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Metal-dielectric nanolaminates represent a class of hyperbolic metamaterials with uniaxial permittivity tensor. In this study, we critically compare permittivity extraction of nanolaminate samples using two techniques: polarized reflectometry vs. spectroscopic anisotropic ellipsometry. Both Au/MgF2 and Ag/MgF2 metal-dielectric stacks are examined. We demonstrate the applicability of the treatment of the multilayered material as a uniaxial medium and compare the derived optical parameters to those expected from the effective medium approximation. We also experimentally compare the effect of varying the material outer layer on the homogenization of the composite. Additionally, we introduce a simple empirical method of extracting the epsilon-near-zero point of the nanolaminates from normal incidence reflectance. The results of this study are useful in accurate determination of the hyperbolic material permittivity and in the ability to tune its optical properties. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the efficacy of covered stents for the treatment of transjugular intrahepatic portosystemic shunt (TIPS) obstruction in human subjects with identified or suspected biliary fistulae.Methods: Five patients were treated for early failure of TIPS revisions. All had mid-shunt thrombus, and four of these had demonstrable biliary fistulae. Three patients also propagated thrombus into the native portal venous system and required thrombolysis. TIPS were revised in four patients using a custom-made polytetrafluoroethylene (PTFE)-covered Wallstent, and in one patient using a custom-made PTFE-covered Gianturco Z-stent.Results: All identified biliary fistulae were successfully sealed. All five patients maintained patency and function of the TIPS during follow-up ranging from 2 days to 21 months (mean 8.4 months). No patient has required additional revision. Thrombosis of the native portal venous system was treated with partial success by mechanical thrombolysis.Conclusion: Early and recurrent failure of TIPS with mid-shunt thrombosis, which may be associated with biliary fistulae, can be successfully treated using covered stents. Stent-graft revision appears to be safe, effective, and potentially durable. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to characterize the hemodynamics of peripheral artery stent grafts to guide intelligent stent redesign., Materials and Methods: Two surgically explanted porcine arteries were mounted in an ex vivo system with subsequent deployment of an Xpert self-expanding nitinol stent or Viabahn stent graft. The arteries were casted with radiopaque resin, and the cast then scanned using micro-computed tomography at 8μm isotropic voxel resolution. The arterial lumen was segmented and a computational mesh grid surface generated. Computational fluid dynamics (CFD) analysis was subsequently performed using COMSOL Multiphysics 5.1., Results: CFD analysis demonstrated low endothelial shear stress (ESS) involving 9.4 and 63.6% surface area of the central stent graft and bare metal stent, respectively. Recirculation zones were identified adjacent to the bare metal stent struts, while none were identified in the central stent graft. However, the stent graft demonstrated malapposition of the proximal stent graft edge with low velocity flow between the PTFE lining and arterial wall, which was associated with longitudinally and radially oriented recirculation zones and low ESS., Conclusion: Computational hemodynamic analysis demonstrates that peripheral artery stent grafts have a superior central hemodynamic profile compared to bare metal stents. Stents grafts, however, suffer from malapposition at the proximal stent edge which is likely a major contributor to edge stenosis., (Copyright © 2017 Editions françaises de radiologie. Published by Elsevier Masson SAS. All rights reserved.)

Background and Purpose: Patients with arteriovenous malformation (AVM) are known to have an elevated risk of complications with conventional catheter angiography (CCA) but nonetheless require monitoring of hemodynamics. Thus, we aimed to evaluate both anatomy and hemodynamics in patients with AVM noninvasively by using contrast-enhanced MR angiography (CE-MRA) at 3T and to compare the results with CCA., Materials and Methods: Institutional review board approval and informed consent were obtained for this Health Insurance Portability and Accountability Act-compliant study. Twenty control subjects without vascular malformation (6 men, 18-70 years of age) and 10 patients with AVMs (6 men, 20-74 years of age) underwent supra-aortic time-resolved and high-spatial-resolution CE-MRA at 3T. Large-field-of-view coronal acquisitions extending from the root of the aorta to the cranial vertex were obtained for both MRA techniques. Image quality was assessed by 2 specialized radiologists by using a 4-point scale. AVM characteristics and nidus size were evaluated by using both CE-MRA and CCA in all patients., Results: In patients, 96.6% (319/330) of arterial segments on high-spatial-resolution MRA and 87.7% (272/310) of arterial segments on time-resolved MRA were graded excellent/good. MRA showed 100% specificity for detecting feeding arteries and venous drainage (n = 8) and complete obliteration of the AVM in 2 cases (concordance with CCA). Nidus diameters measured by both MRA and CCA resulted in a very strong correlation (r = 0.99) with a mild overestimation by MRA (0.10 cm by using the Bland-Altman plot)., Conclusion: By combining highly temporally resolved and highly spatially resolved MRA at 3T as complementary studies, one can assess vascular anatomy and hemodynamics noninvasively in patients with AVM.

Rationale and Objectives: The purpose of this study was to provide in vivo demonstrations of the functionality of a truly hybrid interventional x-ray/magnetic resonance (MR) system., Materials and Methods: A digital flat-panel x-ray system (1,024(2) array of 200 microm pixels, 30 frames per second) was integrated into an interventional 0.5-T magnet. The hybrid system is capable of MR and x-ray imaging of the same field of view without patient movement. Two intravascular procedures were performed in a 22-kg porcine model: placement of a transjugular intrahepatic portosystemic shunt (TIPS) (x-ray-guided catheterization of the hepatic vein, MR fluoroscopy-guided portal puncture, and x-ray-guided stent placement) and mock chemoembolization (x-ray-guided subselective catheterization of a renal artery branch and MR evaluation of perfused volume)., Results: The resolution and frame rate of the x-ray fluoroscopy images were sufficient to visualize and place devices, including nitinol guidewires (0.016-0.035-inch diameter) and stents and a 2.3-F catheter. Fifth-order branches of the renal artery could be seen. The quality of both real-time (3.5 frames per second) and standard MR images was not affected by the x-ray system. During MR-guided TIPS placement, the trocar and the portal vein could be easily visualized, allowing successful puncture from hepatic to portal vein., Conclusion: Switching back and forth between x-ray and MR imaging modalities without requiring movement of the patient was demonstrated. The integrated nature of the system could be especially beneficial when x-ray and MR image guidance are used iteratively.

Purpose: To compare observer performance in the detection of abnormalities on 1,760 x 2,140 matrix (2K) and 3,520 x 4,280 matrix (4K) digital storage phosphor chest radiographs., Materials and Methods: One hundred sixty patients who underwent dedicated computed tomography (CT) of the thorax were prospectively recruited into the study. Posteroanterior and lateral computed radiographs of the chest were acquired in each patient and printed in 2K and 4K formats. Six radiologists independently analyzed the hard-copy images and scored the presence of parenchymal (opacities 2 cm, and subtle interstitial), mediastinal, and pleural abnormalities on a five-point confidence scale. With CT as the reference standard, observer performance tests were carried out by using receiver operating characteristic (ROC) analysis., Results: Analysis of averaged observer performance showed 2K and 4K images were equally effective in detection of all three groups of abnormalities. In the detection of the three subtypes of parenchymal abnormalities, there were no significant differences in averaged performance between the 2K and 4K formats (area below ROC curve [A(z)] values: opacities 2 cm, 0.86 +/-.025 and 0.85 +/- 0.030; subtle interstitial abnormalities, 0.73 +/- 0.041 and 0.72 +/- 0.041). Averaged performance in detection of mediastinal and pleural abnormalities was equivalent (A(z) values: mediastinal, 0.70 +/- 0.046 and 0.73 +/- 0.033; pleural, 0.85 +/- 0.032 and 0.86 +/- 0.033)., Conclusion: Observer performance in detection of parenchymal, mediastinal, and pleural abnormalities was not significantly different on 2K and 4K storage phosphor chest radiographs.

Purpose: To evaluate the feasibility of endovascular techniques in treating venous outflow obstruction resulting from compression of the iliac vein by the iliac artery of the left lower extremity (May-Thurner syndrome)., Materials and Methods: A retrospective analysis of 39 patients (29 women, 10 men; median age, 46 years) with iliac vein compression syndrome (IVCS) was performed. Nineteen patients presented with acute deep vein thrombosis (DVT) and 20 patients presented with chronic symptoms. All patients presented with leg edema or pain. In the acute group, patients were treated with catheter-directed thrombolysis (120,000-180,000 IU urokinase/h) and angioplasty followed by stent placement. In the chronic group, patients were treated with use of angioplasty and stent placement alone (n = 8), or in combination with thrombolysis (n = 12). Patients were then followed-up with duplex ultrasound and a quality-of-life assessment., Results: Initial technical success was achieved in 34 of 39 patients (87%). The overall patency rate at 1 year was 79%. Symptomatically, 85% of patients were completely or partially improved compared with findings before treatment. Thirty-five of 39 patients received stents. The 1-year patency rate for patients with acute symptoms who received stents was 91.6%; for patients with chronic symptoms who received stents, the 1-year patency rate was 93.9%. Five technical failures occurred. Major complications included acute iliac vein rethrombosis (< 24 hours) requiring reintervention (n = 2). Minor complications included perisheath hematomas (n = 4) and minor bleeding (n = 1). There were no deaths, pulmonary embolus, cerebral hemorrhage, or major bleeding complications., Conclusion: Endovascular reconstruction of occluded iliac veins secondary to IVCS (May-Thurner) appears to be safe and effective.

Purpose: To compare single- versus four-channel helical computed tomographic (CT) aortography., Materials and Methods: Forty-eight patients with aortic aneurysm or dissection underwent four- and one-channel CT angiography. Scan pairs covered the thoracic inlet to the diaphragm (n = 10) and supraceliac abdominal aorta (n = 19) or thoracic inlet (n = 19) to the femoral arterial bifurcations. For four-channel CT, nominal section thickness and pitch were 2.5 mm and 6.0, respectively, and for one-channel CT, 3.0 mm and 2.0 to the infrarenal aorta and 5.0 mm and 2.0 to the femoral arteries. Effective section thickness, scanning duration, scanning coverage, dose of iodinated contrast material, and mean aortoiliac attenuation were compared. Data were summarized as speed (coverage/duration), scanning efficiency (speed/section thickness), and contrast efficiency (mean aortic attenuation/dose of contrast material)., Results: At four- versus one-channel CT, CT angiography was 2.6 times faster, scanning efficiency was 4.1 times greater, contrast efficiency was 2.5 times greater, dose of contrast material was reduced (mean, 57%; 97 vs 232 mL) without a significant change in aortic enhancement, and sections were thinner (mean, 40%; 3.2 vs 5.3 mm) despite a 59% shorter scanning duration (22 vs 56 seconds)., Conclusion: Substantially reduced doses of contrast medium, shorter scanning durations, and narrower effective sections result with four- versus one-channel CT aortography. No advantages of one-channel CT aortography were demonstrated.

Purpose: To evaluate the potential of covered stents to replace surgery in the treatment of subclavian artery aneurysms and traumatic injuries., Materials and Methods: Nine patients (five men, four women; age range, 20-83 years; mean, 54 years) with subclavian artery aneurysms (n = 5) or fistulas (n = 4) were treated with stent-grafts. All devices used were custom-made, consisting of polytetrafluoroethylene (PTFE)-covered Palmaz (n = 5), Wallstent (n = 2), Z stents (n = 8), or a polyester-covered Z stent (n = 1). One patient was lost to follow-up after 2 months. All others were followed up with clinical evaluation, computed tomography (CT), and/or ultrasound., Results: All devices were deployed successfully with exclusion of the aneurysms and fistulas. There were two procedure-related complications (22%), consisting of groin pseudoaneurysms requiring surgical repair 3 and 9 days after the procedure. One of those patients required additional oral antibiotic therapy for a postsurgical groin wound infection. One patient developed a stenosis at 12 months, which required angioplasty. The stent-graft thrombosed in one patient because of a kink 2 months after placement, which was successfully treated by thrombolysis and placement of a Wallstent. The primary and secondary patencies are 89% and 100%, respectively, after a mean follow-up of 29 months (2-66 mo)., Conclusion: Mid-term results of stent-graft therapy of subclavian artery aneurysms and fistulas are encouraging, with low morbidity and excellent clinical outcome.

Purpose: To report the results of endoluminal recanalization and stent placement in patients with chronic occlusions of the inferior vena cava (IVC)., Materials and Methods: Seventeen consecutive patients (12 male, five female patients; mean age, 40.6 years; age range, 15-77 years) with chronic IVC occlusions were treated during a 6-year period. The mean duration of symptoms was 32 months. Underlying active malignancy was the cause of occlusion in four patients. Five patients with superimposed acute thrombus underwent catheter-directed thrombolysis prior to IVC recanalization. Clinical patency was defined as absence or improvement of symptoms. Clinical follow-up was supplemented with ultrasonography, vena cavography, or both in 10 patients., Results: Technical success was achieved in 15 (88%) patients. Additional thrombolytic therapy and stent placement was needed in two patients to maintain patency at 4 and 6 months after the procedure. Twelve patients had IVCs that remained patent after a mean follow-up of 19 months for a primary patency rate of 80%. The primary assisted patency rate was 87% (13 of 15). There were four deaths owing to underlying disease 6-21 months after the procedures. There were no procedure-related complications., Conclusion: Endoluminal recanalization and stent placement in chronically occluded IVCs has a good intermediate-term outcome and should be considered in patients who have symptoms and who often do not have adequate alternative therapy.

Purpose: To compare diagnostic yield and complication rates of magnetic resonance (MR)-guided versus computed tomography (CT)- and ultrasound (US)-guided liver biopsies., Materials and Methods: MR-, CT-, and US-guided liver biopsies performed between 9/96 and 9/98 were compared. Sixty patients (21 men and 39 women, mean age 60 years) underwent MR-guided biopsy of liver lesions. Thirty patients (16 men and 14 women, mean age 59 years) underwent CT-guided biopsy. Eighteen patients (seven men and 11 women, mean age 50 years) underwent US-guided biopsy. MR procedures were performed in an open-configuration 0.5-T Signa SP MR unit. Lesion localization used standard T1 and T2 sequences, whereas biopsies were performed with multiplanar spoiled gradient recalled echo and fast gradient recalled echo sequences. A coaxial system with an MR-compatible 18-gauge stabilizing needle and a 21-gauge aspiration needle was used to obtain all samples. In CT and US procedures, a 19-gauge stabilizing needle and a 21-gauge aspiration or a 20-gauge core biopsy needle were used. A cytotechnologist was present to determine the adequacy of samples., Results: MR had a diagnostic yield of 61%. CT and US had diagnostic yields of 67% and 61%, respectively. No serious complications were reported for MR and US procedures. Two CT biopsies resulted in postprocedural hemorrhage. One patient required surgical exploration and died., Conclusions: MR-guided biopsy of liver lesions with use of a 0.5-T open-configuration magnet is safe and accurate when compared with CT and US. No statistical difference was observed between the diagnostic yield of biopsies performed with MR, CT, and US guidance. MR enabled biopsy of a number of lesions in the hepatic dome and lesions with low contrast, which would normally be difficult to sample safely with use of CT or US.

Airway complications of relapsing polychondritis (RP), including tracheobronchial stenosis, can be fatal. This paper describes a life-saving technique (placement of multiple metallic endobronchial stents under conscious sedation) to prevent life-threatening airway closure in a 50-year-old woman with RP. Using fluoroscopic and bronchoscopic guidance, a tracheal stent and three endobronchial metallic stents were deployed in the central airways, with good functional outcome. There were no complications. In critical airway compromise caused by RP, the insertion of endobronchial stents can result in improved symptoms, pulmonary function, and a return to daily activities, without the use of tracheotomy and mechanical ventilation.

Background: The piggyback technique of orthotopic liver transplantation is an attractive alternative that preserves the recipient inferior vena cava and allows uninterrupted venous blood return during the anhepatic phase. As with other transplantation techniques, the vascular anastomoses required by the piggyback technique can develop strictures., Methods: Review of records of 264 piggyback transplantations revealed two cases of delayed-onset hepatic venous obstruction from anastomotic strictures. Both patients also had symptoms of inferior vena cava obstruction, with azotemia and lower extremity edema. Both patients were treated percutaneously with balloon-expandable stents., Results: Rapid, dramatic resolution of symptoms was achieved in both patients. Patients remain completely asymptomatic at 39 and 3 months of follow-up., Conclusions: Hepatic venous anastomotic strictures in recipients of piggyback technique transplants are a very uncommon complication. They may be easily and effectively treated by minimally invasive endovascular intervention.

Purpose: To evaluate the usefulness of thoracic computed tomography (CT) after placement of an endovascular stent-graft for the treatment of descending thoracic aortic aneurysm., Materials and Methods: From 1992 to 1996, 85 patients with thoracic aortic aneurysm underwent stent-graft placement. In 63 patients, thoracic CT scans were obtained both before and within 10 days after placement. The CT findings were retrospectively studied, and their clinical effect analyzed. In 20 of 63 patients, long-term follow-up CT findings were also evaluated., Results: After stent-graft placement in the 63 patients, CT demonstrated an increase in pleural effusion in 46 (73%), periaortic changes in 21 (33%), perigraft leak in 13 (21%), atelectasis in six (10%), mural thrombus within the stent-graft in two (3%), and new aortic dissection in one (2%). The mean maximum diameter of the aneurysm was 58.8 mm before and 60.0 mm after stent-graft insertion. Sixty-two (98%) patients were successfully treated until discharge. Interventional procedures were performed to eliminate the leakage into the aneurysm sac in 10 patients with perigraft flow depicted at CT. Other complications were managed conservatively., Conclusion: Thoracic CT is useful in the treatment of patients after stent-graft insertion for the management of descending thoracic aortic aneurysm.

Purpose: To report experience with techniques for management of misplaced or migrated endovascular stents., Materials and Methods: During a 5-year period, percutaneous management of 27 misplaced or migrated endovascular stents (16 Palmaz, 11 Wallstents) in 25 patients was attempted. The 17 venous and 10 arterial stents were rescued from the aorta (n = 9), inferior vena cava (IVC) (n = 4), transjugular intrahepatic portosystemic shunt/IVC (n = 2), right atrium (n = 3), right ventricle (n = 2), pulmonary artery (n = 2), iliac vein (n = 2), iliac artery (n = 1), superior vena cava (n = 1), and superior mesenteric vein (n = 1)., Results: Stent management was successful in 26 of 27 cases (96%). Eleven stents were removed percutaneously, two were repositioned and removed with a minor surgical procedure, and 13 were repositioned and deployed in a stable alternate location. The only complication was the development of tricuspid insufficiency in the single case in which the procedure failed (4% complication rate). This patient's stent was eventually surgically removed from the right ventricle., Conclusion: Misplaced or migrated endovascular Palmaz and Wallstents can be effectively managed with few complications by using a variety of percutaneous techniques.

Purpose: To evaluate the performance of portal venous puncture with use of magnetic resonance (MR) guidance, and to place a transjugular intrahepatic portosystemic shunt (TIPS) in a swine model., Materials and Methods: A study of 12 swine was performed to evaluate the ability of interventional MR imaging to guide portal vein puncture and TIPS placement. Six swine had catheters placed in the right hepatic vein under C-arm fluoroscopy. A nitinol guide wire was left in the vein and the animals were then moved into an open configuration MR imaging unit. A TIPS needle set was used to puncture the portal vein using MR fluoroscopy. The animals were transferred to the C-arm, and venography confirmed portal vein puncture. A follow-up study was performed in six additional swine to place a TIPS using only MR imaging guidance. MR tracking was used to advance a catheter from the right atrium into the inferior vena cava. Puncture of the portal vein was performed and a nitinol stent was placed, bridging the hepatic parenchyma. MR venogram confirmed placement., Results: Successful portal vein puncture was achieved in all animals. The number of punctures required decreased from 12 in the first animal to a single puncture in the last eight swine. A stent was successfully placed across the hepatic tract in all six swine., Conclusions: Real-time MR imaging proved to be a feasible method to guide portal vein puncture and TIPS placement in pigs.

Purpose: The authors describe their experience with the use of single-piece, tapered stent-grafts for the treatment of abdominal aortic or aortoiliac aneurysms., Materials and Methods: Single-piece, tapered stent-grafts were placed in 15 patients for the treatment of abdominal aortic aneurysms with small distal necks (n = 13), and aortoiliac aneurysms (n = 2). There were 13 men and two women who ranged in age from 59 to 83 years (mean, 71 years). Usual open surgery was considered high risk in all patients because of comorbid medical conditions. The stent-grafts were made of Z stents covered with polytetrafluoroethylene (PTFE). Additional stent-grafts needed to treat perigraft leaks were made of Z stents covered with woven polyester (n = 5), Wallstents covered with PTFE (n = 2), Z stents covered with PTFE (n = 1), and a PTFE-covered Palmaz stent (n = 1). After stent-graft placement, the contralateral iliac artery was occluded by a blocking device composed of either a PTFE-covered Palmaz (n = 1) or Z stent (n = 13), and a femoral-femoral bypass was created., Results: After placement of the stent-grafts, immediate perigraft leaks were observed in eight patients (53%). These were at the proximal (n = 5) or the distal end (n = 3). All, except one, were treated successfully with additional stent-grafts. The one failure was in a patient who developed aortic rupture after balloon dilation, requiring open surgical repair. Second procedures were required in four patients (27%), including three leaks treated successfully with coil embolization and/or a back-up stent-graft, and one stent-graft migration and thrombosis treated by thrombolysis and placement of an additional stent-graft. One patient died of respiratory failure 23 days after placement of the stent-graft. The mean follow-up was 12 months (range, 4-26 months). On the last follow-up, the aneurysms in the 13 living patients remained thrombosed., Conclusion: Treatment of aortoiliac aneurysms with use of single-piece, tapered stent-grafts is feasible in selected patients. The morbidity and mortality rates compare favorably with those of the open surgical procedures in a high-risk population. Further improvements in the technique and longer follow-up data are needed before this procedure can be recommended for the treatment of all aortoiliac aneurysms.

Purpose: Standard therapy of mycotic aneurysms in the descending aorta consists of thoracotomy and in situ graft placement or extraanatomic bypass. The alternative use of endovascular stent-grafts was evaluated for management of infected aneurysms of the thoracic aorta., Materials and Methods: In a retrospective analysis during a 5-year period, 112 patients underwent stent-graft placement for thoracic aortic aneurysms. Three patients (mean age, 68.6; range, 64-70 years) had mycotic thoracic aneurysms. Stent-grafts were constructed from Z stents covered with polyester fabric and were delivered remotely through a catheter under fluoroscopic guidance., Results: Complete thrombosis of the mycotic aneurysms was achieved in all patients. One patient required a second separate stent-graft placement procedure because of migration of the initial device; the second patient underwent surgical repair of a ruptured mycotic abdominal aortic aneurysm followed immediately by stent-graft placement for a chronic mycotic thoracic aneurysm; a third patient underwent repair of two infected false aneurysms secondary to complete rupture of a surgical interposition graft. There were no complications of persistent bacteremia despite placement of the stent-graft device at the site of primary infection, reinfection, delayed rupture, paraplegia, distal emboli, or surgical conversion. One patient died of cardiac arrest at 25 months; there were no perioperative deaths (< or = 30 days). The remaining two patients were alive and well at median follow-up of 24 months (range, 4-25 months)., Conclusion: Endovascular stent-grafts combined with antibiotic therapy may be an alternative to conventional thoracotomy in managing mycotic aneurysms of the descending thoracic aorta.

Purpose: To describe the use of endovascular stent-grafts to treat acute ruptures of the descending thoracic aorta as an alternative to surgery in high-risk patients., Materials and Methods: From July 1992 to August 1996, 95 patients underwent stent-grafting of the descending thoracic aorta for a variety of lesions. Of these, 11 patients with acute (< or = 7 days) rupture from aneurysms (n = 8) or trauma (n = 3) underwent repair with use of endovascular stent-grafts. Rupture was confirmed with preoperative imaging studies and occurred in the mediastinum (n = 9), the pleural space (n = 1), or the lung (n = 1). All patients were considered high surgical risk due to generalized cardiopulmonary disease and/or previous thoracotomies. Stent-grafts were constructed from Z stents covered with polyester fabric and delivered through a catheter under fluoroscopic control from a remote access site., Results: Stent-graft deployment was successful in all patients. There were no complications of perigraft leak, stent migration, paraplegia, or intraoperative death. Two patients died in the follow-up period: one of ventricular perforation during unrelated thoracic surgery for tumor resection (day 1) and one of cardiac arrest (day 28). All others are alive (mean follow-up, 15.1 months)., Conclusion: For acute rupture of the thoracic aorta, endovascular stent-graft repair is technically feasible and may be a therapeutic alternative to a surgical interposition graft in patients considered high risk for conventional thoracotomy. Long-term studies are necessary to determine the role of stent-grafts in preventing future aortic rupture.

The purpose of the study was to describe the clinical experience is using endoluminal stent-grafts for the treatment of thoracic aortic aneurysms in high-risk patients. Patients with aneurysms of the descending thoracic aorta who were considered high surgical risks underwent evaluation for endoluminal repair. The prosthesis was constructed from Z stents covered with polyester fabric using dimensions based upon preprocedural computed tomography scans and angiography. Through a femoral arteriotomy or left retroperitoneal flank incision, a 22-24 Fr delivery catheter was inserted and advanced through the aorta to the target site under fluoroscopic guidance in the operating suite. The stent-graft prosthesis was deployed at the site of the aneurysm. 44 patients (36 male, 8 female; mean age 36 years) underwent stent-graft repair for thoracic aneurysms (mean diameter 6.3 cm). The deployment was technically successful in all cases, with complete aneurysm thrombosis in 88%. The 30-day perioperative mortality rate was 6.8% and 35-month actuarial survival was 82%. There were no cases of stent migration, surgical conversion or intraprocedural death. Paraplegia occurred in two patients who underwent simultaneous surgical infrarenal aortic aneurysm repair immediately followed by stent-graft placement for a coexisting thoracic aneurysm. The conclusion was that placement of endoluminal stent-grafts for repair of thoracic aortic aneurysms is technically feasible in high-risk patients in whom conventional surgery is contraindicated. Long-term studies are needed to determine protection against aneurysm rupture and patient survival.

Purpose: Our goal was to describe those diseases of the airways that manifest the tree-in-bud (TIB) pattern on CT scan and to establish a differential diagnosis for this CT scan finding., Method: We prospectively collected cases with the TIB pattern on CT and reviewed the scans of patients with histories pertaining to small airway disease. CT scans were performed at 1 to 3 mm collimation., Results: Twenty-six of 27 cases with the TIB pattern had associated bronchiectasis or proximal airway wall thickening. One case with normal proximal airways had an acute aspiration. In addition, we reviewed 141 scans of patients with emphysema, respiratory bronchiolitis (RB), bronchiolitis obliterans (BO), bronchiolitis obliterans organizing pneumonia (BOOP), extrinsic allergic alveolitis (EAA), bronchiectasis, bronchitis, and pneumonia. Of the CT scans with bronchiectasis, 25.6% had TIB, and 17.6% of CT scans with acute infectious bronchitis or pneumonia had this pattern. None of the patients with emphysema, BO, BOOP, EAA, or RB had this pattern., Conclusion: The TIB pattern on CT scan is mostly associated with pulmonary infections that commonly involve the large airways. This pattern was present in 17.6% of cases with acute bronchitis or pneumonia and 25.6% of cases with bronchiectasis.

Rationale and Objectives: We examined whether high-resolution computed tomography (HRCT) would detect and quantify induced airway changes in asthmatic volunteers., Methods: We performed pulmonary function tests and HRCT on eight asthmatic adults and two nonasthmatic control adults under three conditions: baseline, after methacholine inhalation, and after albuterol inhalation. Changes in pulmonary function, airway internal luminal diameter (AILD), and airway wall thickness (AWT) in the three conditions were compared., Results: After methacholine inhalation, pulmonary function showed significant airflow obstruction in the asthmatic volunteers compared with two nonasthmatic control volunteers. The median value for AILD decreased by 17% (p = .04). After subsequent inhalation of albuterol, pulmonary function improved to above the baseline levels in the eight asthmatic volunteers. The median value for AILD increased by 18% above the baseline value (p = .001). No changes in pulmonary function or AILD were seen in the two nonasthmatic volunteers. AWT did not change significantly in either the asthmatic or nonasthmatic volunteers after inhalation of methacholine or albuterol., Conclusion: HRCT can quantify changes in the internal luminal diameter of asthmatic airways provoked by methacholine and albuterol inhalation.

Hydrostatic pulmonary edema can be defined as an abnormal increase in extravascular water secondary to elevated pressure in the pulmonary circulation, as in congestive heart failure or intravascular volume overload. The diagnosis of hydrostatic pulmonary edema is usually based on clinical information, conventional chest radiograph findings, and response to treatment and does not require high-resolution CT. However, recognizing the appearance of hydrostatic pulmonary edema on high-resolution CT can be important, as the edema can mimic other diseases or can occur as an unsuspected finding in patients having high-resolution CT for other indications, and a misdiagnosis may lead to unnecessary lung biopsy. Although the CT appearances of pulmonary edema have been described in several studies [1-3], to date, the high-resolution CT appearances of hydrostatic pulmonary edema have been described only in isolated cases [4-6] or in experimental studies of phantom or animal models [7, 8]. This essay illustrates the spectrum of high-resolution CT findings seen in adult patients with hydrostatic pulmonary edema secondary to cardiac disease.

Pulmonary involvement with Aspergillus fumigatus is varied and largely dependent on the patient's underlying pulmonary and immune status. Hypersensitivity reactions from inhalation of spores can cause acute allergic alveolitis, and bronchial colonization can cause allergic bronchopulmonary aspergillosis (ABPA). The latter is found mainly in patients with asthma or cystic fibrosis. Mycetomas develop from secondary colonization of preexisting lung cavities. Invasive and semi-invasive aspergillosis affect mostly patients with altered immune status. This essay illustrates the radiologic findings of pulmonary aspergillosis and shows the correlation between the imaging and pathologic findings.