, performed with state-of-the-art equipment, in the evaluation of the iliac arteries. MATERIALS AND METHODS: The iliac arteries of 50 patients undergoing conventional arteriography for evaluation of lower-extremity ischemia or abdominal aortic aneurysm were also imaged with axial 2D TOF MR angiography. Blinded interpretations of conventional arteriograms and MR angiograms were compared. MR angiography was performed with a 1.5-T system with 2-mm contiguous axial sections, 60 degrees flip angle, 28-msec repetition time, and 7.4-msec echo time. RESULTS: Blinded interpretations of 2D TOF MR angiograms matched those of conventional arteriograms in 26 of 50 patients (52%). For the diagnosis of obstructive iliac artery lesions, sensitivity and specificity with MR angiography were 85% and 59%, respectively. Two of three saccular iliac artery aneurysms escaped detection with MR angiography. CONCLUSION: Iliac artery evaluation with axial 2D TOF MR angiography is not sufficiently accurate to warrant its use as a replacement for conventional arteriography in patients who lack contraindications to the latter.
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Arteriopatías Oclusivas/diagnóstico , Aneurisma Ilíaco/diagnóstico , Arteria Ilíaca/patología , Angiografía por Resonancia Magnética/métodos , Angiografía , Aneurisma de la Aorta Abdominal/diagnóstico por imagen , Arteriopatías Oclusivas/diagnóstico por imagen , Humanos , Aneurisma Ilíaco/diagnóstico por imagen , Isquemia/diagnóstico por imagen , Pierna/irrigación sanguínea , Persona de Mediana Edad , Sensibilidad y EspecificidadRESUMEN
Renal and visceral artery images obtained concurrently with spiral CT and conventional arteriography were compared for 32 patients. Indications for imaging were occlusive disease (n = 12), aneurysmal disease (n = 9), and renal or visceral artery disease (n = 11). Conventional arteriography enabled visualization of 64 renal arteries and 15 accessory renal arteries. Lateral aortograms obtained in 15 patients enabled visualization of 14 superior mesenteric (SMA) and 14 celiac arteries. Spiral CT enabled visualization of 60 renal arteries, 12 accessory renal arteries, 27 SMAs, and 22 celiac arteries. Calcification or a disparity in timing of contrast material injection and scanning prevented visualization of the celiac artery in 10 patients and the SMA in four patients. With conventional arteriography as the standard for comparison, spiral CT had a sensitivity of 67% and a specificity of 95% for depiction of at least 75% stenosis in the main renal artery. By means of the Pearson correlation coefficient, significant correlation (p < 0.001) was confirmed between spiral CT and arteriography for evaluation of stenosis of the main renal artery, SMA, and celiac artery. This early experience suggests that spiral CT may be useful in evaluation of renal and visceral arteries and their relationship to aortic disease.
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Angiografía , Arteria Celíaca/diagnóstico por imagen , Arteria Mesentérica Superior/diagnóstico por imagen , Arteria Renal/diagnóstico por imagen , Tomografía Computarizada por Rayos X/métodos , Adulto , Anciano , Anciano de 80 o más Años , Aneurisma/diagnóstico por imagen , Enfermedades de la Aorta/diagnóstico por imagen , Aortografía , Arteriopatías Oclusivas/diagnóstico por imagen , Calcinosis/diagnóstico por imagen , Constricción Patológica/diagnóstico por imagen , Medios de Contraste/administración & dosificación , Femenino , Humanos , Aumento de la Imagen/métodos , Masculino , Persona de Mediana Edad , Obstrucción de la Arteria Renal/diagnóstico por imagen , Sensibilidad y Especificidad , Enfermedades Vasculares/diagnóstico por imagenRESUMEN
We discuss the cellular-hypercube optical free-space interconnection architecture and its implementation by two-dimensional smart-pixel optoelectronic cellular arrays. We emphasize the behavior of the cellular hypercube in performing shift-invariant parallel shifts of data, a basic requirement of most single-instruction multiple-data algorithms. We present a time-multiplexing scheme for realizing the cellular hypercube, showing that the communication time is inversely proportional to the number of optical detectors per cell. We also present an improved hybrid interconnection network with improved performance that combines the cellular hypercube and mesh, using optics for the longer-distance connections and electronics for nearest-neighbor connections.
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BACKGROUND: Thirty-eight limbs with iliac occlusive disease were treated with Palmaz stents from 1987 through 1991. METHODS: Indications for stent utilization included dissection induced by percutaneous transluminal balloon angioplasty (PTA) (10), restenosis after PTA (nine), post-PTA residual stenosis (nine), multiple stenoses or occlusion (five), and unfavorable location (five). RESULTS: The ankle/brachial pressure index increased from 0.53 +/- 0.27 to 0.8 +/- 0.26 after stent deployment. The intraluminal pressure gradient decreased from 31.9 +/- 16.3 to 0.9 +/- 2.2 mm Hg after stent deployment. Complications included pseudoaneurysm (one), arteriovenous fistula (one), iliac perforation (one), groin hematoma (two), and occlusion (two). Follow-up arteriogram showed stenosis proximal or distal (n = 4) or within the stents (n = 4). These were treated with PTA or stents. Two patients required an aortobifemoral graft. Nine patients have died. Life table analysis showed a 1-, 3-, and 5-year primary and secondary cumulative patency of 87% +/- 5.9%, 74% +/- 8.2%, and 63% +/- 10% and 91% +/- 5.1%, 91% +/- 5.6%, and 86% +/- 7.6%, respectively. CONCLUSIONS: Palmaz stents, often required to salvage a PTA failure, appear to maintain overall patency at a high level. However, intimal hyperplasia and the progression of atherosclerotic disease may result in a need for additional procedures to obtain this favorable outcome.
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Arteriopatías Oclusivas/cirugía , Arteria Ilíaca/cirugía , Stents , Adulto , Anciano , Angioplastia de Balón/efectos adversos , Diseño de Equipo , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Fumar , Stents/efectos adversos , Resultado del TratamientoRESUMEN
PURPOSE: To determine if a three-dimensional (3D) gadolinium-enhanced technique is useful for improving the accuracy of magnetic resonance (MR) angiography. MATERIALS AND METHODS: Prospectively, two-dimensional (2D) time-of-flight (TOF) and 3D gadolinium-enhanced MR angiography was performed in 23 patients. Conventional arteriography, the reference standard, was performed in all but five patients. Images from each examination were interpreted blindly by two observers. RESULTS: For common and external iliac arteries, interpretations of dynamic 3D gadolinium-enhanced MR angiograms matched those of conventional arteriograms in 12 of 18 patients (67%) for both observers. Interpretations of 2D TOF images matched those of conventional arteriograms in six (33%) and seven (39%) patients for the two observers respectively. CONCLUSION: Preliminary results suggest that iliac artery MR angiography can be improved by complementing standard 2D TOF acquisitions with 3D gadolinium-enhanced acquisitions.