COMPUTARISED TOMOGRAPHY

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COMPUTARISED TOMOGRAPHY MAGNETIC RESONANCE IMAGING
DR MANOJ ABHANG MD PART II
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CT SCAN

• IMPORTANT POINTS
• A noninvasive, painless medical tests that helps
  physcians to
• diagnose treat medical conditions
• 2) A system of x ray tube detectors are made
  to rotate
• around the part of body being scanned
• 3) X rays are received by the detectors whitch
  are coupled
• With a photomultiplier tube computer
• 4) Result cross sectional image of part
  giving excellent
• spatial contrast resolution
• 5) Most images done in axial plane therefore
  earlier term
• computed axial tomography

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1) The CT scanner is typically a large machine
with a hole, or tunnel, in the center. 2)
A moveable examination table slides into and out
of this tunnel. 3) In the center of the
machine, the x-ray tube and electronic
x-ray detectors are located opposite each
other on a ring, called a gantry, which rotates
around you. 4) The computer that processes
the imaging information and monitor are
located in a separate room.
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• Physicians often use the CT examination to
• Plan and properly administer radiation
• treatments for tumors
• 2) Guide biopsies and other minimally invasive
• procedures plan surgery
• 3) Measure bone mineral density for the detection
  
• of osteoporosis
• 4) Quickly identify injuries to the liver,
  spleen,
• kidneys or other internal organs in cases of
  
• trauma

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WORKING OF CT SCAN 1) CT scanning works very
much like other x-ray examinations. 2)
X-rays are a form of radiationlike light or
radio wavesthat can be directed at the
body. 3) Different body parts absorb the x-rays
in varying degrees. 4) With CT scanning,
numerous x-ray beams and a set of
electronic x-ray detectors rotate around
you, measuring the amount of radiation being
absorbed throughout your body. 5) At the same
time, the examination table is moving
through the scanner, so that the x-ray beam
follows a spiral path.
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7) A special computer program processes
this series of pictures, or slices of your body,
to create two-dimensional cross-sectional
images, which are then displayed on a
monitor.
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CT slice through the mid-abdomen showing multiple
normal-appearing organs, which are labeled.
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CT scan showing the liver
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CT scan of a normal appendix in the right lower
abdomen. The appendix normally connects with the
right colon and contains air (this appears black
on the scan). Air in the appendix excludes
appendicitis since this means that the appendix
is not obstructed or inflamed.
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CT angiogram. Frontal or coronal view of chest-3D
slab image showing pulmonary vessels.
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A 3D reconstructed CT view of the kidneys and
ureters, which connect the kidneys to the
bladder. Part of the ribs, spine and pelvis are
included in this image
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Comminuted Fracture of the left hip on 3D CT
Reconstruction.
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Benefits -CT scanning is painless, noninvasive
and accurate. -A major advantage of CT is that
it is able to image bone, soft tissue and blood
vessels all at the same time. -Unlike
conventional x-rays, CT scanning provides very
detailed images of many types of tissue as well
as the lungs, bones, and blood vessels. and
simple in emergency cases, they can reveal
internal injuries and bleeding quickly enough to
help save lives. -CT has been shown to be a
cost-effective imaging tool for a wide range of
clinical problems.
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-CT may be less expensive than MRI. In addition,
it is less sensitive to patient movement. -CT
can be performed if you have an implanted medical
device of any kind, unlike MRI. -CT imaging
provides real-time imaging, making it a good tool
for guiding minimally invasive procedures such as
needle biopsies and needle aspirations of many
areas of the body, particularly the lungs,
abdomen, pelvis and bones. -A diagnosis
determined by CT scanning may eliminate the need
for exploratory surgery and surgical biopsy.
-No radiation remains in a patient's body after
a CT examination. -X-rays used in CT scans
usually have no side effects.
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• Risks
• -There is always a slight chance of cancer from
  radiation.
• However, the benefit of an accurate diagnosis far
  outweighs the risk.
• -The effective radiation dose from this procedure
  is about 10 mSv, which is about the same as the
  average person receives from background radiation
  in three years.
• -Women should always inform their physician or
  x-ray technologist if there is any possibility
  that they are pregnant.
• -CT scanning is, in general, not recommended for
  pregnant women because of potential risk to the
  baby.
• -Nursing mothers should wait for 24 hours after
  contrast material injection before resuming
  breast-feeding.

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-The risk of serious allergic reaction to
contrast materials that contain iodine is rare,
and radiology departments are well-equipped to
deal with them. -Children should have a CT
study only if it is essential for making a
diagnosis and should not have repeated CT studies
unless absolutely necessary.
LIMITATIONS Very fine soft-tissue
details in areas such as the knee or shoulder can
be more readily and clearly seen with magnetic
resonance imaging (MRI). The exam is not
generally indicated for pregnant women.
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MRI

• 1) Magnetic resonance imaging (MRI) uses
  radiofrequency waves and a strong magnetic field
  rather than x-rays to provide remarkably clear
  and detailed pictures of internal organs and
  tissues.
• 2) The technique has proven very valuable for the
  diagnosis
• of a broad range of pathologic conditions in
  all parts of the body including cancer, heart and
  vascular disease, strokes, and joint and
  musculoskeletal disorders.
• MRI requires specialized equipment and expertise
  and
• allows evaluation of some body structures
  that may not be
• as visible with other imaging methods.

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• 4) Hydrogen atom has single proton in its
  nucleus is the most abundant element in the
  body, used commonly in vivo imaging
• 5) T1 is the measure of time required for the
  protons in a
• substance to become magnetized after being
  placed in a
• magnetic field
• Water Csf black- Hypointense
• Fat white hyperintense
• 6) T2 involves the loss of magnetization in
  transverse plane
• 7) By using different imaging techniques such as
  spin echo,
• inversion, recovery partial saturation
  contrast between
• lesions adjacent normal tissues organs
  can be increased or decreased
• 8) Intensity MRI
• Density CT
• ECHO Ultrasound

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7) By using different imaging techniques such as
spin echo, inversion, recovery partial
saturation contrast between lesions adjacent
normal tissues organs can be increased or
decreased 8) Intensity MRI Density
CT ECHO Ultrasound
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WORKING OF MRI 1) Instead radiofrequency
waves are directed at protons, the nuclei of
hydrogen atoms, in a strong magnetic field. 2)
The protons are first "excited" and then
"relaxed," emitting radio signals that can be
computer-processed to form an image. 3) In the
body, protons are most abundant in the hydrogen
atoms of waterthe "H" of H2O so that an MR
image show differences in the water content and
distribution in various body tissues. 4) Even
different types of tissue within the same organ,
such as the gray and white matter of the brain,
can easily be distinguished. Typically an MRI
examination consists of two to six imaging
sequences, each lasting two to 15 minutes.
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5) Each sequence has its own degree of contrast
and shows a cross-section of the body in one of
several planes (right to left, front to back,
upper to lower).
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MR of the knee - side (lateral) view, showing
distal or lowest part of femur, the patella
(knee cap) and proximal (upper) tibia. The
lateral meniscus is seen as a dark bow-tie like
structure. The patellar tendon is also clearly
seen at the front of the knee connecting the
patella with the tibia.
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MR image of the pelvis of a woman shows the
uterus (arrow) and ovaries (arrowhead).
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MR of the right shoulder looking at rotator cuff
and head of humerus as well as glenoid portion
of scapula.
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MRI of the sternum, ribs and portions of both
breasts, looking at the patient from the front.
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MRI of the chest. Patient is lying on his back.
Lungs are black, aorta and pulmonary arteries
are grey, shoulder muscles are grey and fat under
the skin is white on this sequence.
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• Benefits
• Images of the soft-tissue structures of the
  bodysuch as the heart, lungs, liver and other
  organsare clearer and more detailed than with
  other imaging methods.
• 2) MRI can help physicians evaluate the function
  as well as the structure of many organs.
• 3) The detail makes MRI an invaluable tool in
  early diagnosis and evaluation of tumors.
• 4) MRI contrast material is less likely to
  produce an allergic
• reaction than the iodine-based materials used
  for conventional x-rays and CT scanning.

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5) MRI enables the detection of abnormalities
that might be obscured by bone with
other imaging methods. 6) MRI provides a fast,
noninvasive alternative to x-ray
angiography for diagnosing problems of the heart
cardiovascular system. 7) Exposure to
radiation is avoided.
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Risks - An undetected metal implant may be
affected by the strong magnetic field. - MRI
is generally avoided in the first 12 weeks of
pregnancy. Doctors usually use other methods
of imaging, such as ultrasound, on pregnant
women unless there is a strong medical reason
to use MRI.
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• LIMITATIONS
• -Bone is better imaged by conventional x-rays in
  some cases and CT is preferred for patients with
  severe bleeding.
• -MRI may not always distinguish between tumor
  tissue and
• edema fluid and does not detect calcium when
  this is present within a tumor.
• -In most cases the examination is safe for
  patients with metal
• implants, with the exception of a few types of
  implants,so patients should inform the technician
  of an implant prior
• to the test.
• The examination must be used cautiously in early
  pregnancy.
• MRI typically costs more than CT scanning.

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• ADVANTAGE OF MRI OVER CT SCAN X-RAY
• DIRECT MULTIPLANER IMAGING IN CORONAL, SAGITTAL
  AXIAL ORIENTATION
• 2) NO ARTEFACTS DUE TO BONE EDGES, DENTAL
  FILLINGS, SURGICAL CLIPS
• 3) SUPERIOR SOFT TISSUE CONTRAST
• 4) IMPROVED TISSUE CHARACTRRIZATION
• 5) NO IONISING RADIATION OR KNOWN BILOGICAL
• ILL-EFFECTS
• 6) MR MYELOGRAPHY IS DONE WITHOUT USE OF
  CONTRAST MATERIAL

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7) MR ANGIOGRAPHY IS DONE WITHOUT USE OF
CONTRAST MATERIAL 8) BOTH STATIC REAL TIME
IMAGES CAN BE OBTAINED