Interventional Radiology

Radiology Today

As this chapter is being written, the importance of purely diagnostic conventional angiography decreases by the day. Vascular anatomy and disease can be imaged with a multitude of noninvasive modalities: ultrasound, Doppler ultrasound, spiral CT, and MR imaging (Fig. 7.1). These tests alone or in combination can sufficiently address most diagnostic issues. There are circumstances, however, where catheter-based angiography still has its place. It certainly is an integral component of all percutaneous therapeutic interventions for which intravascular access is a prerequisite:

• Dilations (for example, in arteriosclerotic vascular stenosis)

• Stent graft placement (for example, in aneurysms)

• Embolizations (for example, treating acute hemorrhage or to shut off blood supply to tumors)

• Vena cava filter placements (for example, in venous thrombosis and after pulmonary embolism)

• Shunt placements (for example, when performing a transjugular intrahepatic portosystemic shunt, TIPSS)

When the need for an intervention is anticipated, the diagnostic portion of the work-up can be done effectively by diagnostic angiography followed by the actual therapeutic part of the procedure since they use the same access route, resulting in an "all-in-one" procedure. Angiography of the veins—called phlebography or veno-graphy—has lost its relevance in daily radiological practice. This is due to the advent of new imaging modalities and a change in the therapeutic regimen for treatment of deep vein thrombosis. Ultrasound and Doppler ultrasound are now the first line modalities to assess extremity veins. If pulmonary embolism is suspected, spiral CT is the "one-stop-shop" procedure of choice wherever it is available (see p. 78).

Owing to the development of small-caliber access systems, minimally invasive intervention guided by sectional modalities (mostly CT and ultrasound) continues to be very successful. With few exceptions, virtually any region of the body can be accessed percutaneously and tissue can be sampled for histopathological diagnosis with significantly less risk and cost compared to surgical means. An abscess or fluid collection can be drained quickly, obstructed bile ducts can be relieved rapidly.

I MR Angiography

Angiography Lower Extremities
Fig. 7.1 The aorta (a, arrows) as well as its branches down into the lower extremities (b) and the vena cava (c, arrows) can be examined with contrast-enhanced magnetic resonance angiography—all of it completely noninvasive.

Finally, a variety of therapeutic agents may be introduced into the body: In osteoporotic and some pathological fractures of the vertebral bodies, the transpedicular injection of polymethylmethacrylate (PMMA) stabilizes the vertebral body and alleviates the pain (see Fig. 8.24c, p. 133). In extreme pain due to invasive pancreatic carcinoma, denervation of the celiac plexus by a percutaneous image-guided alcohol injection may offer effective palliative therapy; the actual procedure is associated with few risks and morbidity, an important consideration in patients with a very limited life expectancy

For students and beginners in radiology, angiography and intervention have a completely different feel to the stan dard radiology experience. A sure instinct and a lot of "touch" in the literal sense of the word (how about "Finger-spitzengefuhl" for a great German term), materials science, craftsmanship, precision, and diligence are prerequisites for successful treatment and need to be developed over time during training and even way into practice. A healthy helping of cold-bloodedness and "fortune" (pronounce this the elegant French way to describe the status of being a lucky kid) are other essentials of a successful interventionalist. A certain arrogance toward the noninter-ventional "armchair radiologists" comes as part of the package and is tolerated if the interventionalist is worth his money.

Table 7.1 Suggestions for modalities in angiography and intervention

Which imaging modality for which indication?

Indication

Imaging

Arterial problem

Depending on availability, expertise, and problem: angiography, ultrasound, Doppler ultrasound, MRA, CTA.

Venous problem

Depending on availability, expertise, and problem: ultrasound, Doppler ultrasound, CTV, venography, MRV.

Which intervention for which indication?

Intervention

Indication

Angiography

Planned recanalization, thrombolysis, balloon dilation, stenting of vessels, hemorrhage before anticipated embolization (i.e., gastrointestinal bleed).

Balloon dilation

Vascular stenosis, after recanalization, frequently after thrombolysis, before stenting (attention: small vessels and strong collateralization).

Stent implantation

Irregular plaque surface after balloon dilation, elastic stenosis, dissection, iliac occlusive disease. Stent grafts in aortic aneurysms and dissections should be performed by specialists only and with vascular surgical back-up.

Vena-cava filter

Pulmonary embolism and failed or contraindicated anticoagulation.

Transjugular intrahepatic portosystemic stent-shunt (TIPSS) implantation

Portal hypertension with recurring/uncontrollable gastrointestinal bleeds and ascites (attention: hepatic encephalopathy, cardiac insufficiency).

CT-guided tissue biopsy

Cytological, histopathological, and microbiological verification of disease.

Embolization

Occasionally in inoperable tumors; preoperatively in hypervascular tumors; therapy of arteriovenous malformations; arterial bleeds.

Port implantation

When mid-term intravenous access is necessary, e.g., in chemotherapy.

Neural blockade

When conservative pain medication fails or is not tolerated; to reduce dose of systemic analgesics in special pain syndromes.

Drainage

Image-guided drainage of abscesses and cysts. CT is the best modality for complex drain approach.

Radiofrequency ablation

In patients with small numbers of accessible liver tumors unsuitable for surgical resection.

CT, computed tomography; CTA, CT angiography; CTV, CT venography; MR, magnetic resonance; MRV, MR venography.

CT, computed tomography; CTA, CT angiography; CTV, CT venography; MR, magnetic resonance; MRV, MR venography.

In all elective interventions the patient should give informed consent after sufficient time has been given to explaining risks and benefits, complications, and alternative measures to the planned procedure. This should be done at least a day before the procedure. Blood clotting should be sufficient, that is, prothrombin time should be > 50 %, partial thromboplastin time < 35 seconds, thrombocyte count > 50 000/|il. Acetylsalicylic acid (ASA/aspirin) should be discontinued a week before deep body interventions are performed.

Do You Know Who Started It All?

Werner Forssmann was the first who, in 1929, inserted a catheter into a person's central vessels and heart: He did it to himself—against strict orders from his chief and while wrestling with a colleague who wanted to save his life. Forssmann also took a chest radiograph of himself to document the experiment. In 1956 a Swedish committee had to hunt him down by police in post-war Germany where he was practicing in a little town. The policeman eventually said to him: "They are looking for a Dr. Forssmann but it can't be you because this guy has won the Nobel prize."

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