Acute pulmonary embolism: diagnostic value of digital subtraction angiography

Digital subtraction angiography (DSA) performed via a peripheral vein was compared prospectively with selective conventional pulmonary angiography (CPA) in 54 patients suspected of having pulmonary embolism (PE). All patients also underwent ascending venography. In contrast to the conventional pulmonary angiograms, all of which were considered satisfactory, 13 of 54 digital subtraction angiograms (24%) were technically unsatisfactory. The interpretable digital subtraction angiograms had 81% sensitivity and 64% specificity. With DSA, one cannot exclude the diagnosis of PE on the basis of normal angiograms (27% false-positive results) as one can with perfusion scanning. On the other hand, DSA showed good sensitivity (94%) in medium to major PE. Therefore it may be the technique of choice in the screening of life-threatening PE for which curative emergency treatment with thrombolytic agents or embolectomy is often necessary.     

选择性DSA冠状动脉造影技术

作者应用数字减影对１００例进行选择性冠状动脉造影５１８次，其中临床疑有冠心病的７８例，发现冠状动狭窄５７例（７３．０８％）。左冠狭窄４１例（７１．９３％），右冠狭窄７例（１２．７８％），合并左右冠狭窄９例（１５．７９％）。作者着重介绍了选择性冠状动脉造影的方法和操作、投照位置，以及选用减影处理方式，应用技术和图像质量的关系。作者认为应用数字减影行选择性冠状动脉造影较常规造影具有优势和实用价值。     

Magnetic resonance imaging of aneurysms and thrombi

This is a report of the first systematic investigation of the qualitative and quantitative diagnosis of aneurysms in the regions of the left ventricle and thoracic and abdominal aorta plus proof of intracavitary thrombi in the heart and the aorta, as well as aneurysms in the superior and inferior vena cava. For diagnosis of the heart, ECG gating is an absolute necessity, but for the analysis of abdominal aortic aneurysms it only leads to a considerable improvement of the spatial resolution. For differential diagnosis of the blood flow and intracavitary clots in the heart and the aorta, use of a second or even multiple echoes is needed. Also, digital subtraction between the first and second echoes (magnetic resonance digital subtraction) can assist in assessing flow. When dissecting aortic aneurysm is suspected and in cases when risk of perforation of ventricular and aortic aneurysms is present, MR offers particular advantages, since it is noninvasive and few scans can provide all the information that is required.     

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.     

Dynamic time-resolved contrast-enhanced two-dimensional MR projection angiography of the pulmonary circulation: standard technique and clinical applications

OBJECTIVE: Time-resolved pulmonary two-dimensional MR projection angiography is a fast acquisition technique that allows the generation of dynamic projection angiograms by a method similar to that used to generate digital subtraction angiograms. MR images are obtained after subtracting the mask defined at the beginning of the sequence from later images, thus generating time-resolved continuous projection angiograms that depict the passage of a bolus through the pulmonary circulation. This article describes the application of this novel technique in three patients with pathologic conditions not previously described with this modality and two control subjects. CONCLUSION: The analysis of the findings on dynamic time-resolved contrast-enhanced two-dimensional MR projection angiography shows that this technique is useful not only in revealing morphologic changes associated with pulmonary disorders but also in following the passage of the bolus through the cardiopulmonary circulation. The latter capability allows qualitative detection of normal or abnormal pathways and thus is potentially of value in the assessment of several pulmonary disorders.     

I.v. and intraarterial hybrid digital subtraction angiography: clinical evaluation

Temporal/energy (hybrid) subtraction is a technique for removing soft-tissue motion artifact from digital subtraction angiograms. The diagnostic utility of hybrid subtraction for i.v. and intraarterial angiography was assessed in the first 9 months of operation of a dedicated production system. In i.v. carotid arteriography (N = 127), hybrid subtraction (H) provided a double-profile projection of the carotid bifurcation in an additional 14% of studies, compared with temporal subtraction (T) alone (H79:T48, p less than 0.001). However, a change in estimated percent stenosis or additional diagnostic information occurred in only 2% of studies. In i.v. abdominal arteriography (N = 23), hybrid subtraction, compared with temporal subtraction, provided a diagnostic examination in an additional 14% of studies (H20:T17); however, this difference is not statistically significant. An additional three i.v. abdominal angiograms were nondiagnostic. In intraarterial abdominal (N = 98) and pelvic (N = 60) angiography, hybrid subtraction provided a diagnostic examination in an additional 5% of studies (abdomen H94:T90, pelvis H58:T56); this difference was not statistically significant. An additional 5% of all intraarterial abdominal and pelvic digital subtraction angiographic studies were considered nondiagnostic. Hybrid subtraction provides a double-profile view of the carotid bifurcation in a significant number of patients. However, apart from some potential for improved i.v. abdominal arteriography, hybrid subtraction does not result in significant improvement in comparison to conventional temporal-subtraction techniques.     

Three-dimensional dynamic MR digital subtraction angiography using sensitivity encoding for the evaluation of intracranial arteriovenous malformations: a preliminary study

BACKGROUND AND PURPOSE: Our aim was to develop 3D dynamic MR digital subtraction angiography with high temporal resolution without sacrificing spatial resolution by using sensitivity encoding for the evaluation of cerebral arteriovenous malformations. METHODS: Nineteen patients with 19 angiographically proven arteriovenous malformations (16 supratentorial and 3 infratentorial) were assessed by conventional catheter angiography and 3D dynamic MR digital subtraction angiography. A 3D contrast-enhanced gradient-echo sequence with sensitivity encoding based on a parallel imaging technique was performed and acquired 20 dynamic images, repeated 18 times every 1.7 seconds. Three-dimensional dynamic MR digital subtraction angiograms were analyzed independently by two radiologists in a blinded fashion with regard to arteriovenous malformation nidus and venous drainage. Conventional catheter angiography was used as reference. RESULTS: All MR imaging examinations were assessable. Interobserver agreement was excellent for the detection of nidus and for the evaluation of nidus size (kappa = 1 and 0.875, respectively) but moderate for the visualization of the venous drainage (kappa = 0.56). All nidi detected on conventional catheter angiography were clearly depicted on 3D dynamic MR digital subtraction angiography. The evaluation of the size of the nidus by both techniques was similar. On 3D dynamic MR angiograms, veins were correctly analyzed in 17 of 19 arteriovenous malformations. CONCLUSION: Our preliminary study demonstrates that 3D dynamic MR digital subtraction angiography using sensitivity encoding with a high spatial resolution is appropriate for the assessment of arteriovenous malformations.     

Double blind comparison of Iomeprol 350 and Iopamidol 340 in intravenous digital subtraction angiography for peripheral vascular disease.

A randomized double blind study was undertaken to compare the diagnostic efficacy and side effects of a new non-ionic contrast medium Iomeprol with a commonly used one--Iopamidol. Visual and densitometric comparison was made of intravenous digital subtraction angiograms performed for peripheral vascular disease. The results show the two media to be similar both in imaging quality and in the incidence of associated side effects. Ninety-eight per cent of the intravenous digital subtraction angiograms were assessed as adequate for clinical management by the vascular surgeon.     

The use of the Fourier transform in cardiac digital angiography

Digital angiography has achieved broad clinical application as a morphological imaging modality through the technique of temporal subtraction known as digital subtraction angiography (DSA). After applying the Fourier transform to the intensity time curves (ITC) of an angiographic sequence, we are able to produce both morphological and functional images. The resulting pictures show an improved signal-to-noise ratio, reduction of motion artifacts, easy application of phase-synchronous subtraction, and integration and quantitative visualization of blood flow. The methods are demonstrated with nonselective angiograms and intravenous levocardiograms. Furthermore, when applied to angiographic sequences, the Fourier transform leads to a significant reduction in data without loss of important information.     

Dynamic contrast-enhanced MR angiography and MR imaging of the carotid artery: high-resolution sequences in different acquisition planes

BACKGROUND AND PURPOSE: First-pass contrast-enhanced MR angiography has become the technique of choice for studying the carotid bifurcation, but this method has some limitations. We evaluated the clinical utility of performing 3D contrast-enhanced MR angiography in the axial plane immediately after performing angiography in the coronal plane. METHODS: Cervical carotid arteries of 80 consecutive patients were studied on a 1.5-T MR imager with phased-array coils. Coronal 3D MR angiography was performed after administering a bolus injection of contrast material (20 mL) with automatic triggering. This was immediately followed by an axial acquisition. We measured carotid diameters on the contrast-enhanced MR angiograms as well as on intra-arterial digital subtraction angiograms according to established criteria. We also evaluated original source MR angiograms. RESULTS: Angiograms obtained in the axial plane correlated better with the intra-arterial digital subtraction angiograms than did the coronal angiograms. When first-pass contrast-enhanced MR angiography was incomplete because of a failure of triggering, the second-phase acquisition provided sufficient image quality. Original source images suffered from ring artifacts, low axial resolution, and a low level of soft-tissue visualization. Axial-based source images showed flow-independent contrast filling to the patent lumen with sufficient visualization of plaque morphology, thickened arterial wall, and surrounding disease processes, such as tumors. CONCLUSION: With the addition of a 1-minute second-phase 3D acquisition in a different plane immediately after first-pass contrast-enhanced MR angiography, one can obtain a more accurate depiction of the carotid bifurcation, insurance against failure of triggering, and diagnostic source images.     

Intravenous digital subtraction angiography by peripheral injection

We describe a technique for performing intravenous digital subtraction arteriography by peripheral injection and review our experience of 504 studies in 469 patients. The technique gave adequate opacification for anatomical definition of vessels in 93% of patients studied and was suitable for studies of the pulmonary arteries and left ventricle as well as the major systemic arteries. The chief causes of failure were impaired cardiac performance (2.4%) and poor patient cooperation (1.4%). Premature termination was caused by angina pectoris in 1.6% of our cases. These limitations apply also to central venous injection.     

A novel image fusion visualizes the angioarchitecture of the perforating arteries in the brain

We report a novel technique that fuses 3D digital subtraction angiograms and MR images. Image fusion was successfully performed within 20 minutes each in 11 consecutive cases. Our initial experience showed that this image fusion enabled clear and simultaneous visualization of perforating arteries and surrounding tissues. The relation between perforating arteries and normal brain or lesions was easily understood in a clinical setting by using this image fusion.     

Digital subtraction ventriculography in determining global and regional left ventricular parameters compared to left catheterization cardiography

Since May 1982 we studied more than 150 patients with heart diseases by means of digital angiography, out of them 46 patients with a history of transmural myocardial infarction were selected. Urografin 76, 30 ml, was administered at a flow rate of 18 ml/s by means of a catheter in the superior vena cava during digital subtraction ventriculography. Results were compared with conventional contrast ventriculograms. The correlation coefficient was r = 0.93 (p less than 0.001) for determination of ejection fraction with both methods. The data in individual cases suggest that DSV is more sensitive than conventional contrast ventriculography in determination of severely reduced ejection fractions. The methods are practically identical in qualitative evaluation of disorders of regional wall motion in the anterolateral region, while DSV is more sensitive than conventional ventriculography in evaluating the apical region. Sensitivity was 85.7% when the two methods were compared in evaluation of the inferior region of the left ventricle. Both methods are identical in demonstration of severely deformed ventricles. Digital subtraction ventriculography may replace conventional contrast ventriculography in some of the situations discussed above.     

DSA判断法乐四联症肺动脉狭窄和左心功能

目的：研究法乐四联症患者肺动脉狭窄和左心功能与手术关系。材料和方法：采用ＤＳＡ２４００型数字减影血管造影机（ＤＳＡ）测量了６３例法乐四联症患者心血管造影图像,并与手术结果进行对照分析。结果：肺动脉指数（ＰＡＩ）、ＭｃＧｏｏｎ比值、左心室射血指数（ＳＶＩ）与术后右心室／左心室压力比值呈负相关。结论：ＰＡＩ＞１５０ｍｍ２／ＢＳＡ,ＭｃＧｏｏｎ比值＞１．８,ＳＶＩ＞３０ｍｌ／ｍ２可作为法乐四联症心内修复术选择的定量指标。     

Stereoscopic display of MR angiograms

Summary Recent developments in magnetic resonance (MR) allow high resolution imaging of flowing blood. To overcome the tomographic nature of conventional MR acquisitions, projection angiograms can be produced. These angiograms are similar in their display of blood vessels to plain film or digital subtraction angiograms. However, the three-dimensional information inherent in them is partly lost when single projections are viewed. We describe a method of three-dimensional display consisting of stereo pairs of the MR angiograms. With these an examiner experienced in stereo viewing can recover depth perception.     

Subtraction helical CT angiography of intra- and extracranial vessels: technical considerations and preliminary experience

BACKGROUND AND PURPOSE: Reported CT angiographic (CTA) subtraction methods are not simple, robust, or real time. We investigated a novel technique for semiautomated digital subtraction CTA of the intracranial and extracranial arteries. METHODS: Thirty patients underwent precontrast (low milliampere-seconds) and postcontrast (pitch, 1.5; collimation, 1-2.5 mm) helical imaging with a vacuum-type head holder to facilitate image registration and minimize movement. A reconstructed three-dimensional model of the precontrast bone dataset was subtracted from the postcontrast dataset to produce subtracted maximum-intensity-projection angiograms. Experienced (operator 1) and less-experienced (operator 2) staff performed the standard and subtraction reconstructions, and image generation time and quality (graded 1-5) were compared. A third operator blinded to the method assessed the hard-copy image quality. RESULTS: Image quality with subtraction postprocessing was significantly better with both operators (operator 1, mean improvement of 0.87 grade, median improvement of 1 grade, P <.001; operator 2, mean improvement of 0.63 grade, median improvement of 1 grade, P <.001). Hard-copy image quality was better with the subtraction method (operator 1, P >.001; operator 2, P <.001). Blood vessels at the base of the brain were better demonstrated on subtraction images in 13 of 14 examinations. For the less experienced operator, the reconstruction time was significantly less with the subtraction method than with the conventional method (mean, 7.5 vs 10.1 minutes; P =.001). CONCLUSION: When separation of the vasculature from bone is important and technically difficult, digital subtraction CTA offers a potential advantage. This semiautomated technique is fast and easy to learn, and variably experienced staff can use it.     

Maskless 2-Dimensional Digital Subtraction Angiography Generation Model for Abdominal Vasculature using Deep Learning

PurposeTo develop a deep learning (DL) model to generate synthetic, 2-dimensional subtraction angiograms free of artifacts from native abdominal angiograms.Materials and MethodsIn this retrospective study, 2-dimensional digital subtraction angiography (2D-DSA) images and native angiograms were consecutively collected from July 2019 to March 2020. Images were divided into motion-free (training, validation, and motion-free test datasets) and motion-artifact (motion-artifact test dataset) sets. A total of 3,185, 393, 383, and 345 images from 87 patients (mean age, 71 years ± 10; 64 men and 23 women) were included in the training, validation, motion-free, and motion-artifact test datasets, respectively. Native angiograms and 2D-DSA image pairs were used to train and validate an image-to-image translation model to generate synthetic DL-based subtraction angiography (DLSA) images. DLSA images were quantitatively evaluated by the peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) using the motion-free dataset and were qualitatively evaluated via visual assessments by radiologists with a numerical rating scale using the motion-artifact dataset.ResultsThe DLSA images showed a mean PSNR (± standard deviation) of 43.05 dB ± 3.65 and mean SSIM of 0.98 ± 0.01, indicating high agreement with the original 2D-DSA images in the motion-free dataset. Qualitative visual evaluation by radiologists of the motion-artifact dataset showed that DLSA images contained fewer motion artifacts than 2D-DSA images. Additionally, DLSA images scored similar to or higher than 2D-DSA images for vascular visualization and clinical usefulness.ConclusionsThe developed DL model generated synthetic, motion-free subtraction images from abdominal angiograms with similar imaging characteristics to 2D-DSA images.     

Real-time digital subtraction angiography for therapeutic neuroradiologic procedures

Procedural control during therapeutic neuroradiologic procedures is generally based on repeated angiograms to assess the degree to which embolization has reduced abnormal blood flow. Due to the complex craniofacial skeletal anatomy that is superimposed over lesions in this area, subtraction studies are usually required to see the vessels and visualize a tumor stain satisfactorily. We have used a device incorporating continuous recursive digital video filtration, which allows the operator to view a subtracted fluoroscopic image of each control angiographic sequence in real time. The advantages of this technique for therapeutic procedures are described.     

Accurate analysis of blood vessel sizes and stenotic lesions using stereoscopic DSA system

We have developed a technique to determine accurately the magnification factor and three-dimensional orientation of a vessel segment from a stereoscopic pair of digital subtraction angiograms (DSA). Our DSA system includes a stereoscopic x-ray tube with a 25-mm focal spot shift. The magnification and orientation of a selected vessel segment are determined from the distance and direction of the focal spot shift and the stereoscopic discrepancy in image positions for that segment. Our results indicate that the accuracies of determining the magnification and orientation are less than 1% and approximately 5 degrees, respectively. After the magnification and orientation are determined accurately, an iterative deconvolution technique for the measurement of vessel image size is applied to the selected vessel segment. This iterative deconvolution technique provides the best estimate of vessel image size by taking into account the unsharpness of the digital system. With this technique, the vessel image size can be determined to an accuracy of approximately 1.0 mm, which corresponds to one third the pixel size of our DSA system. Information derived from stereoscopic analysis and iterative deconvolution thus allows accurate calculation of actual vascular dimensions from DSA images.