Download 10 - KUET

Diagnostic Methods:
Ultrasound, CT, and MRI
Prepared byMd. Bashir Uddin
Assistant Professor
Dept. of BME
KUET, Khulna-9203
Diagnostic Methods
In medicine, a diagnostic test or method is any kind of
medical test performed to aid in the diagnosis or detection of
disease.
For example, such a test may be used to confirm that a
person is free from disease, or to fully diagnose a disease,
including to sub-classify it regarding severity and
susceptibility to treatment.
Some of diagnostic methods are:
Ultrasound Imaging
CT Scan
MRI
etc
Ultrasound
Ultrasound is an oscillating sound pressure wave with a
frequency greater than the upper limit of the human hearing
range
Ultrasound 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 Imaging
Ultrasound 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 Imaging
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 is used to help physicians evaluate symptoms
such as:
pain
swelling
infection
Ultrasound Imaging
Ultrasound is a useful way of examining many of the body's
internal organs, including but not limited to the:
Liver
Patients
Gallbladder
Eyes
Spleen
scrotum (testicles)
Pancreas
brain in infants
Kidneys
hips in infants
Bladder
heart and blood vessels
thyroid and parathyroid glands
uterus, ovaries, and unborn child (fetus) in pregnant
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
Ultrasound Imaging
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.
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)
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:
•Head
•Chest
•Blood vessels
•Abdomen and pelvis
•Bones and joints
•Spine
Magnetic Resonance Imaging (MRI)



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.