Digital radiography

DSA has quickly made the transition from an experimental examination performed in a research institution to a routine procedure performed in a community hospital. Diagnostic quality images for screening applications are obtained in over 90% of patients, and in many instances DSA is the only angiographic study that need be done.

The applications of IV DSA have broadened to encompass many angiographic procedures for which selective injections are not mandatory. When IA studies must be performed, digital equipment offers the advantages of speed, safety, and lessened patient discomfort. New technological developments will increase the advantages and applications.     

Echocardiographic gating in non-cardiac digital angiography

This paper reports the results of the ECG-gating in non-cardiac digital subtraction angiography (DSA). One hundred and fifteen patients underwent DSA (126 examinations); ECG-gating was applied in 66/126 examinations: images recorded at 70% of R wave were subtracted. Artifacts produced by vascular movements were evaluated in all patients: only 40 examinations, carried out without ECG-gating, showed vascular artifacts. The major advantage of the ECG-gated DSA is the more efficient subtraction because of the better images superimposition: therefore, ECG-gating can be clinically helpful. On the contrary, it could be a problem in arrhythmic or bradycardic patients. ECG-gating is helpful in DSA imaging of the thoracic and abdominal aorta and of the cervical and renal arteries. In the examinations of peripheral vessels of the limbs it is not so efficient as in the trunk or in the neck.     

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.     

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.     

Perimesencephalic subarachnoid hemorrhage: when to stop imaging?

To evaluate the yield of digital subtraction angiography (DSA) and repeated follow-up imaging in patients with initial pattern of perimesencephalic subarachnoid hemorrhage (PSAH) and negative computed tomography angiography (CTA) in excluding an underlying aneurysm. We conducted a retrospective analysis of all nontraumatic SAH who underwent a DSA between January 2006 and January 2010 and selected those with a PSAH pattern on CT done within 72 h from ictus. All CTAs were performed with a 64-section multidetector row CT scanner, and findings were compared with DSA and to follow-up imaging. Forty-nine patients with initial PSAH pattern and negative CTA who underwent subsequent DSA were identified. Six patients were excluded because CTA was not available in hospitals or 72 h after ictus. Only one patient (2.4%) had a false negative CTA with a 1-mm left ICA aneurysm seen on DSA, considered not to be the source of hemorrhage. An average of 2.0 ± 1.2 follow-up exams per patient (range 0–5) revealed no source of bleeding. One patient had a procedure-related transient complication, but evolved with no sequels. In patients with PSAH, CTA is reliable for ruling out an underlying aneurysm. DSA and, especially, further follow-up imaging have no increased diagnostic yield compared to initial negative CTA.     

Indications for intravenous and intraarterial digital subtraction angiography (DSA) in the diagnosis of cerebrovascular insufficiency. A new diagnostic concept including ultrasound

For screening of arteriosclerotic lesions of the carotid bifurcation duplex scanning (B-mode imaging plus doppler flow analysis) is the method of first choice, because it is really noninvasive and offers the same results as intravenous DSA (IV DSA). IV DSA should not be performed as a screening procedure unless ultrasound examinations are not available or are inadequate. Except for patients with isolated unilateral stenosis of the internal carotid artery near the bifurcation confirmed with both duplex scanning and IV DSA, arteriography is required for therapy planning. Aortic arch angiogram, selective extra- and intracranial carotid arteriography and--if necessary--vertebral and subclavian arteriography can be performed with intraarterial DSA (IA DSA). The application of DSA to catheter arteriography will help to reduce further the potential risk of adverse reactions related to high intravasal contrast doses specially in the cerebral circulation, but will not turn arteriography into a risk-free procedure. Postoperative examinations of the carotid bifurcation can be performed with ultrasound as well as with IV DSA. Extracranial bypasses are best demonstrated with IV DSA. Extraintracranial bypasses can be demonstrated only with IA DSA.     

Intravenous 3D digital subtraction angiography in the diagnosis of unruptured intracranial aneurysms

Recent progress in digital subtraction angiography (DSA) devices makes it possible to perform rotational angiography with high resolution and high sensitivity. We tried intravenous (IV) 3D DSA in patients who had undergone MR angiography (MRA) suggestive of unruptured intracranial aneurysms. IV 3D DSA can be used as an alternative method for imaging unruptured intracranial aneurysms suggested on MRA.     

Digital angiography

The many available methods of digital subtraction angiography (DSA) are briefly reviewed. At present the most commonly used are temporal filtration techniques, which include conventional subtraction, integrated remasking , and various types of filtering. Their present use in intravenous, as well as intra-arterial, DSA is shown. The "moving mask" subtraction technique for cardiac and coronary studies is of particular interest. The current status of second-order subtraction techniques such as tomographic DSA and parametric digital imaging is presented. The latter method is particularly useful for demonstration of shunts. Finally, several examples of non-angiographic and future applications of digital radiography are presented.     

MR动态减影血管造影在脑动静脉畸形治疗前后中的评价

目的评价MR动态减影血管造影（MR-DSA）在脑动静脉畸形（AVM）栓塞治疗前后的价值和限度。方法22例AVM患者，在栓塞前后均行MR—DSA、三维增强MR血管造影（3D—CEMRA）、MR质子加权成像（PWI）和DSA检查，同时由2名有经验的医生独立进行双盲对照研究。结果MR-DSA和DSA在22例AVM栓塞前后的瘤巢大小及分类上结果一致，MR—DSA能够显示AVM栓塞后的血液动力学改变，瘤巢及引流静脉显影推迟17例，瘤巢变小13例（其中完全消失4例），与DSA符合率为100％。与DSA相比，MR-DSA没有显示瘤巢内动脉瘤和栓塞后引流静脉及供血动脉直径变小各1例，而3D-CEMRA对此显示清晰。栓塞后的PWI与栓塞前相比，22例均可见不同程度的高信号。结论MR—DSA是1种快速、有效、无创的血管造影检查方法，能提供AVM栓塞前后的血流动力学信息，MR—DSA、3D-CEMRA和PWI应在AVM的随访中相互结合，综合运用。     

Tomographic DSA using temporal filtration: initial neurovascular application

A preliminary study showed that encouraging laboratory results reported previously using tomographic digital subtraction angiography (DSA) can be transferred to clinical application for neurovascular imaging. Tomography may show cervical carotid disease more clearly than standard DSA images, and it eliminates the interference caused by overlapping vessels. Production of multiple tomographic image planes from a single set of projection data, tomosynthesis, must be incorporated into this imaging system before tomographic DSA becomes clinically useful. This is a practical reality with the present equipment; clinical evaluation of this new capability is underway.     

Characterization of aneurysm remnants after endovascular treatment: contrast-enhanced MR angiography versus catheter digital subtraction angiography

BACKGROUND AND PURPOSE: A substantial percentage of coiled aneurysms are associated with persistent filling of an aneurysmal component due to incomplete initial treatment or re-growth. Traditionally follow-up of coiled aneurysms has consisted of repeated intra-arterial cerebral catheter angiography, an invasive procedure with associated risks. Hence, many authors have advocated the use of non-invasive imaging techniques for this purpose. Our aim was to compare contrast-enhanced MR angiography (CE-MRA) with digital subtraction angiography (DSA) for depiction of aneurysmal remnants of coiled cerebral aneurysms.MATERIALS AND METHODS: Aneurysms coiled between September 2003 and October 2006 were retrospectively reviewed. We included patients meeting the following criteria: 1) residual/recurrent aneurysm measuring 2 mm or greater, and 2) CE-MRA and DSA performed no more than 60 days apart. Three readers were asked to determine which technique was superior for characterization of the aneurysmal remnant: CE-MRA, DSA, or indeterminate. Statistical analysis included most rule and κ statistics.RESULTS: Of 232 patients who underwent coiling, 44 met the inclusion criteria (33 women and 11 men; 24–72 years of age). Sixteen patients had neck remnants and 28 had body remnants. The first study to identify the remnant was DSA in 35 patients and CE-MRA in 9. In 32 patients (32/44, 73%), the readers indicated that CE-MRA was superior to DSA for remnant characterization. CE-MRA and DSA were thought to be equivalent in 7 (16%), and DSA was preferred in 3 (7%). Two cases (5%) yielded ambiguous results. Of the 28 body remnants, 22 (78.6%) were characterized by remnant protrusion into the coil mass: In 20 of these (91%), the readers preferred CE-MRA over DSA, and in 2 cases (9%), the techniques were thought to be equivalent.CONCLUSION: In patients with known aneurysm remnants, CE-MRA is at least equivalent to DSA for characterization of aneurysmal remnants after coiling. Contrast filling within the coil mass was more clearly seen with CE-MRA than with DSA.

Since the publication of the International Subarachnoid Aneurysm Trial,¹ intracranial aneurysms are increasingly treated with endovascular coiling. A substantial percentage of coiled aneurysms are associated with persistent filling of an aneurysmal component either due to incomplete initial treatment or regrowth.^1,2 Reconfiguration of the coil mass with time results in a recurrent aneurysmal neck or body remnant,^3,4 which leads to reperfusion of the aneurysm, exposing the patient to a risk of rupture and rebleeding.¹ For this reason, follow-up imaging (surveillance) of coiled aneurysms is important. When a considerable aneurysmal remnant is identified, recoiling is commonly advised. Traditionally this surveillance has consisted of repeated digital substraction angiography (DSA) in the months and years following the initial endovascular coiling. DSA is, however, an invasive procedure with well-known associated risks.⁵ Additional disadvantages include a short postprocedural hospital stay, radiation exposure, allergic or nephrotoxic effects of iodinated contrast medium, and patient discomfort and expense. Hence, many authors have developed and advocated the use of noninvasive imaging techniques for the surveillance of aneurysm postcoiling.^6-15The accuracy and reliability of contrast-enhanced MR angiography (CE-MRA) to identify an aneurysm recurrence in coiled patients has been established.^6,7,10,13 Although it is now recognized that CE-MRA is not devoid of risks,^16,17 these risks are negligible and avoidable, compared with those of DSA. The purpose of this trial was to further evaluate the performance of CE-MRA for the depiction of the size and configuration of these aneurysmal remnants compared with DSA (the gold standard). This trial will help further define the role of noninvasive imaging in the surveillance of patients with previously coiled aneurysms.     

Current experience with digital subtraction angiography in the community medical center

At the community medical center, we have introduced and successfully applied digital subtraction angiography (DSA) to disease processes seen in 1,144 patients. Although there is a trade-off between increased contrast resolution and decreased spatial resolution with the DSA approach, nonetheless in many vascular beds it provides rapid, safe, and accurate disease diagnosis.     

MR digital subtraction angiography in the diagnosis of meningiomas

OBJECTIVE: MR digital subtraction angiography (DSA) is a technique for demonstrating the vasculature combining a rapid two-dimensional T1-weighted sequence with a bolus injection of gadolinium. We attempted to determine its contribution to the diagnosis of intracranial meningiomas. METHODS AND PATIENTS: MR DSA was performed in 18 patients with meningioma as well as in 28 patients with other tumors. The findings were analyzed regarding demonstration of tumor stain and tumor-related vessels. RESULTS: All meningiomas except one were visualized as a homogeneous and intense stain. Feeding arteries were visualized in 2 patients, and draining or abnormal veins in three. In 21 of the 28 patients with other tumors, tumor stains of varying degrees were demonstrated. CONCLUSION: MR DSA can serve as an adjunct to routine MR imaging, because it enables assessment of the hemodynamics of meningiomas and facilitates its differential diagnosis from other tumors.     

小型医学影像存储与传输系统的临床应用

目的 探索小型医学图像存档与通讯系统(minimizing picture archiving and communication system，mini—PACS)在实际工作中的应用，逐步实现科室内的无胶片化管理。方法 建立基于PC机的局域网，连接CT、MR、数字胃肠机、DSA、激光相机等医学影像设备，整合数字图像网络(digital imaging network，DIN)和医学图像诊断系统(medical diagnostic imaging system，MDIS)，组成放射科信息管理系统(radiology information system，RIS)。RIS系统通过其中1台安装双网卡的PC工作站与医院信息系统(hospital information system，HIS)相连。结果 系统在2年多的时间内得到连续使用，放射科信息管理系统得以实现和完善。在现有的数字化影像设备上实现了符合医学数字图像传输标准3．0(digital imaging communication in medicine，DICOM3．0)格式的图像采集、储存、传输、打印、浏览功能。图像和诊断报告信息通过Microsoft Access数据库管理，不同设备上保存的在线图像为3～6个月，所有图像用CD—R光盘刻录，作为离线永久保存，已有32700多份诊断报告存入数据库；HIS终端可有限制地从该系统获得图像和诊断信息。结论 mini—PACS系统投入和运行成本低、维护简单、性能可靠，可基本实现PACS的重要功能，在中、小医院具有良好的应用前景。     

Diagnosis of aortic aneurysm

The aim of the study was to analyze the use and indication of 3 imaging modalities (CT,DSA and MRI) for patients with suspicion of aortic aneurysm. During 18 months 383 patients with suspicion of aortic aneurysm were examined with CT (SCT/MSCT), 17 with digital subtraction angiography (DSA) and 15 with MRI. Diagnostic DSA was performed in 7 cases for planning endoluminal therapy, in 7 cases because of unclear findings in CT and in 4 cases because of dissection of the aorta. MRI was performed in 12 cases with previously performed CT and in 3 cases as the only imaging modality because of intolerance to iodinated contrast material. CT is a well established and in most cases sufficient method for the examination of patients with the suspicion of aortic aneurysm. CT is widely available, and provides good image quality and a high diagnostic accuracy. Additional examinations with DSA or MRI are necessary in less than 5% of the patients.     

Digital subtraction angiography (DSA)

Summary A four year study has been undertaken into the effects on the workload and cost implications of the introduction of digital subtraction angiography (DSA) in a large United Kingdom teaching hospital. The increase in workload has been entirely due to the ability to perform intravenous angiography. DSA is cheaper than conventional angiography if more than 210 cases are undertaken each year. This difference is accounted for by the reduced use of X-ray film. However, intravenous angiography is more expensive because of the use of large volumes of nonionic medium.     

Dynamic and static phantoms for evaluation of digital subtraction angiographic systems

Two types of phantoms were developed with which to evaluate the overall performance of digital subtraction angiography (DSA) systems. A dynamic phantom, called a "fish bone" phantom, consists of polyethylene tubes that simulate blood vessels with various lesions, such as stenoses, ulcers, and aneurysms. With this phantom, washout curves were obtained representing the relationship between iodine content and time. It will be useful for qualitative assessment of DSA images, evaluation of different image-processing schemes, and studies of blood flow analysis. A static phantom, called a "C-D" phantom, can be used for measurement of quantitative contrast-detail (C-D) diagrams and for daily monitoring of DSA systems. This was constructed of tubes of seven different diameters (2.15-0.28 mm) and 14 different concentrations of contrast medium (100%-1.1% Renografin-76 [meglumine and sodium diatrizoate]). The C-D diagrams were determined from an observer performance study using C-D phantom images obtained at four different DSA settings.     

MR-DSA在评价脑动静脉畸形栓塞前后的价值和限度

目的 评价动态MR血管造影(MR—DSA)在观察脑动静脉畸形栓塞前后的价值和限度。资料与方法 22例脑动静脉畸形患者，在栓塞前后均行MR—DSA、三维增强MR血管造影(3D—CEMRA)、质子加权成像(proton imaging)和数字减影血管造影(DSA)检查，同时由2位有经验的医师独立进行双盲对照研究。结果 MR—DSA和DSA在22例脑动静脉畸形栓塞前后的瘤巢大小及分类上结果一致(100％)，MR—DSA能够显示脑动静脉畸形栓塞后的血流动力学改变，瘤巢及引流静脉延迟显影17例，瘤巢变小13例(其中完全消失4例)，与DSA的符合率为100％。与DSA相比，分别有瘤巢内动脉瘤和栓塞后引流静脉及供血动脉直径变小各1例，MR—四A没有显示，而3D—CEMRA显示清晰。栓塞后的质子加权图像与栓塞前相比，22例均可见不同程度的高信号。结论 MR—DSA是一种快速、有效且无创的血管造影检查方法，能提供脑动静脉畸形栓塞前后的血流动力学信息，MR，DSA、3D—CEMRA和质子加权成像应在脑动静脉畸形的随访中相互结合，综合运用。     

肌纤维发育不良影像学特征及误诊分析

目的探讨肌纤维发育不良的影像学特征,减少该病的误诊。方法回顾性分析7例临床诊断为肌纤维发育不良患者的临床和影像学资料,这些病变早期常误诊为动脉硬化性血管病,或将其并发症作为主要诊断。经多层螺旋CT血管成像(CTA)、磁共振成像(MRI)和数字减影血管造影(DSA)中一种或多种检查,由两名高年资诊断医师和一名介入科医师共同对所有病例的影像资料进行综合分析,得出诊断。分析内容包括病变的位置、形态和并发症。结果7例肌纤维发育不良共有25处病灶,累及1个部位4例,2个部位1例,2个部位以上2例。25处病灶依据Kincaid分型,计算血管狭窄形态发生率,串珠样改变23处(92%),混合型2处(8%)。肌纤维发育不良伴有动脉夹层5例,伴有动脉瘤2例,伴有脑梗塞1例,伴有肾梗死2例,伴有颈动脉海绵窦瘘1例。结论肌纤维发育不良在中青年女性中常见,串珠样改变的影像学表现具有相对特征,综合利用CTA、MRI及DSA可以显示肌纤维发育不良病变特点及并发症。认识这些特征,有助于提高该病诊断,减少误诊。