Conventional X-ray Angiography Research Articles

Automated analysis method to assess pulmonary blood flow distribution using conventional X-ray angiography

Quantitative assessment of the right-to-left ratio of pulmonary blood flow distribution is important for determining the clinical indications for treating pulmonary arterial branch stenosis. A novel theory was recently proposed that can be used to quantitatively assess the right-to-left ratio on conventional X-ray angiography images. In the proposal, further developments were indicated, especially automated calculation. In this study, a new automated algorithm was developed. In the X-ray image, regions of interest were set in right and left lung, and time-signal intensity curves were measured. The new automated algorithm is applied to determine the optimal time window for the analysis of the time-signal intensity curve and to calculate the slope of the curve in the optimized time window. The right-to-left ratios in seven consecutive patients calculated by the new automated algorithm were compared to those calculated by lung perfusion scintigraphy. The ratios were in good agreement with linear regression with a slope of 1.27 and a Pearson correlation coefficient of 0.95. The processing time was less than 10 s, which is one-eighth of the manual processing time. The new automated algorithm is accurate, stable, and fast enough for clinical use in the real world.

Radiological equipment and accessories as sources of nosocomial infection

Background: Nosocomial infections have become a major challenge in health institutions, as they affect the quality of health care delivered. The radiology department is one of the mainstays of modern medicine. It is therefore, necessary to assess its contamination by nosocomial organisms.Aim: The study aims at identifying the nosocomial bacteria associated with imaging equipment and accessories in Aminu Kano Teaching Hospital, Kano, Nigeria.Methods: The study design was prospective and cross-sectional in nature, and was conducted between Oct 2014 to Jan 2015 using disproportionate stratified random sampling method. Four different conventional x-ray units, fluoroscopy, computed tomography, angiography and ultrasound units were selected. Swabs were collected from the surfaces of the selected parts of the equipment and accessories after working hours in each unit. The swabs were taken to the microbiology laboratory for culturing and identification using standard laboratory procedure. A total of 200 cultured samples were used in the study. The collected data was analyzed using SPSS version 16.0 software.Results: Bacteria were isolated in 43.5 % (n = 87) of all the swab samples with ultrasound transducer as major culture. Specific bacteria isolated were: Staphylococcus aureus (n = 65; 74.7 %), Pseudomonas aeruginosa (n = 14; 16.1 %), Bacillus spp (n = 6; 6.9 %), Klebsiella spp (n = 1; 1.1 %) and Proteus spp (n = 1; 1.1 %). Methylated spirit was the most effective chemical disinfectant. Conclusion: Radiology equipment and accessories in Aminu Kano Teaching Hospital are not entirely free of bacteria. Meticulous attention to disinfection will safeguard staff and other patients from nosocomial infections.

Three-dimensional reconstruction and NURBS-based structured meshing of coronary arteries from the conventional X-ray angiography projection images

Despite its two-dimensional nature, X-ray angiography (XRA) has served as the gold standard imaging technique in the interventional cardiology for over five decades. Accordingly, demands for tools that could increase efficiency of the XRA procedure for the quantitative analysis of coronary arteries (CA) are constantly increasing. The aim of this study was to propose a novel procedure for three-dimensional modeling of CA from uncalibrated XRA projections. A comprehensive mathematical model of the image formation was developed and used with a robust genetic algorithm optimizer to determine the calibration parameters across XRA views. The frames correspondences between XRA acquisitions were found using a partial-matching approach. Using the same matching method, an efficient procedure for vessel centerline reconstruction was developed. Finally, the problem of meshing complex CA trees was simplified to independent reconstruction and meshing of connected branches using the proposed nonuniform rational B-spline (NURBS)-based method. Because it enables structured quadrilateral and hexahedral meshing, our method is suitable for the subsequent computational modelling of CA physiology (i.e. coronary blood flow, fractional flow reverse, virtual stenting and plaque progression). Extensive validations using digital, physical, and clinical datasets showed competitive performances and potential for further application on a wider scale.

Potential of 80-kV high-resolution cone-beam CT imaging combined with an optimized protocol for neurological surgery.

With the development of computed tomography (CT) and magnetic resonance imaging (MRI), the use of conventional X-ray angiography including digital subtraction angiography (DSA) for diagnosis has decreased, as it is an invasive technique with a risk of neurological complications. However, X-ray angiography imaging technologies have progressed markedly, along with the development of endovascular treatments. A newly developed angiography technique using cone-beam CT (CBCT) technology provides higher spatial resolution than conventional CT. Herein, we describe the potential of this technology for neurosurgical operations with reference to clinical cases. Two hundred twenty-five patients who received 80-kV high-resolution CBCT from July 2011 to June 2014 for preoperative examinations were included in this study. For pathognomonical cases, images were taken with suitable reconstruction modes and contrast protocols. Cases were compared with intraoperative findings or images from other modalities. We observed the following pathognomonical types: (1) imaging of the distal dural ring (DDR) and the surrounding structure for paraclinoid aneurysms, (2) imaging of thin blood vessels, and (3) imaging of both brain tumors and their surrounding anatomy. Our devised 80-kV high-resolution CBCT imaging system provided clear visualization of detailed anatomy when compared with other modalities in almost all cases. Only two cases provided poor visualization due to movement artifact. Eighty-kilovolt high-resolution CBCT has the potential to provide detailed anatomy for neurosurgical operations when utilizing suitable modes and contrast protocols.

Is MRI the Preferred Method for Evaluating Right Ventricular Size and Function in Patients With Congenital Heart Disease?

In contrast to adult patients with acquired heart disease, abnormalities of the right ventricle (RV) are ubiquitous in children and adults with congenital heart disease (CHD). The RV is exposed to volume overload in shunt lesions (eg, atrial septal defect, anomalous pulmonary venous connections), as well as congenital or acquired tricuspid and pulmonary valve regurgitation. RV pressure overload characterizes numerous congenital anomalies, including pulmonary valve stenosis or atresia, large ventricular septal defect, single ventricle, tetralogy of Fallot (TOF), truncus arteriosus, and transposition of the great arteries, to name a few. Importantly, many surgical and transcatheter treatments of CHD result in persistent or acquired volume and pressure overload of the RV. In some patients with CHD, the RV functions as the systemic ventricle (eg, palliated hypoplastic left heart syndrome, physiologically corrected transposition of the great arteries, and D-loop transposition of the great arteries after atrial switch procedure). Furthermore, exposure to cyanosis and surgical procedures in the RV often leads to myocardial abnormalities, including scar tissue and diffuse fibrosis. Response by Yeh and Foster see p 197 Given the frequent involvement of the RV in CHD, it is not surprising that the assessment of RV size and function is key for guiding clinical decisions in these patients.1 Among the diagnostic imaging tools available to clinicians for RV imaging, cardiac magnetic resonance (CMR) has emerged as the reference standard. In the following sections, I will review the evidence supporting this contention, highlight how CMR data are used to guide clinical decisions, and discuss the strengths and weaknesses of CMR in comparison with other modalities, including echocardiography, computed tomography, conventional x-ray angiography, and nuclear scintigraphy. CMR is ideally suited for the assessment of the RV because it allows comprehensive assessment of cardiovascular morphology and physiology without most of the limitations that hinder alternative …

Contrast-enhanced peripheral MRA: technique and contrast agents

In the last decade contrast-enhanced magnetic resonance angiography (CE-MRA) has gained wide acceptance as a valuable tool in the diagnostic work-up of patients with peripheral arterial disease. This review presents current concepts in peripheral CE-MRA with emphasis on MRI technique and contrast agents. Peripheral CE-MRA is defined as an MR angiogram of the arteries from the aortic bifurcation to the feet. Advantages of CE-MRA include minimal invasiveness and lack of ionizing radiation. The basic technique employed for peripheral CE-MRA is the bolus-chase method. With this method a paramagnetic MRI contrast agent is injected intravenously and T1-weighted images are acquired in the subsequent arterial first-pass phase. In order to achieve high quality MR angiograms without interfering venous contamination or artifacts, a number of factors need to be taken into account. This includes magnetic field strength of the MRI system, receiver coil configuration, use of parallel imaging, contrast bolus timing technique, and k-space filling strategies. Furthermore, it is possible to optimize peripheral CE-MRA using venous compression techniques, hybrid scan protocols, time-resolved imaging, and steady-state MRA. Gadolinium(Gd)-based contrast agents are used for CE-MRA of the peripheral arteries. Extracellular Gd agents have a pharmacokinetic profile similar to iodinated contrast media. Accordingly, these agents are employed for first-pass MRA. Blood-pool Gd-based agents are characterized by prolonged intravascular stay, due to macromolecular structure or protein binding. These agents can be used for first-pass, as well as steady-state MRA. Some Gd-based contrast agents with low thermodynamic stability have been linked to development of nephrogenic systemic fibrosis in patients with severe renal insufficiency. Using optimized technique and a stable MRI contrast agent, peripheral CE-MRA is a safe procedure with diagnostic accuracy close to that of conventional catheter X-ray angiography.

Imagerie stéréotaxique et diagnostique en radiochirurgie

Constant progress in medical imaging and particularly magnetic resonance imaging has profound impact in planning for stereotactic radiosurgery and radiotherapy. The purpose of this paper is to discuss the integration of medical imaging modalities in the planning process. Principles of generic algorithms to calculate stereotactic coordinates are treated for tomographic imaging and digital substraction angiography, and their accuracies are analyzed in a review of the literature. The algorithmic foundations and performance of automatic intermodality co-registration methods are developed. Finally, the MRI sequences useful in planning and follow-up are discussed and the role of MR angiographic sequences compared to conventional X-ray angiography in the particular case of the arteriovenous malformation planning.

X-ray phase contrast for CO2 microangiography

We demonstrate a laboratory method for imaging small blood vessels using x-ray propagation-based phase-contrast imaging and carbon dioxide (CO2) gas as a contrast agent. The limited radiation dose in combination with CO2 being clinically acceptable makes the method promising for small-diameter vascular visualization. We investigate the possibilities and limitations of the method for small-animal angiography and compare it with conventional absorption-based x-ray angiography. Photon noise in absorption-contrast imaging prevents visualization of blood vessels narrower than 50 µm at the highest radiation doses compatible with living animals, whereas our simulations and experiments indicate the possibility of visualizing 20 µm vessels at radiation doses as low as 100 mGy. Experimental computed tomography of excised rat kidney shows blood vessels of diameters down to 60 µm with improved image quality compared to absorption-based methods. With our present prototype x-ray source, the acquisition time for a tomographic dataset is approximately 1 h, which is long compared to the 1–20 min common for absorption-contrast micro-CT systems. Further development of the liquid-metal-jet microfocus x-ray sources used here and high-resolution x-ray detectors shows promise to reduce exposure times and make this high-resolution method practical for imaging of living animals.

Visualization of microvasculature by x-ray in-line phase contrast imaging in rat spinal cord

Computed tomography combined with angiography has recently been developed to visualize three-dimensional (3D) vascular structure in experi-mental and clinical studies. However, there remain difficulties in using conventional x-ray angiography to detect small vessels with a diameter less than 200 µm. This study attempted to develop a novel method for visualizing the micro-angioarchitecture of rat spinal cord. Herein, synchrotron radiation-based x-ray in-line phase contrast computed tomography (IL-XPCT) was used to obtain 3D micro-vessel structure without angiography. The digital phase contrast images were compared with conventional histological sections. Our results clearly demonstrated that the resolution limit of the spatial blood supply network in the normal rat thoracic cord appeared to be as small as ∼10 µm. The rendered images were consistent with that obtained from histo-morphology sections. In summary, IL-XPCT is a potential tool to investigate the 3D neurovascular morphology of the rat spinal cord without the use of contrast agents, and it could help to evaluate the validity of the pro- or anti-angiogenesis therapeutic strategies on microvasculature repair or regeneration.

Imaging of angiogenesis: from morphology to molecules and from bench to bedside

Angiogenesis is one of the hallmarks of cancer and is increasingly in the focus of oncological research. Judah Folkman first articulated the importance of angiogenesis for tumor growth in 1971 [1]. He stated that the growth of solid tumors remains restricted to 2–3 mm in diameter until the onset of angiogenesis. Although this hypothesis first was strongly criticized, angiogenesis soon became one of the most important fields of research in oncology. Up to now, subsequent investigations have identified more than 20 angiogenic growth factors, their receptors and signal transduction pathways. Moreover, endogenous angiogenesis inhibitors have been discovered, and the cellular and molecular characterization of the angiogenic phenotype in human cancers has been achieved [2, 3]. Although the results of the first clinical trials using angiogenesis inhibitors in oncology were disappointing, encouraging results have been achieved in the past few years with the vascular endothelial growth factor (VEGF) antibody Avastin® in combination with standard cytotoxic chemotherapy. This combined antiangiogenic-cytotoxic therapy has been proven to be successful first in metastasized colorectal cancer, and subsequently also in breast cancer and non-small cell lung cancer [4–7]. This success of targeted antiangiogenic therapy will spur the demand for imaging modalities for assessment of the angiogenic cascade, which is the topic of this supplement “Imaging of Angiogenesis.” Imaging of angiogenic activity might on the one hand help in the process of developing novel antiangiogenic drugs in the preclinical setting. Moreover, in the clinical setting, imaging of angiogenesis might be useful for assessment of the optimum dose of new antiangiogenic agents and for early response evaluation. Up to now, clinical trials with conventional cytotoxic chemotherapeutic agents have mainly used morphological imaging to provide indices of therapeutic response, mostly computed tomography (CT) or magnetic resonance imaging (MRI). Bidimensional measurements of the maximum tumor extension are mainly used to estimate changes in response to the investigational therapy as compared with a baseline measure. Through standardization of these measurements by introducing the RECIST criteria in the year 2000, considerable progress has been achieved [8]. However, as antiangiogenic agents lead to a stop of tumor progression rather than to tumor shrinkage, the approach of measuring tumor response by a reduction of tumor size is not applicable and might take months or years to become apparent. Therefore, there is great interest in identifying reliable biomarkers of early tumor response to non-cytotoxic drugs [9]. Imaging techniques could potentially be used as such a biomarker and could provide an early indicator of effectiveness at a functional or molecular level. Concerning morphological imaging of the vasculature, conventional X-ray angiography and digital subtraction angiography (DSA) are widely used in the clinical arena; however, they do not allow for assessment of the microvasculature and thus are not commonly used for response evaluation of antiangiogenic therapies. More promising is the assessment of changes in hemodynamic parameters such as blood flow, blood volume, or vessel permeability. They may be effective biomarkers for response evaluation, because antiangiogenic therapies are designed to affect the abnormal blood vessels found in tumors. Current clinical trials employ various imaging techniques for this purpose, mostly dynamic contrast-enhanced MRI (DCE MRI), and less often ultrasound, PET (especially with [15O] water), and dynamic contrast-enhanced CT (DCE CT) [10]. In the future, targeting specific molecular markers of angiogenesis might also be used for response assessment of antiangiogenic therapies like the VEGF pathway or cell surface markers like the integrin αvβ3.

Correlation between cardiac catheterization and contrast enhanced MRI in pulmonary artery stenosis

Introduction Peripheral pulmonary artery stenosis (PPAS) is present in 2-3% of all congenital heart defects. Catheter interventions guided by conventional X-ray angiography (XRA) have replaced cardiac surgery in the management of PPAS. However, X-ray exposure has negative health effects. Interventional XRA would benefit from non-ionizing and noninvasive planning using contrast enhanced magnetic resonance imaging (CE-MRI) due to its multi-planar capability, but the correlation of images in the two modalities is not always perfect, possibly due to different projections or time delays in capture.

Pre-Procedural Imaging of Aortic Root Orientation and Dimensions: Comparison Between X-Ray Angiographic Planar Imaging and 3-Dimensional Multidetector Row Computed Tomography

We sought to examine whether contrast-enhanced multidetector row computed tomography (MDCT) allows prediction of X-ray angiographic planes for the root angiogram in the context of transcatheter aortic valve implantation. Understanding of aortic root orientation relative to the body axis is critical for precise positioning of the stent/valve during transcatheter aortic valve implantation. Forty patients with severe aortic stenosis underwent conventional X-ray angiography and contrast-enhanced MDCT of the aortic root. Oblique MDCT images of the aortic root, corresponding to X-ray angiographic left anterior oblique (LA)/right anterior oblique (RAO) projections, were created. The cranial/caudal angulation was compared between angiographic and reformatted MDCT images. In addition, root diameter measurements were compared. The cranial angulation in the LAO X-ray angiograms (mean LAO: 39+/- 8, n = 38) and matched MDCT images were not significantly different (cranial: 25 +/- 7 vs. 23 +/- 8; p = 0.214). There was a small but significant difference between the caudal angulation in the RAO angiogram (mean RAO: 25 +/- 5, n = 40) and matched CT images (caudal: 21 +/- 9 vs. 29 +/- 10; p = 0.002). The annulus diameter in the LAO projection was not significantly different between X-ray angiography and contrast-enhanced MDCT (2.3 +/- 0.3 vs. 2.4 +/- 0.3; p = 0.052), whereas there was a small but significant difference in the annulus diameter in RAO projections between angiography and MDCT (2.4 +/- 0.3 vs. 2.2 +/- 0.3; p = 0.029). Pre-procedural contrast-enhanced MDCT imaging of the aortic root allows prediction of X-ray angiographic planes and contributes to planning of the transcatheter aortic valve implantation.

Ultra-Low-Dose Intra-Arterial Contrast Injection for Iliofemoral Computed Tomographic Angiography

This study sought to evaluate the feasibility of using ultra-low-dose intra-arterial contrast injection for iliofemoral computed tomographic (CT) angiography to follow diagnostic cardiac catheterization. Cardiovascular interventions such as percutaneous aortic valve replacement require transfemoral delivery of large-bore intra-arterial catheters; therefore, pre-procedural assessment of aortoiliofemoral anatomy is important. CT angiography is ideal for this purpose but requires a large volume of intravenous contrast. Consecutive patients requiring evaluation of aortoiliofemoral anatomy underwent conventional anteroposterior projection iliac angiography during cardiac catheterization. A pigtail catheter was left in situ in the infrarenal abdominal aorta, and patients were transferred to the CT suite. Subsequently, 10 to 15 ml of contrast diluted with normal saline was injected intra-arterially via the pigtail catheter while a spiral CT of the abdomen and pelvis was acquired. Conventional angiographic and CT images were analyzed independently to assess suitability for large-bore (7-mm-diameter)intra-arterial catheter access. Excellent CT image quality was achieved in 34 of 37 patients (92%). The mean contrast dose for CT was 12 +/- 2 ml. In 9 patients (24%), CT changed the assessment of femoral access feasibility. Furthermore, in another 7 patients (19%), unfavorable anatomy as shown by CT directed the avoidance of a particular side. Overall, CT findings altered the interventional approach in 16 patients (43%). There was no significant deterioration detected in renal function after coronary and CT angiography (estimated glomerular filtration rate 54.8 +/- 3.8 ml/min before 53.3 +/- 3.9 ml/min after, p = 0.55). High-quality aortoiliofemoral CT angiography can be obtained with a technical success rate of >90% using 10 to 15 ml of contrast injected via a catheter in the abdominal aorta, and offers an alternative to conventional X-ray or CT angiography with high-volume intravenous contrast injection.

High field strength coronary MRA—ready for prime time?

Yang and colleagues report on their single-center experience with high-field coronary MRA using a new MR contrast agent. Data on 30 patients were compared with conventional X-ray angiography. Their new coronary MRA approach seems favourable when compared with previous MRA methods.

Image-Guided Perforator Flap Design Using Invisible Near-Infrared Light and Validation With X-Ray Angiography

Although perforator flaps mark an important conceptual change in reconstructive surgery, individual perforator vessels show a high degree of variability with respect to anatomic landmarks. We have developed an intraoperative imaging system that simultaneously displays surgical anatomy and otherwise invisible near-infrared images. In 22 adult pigs, perforating vessels were identified within seconds using this optical imaging system and systemic injection of indocyanine green. Perforator flaps were then designed based on these results, and vessel location confirmed by direct visualization and anatomic dissection. Since x-ray angiography remains the gold standard for identification of underlying vessels, conventional x-ray angiography was also performed in 8 pigs to verify the location of perforators. There was full correlation of all the perforators identified among near-infrared fluorescence angiography, x-ray angiography, and anatomic dissection. The technology we describe provides high-sensitivity real-time image guidance throughout perforator dissection, and permits patient-specific flap design.

Distortion Correction and Geometric Calibration for X-Ray Angiography System

Based on the knowledge that distortion is the result of pixel movement, a distortion correction method is developed by analyzing the principle of distortion change with imaging orientation, which can be used to correct the imaging distortion of a conventional X-ray angiography (XRA) system with an image intensifier. Distortion at any arbitrary imaging orientation can be corrected by integrating the movement model of every single pixel. Experiments show that the method is fast with subpixel accuracy. Meanwhile, for achieving the geometric calibration for the XRA imaging system, we propose a novel method with the kernel of a C-arm movement model which represents C-arm movement without any assumption for simplification purposes. Then extended models with high flexibility are obtained by taking into account the influence of C-arm movement on intrinsic parameters, which are applicable even for the situation with varying source-intensifier distance. Experiments demonstrate that the proposed method can be used to calculate the accurate imaging parameters, including intrinsic and extrinsic parameters.

Contrast-enhanced magnetic resonance angiography (CE-MRA) of intra- and extra-cranial vessels in dogs

Until recently intra- and extra-cranial vessels in dogs have been imaged using conventional X-ray or digital subtraction angiography. As both of these methods are surgically demanding and involve the use of complex equipment with potential risks for the animal, they are now mainly used in experimental work. In this study, a method for delineating the intra- and extra-cranial vessels of dogs using contrast-enhanced magnetic resonance angiography (CE-MRA) has been examined. The MR images were acquired on a 1.5-T scanner after a bolus injection of gadolinium contrast medium. CE-MRA showed most of the major intra- and extra-cranial arteries and veins as well as most venous sinuses and plexuses of the brain. Difficulties may arise in differentiating between minor arterial and venous vessels as well as in the measurement of vessel diameter. More frequent use of this diagnostic method in clinical cases will indicate whether MRA of the head and brain is of as much use in veterinary medicine as it has become in human medicine. There is certainly potential value in detecting rare conditions in animals such as aneurysms and vascular malformations, as well as in examining vessels feeding intracranial masses and the investigation of cerebrovascular accidents.

Hind Limb Ischemia in Rabbit Model: T2-prepared versus Time-of-Flight MR Angiography at 3 T

To prospectively compare various parameters of vessels imaged at 3 T by using time-of-flight (TOF) and T2-prepared magnetic resonance (MR) angiography in a rabbit model of hind limb ischemia. Experiments were approved by the institutional animal care and use committee. Endovascular occlusion of the left superficial femoral artery was induced in 14 New Zealand white rabbits. After 2 weeks, MR angiography and conventional (x-ray) angiography were performed. Vessel sharpness was evaluated visually in the ischemic and nonischemic limbs, and the presence of small collateral vessels was evaluated in the ischemic limbs. Vessel sharpness was also quantified by evaluating the magnitude of signal intensity change at the vessel borders. The sharpness of vessels in the nonischemic limbs was similar between the TOF and the T2-prepared images. In the ischemic limbs, however, T2-prepared imaging, as compared with TOF imaging, generated higher vessel sharpness in arteries with diminished blood flow (mean vessel sharpness: 44% vs 30% for popliteal arteries, 45% vs 28% for saphenous arteries; P < .001 for both comparisons) and enabled better detection of small collateral vessels (93% vs 36% of vessels, P < .001). T2-prepared imaging can facilitate high-spatial-resolution MR angiography of small vessels with low blood flow and thus has potential as a tool for noninvasive evaluation of arteriogenic therapies, without use of contrast material. http://radiology.rsnajnls.org/cgi/content/full/2452062067/DC1.

Assessment of Vasculature of Meningiomas and the Effects of Embolization with Intra-arterial MR Perfusion Imaging: A Feasibility Study

Embolization of meningiomas has emerged as a preoperative adjuvant therapy that has proved effective in mitigating blood loss during surgical resection. Arterial supply to these tumors is typically identified by diffuse areas of parenchymal staining after selective x-ray angiograms. We investigate the benefits that selective injection of MR contrast may have in identifying vascular territories and determining the effects of embolization therapy. Selective intra-arterial (IA) injection of dilute MR contrast media was used to assess the vascular distribution territories of meningeal tumors before and after embolization therapy. Regions of the tumor that experienced loss of signal intensity after localized contrast injections into the external and common carotid as well as vertebral arteries were used to quantify the specific vessel's volume of distribution. Assessments were made before and after embolization to reveal changes in the vascular supply of the tumor. MR findings were compared with radiographic evaluation of tumor vascular supply on the basis of conventional x-ray angiography. MR proved to be an excellent means to assess tissue fed by selected arteries and clearly demonstrated the treated and untreated portions of the neoplasm after therapy. In some instances, MR revealed postembolization residual enhancement of the tumor that was difficult to appreciate on x-ray angiograms. Very low contrast dose was necessary, which made repeated assessment during therapy practical. MR perfusion imaging with selective IA injection of dilute contrast can reveal the distribution territory of vessels. Changes in tumor vasculature could be detected after embolization, which reveal the volumetric fraction of the tumor affected by the therapy.

Cigarette-Smoke-Induced Vasoconstriction of Peripheral Arteries Evaluation by Synchrotron Radiation Microangiography

Although cigarette smoking is thought to constrict peripheral vessels, details have not been clarified because of the limitation of spatial resolution in conventional X-ray angiography systems. Synchrotron radiation microangiography can identify small arteries down to 50 microm in diameter. Male Wistar rats (n=9) were made to smoke a cigarette using the modified Griffith snout exposure system. Angiography of the rat hind limb was performed before, during, and 15 min after smoking. Arteries were classified into 3 groups based on the pre-smoking diameter: Group S: <100 microm, Group M 100-200 microm, Group L: >200 microm). In Groups M and L, arteries were constricted with smoking (mean diameter 140-106 microm; p<0.001, 260-162 microm; p<0.00001, respectively), whereas no constriction was noted in Group S (82-83 microm). Constricted arteries in Groups M and L returned to pre-smoking levels at 15 min after cessation of smoking. The acute changes brought about by cigarette smoking in rat peripheral arteries could be identified by synchrotron radiation microangiography. Cigarette smoking exclusively constricted arteries greater than 100 mum in diameter, which means there is vessel-size dependency of the impairment.