Doppler Ultrasound - Uses, Types, Preparation, and Procedure

Introduction:

Doppler ultrasound or Doppler ultrasonography is a medical imaging technique that uses sound waves to detect the details of blood flow inside the blood vessels. Doppler ultrasound is a special ultrasound technique in which the sound waves are audible during the scan. It is useful for the detection of the speed and direction of blood flow. The movement of the blood cells causes a change in pitch of the reflected sound waves (Doppler effect). The images are processed as graphs or color pictures on the computer. Normal ultrasound shows only the structures of the organs but cannot show the blood flow.

How Does Doppler Ultrasound Work?

Ultrasound is a diagnostic tool that captures the images of soft tissues inside the body using sound waves. Ultrasound imaging is also called a sonogram. During the Doppler ultrasound, a handheld probe called the transducer produces high-frequency sound waves that reach the organs, which bounce back and are received by the transducer. The transducer processes the reflected waves, which are then converted by the computer into images of the blood vessels. It has the ability to show the structure and movement of the internal structures. It can also show blood flowing through the blood vessels.

The sound waves travel at different speeds in various tissues. It can travel fastest through bone tissue and slowest through the air. The speed of the sound waves and the amount of the sound waves returned to the transducer determine the types of tissue.

What Are the Uses of Doppler Ultrasound?

Doppler ultrasound is useful in the following conditions:

• Determine the function and abnormalities of the heart, such as congenital heart disease.

• Detect the blocked blood vessels.

• Determine the narrowing of blood vessels.

• Evaluate the blood flow after surgery.

• To detect the enlarged artery (aneurysm).

• Determine the blood flow in pregnant women and the fetus in the womb.

• Detects the blood flow to the brain after a stroke.

• Follow-up scan in patients who had treatment for blood flow disorders.

Sometimes, the doctors may recommend a Doppler ultrasound for a person who is having any of the following symptoms:

• Numbness in the legs.

• Color change in the skin over the legs.

• Cramps and pain in the leg and hip muscles when walking.

• Feeling cold in the lower part of the legs or foot.

• Difficulty in breathing.

• Swelling of the legs, feet, or abdomen.

What Are the Different Types of Doppler Ultrasound?

• Color Doppler- Color Doppler is a doppler imaging in which the blood vessels appear as colored structures on the screen. This is used to determine the speed and direction of the blood flow.

• Power Doppler - This is recommended when the images are difficult to obtain with color doppler. It is used to obtain accurate details of the blood flow in the blood vessels located inside the organs.

• Spectral Doppler- This is an ultrasound imaging that measures the blood flow velocity and displays them as a graphical representation on the screen.

• Duplex Doppler - Duplex Doppler is used for detecting the blood flow through the arteries and veins and also provides the details of the surrounding tissues.

• Continuous-Wave Doppler- It is used to determine the gradient, pressure, and blood flow in the vessels of the heart.

How Do Patients Prepare for a Doppler Ultrasound?

• Patients are instructed to remove any objects or clothes that interfere with the scan and wear the apron provided by the technician.

• For Doppler abdomen ultrasounds, patients are instructed not to eat or drink for several hours before the test.

• For pelvic Doppler ultrasound, patients are advised to drink 32 ounces (0.9 liters) of water an hour before the scan. To get effective pelvic images, patients have to fill their bladder before the test.

• For an abdomen scan, the health provider may give an enema (a medicine used to clean your bowel) to the patient before the scan.

• Avoid tobacco products such as cigarettes two hours before the procedure. The nicotine in tobacco products causes narrowing of the blood vessels, which affects the test result.

What Are the Best Positions for Doppler Ultrasound at Different Locations?

• For chest and abdomen scans, the patient may be asked to lie back and neck extended for a chest doppler ultrasound.

• For examining the blood vessels of the leg and arm, patients are asked to lie back with their heads raised. The arm or leg will be facing outwards. Sometimes, for leg scans, they are asked to lie on their stomach.

• Pregnant women are asked to lie on their left side with their abdomen exposed for a doppler ultrasound.

How Is the Doppler Ultrasound Performed?

• For a Doppler ultrasound, patients will be asked to lie down on a flat table. The radiologist or diagnostic medical sonographer will apply a water-soluble gel over the skin of the target area, which will be imaged. This gel may feel cool, and it does not cause any pain. The radiologist will gently move a probe called a transducer over the skin on top of the gel. They move the probe back and forth to get the images clearly.

• Patients may need to change their body positions to look at different areas and, for a few seconds, be asked to hold their breath to get better images. After that, they will wipe off the gel over the skin.

• To detect the abnormalities of the artery, blood pressure cuffs are tied over different parts of the body, such as the thigh, calf, ankle, and different areas of the arms. This blood pressure cuff is used to compare the blood pressure at various points of the legs and arms.

• Though the abnormalities are found in one arm or leg, a Doppler ultrasound is performed in both the legs or arms to compare the results. This procedure usually takes about 60 minutes or less.

• After the scan, the radiologist reviews the images and sends the report to the physician. Patients can continue their regular activities immediately after the test.

What Are the Factors That Influence the Doppler Ultrasound Result?

• Obesity.

• Presence of intestinal gas (a mix of odorless vapors, including oxygen, nitrogen, carbon dioxide, hydrogen, and methane).

• Movement of the patient during the scan.

• Heart disease and arrhythmias (abnormally increased heartbeat).

• Open wound in the examination site.

What Health Conditions Does Doppler Ultrasound Help to Diagnose?

The health conditions that can be diagnosed using Doppler ultrasound are

• Narrowed nervous system.
• Injuries to the blood vessels.
• Presence of blood clots.
• Presence of tumor in blood vessels.
• CVI (chronic venous insufficiency).
• Hypertension caused due to renal vascular causes.

What Are The Risks Associated With Doppler Ultrasound?

Doppler ultrasound is a low-risk and noninvasive test. It does not include any injectable contrast dyes or use of any form of radiation such as X-rays or CT (computed tomography). Ultrasound procedures are less harmful without any pain.

Conclusion:

Doppler ultrasound is a non-invasive diagnostic tool that detects the blood flow within the blood vessels efficiently. This scan uses only soundwaves and does not require radiation or contrast materials for the imaging process. It is easy to use and less expensive when compared to other imaging techniques for blood vessels, such as angiography (a procedure used to look at the blood vessels of the heart with the help of imaging techniques). Doppler ultrasound scan is completely safe for pregnant women, especially for pregnant women having preeclampsia (high blood pressure in pregnancy) or sickle cell anemia (a disease in which the shape of the red blood cells is altered). This scan is occasionally uncomfortable, but it is not painful.