Diagnostic Methods: Ultrasound, CT, and MRI

Prepared by-

Md. Bashir UddinAssistant Professor

Dept. of BMEKUET, Khulna-9203

Diagnostic Methods

UltrasoundUltrasound is an oscillating sound pressure wave with a frequency greater than the upper limit of the human hearing rangeUltrasound devices operate with frequencies from 20 kHz up to several gigahertz.Ultrasound is used in many different fields, such as-

To detect objects and measure distances In Ultrasonic imaging (sonography) In Nondestructive testing of products and structures To detect invisible flaws In Cleaning and mixing Locating prey and obstacles To change the chemical properties of substances

Ultrasound

Ultrasound ImagingUltrasound is safe and painless, and produces pictures of the inside of the body using sound waves. Ultrasound imaging, also called ultrasound scanning or sonography, involves the use of a small transducer (probe) and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through the gel into the body.

The transducer collects the sounds that bounce back and a computer then uses those sound waves to create an image.

Ultrasound examinations do not use ionizing radiation (as used in x-rays), thus there is no radiation exposure to the patient. Because ultrasound images are captured in real-time, they can show the structure and movement of the body's internal organs, as well as blood flowing through blood vessels.Ultrasound imaging is a noninvasive medical test that helps physicians diagnose and treat medical conditions

Ultrasound Imaging

Ultrasound is used to help physicians evaluate symptoms such as:

painswellinginfection

Ultrasound is a useful way of examining many of the body's internal organs, including but not limited to the:

Ultrasound Imaging

LiverGallbladderSpleenPancreasKidneysBladderheart and blood vesselsthyroid and parathyroid glandsuterus, ovaries, and unborn child (fetus) in pregnant

PatientsEyesscrotum (testicles)brain in infantships in infants

Ultrasound Imaging

Benefits:Most ultrasound scanning is noninvasive (no needles or injections).Occasionally, an ultrasound exam may be temporarily uncomfortable, but it is almost never painful.Ultrasound is widely available, easy-to-use and less expensive than other imaging methods.Ultrasound imaging is extremely safe and does not use any ionizing radiation.Ultrasound scanning gives a clear picture of soft tissues that do not show up well on x-ray images.Ultrasound is the preferred imaging modality for the diagnosis and monitoring of pregnant women and their unborn babies.Ultrasound provides real-time imaging, making it a good tool for guiding minimally invasive procedures such as needle biopsies and fluid aspiration

Limitations:Ultrasound waves are disrupted by air or gas; therefore ultrasound is not an ideal imaging technique for air-filled bowel or organs obscured by the bowel. In most cases, barium exams, CT scanning, and MRI are the methods of choice in such a setting.Large patients are more difficult to image by ultrasound because greater amounts of tissue attenuates (weakens) the sound waves as they pass deeper into the body.Ultrasound has difficulty penetrating bone and, therefore, can only see the outer surface of bony structures and not what lies within (except in infants who have more cartilage in their skeletons than older children or adults). For visualizing internal structure of bones or certain joints, other imaging modalities such as MRI are typically used.

Ultrasound Imaging

Computerized Tomography (CT)

Computerized/Computed tomography (CT scan) — also called CT or x-ray CT — combines a series of X-ray views taken from many different angles and computer processing to create cross-sectional images of the bones and soft tissues inside your body.In some cases, CT images can be combined to create 3-D images. CT scan images can provide much more information than do plain X-rays. A CT scan has many uses, but is particularly well suited to quickly examine people who may have internal injuries from car accidents or other types of trauma. A CT scan can be used to visualize nearly all parts of the body.

Computerized Tomography (CT)

X-ray computed tomography (x-ray CT) is a technology to produce tomographic images (virtual 'slices') of specific areas of the scanned object, allowing the user to see inside without cutting.Medical imaging is the most common application of x-ray CT. Its cross-sectional images are used for diagnostic and therapeutic purposes in various medical disciplines.As x-ray CT is the most common form of CT in medicine and various other contexts, the term computed tomography alone (or CT) is often used to refer to x-ray CT, although other types exist (such as positron emission tomography [PET] and single-photon emission computed tomography [SPECT]). Older and less preferred terms that also refer to x-ray CT are computed axial tomography (CAT scan) and computer-aided/assisted tomography.

Computerized Tomography (CT)

Computerized Tomography (CT)Advantages:There are several advantages that CT has over traditional 2D medical radiography. First, CT completely eliminates the superimposition of images of structures outside the area of interest. Second, because of the inherent high-contrast resolution of CT, differences between tissues that differ in physical density by less than 1% can be distinguished. Finally, data from a single CT imaging procedure consisting of either multiple contiguous or one helical scan can be viewed as images in the axial, coronal, or sagittal planes, depending on the diagnostic task. This is referred to as multiplanar reformatted imaging.

Adverse Effect:The radiation used in CT scans can damage body cells, including DNA molecules, which can lead to cancer.

Magnetic resonance imaging (MRI) is a technique that uses a magnetic field and radio waves to create detailed images of the organs and tissues within your body.Most MRI machines are large, tube-shaped magnets. When you lie inside an MRI machine, the magnetic field temporarily realigns hydrogen atoms in your body. Radio waves cause these aligned atoms to produce very faint signals, which are used to create cross-sectional MRI images — like slices in a loaf of bread.The MRI machine can also be used to produce 3-D images that may be viewed from many different angles.In many cases, MRI gives different information about structures in the body than can be seen with an X-ray, ultrasound, or computed tomography (CT) scan. MRI also may show problems that cannot be seen with other imaging methods.

Magnetic Resonance Imaging (MRI)

Magnetic resonance imaging (MRI) is done for many reasons. It is used to find problems such as tumors, bleeding, injury, blood vessel diseases, or infection. MRI also may be done to provide more information about a problem seen on an X-ray, ultrasound scan, or CT scan. Contrast material may be used during MRI to show abnormal tissue more clearly. An MRI scan can be done for the:

Magnetic Resonance Imaging (MRI)

•Head•Chest•Blood vessels

•Abdomen and pelvis•Bones and joints•Spine

It is a noninvasive diagnostic scanning technique

MRI provides a better contrast between normal and abnormal tissue than the CT scan.

The procedure lasts between 60 and 90 minutes.

Magnetic Resonance Imaging (MRI)

Benefits:•Provide very detailed diagnostic pictures of most of the important organs and tissues in body•Sometimes able to show unique information that other tests are unable to show•Generally painless•Do not use radiation and are therefore suitable for use in children and pregnant women.

Risks:Safety studies have found no long-term negative effects from MRI scans.•MRI scan is done in an enclosed space, so the people who are claustrophobic, i.e. fearful of being in a closely enclosed surface, are facing problems with MRI to be done.•MRI scans involve really loud noises while processing because they involve a really high amount of electric current supply.•MRI scans can cause heart pacemakers, defibrillation devices and cochlear implants to malfunction.

Magnetic Resonance Imaging (MRI)