Tomosynthesis applied to digital subtraction angiography

This extension of our previous work on tomographic digital subtraction angiography (DSA) describes the theory of tomosynthetic DSA image reconstruction techniques. In addition to developing the resolution limits resulting from x-ray exposure length and image intensifier field curvature, we describe one method of image formation and show tomosynthetic DSA images of animal and human anatomy. Methods for improving the present technique are discussed.     

Cardiac imaging with digital subtraction angiography

Central cardiovascular anatomy and function have been evaluated with intravenous digital subtraction angiography (DSA). The subtraction techniques used for studying the left ventricle (LV) were mask mode, time interval difference and functional subtraction. Aside from contrast enhancement, a major use of digital fluoroscopy for cardiac applications has been computer-assisted quantitative analysis of LV dimensions and function. Left ventricular volumes and wall thickness determined from DSA studies have correlated closely with direct left ventriculograms and sonocardiometry measurements in patients and animals, respectively. Measurements of segmental LV contraction with DSA correlated closely with direct left ventriculography in normal patients and patients with coronary artery disease. The sensitivity of intravenous DSA for detecting significant coronary artery disease was increased by performing DSA immediately after increasing the myocardial oxygen demands by atrial pacing. The advantages and disadvantages of DSA in relation to other semi-or non-invasive imaging modalities are discussed.     

Internal densitometric gating for digital subtraction angiography

Motion artifacts create a severe problem in digital subtraction angiography (DSA) studies. Periodic motion can be eliminated by "gating," matching a precontrast mask with a postcontrast image at the same phase position in the cycle. Electrocardiogram (EKG) signals are used in cardiac DSA for this purpose. An alternate method relies on the generation of a density-time curve dependent on the attenuation changes of anatomical motion. A densitometric window placed at an appropriate location records the variation, from which individual images are tagged with phase position information encoded as delay time. Results are similar to the EKG gating method for cardiac DSA when using an appropriate window location. Periodic motion caused by superimposed respiration can be suppressed by tracking diaphragm or other object attenuation changes with the same algorithms. Using these techniques permits the nonarbitrary matching of mask and contrast images without physiologic monitoring. The techniques are straightforward and relatively easy to implement on systems designed for rapid digital imaging.     

64层螺旋CT与数字减影血管造影对颅内动脉瘤诊断的比较

目的 通过64层螺旋CT的CT血管造影(CTA)及CT数字减影血管造影(CTDSA)技术与数字减影血管造影(DSA)的比较研究,评价64层螺旋CT在颅内动脉瘤诊断中的临床应用价值。方法 26例临床怀疑颅内动脉瘤的患者实施64层CT和DSA检查,对64层CT图像进行了CTA和DSCTA两种方式的后处理。CTA后处理技术包括容积再现(VR),最大密度投影(MIP)和多平面重建(MPR),在CTA图像基础上用增强数据逐层减去平扫数据,自动去除骨与脑组织,获得CTDSA影像。比较3种技术(DSA、CTA和CTDSA)的特征。结果 26例可疑患者中,DSA和CTDSA发现31个动脉瘤,CTA发现29个动脉瘤。CTA漏掉的2个动脉瘤,直径小于3mm。结论 CTDSA是检查颅内动脉瘤的高度敏感的影像学方法,具有与DSA相当的价值。     

儿童先天性心脏病心血管造影检查技术

目的 探讨和评价儿童先天性心脏病心血管造影技术。方法 11045例儿童先天性心脏病患者做了心血管造影检查,采用的设备包括早期的快速换片心血管造影设备,电影心血管造影设备和数字减影心血管造影设备。使用了不同的心血管造影技术。结果 用快速换片心血管造影设备和常规正侧位投照时的儿童先天性心脏病心血管造影诊断符合率为80．5％,用电影心血管造影设备和轴位成角投照技术时的造影诊断符合率为90．0％,采用数字减影心血管造影设备,轴位成角投照技术和非离子型对比剂时的造影诊断符合率为96．5％。结论 对于儿童先天性心脏病心血管造影而言,使用动态电影摄片,作数字血管减影,采用轴位成角投照技术,使用非离子型对比剂和快速注射对比剂是取得高质量图像和理想诊断效果的关键。     

Zerebrale Gef??diagnostik – Bildgebung

Imaging of the cerebral vasculature relies mostly on computed tomography angiography (CTA), magnetic resonance angiography (MRA) and digital subtraction angiography (DSA). Although DSA is still the gold standard, many questions can be answered with CTA and/or MRA thanks to recent technological advances. The following article describes the advantages and disadvantages of these techniques with regard to different questions. Basic principles regarding the different techniques are explained.     

Evaluation of the processing functions of a digital subtraction angiography image processor

A large number of imaging systems for digital subtraction angiography (DSA) are now commercially available. Numerous evaluations of the performance of these systems have been reported in the literature. However systematic evaluations of the processing functions of DSA image processors have not been widely reported. Such an evaluation for one commercial system is presented in this paper. Functions evaluated include linear transformation, logarithmic transformation, integration, subtraction and temporal filtration. The observations indicate that image processing results are frequently achieved by indirect routes which compromise the fidelity of the image data.     

Arterielle Zugangswege in der interventionellen Radiologie

Transbrachial and transfemoral punctures are the conventional methods for accessing arteries in digital subtraction angiography (DSA). How to perform the punctures and how to use the different materials are elementary basics for diagnostic interventions in DSA, such as dilatating, stenting, coiling, implanting ports or chemical embolization. With both puncture methods different anatomic settings have to be considered and also experience with handling the surgical instruments has to be acquired. The management of complications and knowledge on the risk factors associated with each procedure are further requirements. An essential subject of studies is increasing the comfort for the patients by finding less invasive techniques in DSA.     

The AAPM/RSNA physics tutorial for residents: digital fluoroscopy.

A digital fluoroscopy system is most commonly configured as a conventional fluoroscopy system (tube, table, image intensifier, video system) in which the analog video signal is converted to and stored as digital data. Other methods of acquiring the digital data (eg, digital or charge-coupled device video and flat-panel detectors) will become more prevalent in the future. Fundamental concepts related to digital imaging in general include binary numbers, pixels, and gray levels. Digital image data allow the convenient use of several image processing techniques including last image hold, gray-scale processing, temporal frame averaging, and edge enhancement. Real-time subtraction of digital fluoroscopic images after injection of contrast material has led to widespread use of digital subtraction angiography (DSA). Additional image processing techniques used with DSA include road mapping, image fade, mask pixel shift, frame summation, and vessel size measurement. Peripheral angiography performed with an automatic moving table allows imaging of the peripheral vasculature with a single contrast material injection.     

Digital subtraction angiography in the community hospital

Although digital angiography may involve the same physician processes in the university as in the community hospital, it can be seen that the indications, approaches, and utility of DSA are somewhat different in the two environments. DSA is presently in a state of change, in part because of the maturing of other modalities and also because of the present emphasis on cost-saving in medical imaging. As referring physicians become used to digital arteriographic images, more and more procedures will be performed with DSA. We believe the DSA will have an important role in the community hospital for years to come. Its emergence as the first of the "conventional" imaging techniques to be digitized can be seen as an initial step toward the total digital imaging department of the future.     

Neurinoma of the jugular foramen

Summary The complementary predications of modern imaging techniques, CT, MRI and intraarterial digital subtraction angiography (i.a. DSA), in the differential diagnosis of a neurinoma of the jugular foramen are described.     

Digital subtraction angiography--a critical analysis

The advantages and disadvantages claimed for intravenous and intra-arterial digital subtraction angiography (DSA) are critically examined. The parameters determining image quality and the factors degrading the image in intravenous DSA are discussed. It is argued that many of the patients specifically referred for intravenous digital subtraction studies are unsuitable for this examination either because poor image quality is to be expected and/or because the large contrast load inherent in this type of examination is undesirable.     

Digital subtraction angiography: principles and pitfalls of image improvement techniques

The technology of imaging methods in digital subtraction angiography (DSA) is discussed in detail. Areas covered include function of the video camera in both interlaced and sequential scan modes, digitization by the analog-to-digital converter, logarithmic signal processing, dose rates, and acquisition of images using frame integration and pulsed-sequential techniques. Also discussed are various methods of improving image content and quality by both hardware and software modifications. These include the development of larger image intensifiers, larger matrices, video camera improvements, reregistration, hybrid subtraction, matched filtering, recursive filtering, DSA tomography, and edge enhancement.     

Ocular lens dose in cerebral vascular imaging

Ocular lens dose was considered with respect to cerebral vascular imaging, using both digital subtraction angiography (DSA) and conventional angiography. A dose measurement study is described in which doses were found to be minimal (0.327 cGy) in DSA, but high (60 cGy) using conventional techniques. The use of an undercouch tube in DSA and an increased focus-lens distance, when compared with the conventional angiographic approach were considered the major factors contributing to the difference in lens dose. The implications for selection of technique are discussed.     

Registered image subtraction for CT-, MR- and coronary angiography

Conventional post-processing of digital subtraction angiography (DSA) by 3D spiral CT, 3D MRI and 2D DSA is often hampered by extended artefacts due to patient movements during examination. In this paper an image registration procedure prior to the digital subtraction is introduced allowing an enhanced visualization of the contrast agent. The object displacement is detected by analysis of image deformations in small local regions. The motion pattern is used to compute a new synthetic mask of maximum congruence with the contrast medium image. This new mask image is then used in the subsequent subtraction. The algorithm works fully automatically and does not need any interactive placement of landmarks. Results obtained from subtraction of uncorrected and corrected sequences were compared with each other. The registration procedure provided good results in the suppression of subtraction artefacts and in the enhancement of vascular structures. Results are presented from subtraction of 2D and 3D data from CTA, MR mammography and coronary angiography. Received 10 August 1995; Revision received 18 March 1996; Accepted 12 April 1996     

Work in progress: the application of temporal filtering techniques to hybrid subtraction in digital subtraction angiography

Temporal filtering methods were applied to iodine signal-to-noise ratio (SNR) restoration in intravenous hybrid subtraction digital subtraction angiography (DSA). For equal detected exposure rates hybrid subtraction had approximately 35% of the SNR of temporal subtraction. When matched filtering was applied to a DSA run, the filtered result had approximately two times higher SNR than the peak contrast image in the run. Thus, when matched filtering techniques were applied to the hybrid image sequence, the resultant SNR increased to about 70% of that of temporal subtraction. With an additional factor-of-two increase in exposure rate for the hybrid run, SNR parity with temporal subtraction could be achieved. This compared with a factor-of-nine increase in exposure that would be required if no filtering were performed. Experimental hybrid matched filter results, generated with intravenous canine DSA studies, supported the predictions in SNR performance.     

Digital intraarterial subtraction technique of the extracerebral vascular system

We report the results from intraarterial digital subtraction angiography (IA DSA) of the extracerebral vessels with aortic arch injection of contrast medium via femoro-arterial puncture, instead of the more widely used intravenous digital subtraction angiography (IV DSA). Intraarterial DSA is performed using a lower contrast dose and rate, making this study less invasive and costly than the conventional arteriographic study of the aortic arch. Intraarterial DSA provides better resolution than IV DSA. The diagnostic accuracy is almost equivalent to conventional angiography and is largely superior to photographic subtraction angiography with intravenous injection of contrast media.     

3D rotational digital subtraction angiography may underestimate intracranial aneurysms: findings from two basilar aneurysms

3D digital subtraction angiography (DSA) allows clinicians to review intracranial aneurysms and other vascular lesions. We report 2 basilar aneurysms that were imaged by both 3D DSA and DynaCT. These 2 techniques produced very different aneurysm appearances. Anterior portions of the aneurysms were invisible on 3D DSA but were revealed by DynaCT. These aneurysms appeared to have been flattened by image artifacts in 3D DSA. Pulsation and gravity are 2 possible causes of aneurysm underestimation.     

全下肢动脉血管造影技术的临床应用探讨

目的比较血管造影跟踪法(bolus chasing angiography,BCA)与传统法(static digital subtraction angiography,DSA)的技术特点。方法回顾性分析了我院61例全下肢动脉血管造影患者的造影技术参数,其中31例采用BCA、30例采用DSA血管造影技术。分别对完成造影时间、对比剂用量、图像质量、患者吸收辐射剂量(dose-area product,DAP)进行对照分析。结果2种造影技术对比显示:DSA的图像质量在显示胫腓血管上优于BCA,但是DAP值高,对比剂用量多以及检查时间长。经统计学处理,二者差异均具有显著性(P<0.00)。结论BCA与DSA相比具有造影时间短,对比剂量用量少,DAP低的特点,DSA局部观察血管情况较细致。因此,先行BCA筛查,然后针对病变加做局部DSA。     

Peripheral vascular disease: prospective study of intraarterial digital subtraction angiography using a 9-inch intensifier

A prospective randomized study was undertaken to evaluate the role of intraarterial digital subtraction angiography (IADSA) in the study of peripheral vascular disease. Patients underwent either conventional film-based angiography alone, digital subtraction angiography (DSA) alone, or a combined study. With a 9-inch image intensifier, DSA alone resulted in cost savings of film and contrast material but required a significantly longer examination period than the other groups and an increased iodine dose per examination. When the images were analyzed by a radiologist and a vascular surgeon, the DSA studies provided less detail in the aortoiliac region than the other techniques but had advantages in demonstrating the runoff vessels. IADSA examination should not replace conventional arteriography in patients with peripheral vascular disease but has a useful complementary role.