Physics UNIT 3: modalities that use X-rays

why is the tube head angled in a digital mammography unit

to maximise the anode heel effect, the cathode is placed over the thicker chest wall and the anode is placed over the nipple region to achieve uniform image density

what is the anode heel effect

the anode heel effect is the variation of intensity of the X-ray beam, the intensity is higher on the cathode side and lower on the anode side due to the absorption of x-rays in the anode

4 benefits of using a perspex compression plate

1. perspex is low density which means less scatter

2. it is radiolucent and transparent

3. reduces motion blur by holding the breast in place

4. compresses the breast making the thickness more even

what is the fixed FDD in mammography

65cm

role of the Automatic Exposure Control (AEC) in a digital mammography unit

selects and maintains optimal exposure factors regardless of the density or thickness of the breast tissue

gantry ct?

a box like structure which houses the key components; xray tube, collimator, detector array, filters, and high voltage generator

x-ray couch ct ?

usually made of carbon fibre, prior to the examination the height and longitudinal movement of the table is adjusted for centring. Must be smooth and unnaffected by the weight of the patient

laser beam lights ct?

used for precise patient positioning in x,y and z planes

x-ray tube ct

rotates 360 degrees around the patient using slip ring technology to provide a continuous x-ray beam for image acquisition

filters ct

remove low energy photons that do not contribute to image formation, lowering patient dose and improving beam quality

collimators ct?

Limit the x-ray beam to reduce patient dose and improve image quality

There are 2 types of collimators; pre-patient collimators reduce dose by limiting the area being exposed and pre-detector collimators reduce scatter and improve contrast