AFP Test

AFP Test or Alpha-fetoprotein test is conducted on pregnant women to check the AFP level in the blood. The liver in the fetus produces AFP naturally. Determining the amount of AFP in the mother's blood will help identify any neural tube defect in the fetus. Neural tube defects arise in 2 out of every 1,000 pregnancies. AFP test also helps check for Down's syndrome. There are 60% chances for detecting Down's syndrome when the AFP levels are low in the blood. AFP can also be calculated from the sample of amniotic fluid of a pregnant woman. This screening test is generally performed between 16 and 18 weeks of pregnancy and is very sensitive between 15 and 17 weeks. The accuracy of the AFP test result lies in the exact age of the fetus. The AFT test is also referred to as maternal serum alpha-fetoprotein (MSAFP). AFP test is done on men and non-pregnant women too to confirm cancer in the testicles, stomach, pancreas, liver and the ovaries. High levels of AFP can indicate renal cell cancer.

Interpretation of AFP test results: In men and non-pregnant women, the values of the AFP test is 0-6.4 IU/mL (international units per milliliter), 0-20 nanograms per milliliter (ng/mL) or 0-20 micrograms per liter. In pregnant women of about 15 - 22 weeks gestation, the AFP results usually show 19-75 IU/mL, 7-124 ng/mL or 7-124 microgram per liter. AFP test values vary depending on the weight of the woman and race. Black women have higher values than white women and white women have higher values than Asian women. High AFP can suggest multiple pregnancies, fetus with neural tube defects, and abdominal wall defect in the fetus or fetal death. In non-pregnant adults, high AFP values mean cancer in the testicles or ovaries. High AFP can also indicate liver disease and bowel inflammation.

Chorionic Villus Sampling

The diagnostic procedure of taking out a sample tissue (Choroinic Villi) from the placenta to detect congenital abnormalities in a fetus is known as Chorionic Villus Sampling (CVS). With the guidance of ultrasound, the position of placenta is first determined. There are two methods - trans-cervical and trans-abdominal to perform this test. The position of the placenta helps the physician choose a suitable method. For trans-cervical CVS, parameters like the position of the uterus, the size of the gestational sac and the position of the placenta inside the uterus are first determined using abdominal ultrasound. Using a good antiseptic, the vulva, vagina and the cervix are cleansed. The abdomen is also cleansed for trans-abdominal procedure.

Trans cervical procedure: A thin plastic tube is inserted through the vagina and cervix for the trans-cervical procedure to reach the placenta. A tiny sample of chorionic villus tissue is taken out after locating the exact position of the placenta.

Trans-abdominal procedure: This procedure is similar to the earlier one, but a needle is inserted through the abdomen in this test to reach the uterus and then to the placenta. The chorionic villus sample tissue is drawn into the syringe, while the needle is guided by ultrasound.

This sample is then taken to the laboratory for evaluation. This procedure can be conducted even earlier than amniocentesis to detect any congenital defects present in the fetus. It is done at around 10 to 12 weeks after the last menstruation. Study of the DNA, chromosomes and enzymes of the fetus can be conducted using the sample taken out during the test. Results are available within a week or two. If there are any abnormalities found in the fetus, it is easy to conduct a therapeutic abortion, in case it is necessary. Pregnant women over the age of 35 who are at risk for giving birth to a baby with Downs Syndrome or those who have had birth defects in an earlier pregnancy are advised this test. For detecting neural tube defects and the Rh-incompatibility, amniocentesis is a better option. Hemoglobinopathies and Tay-Sachs disease can be detected through Chorionic Villus Sampling.

The risk involved in using CVS is slightly higher when compared to amniocentesis. Some complications like rupture of the amniotic membrane, miscarriage, infection, bleeding, Rh-incompatibility in the mother if she is Rh-negative and contamination of the sample with maternal cells can occur. When CVS is performed after 10 weeks of gestational period, there is a risk for limb defects in the fetus. If the mother's blood is Rh-negative, she has to receive Rho GAM to avoid Rh incompatibility. After the CVS, it is advised to have an ultrasound done after about two or four days to ensure the fetus is fine.

Ultrasound

Ultrasonography is a medical imaging technique that is also called ultrasound scanning or sonography. High frequency sound waves and their echoes and used in this technique for obtaining images from inside the human body. The echoes of sound waves reflected from the human body are recorded and displayed as a real-time visual image. This technique is similar to the echo location used by bats, whales and dolphins. The sonar used by submarines also operates with the same technique. Ultrasound is useful method to examine many of the body's internal organs like heart, liver, gallbladder, spleen, pancreas, kidneys and bladder.

Ultrasound Scanning

1. Sound Waves: A transducer (a small handheld device) emits high-frequency sound waves.
   
2. Echoes: These sound waves bounce off tissues, organs, and other structures inside the body.
   
3. Image Formation: The transducer detects the echoes and sends this information to a computer, which creates images based on the patterns of the echoes.
   

Types of Ultra sound:

1. Abdominal Ultra sound: Evaluates organs in the abdomen, such as the liver, gallbladder, spleen, pancreas, and kidneys.
   
2. Pelvic Ultra sound: Assesses reproductive organs (uterus, ovaries) and bladder.
   
3. Obstetric Ultra sound: Monitors pregnancy and fetal development, to assess the risk of fetal abnormalities such as neural tube defects or Down's syndrome
   
4. Cardiac Ultrasound (Echocardiogram): Evaluates heart structure and function.
   
5. Doppler Ultra sound: Measures blood flow through vessels.
   
6. Musculoskeletal Ultra sound: Examines muscles, tendons, and joints.
   
7. Thyroid Ultra sound: Evaluates the thyroid gland.
   

Preparation:

• Fasting: May be required for certain abdominal ultrasounds.
  
• Full Bladder: Often necessary for pelvic ultrasounds.
  
• Loose Clothing: Wear comfortable, loose-fitting clothes for easy access to the area being examined.
  

Procedure:

1. Preparation: The patient may be asked to lie on a table and expose the area to be examined.
   
2. Application of Gel: A special gel is applied to the skin to help transmit sound waves.
   
3. Transducer Use: The healthcare provider moves the transducer over the area, capturing images.
   
4. Image Review: The images are reviewed in real-time, and the provider may take multiple images from different angles.
   

Benefits:

• Non-Invasive: No needles or incisions.
  
• Safe: Uses sound waves, not radiation.
  
• Real-Time Imaging: Allows dynamic assessment of moving structures.
  
• Widely Available: Accessible in most healthcare settings.
  

Applications:

• Diagnosis: Identifying and evaluating various medical conditions.
  
• Monitoring: Tracking the progress of diseases or conditions.
  
• Guidance: Assisting in procedures such as biopsies or fluid drainage.
  

Common Uses:

• Pregnancy Monitoring: Checking fetal health and development.
  
• Organ Assessment: Evaluating the liver, kidneys, and other organs.
  
• Cardiac Evaluation: Assessing heart function and detecting abnormalities.
  
• Blood Flow Analysis: Checking for blood clots or poor circulation.
  
• Musculoskeletal Issues: Diagnosing tendonitis, bursitis, or tears.
  

Ultrasound examinations are versatile and essential tools in modern medical diagnostics, providing crucial information for the diagnosis and management of many health conditions.

Carotid Doppler ultrasound scanning is a diagnostic method used to assess blood flow through the carotid arteries, which are the primary vessels supplying the neck and head. This non-invasive modality is employed in the evaluation of various conditions, including:
1. Carotid artery stenosis (narrowing) - a common finding associated with increased risk of stroke. Doppler echocardiography image reveals any narrowing of the arteries or turbu￾lence in blood flow.
Echocardiography is a diagnostic tech￾nique used to evaluate structural and functional abnormalities of the heart including:
1. Heart wall: Detecting changes in thickness, texture or motion.
2. Heart chambers: Assessing size, shape, and function.
3. Heart valves: Evaluating valve leaflet movement, regurgitation and stenosis.
4. Large coronary arteries: Identifying narrowing or obstruction.
In addition to detecting cardiovascular lesions, echocardiography is also employed in the diagnosis of:
1. Congenital heart disease: Abnormalities present at birth.
2. Cardiomyopathy: Heart muscle disorders characterized by impaired function.
3. Aneurysms: Ballooning or dilation of the heart or blood vessel walls.
4. Pericarditis: Inflammation of the pericardial sac surrounding the heart.
5. Blood clots in the heart: Emboli that may have originated from other sources and traveled to the heart.

2. Transient ischemic attacks (TIAs), also known as "mini-strokes" or "warning strokes" - a temporary loss of blood flow to the brain.
3. Stroke - a neurovascular event characterized by permanent disruption of blood flow to the brain.
Doppler echocardiography is a valuable diagnostic tool that enables the measurement of blood flow velocity (speed) within the heart. This modality allows cardiologists to:
1. Assess structural abnormalities: Such as mitral valve prolapse, where the mitral valve leaflets protrude into the left ventricle.
2. Evaluate septal defects: Abnormal openings in the septum that separate the right and left sides of the heart.
By analyzing blood flow velocity, Doppler echocardiography can help diagnose and monitor various cardiovascular conditions, including those affecting the heart valves and septum.

Cataract Surgery: An ultrasound probe is inserted into the lens capsule through a small incision in the cornea. The incision is made using a diamond tipped instrument. The ultrasound probe softens the lens by emitting sound waves. It then sucks out the softened lens tissue. Only the front part of the lens capsule is removed.

Doppler ultrasound is a type of echocardiography that utilizes the principles of Doppler shift to measure the velocity of moving structures. This technique involves transmitting high-frequency ultrasonic waves from an emitter and detecting the frequency changes resulting from the interaction with moving targets, such as blood flowing through a blood vessel.
Doppler ultrasonography has become a widely accepted diagnostic modality for detecting various vascular conditions. Specifically, it is commonly employed to:
1. Identify arterial narrowing or stenosis in the neck, often resulting from atherosclerosis (the accumulation of fatty deposits on artery walls).
2. Detect blood clots (thrombi) within veins, as seen in deep vein thrombosis.
In addition to its vascular applications, Doppler ultrasound is also used for:
1. Fetal monitoring: To non-invasively assess fetal heart rate and detect any potential abnormalities.
2. Dialysis and cardiopulmonary bypass procedures: To monitor for air emboli (air bubbles) that may form during these interventions.
3. Blood pressure measurement: As a non-invasive means to estimate blood pressure, particularly in situations where direct measurement is not possible or practical.
The process begins with the emission of pulses of ultrasound at a specific frequency. As these pulses interact with moving objects, such as red blood cells in a vessel, the frequency of the reflected signals (echoes) shifts due to the Doppler effect. A sensor detects these frequency changes and converts them into meaningful data, providing valuable information about the velocity or flow characteristics of the target structure, for example, blood flow through an artery or vein.

Ancillary term used in ultrasound imaging to describe an anechoic region or structure that does not produce any reflective echoes (sonographic signals) when exposed to ultrasound waves. This is typically seen in structures containing clear fluid, such as:
1. Cysts: Fluid-filled cavities that do not reflect ultrasound signals.
In these cases, the lack of echogenicity allows for better visualization and differentiation from surrounding tissues.
"Echogenic" - A descriptive term used in ultrasound imaging to identify structures that produce reflective echoes or signals when exposed to ultrasound waves. In other words, an echogenic structure is one that generates a strong sonographic signal, allowing it to be visualized and characterized on the ultrasound image.

The frequency of ultrasound waves used in medical imaging varies depending on the type of examination and the depth of the tissue being imaged. Here are some general guidelines:

Common Frequencies:

1. General Diagnostic Ultrasound:
   • Frequencies typically range from 2 MHz to 15 MHz.
     
   
   
2. Abdominal Ultrasound:
   • Lower frequencies around 2 MHz to 5 MHz.
     
   • Lower frequencies provide deeper penetration but lower resolution.
     
   
   
3. Pelvic Ultrasound:
   • Frequencies typically in the range of 3 MHz to 7.5 MHz.
     
   
   
4. Obstetric Ultrasound:
   • Frequencies around 2 MHz to 5 MHz for deeper penetration to view the fetus.
     
   
   
5. Cardiac Ultrasound (Echocardiogram):
   • Frequencies typically range from 2.5 MHz to 5 MHz.
     
   
   
6. Vascular Ultrasound:
   • Frequencies around 5 MHz to 10 MHz.
     
   
   
7. Musculoskeletal Ultrasound:
   • Higher frequencies around 7.5 MHz to 15 MHz.
     
   • Higher frequencies provide better resolution for superficial structures.
     
   
   
8. Small Parts (Thyroid, Breast, Scrotal):
   • Frequencies in the range of 7.5 MHz to 15 MHz.
     
   
   

• Penetration vs. Resolution: Lower frequencies penetrate deeper into the body but produce images with lower resolution. Higher frequencies provide higher resolution images but do not penetrate as deeply.
  
• Tissue Characteristics: Different tissues reflect sound waves differently, so the frequency is chosen based on the specific characteristics and location of the tissue being examined.
  

Specific Frequency Ranges:

1. 2-3.5 MHz: Deep structures like the liver, kidneys, and heart.
   
2. 3.5-5 MHz: General abdominal and obstetric imaging.
   
3. 5-7.5 MHz: Breast, thyroid, and vascular imaging.
   
4. 7.5-10 MHz: Musculoskeletal and superficial structures.
   
5. 10-15 MHz: Very superficial structures and detailed imaging of small parts.
   

Normally the term ultrasound refers to frequencies above 20 kHz (the maximum frequency a human can hear), medical ultrasound utilizes frequencies in the range of several MHz to achieve the necessary balance between resolution and penetration for effective imaging of different tissues and organs.

As you can see from the table above, specific band of frequencies are chosen for optimal imaging.

• Resolution: Higher frequencies provide better resolution, allowing for more detailed images of tissues and structures.
  
• Penetration: The choice of frequency is a trade-off between penetration and resolution. Lower frequencies penetrate deeper but have lower resolution, while higher frequencies provide detailed images of superficial structures.
  

Movement of the internal tissues and organs are captured in ultrasound. Ultrasonography enables the physicians to diagnose a variety of disease conditions and also assess the damage caused to the systems. The ultrasound machine transmits high frequency sound pulses into the human body by using probes. These sound waves that travel into the body hit a boundary between the tissues inside the body and reflect the sound waves to the probe. Some waves travel even further and they reach another boundary and then get reflected back. The waves that are reflected are picked up by the probe and relayed back into the ultrasound machine.

The ultrasound machine in turn calculates the distance from the probe to the tissue or organ by using the speed of sound tissue and the time of each echo's return. The machine displays these distances and intensities of the echoes on the screen. Through the echoes that are produced the sonologist can identify how far away an object is, how large it is, its shape and consistency (fluid, solid or mixed). Two dimensional images are formed and reflected on the screen. Different types of ultrasound are used for different disease conditions. Ultrasound is used in a variety of clinical settings including obstetrics and gynecology, cardiology and cancer detection.