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Specialized Tech Flashcards

1
Q

Basic Ideas of Imaging

A

 To measure and map a useful
property of the human tissues.
 Non-invasive or minimally-
invasive.

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2
Q

Reflection

A

Photography,
ultrasound

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3
Q

Transmission

A

X-rays

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4
Q

Radiation

A

Pet/spect

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5
Q

Computed Tomography developed in

A

1971
by Dr. Godfrey N. Hounsfield &was used to image the
brain (Hounsfield, 1980)

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6
Q

Originally all scans were done in the axial plane ,thus
leading to the name

A

‘Computerized Axial Tomography
“or CAT Scan .

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7
Q

Axial as initial scans are done and these image scan be
reformatted and viewed in the

A

Axial as initial scans are done and these image scan be
reformatted and viewed in the Coronal plane , Sagittal
plane .

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8
Q

The CT x-ray system

A

(the gantry) consists of the x-ray source (fan-shaped beam),
radiation detectors and data-acquisition system.

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9
Q

Image Display:
 As so called

A

Image Display:
 As so called Soft
Tissue Window is
used to better
visualize the soft
tissues and the Bone
Window is used to
better visualize the
bone tissue.

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10
Q

Image display in term of

A

2 window

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11
Q

CT scans are mainly
performed in the

A

CT scans are mainly
performed in the Axial
plane.
 The Coronal and Sagittal
cuts can then be calculated
(reconstructed) by the
computer.
 Direct coronal and Sagittal
cuts can be also performed
but they require different
patient positioning.

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12
Q

Indications of CT in the Head and
Neck:

A
  1. Assessment of tumour size, site and extent, for both
    benign and malignant tumours affecting the jaw bones,
    maxillary antra, or base of the skull.
  2. Investigation and assessment of extent of any suspected
    intracranial and spinal cord damage following trauma to
    the head and neck.
  3. Detection of the extent of any diseases in the paranasal
    sinuses and their extension into the orbit or base of the
    skull.
  4. Investigation of any TMJ pathosis or abnormalities.
  5. Investigation of the Salivary Glands and detection of any
    intrinsic or extrinsic swellings.
  6. Pre-operative assessment of jaw bones height and
    thickness before inserting Implants.
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13
Q

Advantages of C.T.:

A
  1. Imaging of Hard and Soft tissues.
  2. The sensitivity of the detector combined with the power of
    the computer makes it possible to discriminate between
    objects with small differences in density such as blood
    and fat or blood and cerebrospinal fluid.
  3. Images can be enhanced by the use of intravenous (IV)
    contrast media, providing additional information.
  4. Images can be reformatted to another plane without the
    necessity of another scan .Some CT scanners can image
    the mandible and the maxilla on one scan .
  5. Eliminates the superimposition of images of structures
    superficial or deep to the area in question (Tomography
    ), and this can be done in any plane.
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14
Q

Disadvantages of C.T.:

A

The details of a computed tomographic
image are not as fine as in conventional
radiography due to the pixel size which
is greater than the size of the silver
specks that form the image in
conventional radiographs.
2. Metallic objects such as amalgam
fillings produce streak artifacts across
the CT image.
3. The equipment is expensive.
4. Increase radiation dose when compared
with conventional film.

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15
Q

method was introduced that may
prove to be more efficient and economical than
either conventional tomography or CT for oral
diagnosis .

A

(Cone Beam CT ){(CBCT

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16
Q

CBCT uses a

A

CBCT uses a round or rectangular cone shaped x-
ray beam centered on 2 &3D x-ray sensor to scan
360 rotations about patients head.
The patient is imaged in normal seated position
as in conventional tomography

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17
Q

Advantages of CBCT :

A

 The scan times usually range between 17
sec. to little more than 1 min.
 Excellent image quality :
 High resolution
 Reduction of artifacts
 Distortion free
 Excellent contrast resolution
 User friendly software making acquisition and
image display simple and accurate

Low radiation dose
 less expensive than CT .
 It has already been in use in implant therapy.
 It helps in clinical assessment of bone graft quality
following alveolar surgery in patients with cleft lip and
palate

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18
Q

These investigations use contrast media

A

II. Contrast Studies

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19
Q

Contrast Media are:

A

Radiopaque substances that have been
developed to alter artificially the density
of different parts of the patient i.e.
altering subject contrast.
 Certain organs, structures and tissues,
invisible using conventional means can be
seen.

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20
Q

Contrast studies include:

A

 Sialography – Salivary Glands
 Arthrography– Joints
 Angiography– Blood Vessels
 Lymphography– Lymph Nodes and Vessels
 Urography– Kidneys
 Barium swallow, meal– GI Tract

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21
Q

Contrast media:
 Types:

A

Barium sulphate
Iodine-based aqueous solutions
Iodine-based oil solutions
MR contrast agents

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22
Q

suspensions for GIT investigations.

A

Barium sulphate

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23
Q

Iodine-based aqueous solutions

A

water soluble) used for all
other investigations e.g. Urografin

24
Q

Iodine-based oil solutions

A

used for lymphography and
sialography e.g. Lipiodol

25
Q

MR contrast agents e.g

A

gadolinium.

26
Q

Contrast media Patients at risk:

A

 Patients at risk:
1. The elderly and very young children.
2. Patient with history of allergy to contrast media.
3. Diabetes, cardiac failure, renal failure or severe pulmonary
disorders.

27
Q

Sialography: is

A

radiographic demonstration of the
major salivary glands by introducing a
radiopaque contrast medium into their
ductal system.

28
Q

Ideal Requirements of Contrast Media
used in Sialography:

A
  1. They must posses sufficient radio-opacity provide
    good delineation of the anatomic structures.
  2. It must have proper viscosity, not very high as it will
    need excessive pressure upon injection, and not very
    low as it will escape the gland and will need repeated
    injections.
  3. It must be readily excreted from the glands.
  4. It must be non toxic and non-harmful to the tissues.
29
Q

Sialography Procedures:
 Preoperative phase:

A

 Taking preop. (scout) radiographs:
 Parotid gland– lat. oblique, PA and ant. parotid view using
occlusal film
 Submandibular gland– lat. oblique, cross-sectional mandibular
occlusal and panoramic
 Patient preparation:

30
Q

Sialography Procedures: Filling phase:

A

 Introducing the contrast medium through a canula in gland duct
orifice
 Taking the filling phase radiographs.

31
Q

Emptying or evacuation phase: sialography

A

 Removal of canula and allowing excretion of contrast media
 Taking radiographs after 5minutes
 Radiographs can be used to assess gland function

32
Q

Indications: of sialography ospe

A
  1. Chronic inflammation of Salivary Glands (sialectasis):
     Obstructive inflammation:
     calculi (sialolithiasis)– RL stone
     strictures (constriction of the ductal wall near the
    orifice)
     stenosis (constriction of the ductal wall along the
    whole course of the main duct).
     Non-obstructive inflammation:
     auto-immune diseases as Sjogren’s disease
     bacterial infections as acute suppurative parotitis
    or recurrent parotitis
     viral infections as mumps
     inflammation secondary to allergic reactions.
    2.Neoplasms of salivary glands :
     extrinsic tumours (there is normal architecture of the
    gland and its secretary function but there is just
    deviation of the ducts due to external pressure of the
    tumour)
     intrinsic tumour (arising from the gland itself); which
    may be benign (encapsulated) or malignant
    3.Trauma of salivary glands :
     Trauma → haemorrhage → displacement of the gland
    → occlusion by scarring and fibrosis → accumulation
    of saliva and contrast media → sialocele.
    4.Metabolic diseases of salivary glands : e.g. diabetes
    mellitus
33
Q

Contraindications: of sialography

A
  1. Allergy to compounds containing iodine.
  2. Periods of acute inflammation when there is discharge of
    pus from the duct opening because injection may result in
    disruption of the epithelium with spread of infection.
  3. When pre-operative radiographs show a calculus close to
    the duct opening as injection may push the calculus back
    down the main duct where it may be inaccessible.
  4. Patients performing thyroid function test using iodine-
    containing materials as there will be interference between
    the iodinated contrast media of sialography and those of
    the thyroid test resulting in false results of the test so the
    test has to be done first followed by sialography.
34
Q

Radiograph modality of soft tissue

A

Diagnostic ultrasound is now established as the first
choice imaging modality for soft tissue investigations
of the face and neck, particularly of the salivary
glands.

35
Q

Frequency of us

A

It is a non-invasive investigation that uses a very high
frequency (7.5-20 MHz) pulsed ultrasound beam to
produce high resolution images of more superficial
structures.
 The use of colour power Doppler allows blood flow to be
detected.

36
Q

Us image called

A

If the ultrasound wave is not reflected
but is absorbed by the tissues, no image
will result.
 Air, bone and other calcified
materials absorb nearly all the
ultrasound beam so its diagnostic use
is limited in these tissues. resultant image is
a real-time black, white and grey visual echo picture.
 It is also a sectional image or tomography that represents a topographical map of the depth of tissue interfaces.

37
Q

Utilization of Doppler effect

A

Utilization of Doppler effect– a change in the frequency
of sound reflected from a moving source – allows the
detection of arterial and/or venous blood flow.
 Adding appropriate colour to the vascular structures in the
echo picture image makes differentiation between
structures straightforward.

38
Q

Indications in the Head and Neck:

A
  1. Examination of Salivary Glands:
     US is valuable in detecting obstructing lesions of S.Gs such as
    calculi, cystic lesions and neoplasms.
     Benign lesions appear homogenous with US and have a smooth
    outline whereas the sonographic appearance of malignant
    lesions is of rough and ill-defined margins.
    It is the best method for differentiating between solid and
    cystic lesions.
  2. Examination of swellings of the neck including lymph nodes and
    thyroid gland.
  3. Examination of soft tissues as the lips, cheek and tongue.
  4. Examination of the maxillary sinus:
     It is effective in distinguishing between normal sinus,
    chronically inflamed sinus and a sinus obliterated with a tumour
    or a fluid.
  5. Assessment of blood flow in the carotid artery thus aiding in
    detecting any thrombosis of the carotids as well as carotid body
    tumours.
39
Q

It is the best method for differentiating between solid and
cystic lesions.

A

Us

40
Q

Advantages: of us

A
  1. Sound waves are not ionizing radiation so it is a
    non-invasive technique and is not harmful to the
    tissues.
  2. Shows good differentiation between different
    soft tissues.
  3. Shows good differentiation between solid and
    cystic lesions of salivary glands and neck
    swellings.
  4. It is a painless technique.
  5. It is widely available, rapidly performed and
    inexpensive.
41
Q

Disadvantages:of us

A
  1. It has limited use in the head and neck
    area because sound waves are absorbed by
    bone.
  2. Technique is very operator-dependent.
  3. Images can be difficult to interpret for
    inexperienced operators because image
    resolution is very poor.
42
Q

another specialized modality that does not
involve the use of ionizing radiation. Felix Bloch and Edward M. Purcell
independently describe the nuclear magnetic
resonance (NMR) phenomenon.

A

Mri

43
Q

Mri used for

A

Used for imaging intracranial and soft tissue
lesions.

MRI modality that uses the
response of biologic tissues to an
applied and changing magnetic
field to generate images.
 This current is detected by a
computer and converted into a
visual image.
Uses hydrogen atom

44
Q

Indication of mri in head and neck

A

Tumour staging: evaluation of the size,
site and extent of soft tissue tumours and
tumour-like lesions.
 Investigation of the TMJ to show the hard
and soft tissue components of the joint
including the disc.
 Assessment of intra-cranial lesions.

45
Q

Advantages of mri

A
  1. Ionizing radiation is not used. No adverse effects
    from MRI have ever been reported.
  2. High-resolution images can be reconstructed in
    all planes.
  3. Excellent differentiation between soft tissue is
    possible and between normal and abnormal
    tissues.
  4. Metallic (amalgam) restorations do not produce
    artifacts on the final image as with CT images.
46
Q

Disadv of mri

A

 Cortical bone is not imaged, signal
obtainable only from bone marrow.
 Scanning time is long and very annoying to
the patient.
 Equipment is very expensive.
 Patients with pacemakers can not be
imaged.

47
Q

Radioisotope Imaging
(Nuclear Medicine also called

A

Scintigraphy )

48
Q

Scintigraphy

A

It relies upon altering the patient by making
the tissues radioactive and the patient
becoming the source of ionizing
radiation.
 Done by injecting certain radioactive
compounds into the patient that have an
affinity for particular tissues – Target
Tissues.

49
Q

Radioisotope camera

A

Radioactive compounds
become concentrated in the
target tissue and their
radiation emission are the
detected and imaged,
usually using a stationary
gamma camera.
 This investigation allows
the function and/or the
structure of the target tissue
to be examined under both
static and dynamic
conditions.

50
Q

Radioisotopes :
 Typical examples used in conventional nuclear medicine
include:

A

Technetium (99mTc)– according to its attachment to
different substances .

51
Q

Indication for conventional isotope
imaging in head and neck

A
  1. Tumour staging– assessment of the sites
    and extent of bone metastases.
  2. Investigation of salivary gland function.
  3. Evaluation of bone grafts.
  4. Assessment of continued growth in
    condylar hyperplasia.
  5. Investigation of the thyroid.
  6. Brain scans.
52
Q

Advantages: for conventional isotope

A
  1. Target tissue function is investigated.
  2. All similar target tissues can be examined
    during one investigation e.g. the whole
    skeleton in one bone scan.
  3. Computer analysis and enhancement of
    results are available.
53
Q

Disadv of conventional isotope

A
  1. Poor image resolution– minimal
    information about anatomy.
  2. Relatively high radiation dose.
  3. Images are not usually disease-specific.
  4. Difficult to localize exact anatomical site
    of source of emission.
  5. Some investigations take several hours.
  6. Not widely available.
54
Q

This enables the exact anatomical site of the
source of the emissions to be determined.

A

Single Photon Emission Computed
Tomography (SPECT)

55
Q

Spect

A

Gamma rays emitted from the patient are detected
by a gamma camera rotating around the
patient.
 The distribution of radioactivity is displayed as a
cross-sectional image or SPECT scan.
 This enables the exact anatomical site of the
source of the emissions to be determined.

56
Q

For pregnancy we use

A

Us

Radio (3 decks)

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