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.

Frequency Range	Impact	Application
1 MHz to 3 MHz	Deep Tissue Imaging.	Deep structures like the liver, kidneys, and heart
3 MHz to 5 MHz	Provides a balance between penetration and resolution	General Abdominal and Obstetric Imaging
2.5 MHz to 5 MHz	Specifically chosen for adequate penetration and resolution	Cardiac Imaging (Echocardiography)
5 MHz to 10 MHz	Optimal for vascular imaging	Breast, thyroid, and vascular imaging
7.5 MHz to 15 MHz	Provides higher resolution images but less penetration depth	Musculoskeletal and Superficial Structures

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.

Acardia

Acardia is a rare and serious malformation that occurs exclusively in monizygous twins - twins developing from a single egg. Acardia represents one of the most severe and rare congenital anomalies. It is characterized by the absence of functioning heart. Acardia results from the artery to artery connections in the placenta, thereby causing a physically normal fetus to circulate blood for itself as well as a severely malformed fetus suffering from heart regression. In other words, fetus acardius is a parasite and it receives blood supply from the donor twin. Because the pump twin heart has to pump for two, there is a high risk of going into heart failure and this would lead to the death of the normal twin.

The most common variety is the acardius acephalus where the head is lacking and so are the upper extremities. Other types are acardius anceps, acardius acormus and acardius amorphous. While in acardius anceps, the most highly developed form, a partly developed head with remnants of cranial bones and brain tissue are present with developed body and extremities, acardius acormus is the rarest form of acardia. The monster is a head without a body. Acardia amorphous is the least developed monster not recognizable as a human form, with minimally developed visceral organs. Since there is no gross human form, the name acardius amorphous.

As to the cause of acardia, the etiology of acardiac monster is still unknown. Genetic defects have been reported to be the cause. Some researchers suggest chromosomal abnormalities to be the reason. Krause and Bejdl suggest that compression of the cephalic pole of the embryo prohibiting curving and fusion of the primitive heart tube to be the basic cause of this anomaly. As a result, the dependant entodermal organs like thyroid, esophagus, trachea, lung, liver and others are also not formed.

A pregnant woman carrying an acardiac twin is unlikely to have any unusual symptoms. An acardiac twin is often found incidentally on prenatal ultrasound. As no two acardiac twins are formed exactly alike, they may present differently. Several improved imaging techniques like 2D ultrasonography, 3D ultrasonography and transvaginal Doppler ultrasonography have made diagnosis of acardia possible even in the first trimester of pregnancy. Such early diagnosis helps to reduce the risk of complications. Fetal echocardiography is also recommended to assist in early detection of heart failure in the normal twin. Chromosome studies are also done on both fetuses.

One line of treatment is watching for the earliest signs of heart failure in the pump twin with frequent ultrasounds. If heart failure is identified and the pregnancy is also far enough, then the pump twin should simply be delivered. Physicians recommend prenatal interruption of the blood vessel connections before heart failure develops in the pump twin, thus sacrificing the acardiac twin.

Specialists use laser, electrical cauterization and electrodes, serial amniocentesis, medications and other treatments successfully. If the acardiac twin is large enough and the amount of blood flow to it can cause heart failure in the healthy twin, then blood flow is stopped with Fetal Image-Guided Surgery. The acardiac or parasitic twin never survives, as it is severely malformed and does not have a functioning heart. The normal twin is at risk for heart failure and complications associated with premature birth. The normal twin is expected to have about 10% risk for malformations.

Scleritis

Scleritis is a serious eye disease that refers to the inflammation of the sclera, the white outer portion of the eye. Sclera is made up of connective tissues and thus helps in protecting the eye. Sclera is also responsible for giving spherical shape to our eyes. When sclera develops inflammation it is termed as scleritis.

Normally scleritis occurs between the age of 30 and 60 and also scleritis affects women more than men. Scleritis is potentially damaging and may even cause permanent vision loss in severe cases. Most often scleritis is associated with other underlying auto immune diseases present in the body such as rheumatoid arthritis, Gout, Wegener granulomatosis to name a few. But in few cases the disease may occur without any underlying condition and in such instances, the cause remains unknown. Scleritis can occur in the front portion of the eye ball or the back part of the eye ball and they are known as anterior scleritis and posterior scleritis respectively. Anterior scleritis is further classified into Nodular scleritis, Diffuse scleritis, Necrotizing scleritis with inflammation and Necrotizing scleritis without inflammation.

In Nodular scleritis, tiny tender nodules form on the white portion of the eye. Diffuse scleritis refers to the inflammation of the front half of the sclera. This is the most common type of scleritis compared to other variations. Necrotizing scleritis is a serious form of scleritis and may even lead to vision loss. It is accompanied by severe pain and usually associated with the problem in other organs of the body. The sclera of the eye thins down severely and may occasionally result in perforation of the eye globe. This condition may surface with or without inflammation. Posterior scleritis is the rarest form of scleritis and usually presents itself with the symptoms like double vision, severe pain, retinal detachment, proptosis and restricted eye movement.

Diagnosis of Scleritis

Clinical examination of the eye is the first step towards assessing the scleritis disease. Further some eye tests and blood tests may be conducted to assess the severity and to diagnose the underlying disease that is causing the inflammation. Diagnostic procedures like ultrasonography and MRI may be advised if posterior scleritis is suspected.

Treatment of Scleritis

Firstly, oral anti inflammatory drugs are prescribed to control the inflammation and relieve the patient of the pain. In case of scleritis, topical eye drops alone are not sufficient to cure the inflammation. The main objective of the treatment would be to diagnose and treat the underlying disease that is causing the condition. In chronic cases, graft surgery may be performed to treat the injured portion of the eye.

Scleritis is treatable, but there are chances of this condition recurring again. The success rate of the treatment also depends upon the severity and the type of the scleritis. Necrotizing scleritis has low success rate and the incidence of vision loss is higher with this condition where as diffuse and nodular scleritis are easily treatable.

Tags: #Ultrasound #Acardia #Scleritis