Task8: Medical Imaging

X-Rays

An X-ray, also known as radiography, is a medical imaging technique. It uses tiny amounts of electromagnetic radiation to create images of structures inside the body. These images can then be viewed on film or digitally.

X-rays often are done to view bones and teeth, making them helpful in diagnosing fractures (broken bones) and diseases such as arthritis. A healthcare provider may also order an X-ray to look at organs and structures inside the chest, including the lungs, heart, breasts, and abdomen.

The tiny particles of electromagnetic radiation that an X-ray machine emits pass through all but the most solid objects in the body. As such, the image it creates, known as a radiograph, allows healthcare providers to visualize internal structures in your body.

Sometimes a contrast medium, a type of dye, is given to help images appear in greater detail. You might receive these via injection into a blood vessel, orally, or rectally.

X-ray images appear in various shades of white and grey. Because bones and metal objects are solid, less radiation passes through them, making them appear white on the radiograph. On the other hand, skin, muscle, blood and other fluids, and fat are grey because they allow the most significant amount of radiation to pass through.

Areas where there is nothing to stop the beam of radiation, such as air, or even a fracture, appear black compared to surrounding tissue.

When It's Used

X-ray technology is used for a multitude of purposes. For example, they can help healthcare providers evaluate symptoms and diagnose injuries.

Among the most common reasons X-rays include:

Identifying fractures
Identifying infections in bones and teeth
Diagnosing cavities and evaluating structures in the mouth and jaw
Revealing bone tumors
Measuring bone density (the amount of mineral in your bones) to diagnose osteoporosis (a bone disease caused by bone loss)
Finding evidence of pneumonia, tuberculosis, or lung cancer
Looking for signs of heart failure or changes in blood flow to the lungs and heart
Revealing problems in the digestive tract such as kidney stones, sometimes using a contrast medium called barium
Locating swallowed items such as a coin or tiny toy

CT Scan

Computed tomography—sometimes referred to as a CT scan, CAT scan, or computerized axial tomography—involves the use of multiple X-ray images that are translated by a computer and converted to form a three-dimensional image. This allows healthcare providers to look at an organ, injury, or growth from different angles. A CT scan allows for more insightful analyses than other imaging tests without the need for invasive interventions. It is used for a wide variety of reasons, such as detecting tumors, identifying blood clots, assessing a bone fracture, and more.

When It's Used

CT scanning of the abdomen may be used to identify masses in the liver, kidney, or pancreas, or to search for causes of bleeding in the urinary tract (hematuria).
CT scanning of the cardiovascular system can be used to map the flow of blood (CT angiography) and to help diagnose kidney disorders, aortic aneurysm, atherosclerosis, or pulmonary edema.
CT scanning of the heart can help diagnose and monitor coronary artery disease (CAD) or aid in valve replacement surgery.
CT scanning of the head and brain may be used to look for tumors, hemorrhage, bone trauma, blood flow obstruction, and brain calcification (commonly seen in people with Parkinson's disease and dementia).
CT scanning of the lungs can help detect changes in the lung architecture as a result of fibrosis (scarring), emphysema, tumors, atelectasis (collapsed lung), and pleural effusion.
CT scanning of the skeletal system can aid in the diagnosis of a spinal cord injury, pathologic fractures, bone tumors, or lesions, and to help evaluate a complex fracture, osteoporosis, or joint damage caused by arthritis.

MRI

Magnetic resonance imaging (MRI) is a pain-free, noninvasive medical test used to produce two- or three-dimensional images of the structures inside your body using a strong magnetic field and radio waves. MRI gives detailed views of your organs, tissues, and skeleton, which can be used to help diagnose and monitor a wide variety of medical conditions.

An MRI scan allows your healthcare team to see the internal structures of your body without making an incision via detailed, high-resolution images. All areas of the body can be scanned from any direction or angle using MRI technology, which means this test can be used for both the diagnosis and monitoring of many health conditions.

MRI can be ordered with or without contrast. Contrast medium is a liquid that's injected into your bloodstream through an IV and can allow more detailed images to be obtained. To provide healthcare providers with a point of comparison, many patients have an MRI scan without contrast immediately followed by another with contrast.

When It's Used

Brain and spinal cord conditions such as multiple sclerosis (MS), stroke, brain or spinal cord injuries, brain aneurysms, tumors, and brain injuries
Tumors or abnormalities in organs like the liver, spleen, pancreas, reproductive organs, kidneys, bile ducts, bladder, heart, bowel, and adrenal glands
Heart and blood vessel structure issues, such as the abnormal size of aortic chambers, damage from a heart attack or heart disease, inflammation, blockages, congenital heart disease, aneurysms, and other heart problems
Inflammatory bowel diseases like Crohn's disease or ulcerative colitis
Liver diseases like cirrhosis
Breast cancer
Joint and bone irregularities, tumors, abnormalities, and infections

PET Scan

Positron emission tomography (PET) is a type of imaging technology used to evaluate how your tissues and organs work at the cellular level. It involves the injection of a short-acting radioactive substance, known as a radiotracer, which is absorbed by biologically active cells. You are then placed in a tunnel-like device that is able to detect and translate the emitted radiation into three-dimensional images. By identifying abnormalities in the metabolism of a cell, a PET scan can diagnose and assess the severity of a wide range of diseases, including cancer, heart disease, and disorders of the brain.

A PET scan is commonly used to stage cancer, to evaluate the extent of damage following a heart attack or stroke, and to monitor your response to cardiovascular, neurological, or cancer treatments.

PET differs from CT and MRI in that it examines the function, rather than the structure, of living cells. By contrast, CT and MRI are used to detect damage caused by a disease. In essence, PET looks at how your body responds to a disease, while computed tomography (CT) and magnetic resonance imaging (MRI) look at the damage caused by one.

Among its many functions, PET can measure blood flow, oxygen intake, how your body uses glucose (sugar), and the speed by which a cell replicates. By identifying abnormalities in cellular metabolism, a PET scan can detect the early onset of a disease well before other imaging tests.

When It's Used

PET is primarily used to diagnose cancer, cardiovascular disease, and neurologic disorders.

For cancer, PET is especially useful as it can scan the entire body and pinpoint both a primary tumor and areas of metastasis (where the cancer has spread). With that being said, not all cancers can be detected by PET.

Those that can include:

Brain cancers
Cervical cancer
Colorectal cancer
Esophageal cancer
Head and neck cancers
Hodgkin or non-Hodgkin lymphoma
Lung cancer
Melanoma
Pancreatic cancer
Prostate cancer
Thyroid cancer

For cardiovascular disease, a PET scan can reveal areas of decreased blood flow to the heart, brain, or lungs. By viewing the effects of circulatory impairment, your healthcare provider can make the most appropriate treatment choice, including angioplasty or cardiac bypass surgery.

PET can also help predict the likelihood of a heart attack or stroke by detecting and measuring the hardening of arteries (atherosclerosis).

Among the cardiovascular conditions the test can diagnose:

Cardiac infections
Cardiac sarcoidosis
Congestive heart failure (CHF)
Coronary artery disease (CAD)
Pulmonary embolism
Pulmonary sarcoidosis
Stroke

For neurologic disorders, a PET scan can be used to measure brain activity in relation to areas of high and low radioactivity. Since the brain requires large amounts of glucose and oxygen to function, any shortages can easily be detected on a scan.

Among the neurologic disorders a PET can help diagnose:

Alzheimer disease
Brain hematomas (blood clots)
Brain tumors
Dementia
Epilepsy
Huntington disease
Multiple sclerosis
Parkinson's disease

In addition, PET can be used to detect bacterial infections, most specifically enterobacterial types associated with endocarditis, septic arthritis, osteomyelitis, and central nervous system infections.

Ultrasound

An ultrasound is a non-invasive medical technique that makes use of high-frequency sound waves. It’s best known for its use during pregnancy as the primary method to visualize fetuses developing in the womb. Medical ultrasound falls into two broad categories: diagnostic and therapeutic.

Diagnostic ultrasound, also known as sonography or ultrasonography, use sound to image organs and structures inside of the body, helping to diagnose medical issues. Images produced by diagnostic ultrasound are called sonograms. During a diagnostic ultrasound, you are positioned on a medical table so the part of your body being imaged is accessible. Your doctor or a technician will apply a water-based gel, which helps transmit sound waves, to your skin over the area that needs to be visualized. Your doctor will then guide a handheld device, called a transducer, over the gelled skin. The transducer sends into the body a directed beam of sound waves with frequencies above human hearing (above 20 KHz), which reflect back off of tissues and organs. The transducer analyzes these echoes and converts them into sonograms that are displayed on a monitor.

Diagnostic ultrasound can image a wide range of internal structures, including the heart and blood vessels, liver, and thyroid, among others.

When It's Used

Evaluate and identify the source of pain, swelling, and infections
Diagnose heart conditions
Detect tumors
Evaluate issues that affect blood flow, such as narrowed blood vessels and clots
Guide invasive procedures, including needle biopsies and needle-based anesthesiology
Detect brain abnormalities in newborns

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