Ultrasound (USG)

What is ultrasound (USG), and how does it work?

 

Ultrasound (US) is a structural imaging technique that uses high-frequency mechanical ultrasound waves (with frequencies greater than audible sound waves) to create real-time tomographic (cross-sectional) images. A hand-held transducer is applied to a part of the body to transmit ultrasound waves into the patient. Reflected ultrasound waves (echoes) are then detected by the transducer and processed by a computer to create digital images that can be viewed or recorded.

 

 Clinical Applications Of Ultrasound

 

USG  is often used for initial evaluation of the abdominal organs (e.g., to evaluate for acute cholecystitis and choledocholithiasis), the pelvic organs (e.g., to evaluate for uterine leiomyomas, ovarian torsion, ectopic pregnancy, endometrial abnormalities, prostate cancer, and testicular torsion), the vessels (e.g., to evaluate for carotid artery stenosis and femoral vein deep venous thrombosis), the thyroid and parathyroid glands (e.g., to assess for thyroid nodules and parathyroid adenomas), and the joints (e.g., to assess for rotator cuff tears) and to serve as a real-time imaging guide during percutaneous biopsies. As US does not involve the use of ionizing radiation, it is also used during pregnancy (e.g., to evaluate the embryo/fetus for congenital anomalies) and in the pediatric setting (e.g., to evaluate  the brain and hip joints in infants).

 

Properties of ultrasound waves

 

1. They travel in straight direction.

 

2. They cannot travel in air or vacuum, bones.

 

3. When these collide with hard material, these comeback and produce white image.

 

4. These can partially travel from soft objects which produce lighter image.

 

5. These completely pass from liquid area and produce black image.

 

 

Advantages of ultrasound

 

1. It is not expensive.

 

2. It is not irratative and painless.

 

3. It is not erosive and non invasive.

 

4. It does not damage tissues of the body.

 

5. It gives 100% accurate result if technician is expert.

 

 

Preparation of patient for ultrasound

 

Preparation of the patient for the ultrasound examination depends upon the structure OR region that is examining.

 

1. Examination of patient should be on empty stomach (in fasting state from 6 To 8hours).it will have two benefits, i.e

 

1. On empty stomach the intestine will empty from gases and the underlying organs e.g pancreas will examine clearly.

 

1. in case of gall bladder examination(u/sound) G.B will be full from bile, and full G.B is good for examination, and any pathology if present is easily detectable.

 

2. Physical exercise.

 

3. Intake of water helps in the ultrasound of urinary bladder.

 

 

 

Positioning of the patient for ultrasound

 

Usually patient is examined when it is in supine position, scans in lateral decubitus and prone positions may be necessary and useful in some conditions Esp. In obese patients OR patients with skeletal deformities, the following positions may helpful for specific examinations:-

 

1. Hyper extension of the neck for the thyroid gland scanning (u/s).

 

2. Upright position for the evaluation of the pancreas to scan.

 

3. Prone position for the kidneys Esp. the left kidney.

 

4. Turning slightly to the left to evaluate the hilum of the liver, CBD and head of the pancreas.

 

5. Evaluation of pelvic to scan if small in size.

 

Guidelines for ultrasound examination.

 

Ultrasound examination must be done by trained person, and the following rolls should be respected:-

1. Make sure that the setting of the equipment’s is correct.

 

2. Know the history and the problems of the patient.

 

3. Do systemic examination of the body regions of interest according to the signs & symptoms.

 

4. Move the probe in a slow constant pattern, and hold probe motionless during the movements of the patient.

 

5. Use anatomically constant for scanning e.g RHC for liver & G.B etc.

 

6. Examine each organ or mass in at least two planes.

 

7. Utilize palpation to displace fluid-or-gas filled-bowels, to test the consistency of tumors and organs, and to localize points of pain.

 

8. Continue the examination even if pathologies (abnormalities) are found in early examination (scanning).

 

9. Check equipment setting again if findings is questionable

 

10. Repeat the examination within a short time in clinically difficult situations.

 

11. Ask the patient about the past Lab investigations, X-rays, u/sound and their findings/result/impression. it will become a plus point for you and you should focus that point of abnormality.

 

 

Terms used in ultrasound examination.

 

1. Echogenicity:- The ability of an organ to produce white image.

 

2. Echogenic:– The organ which produce white image is called echogenic e.g. Liver, Kidney

 

3. Hyperechoic/echogenic:- When waves pass from hard materials they cannot penetrate, collide with them and comeback to ultrasound machine and produce white image which is called hyperechoic.

 

4. Hypoechoic:- When waves pass from soft object, these partially penetrates and some collides which comeback to ultrasound machine and produce half white and half black image, which is called hypoechoic.

 

5. Anechoic:- When waves pass from fluids, these completely penetrate through them and no wave reflect back to ultrasound machine and produce black image which is called anechoic.

 

6. Isoechoic:- The image in which there is no differentiation between the echogenicity of two organs.

 

7. Homogenous:- The structure which produce uniform picture (echogenicity) are homogenous organs e.g Liver, thyroid gland etc.

 

8. Heterogenous:- the structures which do not produce uniform picture are called heterogenous they has mixture of bright

 

 

FAQs.

 

 

Q. Why is gel used in Ultrasound ?

Gel is applied between the transducer and skin to displace air and minimize large reflections that would interfere with ultrasound transmission from the transducer into the patient and vice versa. Reflections tend to occur at tissue interfaces where there are large differences in the speed of propagation of ultrasound waves, such as at air/soft tissue and bone/soft tissue interfaces. Gel decreases such reflections at the skin surface by matching the acoustic impedances of the transducer surface and skin surface.

 

Q. What is ultrasound?

Ultrasound is a medical imaging technique that uses high-frequency sound waves to create images of the inside of the body.

 

Q. How does ultrasound work?

Ultrasound works by sending sound waves into the body, which bounce off internal structures and return as echoes. These echoes are then used to create images.

 

Q. Is ultrasound safe?

Yes, ultrasound is considered safe because it does not use ionizing radiation like X-rays or CT scans.

 

Q. What is the purpose of an ultrasound scan?

Ultrasound is used to visualize and diagnose various medical conditions, monitor pregnancies, and guide medical procedures.

 

Q. Does ultrasound hurt?

No, ultrasound is a painless procedure.

 

Q. Are there any risks associated with ultrasound?

Generally, there are no known risks associated with ultrasound. It is non-invasive and does not use radiation.

 

Q. What are the different types of ultrasound exams?

There are various types, including abdominal, pelvic, transvaginal, obstetric, and cardiac ultrasounds.

 

Q. How should I prepare for an ultrasound?

Preparation instructions may vary, but typically, you’ll be asked to fast or drink water before certain exams.

 

Q. Can ultrasound detect cancer?

Ultrasound can help detect tumors and abnormalities, but it may not always distinguish between benign and cancerous growths.

 

Q. What is a transducer in ultrasound?
–

A transducer is the handheld device that sends and receives ultrasound waves. It is placed on the body to create images.

 

Q. What is Doppler ultrasound used for?

Doppler ultrasound measures blood flow and is commonly used to assess vascular conditions and monitor pregnancies.

 

Q. How long does an ultrasound exam take?

The duration of an ultrasound exam varies depending on the type and purpose, but it typically ranges from 15 minutes to an hour.

 

Q. Can ultrasound be used during pregnancy?

Yes, ultrasound is commonly used during pregnancy to monitor the health and development of the fetus.

 

Q. Is 3D/4D ultrasound different from regular ultrasound?

Yes, 3D and 4D ultrasounds provide three-dimensional or real-time images, offering more detailed views of the fetus.

 

Q. Can ultrasound be used to diagnose heart conditions?

Yes, echocardiograms (cardiac ultrasound) are used to assess heart function and detect heart conditions.

 

Q. Can ultrasound determine the gender of a baby?

In some cases, ultrasound can reveal the gender of a fetus, usually during the second trimester.

 

Q. Are there any limitations to what ultrasound can detect?

Ultrasound may not provide clear images in cases of obesity or when air or bone obstructs the view.

 

Q. What is a sonogram?

A sonogram is a still image or picture produced by an ultrasound exam.

 

Q. Can ultrasound diagnose gallstones?

Yes, ultrasound is an effective tool for diagnosing gallstones and gallbladder issues.

 

Q. Are there any age restrictions for ultrasound exams?

There are no specific age restrictions for ultrasound; it can be used on patients of all ages.

 

Q. How is a transvaginal ultrasound different from a regular abdominal ultrasound?

A transvaginal ultrasound involves placing a probe into the vagina for a closer view of pelvic organs, while an abdominal ultrasound is done externally on the abdomen.

 

Q. Can ultrasound detect kidney stones?

Yes, ultrasound can detect the presence of kidney stones.

 

Q. Can ultrasound diagnose liver disease?

Yes, ultrasound is often used to assess liver size and detect liver abnormalities.

 

Q. What is a fetal ultrasound anomaly scan?

It’s a detailed ultrasound during pregnancy to check for any fetal abnormalities or developmental issues.

 

Q. Are there any specific risks to fetal ultrasounds?

Fetal ultrasounds are generally safe, but excessive use should be avoided.

 

Q. Can ultrasound be used for guided biopsies or aspirations?

Yes, ultrasound-guided procedures are common for taking tissue samples or draining fluid from the body.

 

Q. Can ultrasound detect blood clots?

Yes, ultrasound can be used to detect blood clots in veins, such as deep vein thrombosis (DVT).

 

Q. Is there a difference between a radiologist and a sonographer?

Yes, a radiologist interprets ultrasound images, while a sonographer performs the ultrasound exam.

 

Q. Can ultrasound be used to monitor the progression of pregnancy?

Yes, multiple ultrasounds throughout pregnancy help monitor fetal growth and development.

 

Q. How soon can you get an ultrasound during pregnancy?

An ultrasound can be performed as early as 5-6 weeks into pregnancy to confirm viability and estimate due dates.

 

BOOK LINK:- Understanding Ultrasound Physics