Question: What procedure is used to generate pictures of veins?
About the article "Magnetic resonance imaging", section "Magnetic resonance angiography".

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Magnetic resonance angiography (MRA) generates pictures of the arteries to evaluate them for stenosis (abnormal narrowing) or aneurysms (vessel wall dilatations, at risk of rupture).
MRA is often used to evaluate the arteries of the neck and brain, the thoracic and abdominal aorta, the renal arteries, and the legs (called a "run-off").
A variety of techniques can be used to generate the pictures, such as administration of a paramagnetic contrast agent (gadolinium) or using a technique known as "flow-related enhancement" (e.g., 2D and 3D time-of-flight sequences), where most of the signal on an image is due to blood that recently moved into that plane, see also FLASH MRI.
Techniques involving phase accumulation (known as phase contrast angiography) can also be used to generate flow velocity maps easily and accurately.
Magnetic resonance venography (MRV) is a similar procedure that is used to image veins.
In this method, the tissue is now excited inferiorly, while the signal is gathered in the plane immediately superior to the excitation plane—thus imaging the venous blood that recently moved from the excited plane.
Superficial vein is a vein that is close to the surface of the body.
This differs from deep veins that are far from the surface.
Superficial veins are not paired with an artery, unlike the deep veins, which typically have an artery with the same name close by.
Superficial veins are important physiologically for cooling of the body.
When the body is too hot the body shunts blood from the deep veins to the superficial veins, to facilitate heat transfer to the surroundings.
Superficial veins can be seen under the skin.
Those below the level of the heart tend to bulge out.
An immediate way to see this by looking at your hand: raise it above your heart and the blood should drain--lower it below your heart it will fill.
Veins become more visually prominent when lifting heavy weight, especially after a period of proper strength training.
Physiologically, the superficial veins are not as important as the deep veins (as they carry less blood) and are sometimes removed in a procedure called vein stripping, which is used to treat varicose veins. 
Injecting the unwanted veins with a sclerosing solution causes the target vein to immediately shrink, and then dissolve over a period of weeks as the body naturally absorbs the treated vein.
Sclerotherapy is a non-invasive procedure taking only about 10 minutes to perform.
The downtime is minimal, in comparison to an invasive varicose vein surgery.
Sclerotherapy is the "gold standard" and is preferred over laser for eliminating large spider veins (telangiectasiae) and smaller varicose leg veins.
Unlike a laser, the sclerosing solution additionally closes the "feeder veins" under the skin that are causing the spider veins to form, thereby making a recurrence of the spider veins in the treated area less likely.
Multiple injections of dilute sclerosant are injected into the abnormal surface veins of the involved leg.
The patient's leg is then compressed with either stockings or bandages that they wear usually for two weeks after treatment.
Patients are also encouraged to walk regularly during that time.
It is common practice for the patient to require at least two treatment sessions separated by several weeks to significantly improve the appearance of their leg veins.
Sclerotherapy can also be performed using microfoam sclerosants under ultrasound guidance to treat larger varicose veins, including the great and small saphenous veins.
After a map of the patient's varicose veins is created using ultrasound, these veins are injected whilst real-time monitoring of the injections is undertaken, also using ultrasound.
The sclerosant can be observed entering the vein, and further injections performed so that all the abnormal veins are treated.
Follow-up ultrasound scans are used to confirm closure of the treated veins, and any residual varicose veins can be identified and treated. 
Radiofrequency ablation is a minimally invasive procedure used in the treatment of varicose veins.
It is an alternative to the traditional stripping operation.
Under ultrasound guidance, a radiofrequency catheter is inserted into the abnormal vein and the vessel treated with radio-energy, resulting in closure of the involved vein.
Radiofrequency ablation is used to treat the great saphenous vein, the small saphenous vein, and the perforator veins.
The latter are connecting veins that transport blood from the superficial veins to the deep veins.
Branch varicose veins are then usually treated with other minimally invasive procedures, such as ambulatory phlebectomy, sclerotherapy, or foam sclerotherapy.
Currently, the VNUS ClosureRFS stylet is the only device specifically cleared by FDA for endovenous ablation of perforator veins.
It should be pointed out that the possibility of skin burn during the procedure is very small, because the large volumes (500 cc) of dilute Lidocaine (0.1%) tumescent anesthesia injected along the entire vein prior to the application of radiofrequency provide a heat sink that absorbs the heat created by the device.
Early studies have shown a high success rate with low rates of complications. 
Sclerotherapy is a procedure used to treat blood vessels or blood vessel malformations (vascular malformations) and also those of the lymphatic system.
A medicine is injected into the vessels, which makes them shrink.
It is used for children and young adults with vascular or lymphatic malformations.
In adults, sclerotherapy is often used to treat spider veins, smaller varicose veins and hemorrhoids.
Sclerotherapy is one method, along with surgery, radiofrequency and laser ablation, for treatment of spider veins, occasionally varicose veins, and venous malformations.
In ultrasound-guided sclerotherapy, ultrasound is used to visualize the underlying vein so the physician can deliver and monitor the injection.
Sclerotherapy is often done under ultrasound guidance after venous abnormalities have been diagnosed with duplex ultrasound.
Sclerotherapy under ultrasound guidance and using microfoam sclerosants has been shown to be effective in controlling reflux from the sapheno-femoral and sapheno-popliteal junctions.
However, some authors believe that sclerotherapy is not suitable for veins with reflux from the greater or lesser saphenous junction, or veins with axial reflux.