MRS1.1.5.0 Flashcards
(26 cards)
What is the bone anatomy of the chest
both anteriorly and posteriorly
Anterior: Clavicles; Sternum & Sternocostal articulations
Posterior: 12 thoracic vertebrae;12 paired ribs & Scapulae
Recall the visceral anatomy of chest
Airway
Lungs
Mediastinum:
* Heart
* Great vessels
Diaphragm
Why is cardiothoracic ratio important?
The cardiothoracic ratio (CTR) is the ratio of maximal horizontal cardiac diameter to maximal horizontal thoracic diameter
What are the important devices used in imaging
Table bucky, and erect bucky
Why are scatter removal grids important to radiographic imaging
The antiscatter grid plays an important role for enhancing image quality in projection radiography by transmitting a majority of primary radiation and selectively rejecting scattered radiation.
State the general rules for antiscatter grids
Exposure must be increased if using grid (usually at least doubling mAs)
* Do not angle against grid lines
* Do not place detector back to front in holder
* Do not place grid on back to front
* Use at a certain FFD
Why is FFD important?
Focal-film distance (FFD) is the the distance between the center of the anode of the x-ray tube (the focal spot) and the film (top of cassette). Also known as, Source-image distance (SID) which this measurement effects magnification, distortion, and x-ray beam intensity.
How does AUTOMATIC EXPOSURE CONTROL
(AEC) work?
Ionisation chamber is a hollow cell containing air
connected to a timer circuit
* Radiation hits the chamber, and the air inside
becomes ionised, creating an electrical charge
* The electrical charge travels along the wire to the
timer circuit and terminates the radiation exposure
when a sufficient charge has been received
* “Sufficient charge” is a predetermined value that
helps keep the dose as low as possible to see
anatomical detail of the lung
- The radiographer chooses the AEC chambers that
they would like to use- this is determined by the
anatomy in question
What does (AEC) mean?
AUTOMATIC EXPOSURE CONTROL
For PA,
109kV & 2 dots on the first row
For lateral,
125kV & middle dot
State the procedure for patient prep
- ID & Consent
- Explanation
- Pregnancy
- Remove clothing &
jewellery - Patient gown
State the criteria for a good radiographic image
- Sharp outlines of heart and diaphragm
- Faint shadows of the ribs and superior thoracic
vertebrae visible through the heart shadow - Lung markings visible from the hilum to the
periphery of the lung - Inspiration
- Proper shoulder rotation demonstrated by scapulae
projected outside the lung fields
State artefacts on the patient
On the patient
* Clothing
* Jewelry/money/phone etc.
* Dirt/food/hair/blood etc.
State artefacts inside the patient
- Medical devices
- Penetrating trauma
- Inhaled/swallowed FB
State examples of systemic error
- Grid lines
- Dead pixels
- AEC chambers
- Scatter
State the exposure error
- Saturation/burn (over exposure)
- Noise/quantum mottle (under exposure)
State the points for criteria
- Anatomy
- Collimation & Centring
- Positioning
- Exposure
What do we have to ensure for collimation?
- Superior collimation including apex of lung and surrounding soft tissue/ribs.
- Inferior collimation distal to the costophrenic angles.
- Lateral collimation close to skin edge.
- Centered midsagittal plane.
For positioning in the criteria of an image,
- Apical lung visible above clavicles.
- Scapulae projected clear of the lung fields.
- No rotation
o Trachea is midline
o Medial ends of the clavicles are equidistant
from the spinous processes - Good inspiratory effort (8-10 posterior ribs above the diaphragm).
What is kyphosis?
An increased front-to-back curve of the spine is called kyphosis. Kyphosis is an excessive forward rounding of the upper back. In older people, kyphosis is often due to weakness in the spinal bones that causes them to compress or crack.
What are the criteria for lateral x-ray
M: Correct post processed anatomical
marker clear of anatomy.
A: Both lungs from apices to bases
included. Soft tissues included
surrounding lung fields as appropriate.
C: Inferior collimation distal to the
diaphragm. Forward bending of the patient
(or tilting of the light beam diaphragm)
would allow collimation to parallel the
anterior and posterior thoracic margins
For lateral image of chest, the positioning should be
- Chin is not superimposing lungs
- Ribs posterior to the vertebral column
are superimposed. - Sternum is seen in profile
- Arms raised to demonstrate both lungs
free from soft tissue superimposition. - Superimposition of the posterior
costophrenic recess - Clear outline of diaphragm
For lateral image, the exposure should be
Contrast and density sufficient to visualise bone and soft tissue whilst able to appreciate lung markings
The ribs and thoracic cage are seen only faintly over the heart
