EKG-gated digital subtraction angiography in the detection of pulmonary emboli

Digital Subtraction Angiography in Takayasu Arteritis

The usefulness and limitation of digital subtraction angiography (DSA) in Takayasu arteritis were investigated in 32 patients. Intravenous DSA was particularly useful in the follow-up of patients with an established diagnosis of Takayasu arteritis. Pulmonary arterial involvement could also be demonstrated with intravenous DSA as obstructive arterial changes and lack of accumulation of contrast medium in the pulmonary parenchyma. Detailed information concerning the site and extent of vascular involvement and development of collateral vessels were obtained with intraarterial DSA. Thickening of the thoracic aortic wall, however, could not be recognized with either intravenous or intraarterial DSA. Conventional angiography of the descending thoracic aorta is still required as an initial examination, particularly when there is no aortic arch involvement. However, there is no doubt that DSA has the potential to become the diagnostic procedure of choice in Takayasu arteritis.

Digital subtraction versus film-screen angiography for detecting acute pulmonary emboli: evaluation in a porcine model

PURPOSE

To compare the diagnostic performance of digital subtraction angiography (DSA) to that of film-screen angiography (FSA) for detecting acute pulmonary embolism (PE) in a porcine model.

MATERIALS AND METHODS

DSA and FSA were performed in 13 pigs before and after central venous administration of autologous emboli. Results were compared to findings at necropsy with use of ex vivo pulmonary angiography to guide pathologic sectioning. The sensitivity and predictive value of a positive case for detecting each embolus were computed for each pulmonary artery branch order and compared with use of 95% confidence intervals. Interobserver variability among three readers for individual PE detection was calculated.

RESULTS

Pathologic examination of the lungs revealed 100 total PEs (location by vessel order: 1st = 1, 2nd = 0, 3rd = 15, 4th = 32, > 5th = 52). On average, FSA review identified 72 (72%) emboli and DSA review, 65 (65%). There was no significant difference in sensitivity or predictive value of a positive case between DSA and FSA for detecting emboli (P > .05). There was similar agreement among readers for individual PE detection with DSA (mean, 84%) and FSA (mean, 80%).

CONCLUSION

The diagnostic performance of DSA is equivalent to that of FSA for detecting emboli in porcine PA branches. Interobserver agreement for individual PE detection is similar for both imaging techniques.

Improvement of digital coronary angiography: high resolution processing coupled with a real time functional synchronization procedure

The use of Digital Subtraction Angiography in coronary applications is restricted by the difficulty in: 1. Obtaining a good resolution of the distal branches. 2. Avoiding, for the purpose of subtraction, the motion artifacts induced by artery and background displacement during the cardiac and respiratory cycles. 3. Preserving the dynamic vascular motion. 4. And storing the digital dynamic information on a permanent support. We used for this study an angiography system, based upon a high resolution 45 MIPS-32 Mbyte image processor, interfaced with a 2.75 Gbyte Winchester drive allowing the real time storage of either 30 frames/s in the 512*512*8 bits matrix or of 7.5 f/s in the 1024*1024*8 bits matrix. To preserve the most important dynamic informations on the basis of the 7.5 f/s maximal storage rate, we developed a synchronization device able to recognize in real time, from chronologic delays derived by using both ECG and Aortic Pressure curves, the functional End-Diastolic (ED) and the End-Systolic (ES) positions, even in the case of heart rates varying during the procedure. The ED and the ES images are stored together with the Mid-Systolic (MS), the 1/3-Diastolic (1/3D) and 2/3-Diastolic (2/3D) images. To establish the validity of this sampling method, which uses a reduced number of frames per cardiac cycle, 7200 coronary injections performed during 450 routine coronary angiographies were compared by two independent observers (A and B), using: first a Digital (D) 5 frames/cycle sequence, and secondly a cine Film (F) 50 frames/s sequence acquired immediately after the corresponding D injection. The D technique resulted in the best image and diagnostic quality, particularly when the F quality was estimated 'fair' or 'poor' by both observers, and in an important reduction on X-Ray doses. The visualisation of the sequential ED, MS, ES, 1/3D and 2/3D frames gives the possibility: 1. of saving the dynamic information, as a regular sample of functional images can be displayed with a cine loop technique. 2. of facilitating cardiac synchronized subtractions. 3. of reducing the amount of frames per cycle, thus allowing an important reduction of X-ray doses and the digital and permanent storage of the most important cardiac cycles.

Pulmonary embolism

Pulmonary embolism is a common medical problem whose incidence is likely to increase in our aging population. Although it is life-threatening, effective therapy exists. The treatment is not, however, without significant complications. Thus, accurate diagnosis is important. Unfortunately, the clinical manifestations of pulmonary embolism are nonspecific. Furthermore, in many patients the symptoms of an acute embolism are superimposed on underlying chronic heart or lung disease. Thus, a high index of suspicion is needed to identify pulmonary emboli. Laboratory parameters, including arterial oxygen tensions and electrocardiography, are as nonspecific as the clinical signs. They may be more useful in excluding another process than in diagnosing pulmonary embolism. The first radiologic examination is the chest radiograph, but the clinical symptoms are frequently out of proportion to the findings on the chest films. Classic manifestations of pulmonary embolism on the chest radiograph include a wedge-shaped peripheral opacity and a segmental or lobar diminution in vascularity with prominent central arteries. However, these findings are not commonly seen and, even when present, are not specific. Even less specific findings include cardiomegaly, pulmonary infiltrate, elevation of a hemidiaphragm, and pleural effusion. Many patients with pulmonary embolism may have a normal chest radiograph. The chest radiograph is essential, however, for two purposes. First, it may identify another cause of the patient's symptoms, such as a rib fracture, dissecting aortic aneurysm, or pneumothorax. Second, a chest radiograph is essential to interpretation of the radionuclide V/Q scan. The perfusion scan accurately reflects the perfusion of the lung. However, a perfusion defect may result from a variety of etiologies. Any process such as vascular stenosis or compression by tumor may restrict blood flow. In addition, areas of the lung that are not well ventilated will be poorly perfused. Thus, a ventilation scan and a chest radiograph are essential to optimal interpretation of the perfusion scan. Ventilation/perfusion scans are interpreted as degrees of probability of pulmonary embolism. Emboli are not present in patients with a normal V/Q scan. An embolus is unlikely (10%-15%) among patients with a low-probability V/Q scan. However, small emboli that are nonocclusive may be present, and pulmonary arteriography may be used to further evaluate patients with a high clinical suspicion of pulmonary embolus.(ABSTRACT TRUNCATED AT 400 WORDS)

High resolution DSA: experimental and clinical evaluation

The DSA system has been upgraded for capabilities of slow scan video technique and progressive T.V. read-out of 1024 X 1024 matrix with 10 bits of depth. A square wave test pattern made of lead bar demonstrated moderate improvement in spatial resolution, but imaging of a Burger-Rose phantom revealed no significant increase in contrast resolution. Clinical study of various angiograms with intraarterial injections showed that there was slight improvement in the visibility of the vessels, especially small arterial branches, while there was no increase in visibility of the veins. There were no cases in which diagnoses were altered by application of high resolution DSA. With future improvements of the image intensifiers, DSA with 1024 X 1024 matrix may reveal its potential advantage, especially when coupled to larger image intensifiers such as 12 or 14 in.

Digital angiography in pulmonary embolism

Pulmonary digital subtraction angiography was diagnostic in 98.3 per cent of patients with possible acute pulmonary embolism. The procedure was well tolerated even in severely ill patients. A large image intensifier made simultaneous imaging of both lungs possible, reducing the number of contrast injections necessary. Small volumes of low iso-osmolar concentration of modern contrast media were used. There was no need for catheterization of the pulmonary artery. Theoretical considerations and our limited experience indicate that this will reduce the number of complications compared with conventional pulmonary angiography. The procedure is rapidly performed and the diagnostic accuracy high. This makes digital subtraction angiography cost effective. Digital pulmonary angiography can be recommended as the primary diagnostic method in most patients with possible pulmonary embolism.