Sir na Vascular Center
* Sirona is the Celtic Goddess of Health
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(415) 464-5400
"Everything about you depends on circulation." (Jack LaLanne)
About vascular imaging
Imaging can be very helpful for identifying the location and severity of vascular disease. We use imaging to help us decide if the disease is worrisome enough to mandate surgery and also to help with surgical planning. This is a summary of some of the imaging modalities we use frequently.
Ankle brachial index (ABI) and segmental studies

These are non-invasive tests to detect peripheral arterial disease (PAD), problems with blood flow to the legs. The ABI is a measurement of the blood pressure at the ankle compared with a blood pressure measurement in the arm. It is expressed as a ratio, so ABI=ankle pressure ÷ arm pressure. Normally, the ankle pressure should be the same as or slightly higher than the arm pressure, so ABI=1. If the ABI is less than 1, then there is likely to be artery disease present. ABI less than 0.6 indicates severe PAD, and ABI less than 0.3 indicates critical blood flow impairment which may warrant surgery. In some people, we may also do a toe-brachial index (TBI), with a cuff on the big toe. A segmental pressure test involves placing a series of blood pressure cuffs on the legs (high thigh,low thigh, high calf, ankle) to help determine where in the leg the artery disease might be. For instance, a significant pressure drop across the high thigh and low thigh cuffs in a leg might indicate a narrowing or blockage in the femoral artery that travels through the thigh from the groin to the knee.
These tests are performed in our Vascular Lab. There are no special instructions prior to the test. We want you to be relaxed and wearing comfortable clothing. Please arrive approximately 15 minutes prior to the procedure to register. You should take all of your regular medications and you do not need to fast. The test is performed by a registered vascular technician (RVT). For the test, you will need to remove pants because we will need access to your entire leg. Loose fitting shorts or skirt is acceptable. You will lay flat for the study and you will feel some pressure in your legs momentarily as the cuffs inflate. The study takes approximately 20 minutes. The exam findings will be sent to your physician. If Dr. Pak has ordered the study, you will discuss it with her at your next office visit. You will be notified immediately if there are any critical exam findings.
Arterial ultrasound of the legs or arms or abdomen, carotid ultrasound, graft study, aneurysm study

Ultrasound is a non-invasive imaging modality which works by sending sound waves through the body using a hand held transducer. The sound waves reflect off tissues in the body and the information generated is synthesized into images. This is the same technology that the obstetrician uses for accessing a a pregnancy. It involves no ionizing radiation (x-ray). We use arterial ultrasound for many reasons: to assess for the location and degree of narrowing (stenosis) in an artery, to check for re-narrowing in a bypass graft, to evaluate for aneurysm.
These tests are performed in our Vascular Lab. We want you to be relaxed and wearing comfortable clothing. Please arrive approximately 15 minutes prior to the procedure to register. You should take all of your regular medications. If you are having an abdominal ultrasound or aneurysm study, you will need to fast 6 hours prior to the procedure. Fasting reduces bowel gas, which can limit our ability to obtain adequate imaging. If you are having a leg or arm ultrasound or carotid study, you do not need to fast. The test is performed by a registered vascular technician (RVT). For the test, you will need to disrobe to allow us to image the area of interest. You will lay flat for the study and you will feel some light pressure as the transducer is applied to your skin. Most studies take approximately 20-40 minutes. The exam findings will be sent to your physician. If Dr. Pak has ordered the study, you will discuss it with her at your next office visit. You will be notified immediately if there are any critical exam findings.
Varicose vein ultrasound, DVT study, venous ultrasound

Ultrasound is a non-invasive imaging modality which works by sending sound waves through the body using a hand held transducer. The sound waves reflect off tissues in the body and the information generated is synthesized into images. This is the same technology that the obstetrician uses for accessing a a pregnancy. It involves no ionizing radiation (x-ray). We use venous ultrasound to assess for venous insufficiency which can produce varicose veins or leg edema, and to assess for clots.
These tests are performed in our Vascular Lab. We want you to be relaxed and wearing comfortable clothing. Please arrive approximately 15 minutes prior to the procedure to register. You should take all of your regular medications. You do not need to fast. The test is performed by a registered vascular technician (RVT). For the test, you will need to remove pants because we will need access to your entire leg to image the area of interest. For varicose vein ultrasounds, you will stand for the study so that we can evaluate the direction of flow in the veins to determine reflux. If you cannot stand or feel uncomfortable doing so, we will have you lay on the exam table and we will tilt it so that your legs are downward. You will feel some light pressure as the transducer is applied to your skin. Most studies take approximately 20-40 minutes. The exam findings will be sent to your physician. If Dr. Pak has ordered the study, you will discuss it with her at your next office visit. You will be notified immediately if there are any critical exam findings.
Computed tomography (CT) scan, or "cat scan"

Computed tomography angiography (CTA) is another way of imaging arteries. CT allows us to obtain 3D images and to clearly delineate degree of narrowing (stenosis). It also allows us to see the relationships of the arteries or veins to other structures, information which may be helpful in surgical planning; and it allows us to see some areas we cannot see by ultrasound (inside the brain, inside the chest). CTA involves ionizing radiation and use of contrast (xray dye). It also costs more than ultrasound. For this reason, we consider it a "higher power" study, not used for routine testing and surveillance. In general, we prefer CT to MRI for imaging of blood vessels.
CTs can be performed in the hospital or at an outside facility. You will need to have a blood test to measure your kidney function (creatinine) before you can have the scan. If your kidney function is impaired, you may be given additional instructions. Mucomyst is a medication we frequently prescribe to patients who have mild kidney impairment and require a CT scan. If you are allergic to iodinated contrast or to shellfish, please advise us. We may prescribe medication (steroids, diphenhydramine, H2 blocker) prior to the CT scan to reduce your risk of having an adverse reaction. You do not need to fast for vascular CT studies, and you will not need to drink a contrast agent. An intravenous (IV) line will be placed in your arm and then you will lie on a narrow bed. The bed will slide into a big "donut" which spins around you, acquiring images. You will be given instructions to hold your breath momentarily for the study. You will feel a transient warm sensation in your chest as the contrast agent goes through the IV; sometimes you may also feel like you need to urinate. The study generally takes about 10-15 minutes. Most people who have mild claustrophobia have no issues with the CT scan. If you feel that your claustrophobia is severe, you may need a light sedative for the study, and you will need someone to take you home afterwards.