Pozos tipo “S”

No focal signs were elicited and the CXR suggested pulmonary artery prominence without cardiomegaly. The patient underwent pulmonary DSA to exclude embolism.

Contrast (lopamidol 370, Bracco Diagnostics, Milan) was injected at 25 ml/sec for a total of 40 ml, through a 5 Fg straight, multiple side-hole catheter, inserted into the SVC from the right basilic vein. Images were acquired onto a 256 by 256 matrix at 5 frames per second.

Enlargement of the left proximal pulmonary artery can be clearly seen, together with marked bilateral peripheral pruning of the vessels, figure 9. There was no evidence of embolism on this study. TTie likely cause of these appearances was chronic lung disease associated with smoking.

This case illustrates the value of venous DSA in obtaining diagnostic pulmonary arteriograms without needing to formally catheterize the patient. ECG gating was not used to obtain these images. Instead, multiple pre-contrast images were obtained providing a choice of appropriate mask for individual contrast images, resulting in good subtraction despite cardiac pulsation and respiration. The benefit of this flexibility in choosing a subtraction mask is exemplified in figures 9a and 9b. The difference between them is in the choice of mask, note how the movement artifacts adjacent to the left heart border have been removed in figure 9b, simply by using a mask image from a different part of the cardiac cycle. Such flexibility makes DSA a valuable additional tool in evaluation of pulmonary vascular diseases.

Thus while formal cut film pulmonary angiography remains the gold standard for diagnosis of pulmonary embolism, DSA can often provide sufficient information to

make the diagnosis and allow treatment to proceed. The benefits of this approach are twofold, firstly a non-selective injection of contrast eliminates the need for catheter manipulation through the right ventricle, inherently a procedure with slightly higher risk compared to a basilic vein puncture and SVC catheterization. Secondly, the procedure is potentially more rapid and better tolerated by patients, so that a definitive diagnosis can be made in a highly time efficient manner.

Furthermore, formal pulmonary arteriography is not precluded if the initial DSA is non-diagnostic, as modern angiographic equipment often has both capabilities available. In short, if intravenous DSA can give the answer the patient benefits. If, despite DSA, a selective catheter arteriogram is necessary, very little time has been lost by attempting the DSA.

Case 4

A 53 year old white female developed acute chest pain associated with haemotpysis and

dyspnoea following routine surgery at an outside institution. Pulmonary embolism was suspected and she was referred for angiography.

Contrast (lopamidol 300, Bracco Diagnostics, Milan) was injected at 25 ml/sec for a total of 40 ml, through a 5 Fg straight, multiple side-hole catheter, inserted into the IVC from die right femoral vein. Images were acquired onto a 256 by 256 matrix at 5 frames per second, figure 10. Large emboli were identified in both proximal pulmonary arteries. The embolus on the left was seen to prevent perfusion of the upper lobe, while on the right only the upper lobe was perfused. The patient was immediately transferred for thrombolytic therapy.

This case exemplifies the ability of DSA to rapidly obtain diagnostic quality images of the proximal pulmonary arteries from a non-selective injection of contrast. The total study time was less than 15 minutes and no delay was introduced before thrombolysis commenced.

Figure 9. Two images of the same frame using masks from different parts of the cardiac cycle for subtraction. Note how the vessels abutting the left heart border (white arrow) are much more clearly seen in b. This is evident by the loss of the double shadow along these vessels due to motion between the mask and data images observed in a (arrow).

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Figure 10. Single DSA images of the right (a) and left (b) proximal pulmonary arteries, showing a right sided puhnonary artery embolus preventing perfusion of the middle and lower lobes (white arrow), and a left sided pulmonary embolus occluding the upper lobe (black arrow).

Case 5

A 31 year old white female presented to her GP with symptoms of progressive dyspnoea.

She was a non-smoker. She had used oral contraceptives for approximately 5 years. On examination there was evidence of elevated right ventricular pressure and raised systemic venous pressure. Her chest radiograph showed prominent hila and a working diagnosis of pulmonary arterial hypertension was made. She was referred for DSA as an outpatient, figure 11.

Contrast (lopamidol 300, Bracco Diagnostics, Milan) was injected at 25 ml/sec for a total of 40 ml, through a 5 Fg straight, multiple side-hole catheter, inserted into the SVC from the right basilic vein. Images were acquired onto a 256 by 256 matrix at 5 frames per second. The prominent proximal pulmonary arteries were clearly seen, together with marked peripheral attenuation. Additionally, there was reduction in lung parendiymal vascular blush in a patchy, non-segmental distribution. These appearances are consistent with primary pulmonary hypertension.

Intravenous DSA may also be used non-emergenüy to evaluate patients presenting with progressive dyspnoea and no apparent aetiology. DSA can be used as an outpatient procedure with minimal disruption to the patient. In order to evaluate perfusion within lung parenchyma, it is necessary to either ECG gate the acquisition, or to acquire multiple pre-contrast images retrospective gate by matching mask and data images from the same part of the cardiac cycle. Furthermore, in co-operative patients, a good breath-hold can result in excellent subtraction of the ribs. These two manoeuvres successfully applied will result in very good quality pulmonary

arteriography. One of the most valuable features of DSA is that all the image data are stored in a computer as individual pixel values and may be manipulated mathematically. The ability to identify vascular structures at different phases of perfusion, together with the accompanying timing information can provide a definitive diagnosis by using parametric and region of interest imaging.

Case 6

A 32 year old white female presented with a history of periodic fever, left sided chest pain

and dyspnoea. Chest radiography showed a round mass near the left pulmonary artery. Prior to needle biopsy DSA was undertaken to exclude a vascular lesion, prior to biopsy. Contrast (lopamidol 370, Bracco Diagnostics, Milan) was injected at 25 ml/sec for a total of 40 ml, through a 5 Fg straight, multiple side-hole catheter, inserted into the SVC from the right basilic vein. Images were acquired onto a 256 by 256 matrix at 5 frames per second, figure 12. The non-vascular nature of this lesion was confirmed, the biopsy showed carcinoid tumor.

The image in figure 12b is obtained by calculating the maximum intensity in each pixel during the whole acquisition and plotting only this value. Other parameters may be obtained which depend on timing information present in the digitally collected data. This aspect of DSA is further amplified in the next chapter.

Figure 11. Left and right lung DSA shows marked proximal pulmonary artery hypertrophy with distal tapering and pruning. Note the paucity of perfusion blush in a non-segmental distribution. These findings are strongly suggestive of primary pulmonary hypertension, rather than the sequelae of chronic recurrent thromboembolism. Almost perfect subtraction has been achieved, simply by allowing a long acquisition before contrast to gather a wide choice of mask images to match with individual contrast or data images.

Figure 12. The straightforward subtraction image(a) shows paucity of filling of the left upper lobe vessels. The ROI, (white box) identified the position of the mass on plain film radiography, and can be seen to be separate from the pulmonary arteries. In order to visualize both arterial and venous phases of pulmonary perfusion a collapsed or parametric image can be produced, (b). The non- vascular mass was compressing the left upper lobe artery causing partial obstruction to perfusion.

4.1.4 Pulm onary Vascular Malformations

The nature of DSA is such that it is possible to obtain high resolution images of the peripheral vascular tree of the lungs w ithout selective catheterization. This property is useful in the evaluation of potential vascular malformations. Subsequent

treatm ent can also be provided by using DSA to closely m onitor catheter placem ent and the arterial and venous anatom y comprising the lesion to be treated.

Case?

A 12 year old white female presented with haemoptysis. Chest radiography showed a