Ultrasound / Interventional Radiology
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CURRENT PATHOLOGY IMAGING GUIDELINES
CONTENTS
A. Neck and thoraxD. Vascular system
Imaging resourcesF. Spine
G. Extremities
[Plain film:]
- vascular calcifications (aneurysm of the aorta, arteriosclerosis, diabetic angiopathy), complications (atrophy, infections)
Arteriography
- preoperative work-up (detailed anatomy, collaterals)
- allows consecutive interventional procedures (dilatation,
embolisation).
Pulmonary Angiography
- pulmonary embolism (only if at least one positive previous test such as Doppler, scintigraphy, D-dimers)
- arteriovenous malformations, mycotic aneurysm
- contraindications: cardiovascular instability, ventricular arrhythmia, left bundle-branch block, severe pulmonary hypertension, allergy to contrast media, myeloma, unstable diabetes, renal failure.
Digital substraction intravenous angiography:
- no arterial puncture, easier to perform
- less anatomical detail, unforeseeable picture quality, necessity of high volumes of contrast medium.
Phlebography
- imaging of recent and older thromboses if Doppler ultrasound unconclusive. May fail to opacify some deep veins.
- preoperative work-up: integrity of the deep venous network,
good depiction of the perforating and varicose veins.
EchoDoppler ultrasound
- morphological analysis of the vessel (arteries: stenosis, atheroma, dilatation, thrombus / veins: compressibility of the vessel, dilatation, thrombus)
- Color Doppler visualization of the flux in real time (stenoses, accelerations and decelerations, demonstration of pseudo-/aneurysms and of arteriovenous fistulas)
- Power Color Doppler ("energy", "angiographic") : the signal is not depending on the angle of ultrasound incidence, whence better visualization of the vascular tree of an organ or of a vessel in a horizontal plane.
- Pulsed spectral Doppler: direction and speed of the flow, haemodynamic profile of a stenosis, of intraparenchymatous vessels
- Continuous spectral Doppler: more sensitive to slow flow than pulsed Doppler, but doesn't show direction of the flow, doesn't explore a definite volume, no ultrasound images
- Doppler ultrasound after intravenous contrast medium: higher vascular Doppler signal in difficult cases; easier parenchymal lesion depiction with cinetic study possibility.
CT angiography
- multidetector CT-scans allow volumic acquisitions and good spatial resolution of the vessels (renal arteries, coeliomesenteric vessels, polygon of Willis, carotids)
- highly calcified vessels are more difficult to image
MR angiography
- several complementary techniques, 2D and 3D. Artery calcifications don't influence image quality
- no X-rays, no iodinated contrast medium (often IV Gadolinium)
- adequate patient collaboration necessary
- spatial resolution is a little lower than with angioCT
- artifacts may sometimes cause under- or overestimation of a
stenosis. May miss very small intracranial aneurysms.
- EchoDoppler: DVT, ruptured popliteal cyst, abscess or hematoma of the calf, panniculitis, fasciitis, aneurysm or thrombosis of the popliteal artery. Allows to rule out a thrombosis from the iliofemoral to the popliteal level. Ultrasound is usually able to show a thrombosis of calf veins, but not to rule it out entirely
- Phlebography if US-Doppler not conclusive
- Dosage of D-dimers (very sentitive but not specific)
- Plethysmography
- Arteriography (vital organ or threat of necrosis): preoperative work-up; allows interventional procedures or a local fibrinolysis
- EchoDoppler in most other cases
- CT angiography, MR angiography.
- EchoDoppler: visualization and measurement of stenoses, atheroma plaque, aneurysms, steal syndrome (subclavian), reversal of flow. Applications: carotids, extremities, abdominal vessels, cerebral arteries (transcranial, transfontanellar Doppler)
- MR angiography: more precise work-up
- Angio-CT: same as MRI, but lower sensitivity for carotid or vertebral artery dissection
- Arteriography: to perform angioplasty, as preoperative work-up or for traumatic lesions.
4. Aneurysm of the abdominal aorta
- EchoDoppler: allows to rule out an aneurysm. Demonstrates the dilatation, the wall thrombus, the remaining aperture; less reliable than CT to rule out fissuration of the wall. Fairly high risk of rupture if diameter > 5 cm.
- CT (and angio-CT): more precise diagnosis (inclusion of the renal arteries in the aneurysm, abdominal organ ischemia, signs of fissuration).
- MR angiography
- Arteriography: preoperative work-up
5. Dilatation of a peripheral artery:
- Color and pulsed EchoDoppler: aneurysm, ectasia, arteriovenous fistula. Haemodynamic downstream repercussion. Compression treatment of an iatrogenic pseudoaneurysm (after arterial catheterism).
- MR angiography
- Arteriography: preoperative work-up.
- EchoDoppler: abdominal masses compressing the iliac or caval veins. Thrombosis. Cardiogenic central venous stasis. Ascitis.
- CT: complementary to echography
- MRI: tumoral thrombus extension
- Cavography: usually performed at the time of caval filter placement.
- EchoDoppler: portal hypertension (aspect of the liver, spleen, ascitis, collaterals, flow inversion of portal, superior mesenteric & splenic veins, portal thrombosis, portocaval shunt follow-up); Budd-Chiari, thrombosis of a renal vein, mesenteric artery stenosis, arcuate ligament compression, arterial thrombosis (mesenteric infarct), systemic hypertension (see renovasular hypertension).
- CT (if necessary, angio-CT, MR angiography): problem solving
- Arteriography, portography: problem solving + preoperative
workup; interventional radiology (dilatation, stents, embolisation,
shunts).
8. Gastrointestinal and posttraumatic haemorrhage:
- Arteriography: aneurysm, gastroduonenal ulcer, diverticulum, Meckel, arteriovenous malformation, angiodysplasia, tumor. Extravasation visible only if active bleeding > 0.5 ml/min. Selective embolisation possible.
- Scintigraphy: search of Meckel, locates bleeding source if oozing > 0.5 - 0.05 ml/min.
- If subacute, digestive examinations: endoscopy, CT colonography, barium enema/meal (not to be done before angiography), enteroclysis.
- EchoDoppler, CT: portal hypertension staging (oesophagial varices).
Pierre Bénédict, MD, FMH radiologist, Lausanne, 1997-2008
References:
- Eisenberg R.L., Margulis A.R.: "Radiology Pocket Reference: what to order when", Lippincott, 2nd ed., 1999
- ACR (American College of Radiology) guidelines
- Radiation protection 118: Referral guidelines for imaging (Office for official publications of the European Communities)
- Paul Rodriguez "MRI Indications for the Referring Physician", Aurora, 1997